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nc-exe
Unverified Commit fa87aa42 authored by int0x33's avatar int0x33 Committed by GitHub
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Makefile 0 → 100644
View file @ fa87aa42
CC=i686-pc-mingw32-gcc
#CC=x86_64-pc-mingw32-gcc
CFLAGS=-DNDEBUG -DWIN32 -D_CONSOLE -DTELNET -DGAPING_SECURITY_HOLE
LDFLAGS=-s -lkernel32 -luser32 -lwsock32 -lwinmm
all: nc.exe
nc.exe: getopt.c doexec.c netcat.c
$(CC) $(CFLAGS) getopt.c doexec.c netcat.c $(LDFLAGS) -o nc.exe
clean:
rm nc.exe
doexec.c 0 → 100644
View file @ fa87aa42
// for license see license.txt
// Modified 12/27/2004 by Chris Wysopal <weld@vulnwatch.com>
// fixed vulnerability found by hat-squad
// portions Copyright (C) 1994 Nathaniel W. Mishkin
// code taken from rlogind.exe
#include <stdlib.h>
#include <winsock2.h>
#include <winbase.h>
#ifdef GAPING_SECURITY_HOLE
#define BUFFER_SIZE 200
extern char * pr00gie;
void holler(char * str, char * p1, char * p2, char * p3, char * p4, char * p5, char * p6);
char smbuff[20];
//
// Structure used to describe each session
//
typedef struct {
//
// These fields are filled in at session creation time
//
HANDLE ReadPipeHandle; // Handle to shell stdout pipe
HANDLE WritePipeHandle; // Handle to shell stdin pipe
HANDLE ProcessHandle; // Handle to shell process
//
//
// These fields are filled in at session connect time and are only
// valid when the session is connected
//
SOCKET ClientSocket;
HANDLE ReadShellThreadHandle; // Handle to session shell-read thread
HANDLE WriteShellThreadHandle; // Handle to session shell-read thread
} SESSION_DATA, *PSESSION_DATA;
//
// Private prototypes
//
static HANDLE
StartShell(
HANDLE StdinPipeHandle,
HANDLE StdoutPipeHandle
);
static VOID
SessionReadShellThreadFn(
LPVOID Parameter
);
static VOID
SessionWriteShellThreadFn(
LPVOID Parameter
);
// **********************************************************************
//
// CreateSession
//
// Creates a new session. Involves creating the shell process and establishing
// pipes for communication with it.
//
// Returns a handle to the session or NULL on failure.
//
static PSESSION_DATA
CreateSession(
VOID
)
{
PSESSION_DATA Session = NULL;
BOOL Result;
SECURITY_ATTRIBUTES SecurityAttributes;
HANDLE ShellStdinPipe = NULL;
HANDLE ShellStdoutPipe = NULL;
//
// Allocate space for the session data
//
Session = (PSESSION_DATA) malloc(sizeof(SESSION_DATA));
if (Session == NULL) {
return(NULL);
}
//
// Reset fields in preparation for failure
//
Session->ReadPipeHandle = NULL;
Session->WritePipeHandle = NULL;
//
// Create the I/O pipes for the shell
//
SecurityAttributes.nLength = sizeof(SecurityAttributes);
SecurityAttributes.lpSecurityDescriptor = NULL; // Use default ACL
SecurityAttributes.bInheritHandle = TRUE; // Shell will inherit handles
Result = CreatePipe(&Session->ReadPipeHandle, &ShellStdoutPipe,
&SecurityAttributes, 0);
if (!Result) {
holler("Failed to create shell stdout pipe, error = %s",
itoa(GetLastError(), smbuff, 10), NULL, NULL, NULL, NULL, NULL);
goto Failure;
}
Result = CreatePipe(&ShellStdinPipe, &Session->WritePipeHandle,
&SecurityAttributes, 0);
if (!Result) {
holler("Failed to create shell stdin pipe, error = %s",
itoa(GetLastError(), smbuff, 10), NULL, NULL, NULL, NULL, NULL);
goto Failure;
}
//
// Start the shell
//
Session->ProcessHandle = StartShell(ShellStdinPipe, ShellStdoutPipe);
//
// We're finished with our copy of the shell pipe handles
// Closing the runtime handles will close the pipe handles for us.
//
CloseHandle(ShellStdinPipe);
CloseHandle(ShellStdoutPipe);
//
// Check result of shell start
//
if (Session->ProcessHandle == NULL) {
holler("Failed to execute shell", NULL,
NULL, NULL, NULL, NULL, NULL);
goto Failure;
}
//
// The session is not connected, initialize variables to indicate that
//
Session->ClientSocket = INVALID_SOCKET;
//
// Success, return the session pointer as a handle
//
return(Session);
Failure:
//
// We get here for any failure case.
// Free up any resources and exit
//
if (ShellStdinPipe != NULL)
CloseHandle(ShellStdinPipe);
if (ShellStdoutPipe != NULL)
CloseHandle(ShellStdoutPipe);
if (Session->ReadPipeHandle != NULL)
CloseHandle(Session->ReadPipeHandle);
if (Session->WritePipeHandle != NULL)
CloseHandle(Session->WritePipeHandle);
free(Session);
return(NULL);
}
BOOL
doexec(
SOCKET ClientSocket
)
{
PSESSION_DATA Session = CreateSession();
SECURITY_ATTRIBUTES SecurityAttributes;
DWORD ThreadId;
HANDLE HandleArray[3];
int i;
SecurityAttributes.nLength = sizeof(SecurityAttributes);
SecurityAttributes.lpSecurityDescriptor = NULL; // Use default ACL
SecurityAttributes.bInheritHandle = FALSE; // No inheritance
//
// Store the client socket handle in the session structure so the thread
// can get at it. This also signals that the session is connected.
//
Session->ClientSocket = ClientSocket;
//
// Create the session threads
//
Session->ReadShellThreadHandle =
CreateThread(&SecurityAttributes, 0,
(LPTHREAD_START_ROUTINE) SessionReadShellThreadFn,
(LPVOID) Session, 0, &ThreadId);
if (Session->ReadShellThreadHandle == NULL) {
holler("Failed to create ReadShell session thread, error = %s",
itoa(GetLastError(), smbuff, 10), NULL, NULL, NULL, NULL, NULL);
//
// Reset the client pipe handle to indicate this session is disconnected
//
Session->ClientSocket = INVALID_SOCKET;
return(FALSE);
}
Session->WriteShellThreadHandle =
CreateThread(&SecurityAttributes, 0,
(LPTHREAD_START_ROUTINE) SessionWriteShellThreadFn,
(LPVOID) Session, 0, &ThreadId);
if (Session->WriteShellThreadHandle == NULL) {
holler("Failed to create ReadShell session thread, error = %s",
itoa(GetLastError(), smbuff, 10), NULL, NULL, NULL, NULL, NULL);
//
// Reset the client pipe handle to indicate this session is disconnected
//
Session->ClientSocket = INVALID_SOCKET;
TerminateThread(Session->WriteShellThreadHandle, 0);
return(FALSE);
}
//
// Wait for either thread or the shell process to finish
//
HandleArray[0] = Session->ReadShellThreadHandle;
HandleArray[1] = Session->WriteShellThreadHandle;
HandleArray[2] = Session->ProcessHandle;
i = WaitForMultipleObjects(3, HandleArray, FALSE, 0xffffffff);
switch (i) {
case WAIT_OBJECT_0 + 0:
TerminateThread(Session->WriteShellThreadHandle, 0);
TerminateProcess(Session->ProcessHandle, 1);
break;
case WAIT_OBJECT_0 + 1:
TerminateThread(Session->ReadShellThreadHandle, 0);
TerminateProcess(Session->ProcessHandle, 1);
break;
case WAIT_OBJECT_0 + 2:
TerminateThread(Session->WriteShellThreadHandle, 0);
TerminateThread(Session->ReadShellThreadHandle, 0);
break;
default:
holler("WaitForMultipleObjects error: %s",
itoa(GetLastError(), smbuff, 10), NULL, NULL, NULL, NULL, NULL);
break;
}
// Close my handles to the threads, the shell process, and the shell pipes
shutdown(Session->ClientSocket, SD_BOTH);
closesocket(Session->ClientSocket);
DisconnectNamedPipe(Session->ReadPipeHandle);
CloseHandle(Session->ReadPipeHandle);
DisconnectNamedPipe(Session->WritePipeHandle);
CloseHandle(Session->WritePipeHandle);
CloseHandle(Session->ReadShellThreadHandle);
CloseHandle(Session->WriteShellThreadHandle);
CloseHandle(Session->ProcessHandle);
free(Session);
return(TRUE);
}
// **********************************************************************
//
// StartShell
//
// Execs the shell with the specified handle as stdin, stdout/err
//
// Returns process handle or NULL on failure
//
static HANDLE
StartShell(
HANDLE ShellStdinPipeHandle,
HANDLE ShellStdoutPipeHandle
)
{
PROCESS_INFORMATION ProcessInformation;
STARTUPINFO si;
HANDLE ProcessHandle = NULL;
//
// Initialize process startup info
//
si.cb = sizeof(STARTUPINFO);
si.lpReserved = NULL;
si.lpTitle = NULL;
si.lpDesktop = NULL;
si.dwX = si.dwY = si.dwXSize = si.dwYSize = 0L;
si.wShowWindow = SW_HIDE;
si.lpReserved2 = NULL;
si.cbReserved2 = 0;
si.dwFlags = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
si.hStdInput = ShellStdinPipeHandle;
si.hStdOutput = ShellStdoutPipeHandle;
DuplicateHandle(GetCurrentProcess(), ShellStdoutPipeHandle,
GetCurrentProcess(), &si.hStdError,
DUPLICATE_SAME_ACCESS, TRUE, 0);
if (CreateProcess(NULL, pr00gie, NULL, NULL, TRUE, 0, NULL, NULL,
&si, &ProcessInformation))
{
ProcessHandle = ProcessInformation.hProcess;
CloseHandle(ProcessInformation.hThread);
}
else
holler("Failed to execute shell, error = %s",
itoa(GetLastError(), smbuff, 10), NULL, NULL, NULL, NULL, NULL);
return(ProcessHandle);
}
// **********************************************************************
// SessionReadShellThreadFn
//
// The read thread procedure. Reads from the pipe connected to the shell
// process, writes to the socket.
//
static VOID
SessionReadShellThreadFn(
LPVOID Parameter
)
{
PSESSION_DATA Session = Parameter;
BYTE Buffer[BUFFER_SIZE];
BYTE Buffer2[BUFFER_SIZE*2+30];
DWORD BytesRead;
// this bogus peek is here because win32 won't let me close the pipe if it is
// in waiting for input on a read.
while (PeekNamedPipe(Session->ReadPipeHandle, Buffer, sizeof(Buffer),
&BytesRead, NULL, NULL))
{
DWORD BufferCnt, BytesToWrite;
BYTE PrevChar = 0;
if (BytesRead > 0)
{
ReadFile(Session->ReadPipeHandle, Buffer, sizeof(Buffer),
&BytesRead, NULL);
}
else
{
Sleep(50);
continue;
}
//
// Process the data we got from the shell: replace any naked LF's
// with CR-LF pairs.
//
for (BufferCnt = 0, BytesToWrite = 0; BufferCnt < BytesRead; BufferCnt++) {
if (Buffer[BufferCnt] == '\n' && PrevChar != '\r')
Buffer2[BytesToWrite++] = '\r';
PrevChar = Buffer2[BytesToWrite++] = Buffer[BufferCnt];
}
if (send(Session->ClientSocket, Buffer2, BytesToWrite, 0) <= 0)
break;
}
if (GetLastError() != ERROR_BROKEN_PIPE)
holler("SessionReadShellThreadFn exitted, error = %s",
itoa(GetLastError(), smbuff, 10), NULL, NULL, NULL, NULL, NULL);
ExitThread(0);
}
// **********************************************************************
// SessionWriteShellThreadFn
//
// The write thread procedure. Reads from socket, writes to pipe connected
// to shell process.
static VOID
SessionWriteShellThreadFn(
LPVOID Parameter
)
{
PSESSION_DATA Session = Parameter;
BYTE RecvBuffer[1];
BYTE Buffer[BUFFER_SIZE];
DWORD BytesWritten;
DWORD BufferCnt;
BufferCnt = 0;
//
// Loop, reading one byte at a time from the socket.
//
while (recv(Session->ClientSocket, RecvBuffer, sizeof(RecvBuffer), 0) != 0) {
Buffer[BufferCnt++] = RecvBuffer[0];
if (RecvBuffer[0] == '\r')
Buffer[BufferCnt++] = '\n';
// Trap exit as it causes problems
if (strnicmp(Buffer, "exit\r\n", 6) == 0)
ExitThread(0);
//
// If we got a CR, it's time to send what we've buffered up down to the
// shell process.
// SECURITY FIX: CW 12/27/04 Add BufferCnt size check. If we hit end of buffer, flush it
if (RecvBuffer[0] == '\n' || RecvBuffer[0] == '\r' || BufferCnt > BUFFER_SIZE-1) {
if (! WriteFile(Session->WritePipeHandle, Buffer, BufferCnt,
&BytesWritten, NULL))
{
break;
}
BufferCnt = 0;
}
}
ExitThread(0);
}
#endif
\ No newline at end of file
generic.h 0 → 100644
View file @ fa87aa42
/* generic.h -- anything you don't #undef at the end remains in effect.
The ONLY things that go in here are generic indicator flags; it's up
to your programs to declare and call things based on those flags.
You should only need to make changes via a minimal system-specific section
at the end of this file. To build a new section, rip through this and
check everything it mentions on your platform, and #undef that which needs
it. If you generate a system-specific section you didn't find in here,
please mail me a copy so I can update the "master".
I realize I'm probably inventing another pseudo-standard here, but
goddamnit, everybody ELSE has already, and I can't include all of their
hairball schemes too. HAVE_xx conforms to the gnu/autoconf usage and
seems to be the most common format. In fact, I dug a lot of these out
of autoconf and tried to common them all together using "stupidh" to
collect data from platforms.
In disgust... _H* 940910, 941115. Pseudo-version: 1.1 */
#ifndef GENERIC_H /* only run through this once */
#define GENERIC_H
/* =============================== */
/* System calls, lib routines, etc */
/* =============================== */
/* How does your system declare malloc, void or char? Usually void, but go
ask the SunOS people why they had to be different... */
#define VOID_MALLOC
/* notably from fwtk/firewall.h: posix locking? */
#define HAVE_FLOCK /* otherwise it's lockf() */
/* if you don't have setsid(), you might have setpgrp().
#define HAVE_SETSID
/* random() is generally considered better than rand() */
/* xxx: rand48? */
#define HAVE_RANDOM
/* if your machine doesn't have lstat(), it should have stat() [dos...] */
#define HAVE_LSTAT
/* different kinds of term ioctls. How to recognize them, very roughly:
sysv/POSIX_ME_HARDER: termio[s].h, struct termio[s], tty.c_*[]
bsd/old stuff: sgtty.h, ioctl(TIOCSETP), sgttyb.sg_*, tchars.t_*
#define HAVE_TERMIOS
/* dbm vs ndbm */
#define HAVE_NDBM
/* extended utmp/wtmp stuff. MOST machines still do NOT have this SV-ism */
#define UTMPX
/* some systems have nice() which takes *relative* values... [resource.h] */
#define HAVE_SETPRIORITY
/* a sysvism, I think, but ... */
#define HAVE_SYSINFO
/* punted for now: setown / siocspgrp ... see firewall.h */
/* ============= */
/* Include files */
/* ============= */
/* Presence of these can be determined via a script that sniffs them
out if you aren't sure. */
/* stdlib comes with most modern compilers, but ya never know */
#define HAVE_STDLIB_H
/* not on a DOS box! */
#define HAVE_UNISTD_H
/* stdarg is a weird one */
#define HAVE_STDARG_H
/* dir.h or maybe ndir.h otherwise. */
#define HAVE_DIRENT_H
/* string or strings */
#define HAVE_STRINGS_H
/* if you don't have lastlog.h, what you want might be in login.h */
#define HAVE_LASTLOG_H
/* predefines for _PATH_various */
#define HAVE_PATHS_H
/* assorted others */
#define HAVE_PARAM_H
#define HAVE_SYSMACROS_H /* in sys/! */
#define HAVE_TTYENT_H /* securetty et al */
/* ==================== */
/* Still maybe have to do something about the following, if it's even
worth it. I just grepped a lot of these out of various code, without
looking them up yet:
#define HAVE_EINPROGRESS
#define HAVE_F_SETOWN
#define HAVE_SETENV ... now *there's* a hairy one; **environ is portable
#define BIG_ENDIAN/little_endian ... *please* try to avoid this stupidity
#define HAVE_GETUSERSHELL ... you could always pull it out of getpwent()
#define HAVE_SETE[UG]ID ... lib or syscall, it varies on diff platforms
#define HAVE_STRCHR ... should actually be handled by string/strings
#define HAVE_PSTAT
#define HAVE_ST_BLKSIZE ... a stat() thing?
#define HAVE_IP_TOS
#define HAVE_STRFTIME ... screw this, we should just INCLUDE one for lame
old boxes that don't have it [sunos 3.x, early 4.x?]
#define HAVE_VFPRINTF
#define HAVE_SHADOW_PASSWD ... in its multitudinous schemes?? ... how
about sumpin' like #define SHADOW_PASSWD_TYPE ... could get grody.
#define SIG* ... what a swamp, punt for now; should all be in signal.h
#define HAVE_STRCSPN ... see larry wall's comment in the fwtk regex code
#define ULTRIX_AUTH ... bwahaha.
#define HAVE_YP or NIS or whatever you wanna call it this week
randomness about VARARGS??
There's also the issue about WHERE various .h files live, sys/ or otherwise.
There's a BIG swamp lurking where network code of any sort lives.
*/
/* ======================== */
/* System-specific sections */
/* ======================== */
/* By turning OFF various bits of the above, you can customize for
a given platform. /*
/* DOS boxes, with MSC; you may need to adapt to a different compiler. */
#ifdef MSDOS
#undef HAVE_FLOCK
#undef HAVE_RANDOM
#undef HAVE_LSTAT
#undef HAVE_TERMIOS
#undef UTMPX
#undef HAVE_SYSINFO
#undef HAVE_UNISTD_H
#undef HAVE_DIRENT_H /* unless you have the k00l little wrapper from L5!! */
#undef HAVE_STRINGS_H
#undef HAVE_LASTLOG_H
#undef HAVE_PATHS_H
#undef HAVE_PARAM_H
#undef HAVE_SYSMACROS_H
#undef HAVE_TTYENT_H
#endif /* MSDOS */
/* buglix 4.x; dunno about 3.x on down. should be bsd4.2. */
#ifdef ULTRIX
#undef UTMPX
#undef HAVE_PATHS_H
#undef HAVE_SYSMACROS_H
#endif /* buglix */
/* some of this might still be broken on older sunoses */
#ifdef SUNOS
#undef VOID_MALLOC
#undef UTMPX
#undef HAVE_PATHS_H
#endif /* sunos */
/* "contact your vendor for a fix" */
#ifdef SOLARIS
/* has UTMPX */
#undef HAVE_SETPRIORITY
#undef HAVE_STRINGS_H /* this is genuinely the case, go figure */
#undef HAVE_PATHS_H
#undef HAVE_TTYENT_H
#endif /* SOLARIS */
/* whatever aix variant MIT had at the time */
#ifdef AIX
#undef UTMPX
#undef HAVE_LASTLOG_H
#define HAVE_LOGIN_H /* "special", in the educational sense */
#endif /* aix */
/* linux, which is trying as desperately as the gnu folks can to be
POSIXLY_CORRECT. I think I'm gonna hurl... */
#ifdef LINUX
#undef UTMPX
#undef HAVE_SYSINFO
#undef HAVE_TTYENT_H
#endif /* linux */
/* irix 5.x; may not be correct for earlier ones */
#ifdef IRIX
/* wow, does irix really have everything?! */
#endif /* irix */
/* osf on alphas */
#ifdef OSF
#undef UTMPX
#endif /* osf */
/* they's some FUCKED UP paths in this one! */
#ifdef FREEBSD
#undef UTMPX
#undef HAVE_SYSINFO
#undef HAVE_LASTLOG_H
#undef HAVE_SYSMACROS_H
#endif /* freebsd */
/* From the sidewinder site, of all places; may be unreliable */
#ifdef BSDI
#undef UTMPX
#undef HAVE_LASTLOG_H
#undef HAVE_SYSMACROS_H
#undef HAVE_TTYENT_H
/* and their malloc.h was in sys/ ?! */
#endif /* bsdi */
/* netbsd/44lite, jives with amiga-netbsd from cactus */
#ifdef NETBSD
#undef UTMPX
#undef HAVE_SYSINFO
#undef HAVE_LASTLOG_H
#endif /* netbsd */
/* Make some "generic" assumptions if all else fails */
#ifdef GENERIC
#undef HAVE_FLOCK
#if defined(SYSV) && (SYSV < 4) /* TW leftover: old SV doesnt have symlinks */
#undef HAVE_LSTAT
#endif /* old SYSV */
#undef HAVE_TERMIOS
#undef UTMPX
#undef HAVE_PATHS_H
#endif /* generic */
/* ================ */
#endif /* GENERIC_H */
getopt.c 0 → 100644
View file @ fa87aa42
/* Getopt for GNU.
NOTE: getopt is now part of the C library, so if you don't know what
"Keep this file name-space clean" means, talk to roland@gnu.ai.mit.edu
before changing it!
Copyright (C) 1987, 88, 89, 90, 91, 92, 93, 94
Free Software Foundation, Inc.
This file is part of the GNU C Library. Its master source is NOT part of
the C library, however. The master source lives in /gd/gnu/lib.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
/* This tells Alpha OSF/1 not to define a getopt prototype in <stdio.h>.
Ditto for AIX 3.2 and <stdlib.h>. */
#ifndef _NO_PROTO
#define _NO_PROTO
#endif
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#if !defined (__STDC__) || !__STDC__
/* This is a separate conditional since some stdc systems
reject `defined (const)'. */
#ifndef const
#define const
#endif
#endif
#include <stdio.h>
#ifdef WIN32
#include <string.h>
#endif
/* Comment out all this code if we are using the GNU C Library, and are not
actually compiling the library itself. This code is part of the GNU C
Library, but also included in many other GNU distributions. Compiling
and linking in this code is a waste when using the GNU C library
(especially if it is a shared library). Rather than having every GNU
program understand `configure --with-gnu-libc' and omit the object files,
it is simpler to just do this in the source for each such file. */
#if defined (_LIBC) || !defined (__GNU_LIBRARY__)
/* This needs to come after some library #include
to get __GNU_LIBRARY__ defined. */
#ifdef __GNU_LIBRARY__
/* Don't include stdlib.h for non-GNU C libraries because some of them
contain conflicting prototypes for getopt. */
#include <stdlib.h>
#endif /* GNU C library. */
/* This version of `getopt' appears to the caller like standard Unix `getopt'
but it behaves differently for the user, since it allows the user
to intersperse the options with the other arguments.
As `getopt' works, it permutes the elements of ARGV so that,
when it is done, all the options precede everything else. Thus
all application programs are extended to handle flexible argument order.
Setting the environment variable POSIXLY_CORRECT disables permutation.
Then the behavior is completely standard.
GNU application programs can use a third alternative mode in which
they can distinguish the relative order of options and other arguments. */
#include "getopt.h"
/* For communication from `getopt' to the caller.
When `getopt' finds an option that takes an argument,
the argument value is returned here.
Also, when `ordering' is RETURN_IN_ORDER,
each non-option ARGV-element is returned here. */
char *optarg = NULL;
/* Index in ARGV of the next element to be scanned.
This is used for communication to and from the caller
and for communication between successive calls to `getopt'.
On entry to `getopt', zero means this is the first call; initialize.
When `getopt' returns EOF, this is the index of the first of the
non-option elements that the caller should itself scan.
Otherwise, `optind' communicates from one call to the next
how much of ARGV has been scanned so far. */
/* XXX 1003.2 says this must be 1 before any call. */
int optind = 0;
/* The next char to be scanned in the option-element
in which the last option character we returned was found.
This allows us to pick up the scan where we left off.
If this is zero, or a null string, it means resume the scan
by advancing to the next ARGV-element. */
static char *nextchar;
/* Callers store zero here to inhibit the error message
for unrecognized options. */
int opterr = 1;
/* Set to an option character which was unrecognized.
This must be initialized on some systems to avoid linking in the
system's own getopt implementation. */
int optopt = '?';
/* Describe how to deal with options that follow non-option ARGV-elements.
If the caller did not specify anything,
the default is REQUIRE_ORDER if the environment variable
POSIXLY_CORRECT is defined, PERMUTE otherwise.
REQUIRE_ORDER means don't recognize them as options;
stop option processing when the first non-option is seen.
This is what Unix does.
This mode of operation is selected by either setting the environment
variable POSIXLY_CORRECT, or using `+' as the first character
of the list of option characters.
PERMUTE is the default. We permute the contents of ARGV as we scan,
so that eventually all the non-options are at the end. This allows options
to be given in any order, even with programs that were not written to
expect this.
RETURN_IN_ORDER is an option available to programs that were written
to expect options and other ARGV-elements in any order and that care about
the ordering of the two. We describe each non-option ARGV-element
as if it were the argument of an option with character code 1.
Using `-' as the first character of the list of option characters
selects this mode of operation.
The special argument `--' forces an end of option-scanning regardless
of the value of `ordering'. In the case of RETURN_IN_ORDER, only
`--' can cause `getopt' to return EOF with `optind' != ARGC. */
static enum
{
REQUIRE_ORDER, PERMUTE, RETURN_IN_ORDER
} ordering;
/* Value of POSIXLY_CORRECT environment variable. */
static char *posixly_correct;
#ifdef __GNU_LIBRARY__
/* We want to avoid inclusion of string.h with non-GNU libraries
because there are many ways it can cause trouble.
On some systems, it contains special magic macros that don't work
in GCC. */
#include <string.h>
#define my_index strchr
#else
/* Avoid depending on library functions or files
whose names are inconsistent. */
char *getenv ();
static char *
my_index (str, chr)
const char *str;
int chr;
{
while (*str)
{
if (*str == chr)
return (char *) str;
str++;
}
return 0;
}
/* If using GCC, we can safely declare strlen this way.
If not using GCC, it is ok not to declare it. */
#ifdef __GNUC__
/* Note that Motorola Delta 68k R3V7 comes with GCC but not stddef.h.
That was relevant to code that was here before. */
#if !defined (__STDC__) || !__STDC__
/* gcc with -traditional declares the built-in strlen to return int,
and has done so at least since version 2.4.5. -- rms. */
extern int strlen (const char *);
#endif /* not __STDC__ */
#endif /* __GNUC__ */
#endif /* not __GNU_LIBRARY__ */
/* Handle permutation of arguments. */
/* Describe the part of ARGV that contains non-options that have
been skipped. `first_nonopt' is the index in ARGV of the first of them;
`last_nonopt' is the index after the last of them. */
static int first_nonopt;
static int last_nonopt;
/* Exchange two adjacent subsequences of ARGV.
One subsequence is elements [first_nonopt,last_nonopt)
which contains all the non-options that have been skipped so far.
The other is elements [last_nonopt,optind), which contains all
the options processed since those non-options were skipped.
`first_nonopt' and `last_nonopt' are relocated so that they describe
the new indices of the non-options in ARGV after they are moved. */
static void
exchange (argv)
char **argv;
{
int bottom = first_nonopt;
int middle = last_nonopt;
int top = optind;
char *tem;
/* Exchange the shorter segment with the far end of the longer segment.
That puts the shorter segment into the right place.
It leaves the longer segment in the right place overall,
but it consists of two parts that need to be swapped next. */
while (top > middle && middle > bottom)
{
if (top - middle > middle - bottom)
{
/* Bottom segment is the short one. */
int len = middle - bottom;
register int i;
/* Swap it with the top part of the top segment. */
for (i = 0; i < len; i++)
{
tem = argv[bottom + i];
argv[bottom + i] = argv[top - (middle - bottom) + i];
argv[top - (middle - bottom) + i] = tem;
}
/* Exclude the moved bottom segment from further swapping. */
top -= len;
}
else
{
/* Top segment is the short one. */
int len = top - middle;
register int i;
/* Swap it with the bottom part of the bottom segment. */
for (i = 0; i < len; i++)
{
tem = argv[bottom + i];
argv[bottom + i] = argv[middle + i];
argv[middle + i] = tem;
}
/* Exclude the moved top segment from further swapping. */
bottom += len;
}
}
/* Update records for the slots the non-options now occupy. */
first_nonopt += (optind - last_nonopt);
last_nonopt = optind;
}
/* Initialize the internal data when the first call is made. */
static const char *
_getopt_initialize (optstring)
const char *optstring;
{
/* Start processing options with ARGV-element 1 (since ARGV-element 0
is the program name); the sequence of previously skipped
non-option ARGV-elements is empty. */
first_nonopt = last_nonopt = optind = 1;
nextchar = NULL;
posixly_correct = getenv ("POSIXLY_CORRECT");
/* Determine how to handle the ordering of options and nonoptions. */
if (optstring[0] == '-')
{
ordering = RETURN_IN_ORDER;
++optstring;
}
else if (optstring[0] == '+')
{
ordering = REQUIRE_ORDER;
++optstring;
}
else if (posixly_correct != NULL)
ordering = REQUIRE_ORDER;
else
ordering = PERMUTE;
return optstring;
}
/* Scan elements of ARGV (whose length is ARGC) for option characters
given in OPTSTRING.
If an element of ARGV starts with '-', and is not exactly "-" or "--",
then it is an option element. The characters of this element
(aside from the initial '-') are option characters. If `getopt'
is called repeatedly, it returns successively each of the option characters
from each of the option elements.
If `getopt' finds another option character, it returns that character,
updating `optind' and `nextchar' so that the next call to `getopt' can
resume the scan with the following option character or ARGV-element.
If there are no more option characters, `getopt' returns `EOF'.
Then `optind' is the index in ARGV of the first ARGV-element
that is not an option. (The ARGV-elements have been permuted
so that those that are not options now come last.)
OPTSTRING is a string containing the legitimate option characters.
If an option character is seen that is not listed in OPTSTRING,
return '?' after printing an error message. If you set `opterr' to
zero, the error message is suppressed but we still return '?'.
If a char in OPTSTRING is followed by a colon, that means it wants an arg,
so the following text in the same ARGV-element, or the text of the following
ARGV-element, is returned in `optarg'. Two colons mean an option that
wants an optional arg; if there is text in the current ARGV-element,
it is returned in `optarg', otherwise `optarg' is set to zero.
If OPTSTRING starts with `-' or `+', it requests different methods of
handling the non-option ARGV-elements.
See the comments about RETURN_IN_ORDER and REQUIRE_ORDER, above.
Long-named options begin with `--' instead of `-'.
Their names may be abbreviated as long as the abbreviation is unique
or is an exact match for some defined option. If they have an
argument, it follows the option name in the same ARGV-element, separated
from the option name by a `=', or else the in next ARGV-element.
When `getopt' finds a long-named option, it returns 0 if that option's
`flag' field is nonzero, the value of the option's `val' field
if the `flag' field is zero.
The elements of ARGV aren't really const, because we permute them.
But we pretend they're const in the prototype to be compatible
with other systems.
LONGOPTS is a vector of `struct option' terminated by an
element containing a name which is zero.
LONGIND returns the index in LONGOPT of the long-named option found.
It is only valid when a long-named option has been found by the most
recent call.
If LONG_ONLY is nonzero, '-' as well as '--' can introduce
long-named options. */
int
_getopt_internal (argc, argv, optstring, longopts, longind, long_only)
int argc;
char *const *argv;
const char *optstring;
const struct option *longopts;
int *longind;
int long_only;
{
optarg = NULL;
if (optind == 0)
optstring = _getopt_initialize (optstring);
if (nextchar == NULL || *nextchar == '\0')
{
/* Advance to the next ARGV-element. */
if (ordering == PERMUTE)
{
/* If we have just processed some options following some non-options,
exchange them so that the options come first. */
if (first_nonopt != last_nonopt && last_nonopt != optind)
exchange ((char **) argv);
else if (last_nonopt != optind)
first_nonopt = optind;
/* Skip any additional non-options
and extend the range of non-options previously skipped. */
while (optind < argc
&& (argv[optind][0] != '-' || argv[optind][1] == '\0'))
optind++;
last_nonopt = optind;
}
/* The special ARGV-element `--' means premature end of options.
Skip it like a null option,
then exchange with previous non-options as if it were an option,
then skip everything else like a non-option. */
if (optind != argc && !strcmp (argv[optind], "--"))
{
optind++;
if (first_nonopt != last_nonopt && last_nonopt != optind)
exchange ((char **) argv);
else if (first_nonopt == last_nonopt)
first_nonopt = optind;
last_nonopt = argc;
optind = argc;
}
/* If we have done all the ARGV-elements, stop the scan
and back over any non-options that we skipped and permuted. */
if (optind == argc)
{
/* Set the next-arg-index to point at the non-options
that we previously skipped, so the caller will digest them. */
if (first_nonopt != last_nonopt)
optind = first_nonopt;
return EOF;
}
/* If we have come to a non-option and did not permute it,
either stop the scan or describe it to the caller and pass it by. */
if ((argv[optind][0] != '-' || argv[optind][1] == '\0'))
{
if (ordering == REQUIRE_ORDER)
return EOF;
optarg = argv[optind++];
return 1;
}
/* We have found another option-ARGV-element.
Skip the initial punctuation. */
nextchar = (argv[optind] + 1
+ (longopts != NULL && argv[optind][1] == '-'));
}
/* Decode the current option-ARGV-element. */
/* Check whether the ARGV-element is a long option.
If long_only and the ARGV-element has the form "-f", where f is
a valid short option, don't consider it an abbreviated form of
a long option that starts with f. Otherwise there would be no
way to give the -f short option.
On the other hand, if there's a long option "fubar" and
the ARGV-element is "-fu", do consider that an abbreviation of
the long option, just like "--fu", and not "-f" with arg "u".
This distinction seems to be the most useful approach. */
if (longopts != NULL
&& (argv[optind][1] == '-'
|| (long_only && (argv[optind][2] || !my_index (optstring, argv[optind][1])))))
{
char *nameend;
const struct option *p;
const struct option *pfound = NULL;
int exact = 0;
int ambig = 0;
int indfound;
int option_index;
for (nameend = nextchar; *nameend && *nameend != '='; nameend++)
/* Do nothing. */ ;
/* Test all long options for either exact match
or abbreviated matches. */
for (p = longopts, option_index = 0; p->name; p++, option_index++)
if (!strncmp (p->name, nextchar, nameend - nextchar))
{
if ((unsigned int)(nameend - nextchar) == (unsigned int)strlen (p->name))
{
/* Exact match found. */
pfound = p;
indfound = option_index;
exact = 1;
break;
}
else if (pfound == NULL)
{
/* First nonexact match found. */
pfound = p;
indfound = option_index;
}
else
/* Second or later nonexact match found. */
ambig = 1;
}
if (ambig && !exact)
{
if (opterr)
fprintf (stderr, "%s: option `%s' is ambiguous\n",
argv[0], argv[optind]);
nextchar += strlen (nextchar);
optind++;
return '?';
}
if (pfound != NULL)
{
option_index = indfound;
optind++;
if (*nameend)
{
/* Don't test has_arg with >, because some C compilers don't
allow it to be used on enums. */
if (pfound->has_arg)
optarg = nameend + 1;
else
{
if (opterr)
{
if (argv[optind - 1][1] == '-')
/* --option */
fprintf (stderr,
"%s: option `--%s' doesn't allow an argument\n",
argv[0], pfound->name);
else
/* +option or -option */
fprintf (stderr,
"%s: option `%c%s' doesn't allow an argument\n",
argv[0], argv[optind - 1][0], pfound->name);
}
nextchar += strlen (nextchar);
return '?';
}
}
else if (pfound->has_arg == 1)
{
if (optind < argc)
optarg = argv[optind++];
else
{
if (opterr)
fprintf (stderr, "%s: option `%s' requires an argument\n",
argv[0], argv[optind - 1]);
nextchar += strlen (nextchar);
return optstring[0] == ':' ? ':' : '?';
}
}
nextchar += strlen (nextchar);
if (longind != NULL)
*longind = option_index;
if (pfound->flag)
{
*(pfound->flag) = pfound->val;
return 0;
}
return pfound->val;
}
/* Can't find it as a long option. If this is not getopt_long_only,
or the option starts with '--' or is not a valid short
option, then it's an error.
Otherwise interpret it as a short option. */
if (!long_only || argv[optind][1] == '-'
|| my_index (optstring, *nextchar) == NULL)
{
if (opterr)
{
if (argv[optind][1] == '-')
/* --option */
fprintf (stderr, "%s: unrecognized option `--%s'\n",
argv[0], nextchar);
else
/* +option or -option */
fprintf (stderr, "%s: unrecognized option `%c%s'\n",
argv[0], argv[optind][0], nextchar);
}
nextchar = (char *) "";
optind++;
return '?';
}
}
/* Look at and handle the next short option-character. */
{
char c = *nextchar++;
char *temp = my_index (optstring, c);
/* Increment `optind' when we start to process its last character. */
if (*nextchar == '\0')
++optind;
if (temp == NULL || c == ':')
{
if (opterr)
{
if (posixly_correct)
/* 1003.2 specifies the format of this message. */
fprintf (stderr, "%s: illegal option -- %c\n", argv[0], c);
else
fprintf (stderr, "%s: invalid option -- %c\n", argv[0], c);
}
optopt = c;
return '?';
}
if (temp[1] == ':')
{
if (temp[2] == ':')
{
/* This is an option that accepts an argument optionally. */
if (*nextchar != '\0')
{
optarg = nextchar;
optind++;
}
else
optarg = NULL;
nextchar = NULL;
}
else
{
/* This is an option that requires an argument. */
if (*nextchar != '\0')
{
optarg = nextchar;
/* If we end this ARGV-element by taking the rest as an arg,
we must advance to the next element now. */
optind++;
}
else if (optind == argc)
{
if (opterr)
{
/* 1003.2 specifies the format of this message. */
fprintf (stderr, "%s: option requires an argument -- %c\n",
argv[0], c);
}
optopt = c;
if (optstring[0] == ':')
c = ':';
else
c = '?';
}
else
/* We already incremented `optind' once;
increment it again when taking next ARGV-elt as argument. */
optarg = argv[optind++];
nextchar = NULL;
}
}
return c;
}
}
int
getopt (argc, argv, optstring)
int argc;
char *const *argv;
const char *optstring;
{
return _getopt_internal (argc, argv, optstring,
(const struct option *) 0,
(int *) 0,
0);
}
#endif /* _LIBC or not __GNU_LIBRARY__. */
#ifdef TEST
/* Compile with -DTEST to make an executable for use in testing
the above definition of `getopt'. */
int
main (argc, argv)
int argc;
char **argv;
{
int c;
int digit_optind = 0;
while (1)
{
int this_option_optind = optind ? optind : 1;
c = getopt (argc, argv, "abc:d:0123456789");
if (c == EOF)
break;
switch (c)
{
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
if (digit_optind != 0 && digit_optind != this_option_optind)
printf ("digits occur in two different argv-elements.\n");
digit_optind = this_option_optind;
printf ("option %c\n", c);
break;
case 'a':
printf ("option a\n");
break;
case 'b':
printf ("option b\n");
break;
case 'c':
printf ("option c with value `%s'\n", optarg);
break;
case '?':
break;
default:
printf ("?? getopt returned character code 0%o ??\n", c);
}
}
if (optind < argc)
{
printf ("non-option ARGV-elements: ");
while (optind < argc)
printf ("%s ", argv[optind++]);
printf ("\n");
}
exit (0);
}
#endif /* TEST */
getopt.h 0 → 100644
View file @ fa87aa42
/* Declarations for getopt.
Copyright (C) 1989, 90, 91, 92, 93, 94 Free Software Foundation, Inc.
This file is part of the GNU C Library. Its master source is NOT part of
the C library, however. The master source lives in /gd/gnu/lib.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
#ifndef _GETOPT_H
#define _GETOPT_H 1
#ifdef __cplusplus
extern "C" {
#endif
/* For communication from `getopt' to the caller.
When `getopt' finds an option that takes an argument,
the argument value is returned here.
Also, when `ordering' is RETURN_IN_ORDER,
each non-option ARGV-element is returned here. */
extern char *optarg;
/* Index in ARGV of the next element to be scanned.
This is used for communication to and from the caller
and for communication between successive calls to `getopt'.
On entry to `getopt', zero means this is the first call; initialize.
When `getopt' returns EOF, this is the index of the first of the
non-option elements that the caller should itself scan.
Otherwise, `optind' communicates from one call to the next
how much of ARGV has been scanned so far. */
extern int optind;
/* Callers store zero here to inhibit the error message `getopt' prints
for unrecognized options. */
extern int opterr;
/* Set to an option character which was unrecognized. */
extern int optopt;
/* Describe the long-named options requested by the application.
The LONG_OPTIONS argument to getopt_long or getopt_long_only is a vector
of `struct option' terminated by an element containing a name which is
zero.
The field `has_arg' is:
no_argument (or 0) if the option does not take an argument,
required_argument (or 1) if the option requires an argument,
optional_argument (or 2) if the option takes an optional argument.
If the field `flag' is not NULL, it points to a variable that is set
to the value given in the field `val' when the option is found, but
left unchanged if the option is not found.
To have a long-named option do something other than set an `int' to
a compiled-in constant, such as set a value from `optarg', set the
option's `flag' field to zero and its `val' field to a nonzero
value (the equivalent single-letter option character, if there is
one). For long options that have a zero `flag' field, `getopt'
returns the contents of the `val' field. */
struct option
{
#if defined (__STDC__) && __STDC__
const char *name;
#else
char *name;
#endif
/* has_arg can't be an enum because some compilers complain about
type mismatches in all the code that assumes it is an int. */
int has_arg;
int *flag;
int val;
};
/* Names for the values of the `has_arg' field of `struct option'. */
#define no_argument 0
#define required_argument 1
#define optional_argument 2
#if defined (__STDC__) && __STDC__
#ifdef __GNU_LIBRARY__
/* Many other libraries have conflicting prototypes for getopt, with
differences in the consts, in stdlib.h. To avoid compilation
errors, only prototype getopt for the GNU C library. */
extern int getopt (int argc, char *const *argv, const char *shortopts);
#else /* not __GNU_LIBRARY__ */
extern int getopt ();
#endif /* __GNU_LIBRARY__ */
extern int getopt_long (int argc, char *const *argv, const char *shortopts,
const struct option *longopts, int *longind);
extern int getopt_long_only (int argc, char *const *argv,
const char *shortopts,
const struct option *longopts, int *longind);
/* Internal only. Users should not call this directly. */
extern int _getopt_internal (int argc, char *const *argv,
const char *shortopts,
const struct option *longopts, int *longind,
int long_only);
#else /* not __STDC__ */
extern int getopt ();
extern int getopt_long ();
extern int getopt_long_only ();
extern int _getopt_internal ();
#endif /* __STDC__ */
#ifdef __cplusplus
}
#endif
#endif /* _GETOPT_H */
hobbit.txt 0 → 100644
View file @ fa87aa42
Netcat 1.10
=========== /\_/\
/ 0 0 \
Netcat is a simple Unix utility which reads and writes data ====v====
across network connections, using TCP or UDP protocol. \ W /
It is designed to be a reliable "back-end" tool that can | | _
be used directly or easily driven by other programs and / ___ \ /
scripts. At the same time, it is a feature-rich network / / \ \ |
debugging and exploration tool, since it can create almost (((-----)))-'
any kind of connection you would need and has several /
interesting built-in capabilities. Netcat, or "nc" as the ( ___
actual program is named, should have been supplied long ago \__.=|___E
as another one of those cryptic but standard Unix tools. /
In the simplest usage, "nc host port" creates a TCP connection to the given
port on the given target host. Your standard input is then sent to the host,
and anything that comes back across the connection is sent to your standard
output. This continues indefinitely, until the network side of the connection
shuts down. Note that this behavior is different from most other applications
which shut everything down and exit after an end-of-file on the standard input.
Netcat can also function as a server, by listening for inbound connections
on arbitrary ports and then doing the same reading and writing. With minor
limitations, netcat doesn't really care if it runs in "client" or "server"
mode -- it still shovels data back and forth until there isn't any more left.
In either mode, shutdown can be forced after a configurable time of inactivity
on the network side.
And it can do this via UDP too, so netcat is possibly the "udp telnet-like"
application you always wanted for testing your UDP-mode servers. UDP, as the
"U" implies, gives less reliable data transmission than TCP connections and
some systems may have trouble sending large amounts of data that way, but it's
still a useful capability to have.
You may be asking "why not just use telnet to connect to arbitrary ports?"
Valid question, and here are some reasons. Telnet has the "standard input
EOF" problem, so one must introduce calculated delays in driving scripts to
allow network output to finish. This is the main reason netcat stays running
until the *network* side closes. Telnet also will not transfer arbitrary
binary data, because certain characters are interpreted as telnet options and
are thus removed from the data stream. Telnet also emits some of its
diagnostic messages to standard output, where netcat keeps such things
religiously separated from its *output* and will never modify any of the real
data in transit unless you *really* want it to. And of course telnet is
incapable of listening for inbound connections, or using UDP instead. Netcat
doesn't have any of these limitations, is much smaller and faster than telnet,
and has many other advantages.
Some of netcat's major features are:
Outbound or inbound connections, TCP or UDP, to or from any ports
Full DNS forward/reverse checking, with appropriate warnings
Ability to use any local source port
Ability to use any locally-configured network source address
Built-in port-scanning capabilities, with randomizer
Built-in loose source-routing capability
Can read command line arguments from standard input
Slow-send mode, one line every N seconds
Hex dump of transmitted and received data
Optional ability to let another program service established connections
Optional telnet-options responder
Efforts have been made to have netcat "do the right thing" in all its various
modes. If you believe that it is doing the wrong thing under whatever
circumstances, please notify me and tell me how you think it should behave.
If netcat is not able to do some task you think up, minor tweaks to the code
will probably fix that. It provides a basic and easily-modified template for
writing other network applications, and I certainly encourage people to make
custom mods and send in any improvements they make to it. This is the second
release; the overall differences from 1.00 are relatively minor and have mostly
to do with portability and bugfixes. Many people provided greatly appreciated
fixes and comments on the 1.00 release. Continued feedback from the Internet
community is always welcome!
Netcat is entirely my own creation, although plenty of other code was used as
examples. It is freely given away to the Internet community in the hope that
it will be useful, with no restrictions except giving credit where it is due.
No GPLs, Berkeley copyrights or any of that nonsense. The author assumes NO
responsibility for how anyone uses it. If netcat makes you rich somehow and
you're feeling generous, mail me a check. If you are affiliated in any way
with Microsoft Network, get a life. Always ski in control. Comments,
questions, and patches to hobbit@avian.org.
Building
========
Compiling is fairly straightforward. Examine the Makefile for a SYSTYPE that
matches yours, and do "make <systype>". The executable "nc" should appear.
If there is no relevant SYSTYPE section, try "generic". If you create new
sections for generic.h and Makefile to support another platform, please follow
the given format and mail back the diffs.
There are a couple of other settable #defines in netcat.c, which you can
include as DFLAGS="-DTHIS -DTHAT" to your "make" invocation without having to
edit the Makefile. See the following discussions for what they are and do.
If you want to link against the resolver library on SunOS [recommended] and
you have BIND 4.9.x, you may need to change XLIBS=-lresolv in the Makefile to
XLIBS="-lresolv -l44bsd".
Linux sys/time.h does not really support presetting of FD_SETSIZE; a harmless
warning is issued.
Some systems may warn about pointer types for signal(). No problem, though.
Exploration of features
=======================
Where to begin? Netcat is at the same time so simple and versatile, it's like
trying to describe everything you can do with your Swiss Army knife. This will
go over the basics; you should also read the usage examples and notes later on
which may give you even more ideas about what this sort of tool is good for.
If no command arguments are given at all, netcat asks for them, reads a line
from standard input, and breaks it up into arguments internally. This can be
useful when driving netcat from certain types of scripts, with the side effect
of hiding your command line arguments from "ps" displays.
The host argument can be a name or IP address. If -n is specified, netcat
will only accept numeric IP addresses and do no DNS lookups for anything. If
-n is not given and -v is turned on, netcat will do a full forward and reverse
name and address lookup for the host, and warn you about the all-too-common
problem of mismatched names in the DNS. This often takes a little longer for
connection setup, but is useful to know about. There are circumstances under
which this can *save* time, such as when you want to know the name for some IP
address and also connect there. Netcat will just tell you all about it, saving
the manual steps of looking up the hostname yourself. Normally mismatch-
checking is case-insensitive per the DNS spec, but you can define ANAL at
compile time to make it case-sensitive -- sometimes useful for uncovering minor
errors in your own DNS files while poking around your networks.
A port argument is required for outbound connections, and can be numeric or a
name as listed in /etc/services. If -n is specified, only numeric arguments
are valid. Special syntax and/or more than one port argument cause different
behavior -- see details below about port-scanning.
The -v switch controls the verbosity level of messages sent to standard error.
You will probably want to run netcat most of the time with -v turned on, so you
can see info about the connections it is trying to make. You will probably
also want to give a smallish -w argument, which limits the time spent trying to
make a connection. I usually alias "nc" to "nc -v -w 3", which makes it
function just about the same for things I would otherwise use telnet to do.
The timeout is easily changed by a subsequent -w argument which overrides the
earlier one. Specifying -v more than once makes diagnostic output MORE
verbose. If -v is not specified at all, netcat silently does its work unless
some error happens, whereupon it describes the error and exits with a nonzero
status. Refused network connections are generally NOT considered to be errors,
unless you only asked for a single TCP port and it was refused.
Note that -w also sets the network inactivity timeout. This does not have any
effect until standard input closes, but then if nothing further arrives from
the network in the next <timeout> seconds, netcat tries to read the net once
more for good measure, and then closes and exits. There are a lot of network
services now that accept a small amount of input and return a large amount of
output, such as Gopher and Web servers, which is the main reason netcat was
written to "block" on the network staying open rather than standard input.
Handling the timeout this way gives uniform behavior with network servers that
*don't* close by themselves until told to.
UDP connections are opened instead of TCP when -u is specified. These aren't
really "connections" per se since UDP is a connectionless protocol, although
netcat does internally use the "connected UDP socket" mechanism that most
kernels support. Although netcat claims that an outgoing UDP connection is
"open" immediately, no data is sent until something is read from standard
input. Only thereafter is it possible to determine whether there really is a
UDP server on the other end, and often you just can't tell. Most UDP protocols
use timeouts and retries to do their thing and in many cases won't bother
answering at all, so you should specify a timeout and hope for the best. You
will get more out of UDP connections if standard input is fed from a source
of data that looks like various kinds of server requests.
To obtain a hex dump file of the data sent either way, use "-o logfile". The
dump lines begin with "<" or ">" to respectively indicate "from the net" or
"to the net", and contain the total count per direction, and hex and ascii
representations of the traffic. Capturing a hex dump naturally slows netcat
down a bit, so don't use it where speed is critical.
Netcat can bind to any local port, subject to privilege restrictions and ports
that are already in use. It is also possible to use a specific local network
source address if it is that of a network interface on your machine. [Note:
this does not work correctly on all platforms.] Use "-p portarg" to grab a
specific local port, and "-s ip-addr" or "-s name" to have that be your source
IP address. This is often referred to as "anchoring the socket". Root users
can grab any unused source port including the "reserved" ones less than 1024.
Absence of -p will bind to whatever unused port the system gives you, just like
any other normal client connection, unless you use -r [see below].
Listen mode will cause netcat to wait for an inbound connection, and then the
same data transfer happens. Thus, you can do "nc -l -p 1234 < filename" and
when someone else connects to your port 1234, the file is sent to them whether
they wanted it or not. Listen mode is generally used along with a local port
argument -- this is required for UDP mode, while TCP mode can have the system
assign one and tell you what it is if -v is turned on. If you specify a target
host and optional port in listen mode, netcat will accept an inbound connection
only from that host and if you specify one, only from that foreign source port.
In verbose mode you'll be informed about the inbound connection, including what
address and port it came from, and since listening on "any" applies to several
possibilities, which address it came *to* on your end. If the system supports
IP socket options, netcat will attempt to retrieve any such options from an
inbound connection and print them out in hex.
If netcat is compiled with -DGAPING_SECURITY_HOLE, the -e argument specifies
a program to exec after making or receiving a successful connection. In the
listening mode, this works similarly to "inetd" but only for a single instance.
Use with GREAT CARE. This piece of the code is normally not enabled; if you
know what you're doing, have fun. This hack also works in UDP mode. Note that
you can only supply -e with the name of the program, but no arguments. If you
want to launch something with an argument list, write a two-line wrapper script
or just use inetd like always.
If netcat is compiled with -DTELNET, the -t argument enables it to respond
to telnet option negotiation [always in the negative, i.e. DONT or WONT].
This allows it to connect to a telnetd and get past the initial negotiation
far enough to get a login prompt from the server. Since this feature has
the potential to modify the data stream, it is not enabled by default. You
have to understand why you might need this and turn on the #define yourself.
Data from the network connection is always delivered to standard output as
efficiently as possible, using large 8K reads and writes. Standard input is
normally sent to the net the same way, but the -i switch specifies an "interval
time" which slows this down considerably. Standard input is still read in
large batches, but netcat then tries to find where line breaks exist and sends
one line every interval time. Note that if standard input is a terminal, data
is already read line by line, so unless you make the -i interval rather long,
what you type will go out at a fairly normal rate. -i is really designed
for use when you want to "measure out" what is read from files or pipes.
Port-scanning is a popular method for exploring what's out there. Netcat
accepts its commands with options first, then the target host, and everything
thereafter is interpreted as port names or numbers, or ranges of ports in M-N
syntax. CAVEAT: some port names in /etc/services contain hyphens -- netcat
currently will not correctly parse those, so specify ranges using numbers if
you can. If more than one port is thus specified, netcat connects to *all* of
them, sending the same batch of data from standard input [up to 8K worth] to
each one that is successfully connected to. Specifying multiple ports also
suppresses diagnostic messages about refused connections, unless -v is
specified twice for "more verbosity". This way you normally get notified only
about genuinely open connections. Example: "nc -v -w 2 -z target 20-30" will
try connecting to every port between 20 and 30 [inclusive] at the target, and
will likely inform you about an FTP server, telnet server, and mailer along the
way. The -z switch prevents sending any data to a TCP connection and very
limited probe data to a UDP connection, and is thus useful as a fast scanning
mode just to see what ports the target is listening on. To limit scanning
speed if desired, -i will insert a delay between each port probe. There are
some pitfalls with regard to UDP scanning, described later, but in general it
works well.
For each range of ports specified, scanning is normally done downward within
that range. If the -r switch is used, scanning hops randomly around within
that range and reports open ports as it finds them. [If you want them listed
in order regardless, pipe standard error through "sort"...] In addition, if
random mode is in effect, the local source ports are also randomized. This
prevents netcat from exhibiting any kind of regular pattern in its scanning.
You can exert fairly fine control over your scan by judicious use of -r and
selected port ranges to cover. If you use -r for a single connection, the
source port will have a random value above 8192, rather than the next one the
kernel would have assigned you. Note that selecting a specific local port
with -p overrides any local-port randomization.
Many people are interested in testing network connectivity using IP source
routing, even if it's only to make sure their own firewalls are blocking
source-routed packets. On systems that support it, the -g switch can be used
multiple times [up to 8] to construct a loose-source-routed path for your
connection, and the -G argument positions the "hop pointer" within the list.
If your network allows source-routed traffic in and out, you can test
connectivity to your own services via remote points in the internet. Note that
although newer BSD-flavor telnets also have source-routing capability, it isn't
clearly documented and the command syntax is somewhat clumsy. Netcat's
handling of "-g" is modeled after "traceroute".
Netcat tries its best to behave just like "cat". It currently does nothing to
terminal input modes, and does no end-of-line conversion. Standard input from
a terminal is read line by line with normal editing characters in effect. You
can freely suspend out of an interactive connection and resume. ^C or whatever
your interrupt character is will make netcat close the network connection and
exit. A switch to place the terminal in raw mode has been considered, but so
far has not been necessary. You can send raw binary data by reading it out of
a file or piping from another program, so more meaningful effort would be spent
writing an appropriate front-end driver.
Netcat is not an "arbitrary packet generator", but the ability to talk to raw
sockets and/or nit/bpf/dlpi may appear at some point. Such things are clearly
useful; I refer you to Darren Reed's excellent ip_filter package, which now
includes a tool to construct and send raw packets with any contents you want.
Example uses -- the light side
==============================
Again, this is a very partial list of possibilities, but it may get you to
think up more applications for netcat. Driving netcat with simple shell or
expect scripts is an easy and flexible way to do fairly complex tasks,
especially if you're not into coding network tools in C. My coding isn't
particularly strong either [although undoubtedly better after writing this
thing!], so I tend to construct bare-metal tools like this that I can trivially
plug into other applications. Netcat doubles as a teaching tool -- one can
learn a great deal about more complex network protocols by trying to simulate
them through raw connections!
An example of netcat as a backend for something else is the shell-script
Web browser, which simply asks for the relevant parts of a URL and pipes
"GET /what/ever" into a netcat connection to the server. I used to do this
with telnet, and had to use calculated sleep times and other stupidity to
kludge around telnet's limitations. Netcat guarantees that I get the whole
page, and since it transfers all the data unmodified, I can even pull down
binary image files and display them elsewhere later. Some folks may find the
idea of a shell-script web browser silly and strange, but it starts up and
gets me my info a hell of a lot faster than a GUI browser and doesn't hide
any contents of links and forms and such. This is included, as scripts/web,
along with several other web-related examples.
Netcat is an obvious replacement for telnet as a tool for talking to daemons.
For example, it is easier to type "nc host 25", talk to someone's mailer, and
just ^C out than having to type ^]c or QUIT as telnet would require you to do.
You can quickly catalog the services on your network by telling netcat to
connect to well-known services and collect greetings, or at least scan for open
ports. You'll probably want to collect netcat's diagnostic messages in your
output files, so be sure to include standard error in the output using
`>& file' in *csh or `> file 2>&1' in bourne shell.
A scanning example: "echo QUIT | nc -v -w 5 target 20-250 500-600 5990-7000"
will inform you about a target's various well-known TCP servers, including
r-services, X, IRC, and maybe a few you didn't expect. Sending in QUIT and
using the timeout will almost guarantee that you see some kind of greeting or
error from each service, which usually indicates what it is and what version.
[Beware of the "chargen" port, though...] SATAN uses exactly this technique to
collect host information, and indeed some of the ideas herein were taken from
the SATAN backend tools. If you script this up to try every host in your
subnet space and just let it run, you will not only see all the services,
you'll find out about hosts that aren't correctly listed in your DNS. Then you
can compare new snapshots against old snapshots to see changes. For going
after particular services, a more intrusive example is in scripts/probe.
Netcat can be used as a simple data transfer agent, and it doesn't really
matter which end is the listener and which end is the client -- input at one
side arrives at the other side as output. It is helpful to start the listener
at the receiving side with no timeout specified, and then give the sending side
a small timeout. That way the listener stays listening until you contact it,
and after data stops flowing the client will time out, shut down, and take the
listener with it. Unless the intervening network is fraught with problems,
this should be completely reliable, and you can always increase the timeout. A
typical example of something "rsh" is often used for: on one side,
nc -l -p 1234 | uncompress -c | tar xvfp -
and then on the other side
tar cfp - /some/dir | compress -c | nc -w 3 othermachine 1234
will transfer the contents of a directory from one machine to another, without
having to worry about .rhosts files, user accounts, or inetd configurations
at either end. Again, it matters not which is the listener or receiver; the
"tarring" machine could just as easily be running the listener instead. One
could conceivably use a scheme like this for backups, by having cron-jobs fire
up listeners and backup handlers [which can be restricted to specific addresses
and ports between each other] and pipe "dump" or "tar" on one machine to "dd
of=/dev/tapedrive" on another as usual. Since netcat returns a nonzero exit
status for a denied listener connection, scripts to handle such tasks could
easily log and reject connect attempts from third parties, and then retry.
Another simple data-transfer example: shipping things to a PC that doesn't have
any network applications yet except a TCP stack and a web browser. Point the
browser at an arbitrary port on a Unix server by telling it to download
something like http://unixbox:4444/foo, and have a listener on the Unix side
ready to ship out a file when the connect comes in. The browser may pervert
binary data when told to save the URL, but you can dig the raw data out of
the on-disk cache.
If you build netcat with GAPING_SECURITY_HOLE defined, you can use it as an
"inetd" substitute to test experimental network servers that would otherwise
run under "inetd". A script or program will have its input and output hooked
to the network the same way, perhaps sans some fancier signal handling. Given
that most network services do not bind to a particular local address, whether
they are under "inetd" or not, it is possible for netcat avoid the "address
already in use" error by binding to a specific address. This lets you [as
root, for low ports] place netcat "in the way" of a standard service, since
inbound connections are generally sent to such specifically-bound listeners
first and fall back to the ones bound to "any". This allows for a one-off
experimental simulation of some service, without having to screw around with
inetd.conf. Running with -v turned on and collecting a connection log from
standard error is recommended.
Netcat as well can make an outbound connection and then run a program or script
on the originating end, with input and output connected to the same network
port. This "inverse inetd" capability could enhance the backup-server concept
described above or help facilitate things such as a "network dialback" concept.
The possibilities are many and varied here; if such things are intended as
security mechanisms, it may be best to modify netcat specifically for the
purpose instead of wrapping such functions in scripts.
Speaking of inetd, netcat will function perfectly well *under* inetd as a TCP
connection redirector for inbound services, like a "plug-gw" without the
authentication step. This is very useful for doing stuff like redirecting
traffic through your firewall out to other places like web servers and mail
hubs, while posing no risk to the firewall machine itself. Put netcat behind
inetd and tcp_wrappers, perhaps thusly:
www stream tcp nowait nobody /etc/tcpd /bin/nc -w 3 realwww 80
and you have a simple and effective "application relay" with access control
and logging. Note use of the wait time as a "safety" in case realwww isn't
reachable or the calling user aborts the connection -- otherwise the relay may
hang there forever.
You can use netcat to generate huge amounts of useless network data for
various performance testing. For example, doing
yes AAAAAAAAAAAAAAAAAAAAAA | nc -v -v -l -p 2222 > /dev/null
on one side and then hitting it with
yes BBBBBBBBBBBBBBBBBBBBBB | nc othermachine 2222 > /dev/null
from another host will saturate your wires with A's and B's. The "very
verbose" switch usage will tell you how many of each were sent and received
after you interrupt either side. Using UDP mode produces tremendously MORE
trash per unit time in the form of fragmented 8 Kbyte mobygrams -- enough to
stress-test kernels and network interfaces. Firing random binary data into
various network servers may help expose bugs in their input handling, which
nowadays is a popular thing to explore. A simple example data-generator is
given in data/data.c included in this package, along with a small collection
of canned input files to generate various packet contents. This program is
documented in its beginning comments, but of interest here is using "%r" to
generate random bytes at well-chosen points in a data stream. If you can
crash your daemon, you likely have a security problem.
The hex dump feature may be useful for debugging odd network protocols,
especially if you don't have any network monitoring equipment handy or aren't
root where you'd need to run "tcpdump" or something. Bind a listening netcat
to a local port, and have it run a script which in turn runs another netcat
to the real service and captures the hex dump to a log file. This sets up a
transparent relay between your local port and wherever the real service is.
Be sure that the script-run netcat does *not* use -v, or the extra info it
sends to standard error may confuse the protocol. Note also that you cannot
have the "listen/exec" netcat do the data capture, since once the connection
arrives it is no longer netcat that is running.
Binding to an arbitrary local port allows you to simulate things like r-service
clients, if you are root locally. For example, feeding "^@root^@joe^@pwd^@"
[where ^@ is a null, and root/joe could be any other local/remote username
pair] into a "rsh" or "rlogin" server, FROM your port 1023 for example,
duplicates what the server expects to receive. Thus, you can test for insecure
.rhosts files around your network without having to create new user accounts on
your client machine. The program data/rservice.c can aid this process by
constructing the "rcmd" protocol bytes. Doing this also prevents "rshd" from
trying to create that separate standard-error socket and still gives you an
input path, as opposed to the usual action of "rsh -n". Using netcat for
things like this can be really useful sometimes, because rsh and rlogin
generally want a host *name* as an argument and won't accept IP addresses. If
your client-end DNS is hosed, as may be true when you're trying to extract
backup sets on to a dumb client, "netcat -n" wins where normal rsh/rlogin is
useless.
If you are unsure that a remote syslogger is working, test it with netcat.
Make a UDP connection to port 514 and type in "<0>message", which should
correspond to "kern.emerg" and cause syslogd to scream into every file it has
open [and possibly all over users' terminals]. You can tame this down by
using a different number and use netcat inside routine scripts to send syslog
messages to places that aren't configured in syslog.conf. For example,
"echo '<38>message' | nc -w 1 -u loggerhost 514" should send to auth.notice
on loggerhost. The exact number may vary; check against your syslog.h first.
Netcat provides several ways for you to test your own packet filters. If you
bind to a port normally protected against outside access and make a connection
to somewhere outside your own network, the return traffic will be coming to
your chosen port from the "outside" and should be blocked. TCP may get through
if your filter passes all "ack syn", but it shouldn't be even doing that to low
ports on your network. Remember to test with UDP traffic as well! If your
filter passes at least outbound source-routed IP packets, bouncing a connection
back to yourself via some gateway outside your network will create "incoming"
traffic with your source address, which should get dropped by a correctly
configured anti-spoofing filter. This is a "non-test" if you're also dropping
source-routing, but it's good to be able to test for that too. Any packet
filter worth its salt will be blocking source-routed packets in both
directions, but you never know what interesting quirks you might turn up by
playing around with source ports and addresses and watching the wires with a
network monitor.
You can use netcat to protect your own workstation's X server against outside
access. X is stupid enough to listen for connections on "any" and never tell
you when new connections arrive, which is one reason it is so vulnerable. Once
you have all your various X windows up and running you can use netcat to bind
just to your ethernet address and listen to port 6000. Any new connections
from outside the machine will hit netcat instead your X server, and you get a
log of who's trying. You can either tell netcat to drop the connection, or
perhaps run another copy of itself to relay to your actual X server on
"localhost". This may not work for dedicated X terminals, but it may be
possible to authorize your X terminal only for its boot server, and run a relay
netcat over on the server that will in turn talk to your X terminal. Since
netcat only handles one listening connection per run, make sure that whatever
way you rig it causes another one to run and listen on 6000 soon afterward, or
your real X server will be reachable once again. A very minimal script just
to protect yourself could be
while true ; do
nc -v -l -s <your-addr> -p 6000 localhost 2
done
which causes netcat to accept and then close any inbound connection to your
workstation's normal ethernet address, and another copy is immediately run by
the script. Send standard error to a file for a log of connection attempts.
If your system can't do the "specific bind" thing all is not lost; run your
X server on display ":1" or port 6001, and netcat can still function as a probe
alarm by listening on 6000.
Does your shell-account provider allow personal Web pages, but not CGI scripts?
You can have netcat listen on a particular port to execute a program or script
of your choosing, and then just point to the port with a URL in your homepage.
The listener could even exist on a completely different machine, avoiding the
potential ire of the homepage-host administrators. Since the script will get
the raw browser query as input it won't look like a typical CGI script, and
since it's running under your UID you need to write it carefully. You may want
to write a netcat-based script as a wrapper that reads a query and sets up
environment variables for a regular CGI script. The possibilities for using
netcat and scripts to handle Web stuff are almost endless. Again, see the
examples under scripts/.
Example uses -- the dark side
=============================
Equal time is deserved here, since a versatile tool like this can be useful
to any Shade of Hat. I could use my Victorinox to either fix your car or
disassemble it, right? You can clearly use something like netcat to attack
or defend -- I don't try to govern anyone's social outlook, I just build tools.
Regardless of your intentions, you should still be aware of these threats to
your own systems.
The first obvious thing is scanning someone *else's* network for vulnerable
services. Files containing preconstructed data, be it exploratory or
exploitive, can be fed in as standard input, including command-line arguments
to netcat itself to keep "ps" ignorant of your doings. The more random the
scanning, the less likelihood of detection by humans, scan-detectors, or
dynamic filtering, and with -i you'll wait longer but avoid loading down the
target's network. Some examples for crafting various standard UDP probes are
given in data/*.d.
Some configurations of packet filters attempt to solve the FTP-data problem by
just allowing such connections from the outside. These come FROM port 20, TO
high TCP ports inside -- if you locally bind to port 20, you may find yourself
able to bypass filtering in some cases. Maybe not to low ports "inside", but
perhaps to TCP NFS servers, X servers, Prospero, ciscos that listen on 200x
and 400x... Similar bypassing may be possible for UDP [and maybe TCP too] if a
connection comes from port 53; a filter may assume it's a nameserver response.
Using -e in conjunction with binding to a specific address can enable "server
takeover" by getting in ahead of the real ones, whereupon you can snarf data
sent in and feed your own back out. At the very least you can log a hex dump
of someone else's session. If you are root, you can certainly use -s and -e to
run various hacked daemons without having to touch inetd.conf or the real
daemons themselves. You may not always have the root access to deal with low
ports, but what if you are on a machine that also happens to be an NFS server?
You might be able to collect some interesting things from port 2049, including
local file handles. There are several other servers that run on high ports
that are likely candidates for takeover, including many of the RPC services on
some platforms [yppasswdd, anyone?]. Kerberos tickets, X cookies, and IRC
traffic also come to mind. RADIUS-based terminal servers connect incoming
users to shell-account machines on a high port, usually 1642 or thereabouts.
SOCKS servers run on 1080. Do "netstat -a" and get creative.
There are some daemons that are well-written enough to bind separately to all
the local interfaces, possibly with an eye toward heading off this sort of
problem. Named from recent BIND releases, and NTP, are two that come to mind.
Netstat will show these listening on address.53 instead of *.53. You won't
be able to get in front of these on any of the real interface addresses, which
of course is especially interesting in the case of named, but these servers
sometimes forget about things like "alias" interface addresses or interfaces
that appear later on such as dynamic PPP links. There are some hacked web
servers and versions of "inetd" floating around that specifically bind as well,
based on a configuration file -- these generally *are* bound to alias addresses
to offer several different address-based services from one machine.
Using -e to start a remote backdoor shell is another obvious sort of thing,
easier than constructing a file for inetd to listen on "ingreslock" or
something, and you can access-control it against other people by specifying a
client host and port. Experience with this truly demonstrates how fragile the
barrier between being "logged in" or not really is, and is further expressed by
scripts/bsh. If you're already behind a firewall, it may be easier to make an
*outbound* connection and then run a shell; a small wrapper script can
periodically try connecting to a known place and port, you can later listen
there until the inbound connection arrives, and there's your shell. Running
a shell via UDP has several interesting features, although be aware that once
"connected", the UDP stub sockets tend to show up in "netstat" just like TCP
connections and may not be quite as subtle as you wanted. Packets may also be
lost, so use TCP if you need reliable connections. But since UDP is
connectionless, a hookup of this sort will stick around almost forever, even if
you ^C out of netcat or do a reboot on your side, and you only need to remember
the ports you used on both ends to reestablish. And outbound UDP-plus-exec
connection creates the connected socket and starts the program immediately. On
a listening UDP connection, the socket is created once a first packet is
received. In either case, though, such a "connection" has the interesting side
effect that only your client-side IP address and [chosen?] source port will
thereafter be able to talk to it. Instant access control! A non-local third
party would have to do ALL of the following to take over such a session:
forge UDP with your source address [trivial to do; see below]
guess the port numbers of BOTH ends, or sniff the wire for them
arrange to block ICMP or UDP return traffic between it and your real
source, so the session doesn't die with a network write error.
The companion program data/rservice.c is helpful in scripting up any sort of
r-service username or password guessing attack. The arguments to "rservice"
are simply the strings that get null-terminated and passed over an "rcmd"-style
connection, with the assumption that the client does not need a separate
standard-error port. Brute-force password banging is best done via "rexec" if
it is available since it is less likely to log failed attempts. Thus, doing
"rservice joe joespass pwd | nc target exec" should return joe's home dir if
the password is right, or "Permission denied." Plug in a dictionary and go to
town. If you're attacking rsh/rlogin, remember to be root and bind to a port
between 512 and 1023 on your end, and pipe in "rservice joe joe pwd" and such.
Netcat can prevent inadvertently sending extra information over a telnet
connection. Use "nc -t" in place of telnet, and daemons that try to ask for
things like USER and TERM environment variables will get no useful answers, as
they otherwise would from a more recent telnet program. Some telnetds actually
try to collect this stuff and then plug the USER variable into "login" so that
the caller is then just asked for a password! This mechanism could cause a
login attempt as YOUR real username to be logged over there if you use a
Borman-based telnet instead of "nc -t".
Got an unused network interface configured in your kernel [e.g. SLIP], or
support for alias addresses? Ifconfig one to be any address you like, and bind
to it with -s to enable all sorts of shenanigans with bogus source addresses.
The interface probably has to be UP before this works; some SLIP versions
need a far-end address before this is true. Hammering on UDP services is then
a no-brainer. What you can do to an unfiltered syslog daemon should be fairly
obvious; trimming the conf file can help protect against it. Many routers out
there still blindly believe what they receive via RIP and other routing
protocols. Although most UDP echo and chargen servers check if an incoming
packet was sent from *another* "internal" UDP server, there are many that still
do not, any two of which [or many, for that matter] could keep each other
entertained for hours at the expense of bandwidth. And you can always make
someone wonder why she's being probed by nsa.gov.
Your TCP spoofing possibilities are mostly limited to destinations you can
source-route to while locally bound to your phony address. Many sites block
source-routed packets these days for precisely this reason. If your kernel
does oddball things when sending source-routed packets, try moving the pointer
around with -G. You may also have to fiddle with the routing on your own
machine before you start receiving packets back. Warning: some machines still
send out traffic using the source address of the outbound interface, regardless
of your binding, especially in the case of localhost. Check first. If you can
open a connection but then get no data back from it, the target host is
probably killing the IP options on its end [this is an option inside TCP
wrappers and several other packages], which happens after the 3-way handshake
is completed. If you send some data and observe the "send-q" side of "netstat"
for that connection increasing but never getting sent, that's another symptom.
Beware: if Sendmail 8.7.x detects a source-routed SMTP connection, it extracts
the hop list and sticks it in the Received: header!
SYN bombing [sometimes called "hosing"] can disable many TCP servers, and if
you hit one often enough, you can keep it unreachable for days. As is true of
many other denial-of-service attacks, there is currently no defense against it
except maybe at the human level. Making kernel SOMAXCONN considerably larger
than the default and the half-open timeout smaller can help, and indeed some
people running large high-performance web servers have *had* to do that just to
handle normal traffic. Taking out mailers and web servers is sociopathic, but
on the other hand it is sometimes useful to be able to, say, disable a site's
identd daemon for a few minutes. If someone realizes what is going on,
backtracing will still be difficult since the packets have a phony source
address, but calls to enough ISP NOCs might eventually pinpoint the source.
It is also trivial for a clueful ISP to watch for or even block outgoing
packets with obviously fake source addresses, but as we know many of them are
not clueful or willing to get involved in such hassles. Besides, outbound
packets with an [otherwise unreachable] source address in one of their net
blocks would look fairly legitimate.
Notes
=====
A discussion of various caveats, subtleties, and the design of the innards.
As of version 1.07 you can construct a single file containing command arguments
and then some data to transfer. Netcat is now smart enough to pick out the
first line and build the argument list, and send any remaining data across the
net to one or multiple ports. The first release of netcat had trouble with
this -- it called fgets() for the command line argument, which behind the
scenes does a large read() from standard input, perhaps 4096 bytes or so, and
feeds that out to the fgets() library routine. By the time netcat 1.00 started
directly read()ing stdin for more data, 4096 bytes of it were gone. It now
uses raw read() everywhere and does the right thing whether reading from files,
pipes, or ttys. If you use this for multiple-port connections, the single
block of data will now be a maximum of 8K minus the first line. Improvements
have been made to the logic in sending the saved chunk to each new port. Note
that any command-line arguments hidden using this mechanism could still be
extracted from a core dump.
When netcat receives an inbound UDP connection, it creates a "connected socket"
back to the source of the connection so that it can also send out data using
normal write(). Using this mechanism instead of recvfrom/sendto has several
advantages -- the read/write select loop is simplified, and ICMP errors can in
effect be received by non-root users. However, it has the subtle side effect
that if further UDP packets arrive from the caller but from different source
ports, the listener will not receive them. UDP listen mode on a multihomed
machine may have similar quirks unless you specifically bind to one of its
addresses. It is not clear that kernel support for UDP connected sockets
and/or my understanding of it is entirely complete here, so experiment...
You should be aware of some subtleties concerning UDP scanning. If -z is on,
netcat attempts to send a single null byte to the target port, twice, with a
small time in between. You can either use the -w timeout, or netcat will try
to make a "sideline" TCP connection to the target to introduce a small time
delay equal to the round-trip time between you and the target. Note that if
you have a -w timeout and -i timeout set, BOTH take effect and you wait twice
as long. The TCP connection is to a normally refused port to minimize traffic,
but if you notice a UDP fast-scan taking somewhat longer than it should, it
could be that the target is actually listening on the TCP port. Either way,
any ICMP port-unreachable messages from the target should have arrived in the
meantime. The second single-byte UDP probe is then sent. Under BSD kernels,
the ICMP error is delivered to the "connected socket" and the second write
returns an error, which tells netcat that there is NOT a UDP service there.
While Linux seems to be a fortunate exception, under many SYSV derived kernels
the ICMP is not delivered, and netcat starts reporting that *all* the ports are
"open" -- clearly wrong. [Some systems may not even *have* the "udp connected
socket" concept, and netcat in its current form will not work for UDP at all.]
If -z is specified and only one UDP port is probed, netcat's exit status
reflects whether the connection was "open" or "refused" as with TCP.
It may also be that UDP packets are being blocked by filters with no ICMP error
returns, in which case everything will time out and return "open". This all
sounds backwards, but that's how UDP works. If you're not sure, try "echo
w00gumz | nc -u -w 2 target 7" to see if you can reach its UDP echo port at
all. You should have no trouble using a BSD-flavor system to scan for UDP
around your own network, although flooding a target with the high activity that
-z generates will cause it to occasionally drop packets and indicate false
"opens". A more "correct" way to do this is collect and analyze the ICMP
errors, as does SATAN's "udp_scan" backend, but then again there's no guarantee
that the ICMP gets back to you either. Udp_scan also does the zero-byte
probes but is excruciatingly careful to calculate its own round-trip timing
average and dynamically set its own response timeouts along with decoding any
ICMP received. Netcat uses a much sleazier method which is nonetheless quite
effective. Cisco routers are known to have a "dead time" in between ICMP
responses about unreachable UDP ports, so a fast scan of a cisco will show
almost everything "open". If you are looking for a specific UDP service, you
can construct a file containing the right bytes to trigger a response from the
other end and send that as standard input. Netcat will read up to 8K of the
file and send the same data to every UDP port given. Note that you must use a
timeout in this case [as would any other UDP client application] since the
two-write probe only happens if -z is specified.
Many telnet servers insist on a specific set of option negotiations before
presenting a login banner. On a raw connection you will see this as small
amount of binary gook. My attempts to create fixed input bytes to make a
telnetd happy worked some places but failed against newer BSD-flavor ones,
possibly due to timing problems, but there are a couple of much better
workarounds. First, compile with -DTELNET and use -t if you just want to get
past the option negotiation and talk to something on a telnet port. You will
still see the binary gook -- in fact you'll see a lot more of it as the options
are responded to behind the scenes. The telnet responder does NOT update the
total byte count, or show up in the hex dump -- it just responds negatively to
any options read from the incoming data stream. If you want to use a normal
full-blown telnet to get to something but also want some of netcat's features
involved like settable ports or timeouts, construct a tiny "foo" script:
#! /bin/sh
exec nc -otheroptions targethost 23
and then do
nc -l -p someport -e foo localhost &
telnet localhost someport
and your telnet should connect transparently through the exec'ed netcat to
the target, using whatever options you supplied in the "foo" script. Don't
use -t inside the script, or you'll wind up sending *two* option responses.
I've observed inconsistent behavior under some Linuxes [perhaps just older
ones?] when binding in listen mode. Sometimes netcat binds only to "localhost"
if invoked with no address or port arguments, and sometimes it is unable to
bind to a specific address for listening if something else is already listening
on "any". The former problem can be worked around by specifying "-s 0.0.0.0",
which will do the right thing despite netcat claiming that it's listening on
[127.0.0.1]. This is a known problem -- for example, there's a mention of it
in the makefile for SOCKS. On the flip side, binding to localhost and sending
packets to some other machine doesn't work as you'd expect -- they go out with
the source address of the sending interface instead. The Linux kernel contains
a specific check to ensure that packets from 127.0.0.1 are never sent to the
wire; other kernels may contain similar code. Linux, of course, *still*
doesn't support source-routing, but they claim that it and many other network
improvements are at least breathing hard.
There are several possible errors associated with making TCP connections, but
to specifically see anything other than "refused", one must wait the full
kernel-defined timeout for a connection to fail. Netcat's mechanism of
wrapping an alarm timer around the connect prevents the *real* network error
from being returned -- "errno" at that point indicates "interrupted system
call" since the connect attempt was interrupted. Some old 4.3 BSD kernels
would actually return things like "host unreachable" immediately if that was
the case, but most newer kernels seem to wait the full timeout and *then* pass
back the real error. Go figure. In this case, I'd argue that the old way was
better, despite those same kernels generally being the ones that tear down
*established* TCP connections when ICMP-bombed.
Incoming socket options are passed to applications by the kernel in the
kernel's own internal format. The socket-options structure for source-routing
contains the "first-hop" IP address first, followed by the rest of the real
options list. The kernel uses this as is when sending reply packets -- the
structure is therefore designed to be more useful to the kernel than to humans,
but the hex dump of it that netcat produces is still useful to have.
Kernels treat source-routing options somewhat oddly, but it sort of makes sense
once one understands what's going on internally. The options list of addresses
must contain hop1, hop2, ..., destination. When a source-routed packet is sent
by the kernel [at least BSD], the actual destination address becomes irrelevant
because it is replaced with "hop1", "hop1" is removed from the options list,
and all the other addresses in the list are shifted up to fill the hole. Thus
the outbound packet is sent from your chosen source address to the first
*gateway*, and the options list now contains hop2, ..., destination. During
all this address shuffling, the kernel does NOT change the pointer value, which
is why it is useful to be able to set the pointer yourself -- you can construct
some really bizarre return paths, and send your traffic fairly directly to the
target but around some larger loop on the way back. Some Sun kernels seem to
never flip the source-route around if it contains less than three hops, never
reset the pointer anyway, and tries to send the packet [with options containing
a "completed" source route!!] directly back to the source. This is way broken,
of course. [Maybe ipforwarding has to be on? I haven't had an opportunity to
beat on it thoroughly yet.]
"Credits" section: The original idea for netcat fell out of a long-standing
desire and fruitless search for a tool resembling it and having the same
features. After reading some other network code and realizing just how many
cool things about sockets could be controlled by the calling user, I started
on the basics and the rest fell together pretty quickly. Some port-scanning
ideas were taken from Venema/Farmer's SATAN tool kit, and Pluvius' "pscan"
utility. Healthy amounts of BSD kernel source were perused in an attempt to
dope out socket options and source-route handling; additional help was obtained
from Dave Borman's telnet sources. The select loop is loosely based on fairly
well-known code from "rsh" and Richard Stevens' "sock" program [which itself is
sort of a "netcat" with more obscure features], with some more paranoid
sanity-checking thrown in to guard against the distinct likelihood that there
are subtleties about such things I still don't understand. I found the
argument-hiding method cleanly implemented in Barrett's "deslogin"; reading the
line as input allows greater versatility and is much less prone to cause
bizarre problems than the more common trick of overwriting the argv array.
After the first release, several people contributed portability fixes; they are
credited in generic.h and the Makefile. Lauren Burka inspired the ascii art
for this revised document. Dean Gaudet at Wired supplied a precursor to
the hex-dump code, and mudge@l0pht.com originally experimented with and
supplied code for the telnet-options responder. Outbound "-e <prog>" resulted
from a need to quietly bypass a firewall installation. Other suggestions and
patches have rolled in for which I am always grateful, but there are only 26
hours per day and a discussion of feature creep near the end of this document.
Netcat was written with the Russian railroad in mind -- conservatively built
and solid, but it *will* get you there. While the coding style is fairly
"tight", I have attempted to present it cleanly [keeping *my* lines under 80
characters, dammit] and put in plenty of comments as to why certain things
are done. Items I know to be questionable are clearly marked with "XXX".
Source code was made to be modified, but determining where to start is
difficult with some of the tangles of spaghetti code that are out there.
Here are some of the major points I feel are worth mentioning about netcat's
internal design, whether or not you agree with my approach.
Except for generic.h, which changes to adapt more platforms, netcat is a single
source file. This has the distinct advantage of only having to include headers
once and not having to re-declare all my functions in a billion different
places. I have attempted to contain all the gross who's-got-what-.h-file
things in one small dumping ground. Functions are placed "dependencies-first",
such that when the compiler runs into the calls later, it already knows the
type and arguments and won't complain. No function prototyping -- not even the
__P(()) crock -- is used, since it is more portable and a file of this size is
easy enough to check manually. Each function has a standard-format comment
ahead of it, which is easily found using the regexp " :$". I freely use gotos.
Loops and if-clauses are made as small and non-nested as possible, and the ends
of same *marked* for clarity [I wish everyone would do this!!].
Large structures and buffers are all malloc()ed up on the fly, slightly larger
than the size asked for and zeroed out. This reduces the chances of damage
from those "end of the buffer" fencepost errors or runaway pointers escaping
off the end. These things are permanent per run, so nothing needs to be freed
until the program exits.
File descriptor zero is always expected to be standard input, even if it is
closed. If a new network descriptor winds up being zero, a different one is
asked for which will be nonzero, and fd zero is simply left kicking around
for the rest of the run. Why? Because everything else assumes that stdin is
always zero and "netfd" is always positive. This may seem silly, but it was a
lot easier to code. The new fd is obtained directly as a new socket, because
trying to simply dup() a new fd broke subsequent socket-style use of the new fd
under Solaris' stupid streams handling in the socket library.
The catch-all message and error handlers are implemented with an ample list of
phoney arguments to get around various problems with varargs. Varargs seems
like deliberate obfuscation in the first place, and using it would also
require use of vfprintf() which not all platforms support. The trailing
sleep in bail() is to allow output to flush, which is sometimes needed if
netcat is already on the other end of a network connection.
The reader may notice that the section that does DNS lookups seems much
gnarlier and more confusing than other parts. This is NOT MY FAULT. The
sockaddr and hostent abstractions are an abortion that forces the coder to
deal with it. Then again, a lot of BSD kernel code looks like similar
struct-pointer hell. I try to straighten it out somewhat by defining my own
HINF structure, containing names, ascii-format IP addresses, and binary IP
addresses. I fill this structure exactly once per host argument, and squirrel
everything safely away and handy for whatever wants to reference it later.
Where many other network apps use the FIONBIO ioctl to set non-blocking I/O
on network sockets, netcat uses straightforward blocking I/O everywhere.
This makes everything very lock-step, relying on the network and filesystem
layers to feed in data when needed. Data read in is completely written out
before any more is fetched. This may not be quite the right thing to do under
some OSes that don't do timed select() right, but this remains to be seen.
The hexdump routine is written to be as fast as possible, which is why it does
so much work itself instead of just sprintf()ing everything together. Each
dump line is built into a single buffer and atomically written out using the
lowest level I/O calls. Further improvements could undoubtedly be made by
using writev() and eliminating all sprintf()s, but it seems to fly right along
as is. If both exec-a-prog mode and a hexdump file is asked for, the hexdump
flag is deliberately turned off to avoid creating random zero-length files.
Files are opened in "truncate" mode; if you want "append" mode instead, change
the open flags in main().
main() may look a bit hairy, but that's only because it has to go down the
argv list and handle multiple ports, random mode, and exit status. Efforts
have been made to place a minimum of code inside the getopt() loop. Any real
work is sent off to functions in what is hopefully a straightforward way.
Obligatory vendor-bash: If "nc" had become a standard utility years ago,
the commercial vendors would have likely packaged it setuid root and with
-DGAPING_SECURITY_HOLE turned on but not documented. It is hoped that netcat
will aid people in finding and fixing the no-brainer holes of this sort that
keep appearing, by allowing easier experimentation with the "bare metal" of
the network layer.
It could be argued that netcat already has too many features. I have tried
to avoid "feature creep" by limiting netcat's base functionality only to those
things which are truly relevant to making network connections and the everyday
associated DNS lossage we're used to. Option switches already have slightly
overloaded functionality. Random port mode is sort of pushing it. The
hex-dump feature went in later because it *is* genuinely useful. The
telnet-responder code *almost* verges on the gratuitous, especially since it
mucks with the data stream, and is left as an optional piece. Many people have
asked for example "how 'bout adding encryption?" and my response is that such
things should be separate entities that could pipe their data *through* netcat
instead of having their own networking code. I am therefore not completely
enthusiastic about adding any more features to this thing, although you are
still free to send along any mods you think are useful.
Nonetheless, at this point I think of netcat as my tcp/ip swiss army knife,
and the numerous companion programs and scripts to go with it as duct tape.
Duct tape of course has a light side and a dark side and binds the universe
together, and if I wrap enough of it around what I'm trying to accomplish,
it *will* work. Alternatively, if netcat is a large hammer, there are many
network protocols that are increasingly looking like nails by now...
_H* 960320 v1.10 RELEASE -- happy spring!
license.txt 0 → 100644
View file @ fa87aa42
GNU GENERAL PUBLIC LICENSE
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12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.
<one line to give the program's name and a brief idea of what it does.>
Copyright (C) <year> <name of author>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Also add information on how to contact you by electronic and paper mail.
If the program is interactive, make it output a short notice like this
when it starts in an interactive mode:
Gnomovision version 69, Copyright (C) year name of author
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License. Of course, the commands you use may
be called something other than `show w' and `show c'; they could even be
mouse-clicks or menu items--whatever suits your program.
You should also get your employer (if you work as a programmer) or your
school, if any, to sign a "copyright disclaimer" for the program, if
necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the program
`Gnomovision' (which makes passes at compilers) written by James Hacker.
<signature of Ty Coon>, 1 April 1989
Ty Coon, President of Vice
This General Public License does not permit incorporating your program into
proprietary programs. If your program is a subroutine library, you may
consider it more useful to permit linking proprietary applications with the
library. If this is what you want to do, use the GNU Library General
Public License instead of this License.
nc.exe 0 → 100644
View file @ fa87aa42
File added
nc64.exe 0 → 100644
View file @ fa87aa42
File added
netcat.c 0 → 100644
View file @ fa87aa42
// for license see license.txt
/* Netcat 1.00 951010
A damn useful little "backend" utility begun 950915 or thereabouts,
as *Hobbit*'s first real stab at some sockets programming. Something that
should have and indeed may have existed ten years ago, but never became a
standard Unix utility. IMHO, "nc" could take its place right next to cat,
cp, rm, mv, dd, ls, and all those other cryptic and Unix-like things.
Read the README for the whole story, doc, applications, etc.
Layout:
conditional includes:
includes:
handy defines:
globals:
malloced globals:
cmd-flag globals:
support routines:
main:
todo:
more of the portability swamp, and an updated generic.h
frontend progs to generate various packets, raw or otherwise...
char-mode [cbreak, fcntl-unbuffered, etc...]
connect-to-all-A-records hack
bluesky:
RAW mode!
backend progs to grab a pty and look like a real telnetd?!
*/
#include "generic.h" /* same as with L5, skey, etc */
#ifdef WIN32
#pragma comment (lib, "ws2_32") /* winsock support */
#endif
/* conditional includes -- a very messy section: */
/* #undef _POSIX_SOURCE /* might need this for something? */
#define HAVE_BIND /* XXX -- for now, see below... */
#define HAVE_HELP /* undefine if you dont want the help text */
/* #define ANAL /* if you want case-sensitive DNS matching */
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#else
#include <malloc.h> /* xxx: or does it live in sys/ ?? */
#endif
/* have to do this *before* including types.h. xxx: Linux still has it wrong */
#ifdef FD_SETSIZE /* should be in types.h, butcha never know. */
#undef FD_SETSIZE /* if we ever need more than 16 active */
#endif /* fd's, something is horribly wrong! */
#ifdef WIN32
#define FD_SETSIZE 64 /* WIN32 does this as an array not a bitfield and it likes 64 */
#else
#define FD_SETSIZE 16 /* <-- this'll give us a long anyways, wtf */
#endif
#include <sys/types.h> /* *now* do it. Sigh, this is broken */
#ifdef WIN32
#undef HAVE_RANDOM
#undef IP_OPTIONS
#undef SO_REUSEPORT
#include <windows.h>
#endif
#ifdef HAVE_RANDOM
#define SRAND srandom
#define RAND random
#else
#define SRAND srand
#define RAND rand
#endif /* HAVE_RANDOM */
/* xxx: these are rsh leftovers, move to new generic.h */
/* will we even need any nonblocking shit? Doubt it. */
/* get FIONBIO from sys/filio.h, so what if it is a compatibility feature */
/* #include <sys/filio.h> */
/*
#include <sys/ioctl.h>
#include <sys/file.h>
*/
/* includes: */
#ifdef WIN32
#include "getopt.h"
#define sleep _sleep
#define strcasecmp strcmpi
#define EADDRINUSE WSAEADDRINUSE
#define ETIMEDOUT WSAETIMEDOUT
#define ECONNREFUSED WSAECONNREFUSED
#endif
#ifndef WIN32
#include <sys/time.h> /* timeval, time_t */
#else
#include <time.h>
#endif
#include <setjmp.h> /* jmp_buf et al */
#ifndef WIN32
#include <sys/socket.h> /* basics, SO_ and AF_ defs, sockaddr, ... */
#include <netinet/in.h> /* sockaddr_in, htons, in_addr */
#include <netinet/in_systm.h> /* misc crud that netinet/ip.h references */
#include <netinet/ip.h> /* IPOPT_LSRR, header stuff */
#include <netdb.h> /* hostent, gethostby*, getservby* */
#include <arpa/inet.h> /* inet_ntoa */
#else
#include <fcntl.h>
#include <io.h>
#include <conio.h>
//#include <winsock2.h>
#endif
#include <stdio.h>
#include <string.h> /* strcpy, strchr, yadda yadda */
#include <errno.h>
#include <signal.h>
/* handy stuff: */
#define SA struct sockaddr /* socket overgeneralization braindeath */
#define SAI struct sockaddr_in /* ... whoever came up with this model */
#define IA struct in_addr /* ... should be taken out and shot, */
/* ... not that TLI is any better. sigh.. */
#define SLEAZE_PORT 31337 /* for UDP-scan RTT trick, change if ya want */
#define USHORT unsigned short /* use these for options an' stuff */
#define BIGSIZ 8192 /* big buffers */
#define SMALLSIZ 256 /* small buffers, hostnames, etc */
#ifndef INADDR_NONE
#define INADDR_NONE 0xffffffff
#endif
#ifdef MAXHOSTNAMELEN
#undef MAXHOSTNAMELEN /* might be too small on aix, so fix it */
#endif
#define MAXHOSTNAMELEN 256
struct host_poop {
char name[MAXHOSTNAMELEN]; /* dns name */
char addrs[8][24]; /* ascii-format IP addresses */
struct in_addr iaddrs[8]; /* real addresses: in_addr.s_addr: ulong */
};
#define HINF struct host_poop
struct port_poop {
char name [64]; /* name in /etc/services */
char anum [8]; /* ascii-format number */
USHORT num; /* real host-order number */
};
#define PINF struct port_poop
/* globals: */
jmp_buf jbuf; /* timer crud */
int jval = 0; /* timer crud */
int netfd = -1;
int ofd = 0; /* hexdump output fd */
static char unknown[] = "(UNKNOWN)";
static char p_tcp[] = "tcp"; /* for getservby* */
static char p_udp[] = "udp";
#ifndef WIN32
#ifdef HAVE_BIND
extern int h_errno;
#endif
#endif
int gatesidx = 0; /* LSRR hop count */
int gatesptr = 4; /* initial LSRR pointer, settable */
USHORT Single = 1; /* zero if scanning */
unsigned int insaved = 0; /* stdin-buffer size for multi-mode */
unsigned int wrote_out = 0; /* total stdout bytes */
unsigned int wrote_net = 0; /* total net bytes */
static char wrote_txt[] = " sent %d, rcvd %d";
static char hexnibs[20] = "0123456789abcdef ";
/* will malloc up the following globals: */
struct timeval * timer1 = NULL;
struct timeval * timer2 = NULL;
SAI * lclend = NULL; /* sockaddr_in structs */
SAI * remend = NULL;
HINF ** gates = NULL; /* LSRR hop hostpoop */
char * optbuf = NULL; /* LSRR or sockopts */
char * bigbuf_in; /* data buffers */
char * bigbuf_net;
fd_set * ding1; /* for select loop */
fd_set * ding2;
PINF * portpoop = NULL; /* for getportpoop / getservby* */
unsigned char * stage = NULL; /* hexdump line buffer */
#ifdef WIN32
char * setsockopt_c;
int nnetfd;
#endif
/* global cmd flags: */
USHORT o_alla = 0;
unsigned int o_interval = 0;
USHORT o_listen = 0;
USHORT o_nflag = 0;
USHORT o_wfile = 0;
USHORT o_random = 0;
USHORT o_udpmode = 0;
USHORT o_verbose = 0;
unsigned int o_wait = 0;
USHORT o_zero = 0;
USHORT o_crlf = 0;
/* Debug macro: squirt whatever to stderr and sleep a bit so we can see it go
by. need to call like Debug ((stuff)) [with no ; ] so macro args match!
Beware: writes to stdOUT... */
#ifdef DEBUG
#define Debug(x) printf x; printf ("\n"); fflush (stdout); sleep (1);
#else
#define Debug(x) /* nil... */
#endif
/* support routines -- the bulk of this thing. Placed in such an order that
we don't have to forward-declare anything: */
int helpme(); /* oop */
#ifdef WIN32
/* res_init
winsock needs to be initialized. Might as well do it as the res_init
call for Win32 */
void res_init()
{
WORD wVersionRequested;
WSADATA wsaData;
int err;
wVersionRequested = MAKEWORD(1, 1);
err = WSAStartup(wVersionRequested, &wsaData);
if (err != 0)
/* Tell the user that we couldn't find a useable */
/* winsock.dll. */
return;
/* Confirm that the Windows Sockets DLL supports 1.1.*/
/* Note that if the DLL supports versions greater */
/* than 1.1 in addition to 1.1, it will still return */
/* 1.1 in wVersion since that is the version we */
/* requested. */
if ( LOBYTE( wsaData.wVersion ) != 1 ||
HIBYTE( wsaData.wVersion ) != 1 ) {
/* Tell the user that we couldn't find a useable */
/* winsock.dll. */
WSACleanup();
return;
}
}
/* winsockstr
Windows Sockets cannot report errors through perror() so we need to define
our own error strings to print. Someday all the string should be prettied up.
Prettied the errors I usually get */
char * winsockstr(error)
int error;
{
switch (error)
{
case WSAEINTR : return("INTR ");
case WSAEBADF : return("BADF ");
case WSAEACCES : return("ACCES ");
case WSAEFAULT : return("FAULT ");
case WSAEINVAL : return("INVAL ");
case WSAEMFILE : return("MFILE ");
case WSAEWOULDBLOCK : return("WOULDBLOCK ");
case WSAEINPROGRESS : return("INPROGRESS ");
case WSAEALREADY : return("ALREADY ");
case WSAENOTSOCK : return("NOTSOCK ");
case WSAEDESTADDRREQ : return("DESTADDRREQ ");
case WSAEMSGSIZE : return("MSGSIZE ");
case WSAEPROTOTYPE : return("PROTOTYPE ");
case WSAENOPROTOOPT : return("NOPROTOOPT ");
case WSAEPROTONOSUPPORT: return("PROTONOSUPPORT");
case WSAESOCKTNOSUPPORT: return("SOCKTNOSUPPORT");
case WSAEOPNOTSUPP : return("OPNOTSUPP ");
case WSAEPFNOSUPPORT : return("PFNOSUPPORT ");
case WSAEAFNOSUPPORT : return("AFNOSUPPORT ");
case WSAEADDRINUSE : return("ADDRINUSE ");
case WSAEADDRNOTAVAIL : return("ADDRNOTAVAIL ");
case WSAENETDOWN : return("NETDOWN ");
case WSAENETUNREACH : return("NETUNREACH ");
case WSAENETRESET : return("NETRESET ");
case WSAECONNABORTED : return("CONNABORTED ");
case WSAECONNRESET : return("CONNRESET ");
case WSAENOBUFS : return("NOBUFS ");
case WSAEISCONN : return("ISCONN ");
case WSAENOTCONN : return("NOTCONN ");
case WSAESHUTDOWN : return("SHUTDOWN ");
case WSAETOOMANYREFS : return("TOOMANYREFS ");
case WSAETIMEDOUT : return("TIMEDOUT ");
case WSAECONNREFUSED : return("connection refused");
case WSAELOOP : return("LOOP ");
case WSAENAMETOOLONG : return("NAMETOOLONG ");
case WSAEHOSTDOWN : return("HOSTDOWN ");
case WSAEHOSTUNREACH : return("HOSTUNREACH ");
case WSAENOTEMPTY : return("NOTEMPTY ");
case WSAEPROCLIM : return("PROCLIM ");
case WSAEUSERS : return("USERS ");
case WSAEDQUOT : return("DQUOT ");
case WSAESTALE : return("STALE ");
case WSAEREMOTE : return("REMOTE ");
case WSAEDISCON : return("DISCON ");
case WSASYSNOTREADY : return("SYSNOTREADY ");
case WSAVERNOTSUPPORTED: return("VERNOTSUPPORTED");
case WSANOTINITIALISED : return("NOTINITIALISED ");
case WSAHOST_NOT_FOUND : return("HOST_NOT_FOUND ");
case WSATRY_AGAIN : return("TRY_AGAIN ");
case WSANO_RECOVERY : return("NO_RECOVERY ");
case WSANO_DATA : return("NO_DATA ");
default : return("unknown socket error");
}
}
#endif
/* holler :
fake varargs -- need to do this way because we wind up calling through
more levels of indirection than vanilla varargs can handle, and not all
machines have vfprintf/vsyslog/whatever! 6 params oughta be enough. */
void holler (str, p1, p2, p3, p4, p5, p6)
char * str;
char * p1, * p2, * p3, * p4, * p5, * p6;
{
if (o_verbose) {
fprintf (stderr, str, p1, p2, p3, p4, p5, p6);
#ifdef WIN32
if (h_errno)
fprintf (stderr, ": %s\n",winsockstr(h_errno));
#else
if (errno) { /* this gives funny-looking messages, but */
perror (" "); /* it's more portable than sys_errlist[]... */
} /* xxx: do something better. */
#endif
else
fprintf (stderr, "\n");
fflush (stderr);
}
} /* holler */
/* bail :
error-exit handler, callable from anywhere */
void bail (str, p1, p2, p3, p4, p5, p6)
char * str;
char * p1, * p2, * p3, * p4, * p5, * p6;
{
o_verbose = 1;
holler (str, p1, p2, p3, p4, p5, p6);
#ifdef WIN32
shutdown(netfd, 0x02); /* Kirby */
closesocket (netfd);
#else
close (netfd);
#endif
sleep (1);
exit (1);
} /* bail */
/* catch :
no-brainer interrupt handler */
void catch ()
{
errno = 0;
if (o_verbose > 1) /* normally we don't care */
bail (wrote_txt, wrote_net, wrote_out);
bail (" punt!");
}
/* timeout and other signal handling cruft */
void tmtravel ()
{
#ifdef NTFIXTHIS
signal (SIGALRM, SIG_IGN);
alarm (0);
#endif
if (jval == 0)
bail ("spurious timer interrupt!");
longjmp (jbuf, jval);
}
UINT theTimer;
/* arm :
set the timer. Zero secs arg means unarm */
void arm (num, secs)
unsigned int num;
unsigned int secs;
{
#ifdef WIN32
HANDLE stdhnd;
stdhnd = GetStdHandle(STD_OUTPUT_HANDLE);
#ifdef DEBUG
if (stdhnd != INVALID_HANDLE_VALUE)
printf("handle is %ld\n", stdhnd);
else
printf("failed to get stdhndl\n");
#endif
#else
if (secs == 0) { /* reset */
signal (SIGALRM, SIG_IGN);
alarm (0);
jval = 0;
} else { /* set */
signal (SIGALRM, tmtravel);
alarm (secs);
jval = num;
} /* if secs */
#endif /* WIN32 */
} /* arm */
/* Hmalloc :
malloc up what I want, rounded up to *4, and pre-zeroed. Either succeeds
or bails out on its own, so that callers don't have to worry about it. */
char * Hmalloc (size)
unsigned int size;
{
unsigned int s = (size + 4) & 0xfffffffc; /* 4GB?! */
char * p = malloc (s);
if (p != NULL)
memset (p, 0, s);
else
bail ("Hmalloc %d failed", s);
return (p);
} /* Hmalloc */
/* findline :
find the next newline in a buffer; return inclusive size of that "line",
or the entire buffer size, so the caller knows how much to then write().
Not distinguishing \n vs \r\n for the nonce; it just works as is... */
unsigned int findline (buf, siz)
char * buf;
unsigned int siz;
{
register char * p;
register int x;
if (! buf) /* various sanity checks... */
return (0);
if (siz > BIGSIZ)
return (0);
x = siz;
for (p = buf; x > 0; x--) {
if (*p == '\n') {
x = (int) (p - buf);
x++; /* 'sokay if it points just past the end! */
Debug (("findline returning %d", x))
return (x);
}
p++;
} /* for */
Debug (("findline returning whole thing: %d", siz))
return (siz);
} /* findline */
/* comparehosts :
cross-check the host_poop we have so far against new gethostby*() info,
and holler about mismatches. Perhaps gratuitous, but it can't hurt to
point out when someone's DNS is fukt. Returns 1 if mismatch, in case
someone else wants to do something about it. */
int comparehosts (poop, hp)
HINF * poop;
struct hostent * hp;
{
errno = 0;
#ifndef WIN32
h_errno = 0;
#endif
/* The DNS spec is officially case-insensitive, but for those times when you
*really* wanna see any and all discrepancies, by all means define this. */
#ifdef ANAL
if (strcmp (poop->name, hp->h_name) != 0) { /* case-sensitive */
#else
if (strcasecmp (poop->name, hp->h_name) != 0) { /* normal */
#endif
holler ("DNS fwd/rev mismatch: %s != %s", poop->name, hp->h_name);
return (1);
}
return (0);
/* ... do we need to do anything over and above that?? */
} /* comparehosts */
/* gethostpoop :
resolve a host 8 ways from sunday; return a new host_poop struct with its
info. The argument can be a name or [ascii] IP address; it will try its
damndest to deal with it. "numeric" governs whether we do any DNS at all,
and we also check o_verbose for what's appropriate work to do. */
HINF * gethostpoop (name, numeric)
char * name;
USHORT numeric;
{
struct hostent * hostent;
struct in_addr iaddr;
register HINF * poop = NULL;
register int x;
/* I really want to strangle the twit who dreamed up all these sockaddr and
hostent abstractions, and then forced them all to be incompatible with
each other so you *HAVE* to do all this ridiculous casting back and forth.
If that wasn't bad enough, all the doc insists on referring to local ports
and addresses as "names", which makes NO sense down at the bare metal.
What an absolutely horrid paradigm, and to think of all the people who
have been wasting significant amounts of time fighting with this stupid
deliberate obfuscation over the last 10 years... then again, I like
languages wherein a pointer is a pointer, what you put there is your own
business, the compiler stays out of your face, and sheep are nervous.
Maybe that's why my C code reads like assembler half the time... */
/* If we want to see all the DNS stuff, do the following hair --
if inet_addr, do reverse and forward with any warnings; otherwise try
to do forward and reverse with any warnings. In other words, as long
as we're here, do a complete DNS check on these clowns. Yes, it slows
things down a bit for a first run, but once it's cached, who cares? */
errno = 0;
#ifndef WIN32
h_errno = 0;
#endif
if (name)
poop = (HINF *) Hmalloc (sizeof (HINF));
if (! poop)
bail ("gethostpoop fuxored");
strcpy (poop->name, unknown); /* preload it */
/* see wzv:workarounds.c for dg/ux return-a-struct inet_addr lossage */
iaddr.s_addr = inet_addr (name);
if (iaddr.s_addr == INADDR_NONE) { /* here's the great split: names... */
if (numeric)
bail ("Can't parse %s as an IP address", name);
hostent = gethostbyname (name);
if (! hostent)
/* failure to look up a name is fatal, since we can't do anything with it */
/* XXX: h_errno only if BIND? look up how telnet deals with this */
bail ("%s: forward host lookup failed: h_errno %d", name, h_errno);
strncpy (poop->name, hostent->h_name, sizeof (poop->name));
for (x = 0; hostent->h_addr_list[x] && (x < 8); x++) {
memcpy (&poop->iaddrs[x], hostent->h_addr_list[x], sizeof (IA));
strncpy (poop->addrs[x], inet_ntoa (poop->iaddrs[x]),
sizeof (poop->addrs[0]));
} /* for x -> addrs, part A */
if (! o_verbose) /* if we didn't want to see the */
return (poop); /* inverse stuff, we're done. */
/* do inverse lookups in separate loop based on our collected forward addrs,
since gethostby* tends to crap into the same buffer over and over */
for (x = 0; poop->iaddrs[x].s_addr && (x < 8); x++) {
hostent = gethostbyaddr ((char *)&poop->iaddrs[x],
sizeof (IA), AF_INET);
if ((! hostent) || (! hostent-> h_name))
holler ("Warning: inverse host lookup failed for %s: h_errno %d",
poop->addrs[x], h_errno);
else
(void) comparehosts (poop, hostent);
} /* for x -> addrs, part B */
} else { /* not INADDR_NONE: numeric addresses... */
memcpy (poop->iaddrs, &iaddr, sizeof (IA));
strncpy (poop->addrs[0], inet_ntoa (iaddr), sizeof (poop->addrs));
if (numeric) /* if numeric-only, we're done */
return (poop);
if (! o_verbose) /* likewise if we don't want */
return (poop); /* the full DNS hair */
hostent = gethostbyaddr ((char *) &iaddr, sizeof (IA), AF_INET);
/* numeric or not, failure to look up a PTR is *not* considered fatal */
if (! hostent)
holler ("%s: inverse host lookup failed: h_errno %d", name, h_errno);
else {
strncpy (poop->name, hostent->h_name, MAXHOSTNAMELEN - 2);
hostent = gethostbyname (poop->name);
if ((! hostent) || (! hostent->h_addr_list[0]))
holler ("Warning: forward host lookup failed for %s: h_errno %d",
poop->name, h_errno);
else
(void) comparehosts (poop, hostent);
} /* if hostent */
} /* INADDR_NONE Great Split */
/* whatever-all went down previously, we should now have a host_poop struct
with at least one IP address in it. */
#ifndef WIN32
h_errno = 0;
#endif
return (poop);
} /* gethostpoop */
/* getportpoop :
Same general idea as gethostpoop -- look up a port in /etc/services, fill
in global port_poop, but return the actual port *number*. Pass ONE of:
pstring to resolve stuff like "23" or "exec";
pnum to reverse-resolve something that's already a number.
If o_nflag is on, fill in what we can but skip the getservby??? stuff.
Might as well have consistent behavior here... */
USHORT getportpoop (pstring, pnum)
char * pstring;
unsigned int pnum;
{
struct servent * servent;
#ifndef WIN32
register int x;
register int y;
#else
u_short x;
u_short y;
#endif
char * whichp = p_tcp;
if (o_udpmode)
whichp = p_udp;
portpoop->name[0] = '?'; /* fast preload */
portpoop->name[1] = '\0';
/* case 1: reverse-lookup of a number; placed first since this case is much
more frequent if we're scanning */
if (pnum) {
if (pstring) /* one or the other, pleeze */
return (0);
x = pnum;
if (o_nflag) /* go faster, skip getservbyblah */
goto gp_finish;
y = htons (x); /* gotta do this -- see Fig.1 below */
servent = getservbyport (y, whichp);
if (servent) {
y = ntohs (servent->s_port);
if (x != y) /* "never happen" */
holler ("Warning: port-bynum mismatch, %d != %d", x, y);
strncpy (portpoop->name, servent->s_name, sizeof (portpoop->name));
} /* if servent */
goto gp_finish;
} /* if pnum */
/* case 2: resolve a string, but we still give preference to numbers instead
of trying to resolve conflicts. None of the entries in *my* extensive
/etc/services begins with a digit, so this should "always work" unless
you're at 3com and have some company-internal services defined... */
if (pstring) {
if (pnum) /* one or the other, pleeze */
return (0);
x = atoi (pstring);
if (x)
return (getportpoop (NULL, x)); /* recurse for numeric-string-arg */
if (o_nflag) /* can't use names! */
return (0);
servent = getservbyname (pstring, whichp);
if (servent) {
strncpy (portpoop->name, servent->s_name, sizeof (portpoop->name));
x = ntohs (servent->s_port);
goto gp_finish;
} /* if servent */
} /* if pstring */
return (0); /* catches any problems so far */
/* Obligatory netdb.h-inspired rant: servent.s_port is supposed to be an int.
Despite this, we still have to treat it as a short when copying it around.
Not only that, but we have to convert it *back* into net order for
getservbyport to work. Manpages generally aren't clear on all this, but
there are plenty of examples in which it is just quietly done. More BSD
lossage... since everything getserv* ever deals with is local to our own
host, why bother with all this network-order/host-order crap at all?!
That should be saved for when we want to actually plug the port[s] into
some real network calls -- and guess what, we have to *re*-convert at that
point as well. Fuckheads. */
gp_finish:
/* Fall here whether or not we have a valid servent at this point, with
x containing our [host-order and therefore useful, dammit] port number */
sprintf (portpoop->anum, "%d", x); /* always load any numeric specs! */
portpoop->num = (x & 0xffff); /* ushort, remember... */
return (portpoop->num);
} /* getportpoop */
/* nextport :
Come up with the next port to try, be it random or whatever. "block" is
a ptr to randports array, whose bytes [so far] carry these meanings:
0 ignore
1 to be tested
2 tested [which is set as we find them here]
returns a USHORT random port, or 0 if all the t-b-t ones are used up. */
USHORT nextport (block)
char * block;
{
register unsigned int x;
register unsigned int y;
y = 70000; /* high safety count for rnd-tries */
while (y > 0) {
x = (RAND() & 0xffff);
if (block[x] == 1) { /* try to find a not-done one... */
block[x] = 2;
break;
}
x = 0; /* bummer. */
y--;
} /* while y */
if (x)
return (x);
y = 65535; /* no random one, try linear downsearch */
while (y > 0) { /* if they're all used, we *must* be sure! */
if (block[y] == 1) {
block[y] = 2;
break;
}
y--;
} /* while y */
if (y)
return (y); /* at least one left */
return (0); /* no more left! */
} /* nextport */
/* loadports :
set "to be tested" indications in BLOCK, from LO to HI. Almost too small
to be a separate routine, but makes main() a little cleaner... */
void loadports (block, lo, hi)
char * block;
USHORT lo;
USHORT hi;
{
USHORT x;
if (! block)
bail ("loadports: no block?!");
if ((! lo) || (! hi))
bail ("loadports: bogus values %d, %d", lo, hi);
x = hi;
while (lo <= x) {
block[x] = 1;
x--;
}
} /* loadports */
#ifdef GAPING_SECURITY_HOLE
char * pr00gie = NULL; /* global ptr to -e arg */
#ifdef WIN32
BOOL doexec(SOCKET ClientSocket); // this is in doexec.c
#else
/* doexec :
fiddle all the file descriptors around, and hand off to another prog. Sort
of like a one-off "poor man's inetd". This is the only section of code
that would be security-critical, which is why it's ifdefed out by default.
Use at your own hairy risk; if you leave shells lying around behind open
listening ports you deserve to lose!! */
doexec (fd)
int fd;
{
register char * p;
dup2 (fd, 0); /* the precise order of fiddlage */
#ifdef WIN32
shutdown(fd, SD_BOTH); /* Kirby */
closesocket (fd);
#else
close (fd); /* is apparently crucial; this is */
#endif
dup2 (0, 1); /* swiped directly out of "inetd". */
dup2 (0, 2);
p = strrchr (pr00gie, '/'); /* shorter argv[0] */
if (p)
p++;
else
p = pr00gie;
Debug (("gonna exec %s as %s...", pr00gie, p))
execl (pr00gie, p, NULL);
bail ("exec %s failed", pr00gie); /* this gets sent out. Hmm... */
} /* doexec */
#endif
#endif /* GAPING_SECURITY_HOLE */
/* doconnect :
do all the socket stuff, and return an fd for one of
an open outbound TCP connection
a UDP stub-socket thingie
with appropriate socket options set up if we wanted source-routing, or
an unconnected TCP or UDP socket to listen on.
Examines various global o_blah flags to figure out what-all to do. */
int doconnect (rad, rp, lad, lp)
IA * rad;
USHORT rp;
IA * lad;
USHORT lp;
{
#ifndef WIN32
register int nnetfd;
#endif
register int rr;
int x, y;
errno = 0;
#ifdef WIN32
WSASetLastError(0);
#endif
/* grab a socket; set opts */
if (o_udpmode)
nnetfd = socket (AF_INET, SOCK_DGRAM, IPPROTO_UDP);
else
nnetfd = socket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (nnetfd < 0)
bail ("Can't get socket");
if (nnetfd == 0) /* might *be* zero if stdin was closed! */
nnetfd = dup (nnetfd); /* so fix it. Leave the old 0 hanging. */
#ifdef WIN32
rr = setsockopt (nnetfd, SOL_SOCKET, SO_REUSEADDR, (const char FAR *)setsockopt_c, sizeof (setsockopt_c));
#else
x = 1;
rr = setsockopt (nnetfd, SOL_SOCKET, SO_REUSEADDR, &x, sizeof (x));
#endif
if (rr == -1)
holler ("nnetfd reuseaddr failed"); /* ??? */
#ifdef SO_REUSEPORT /* doesnt exist everywhere... */
#ifdef WIN32
rr = setsockopt (nnetfd, SOL_SOCKET, SO_REUSEPORT, &c, sizeof (c));
#else
rr = setsockopt (nnetfd, SOL_SOCKET, SO_REUSEPORT, &x, sizeof (x));
#endif
if (rr == -1)
holler ("nnetfd reuseport failed"); /* ??? */
#endif
/* fill in all the right sockaddr crud */
lclend->sin_family = AF_INET;
remend->sin_family = AF_INET;
/* if lad/lp, do appropriate binding */
if (lad)
memcpy (&lclend->sin_addr.s_addr, lad, sizeof (IA));
if (lp)
lclend->sin_port = htons (lp);
rr = 0;
if (lad || lp) {
x = (int) lp;
/* try a few times for the local bind, a la ftp-data-port... */
for (y = 4; y > 0; y--) {
rr = bind (nnetfd, (SA *)lclend, sizeof (SA));
if (rr == 0)
break;
if (errno != EADDRINUSE)
break;
else {
holler ("retrying local %s:%d", inet_ntoa (lclend->sin_addr), lp);
sleep (1);
errno = 0; /* clear from sleep */
} /* if EADDRINUSE */
} /* for y counter */
} /* if lad or lp */
if (rr)
bail ("Can't grab %s:%d with bind",
inet_ntoa(lclend->sin_addr), lp);
if (o_listen)
return (nnetfd); /* thanks, that's all for today */
memcpy (&remend->sin_addr.s_addr, rad, sizeof (IA));
remend->sin_port = htons (rp);
/* rough format of LSRR option and explanation of weirdness.
-Option comes after IP-hdr dest addr in packet, padded to *4, and ihl > 5.
-IHL is multiples of 4, i.e. real len = ip_hl << 2.
- type 131 1 ; 0x83: copied, option class 0, number 3
- len 1 ; of *whole* option!
- pointer 1 ; nxt-hop-addr; 1-relative, not 0-relative
- addrlist... var ; 4 bytes per hop-addr
- pad-to-32 var ; ones, i.e. "NOP"
-
-If we want to route A -> B via hops C and D, we must add C, D, *and* B to the
-options list. Why? Because when we hand the kernel A -> B with list C, D, B
-the "send shuffle" inside the kernel changes it into A -> C with list D, B and
-the outbound packet gets sent to C. If B wasn't also in the hops list, the
-final destination would have been lost at this point.
-
-When C gets the packet, it changes it to A -> D with list C', B where C' is
-the interface address that C used to forward the packet. This "records" the
-route hop from B's point of view, i.e. which address points "toward" B. This
-is to make B better able to return the packets. The pointer gets bumped by 4,
-so that D does the right thing instead of trying to forward back to C.
-
-When B finally gets the packet, it sees that the pointer is at the end of the
-LSRR list and is thus "completed". B will then try to use the packet instead
-of forwarding it, i.e. deliver it up to some application.
-
-Note that by moving the pointer yourself, you could send the traffic directly
-to B but have it return via your preconstructed source-route. Playing with
-this and watching "tcpdump -v" is the best way to understand what's going on.
-
-Only works for TCP in BSD-flavor kernels. UDP is a loss; udp_input calls
-stripoptions() early on, and the code to save the srcrt is notdef'ed.
-Linux is also still a loss at 1.3.x it looks like; the lsrr code is { }...
-*/
/* if any -g arguments were given, set up source-routing. We hit this after
the gates are all looked up and ready to rock, any -G pointer is set,
and gatesidx is now the *number* of hops */
if (gatesidx) { /* if we wanted any srcrt hops ... */
/* don't even bother compiling if we can't do IP options here! */
/* #ifdef IP_OPTIONS */
#ifndef WIN32
if (! optbuf) { /* and don't already *have* a srcrt set */
char * opp; /* then do all this setup hair */
optbuf = Hmalloc (48);
opp = optbuf;
*opp++ = IPOPT_LSRR; /* option */
*opp++ = (char)
(((gatesidx + 1) * sizeof (IA)) + 3) & 0xff; /* length */
*opp++ = gatesptr; /* pointer */
/* opp now points at first hop addr -- insert the intermediate gateways */
for ( x = 0; x < gatesidx; x++) {
memcpy (opp, gates[x]->iaddrs, sizeof (IA));
opp += sizeof (IA);
}
/* and tack the final destination on the end [needed!] */
memcpy (opp, rad, sizeof (IA));
opp += sizeof (IA);
*opp = IPOPT_NOP; /* alignment filler */
} /* if empty optbuf */
/* calculate length of whole option mess, which is (3 + [hops] + [final] + 1),
and apply it [have to do this every time through, of course] */
x = ((gatesidx + 1) * sizeof (IA)) + 4;
rr = setsockopt (nnetfd, IPPROTO_IP, IP_OPTIONS, optbuf, x);
if (rr == -1)
bail ("srcrt setsockopt fuxored");
#else /* IP_OPTIONS */
holler ("Warning: source routing unavailable on this machine, ignoring");
#endif /* IP_OPTIONS*/
} /* if gatesidx */
/* wrap connect inside a timer, and hit it */
arm (1, o_wait);
if (setjmp (jbuf) == 0) {
rr = connect (nnetfd, (SA *)remend, sizeof (SA));
} else { /* setjmp: connect failed... */
rr = -1;
#ifdef WIN32
WSASetLastError(WSAETIMEDOUT); /* fake it */
#else
errno = ETIMEDOUT; /* fake it */
#endif
}
arm (0, 0);
if (rr == 0)
return (nnetfd);
#ifdef WIN32
errno = h_errno;
shutdown(nnetfd, 0x02); /* Kirby */
closesocket (nnetfd);
WSASetLastError(errno); /* don't want to lose connect error */
#else
close (nnetfd); /* clean up junked socket FD!! */
#endif
return (-1);
} /* doconnect */
/* dolisten :
just like doconnect, and in fact calls a hunk of doconnect, but listens for
incoming and returns an open connection *from* someplace. If we were
given host/port args, any connections from elsewhere are rejected. This
in conjunction with local-address binding should limit things nicely... */
int dolisten (rad, rp, lad, lp)
IA * rad;
USHORT rp;
IA * lad;
USHORT lp;
{
register int nnetfd;
register int rr;
HINF * whozis = NULL;
int x;
char * cp;
USHORT z;
errno = 0;
/* Pass everything off to doconnect, who in o_listen mode just gets a socket */
nnetfd = doconnect (rad, rp, lad, lp);
if (nnetfd <= 0)
return (-1);
if (o_udpmode) { /* apparently UDP can listen ON */
if (! lp) /* "port 0", but that's not useful */
bail ("UDP listen needs -p arg");
} else {
rr = listen (nnetfd, 1); /* gotta listen() before we can get */
if (rr < 0) /* our local random port. sheesh. */
bail ("local listen fuxored");
}
/* I can't believe I have to do all this to get my own goddamn bound address
and port number. It should just get filled in during bind() or something.
All this is only useful if we didn't say -p for listening, since if we
said -p we *know* what port we're listening on. At any rate we won't bother
with it all unless we wanted to see it, although listening quietly on a
random unknown port is probably not very useful without "netstat". */
if (o_verbose) {
x = sizeof (SA); /* how 'bout getsockNUM instead, pinheads?! */
rr = getsockname (nnetfd, (SA *) lclend, &x);
if (rr < 0)
holler ("local getsockname failed");
strcpy (bigbuf_net, "listening on ["); /* buffer reuse... */
if (lclend->sin_addr.s_addr)
strcat (bigbuf_net, inet_ntoa (lclend->sin_addr));
else
strcat (bigbuf_net, "any");
strcat (bigbuf_net, "] %d ...");
z = ntohs (lclend->sin_port);
holler (bigbuf_net, z);
} /* verbose -- whew!! */
/* UDP is a speeeeecial case -- we have to do I/O *and* get the calling
party's particulars all at once, listen() and accept() don't apply.
At least in the BSD universe, however, recvfrom/PEEK is enough to tell
us something came in, and we can set things up so straight read/write
actually does work after all. Yow. YMMV on strange platforms! */
if (o_udpmode) {
x = sizeof (SA); /* retval for recvfrom */
arm (2, o_wait); /* might as well timeout this, too */
if (setjmp (jbuf) == 0) { /* do timeout for initial connect */
rr = recvfrom /* and here we block... */
(nnetfd, bigbuf_net, BIGSIZ, MSG_PEEK, (SA *) remend, &x);
Debug (("dolisten/recvfrom ding, rr = %d, netbuf %s ", rr, bigbuf_net))
} else
goto dol_tmo; /* timeout */
arm (0, 0);
/* I'm not completely clear on how this works -- BSD seems to make UDP
just magically work in a connect()ed context, but we'll undoubtedly run
into systems this deal doesn't work on. For now, we apparently have to
issue a connect() on our just-tickled socket so we can write() back.
Again, why the fuck doesn't it just get filled in and taken care of?!
This hack is anything but optimal. Basically, if you want your listener
to also be able to send data back, you need this connect() line, which
also has the side effect that now anything from a different source or even a
different port on the other end won't show up and will cause ICMP errors.
I guess that's what they meant by "connect".
Let's try to remember what the "U" is *really* for, eh?
*/
rr = connect (nnetfd, (SA *)remend, sizeof (SA));
goto whoisit;
} /* o_udpmode */
/* fall here for TCP */
x = sizeof (SA); /* retval for accept */
arm (2, o_wait); /* wrap this in a timer, too; 0 = forever */
if (setjmp (jbuf) == 0) {
rr = accept (nnetfd, (SA *)remend, &x);
} else
goto dol_tmo; /* timeout */
arm (0, 0);
#ifdef WIN32
shutdown(nnetfd, 0x02); /* Kirby */
closesocket (nnetfd);
#else
close (nnetfd); /* dump the old socket */
#endif
nnetfd = rr; /* here's our new one */
whoisit:
if (rr < 0)
goto dol_err; /* bail out if any errors so far */
/* Various things that follow temporarily trash bigbuf_net, which might contain
a copy of any recvfrom()ed packet, but we'll read() another copy later. */
/* If we can, look for any IP options. Useful for testing the receiving end of
such things, and is a good exercise in dealing with it. We do this before
the connect message, to ensure that the connect msg is uniformly the LAST
thing to emerge after all the intervening crud. Doesn't work for UDP on
any machines I've tested, but feel free to surprise me. */
/* #ifdef IP_OPTIONS */
#ifndef WIN32
if (! o_verbose) /* if we wont see it, we dont care */
goto dol_noop;
optbuf = Hmalloc (40);
x = 40;
rr = getsockopt (nnetfd, IPPROTO_IP, IP_OPTIONS, optbuf, &x);
if (rr < 0)
holler ("getsockopt failed");
Debug (("ipoptions ret len %d", x))
if (x) { /* we've got options, lessee em... */
unsigned char * q = (unsigned char *) optbuf;
char * p = bigbuf_net; /* local variables, yuk! */
char * pp = &bigbuf_net[128]; /* get random space farther out... */
memset (bigbuf_net, 0, 256); /* clear it all first */
while (x > 0) {
sprintf (pp, "%2.2x ", *q); /* clumsy, but works: turn into hex */
strcat (p, pp); /* and build the final string */
q++; p++;
x--;
}
holler ("IP options: %s", bigbuf_net);
} /* if x, i.e. any options */
dol_noop:
#endif /* IP_OPTIONS */
/* find out what address the connection was *to* on our end, in case we're
doing a listen-on-any on a multihomed machine. This allows one to
offer different services via different alias addresses, such as the
"virtual web site" hack. */
memset (bigbuf_net, 0, 64);
cp = &bigbuf_net[32];
x = sizeof (SA);
rr = getsockname (nnetfd, (SA *) lclend, &x);
if (rr < 0)
holler ("post-rcv getsockname failed");
strcpy (cp, inet_ntoa (lclend->sin_addr));
/* now check out who it is. We don't care about mismatched DNS names here,
but any ADDR and PORT we specified had better fucking well match the caller.
Converting from addr to inet_ntoa and back again is a bit of a kludge, but
gethostpoop wants a string and there's much gnarlier code out there already,
so I don't feel bad.
The *real* question is why BFD sockets wasn't designed to allow listens for
connections *from* specific hosts/ports, instead of requiring the caller to
accept the connection and then reject undesireable ones by closing. */
z = ntohs (remend->sin_port);
strcpy (bigbuf_net, inet_ntoa (remend->sin_addr));
whozis = gethostpoop (bigbuf_net, o_nflag);
errno = 0;
x = 0; /* use as a flag... */
if (rad)
if (memcmp (rad, whozis->iaddrs, sizeof (SA)))
x = 1;
if (rp)
if (z != rp)
x = 1;
if (x) /* guilty! */
bail ("invalid connection to [%s] from %s [%s] %d",
cp, whozis->name, whozis->addrs[0], z);
holler ("connect to [%s] from %s [%s] %d", /* oh, you're okay.. */
cp, whozis->name, whozis->addrs[0], z);
return (nnetfd); /* open! */
dol_tmo:
errno = ETIMEDOUT; /* fake it */
dol_err:
#ifdef WIN32
shutdown(nnetfd, 0x02); /* Kirby */
closesocket (nnetfd);
#else
close (nnetfd);
#endif
return (-1);
} /* dolisten */
/* udptest :
fire a couple of packets at a UDP target port, just to see if it's really
there. On BSD kernels, ICMP host/port-unreachable errors get delivered to
our socket as ECONNREFUSED write errors. On SV kernels, we lose; we'll have
to collect and analyze raw ICMP ourselves a la satan's probe_udp_ports
backend. Guess where could swipe the appropriate code from...
Use the time delay between writes if given, otherwise use the "tcp ping"
trick for getting the RTT. [I got that idea from pluvius, and warped it.]
Return either the original fd, or clean up and return -1. */
udptest (fd, where)
int fd;
IA * where;
{
register int rr;
#ifdef WIN32
rr = send (fd, bigbuf_in, 1, 0);
#else
rr = write (fd, bigbuf_in, 1);
#endif
if (rr != 1)
holler ("udptest first write failed?! errno %d", errno);
if (o_wait)
sleep (o_wait);
else {
/* use the tcp-ping trick: try connecting to a normally refused port, which
causes us to block for the time that SYN gets there and RST gets back.
Not completely reliable, but it *does* mostly work. */
o_udpmode = 0; /* so doconnect does TCP this time */
/* Set a temporary connect timeout, so packet filtration doesnt cause
us to hang forever, and hit it */
o_wait = 5; /* XXX: enough to notice?? */
rr = doconnect (where, SLEAZE_PORT, 0, 0);
if (rr > 0)
#ifdef WIN32
shutdown(fd, 0x02); /* Kirby */
closesocket (rr);
#else
close (rr); /* in case it *did* open */
#endif
o_wait = 0; /* reset it */
o_udpmode++; /* we *are* still doing UDP, right? */
} /* if o_wait */
errno = 0; /* clear from sleep */
#ifdef WIN32
rr = send (fd, bigbuf_in, 1, 0);
#else
rr = write (fd, bigbuf_in, 1);
#endif
if (rr == 1) /* if write error, no UDP listener */
return (fd);
#ifdef WIN32
shutdown(fd, 0x02); /* Kirby */
closesocket (fd);
#else
close (fd); /* use it or lose it! */
#endif
return (-1);
} /* udptest */
/* oprint :
Hexdump bytes shoveled either way to a running logfile, in the format:
D offset - - - - --- 16 bytes --- - - - - # .... ascii .....
where "which" sets the direction indicator, D:
0 -- sent to network, or ">"
1 -- rcvd and printed to stdout, or "<"
and "buf" and "n" are data-block and length. If the current block generates
a partial line, so be it; we *want* that lockstep indication of who sent
what when. Adapted from dgaudet's original example -- but must be ripping
*fast*, since we don't want to be too disk-bound... */
void oprint (which, buf, n)
int which;
char * buf;
int n;
{
int bc; /* in buffer count */
int obc; /* current "global" offset */
int soc; /* stage write count */
register unsigned char * p; /* main buf ptr; m.b. unsigned here */
register unsigned char * op; /* out hexdump ptr */
register unsigned char * a; /* out asc-dump ptr */
register int x;
register unsigned int y;
if (! ofd)
bail ("oprint called with no open fd?!");
if (n == 0)
return;
op = stage;
if (which) {
*op = '<';
obc = wrote_out; /* use the globals! */
} else {
*op = '>';
obc = wrote_net;
}
op++; /* preload "direction" */
*op = ' ';
p = (unsigned char *) buf;
bc = n;
stage[59] = '#'; /* preload separator */
stage[60] = ' ';
while (bc) { /* for chunk-o-data ... */
x = 16;
soc = 78; /* len of whole formatted line */
if (bc < x) {
soc = soc - 16 + bc; /* fiddle for however much is left */
x = (bc * 3) + 11; /* 2 digits + space per, after D & offset */
op = &stage[x];
x = 16 - bc;
while (x) {
*op++ = ' '; /* preload filler spaces */
*op++ = ' ';
*op++ = ' ';
x--;
}
x = bc; /* re-fix current linecount */
} /* if bc < x */
bc -= x; /* fix wrt current line size */
sprintf (&stage[2], "%8.8x ", obc); /* xxx: still slow? */
obc += x; /* fix current offset */
op = &stage[11]; /* where hex starts */
a = &stage[61]; /* where ascii starts */
while (x) { /* for line of dump, however long ... */
y = (int)(*p >> 4); /* hi half */
*op = hexnibs[y];
op++;
y = (int)(*p & 0x0f); /* lo half */
*op = hexnibs[y];
op++;
*op = ' ';
op++;
if ((*p > 31) && (*p < 127))
*a = *p; /* printing */
else
*a = '.'; /* nonprinting, loose def */
a++;
p++;
x--;
} /* while x */
*a = '\n'; /* finish the line */
x = write (ofd, stage, soc);
if (x < 0)
bail ("ofd write err");
} /* while bc */
} /* oprint */
#ifdef TELNET
USHORT o_tn = 0; /* global -t option */
/* atelnet :
Answer anything that looks like telnet negotiation with don't/won't.
This doesn't modify any data buffers, update the global output count,
or show up in a hexdump -- it just shits into the outgoing stream.
Idea and codebase from Mudge@l0pht.com. */
void atelnet (buf, size)
unsigned char * buf; /* has to be unsigned here! */
unsigned int size;
{
static unsigned char obuf [4]; /* tiny thing to build responses into */
register int x;
register unsigned char y;
register unsigned char * p;
y = 0;
p = buf;
x = size;
while (x > 0) {
if (*p != 255) /* IAC? */
goto notiac;
obuf[0] = 255;
p++; x--;
if ((*p == 251) || (*p == 252)) /* WILL or WONT */
y = 254; /* -> DONT */
if ((*p == 253) || (*p == 254)) /* DO or DONT */
y = 252; /* -> WONT */
if (y) {
obuf[1] = y;
p++; x--;
obuf[2] = *p; /* copy actual option byte */
#ifdef WIN32
(void) send (netfd, obuf, 3, 0); /* one line, or the whole buffer */
#else
(void) write (netfd, obuf, 3);
#endif
/* if one wanted to bump wrote_net or do a hexdump line, here's the place */
y = 0;
} /* if y */
notiac:
p++; x--;
} /* while x */
} /* atelnet */
#endif /* TELNET */
/* readwrite :
handle stdin/stdout/network I/O. Bwahaha!! -- the select loop from hell.
In this instance, return what might become our exit status. */
int readwrite (fd)
#ifdef WIN32
unsigned int fd;
#else
int fd;
#endif
{
register int rr;
register char * zp; /* stdin buf ptr */
register char * np; /* net-in buf ptr */
unsigned int rzleft;
unsigned int rnleft;
USHORT netretry; /* net-read retry counter */
USHORT wretry; /* net-write sanity counter */
USHORT wfirst; /* one-shot flag to skip first net read */
#ifdef WIN32 /* (weld) WIN32 must poll because of weak stdin handling so we need a
short timer */
struct timeval timer3;
int istty;
time_t start, current;
int foo;
timer3.tv_sec = 0;
timer3.tv_usec = 1000;
/* save the time so we can bail when we reach timeout */
time( &start );
/* sets stdin and stdout to binary so no crlf translation if its a tty */
if (!_isatty( 1 ))
_setmode( 1, _O_BINARY );
if ((istty = _isatty( 0 )) == FALSE)
_setmode( 0, _O_BINARY ); /* (weld) I think we want to do this */
#endif
/* if you don't have all this FD_* macro hair in sys/types.h, you'll have to
either find it or do your own bit-bashing: *ding1 |= (1 << fd), etc... */
#ifndef WIN32 /* fd is not implemented as a real file handle in WIN32 */
if (fd > FD_SETSIZE) {
holler ("Preposterous fd value %d", fd);
return (1);
}
#endif
FD_SET (fd, ding1); /* global: the net is open */
netretry = 2;
wfirst = 0;
rzleft = rnleft = 0;
if (insaved) {
rzleft = insaved; /* preload multi-mode fakeouts */
zp = bigbuf_in;
wfirst = 1;
if (Single) /* if not scanning, this is a one-off first */
insaved = 0; /* buffer left over from argv construction, */
else {
FD_CLR (0, ding1); /* OR we've already got our repeat chunk, */
close (0); /* so we won't need any more stdin */
} /* Single */
} /* insaved */
if (o_interval)
sleep (o_interval); /* pause *before* sending stuff, too */
errno = 0; /* clear from sleep */
#ifdef WIN32
WSASetLastError(0);
#endif
/* and now the big ol' select shoveling loop ... */
while (FD_ISSET (fd, ding1)) { /* i.e. till the *net* closes! */
wretry = 8200; /* more than we'll ever hafta write */
if (wfirst) { /* any saved stdin buffer? */
wfirst = 0; /* clear flag for the duration */
goto shovel; /* and go handle it first */
}
*ding2 = *ding1; /* FD_COPY ain't portable... */
/* some systems, notably linux, crap into their select timers on return, so
we create a expendable copy and give *that* to select. *Fuck* me ... */
if (timer1)
memcpy (timer2, timer1, sizeof (struct timeval));
#ifdef WIN32 /* (weld)we must use our own small timeval to poll */
rr = select (16, ding2, 0, 0, &timer3); /* here it is, kiddies */
#else
rr = select (16, ding2, 0, 0, timer2); /* here it is, kiddies */
#endif
if (rr < 0) {
#ifdef WIN32
if (h_errno != WSAEINTR) { /* might have gotten ^Zed, etc ?*/
#else
if (errno != EINTR) { /* might have gotten ^Zed, etc ?*/
#endif
foo = h_errno;
holler ("select fuxored");
#ifdef WIN32
shutdown(fd, 0x02); /* Kirby */
closesocket (fd);
#else
close (fd);
#endif
return (1);
}
} /* select fuckup */
/* if we have a timeout AND stdin is closed AND we haven't heard anything
from the net during that time, assume it's dead and close it too. */
#ifndef WIN32 /* (weld) need to write some code here */
if (rr == 0) {
if (! FD_ISSET (0, ding1))
netretry--; /* we actually try a coupla times. */
if (! netretry) {
if (o_verbose > 1) /* normally we don't care */
holler ("net timeout");
close (fd);
return (0); /* not an error! */
}
} /* select timeout */
#else
if (rr == 0) {
time( &current );
if ( o_wait > 0 && (current - start) > timer1->tv_sec) {
if (o_verbose > 1) /* normally we don't care */
holler ("net timeout");
shutdown(fd, 0x02); /* Kirby */
closesocket (fd);
FD_ZERO(ding1);
WSASetLastError(0);
return (0); /* not an error! */
}
} /* select timeout */
#endif
/* xxx: should we check the exception fds too? The read fds seem to give
us the right info, and none of the examples I found bothered. */
/* Ding!! Something arrived, go check all the incoming hoppers, net first */
if (FD_ISSET (fd, ding2)) { /* net: ding! */
#ifdef WIN32
// reset timer
time( &start );
rr = recv (fd, bigbuf_net, BIGSIZ, 0);
#else
rr = read (fd, bigbuf_net, BIGSIZ);
#endif
if (rr <= 0) {
FD_CLR (fd, ding1); /* net closed, we'll finish up... */
rzleft = 0; /* can't write anymore: broken pipe */
} else {
rnleft = rr;
np = bigbuf_net;
#ifdef TELNET
if (o_tn)
atelnet (np, rr); /* fake out telnet stuff */
#endif /* TELNET */
} /* if rr */
Debug (("got %d from the net, errno %d", rr, errno))
} /* net:ding */
/* if we're in "slowly" mode there's probably still stuff in the stdin
buffer, so don't read unless we really need MORE INPUT! MORE INPUT! */
if (rzleft)
goto shovel;
/* okay, suck more stdin */
#ifndef WIN32
if (FD_ISSET (0, ding2)) { /* stdin: ding! */
rr = read (0, bigbuf_in, BIGSIZ);
/* xxx: maybe make reads here smaller for UDP mode, so that the subsequent
writes are smaller -- 1024 or something? "oh, frag it", etc, although
mobygrams are kinda fun and exercise the reassembler. */
if (rr <= 0) { /* at end, or fukt, or ... */
FD_CLR (0, ding1); /* disable and close stdin */
close (0);
} else {
rzleft = rr;
zp = bigbuf_in;
/* special case for multi-mode -- we'll want to send this one buffer to every
open TCP port or every UDP attempt, so save its size and clean up stdin */
if (! Single) { /* we might be scanning... */
insaved = rr; /* save len */
FD_CLR (0, ding1); /* disable further junk from stdin */
close (0); /* really, I mean it */
} /* Single */
} /* if rr/read */
} /* stdin:ding */
#else
if (istty) {
/* (weld) cool, we can actually peek a tty and not have to block */
/* needs to be cleaned up */
if (kbhit()) {
/* bigbuf_in[0] = getche(); */
gets(bigbuf_in);
if (o_crlf)
strcat(bigbuf_in, "\x0d");
strcat(bigbuf_in, "\x0a");
rr = strlen(bigbuf_in);
rzleft = rr;
zp = bigbuf_in;
/* special case for multi-mode -- we'll want to send this one buffer to every
open TCP port or every UDP attempt, so save its size and clean up stdin */
if (! Single) { /* we might be scanning... */
insaved = rr; /* save len */
close (0); /* really, I mean it */
}
}
} else {
/* (weld) this is gonna block until a <cr> so it kinda sucks */
rr = read (0, bigbuf_in, BIGSIZ);
if (rr <= 0) { /* at end, or fukt, or ... */
close (0);
} else {
rzleft = rr;
zp = bigbuf_in;
/* special case for multi-mode -- we'll want to send this one buffer to every
open TCP port or every UDP attempt, so save its size and clean up stdin */
if (! Single) { /* we might be scanning... */
insaved = rr; /* save len */
close (0); /* really, I mean it */
} /* Single */
} /* if rr/read */
}
#endif
shovel:
/* now that we've dingdonged all our thingdings, send off the results.
Geez, why does this look an awful lot like the big loop in "rsh"? ...
not sure if the order of this matters, but write net -> stdout first. */
/* sanity check. Works because they're both unsigned... */
if ((rzleft > 8200) || (rnleft > 8200)) {
holler ("Preposterous Pointers: %d, %d", rzleft, rnleft);
rzleft = rnleft = 0;
}
/* net write retries sometimes happen on UDP connections */
if (! wretry) { /* is something hung? */
holler ("too many output retries");
return (1);
}
if (rnleft) {
rr = write (1, np, rnleft);
fflush(stdin);
if (rr > 0) {
if (o_wfile)
oprint (1, np, rr); /* log the stdout */
np += rr; /* fix up ptrs and whatnot */
rnleft -= rr; /* will get sanity-checked above */
wrote_out += rr; /* global count */
}
Debug (("wrote %d to stdout, errno %d", rr, errno))
} /* rnleft */
if (rzleft) {
if (o_interval) /* in "slowly" mode ?? */
rr = findline (zp, rzleft);
else
rr = rzleft;
#ifdef WIN32
rr = send (fd, zp, rr, 0); /* one line, or the whole buffer */
#else
rr = write (fd, zp, rr); /* one line, or the whole buffer */
#endif
if (rr > 0) {
zp += rr;
rzleft -= rr;
wrote_net += rr; /* global count */
}
Debug (("wrote %d to net, errno %d", rr, errno))
} /* rzleft */
if (o_interval) { /* cycle between slow lines, or ... */
sleep (o_interval);
errno = 0; /* clear from sleep */
continue; /* ...with hairy select loop... */
}
if ((rzleft) || (rnleft)) { /* shovel that shit till they ain't */
wretry--; /* none left, and get another load */
goto shovel;
}
} /* while ding1:netfd is open */
/* XXX: maybe want a more graceful shutdown() here, or screw around with
linger times?? I suspect that I don't need to since I'm always doing
blocking reads and writes and my own manual "last ditch" efforts to read
the net again after a timeout. I haven't seen any screwups yet, but it's
not like my test network is particularly busy... */
#ifdef WIN32
shutdown(fd, 0x02); /* Kirby */
closesocket (fd);
#else
close (fd);
#endif
return (0);
} /* readwrite */
/* main :
now we pull it all together... */
main (argc, argv)
int argc;
char ** argv;
{
#ifndef HAVE_GETOPT
extern char * optarg;
extern int optind, optopt;
#endif
register int x;
register char *cp;
HINF * gp;
HINF * whereto = NULL;
HINF * wherefrom = NULL;
IA * ouraddr = NULL;
IA * themaddr = NULL;
USHORT o_lport = 0;
USHORT ourport = 0;
USHORT loport = 0; /* for scanning stuff */
USHORT hiport = 0;
USHORT curport = 0;
char * randports = NULL;
int cycle = 0;
#ifdef HAVE_BIND
/* can *you* say "cc -yaddayadda netcat.c -lresolv -l44bsd" on SunLOSs? */
res_init();
#endif
/* I was in this barbershop quartet in Skokie IL ... */
/* round up the usual suspects, i.e. malloc up all the stuff we need */
lclend = (SAI *) Hmalloc (sizeof (SA));
remend = (SAI *) Hmalloc (sizeof (SA));
bigbuf_in = Hmalloc (BIGSIZ);
bigbuf_net = Hmalloc (BIGSIZ);
ding1 = (fd_set *) Hmalloc (sizeof (fd_set));
ding2 = (fd_set *) Hmalloc (sizeof (fd_set));
portpoop = (PINF *) Hmalloc (sizeof (PINF));
#ifdef WIN32
setsockopt_c = (char *)malloc(sizeof(char));
*setsockopt_c = 1;
#endif
errno = 0;
gatesptr = 4;
#ifndef WIN32
h_errno = 0;
#endif
/* catch a signal or two for cleanup */
#ifdef NTFIXTHIS
signal (SIGINT, catch);
signal (SIGQUIT, catch);
signal (SIGTERM, catch);
signal (SIGURG, SIG_IGN);
#endif
recycle:
/* if no args given at all, get 'em from stdin and construct an argv. */
if (argc == 1) {
cp = argv[0];
argv = (char **) Hmalloc (128 * sizeof (char *)); /* XXX: 128? */
argv[0] = cp; /* leave old prog name intact */
cp = Hmalloc (BIGSIZ);
argv[1] = cp; /* head of new arg block */
fprintf (stderr, "Cmd line: ");
fflush (stderr); /* I dont care if it's unbuffered or not! */
insaved = read (0, cp, BIGSIZ); /* we're gonna fake fgets() here */
if (insaved <= 0)
bail ("wrong");
x = findline (cp, insaved);
if (x)
insaved -= x; /* remaining chunk size to be sent */
if (insaved) /* which might be zero... */
memcpy (bigbuf_in, &cp[x], insaved);
cp = strchr (argv[1], '\n');
if (cp)
*cp = '\0';
cp = strchr (argv[1], '\r'); /* look for ^M too */
if (cp)
*cp = '\0';
/* find and stash pointers to remaining new "args" */
cp = argv[1];
cp++; /* skip past first char */
x = 2; /* we know argv 0 and 1 already */
for (; *cp != '\0'; cp++) {
if (*cp == ' ') {
*cp = '\0'; /* smash all spaces */
continue;
} else {
if (*(cp-1) == '\0') {
argv[x] = cp;
x++;
}
} /* if space */
} /* for cp */
argc = x;
} /* if no args given */
/* If your shitbox doesn't have getopt, step into the nineties already. */
/* optarg, optind = next-argv-component [i.e. flag arg]; optopt = last-char */
while ((x = getopt (argc, argv, "ade:g:G:hi:lLno:p:rs:tcuvw:z")) != EOF) {
/* Debug (("in go: x now %c, optarg %x optind %d", x, optarg, optind)) */
switch (x) {
case 'a':
bail ("all-A-records NIY");
o_alla++; break;
#ifdef GAPING_SECURITY_HOLE
case 'e': /* prog to exec */
pr00gie = optarg;
break;
#endif
case 'L': /* listen then cycle back to start instead of exiting */
o_listen++;
cycle = 1;
break;
case 'd': /* detach from console */
FreeConsole();;
break;
case 'G': /* srcrt gateways pointer val */
x = atoi (optarg);
if ((x) && (x == (x & 0x1c))) /* mask off bits of fukt values */
gatesptr = x;
else
bail ("invalid hop pointer %d, must be multiple of 4 <= 28", x);
break;
case 'g': /* srcroute hop[s] */
if (gatesidx > 8)
bail ("too many -g hops");
if (gates == NULL) /* eat this, Billy-boy */
gates = (HINF **) Hmalloc (sizeof (HINF *) * 10);
gp = gethostpoop (optarg, o_nflag);
if (gp)
gates[gatesidx] = gp;
gatesidx++;
break;
case 'h':
errno = 0;
#ifdef HAVE_HELP
helpme(); /* exits by itself */
#else
bail ("no help available, dork -- RTFS");
#endif
case 'i': /* line-interval time */
o_interval = atoi (optarg) & 0xffff;
#ifdef WIN32
o_interval *= 1000;
#endif
if (! o_interval)
bail ("invalid interval time %s", optarg);
break;
case 'l': /* listen mode */
o_listen++; break;
case 'n': /* numeric-only, no DNS lookups */
o_nflag++; break;
case 'o': /* hexdump log */
stage = (unsigned char *) optarg;
o_wfile++; break;
case 'p': /* local source port */
o_lport = getportpoop (optarg, 0);
if (o_lport == 0)
bail ("invalid local port %s", optarg);
break;
case 'r': /* randomize various things */
o_random++; break;
case 's': /* local source address */
/* do a full lookup [since everything else goes through the same mill],
unless -n was previously specified. In fact, careful placement of -n can
be useful, so we'll still pass o_nflag here instead of forcing numeric. */
wherefrom = gethostpoop (optarg, o_nflag);
ouraddr = &wherefrom->iaddrs[0];
break;
#ifdef TELNET
case 't': /* do telnet fakeout */
o_tn++; break;
#endif /* TELNET */
case 'c': /* do telnet fakeout */
o_crlf++; break;
case 'u': /* use UDP */
o_udpmode++; break;
case 'v': /* verbose */
o_verbose++; break;
case 'w': /* wait time */
o_wait = atoi (optarg);
if (o_wait <= 0)
bail ("invalid wait-time %s", optarg);
timer1 = (struct timeval *) Hmalloc (sizeof (struct timeval));
timer2 = (struct timeval *) Hmalloc (sizeof (struct timeval));
timer1->tv_sec = o_wait; /* we need two. see readwrite()... */
break;
case 'z': /* little or no data xfer */
o_zero++;
break;
default:
errno = 0;
bail ("nc -h for help");
} /* switch x */
} /* while getopt */
/* other misc initialization */
#ifndef WIN32 /* Win32 doesn't like to mix file handles and sockets */
Debug (("fd_set size %d", sizeof (*ding1))) /* how big *is* it? */
FD_SET (0, ding1); /* stdin *is* initially open */
#endif
if (o_random) {
SRAND (time (0));
randports = Hmalloc (65536); /* big flag array for ports */
}
#ifdef GAPING_SECURITY_HOLE
if (pr00gie) {
close (0); /* won't need stdin */
o_wfile = 0; /* -o with -e is meaningless! */
ofd = 0;
}
#endif /* G_S_H */
if (o_wfile) {
ofd = open (stage, O_WRONLY | O_CREAT | O_TRUNC, 0664);
if (ofd <= 0) /* must be > extant 0/1/2 */
bail ("can't open %s", stage);
stage = (unsigned char *) Hmalloc (100);
}
/* optind is now index of first non -x arg */
Debug (("after go: x now %c, optarg %x optind %d", x, optarg, optind))
/* Debug (("optind up to %d at host-arg %s", optind, argv[optind])) */
/* gonna only use first addr of host-list, like our IQ was normal; if you wanna
get fancy with addresses, look up the list yourself and plug 'em in for now.
unless we finally implement -a, that is. */
if (argv[optind])
whereto = gethostpoop (argv[optind], o_nflag);
if (whereto && whereto->iaddrs)
themaddr = &whereto->iaddrs[0];
if (themaddr)
optind++; /* skip past valid host lookup */
errno = 0;
#ifndef WIN32
h_errno = 0;
#endif
/* Handle listen mode here, and exit afterward. Only does one connect;
this is arguably the right thing to do. A "persistent listen-and-fork"
mode a la inetd has been thought about, but not implemented. A tiny
wrapper script can handle such things... */
if (o_listen) {
curport = 0; /* rem port *can* be zero here... */
if (argv[optind]) { /* any rem-port-args? */
curport = getportpoop (argv[optind], 0);
if (curport == 0) /* if given, demand correctness */
bail ("invalid port %s", argv[optind]);
} /* if port-arg */
netfd = dolisten (themaddr, curport, ouraddr, o_lport);
/* dolisten does its own connect reporting, so we don't holler anything here */
if (netfd > 0) {
#ifdef GAPING_SECURITY_HOLE
if (pr00gie) /* -e given? */
doexec (netfd);
#ifdef WIN32
if (!pr00gie) // doexec does the read/write for win32
#endif
#endif /* GAPING_SECURITY_HOLE */
x = readwrite (netfd); /* it even works with UDP! */
if (o_verbose > 1) /* normally we don't care */
holler (wrote_txt, wrote_net, wrote_out);
if (cycle == 1)
goto recycle;
exit (x); /* "pack out yer trash" */
} else
bail ("no connection");
} /* o_listen */
/* fall thru to outbound connects. Now we're more picky about args... */
if (! themaddr)
bail ("no destination");
if (argv[optind] == NULL)
bail ("no port[s] to connect to");
if (argv[optind + 1]) /* look ahead: any more port args given? */
Single = 0; /* multi-mode, case A */
ourport = o_lport; /* which can be 0 */
/* everything from here down is treated as as ports and/or ranges thereof, so
it's all enclosed in this big ol' argv-parsin' loop. Any randomization is
done within each given *range*, but in separate chunks per each succeeding
argument, so we can control the pattern somewhat. */
while (argv[optind]) {
hiport = loport = 0;
cp = strchr (argv[optind], '-'); /* nn-mm range? */
if (cp) {
*cp = '\0';
cp++;
hiport = getportpoop (cp, 0);
if (hiport == 0)
bail ("invalid port %s", cp);
} /* if found a dash */
loport = getportpoop (argv[optind], 0);
if (loport == 0)
bail ("invalid port %s", argv[optind]);
if (hiport > loport) { /* was it genuinely a range? */
Single = 0; /* multi-mode, case B */
curport = hiport; /* start high by default */
if (o_random) { /* maybe populate the random array */
loadports (randports, loport, hiport);
curport = nextport (randports);
}
} else /* not a range, including args like "25-25" */
curport = loport;
Debug (("Single %d, curport %d", Single, curport))
/* Now start connecting to these things. curport is already preloaded. */
while (loport <= curport) {
if ((! o_lport) && (o_random)) { /* -p overrides random local-port */
ourport = (RAND() & 0xffff); /* random local-bind -- well above */
if (ourport < 8192) /* resv and any likely listeners??? */
ourport += 8192; /* xxx: may still conflict; use -s? */
}
curport = getportpoop (NULL, curport);
netfd = doconnect (themaddr, curport, ouraddr, ourport);
Debug (("netfd %d from port %d to port %d", netfd, ourport, curport))
if (netfd > 0)
if (o_zero && o_udpmode) /* if UDP scanning... */
netfd = udptest (netfd, themaddr);
if (netfd > 0) { /* Yow, are we OPEN YET?! */
x = 0; /* pre-exit status */
holler ("%s [%s] %d (%s) open",
whereto->name, whereto->addrs[0], curport, portpoop->name);
#ifdef GAPING_SECURITY_HOLE
if (pr00gie) /* exec is valid for outbound, too */
doexec (netfd);
#endif /* GAPING_SECURITY_HOLE */
if (! o_zero)
#ifdef WIN32
#ifdef GAPING_SECURITY_HOLE
if (!pr00gie) // doexec does the read/write for win32
#endif
#endif
x = readwrite (netfd); /* go shovel shit */
} else { /* no netfd... */
x = 1; /* preload exit status for later */
/* if we're scanning at a "one -v" verbosity level, don't print refusals.
Give it another -v if you want to see everything. */
#ifdef WIN32
if ((Single || (o_verbose > 1)) || (h_errno != WSAECONNREFUSED))
#else
if ((Single || (o_verbose > 1)) || (errno != ECONNREFUSED))
#endif
holler ("%s [%s] %d (%s)",
whereto->name, whereto->addrs[0], curport, portpoop->name);
} /* if netfd */
#ifdef WIN32
shutdown(netfd, 0x02); /* Kirby */
closesocket (netfd); /* just in case we didn't already */
#else
close (netfd); /* just in case we didn't already */
#endif
if (o_interval)
sleep (o_interval); /* if -i, delay between ports too */
if (o_random)
curport = nextport (randports);
else
curport--; /* just decrement... */
} /* while curport within current range */
optind++;
} /* while remaining port-args -- end of big argv-ports loop*/
errno = 0;
if (o_verbose > 1) /* normally we don't care */
holler ("sent %d, rcvd %d", wrote_net, wrote_out);
#ifdef WIN32
WSACleanup();
#endif
if (cycle == 1)
goto recycle;
if (Single)
exit (x); /* give us status on one connection */
exit (0); /* otherwise, we're just done */
return(0);
} /* main */
#ifdef HAVE_HELP /* unless we wanna be *really* cryptic */
/* helpme :
the obvious */
int helpme()
{
o_verbose = 1;
holler ("[v1.12 NT http://eternallybored.org/misc/netcat/]\n\
connect to somewhere: nc [-options] hostname port[s] [ports] ... \n\
listen for inbound: nc -l -p port [options] [hostname] [port]\n\
options:");
holler ("\
-d detach from console, background mode\n");
#ifdef GAPING_SECURITY_HOLE /* needs to be separate holler() */
holler ("\
-e prog inbound program to exec [dangerous!!]");
#endif
holler ("\
-g gateway source-routing hop point[s], up to 8\n\
-G num source-routing pointer: 4, 8, 12, ...\n\
-h this cruft\n\
-i secs delay interval for lines sent, ports scanned\n\
-l listen mode, for inbound connects\n\
-L listen harder, re-listen on socket close\n\
-n numeric-only IP addresses, no DNS\n\
-o file hex dump of traffic\n\
-p port local port number\n\
-r randomize local and remote ports\n\
-s addr local source address");
#ifdef TELNET
holler ("\
-t answer TELNET negotiation");
#endif
holler ("\
-c send CRLF instead of just LF\n\
-u UDP mode\n\
-v verbose [use twice to be more verbose]\n\
-w secs timeout for connects and final net reads\n\
-z zero-I/O mode [used for scanning]");
bail ("port numbers can be individual or ranges: m-n [inclusive]");
return(0);
} /* helpme */
#endif /* HAVE_HELP */
/* None genuine without this seal! _H*/
readme.txt 0 → 100644
View file @ fa87aa42
Update 2011-09-17 - added -c option to send CRLF
UPDATE 12/27/04 security fix in -e option for Windows
Netcat 1.11 for NT - nc111nt.zip
The original version of Netcat was written by *hobbit* <hobbit@avian.org>
The NT version was done by Weld Pond <weld@vulnwatch.org>
Netcat for NT is the tcp/ip "Swiss Army knife" that never made it into any
of the resource kits. It has proved to be an extremely versatile tool on
the unix platform. So why should NT always be unix's poor cousin when it
comes to tcp/ip testing and exploration? I bet many NT admins out there
keep a unix box around to use tools such as Netcat or to test their systems
with the unix version of an NT vulnerability exploit. With Netcat for NT
part of that feeling disempowerment is over.
Included with this release is Hobbit's original description of the powers
of Netcat. In this document I will briefly describe some of the things an
NT admin might want to do and know about with Netcat on NT. For more
detailed technical information please read hobbit.txt included in the
nc11nt.zip archive.
Basic Features
* Outbound or inbound connections, TCP or UDP, to or from any ports
* Full DNS forward/reverse checking, with appropriate warnings
* Ability to use any local source port
* Ability to use any locally-configured network source address
* Built-in port-scanning capabilities, with randomizer
* Can read command line arguments from standard input
* Slow-send mode, one line every N seconds
* Hex dump of transmitted and received data
* Ability to let another program service established
connections
* Telnet-options responder
New for NT
* Ability to run in the background without a console window
* Ability to restart as a single-threaded server to handle a new
connection
A simple example of using Netcat is to pull down a web page from a web
server. With Netcat you get to see the full HTTP header so you can see
which web server a particular site is running.
Since NT has a rather anemic command processor, some of the things that are
easy in unix may be a bit more clunky in NT. For the web page example first
create a file get.txt that contains the following line and then a blank
line:
GET / HTTP/1.0
To use Netcat to retrieve the home page of a web site use the command:
nc -v www.website.com 80 < get.txt
You will see Netcat make a connection to port 80, send the text contained
in the file get.txt, and then output the web server's response to stdout.
The -v is for verbose. It tells you a little info about the connection
when it starts.
It is a bit easier to just open the connection and then type at the console
to do the same thing.
nc -v www.website.com 80
Then just type in GET / HTTP/1.0 and hit a couple of returns. You will
see the same thing as above.
A far more exciting thing to do is to get a quick shell going on a remote
machine by using the -l or "listen" option and the -e or "execute"
option. You run Netcat listening on particular port for a connection.
When a connection is made, Netcat executes the program of your choice
and connects the stdin and stdout of the program to the network connection.
nc -l -p 23 -t -e cmd.exe
will get Netcat listening on port 23 (telnet). When it gets connected to
by a client it will spawn a shell (cmd.exe). The -t option tells Netcat
to handle any telnet negotiation the client might expect.
This will allow you to telnet to the machine you have Netcat listening on
and get a cmd.exe shell when you connect. You could just as well use
Netcat instead of telnet:
nc xxx.xxx.xxx.xxx 23
will get the job done. There is no authentication on the listening side
so be a bit careful here. The shell is running with the permissions of the
process that started Netcat so be very careful. If you were to use the
AT program to schedule Netcat to run listening on a port with the
-e cmd.exe option, when you connected you would get a shell with user
NT AUTHORITY\SYSTEM.
The beauty of Netcat really shines when you realize that you can get it
listening on ANY port doing the same thing. Do a little exploring and
see if the firewall you may be behind lets port 53 through. Run Netcat
listening behind the firewall on port 53.
nc -L -p 53 -e cmd.exe
Then from outside the firewall connect to the listening machine:
nc -v xxx.xxx.xxx.xx 53
If you get a command prompt then you are executing commands on the
listening machine. Use 'exit' at the command prompt for a clean
disconnect. The -L (note the capital L) option will restart Netcat with
the same command line when the connection is terminated. This way you can
connect over and over to the same Netcat process.
A new feature for the NT version is the -d or detach from console flag.
This will let Netcat run without an ugly console window cluttering up the
screen or showing up in the task list.
You can even get Netcat to listen on the NETBIOS ports that are probably
running on most NT machines. This way you can get a connection to a
machine that may have port filtering enabled in the TCP/IP Security Network
control panel. Unlike Unix, NT does not seem to have any security around
which ports that user programs are allowed to bind to. This means any
user can run a program that will bind to the NETBIOS ports.
You will need to bind "in front of" some services that may already be
listening on those ports. An example is the NETBIOS Session Service that
is running on port 139 of NT machines that are sharing files. You need
to bind to a specific source address (one of the IP addresses of the
machine) to accomplish this. This gives Netcat priority over the NETBIOS
service which is at a lower priority because it is bound to ANY IP address.
This is done with the Netcat -s option:
nc -v -L -e cmd.exe -p 139 -s xxx.xxx.xxx.xxx
Now you can connect to the machine on port 139 and Netcat will field
the connection before NETBIOS does. You have effectively shut off
file sharing on this machine by the way. You have done this with just
user privileges to boot.
PROBLEMS with Netcat 1.1 for NT
There are a few known problems that will eventually be fixed. One is
the -w or timeout option. This works for final net reads but not
for connections. Another problem is using the -e option in UDP mode.
You may find that some of the features work on Windows 95. Most
of the listening features will not work on Windows 95 however. These will
be fixed in a later release.
Netcat is distributed with full source code so that people can build
upon this work. If you add something useful or discover something
interesting about NT TCP/IP let met know.
Weld Pond <weld@l0pht.com>, 2/2/98
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