shadow/libmisc/utmp.c
nekral-guest a324a7f13f * NEWS, libmisc/chowntty.c, libmisc/utmp.c: is_my_tty() moved from
utmp.c to chowntty.c. checkutmp() now only uses an existing utmp
	entry if the pid matches and ut_line matches with the current tty.
	This fixes a possible DOS when entries can be forged in the utmp
	file.
	* libmisc/chowntty.c, src/login.c, lib/prototypes.h: Remove the
	tty argument from chown_tty. chown_tty always changes stdin and
	does not need this argument anymore.
2008-11-22 23:56:11 +00:00

445 lines
10 KiB
C

/*
* Copyright (c) 1989 - 1994, Julianne Frances Haugh
* Copyright (c) 1996 - 1999, Marek Michałkiewicz
* Copyright (c) 2001 - 2005, Tomasz Kłoczko
* Copyright (c) 2008 , Nicolas François
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the copyright holders or contributors may not be used to
* endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <config.h>
#include "defines.h"
#include "prototypes.h"
#include <utmp.h>
#if HAVE_UTMPX_H
#include <utmpx.h>
#endif
#include <fcntl.h>
#include <stdio.h>
#ident "$Id$"
#if HAVE_UTMPX_H
struct utmpx utxent;
#endif
struct utmp utent;
#define NO_UTENT \
_("No utmp entry. You must exec \"login\" from the lowest level \"sh\"")
#define NO_TTY \
_("Unable to determine your tty name.")
/*
* is_my_tty -- determine if "tty" is the same TTY stdin is using
*/
static bool is_my_tty (const char *tty)
{
char full_tty[200];
struct stat by_name, by_fd;
if ('/' != *tty) {
snprintf (full_tty, sizeof full_tty, "/dev/%s", tty);
tty = full_tty;
}
if ( (stat (tty, &by_name) != 0)
|| (fstat (STDIN_FILENO, &by_fd) != 0)) {
return false;
}
if (by_name.st_rdev != by_fd.st_rdev) {
return false;
} else {
return true;
}
}
/*
* checkutmp - see if utmp file is correct for this process
*
* System V is very picky about the contents of the utmp file
* and requires that a slot for the current process exist.
* The utmp file is scanned for an entry with the same process
* ID. If no entry exists the process exits with a message.
*
* The "picky" flag is for network and other logins that may
* use special flags. It allows the pid checks to be overridden.
* This means that getty should never invoke login with any
* command line flags.
*/
#if defined(__linux__) /* XXX */
void checkutmp (bool picky)
{
char *line;
struct utmp *ut;
pid_t pid = getpid ();
setutent ();
/* First, try to find a valid utmp entry for this process. */
while ((ut = getutent ()) != NULL) {
if ( (ut->ut_pid == pid)
&& ('\0' != ut->ut_line[0])
&& ('\0' != ut->ut_id[0])
&& ( (LOGIN_PROCESS == ut->ut_type)
|| (USER_PROCESS == ut->ut_type))
/* A process may have failed to close an entry
* Check if this entry refers to this tty */
&& is_my_tty (ut->ut_line)) {
break;
}
}
/* If there is one, just use it, otherwise create a new one. */
if (NULL != ut) {
utent = *ut;
} else {
if (picky) {
(void) puts (NO_UTENT);
exit (EXIT_FAILURE);
}
line = ttyname (0);
if (NULL == line) {
(void) puts (NO_TTY);
exit (EXIT_FAILURE);
}
if (strncmp (line, "/dev/", 5) == 0) {
line += 5;
}
memset ((void *) &utent, 0, sizeof utent);
utent.ut_type = LOGIN_PROCESS;
utent.ut_pid = pid;
strncpy (utent.ut_line, line, sizeof utent.ut_line);
/* XXX - assumes /dev/tty?? or /dev/pts/?? */
strncpy (utent.ut_id, utent.ut_line + 3, sizeof utent.ut_id);
strcpy (utent.ut_user, "LOGIN");
utent.ut_time = time (NULL);
}
}
#elif defined(LOGIN_PROCESS)
void checkutmp (bool picky)
{
char *line;
struct utmp *ut;
#if HAVE_UTMPX_H
struct utmpx *utx;
#endif
pid_t pid = getpid ();
#if HAVE_UTMPX_H
setutxent ();
#endif
setutent ();
if (picky) {
#if HAVE_UTMPX_H
while ((utx = getutxent ()) != NULL) {
if (utx->ut_pid == pid) {
break;
}
}
if (NULL != utx) {
utxent = *utx;
}
#endif
while ((ut = getutent ()) != NULL) {
if (ut->ut_pid == pid) {
break;
}
}
if (NULL != ut) {
utent = *ut;
}
#if HAVE_UTMPX_H
endutxent ();
#endif
endutent ();
if (NULL == ut) {
(void) puts (NO_UTENT);
exit (EXIT_FAILURE);
}
#ifndef UNIXPC
/*
* If there is no ut_line value in this record, fill
* it in by getting the TTY name and stuffing it in
* the structure. The UNIX/PC is broken in this regard
* and needs help ...
*/
/* XXX: The ut_line may not match with the current tty.
* ut_line will be set by setutmp anyway, but ut_id
* will not be set, and the wrong utmp entry may be
* updated. -- nekral */
if (utent.ut_line[0] == '\0')
#endif /* !UNIXPC */
{
line = ttyname (0);
if (NULL == line) {
(void) puts (NO_TTY);
exit (EXIT_FAILURE);
}
if (strncmp (line, "/dev/", 5) == 0) {
line += 5;
}
strncpy (utent.ut_line, line, sizeof utent.ut_line);
#if HAVE_UTMPX_H
strncpy (utxent.ut_line, line, sizeof utxent.ut_line);
#endif
}
} else {
line = ttyname (0);
if (NULL == line) {
(void) puts (NO_TTY);
exit (EXIT_FAILURE);
}
if (strncmp (line, "/dev/", 5) == 0) {
line += 5;
}
strncpy (utent.ut_line, line, sizeof utent.ut_line);
ut = getutline (&utent);
if (NULL != ut) {
strncpy (utent.ut_id, ut->ut_id, sizeof ut->ut_id);
}
strcpy (utent.ut_user, "LOGIN");
utent.ut_pid = getpid ();
utent.ut_type = LOGIN_PROCESS;
utent.ut_time = time (NULL);
#if HAVE_UTMPX_H
strncpy (utxent.ut_line, line, sizeof utxent.ut_line);
utx = getutxline (&utxent);
if (NULL != utx) {
strncpy (utxent.ut_id, utx->ut_id, sizeof utxent.ut_id);
}
strcpy (utxent.ut_user, "LOGIN");
utxent.ut_pid = utent.ut_pid;
utxent.ut_type = utent.ut_type;
if (sizeof (utxent.ut_tv) == sizeof (struct timeval)) {
gettimeofday ((struct timeval *) &utxent.ut_tv, NULL);
} else {
struct timeval tv;
gettimeofday (&tv, NULL);
utxent.ut_tv.tv_sec = tv.tv_sec;
utxent.ut_tv.tv_usec = tv.tv_usec;
}
utent.ut_time = utxent.ut_tv.tv_sec;
#endif
}
}
#endif
/*
* Some systems already have updwtmp() and possibly updwtmpx(). Others
* don't, so we re-implement these functions if necessary. --marekm
*/
#ifndef HAVE_UPDWTMP
static void updwtmp (const char *filename, const struct utmp *ut)
{
int fd;
fd = open (filename, O_APPEND | O_WRONLY, 0);
if (fd >= 0) {
write (fd, (const char *) ut, sizeof (*ut));
close (fd);
}
}
#endif /* ! HAVE_UPDWTMP */
#ifdef HAVE_UTMPX_H
#ifndef HAVE_UPDWTMPX
static void updwtmpx (const char *filename, const struct utmpx *utx)
{
int fd;
fd = open (filename, O_APPEND | O_WRONLY, 0);
if (fd >= 0) {
write (fd, (const char *) utx, sizeof (*utx));
close (fd);
}
}
#endif /* ! HAVE_UPDWTMPX */
#endif /* ! HAVE_UTMPX_H */
/*
* setutmp - put a USER_PROCESS entry in the utmp file
*
* setutmp changes the type of the current utmp entry to
* USER_PROCESS. the wtmp file will be updated as well.
*/
#if defined(__linux__) /* XXX */
int setutmp (const char *name, const char unused(*line), const char unused(*host))
{
int err = 0;
utent.ut_type = USER_PROCESS;
strncpy (utent.ut_user, name, sizeof utent.ut_user);
utent.ut_time = time (NULL);
/* other fields already filled in by checkutmp above */
setutent ();
if (pututline (&utent) == NULL) {
err = 1;
}
endutent ();
updwtmp (_WTMP_FILE, &utent);
return err;
}
#elif HAVE_UTMPX_H
int setutmp (const char *name, const char *line, const char *host)
{
struct utmp *utmp, utline;
struct utmpx *utmpx, utxline;
pid_t pid = getpid ();
bool found_utmpx = false;
bool found_utmp = false;
int err = 0;
/*
* The canonical device name doesn't include "/dev/"; skip it
* if it is already there.
*/
if (strncmp (line, "/dev/", 5) == 0) {
line += 5;
}
/*
* Update utmpx. We create an empty entry in case there is
* no matching entry in the utmpx file.
*/
setutxent ();
setutent ();
while ((utmpx = getutxent ()) != NULL) {
if (utmpx->ut_pid == pid) {
found_utmpx = true;
break;
}
}
while ((utmp = getutent ()) != NULL) {
if (utmp->ut_pid == pid) {
found_utmp = true;
break;
}
}
/*
* If the entry matching `pid' cannot be found, create a new
* entry with the device name in it.
*/
if (!found_utmpx) {
memset ((void *) &utxline, 0, sizeof utxline);
strncpy (utxline.ut_line, line, sizeof utxline.ut_line);
utxline.ut_pid = getpid ();
} else {
utxline = *utmpx;
if (strncmp (utxline.ut_line, "/dev/", 5) == 0) {
memmove (utxline.ut_line, utxline.ut_line + 5,
sizeof utxline.ut_line - 5);
utxline.ut_line[sizeof utxline.ut_line - 5] = '\0';
}
}
if (!found_utmp) {
memset ((void *) &utline, 0, sizeof utline);
strncpy (utline.ut_line, utxline.ut_line,
sizeof utline.ut_line);
utline.ut_pid = utxline.ut_pid;
} else {
utline = *utmp;
if (strncmp (utline.ut_line, "/dev/", 5) == 0) {
memmove (utline.ut_line, utline.ut_line + 5,
sizeof utline.ut_line - 5);
utline.ut_line[sizeof utline.ut_line - 5] = '\0';
}
}
/*
* Fill in the fields in the utmpx entry and write it out. Do
* the utmp entry at the same time to make sure things don't
* get messed up.
*/
strncpy (utxline.ut_user, name, sizeof utxline.ut_user);
strncpy (utline.ut_user, name, sizeof utline.ut_user);
utline.ut_type = utxline.ut_type = USER_PROCESS;
if (sizeof (utxline.ut_tv) == sizeof (struct timeval)) {
gettimeofday ((struct timeval *) &utxline.ut_tv, NULL);
} else {
struct timeval tv;
gettimeofday (&tv, NULL);
utxline.ut_tv.tv_sec = tv.tv_sec;
utxline.ut_tv.tv_usec = tv.tv_usec;
}
utline.ut_time = utxline.ut_tv.tv_sec;
strncpy (utxline.ut_host, (NULL != host) ? host : "",
sizeof utxline.ut_host);
if ( (pututxline (&utxline) == NULL)
|| (pututline (&utline) == NULL)) {
err = 1;
}
updwtmpx (_WTMP_FILE "x", &utxline);
updwtmp (_WTMP_FILE, &utline);
utxent = utxline;
utent = utline;
return err;
}
#endif