/* Copyright (C) 1996-2018 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>
and Paul Janzen <pcj@primenet.com>, 1996.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <utmp.h>
#include <not-cancel.h>
#include <kernel-features.h>
#include <sigsetops.h>
#include <not-cancel.h>
#include "utmp-private.h"
#include "utmp-equal.h"
/* Descriptor for the file and position. */
static int file_fd = -1;
static bool file_writable;
static off64_t file_offset;
/* Cache for the last read entry. */
static struct utmp last_entry;
/* Locking timeout. */
#ifndef TIMEOUT
# define TIMEOUT 10
#endif
/* Do-nothing handler for locking timeout. */
static void timeout_handler (int signum) {};
/* LOCK_FILE(fd, type) failure_statement
attempts to get a lock on the utmp file referenced by FD. If it fails,
the failure_statement is executed, otherwise it is skipped.
LOCKING_FAILED()
jumps into the UNLOCK_FILE macro and ensures cleanup of LOCK_FILE.
UNLOCK_FILE(fd)
unlocks the utmp file referenced by FD and performs the cleanup of
LOCK_FILE.
*/
#define LOCK_FILE(fd, type) \
{ \
struct flock fl; \
struct sigaction action, old_action; \
unsigned int old_timeout; \
\
/* Cancel any existing alarm. */ \
old_timeout = alarm (0); \
\
/* Establish signal handler. */ \
action.sa_handler = timeout_handler; \
__sigemptyset (&action.sa_mask); \
action.sa_flags = 0; \
__sigaction (SIGALRM, &action, &old_action); \
\
alarm (TIMEOUT); \
\
/* Try to get the lock. */ \
memset (&fl, '\0', sizeof (struct flock)); \
fl.l_type = (type); \
fl.l_whence = SEEK_SET; \
if (__fcntl64_nocancel ((fd), F_SETLKW, &fl) < 0)
#define LOCKING_FAILED() \
goto unalarm_return
#define UNLOCK_FILE(fd) \
/* Unlock the file. */ \
fl.l_type = F_UNLCK; \
__fcntl64_nocancel ((fd), F_SETLKW, &fl); \
\
unalarm_return: \
/* Reset the signal handler and alarm. We must reset the alarm \
before resetting the handler so our alarm does not generate a \
spurious SIGALRM seen by the user. However, we cannot just set \
the user's old alarm before restoring the handler, because then \
it's possible our handler could catch the user alarm's SIGARLM \
and then the user would never see the signal he expected. */ \
alarm (0); \
__sigaction (SIGALRM, &old_action, NULL); \
if (old_timeout != 0) \
alarm (old_timeout); \
} while (0)
/* Functions defined here. */
static int setutent_file (void);
static int getutent_r_file (struct utmp *buffer, struct utmp **result);
static int getutid_r_file (const struct utmp *key, struct utmp *buffer,
struct utmp **result);
static int getutline_r_file (const struct utmp *key, struct utmp *buffer,
struct utmp **result);
static struct utmp *pututline_file (const struct utmp *data);
static void endutent_file (void);
static int updwtmp_file (const char *file, const struct utmp *utmp);
/* Jump table for file functions. */
const struct utfuncs __libc_utmp_file_functions =
{
setutent_file,
getutent_r_file,
getutid_r_file,
getutline_r_file,
pututline_file,
endutent_file,
updwtmp_file
};
#ifndef TRANSFORM_UTMP_FILE_NAME
# define TRANSFORM_UTMP_FILE_NAME(file_name) (file_name)
#endif
static int
setutent_file (void)
{
if (file_fd < 0)
{
const char *file_name;
file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name);
file_writable = false;
file_fd = __open_nocancel
(file_name, O_RDONLY | O_LARGEFILE | O_CLOEXEC);
if (file_fd == -1)
return 0;
}
__lseek64 (file_fd, 0, SEEK_SET);
file_offset = 0;
/* Make sure the entry won't match. */
#if _HAVE_UT_TYPE - 0
last_entry.ut_type = -1;
#else
last_entry.ut_line[0] = '\177';
# if _HAVE_UT_ID - 0
last_entry.ut_id[0] = '\0';
# endif
#endif
return 1;
}
static int
getutent_r_file (struct utmp *buffer, struct utmp **result)
{
ssize_t nbytes;
assert (file_fd >= 0);
if (file_offset == -1l)
{
/* Not available. */
*result = NULL;
return -1;
}
LOCK_FILE (file_fd, F_RDLCK)
{
nbytes = 0;
LOCKING_FAILED ();
}
/* Read the next entry. */
nbytes = __read_nocancel (file_fd, &last_entry, sizeof (struct utmp));
UNLOCK_FILE (file_fd);
if (nbytes != sizeof (struct utmp))
{
if (nbytes != 0)
file_offset = -1l;
*result = NULL;
return -1;
}
/* Update position pointer. */
file_offset += sizeof (struct utmp);
memcpy (buffer, &last_entry, sizeof (struct utmp));
*result = buffer;
return 0;
}
static int
internal_getut_r (const struct utmp *id, struct utmp *buffer,
bool *lock_failed)
{
int result = -1;
LOCK_FILE (file_fd, F_RDLCK)
{
*lock_failed = true;
LOCKING_FAILED ();
}
#if _HAVE_UT_TYPE - 0
if (id->ut_type == RUN_LVL || id->ut_type == BOOT_TIME
|| id->ut_type == OLD_TIME || id->ut_type == NEW_TIME)
{
/* Search for next entry with type RUN_LVL, BOOT_TIME,
OLD_TIME, or NEW_TIME. */
while (1)
{
/* Read the next entry. */
if (__read_nocancel (file_fd, buffer, sizeof (struct utmp))
!= sizeof (struct utmp))
{
__set_errno (ESRCH);
file_offset = -1l;
goto unlock_return;
}
file_offset += sizeof (struct utmp);
if (id->ut_type == buffer->ut_type)
break;
}
}
else
#endif /* _HAVE_UT_TYPE */
{
/* Search for the next entry with the specified ID and with type
INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS. */
while (1)
{
/* Read the next entry. */
if (__read_nocancel (file_fd, buffer, sizeof (struct utmp))
!= sizeof (struct utmp))
{
__set_errno (ESRCH);
file_offset = -1l;
goto unlock_return;
}
file_offset += sizeof (struct utmp);
if (__utmp_equal (buffer, id))
break;
}
}
result = 0;
unlock_return:
UNLOCK_FILE (file_fd);
return result;
}
/* For implementing this function we don't use the getutent_r function
because we can avoid the reposition on every new entry this way. */
static int
getutid_r_file (const struct utmp *id, struct utmp *buffer,
struct utmp **result)
{
assert (file_fd >= 0);
if (file_offset == -1l)
{
*result = NULL;
return -1;
}
/* We don't have to distinguish whether we can lock the file or
whether there is no entry. */
bool lock_failed = false;
if (internal_getut_r (id, &last_entry, &lock_failed) < 0)
{
*result = NULL;
return -1;
}
memcpy (buffer, &last_entry, sizeof (struct utmp));
*result = buffer;
return 0;
}
/* For implementing this function we don't use the getutent_r function
because we can avoid the reposition on every new entry this way. */
static int
getutline_r_file (const struct utmp *line, struct utmp *buffer,
struct utmp **result)
{
assert (file_fd >= 0);
if (file_offset == -1l)
{
*result = NULL;
return -1;
}
LOCK_FILE (file_fd, F_RDLCK)
{
*result = NULL;
LOCKING_FAILED ();
}
while (1)
{
/* Read the next entry. */
if (__read_nocancel (file_fd, &last_entry, sizeof (struct utmp))
!= sizeof (struct utmp))
{
__set_errno (ESRCH);
file_offset = -1l;
*result = NULL;
goto unlock_return;
}
file_offset += sizeof (struct utmp);
/* Stop if we found a user or login entry. */
if (
#if _HAVE_UT_TYPE - 0
(last_entry.ut_type == USER_PROCESS
|| last_entry.ut_type == LOGIN_PROCESS)
&&
#endif
!strncmp (line->ut_line, last_entry.ut_line, sizeof line->ut_line))
break;
}
memcpy (buffer, &last_entry, sizeof (struct utmp));
*result = buffer;
unlock_return:
UNLOCK_FILE (file_fd);
return ((*result == NULL) ? -1 : 0);
}
static struct utmp *
pututline_file (const struct utmp *data)
{
struct utmp buffer;
struct utmp *pbuf;
int found;
assert (file_fd >= 0);
if (! file_writable)
{
/* We must make the file descriptor writable before going on. */
const char *file_name = TRANSFORM_UTMP_FILE_NAME (__libc_utmp_file_name);
int new_fd = __open_nocancel
(file_name, O_RDWR | O_LARGEFILE | O_CLOEXEC);
if (new_fd == -1)
return NULL;
if (__lseek64 (new_fd, __lseek64 (file_fd, 0, SEEK_CUR), SEEK_SET) == -1
|| __dup2 (new_fd, file_fd) < 0)
{
__close_nocancel_nostatus (new_fd);
return NULL;
}
__close_nocancel_nostatus (new_fd);
file_writable = true;
}
/* Find the correct place to insert the data. */
if (file_offset > 0
&& (
#if _HAVE_UT_TYPE - 0
(last_entry.ut_type == data->ut_type
&& (last_entry.ut_type == RUN_LVL
|| last_entry.ut_type == BOOT_TIME
|| last_entry.ut_type == OLD_TIME
|| last_entry.ut_type == NEW_TIME))
||
#endif
__utmp_equal (&last_entry, data)))
found = 1;
else
{
bool lock_failed = false;
found = internal_getut_r (data, &buffer, &lock_failed);
if (__builtin_expect (lock_failed, false))
{
__set_errno (EAGAIN);
return NULL;
}
}
LOCK_FILE (file_fd, F_WRLCK)
{
pbuf = NULL;
LOCKING_FAILED ();
}
if (found < 0)
{
/* We append the next entry. */
file_offset = __lseek64 (file_fd, 0, SEEK_END);
if (file_offset % sizeof (struct utmp) != 0)
{
file_offset -= file_offset % sizeof (struct utmp);
__ftruncate64 (file_fd, file_offset);
if (__lseek64 (file_fd, 0, SEEK_END) < 0)
{
pbuf = NULL;
goto unlock_return;
}
}
}
else
{
/* We replace the just read entry. */
file_offset -= sizeof (struct utmp);
__lseek64 (file_fd, file_offset, SEEK_SET);
}
/* Write the new data. */
if (__write_nocancel (file_fd, data, sizeof (struct utmp))
!= sizeof (struct utmp))
{
/* If we appended a new record this is only partially written.
Remove it. */
if (found < 0)
(void) __ftruncate64 (file_fd, file_offset);
pbuf = NULL;
}
else
{
file_offset += sizeof (struct utmp);
pbuf = (struct utmp *) data;
}
unlock_return:
UNLOCK_FILE (file_fd);
return pbuf;
}
static void
endutent_file (void)
{
assert (file_fd >= 0);
__close_nocancel_nostatus (file_fd);
file_fd = -1;
}
static int
updwtmp_file (const char *file, const struct utmp *utmp)
{
int result = -1;
off64_t offset;
int fd;
/* Open WTMP file. */
fd = __open_nocancel (file, O_WRONLY | O_LARGEFILE);
if (fd < 0)
return -1;
LOCK_FILE (fd, F_WRLCK)
LOCKING_FAILED ();
/* Remember original size of log file. */
offset = __lseek64 (fd, 0, SEEK_END);
if (offset % sizeof (struct utmp) != 0)
{
offset -= offset % sizeof (struct utmp);
__ftruncate64 (fd, offset);
if (__lseek64 (fd, 0, SEEK_END) < 0)
goto unlock_return;
}
/* Write the entry. If we can't write all the bytes, reset the file
size back to the original size. That way, no partial entries
will remain. */
if (__write_nocancel (fd, utmp, sizeof (struct utmp))
!= sizeof (struct utmp))
{
__ftruncate64 (fd, offset);
goto unlock_return;
}
result = 0;
unlock_return:
UNLOCK_FILE (fd);
/* Close WTMP file. */
__close_nocancel_nostatus (fd);
return result;
}