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freebsd/lib/libc/gen/pututxline.c
Jilles Tjoelker 05eb11cbc4 libc: Use O_CLOEXEC for various internal file descriptors.
This fixes a race condition where another thread may fork() before CLOEXEC
is set, unintentionally passing the descriptor to the child process.

This commit only adds O_CLOEXEC flags to open() or openat() calls where no
fcntl(fd, F_SETFD, FD_CLOEXEC) follows. The separate fcntl() call still
leaves a race window so it should be fixed later.
2012-09-29 11:54:34 +00:00

332 lines
7.2 KiB
C

/*-
* Copyright (c) 2010 Ed Schouten <ed@FreeBSD.org>
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "namespace.h"
#include <sys/endian.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <utmpx.h>
#include "utxdb.h"
#include "un-namespace.h"
static FILE *
futx_open(const char *file)
{
FILE *fp;
struct stat sb;
int fd;
fd = _open(file, O_CREAT|O_RDWR|O_EXLOCK|O_CLOEXEC, 0644);
if (fd < 0)
return (NULL);
/* Safety check: never use broken files. */
if (_fstat(fd, &sb) != -1 && sb.st_size % sizeof(struct futx) != 0) {
_close(fd);
errno = EFTYPE;
return (NULL);
}
fp = fdopen(fd, "r+");
if (fp == NULL) {
_close(fd);
return (NULL);
}
return (fp);
}
static int
utx_active_add(const struct futx *fu)
{
FILE *fp;
struct futx fe;
off_t partial;
int error, ret;
partial = -1;
ret = 0;
/*
* Register user login sessions. Overwrite entries of sessions
* that have already been terminated.
*/
fp = futx_open(_PATH_UTX_ACTIVE);
if (fp == NULL)
return (-1);
while (fread(&fe, sizeof(fe), 1, fp) == 1) {
switch (fe.fu_type) {
case BOOT_TIME:
/* Leave these intact. */
break;
case USER_PROCESS:
case INIT_PROCESS:
case LOGIN_PROCESS:
case DEAD_PROCESS:
/* Overwrite when ut_id matches. */
if (memcmp(fu->fu_id, fe.fu_id, sizeof(fe.fu_id)) ==
0) {
ret = fseeko(fp, -(off_t)sizeof(fe), SEEK_CUR);
goto exact;
}
if (fe.fu_type != DEAD_PROCESS)
break;
/* FALLTHROUGH */
default:
/* Allow us to overwrite unused records. */
if (partial == -1) {
partial = ftello(fp);
/*
* Distinguish errors from valid values so we
* don't overwrite good data by accident.
*/
if (partial != -1)
partial -= (off_t)sizeof(fe);
}
break;
}
}
/*
* No exact match found. Use the partial match. If no partial
* match was found, just append a new record.
*/
if (partial != -1)
ret = fseeko(fp, partial, SEEK_SET);
exact:
if (ret == -1)
error = errno;
else if (fwrite(fu, sizeof(*fu), 1, fp) < 1)
error = errno;
else
error = 0;
fclose(fp);
errno = error;
return (error == 0 ? 0 : 1);
}
static int
utx_active_remove(struct futx *fu)
{
FILE *fp;
struct futx fe;
int error, ret;
/*
* Remove user login sessions, having the same ut_id.
*/
fp = futx_open(_PATH_UTX_ACTIVE);
if (fp == NULL)
return (-1);
error = ESRCH;
ret = -1;
while (fread(&fe, sizeof(fe), 1, fp) == 1 && ret != 0)
switch (fe.fu_type) {
case USER_PROCESS:
case INIT_PROCESS:
case LOGIN_PROCESS:
if (memcmp(fu->fu_id, fe.fu_id, sizeof(fe.fu_id)) != 0)
continue;
/* Terminate session. */
if (fseeko(fp, -(off_t)sizeof(fe), SEEK_CUR) == -1)
error = errno;
else if (fwrite(fu, sizeof(*fu), 1, fp) < 1)
error = errno;
else
ret = 0;
}
fclose(fp);
errno = error;
return (ret);
}
static void
utx_active_init(const struct futx *fu)
{
int fd;
/* Initialize utx.active with a single BOOT_TIME record. */
fd = _open(_PATH_UTX_ACTIVE, O_CREAT|O_RDWR|O_TRUNC, 0644);
if (fd < 0)
return;
_write(fd, fu, sizeof(*fu));
_close(fd);
}
static void
utx_active_purge(void)
{
truncate(_PATH_UTX_ACTIVE, 0);
}
static int
utx_lastlogin_add(const struct futx *fu)
{
struct futx fe;
FILE *fp;
int error, ret;
ret = 0;
/*
* Write an entry to lastlogin. Overwrite the entry if the
* current user already has an entry. If not, append a new
* entry.
*/
fp = futx_open(_PATH_UTX_LASTLOGIN);
if (fp == NULL)
return (-1);
while (fread(&fe, sizeof fe, 1, fp) == 1) {
if (strncmp(fu->fu_user, fe.fu_user, sizeof fe.fu_user) != 0)
continue;
/* Found a previous lastlogin entry for this user. */
ret = fseeko(fp, -(off_t)sizeof fe, SEEK_CUR);
break;
}
if (ret == -1)
error = errno;
else if (fwrite(fu, sizeof *fu, 1, fp) < 1) {
error = errno;
ret = -1;
}
fclose(fp);
errno = error;
return (ret);
}
static void
utx_lastlogin_upgrade(void)
{
struct stat sb;
int fd;
fd = _open(_PATH_UTX_LASTLOGIN, O_RDWR|O_CLOEXEC, 0644);
if (fd < 0)
return;
/*
* Truncate broken lastlogin files. In the future we should
* check for older versions of the file format here and try to
* upgrade it.
*/
if (_fstat(fd, &sb) != -1 && sb.st_size % sizeof(struct futx) != 0)
ftruncate(fd, 0);
_close(fd);
}
static int
utx_log_add(const struct futx *fu)
{
struct iovec vec[2];
int error, fd;
uint16_t l;
/*
* Append an entry to the log file. We only need to append
* records to this file, so to conserve space, trim any trailing
* zero-bytes. Prepend a length field, indicating the length of
* the record, excluding the length field itself.
*/
for (l = sizeof(*fu); l > 0 && ((const char *)fu)[l - 1] == '\0'; l--) ;
vec[0].iov_base = &l;
vec[0].iov_len = sizeof(l);
vec[1].iov_base = __DECONST(void *, fu);
vec[1].iov_len = l;
l = htobe16(l);
fd = _open(_PATH_UTX_LOG, O_CREAT|O_WRONLY|O_APPEND|O_CLOEXEC, 0644);
if (fd < 0)
return (-1);
if (_writev(fd, vec, 2) == -1)
error = errno;
else
error = 0;
_close(fd);
errno = error;
return (error == 0 ? 0 : 1);
}
struct utmpx *
pututxline(const struct utmpx *utmpx)
{
struct futx fu;
int bad;
bad = 0;
utx_to_futx(utmpx, &fu);
switch (fu.fu_type) {
case BOOT_TIME:
utx_active_init(&fu);
utx_lastlogin_upgrade();
break;
case SHUTDOWN_TIME:
utx_active_purge();
break;
case OLD_TIME:
case NEW_TIME:
break;
case USER_PROCESS:
bad |= utx_active_add(&fu);
bad |= utx_lastlogin_add(&fu);
break;
#if 0 /* XXX: Are these records of any use to us? */
case INIT_PROCESS:
case LOGIN_PROCESS:
bad |= utx_active_add(&fu);
break;
#endif
case DEAD_PROCESS:
/*
* In case writing a logout entry fails, never attempt
* to write it to utx.log. The logout entry's ut_id
* might be invalid.
*/
if (utx_active_remove(&fu) != 0)
return (NULL);
break;
default:
errno = EINVAL;
return (NULL);
}
bad |= utx_log_add(&fu);
return (bad ? NULL : futx_to_utx(&fu));
}