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/*
Copyright (C) 2001,2002,2005,2010 Dmitry V. Levin <ldv@altlinux.org>
A privileged helper for utmp/wtmp updates.
This 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.
This 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 this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef _GNU_SOURCE
# define _GNU_SOURCE 1
#endif
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <pwd.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <utmp.h>
#ifdef __GLIBC__
# include <pty.h>
#elif defined(__FreeBSD__)
# include <libutil.h>
#else
# error Unsupported platform
#endif /* __GLIBC__ || __FreeBSD__ */
#define DEV_PREFIX "/dev/"
#define DEV_PREFIX_LEN (sizeof(DEV_PREFIX)-1)
static void __attribute__ ((__noreturn__))
usage(void)
{
#ifdef UTEMPTER_DEBUG
fprintf(stderr, "Usage: utempter add [<host>]\n"
" utempter del\n");
#endif
exit(EXIT_FAILURE);
}
static void
validate_device(const char *device)
{
int flags;
struct stat stb;
if (strncmp(device, DEV_PREFIX, DEV_PREFIX_LEN))
{
#ifdef UTEMPTER_DEBUG
fprintf(stderr, "utempter: invalid device name\n");
#endif
exit(EXIT_FAILURE);
}
if ((flags = fcntl(STDIN_FILENO, F_GETFL, 0)) < 0)
{
#ifdef UTEMPTER_DEBUG
fprintf(stderr, "utempter: fcntl: %s\n", strerror(errno));
#endif
exit(EXIT_FAILURE);
}
if ((flags & O_RDWR) != O_RDWR)
{
#ifdef UTEMPTER_DEBUG
fprintf(stderr, "utempter: invalid descriptor mode\n");
#endif
exit(EXIT_FAILURE);
}
if (stat(device, &stb) < 0)
{
#ifdef UTEMPTER_DEBUG
fprintf(stderr, "utempter: %s: %s\n", device,
strerror(errno));
#endif
exit(EXIT_FAILURE);
}
if (getuid() != stb.st_uid)
{
#ifdef UTEMPTER_DEBUG
fprintf(stderr, "utempter: %s belongs to another user\n",
device);
#endif
exit(EXIT_FAILURE);
}
}
static int
write_uwtmp_record(const char *user, const char *term, const char *host,
#ifdef __GLIBC__
pid_t pid,
#endif
int add)
{
struct utmp ut;
struct timeval tv;
#ifdef __GLIBC__
size_t offset;
#endif
memset(&ut, 0, sizeof(ut));
memset(&tv, 0, sizeof(tv));
(void) gettimeofday(&tv, 0);
strncpy(ut.ut_name, user, sizeof(ut.ut_name));
strncpy(ut.ut_line, term, sizeof(ut.ut_line));
if (host)
strncpy(ut.ut_host, host, sizeof(ut.ut_host));
#ifdef __GLIBC__
offset = (strlen(term) <= sizeof(ut.ut_id)) ? 0 :
strlen(term) - sizeof(ut.ut_id);
strncpy(ut.ut_id, term + offset, sizeof(ut.ut_id));
if (add)
ut.ut_type = USER_PROCESS;
else
ut.ut_type = DEAD_PROCESS;
ut.ut_pid = pid;
ut.ut_tv.tv_sec = tv.tv_sec;
ut.ut_tv.tv_usec = tv.tv_usec;
setutent();
if (!pututline(&ut))
{
#ifdef UTEMPTER_DEBUG
fprintf(stderr, "utempter: pututline: %s\n", strerror(errno));
#endif
exit(EXIT_FAILURE);
}
endutent();
(void) updwtmp(_PATH_WTMP, &ut);
#elif defined(__FreeBSD__)
ut.ut_time = tv.tv_sec;
if (add)
{
login(&ut);
} else
{
if (logout(term) != 1)
{
#ifdef UTEMPTER_DEBUG
fprintf(stderr, "utempter: logout: %s\n",
strerror(errno));
#endif
exit(EXIT_FAILURE);
}
}
#endif /* __GLIBC__ || __FreeBSD__ */
#ifdef UTEMPTER_DEBUG
fprintf(stderr,
"utempter: DEBUG: utmp/wtmp record %s for terminal '%s'\n",
add ? "added" : "removed", term);
#endif
return EXIT_SUCCESS;
}
int
main(int argc, const char *argv[])
{
const char *device, *host;
struct passwd *pw;
pid_t pid;
int add = 0, i;
for (i = 0; i <= 2; ++i)
{
struct stat sb;
if (fstat(i, &sb) < 0)
/* At this stage, we shouldn't even report error. */
exit(EXIT_FAILURE);
}
if (argc < 2)
usage();
if (!strcmp(argv[1], "add"))
{
if (argc > 3)
usage();
add = 1;
} else if (!strcmp(argv[1], "del"))
{
if (argc != 2)
usage();
add = 0;
} else
usage();
host = argv[2];
pid = getppid();
if (pid == 1)
{
#ifdef UTEMPTER_DEBUG
fprintf(stderr,
"utempter: parent process should not be init\n");
#endif
exit(EXIT_FAILURE);
}
pw = getpwuid(getuid());
if (!pw || !pw->pw_name)
{
#ifdef UTEMPTER_DEBUG
fprintf(stderr,
"utempter: cannot find valid user with uid=%u\n",
getuid());
#endif
exit(EXIT_FAILURE);
}
device = ptsname(STDIN_FILENO);
if (!device)
{
#ifdef UTEMPTER_DEBUG
fprintf(stderr, "utempter: cannot find slave pty: %s\n",
strerror(errno));
#endif
exit(EXIT_FAILURE);
}
validate_device(device);
return write_uwtmp_record(pw->pw_name, device + DEV_PREFIX_LEN, host,
#ifdef __GLIBC__
pid,
#endif
add);
}
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