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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 <ctype.h>
#include <fcntl.h>
#include <pwd.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <utmp.h>
#include "diag.h"
#define DEV_PREFIX "/dev/"
#define DEV_PREFIX_LEN (sizeof(DEV_PREFIX) - 1)
#define MIN(a_, b_) (((a_) < (b_)) ? (a_) : (b_))
static void
validate_device(const char *device)
{
int flags;
struct stat stb;
if (strncmp(device, DEV_PREFIX, DEV_PREFIX_LEN))
fatal_error("invalid device name");
if ((flags = fcntl(STDIN_FILENO, F_GETFL, 0)) < 0)
fatal_error("fcntl: %s", strerror(errno));
if ((flags & O_RDWR) != O_RDWR)
fatal_error("invalid descriptor mode");
if (stat(device, &stb) < 0)
fatal_error("%s: %s", device, strerror(errno));
if (getuid() != stb.st_uid)
fatal_error("%s belongs to another user", device);
}
static void
validate_hostname(const char *host)
{
for (const char *p = host; p[0]; ++p) {
unsigned char c = (unsigned char) p[0];
if (!(p == host ? isgraph : isprint)(c))
fatal_error("invalid host name (contains %#x)", c);
}
}
static int
write_uwtmp_record(const char *user, const char *term, const char *host,
pid_t pid, int add)
{
struct utmp ut;
struct timeval tv;
size_t len, offset;
memset(&ut, 0, sizeof(ut));
memset(&tv, 0, sizeof(tv));
(void) gettimeofday(&tv, 0);
len = strlen(user);
memcpy(ut.ut_name, user, MIN(sizeof(ut.ut_name), len));
if (host) {
len = strlen(host);
memcpy(ut.ut_host, host, MIN(sizeof(ut.ut_host), len));
}
len = strlen(term);
memcpy(ut.ut_line, term, MIN(sizeof(ut.ut_line), len));
offset = len <= sizeof(ut.ut_id) ? 0 : len - sizeof(ut.ut_id);
memcpy(ut.ut_id, term + offset, len - offset);
if (add)
ut.ut_type = USER_PROCESS;
else
ut.ut_type = DEAD_PROCESS;
ut.ut_pid = pid;
ut.ut_tv.tv_sec = (__typeof__(ut.ut_tv.tv_sec)) tv.tv_sec;
ut.ut_tv.tv_usec = (__typeof__(ut.ut_tv.tv_usec)) tv.tv_usec;
setutent();
if (!pututline(&ut)) {
int err = errno;
endutent();
if (err == ENOENT)
return EXIT_FAILURE;
fatal_error("pututline: %s", strerror(errno));
}
endutent();
(void) updwtmp(_PATH_WTMP, &ut);
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)
fatal_error("usage error");
if (!strcmp(argv[1], "add")) {
if (argc > 3)
fatal_error("usage error");
add = 1;
} else if (!strcmp(argv[1], "del")) {
if (argc != 2)
fatal_error("usage error");
add = 0;
} else
fatal_error("usage error");
host = argv[2];
pid = getppid();
if (pid == 1)
fatal_error("parent process should not be init");
pw = getpwuid(getuid());
if (!pw || !pw->pw_name)
fatal_error("cannot find a valid user with uid=%u", getuid());
device = ptsname(STDIN_FILENO);
if (!device)
fatal_error("cannot find slave pty: %s", strerror(errno));
validate_device(device);
if (host)
validate_hostname(host);
return write_uwtmp_record(pw->pw_name, device + DEV_PREFIX_LEN, host,
pid, add);
}
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