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/***
This file is part of systemd.
Copyright 2015 Lennart Poettering
systemd 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.
systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include "systemd-basic/alloc-util.h"
#include "systemd-basic/fd-util.h"
#include "systemd-basic/mkdir.h"
#include "systemd-basic/process-util.h"
#include "systemd-basic/signal-util.h"
#include "systemd-basic/string-util.h"
#include "systemd-basic/user-util.h"
#include "systemd-basic/util.h"
#include "nspawn-setuid.h"
static int spawn_getent(const char *database, const char *key, pid_t *rpid) {
int pipe_fds[2];
pid_t pid;
assert(database);
assert(key);
assert(rpid);
if (pipe2(pipe_fds, O_CLOEXEC) < 0)
return log_error_errno(errno, "Failed to allocate pipe: %m");
pid = fork();
if (pid < 0)
return log_error_errno(errno, "Failed to fork getent child: %m");
else if (pid == 0) {
int nullfd;
char *empty_env = NULL;
if (dup3(pipe_fds[1], STDOUT_FILENO, 0) < 0)
_exit(EXIT_FAILURE);
if (pipe_fds[0] > 2)
safe_close(pipe_fds[0]);
if (pipe_fds[1] > 2)
safe_close(pipe_fds[1]);
nullfd = open("/dev/null", O_RDWR);
if (nullfd < 0)
_exit(EXIT_FAILURE);
if (dup3(nullfd, STDIN_FILENO, 0) < 0)
_exit(EXIT_FAILURE);
if (dup3(nullfd, STDERR_FILENO, 0) < 0)
_exit(EXIT_FAILURE);
if (nullfd > 2)
safe_close(nullfd);
(void) reset_all_signal_handlers();
(void) reset_signal_mask();
close_all_fds(NULL, 0);
execle("/usr/bin/getent", "getent", database, key, NULL, &empty_env);
execle("/bin/getent", "getent", database, key, NULL, &empty_env);
_exit(EXIT_FAILURE);
}
pipe_fds[1] = safe_close(pipe_fds[1]);
*rpid = pid;
return pipe_fds[0];
}
int change_uid_gid(const char *user, char **_home) {
char line[LINE_MAX], *x;
struct passwd *pw;
const char *word, *state;
_cleanup_free_ uid_t *uids = NULL;
_cleanup_free_ char *home = NULL;
_cleanup_fclose_ FILE *f = NULL;
_cleanup_close_ int fd = -1;
unsigned n_uids = 0;
size_t sz = 0, l;
uid_t uid;
gid_t gid;
pid_t pid;
int r;
assert(_home);
if (!user || streq(user, "root") || streq(user, "0")) {
/* Reset everything fully to 0, just in case */
r = reset_uid_gid();
if (r < 0)
return log_error_errno(r, "Failed to become root: %m");
*_home = NULL;
return 0;
}
/* First, get user credentials */
fd = spawn_getent("passwd", user, &pid);
if (fd < 0)
return fd;
f = fdopen(fd, "r");
if (!f)
return log_oom();
fd = -1;
errno = 0;
if (!(pw = fgetpwent(f))) {
if (!errno) {
log_error("Failed to resolve user %s.", user);
return -ESRCH;
}
return log_error_errno(errno, "Failed to read from getent: %m");
}
wait_for_terminate_and_warn("getent passwd", pid, true);
uid = pw->pw_uid;
gid = pw->pw_gid;
home = strdup(pw->pw_dir);
if (!home)
return log_oom();
/* Second, get group memberships */
fd = spawn_getent("initgroups", user, &pid);
if (fd < 0)
return fd;
fclose(f);
f = fdopen(fd, "r");
if (!f)
return log_oom();
fd = -1;
if (!fgets(line, sizeof(line), f)) {
if (!ferror(f)) {
log_error("Failed to resolve user %s.", user);
return -ESRCH;
}
return log_error_errno(errno, "Failed to read from getent: %m");
}
truncate_nl(line);
wait_for_terminate_and_warn("getent initgroups", pid, true);
/* Skip over the username and subsequent separator whitespace */
x = line;
x += strcspn(x, WHITESPACE);
x += strspn(x, WHITESPACE);
FOREACH_WORD(word, l, x, state) {
char c[l+1];
memcpy(c, word, l);
c[l] = 0;
if (!GREEDY_REALLOC(uids, sz, n_uids+1))
return log_oom();
r = parse_uid(c, &uids[n_uids++]);
if (r < 0) {
log_error("Failed to parse group data from getent.");
return -EIO;
}
}
r = mkdir_parents(home, 0775);
if (r < 0)
return log_error_errno(r, "Failed to make home root directory: %m");
r = mkdir_safe(home, 0755, uid, gid);
if (r < 0 && r != -EEXIST)
return log_error_errno(r, "Failed to make home directory: %m");
(void) fchown(STDIN_FILENO, uid, gid);
(void) fchown(STDOUT_FILENO, uid, gid);
(void) fchown(STDERR_FILENO, uid, gid);
if (setgroups(n_uids, uids) < 0)
return log_error_errno(errno, "Failed to set auxiliary groups: %m");
if (setresgid(gid, gid, gid) < 0)
return log_error_errno(errno, "setresgid() failed: %m");
if (setresuid(uid, uid, uid) < 0)
return log_error_errno(errno, "setresuid() failed: %m");
if (_home) {
*_home = home;
home = NULL;
}
return 0;
}
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