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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <fcntl.h>
#include <sys/types.h>
#include <unistd.h>
#include "alloc-util.h"
#include "def.h"
#include "errno.h"
#include "fd-util.h"
#include "fileio.h"
#include "mkdir.h"
#include "nspawn-setuid.h"
#include "process-util.h"
#include "rlimit-util.h"
#include "signal-util.h"
#include "string-util.h"
#include "strv.h"
#include "user-util.h"
#include "util.h"
static int spawn_getent(const char *database, const char *key, pid_t *rpid) {
int pipe_fds[2], r;
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");
r = safe_fork("(getent)", FORK_RESET_SIGNALS|FORK_DEATHSIG|FORK_LOG, &pid);
if (r < 0) {
safe_close_pair(pipe_fds);
return r;
}
if (r == 0) {
char *empty_env = NULL;
safe_close(pipe_fds[0]);
if (rearrange_stdio(-1, pipe_fds[1], -1) < 0)
_exit(EXIT_FAILURE);
(void) close_all_fds(NULL, 0);
(void) rlimit_nofile_safe();
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_raw(
uid_t uid,
gid_t gid,
const gid_t *supplementary_gids,
size_t n_supplementary_gids,
bool chown_stdio) {
if (!uid_is_valid(uid))
uid = 0;
if (!gid_is_valid(gid))
gid = 0;
if (chown_stdio) {
(void) fchown(STDIN_FILENO, uid, gid);
(void) fchown(STDOUT_FILENO, uid, gid);
(void) fchown(STDERR_FILENO, uid, gid);
}
if (setgroups(n_supplementary_gids, supplementary_gids) < 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");
return 0;
}
int change_uid_gid(const char *user, bool chown_stdio, char **ret_home) {
char *x, *u, *g, *h;
_cleanup_free_ gid_t *gids = NULL;
_cleanup_free_ char *home = NULL, *line = NULL;
_cleanup_fclose_ FILE *f = NULL;
_cleanup_close_ int fd = -1;
unsigned n_gids = 0;
size_t sz = 0;
uid_t uid;
gid_t gid;
pid_t pid;
int r;
assert(ret_home);
if (!user || STR_IN_SET(user, "root", "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");
*ret_home = NULL;
return 0;
}
/* First, get user credentials */
fd = spawn_getent("passwd", user, &pid);
if (fd < 0)
return fd;
f = take_fdopen(&fd, "r");
if (!f)
return log_oom();
r = read_line(f, LONG_LINE_MAX, &line);
if (r == 0)
return log_error_errno(SYNTHETIC_ERRNO(ESRCH),
"Failed to resolve user %s.", user);
if (r < 0)
return log_error_errno(r, "Failed to read from getent: %m");
(void) wait_for_terminate_and_check("getent passwd", pid, WAIT_LOG);
x = strchr(line, ':');
if (!x)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid user field.");
u = strchr(x+1, ':');
if (!u)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid password field.");
u++;
g = strchr(u, ':');
if (!g)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid UID field.");
*g = 0;
g++;
x = strchr(g, ':');
if (!x)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid GID field.");
*x = 0;
h = strchr(x+1, ':');
if (!h)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid GECOS field.");
h++;
x = strchr(h, ':');
if (!x)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"/etc/passwd entry has invalid home directory field.");
*x = 0;
r = parse_uid(u, &uid);
if (r < 0)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to parse UID of user.");
r = parse_gid(g, &gid);
if (r < 0)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to parse GID of user.");
home = strdup(h);
if (!home)
return log_oom();
f = safe_fclose(f);
line = mfree(line);
/* Second, get group memberships */
fd = spawn_getent("initgroups", user, &pid);
if (fd < 0)
return fd;
f = take_fdopen(&fd, "r");
if (!f)
return log_oom();
r = read_line(f, LONG_LINE_MAX, &line);
if (r == 0)
return log_error_errno(SYNTHETIC_ERRNO(ESRCH),
"Failed to resolve user %s.", user);
if (r < 0)
return log_error_errno(r, "Failed to read from getent: %m");
(void) wait_for_terminate_and_check("getent initgroups", pid, WAIT_LOG);
/* Skip over the username and subsequent separator whitespace */
x = line;
x += strcspn(x, WHITESPACE);
x += strspn(x, WHITESPACE);
for (const char *p = x;;) {
_cleanup_free_ char *word = NULL;
r = extract_first_word(&p, &word, NULL, 0);
if (r < 0)
return log_error_errno(r, "Failed to parse group data from getent: %m");
if (r == 0)
break;
if (!GREEDY_REALLOC(gids, sz, n_gids+1))
return log_oom();
r = parse_gid(word, &gids[n_gids++]);
if (r < 0)
return log_error_errno(r, "Failed to parse group data from getent: %m");
}
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, 0);
if (r < 0 && !IN_SET(r, -EEXIST, -ENOTDIR))
return log_error_errno(r, "Failed to make home directory: %m");
r = change_uid_gid_raw(uid, gid, gids, n_gids, chown_stdio);
if (r < 0)
return r;
if (ret_home)
*ret_home = TAKE_PTR(home);
return 0;
}
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