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/* SPDX-License-Identifier: LGPL-2.1+ */
/***
Copyright 2015 Lennart Poettering
***/
#include <grp.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 "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);
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 *x, *u, *g, *h;
const char *word, *state;
_cleanup_free_ uid_t *uids = NULL;
_cleanup_free_ char *home = NULL, *line = 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 || 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");
*_home = NULL;
return 0;
}
/* First, get user credentials */
fd = spawn_getent("passwd", user, &pid);
if (fd < 0)
return fd;
f = fdopen(fd, "re");
if (!f)
return log_oom();
fd = -1;
r = read_line(f, LONG_LINE_MAX, &line);
if (r == 0) {
log_error("Failed to resolve user %s.", user);
return -ESRCH;
}
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) {
log_error("/etc/passwd entry has invalid user field.");
return -EIO;
}
u = strchr(x+1, ':');
if (!u) {
log_error("/etc/passwd entry has invalid password field.");
return -EIO;
}
u++;
g = strchr(u, ':');
if (!g) {
log_error("/etc/passwd entry has invalid UID field.");
return -EIO;
}
*g = 0;
g++;
x = strchr(g, ':');
if (!x) {
log_error("/etc/passwd entry has invalid GID field.");
return -EIO;
}
*x = 0;
h = strchr(x+1, ':');
if (!h) {
log_error("/etc/passwd entry has invalid GECOS field.");
return -EIO;
}
h++;
x = strchr(h, ':');
if (!x) {
log_error("/etc/passwd entry has invalid home directory field.");
return -EIO;
}
*x = 0;
r = parse_uid(u, &uid);
if (r < 0) {
log_error("Failed to parse UID of user.");
return -EIO;
}
r = parse_gid(g, &gid);
if (r < 0) {
log_error("Failed to parse GID of user.");
return -EIO;
}
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 = fdopen(fd, "re");
if (!f)
return log_oom();
fd = -1;
r = read_line(f, LONG_LINE_MAX, &line);
if (r == 0) {
log_error("Failed to resolve user %s.", user);
return -ESRCH;
}
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);
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)
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");
(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 = TAKE_PTR(home);
return 0;
}
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