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nspawn: when resoliving UIDs/GIDs for "-u", do so in forked off /usr/bin/getent instead of in-process
When the container runs a different native architecture than the host we shouldn't attempt to load the container's NSS modules with the host's libc. Instead, resolve UID/GID by invoking /usr/bin/getent in the container. The tool should be fairly universally available and allows us to do resolving of the UID/GID with the container's libc in a parsable format. https://bugs.freedesktop.org/show_bug.cgi?id=75733
This commit is contained in:
Lennart Poettering
parent
d96c1ecf7b
commit
0cb9fbcd44
@ -2219,6 +2219,272 @@ static void loop_remove(int nr, int *image_fd) {
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ioctl(control, LOOP_CTL_REMOVE, nr);
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}
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static int spawn_getent(const char *database, const char *key, pid_t *rpid) {
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int pipe_fds[2];
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pid_t pid;
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assert(database);
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assert(key);
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assert(rpid);
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if (pipe2(pipe_fds, O_CLOEXEC) < 0) {
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log_error("Failed to allocate pipe: %m");
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return -errno;
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}
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pid = fork();
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if (pid < 0) {
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log_error("Failed to fork getent child: %m");
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return -errno;
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} else if (pid == 0) {
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int nullfd;
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char *empty_env = NULL;
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if (dup3(pipe_fds[1], STDOUT_FILENO, 0) < 0)
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_exit(EXIT_FAILURE);
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if (pipe_fds[0] > 2)
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close_nointr_nofail(pipe_fds[0]);
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if (pipe_fds[1] > 2)
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close_nointr_nofail(pipe_fds[1]);
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nullfd = open("/dev/null", O_RDWR);
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if (nullfd < 0)
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_exit(EXIT_FAILURE);
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if (dup3(nullfd, STDIN_FILENO, 0) < 0)
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_exit(EXIT_FAILURE);
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if (dup3(nullfd, STDERR_FILENO, 0) < 0)
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_exit(EXIT_FAILURE);
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if (nullfd > 2)
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close_nointr_nofail(nullfd);
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reset_all_signal_handlers();
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close_all_fds(NULL, 0);
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execle("/usr/bin/getent", "getenv", database, key, NULL, &empty_env);
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execle("/usr/getent", "getenv", database, key, NULL, &empty_env);
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_exit(EXIT_FAILURE);
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}
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close_nointr_nofail(pipe_fds[1]);
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pipe_fds[1] = -1;
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*rpid = pid;
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return pipe_fds[0];
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}
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static int change_uid_gid(char **_home) {
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_cleanup_strv_free_ char **passwd = NULL;
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char line[LINE_MAX], *w, *x, *state, *u, *g, *h;
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_cleanup_free_ uid_t *uids = NULL;
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_cleanup_free_ char *home = NULL;
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_cleanup_fclose_ FILE *f = NULL;
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_cleanup_close_ int fd = -1;
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unsigned n_uids = 0;
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size_t sz, l;
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uid_t uid;
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gid_t gid;
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pid_t pid;
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int r;
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assert(_home);
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if (!arg_user || streq(arg_user, "root") || streq(arg_user, "0")) {
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/* Reset everything fully to 0, just in case */
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if (setgroups(0, NULL) < 0) {
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log_error("setgroups() failed: %m");
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return -errno;
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}
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if (setresgid(0, 0, 0) < 0) {
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log_error("setregid() failed: %m");
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return -errno;
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}
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if (setresuid(0, 0, 0) < 0) {
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log_error("setreuid() failed: %m");
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return -errno;
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}
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*_home = NULL;
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return 0;
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}
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/* First, get user credentials */
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fd = spawn_getent("passwd", arg_user, &pid);
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if (fd < 0)
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return fd;
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f = fdopen(fd, "r");
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if (!f)
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return log_oom();
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fd = -1;
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if (!fgets(line, sizeof(line), f)) {
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if (!ferror(f)) {
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log_error("Failed to resolve user %s.", arg_user);
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return -ESRCH;
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}
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log_error("Failed to read from getent: %m");
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return -errno;
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}
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truncate_nl(line);
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wait_for_terminate_and_warn("getent passwd", pid);
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x = strchr(line, ':');
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if (!x) {
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log_error("/etc/passwd entry has invalid user field.");
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return -EIO;
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}
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u = strchr(x+1, ':');
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if (!u) {
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log_error("/etc/passwd entry has invalid password field.");
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return -EIO;
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}
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u++;
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g = strchr(u, ':');
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if (!g) {
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log_error("/etc/passwd entry has invalid UID field.");
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return -EIO;
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}
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*g = 0;
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g++;
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x = strchr(g, ':');
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if (!x) {
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log_error("/etc/passwd entry has invalid GID field.");
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return -EIO;
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}
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*x = 0;
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h = strchr(x+1, ':');
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if (!h) {
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log_error("/etc/passwd entry has invalid GECOS field.");
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return -EIO;
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}
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h++;
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x = strchr(h, ':');
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if (!x) {
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log_error("/etc/passwd entry has invalid home directory field.");
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return -EIO;
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}
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*x = 0;
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r = parse_uid(u, &uid);
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if (r < 0) {
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log_error("Failed to parse UID of user.");
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return -EIO;
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}
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r = parse_gid(g, &gid);
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if (r < 0) {
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log_error("Failed to parse GID of user.");
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return -EIO;
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}
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home = strdup(h);
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if (!home)
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return log_oom();
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/* Second, get group memberships */
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fd = spawn_getent("initgroups", arg_user, &pid);
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if (fd < 0)
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return fd;
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fclose(f);
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f = fdopen(fd, "r");
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if (!f)
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return log_oom();
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fd = -1;
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if (!fgets(line, sizeof(line), f)) {
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if (!ferror(f)) {
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log_error("Failed to resolve user %s.", arg_user);
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return -ESRCH;
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}
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log_error("Failed to read from getent: %m");
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return -errno;
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}
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truncate_nl(line);
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wait_for_terminate_and_warn("getent initgroups", pid);
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/* Skip over the username and subsequent separator whitespace */
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x = line;
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x += strcspn(x, WHITESPACE);
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x += strspn(x, WHITESPACE);
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FOREACH_WORD(w, l, x, state) {
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char c[l+1];
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memcpy(c, w, l);
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c[l] = 0;
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if (!GREEDY_REALLOC(uids, sz, n_uids+1))
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return log_oom();
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r = parse_uid(c, &uids[n_uids++]);
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if (r < 0) {
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log_error("Failed to parse group data from getent.");
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return -EIO;
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}
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}
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r = mkdir_parents(home, 0775);
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if (r < 0) {
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log_error("Failed to make home root directory: %s", strerror(-r));
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return r;
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}
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r = mkdir_safe(home, 0755, uid, gid);
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if (r < 0) {
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log_error("Failed to make home directory: %s", strerror(-r));
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return r;
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}
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fchown(STDIN_FILENO, uid, gid);
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fchown(STDOUT_FILENO, uid, gid);
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fchown(STDERR_FILENO, uid, gid);
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if (setgroups(n_uids, uids) < 0) {
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log_error("Failed to set auxiliary groups: %m");
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return -errno;
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}
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if (setresgid(gid, gid, gid) < 0) {
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log_error("setregid() failed: %m");
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return -errno;
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}
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if (setresuid(uid, uid, uid) < 0) {
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log_error("setreuid() failed: %m");
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return -errno;
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}
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if (_home) {
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*_home = home;
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home = NULL;
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}
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return 0;
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}
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int main(int argc, char *argv[]) {
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_cleanup_free_ char *kdbus_domain = NULL, *device_path = NULL, *root_device = NULL, *home_device = NULL, *srv_device = NULL;
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@ -2427,9 +2693,7 @@ int main(int argc, char *argv[]) {
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if (pid == 0) {
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/* child */
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const char *home = NULL;
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uid_t uid = (uid_t) -1;
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gid_t gid = (gid_t) -1;
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_cleanup_free_ char *home = NULL;
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unsigned n_env = 2;
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const char *envp[] = {
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"PATH=" DEFAULT_PATH_SPLIT_USR,
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@ -2598,61 +2862,9 @@ int main(int argc, char *argv[]) {
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goto child_fail;
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}
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if (arg_user) {
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/* Note that this resolves user names
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* inside the container, and hence
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* accesses the NSS modules from the
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* container and not the host. This is
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* a bit weird... */
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if (get_user_creds((const char**)&arg_user, &uid, &gid, &home, NULL) < 0) {
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log_error("get_user_creds() failed: %m");
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goto child_fail;
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}
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if (mkdir_parents_label(home, 0775) < 0) {
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log_error("mkdir_parents_label() failed: %m");
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goto child_fail;
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}
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if (mkdir_safe_label(home, 0775, uid, gid) < 0) {
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log_error("mkdir_safe_label() failed: %m");
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goto child_fail;
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}
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if (initgroups((const char*)arg_user, gid) < 0) {
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log_error("initgroups() failed: %m");
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goto child_fail;
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}
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if (setresgid(gid, gid, gid) < 0) {
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log_error("setregid() failed: %m");
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goto child_fail;
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}
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if (setresuid(uid, uid, uid) < 0) {
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log_error("setreuid() failed: %m");
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goto child_fail;
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}
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} else {
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/* Reset everything fully to 0, just in case */
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if (setgroups(0, NULL) < 0) {
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log_error("setgroups() failed: %m");
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goto child_fail;
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}
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if (setresgid(0, 0, 0) < 0) {
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log_error("setregid() failed: %m");
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goto child_fail;
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}
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if (setresuid(0, 0, 0) < 0) {
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log_error("setreuid() failed: %m");
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goto child_fail;
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}
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}
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r = change_uid_gid(&home);
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if (r < 0)
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goto child_fail;
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if ((asprintf((char**)(envp + n_env++), "HOME=%s", home ? home: "/root") < 0) ||
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(asprintf((char**)(envp + n_env++), "USER=%s", arg_user ? arg_user : "root") < 0) ||
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@ -2698,8 +2910,10 @@ int main(int argc, char *argv[]) {
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#ifdef HAVE_SELINUX
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if (arg_selinux_context)
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if (setexeccon((security_context_t) arg_selinux_context) < 0)
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if (setexeccon((security_context_t) arg_selinux_context) < 0) {
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log_error("setexeccon(\"%s\") failed: %m", arg_selinux_context);
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goto child_fail;
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}
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#endif
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if (!strv_isempty(arg_setenv)) {
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@ -41,7 +41,9 @@ int mkdir_safe_internal(const char *path, mode_t mode, uid_t uid, gid_t gid, mkd
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if (lstat(path, &st) < 0)
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return -errno;
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if ((st.st_mode & 0777) != mode ||
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if ((st.st_mode & 0007) > (mode & 0007) ||
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(st.st_mode & 0070) > (mode & 0070) ||
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(st.st_mode & 0700) > (mode & 0700) ||
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(uid != (uid_t) -1 && st.st_uid != uid) ||
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(gid != (gid_t) -1 && st.st_gid != gid) ||
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!S_ISDIR(st.st_mode)) {
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