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-rw-r--r--src/systemd-nspawn/nspawn-setuid.c271
1 files changed, 271 insertions, 0 deletions
diff --git a/src/systemd-nspawn/nspawn-setuid.c b/src/systemd-nspawn/nspawn-setuid.c
new file mode 100644
index 0000000000..129d3acc5f
--- /dev/null
+++ b/src/systemd-nspawn/nspawn-setuid.c
@@ -0,0 +1,271 @@
+/***
+ 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 <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, *u, *g, *h;
+ 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;
+
+ 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 passwd", pid, true);
+
+ 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();
+
+ /* 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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