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-rw-r--r--src/basic/user-util.c472
1 files changed, 472 insertions, 0 deletions
diff --git a/src/basic/user-util.c b/src/basic/user-util.c
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+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+ This file is part of systemd.
+
+ Copyright 2010 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 <pwd.h>
+#include <grp.h>
+
+#include "alloc-util.h"
+#include "fd-util.h"
+#include "macro.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "string-util.h"
+#include "user-util.h"
+#include "util.h"
+
+bool uid_is_valid(uid_t uid) {
+
+ /* Some libc APIs use UID_INVALID as special placeholder */
+ if (uid == (uid_t) UINT32_C(0xFFFFFFFF))
+ return false;
+
+ /* A long time ago UIDs where 16bit, hence explicitly avoid the 16bit -1 too */
+ if (uid == (uid_t) UINT32_C(0xFFFF))
+ return false;
+
+ return true;
+}
+
+int parse_uid(const char *s, uid_t *ret) {
+ uint32_t uid = 0;
+ int r;
+
+ assert(s);
+
+ assert_cc(sizeof(uid_t) == sizeof(uint32_t));
+ r = safe_atou32(s, &uid);
+ if (r < 0)
+ return r;
+
+ if (!uid_is_valid(uid))
+ return -ENXIO; /* we return ENXIO instead of EINVAL
+ * here, to make it easy to distuingish
+ * invalid numeric uids invalid
+ * strings. */
+
+ if (ret)
+ *ret = uid;
+
+ return 0;
+}
+
+char* getlogname_malloc(void) {
+ uid_t uid;
+ struct stat st;
+
+ if (isatty(STDIN_FILENO) && fstat(STDIN_FILENO, &st) >= 0)
+ uid = st.st_uid;
+ else
+ uid = getuid();
+
+ return uid_to_name(uid);
+}
+
+char *getusername_malloc(void) {
+ const char *e;
+
+ e = getenv("USER");
+ if (e)
+ return strdup(e);
+
+ return uid_to_name(getuid());
+}
+
+int get_user_creds(
+ const char **username,
+ uid_t *uid, gid_t *gid,
+ const char **home,
+ const char **shell) {
+
+ struct passwd *p;
+ uid_t u;
+
+ assert(username);
+ assert(*username);
+
+ /* We enforce some special rules for uid=0: in order to avoid
+ * NSS lookups for root we hardcode its data. */
+
+ if (streq(*username, "root") || streq(*username, "0")) {
+ *username = "root";
+
+ if (uid)
+ *uid = 0;
+
+ if (gid)
+ *gid = 0;
+
+ if (home)
+ *home = "/root";
+
+ if (shell)
+ *shell = "/bin/sh";
+
+ return 0;
+ }
+
+ if (parse_uid(*username, &u) >= 0) {
+ errno = 0;
+ p = getpwuid(u);
+
+ /* If there are multiple users with the same id, make
+ * sure to leave $USER to the configured value instead
+ * of the first occurrence in the database. However if
+ * the uid was configured by a numeric uid, then let's
+ * pick the real username from /etc/passwd. */
+ if (p)
+ *username = p->pw_name;
+ } else {
+ errno = 0;
+ p = getpwnam(*username);
+ }
+
+ if (!p)
+ return errno > 0 ? -errno : -ESRCH;
+
+ if (uid) {
+ if (!uid_is_valid(p->pw_uid))
+ return -EBADMSG;
+
+ *uid = p->pw_uid;
+ }
+
+ if (gid) {
+ if (!gid_is_valid(p->pw_gid))
+ return -EBADMSG;
+
+ *gid = p->pw_gid;
+ }
+
+ if (home)
+ *home = p->pw_dir;
+
+ if (shell)
+ *shell = p->pw_shell;
+
+ return 0;
+}
+
+int get_group_creds(const char **groupname, gid_t *gid) {
+ struct group *g;
+ gid_t id;
+
+ assert(groupname);
+
+ /* We enforce some special rules for gid=0: in order to avoid
+ * NSS lookups for root we hardcode its data. */
+
+ if (streq(*groupname, "root") || streq(*groupname, "0")) {
+ *groupname = "root";
+
+ if (gid)
+ *gid = 0;
+
+ return 0;
+ }
+
+ if (parse_gid(*groupname, &id) >= 0) {
+ errno = 0;
+ g = getgrgid(id);
+
+ if (g)
+ *groupname = g->gr_name;
+ } else {
+ errno = 0;
+ g = getgrnam(*groupname);
+ }
+
+ if (!g)
+ return errno > 0 ? -errno : -ESRCH;
+
+ if (gid) {
+ if (!gid_is_valid(g->gr_gid))
+ return -EBADMSG;
+
+ *gid = g->gr_gid;
+ }
+
+ return 0;
+}
+
+char* uid_to_name(uid_t uid) {
+ char *ret;
+ int r;
+
+ /* Shortcut things to avoid NSS lookups */
+ if (uid == 0)
+ return strdup("root");
+
+ if (uid_is_valid(uid)) {
+ long bufsize;
+
+ bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
+ if (bufsize <= 0)
+ bufsize = 4096;
+
+ for (;;) {
+ struct passwd pwbuf, *pw = NULL;
+ _cleanup_free_ char *buf = NULL;
+
+ buf = malloc(bufsize);
+ if (!buf)
+ return NULL;
+
+ r = getpwuid_r(uid, &pwbuf, buf, (size_t) bufsize, &pw);
+ if (r == 0 && pw)
+ return strdup(pw->pw_name);
+ if (r != ERANGE)
+ break;
+
+ bufsize *= 2;
+ }
+ }
+
+ if (asprintf(&ret, UID_FMT, uid) < 0)
+ return NULL;
+
+ return ret;
+}
+
+char* gid_to_name(gid_t gid) {
+ char *ret;
+ int r;
+
+ if (gid == 0)
+ return strdup("root");
+
+ if (gid_is_valid(gid)) {
+ long bufsize;
+
+ bufsize = sysconf(_SC_GETGR_R_SIZE_MAX);
+ if (bufsize <= 0)
+ bufsize = 4096;
+
+ for (;;) {
+ struct group grbuf, *gr = NULL;
+ _cleanup_free_ char *buf = NULL;
+
+ buf = malloc(bufsize);
+ if (!buf)
+ return NULL;
+
+ r = getgrgid_r(gid, &grbuf, buf, (size_t) bufsize, &gr);
+ if (r == 0 && gr)
+ return strdup(gr->gr_name);
+ if (r != ERANGE)
+ break;
+
+ bufsize *= 2;
+ }
+ }
+
+ if (asprintf(&ret, GID_FMT, gid) < 0)
+ return NULL;
+
+ return ret;
+}
+
+int in_gid(gid_t gid) {
+ gid_t *gids;
+ int ngroups_max, r, i;
+
+ if (getgid() == gid)
+ return 1;
+
+ if (getegid() == gid)
+ return 1;
+
+ if (!gid_is_valid(gid))
+ return -EINVAL;
+
+ ngroups_max = sysconf(_SC_NGROUPS_MAX);
+ assert(ngroups_max > 0);
+
+ gids = alloca(sizeof(gid_t) * ngroups_max);
+
+ r = getgroups(ngroups_max, gids);
+ if (r < 0)
+ return -errno;
+
+ for (i = 0; i < r; i++)
+ if (gids[i] == gid)
+ return 1;
+
+ return 0;
+}
+
+int in_group(const char *name) {
+ int r;
+ gid_t gid;
+
+ r = get_group_creds(&name, &gid);
+ if (r < 0)
+ return r;
+
+ return in_gid(gid);
+}
+
+int get_home_dir(char **_h) {
+ struct passwd *p;
+ const char *e;
+ char *h;
+ uid_t u;
+
+ assert(_h);
+
+ /* Take the user specified one */
+ e = secure_getenv("HOME");
+ if (e && path_is_absolute(e)) {
+ h = strdup(e);
+ if (!h)
+ return -ENOMEM;
+
+ *_h = h;
+ return 0;
+ }
+
+ /* Hardcode home directory for root to avoid NSS */
+ u = getuid();
+ if (u == 0) {
+ h = strdup("/root");
+ if (!h)
+ return -ENOMEM;
+
+ *_h = h;
+ return 0;
+ }
+
+ /* Check the database... */
+ errno = 0;
+ p = getpwuid(u);
+ if (!p)
+ return errno > 0 ? -errno : -ESRCH;
+
+ if (!path_is_absolute(p->pw_dir))
+ return -EINVAL;
+
+ h = strdup(p->pw_dir);
+ if (!h)
+ return -ENOMEM;
+
+ *_h = h;
+ return 0;
+}
+
+int get_shell(char **_s) {
+ struct passwd *p;
+ const char *e;
+ char *s;
+ uid_t u;
+
+ assert(_s);
+
+ /* Take the user specified one */
+ e = getenv("SHELL");
+ if (e) {
+ s = strdup(e);
+ if (!s)
+ return -ENOMEM;
+
+ *_s = s;
+ return 0;
+ }
+
+ /* Hardcode home directory for root to avoid NSS */
+ u = getuid();
+ if (u == 0) {
+ s = strdup("/bin/sh");
+ if (!s)
+ return -ENOMEM;
+
+ *_s = s;
+ return 0;
+ }
+
+ /* Check the database... */
+ errno = 0;
+ p = getpwuid(u);
+ if (!p)
+ return errno > 0 ? -errno : -ESRCH;
+
+ if (!path_is_absolute(p->pw_shell))
+ return -EINVAL;
+
+ s = strdup(p->pw_shell);
+ if (!s)
+ return -ENOMEM;
+
+ *_s = s;
+ return 0;
+}
+
+int reset_uid_gid(void) {
+
+ if (setgroups(0, NULL) < 0)
+ return -errno;
+
+ if (setresgid(0, 0, 0) < 0)
+ return -errno;
+
+ if (setresuid(0, 0, 0) < 0)
+ return -errno;
+
+ return 0;
+}
+
+int take_etc_passwd_lock(const char *root) {
+
+ struct flock flock = {
+ .l_type = F_WRLCK,
+ .l_whence = SEEK_SET,
+ .l_start = 0,
+ .l_len = 0,
+ };
+
+ const char *path;
+ int fd, r;
+
+ /* This is roughly the same as lckpwdf(), but not as awful. We
+ * don't want to use alarm() and signals, hence we implement
+ * our own trivial version of this.
+ *
+ * Note that shadow-utils also takes per-database locks in
+ * addition to lckpwdf(). However, we don't given that they
+ * are redundant as they they invoke lckpwdf() first and keep
+ * it during everything they do. The per-database locks are
+ * awfully racy, and thus we just won't do them. */
+
+ if (root)
+ path = prefix_roota(root, "/etc/.pwd.lock");
+ else
+ path = "/etc/.pwd.lock";
+
+ fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0600);
+ if (fd < 0)
+ return -errno;
+
+ r = fcntl(fd, F_SETLKW, &flock);
+ if (r < 0) {
+ safe_close(fd);
+ return -errno;
+ }
+
+ return fd;
+}
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