| /*** |
| 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 <alloca.h> |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <grp.h> |
| #include <pwd.h> |
| #include <stddef.h> |
| #include <stdint.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <sys/stat.h> |
| #include <unistd.h> |
| #include <utmp.h> |
| |
| #include "alloc-util.h" |
| #include "fd-util.h" |
| #include "fileio.h" |
| #include "format-util.h" |
| #include "macro.h" |
| #include "missing.h" |
| #include "parse-util.h" |
| #include "path-util.h" |
| #include "string-util.h" |
| #include "strv.h" |
| #include "user-util.h" |
| #include "utf8.h" |
| |
| bool uid_is_valid(uid_t uid) { |
| |
| /* Also see POSIX IEEE Std 1003.1-2008, 2016 Edition, 3.436. */ |
| |
| /* 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 from 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_user_creds_clean( |
| const char **username, |
| uid_t *uid, gid_t *gid, |
| const char **home, |
| const char **shell) { |
| |
| int r; |
| |
| /* Like get_user_creds(), but resets home/shell to NULL if they don't contain anything relevant. */ |
| |
| r = get_user_creds(username, uid, gid, home, shell); |
| if (r < 0) |
| return r; |
| |
| if (shell && |
| (isempty(*shell) || PATH_IN_SET(*shell, |
| "/bin/nologin", |
| "/sbin/nologin", |
| "/usr/bin/nologin", |
| "/usr/sbin/nologin"))) |
| *shell = NULL; |
| |
| if (home && |
| (isempty(*home) || path_equal(*home, "/"))) |
| *home = NULL; |
| |
| 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) { |
| int r; |
| |
| r = maybe_setgroups(0, NULL); |
| if (r < 0) |
| return r; |
| |
| 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 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; |
| } |
| |
| bool valid_user_group_name(const char *u) { |
| const char *i; |
| long sz; |
| |
| /* Checks if the specified name is a valid user/group name. Also see POSIX IEEE Std 1003.1-2008, 2016 Edition, |
| * 3.437. We are a bit stricter here however. Specifically we deviate from POSIX rules: |
| * |
| * - We don't allow any dots (this would break chown syntax which permits dots as user/group name separator) |
| * - We require that names fit into the appropriate utmp field |
| * - We don't allow empty user names |
| * |
| * Note that other systems are even more restrictive, and don't permit underscores or uppercase characters. |
| */ |
| |
| if (isempty(u)) |
| return false; |
| |
| if (!(u[0] >= 'a' && u[0] <= 'z') && |
| !(u[0] >= 'A' && u[0] <= 'Z') && |
| u[0] != '_') |
| return false; |
| |
| for (i = u+1; *i; i++) { |
| if (!(*i >= 'a' && *i <= 'z') && |
| !(*i >= 'A' && *i <= 'Z') && |
| !(*i >= '0' && *i <= '9') && |
| !IN_SET(*i, '_', '-')) |
| return false; |
| } |
| |
| sz = sysconf(_SC_LOGIN_NAME_MAX); |
| assert_se(sz > 0); |
| |
| if ((size_t) (i-u) > (size_t) sz) |
| return false; |
| |
| if ((size_t) (i-u) > UT_NAMESIZE - 1) |
| return false; |
| |
| return true; |
| } |
| |
| bool valid_user_group_name_or_id(const char *u) { |
| |
| /* Similar as above, but is also fine with numeric UID/GID specifications, as long as they are in the right |
| * range, and not the invalid user ids. */ |
| |
| if (isempty(u)) |
| return false; |
| |
| if (valid_user_group_name(u)) |
| return true; |
| |
| return parse_uid(u, NULL) >= 0; |
| } |
| |
| bool valid_gecos(const char *d) { |
| |
| if (!d) |
| return false; |
| |
| if (!utf8_is_valid(d)) |
| return false; |
| |
| if (string_has_cc(d, NULL)) |
| return false; |
| |
| /* Colons are used as field separators, and hence not OK */ |
| if (strchr(d, ':')) |
| return false; |
| |
| return true; |
| } |
| |
| bool valid_home(const char *p) { |
| |
| if (isempty(p)) |
| return false; |
| |
| if (!utf8_is_valid(p)) |
| return false; |
| |
| if (string_has_cc(p, NULL)) |
| return false; |
| |
| if (!path_is_absolute(p)) |
| return false; |
| |
| if (!path_is_safe(p)) |
| return false; |
| |
| /* Colons are used as field separators, and hence not OK */ |
| if (strchr(p, ':')) |
| return false; |
| |
| return true; |
| } |
| |
| int maybe_setgroups(size_t size, const gid_t *list) { |
| int r; |
| |
| /* Check if setgroups is allowed before we try to drop all the auxiliary groups */ |
| if (size == 0) { /* Dropping all aux groups? */ |
| _cleanup_free_ char *setgroups_content = NULL; |
| bool can_setgroups; |
| |
| r = read_one_line_file("/proc/self/setgroups", &setgroups_content); |
| if (r == -ENOENT) |
| /* Old kernels don't have /proc/self/setgroups, so assume we can use setgroups */ |
| can_setgroups = true; |
| else if (r < 0) |
| return r; |
| else |
| can_setgroups = streq(setgroups_content, "allow"); |
| |
| if (!can_setgroups) { |
| log_debug("Skipping setgroups(), /proc/self/setgroups is set to 'deny'"); |
| return 0; |
| } |
| } |
| |
| if (setgroups(size, list) < 0) |
| return -errno; |
| |
| return 0; |
| } |