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Diffstat (limited to 'src/libsystemd-basic/src/user-util.c')
-rw-r--r-- | src/libsystemd-basic/src/user-util.c | 636 |
1 files changed, 636 insertions, 0 deletions
diff --git a/src/libsystemd-basic/src/user-util.c b/src/libsystemd-basic/src/user-util.c new file mode 100644 index 0000000000..be849dfa5e --- /dev/null +++ b/src/libsystemd-basic/src/user-util.c @@ -0,0 +1,636 @@ +/*** + 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 "systemd-basic/alloc-util.h" +#include "systemd-basic/fd-util.h" +#include "systemd-basic/fileio.h" +#include "systemd-basic/formats-util.h" +#include "systemd-basic/macro.h" +#include "systemd-basic/missing.h" +#include "systemd-basic/parse-util.h" +#include "systemd-basic/path-util.h" +#include "systemd-basic/string-util.h" +#include "systemd-basic/strv.h" +#include "systemd-basic/user-util.h" +#include "systemd-basic/utf8.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 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. */ + + 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') && + *i != '_' && + *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; +} |