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-rw-r--r--src/basic/user-util.c857
1 files changed, 857 insertions, 0 deletions
diff --git a/src/basic/user-util.c b/src/basic/user-util.c
new file mode 100644
index 0000000..260f3d2
--- /dev/null
+++ b/src/basic/user-util.c
@@ -0,0 +1,857 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#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());
+}
+
+static bool is_nologin_shell(const char *shell) {
+
+ return PATH_IN_SET(shell,
+ /* 'nologin' is the friendliest way to disable logins for a user account. It prints a nice
+ * message and exits. Different distributions place the binary at different places though,
+ * hence let's list them all. */
+ "/bin/nologin",
+ "/sbin/nologin",
+ "/usr/bin/nologin",
+ "/usr/sbin/nologin",
+ /* 'true' and 'false' work too for the same purpose, but are less friendly as they don't do
+ * any message printing. Different distributions place the binary at various places but at
+ * least not in the 'sbin' directory. */
+ "/bin/false",
+ "/usr/bin/false",
+ "/bin/true",
+ "/usr/bin/true");
+}
+
+static int synthesize_user_creds(
+ const char **username,
+ uid_t *uid, gid_t *gid,
+ const char **home,
+ const char **shell,
+ UserCredsFlags flags) {
+
+ /* We enforce some special rules for uid=0 and uid=65534: in order to avoid NSS lookups for root we hardcode
+ * their user record data. */
+
+ if (STR_IN_SET(*username, "root", "0")) {
+ *username = "root";
+
+ if (uid)
+ *uid = 0;
+ if (gid)
+ *gid = 0;
+
+ if (home)
+ *home = "/root";
+
+ if (shell)
+ *shell = "/bin/sh";
+
+ return 0;
+ }
+
+ if (synthesize_nobody() &&
+ STR_IN_SET(*username, NOBODY_USER_NAME, "65534")) {
+ *username = NOBODY_USER_NAME;
+
+ if (uid)
+ *uid = UID_NOBODY;
+ if (gid)
+ *gid = GID_NOBODY;
+
+ if (home)
+ *home = FLAGS_SET(flags, USER_CREDS_CLEAN) ? NULL : "/";
+
+ if (shell)
+ *shell = FLAGS_SET(flags, USER_CREDS_CLEAN) ? NULL : "/sbin/nologin";
+
+ return 0;
+ }
+
+ return -ENOMEDIUM;
+}
+
+int get_user_creds(
+ const char **username,
+ uid_t *uid, gid_t *gid,
+ const char **home,
+ const char **shell,
+ UserCredsFlags flags) {
+
+ uid_t u = UID_INVALID;
+ struct passwd *p;
+ int r;
+
+ assert(username);
+ assert(*username);
+
+ if (!FLAGS_SET(flags, USER_CREDS_PREFER_NSS) ||
+ (!home && !shell)) {
+
+ /* So here's the deal: normally, we'll try to synthesize all records we can synthesize, and override
+ * the user database with that. However, if the user specifies USER_CREDS_PREFER_NSS then the
+ * user database will override the synthetic records instead — except if the user is only interested in
+ * the UID and/or GID (but not the home directory, or the shell), in which case we'll always override
+ * the user database (i.e. the USER_CREDS_PREFER_NSS flag has no effect in this case). Why?
+ * Simply because there are valid usecase where the user might change the home directory or the shell
+ * of the relevant users, but changing the UID/GID mappings for them is something we explicitly don't
+ * support. */
+
+ r = synthesize_user_creds(username, uid, gid, home, shell, flags);
+ if (r >= 0)
+ return 0;
+ if (r != -ENOMEDIUM) /* not a username we can synthesize */
+ return r;
+ }
+
+ 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 if (FLAGS_SET(flags, USER_CREDS_ALLOW_MISSING) && !gid && !home && !shell) {
+
+ /* If the specified user is a numeric UID and it isn't in the user database, and the caller
+ * passed USER_CREDS_ALLOW_MISSING and was only interested in the UID, then juts return that
+ * and don't complain. */
+
+ if (uid)
+ *uid = u;
+
+ return 0;
+ }
+ } else {
+ errno = 0;
+ p = getpwnam(*username);
+ }
+ if (!p) {
+ r = errno > 0 ? -errno : -ESRCH;
+
+ /* If the user requested that we only synthesize as fallback, do so now */
+ if (FLAGS_SET(flags, USER_CREDS_PREFER_NSS)) {
+ if (synthesize_user_creds(username, uid, gid, home, shell, flags) >= 0)
+ return 0;
+ }
+
+ return r;
+ }
+
+ 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) {
+ if (FLAGS_SET(flags, USER_CREDS_CLEAN) && empty_or_root(p->pw_dir))
+ *home = NULL;
+ else
+ *home = p->pw_dir;
+ }
+
+ if (shell) {
+ if (FLAGS_SET(flags, USER_CREDS_CLEAN) && (isempty(p->pw_shell) || is_nologin_shell(p->pw_shell)))
+ *shell = NULL;
+ else
+ *shell = p->pw_shell;
+ }
+
+ return 0;
+}
+
+int get_group_creds(const char **groupname, gid_t *gid, UserCredsFlags flags) {
+ 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 (STR_IN_SET(*groupname, "root", "0")) {
+ *groupname = "root";
+
+ if (gid)
+ *gid = 0;
+
+ return 0;
+ }
+
+ if (synthesize_nobody() &&
+ STR_IN_SET(*groupname, NOBODY_GROUP_NAME, "65534")) {
+ *groupname = NOBODY_GROUP_NAME;
+
+ if (gid)
+ *gid = GID_NOBODY;
+
+ return 0;
+ }
+
+ if (parse_gid(*groupname, &id) >= 0) {
+ errno = 0;
+ g = getgrgid(id);
+
+ if (g)
+ *groupname = g->gr_name;
+ else if (FLAGS_SET(flags, USER_CREDS_ALLOW_MISSING)) {
+ if (gid)
+ *gid = id;
+
+ return 0;
+ }
+ } 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 (synthesize_nobody() &&
+ uid == UID_NOBODY)
+ return strdup(NOBODY_USER_NAME);
+
+ 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 (synthesize_nobody() &&
+ gid == GID_NOBODY)
+ return strdup(NOBODY_GROUP_NAME);
+
+ 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) {
+ long ngroups_max;
+ gid_t *gids;
+ int 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 = newa(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, 0);
+ 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 and nobody to avoid NSS */
+ u = getuid();
+ if (u == 0) {
+ h = strdup("/root");
+ if (!h)
+ return -ENOMEM;
+
+ *_h = h;
+ return 0;
+ }
+ if (synthesize_nobody() &&
+ u == UID_NOBODY) {
+ h = strdup("/");
+ 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 shell for root and nobody to avoid NSS */
+ u = getuid();
+ if (u == 0) {
+ s = strdup("/bin/sh");
+ if (!s)
+ return -ENOMEM;
+
+ *_s = s;
+ return 0;
+ }
+ if (synthesize_nobody() &&
+ u == UID_NOBODY) {
+ s = strdup("/sbin/nologin");
+ 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_PASSWD_LOCK_PATH);
+ else
+ path = ETC_PASSWD_LOCK_PATH;
+
+ fd = open(path, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0600);
+ if (fd < 0)
+ return log_debug_errno(errno, "Cannot open %s: %m", path);
+
+ r = fcntl(fd, F_SETLKW, &flock);
+ if (r < 0) {
+ safe_close(fd);
+ return log_debug_errno(errno, "Locking %s failed: %m", path);
+ }
+
+ 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) {
+ /* Note that this function is also called by valid_shell(), any
+ * changes must account for that. */
+
+ 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_normalized(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;
+}
+
+bool synthesize_nobody(void) {
+ /* Returns true when we shall synthesize the "nobody" user (which we do by default). This can be turned off by
+ * touching /etc/systemd/dont-synthesize-nobody in order to provide upgrade compatibility with legacy systems
+ * that used the "nobody" user name and group name for other UIDs/GIDs than 65534.
+ *
+ * Note that we do not employ any kind of synchronization on the following caching variable. If the variable is
+ * accessed in multi-threaded programs in the worst case it might happen that we initialize twice, but that
+ * shouldn't matter as each initialization should come to the same result. */
+ static int cache = -1;
+
+ if (cache < 0)
+ cache = access("/etc/systemd/dont-synthesize-nobody", F_OK) < 0;
+
+ return cache;
+}
+
+int putpwent_sane(const struct passwd *pw, FILE *stream) {
+ assert(pw);
+ assert(stream);
+
+ errno = 0;
+ if (putpwent(pw, stream) != 0)
+ return errno > 0 ? -errno : -EIO;
+
+ return 0;
+}
+
+int putspent_sane(const struct spwd *sp, FILE *stream) {
+ assert(sp);
+ assert(stream);
+
+ errno = 0;
+ if (putspent(sp, stream) != 0)
+ return errno > 0 ? -errno : -EIO;
+
+ return 0;
+}
+
+int putgrent_sane(const struct group *gr, FILE *stream) {
+ assert(gr);
+ assert(stream);
+
+ errno = 0;
+ if (putgrent(gr, stream) != 0)
+ return errno > 0 ? -errno : -EIO;
+
+ return 0;
+}
+
+#if ENABLE_GSHADOW
+int putsgent_sane(const struct sgrp *sg, FILE *stream) {
+ assert(sg);
+ assert(stream);
+
+ errno = 0;
+ if (putsgent(sg, stream) != 0)
+ return errno > 0 ? -errno : -EIO;
+
+ return 0;
+}
+#endif
+
+int fgetpwent_sane(FILE *stream, struct passwd **pw) {
+ struct passwd *p;
+
+ assert(pw);
+ assert(stream);
+
+ errno = 0;
+ p = fgetpwent(stream);
+ if (!p && errno != ENOENT)
+ return errno > 0 ? -errno : -EIO;
+
+ *pw = p;
+ return !!p;
+}
+
+int fgetspent_sane(FILE *stream, struct spwd **sp) {
+ struct spwd *s;
+
+ assert(sp);
+ assert(stream);
+
+ errno = 0;
+ s = fgetspent(stream);
+ if (!s && errno != ENOENT)
+ return errno > 0 ? -errno : -EIO;
+
+ *sp = s;
+ return !!s;
+}
+
+int fgetgrent_sane(FILE *stream, struct group **gr) {
+ struct group *g;
+
+ assert(gr);
+ assert(stream);
+
+ errno = 0;
+ g = fgetgrent(stream);
+ if (!g && errno != ENOENT)
+ return errno > 0 ? -errno : -EIO;
+
+ *gr = g;
+ return !!g;
+}
+
+#if ENABLE_GSHADOW
+int fgetsgent_sane(FILE *stream, struct sgrp **sg) {
+ struct sgrp *s;
+
+ assert(sg);
+ assert(stream);
+
+ errno = 0;
+ s = fgetsgent(stream);
+ if (!s && errno != ENOENT)
+ return errno > 0 ? -errno : -EIO;
+
+ *sg = s;
+ return !!s;
+}
+#endif
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-23 02:42:40 +0000