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-rw-r--r--src/basic/user-util.c1068
1 files changed, 1068 insertions, 0 deletions
diff --git a/src/basic/user-util.c b/src/basic/user-util.c
new file mode 100644
index 0000000..519e788
--- /dev/null
+++ b/src/basic/user-util.c
@@ -0,0 +1,1068 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <utmp.h>
+
+#include "sd-messages.h"
+
+#include "alloc-util.h"
+#include "chase-symlinks.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "format-util.h"
+#include "macro.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "random-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));
+
+ /* We are very strict when parsing UIDs, and prohibit +/- as prefix, leading zero as prefix, and
+ * whitespace. We do this, since this call is often used in a context where we parse things as UID
+ * first, and if that doesn't work we fall back to NSS. Thus we really want to make sure that UIDs
+ * are parsed as UIDs only if they really really look like UIDs. */
+ r = safe_atou32_full(s, 10
+ | SAFE_ATO_REFUSE_PLUS_MINUS
+ | SAFE_ATO_REFUSE_LEADING_ZERO
+ | SAFE_ATO_REFUSE_LEADING_WHITESPACE, &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 distinguish
+ * invalid numeric uids from invalid
+ * strings. */
+
+ if (ret)
+ *ret = uid;
+
+ return 0;
+}
+
+int parse_uid_range(const char *s, uid_t *ret_lower, uid_t *ret_upper) {
+ _cleanup_free_ char *word = NULL;
+ uid_t l, u;
+ int r;
+
+ assert(s);
+ assert(ret_lower);
+ assert(ret_upper);
+
+ r = extract_first_word(&s, &word, "-", EXTRACT_DONT_COALESCE_SEPARATORS);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ return -EINVAL;
+
+ r = parse_uid(word, &l);
+ if (r < 0)
+ return r;
+
+ /* Check for the upper bound and extract it if needed */
+ if (!s)
+ /* Single number with no dash. */
+ u = l;
+ else if (!*s)
+ /* Trailing dash is an error. */
+ return -EINVAL;
+ else {
+ r = parse_uid(s, &u);
+ if (r < 0)
+ return r;
+
+ if (l > u)
+ return -EINVAL;
+ }
+
+ *ret_lower = l;
+ *ret_upper = u;
+ 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 = secure_getenv("USER");
+ if (e)
+ return strdup(e);
+
+ return uid_to_name(getuid());
+}
+
+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");
+}
+
+const char* default_root_shell(const char *root) {
+ /* We want to use the preferred shell, i.e. DEFAULT_USER_SHELL, which usually
+ * will be /bin/bash. Fall back to /bin/sh if DEFAULT_USER_SHELL is not found,
+ * or any access errors. */
+
+ int r = chase_symlinks(DEFAULT_USER_SHELL, root, CHASE_PREFIX_ROOT, NULL, NULL);
+ if (r < 0 && r != -ENOENT)
+ log_debug_errno(r, "Failed to look up shell '%s%s%s': %m",
+ strempty(root), root ? "/" : "", DEFAULT_USER_SHELL);
+ if (r > 0)
+ return DEFAULT_USER_SHELL;
+
+ return "/bin/sh";
+}
+
+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 = default_root_shell(NULL);
+
+ return 0;
+ }
+
+ if (STR_IN_SET(*username, NOBODY_USER_NAME, "65534") &&
+ synthesize_nobody()) {
+ *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 : 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 just return that
+ * and don't complain. */
+
+ if (uid)
+ *uid = u;
+
+ return 0;
+ }
+ } else {
+ errno = 0;
+ p = getpwnam(*username);
+ }
+ if (!p) {
+ r = errno_or_else(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) ||
+ !path_is_valid(p->pw_dir) ||
+ !path_is_absolute(p->pw_dir)))
+ *home = NULL; /* Note: we don't insist on normalized paths, since there are setups that have /./ in the path */
+ else
+ *home = p->pw_dir;
+ }
+
+ if (shell) {
+ if (FLAGS_SET(flags, USER_CREDS_CLEAN) &&
+ (isempty(p->pw_shell) ||
+ !path_is_valid(p->pw_dir) ||
+ !path_is_absolute(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 (STR_IN_SET(*groupname, NOBODY_GROUP_NAME, "65534") &&
+ synthesize_nobody()) {
+ *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_or_else(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 == UID_NOBODY && synthesize_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;
+
+ if (bufsize > LONG_MAX/2) /* overflow check */
+ return NULL;
+
+ 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 == GID_NOBODY && synthesize_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;
+
+ if (bufsize > LONG_MAX/2) /* overflow check */
+ return NULL;
+
+ bufsize *= 2;
+ }
+ }
+
+ if (asprintf(&ret, GID_FMT, gid) < 0)
+ return NULL;
+
+ return ret;
+}
+
+static bool gid_list_has(const gid_t *list, size_t size, gid_t val) {
+ for (size_t i = 0; i < size; i++)
+ if (list[i] == val)
+ return true;
+ return false;
+}
+
+int in_gid(gid_t gid) {
+ _cleanup_free_ gid_t *gids = NULL;
+ int ngroups;
+
+ if (getgid() == gid)
+ return 1;
+
+ if (getegid() == gid)
+ return 1;
+
+ if (!gid_is_valid(gid))
+ return -EINVAL;
+
+ ngroups = getgroups_alloc(&gids);
+ if (ngroups < 0)
+ return ngroups;
+
+ return gid_list_has(gids, ngroups, gid);
+}
+
+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 merge_gid_lists(const gid_t *list1, size_t size1, const gid_t *list2, size_t size2, gid_t **ret) {
+ size_t nresult = 0;
+ assert(ret);
+
+ if (size2 > INT_MAX - size1)
+ return -ENOBUFS;
+
+ gid_t *buf = new(gid_t, size1 + size2);
+ if (!buf)
+ return -ENOMEM;
+
+ /* Duplicates need to be skipped on merging, otherwise they'll be passed on and stored in the kernel. */
+ for (size_t i = 0; i < size1; i++)
+ if (!gid_list_has(buf, nresult, list1[i]))
+ buf[nresult++] = list1[i];
+ for (size_t i = 0; i < size2; i++)
+ if (!gid_list_has(buf, nresult, list2[i]))
+ buf[nresult++] = list2[i];
+ *ret = buf;
+ return (int)nresult;
+}
+
+int getgroups_alloc(gid_t** gids) {
+ gid_t *allocated;
+ _cleanup_free_ gid_t *p = NULL;
+ int ngroups = 8;
+ unsigned attempt = 0;
+
+ allocated = new(gid_t, ngroups);
+ if (!allocated)
+ return -ENOMEM;
+ p = allocated;
+
+ for (;;) {
+ ngroups = getgroups(ngroups, p);
+ if (ngroups >= 0)
+ break;
+ if (errno != EINVAL)
+ return -errno;
+
+ /* Give up eventually */
+ if (attempt++ > 10)
+ return -EINVAL;
+
+ /* Get actual size needed, and size the array explicitly. Note that this is potentially racy
+ * to use (in multi-threaded programs), hence let's call this in a loop. */
+ ngroups = getgroups(0, NULL);
+ if (ngroups < 0)
+ return -errno;
+ if (ngroups == 0)
+ return false;
+
+ free(allocated);
+
+ p = allocated = new(gid_t, ngroups);
+ if (!allocated)
+ return -ENOMEM;
+ }
+
+ *gids = TAKE_PTR(p);
+ return ngroups;
+}
+
+int get_home_dir(char **ret) {
+ struct passwd *p;
+ const char *e;
+ char *h;
+ uid_t u;
+
+ assert(ret);
+
+ /* Take the user specified one */
+ e = secure_getenv("HOME");
+ if (e && path_is_valid(e) && path_is_absolute(e))
+ goto found;
+
+ /* Hardcode home directory for root and nobody to avoid NSS */
+ u = getuid();
+ if (u == 0) {
+ e = "/root";
+ goto found;
+ }
+
+ if (u == UID_NOBODY && synthesize_nobody()) {
+ e = "/";
+ goto found;
+ }
+
+ /* Check the database... */
+ errno = 0;
+ p = getpwuid(u);
+ if (!p)
+ return errno_or_else(ESRCH);
+ e = p->pw_dir;
+
+ if (!path_is_valid(e) || !path_is_absolute(e))
+ return -EINVAL;
+
+ found:
+ h = strdup(e);
+ if (!h)
+ return -ENOMEM;
+
+ *ret = path_simplify(h);
+ return 0;
+}
+
+int get_shell(char **ret) {
+ struct passwd *p;
+ const char *e;
+ char *s;
+ uid_t u;
+
+ assert(ret);
+
+ /* Take the user specified one */
+ e = secure_getenv("SHELL");
+ if (e && path_is_valid(e) && path_is_absolute(e))
+ goto found;
+
+ /* Hardcode shell for root and nobody to avoid NSS */
+ u = getuid();
+ if (u == 0) {
+ e = default_root_shell(NULL);
+ goto found;
+ }
+ if (u == UID_NOBODY && synthesize_nobody()) {
+ e = NOLOGIN;
+ goto found;
+ }
+
+ /* Check the database... */
+ errno = 0;
+ p = getpwuid(u);
+ if (!p)
+ return errno_or_else(ESRCH);
+ e = p->pw_shell;
+
+ if (!path_is_valid(e) || !path_is_absolute(e))
+ return -EINVAL;
+
+ found:
+ s = strdup(e);
+ if (!s)
+ return -ENOMEM;
+
+ *ret = path_simplify(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;
+
+ return RET_NERRNO(setresuid(0, 0, 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, ValidUserFlags flags) {
+ const char *i;
+
+ /* Checks if the specified name is a valid user/group name. There are two flavours of this call:
+ * strict mode is the default which is POSIX plus some extra rules; and relaxed mode where we accept
+ * pretty much everything except the really worst offending names.
+ *
+ * Whenever we synthesize users ourselves we should use the strict mode. But when we process users
+ * created by other stuff, let's be more liberal. */
+
+ if (isempty(u)) /* An empty user name is never valid */
+ return false;
+
+ if (parse_uid(u, NULL) >= 0) /* Something that parses as numeric UID string is valid exactly when the
+ * flag for it is set */
+ return FLAGS_SET(flags, VALID_USER_ALLOW_NUMERIC);
+
+ if (FLAGS_SET(flags, VALID_USER_RELAX)) {
+
+ /* In relaxed mode we just check very superficially. Apparently SSSD and other stuff is
+ * extremely liberal (way too liberal if you ask me, even inserting "@" in user names, which
+ * is bound to cause problems for example when used with an MTA), hence only filter the most
+ * obvious cases, or where things would result in an invalid entry if such a user name would
+ * show up in /etc/passwd (or equivalent getent output).
+ *
+ * Note that we stepped far out of POSIX territory here. It's not our fault though, but
+ * SSSD's, Samba's and everybody else who ignored POSIX on this. (I mean, I am happy to step
+ * outside of POSIX' bounds any day, but I must say in this case I probably wouldn't
+ * have...) */
+
+ if (startswith(u, " ") || endswith(u, " ")) /* At least expect whitespace padding is removed
+ * at front and back (accept in the middle, since
+ * that's apparently a thing on Windows). Note
+ * that this also blocks usernames consisting of
+ * whitespace only. */
+ return false;
+
+ if (!utf8_is_valid(u)) /* We want to synthesize JSON from this, hence insist on UTF-8 */
+ return false;
+
+ if (string_has_cc(u, NULL)) /* CC characters are just dangerous (and \n in particular is the
+ * record separator in /etc/passwd), so we can't allow that. */
+ return false;
+
+ if (strpbrk(u, ":/")) /* Colons are the field separator in /etc/passwd, we can't allow
+ * that. Slashes are special to file systems paths and user names
+ * typically show up in the file system as home directories, hence
+ * don't allow slashes. */
+ return false;
+
+ if (in_charset(u, "0123456789")) /* Don't allow fully numeric strings, they might be confused
+ * with UIDs (note that this test is more broad than
+ * the parse_uid() test above, as it will cover more than
+ * the 32bit range, and it will detect 65535 (which is in
+ * invalid UID, even though in the unsigned 32 bit range) */
+ return false;
+
+ if (u[0] == '-' && in_charset(u + 1, "0123456789")) /* Don't allow negative fully numeric
+ * strings either. After all some people
+ * write 65535 as -1 (even though that's
+ * not even true on 32bit uid_t
+ * anyway) */
+ return false;
+
+ if (dot_or_dot_dot(u)) /* User names typically become home directory names, and these two are
+ * special in that context, don't allow that. */
+ return false;
+
+ /* Compare with strict result and warn if result doesn't match */
+ if (FLAGS_SET(flags, VALID_USER_WARN) && !valid_user_group_name(u, 0))
+ log_struct(LOG_NOTICE,
+ LOG_MESSAGE("Accepting user/group name '%s', which does not match strict user/group name rules.", u),
+ "USER_GROUP_NAME=%s", u,
+ "MESSAGE_ID=" SD_MESSAGE_UNSAFE_USER_NAME_STR);
+
+ /* Note that we make no restrictions on the length in relaxed mode! */
+ } else {
+ long sz;
+ size_t l;
+
+ /* 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 empty user names (see above)
+ * - We require that names fit into the appropriate utmp field
+ * - We don't allow any dots (this conflicts with chown syntax which permits dots as user/group name separator)
+ * - We don't allow dashes or digit as the first character
+ *
+ * Note that other systems are even more restrictive, and don't permit underscores or uppercase characters.
+ */
+
+ if (!ascii_isalpha(u[0]) &&
+ u[0] != '_')
+ return false;
+
+ for (i = u+1; *i; i++)
+ if (!ascii_isalpha(*i) &&
+ !ascii_isdigit(*i) &&
+ !IN_SET(*i, '_', '-'))
+ return false;
+
+ l = i - u;
+
+ sz = sysconf(_SC_LOGIN_NAME_MAX);
+ assert_se(sz > 0);
+
+ if (l > (size_t) sz)
+ return false;
+ if (l > NAME_MAX) /* must fit in a filename */
+ return false;
+ if (l > UT_NAMESIZE - 1)
+ return false;
+ }
+
+ return true;
+}
+
+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;
+}
+
+char *mangle_gecos(const char *d) {
+ char *mangled;
+
+ /* Makes sure the provided string becomes valid as a GEGOS field, by dropping bad chars. glibc's
+ * putwent() only changes \n and : to spaces. We do more: replace all CC too, and remove invalid
+ * UTF-8 */
+
+ mangled = strdup(d);
+ if (!mangled)
+ return NULL;
+
+ for (char *i = mangled; *i; i++) {
+ int len;
+
+ if ((uint8_t) *i < (uint8_t) ' ' || *i == ':') {
+ *i = ' ';
+ continue;
+ }
+
+ len = utf8_encoded_valid_unichar(i, SIZE_MAX);
+ if (len < 0) {
+ *i = ' ';
+ continue;
+ }
+
+ i += len - 1;
+ }
+
+ return mangled;
+}
+
+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;
+ }
+ }
+
+ return RET_NERRNO(setgroups(size, list));
+}
+
+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_or_else(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_or_else(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_or_else(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_or_else(EIO);
+
+ return 0;
+}
+#endif
+
+int fgetpwent_sane(FILE *stream, struct passwd **pw) {
+ assert(stream);
+ assert(pw);
+
+ errno = 0;
+ struct passwd *p = fgetpwent(stream);
+ if (!p && errno != ENOENT)
+ return errno_or_else(EIO);
+
+ *pw = p;
+ return !!p;
+}
+
+int fgetspent_sane(FILE *stream, struct spwd **sp) {
+ assert(stream);
+ assert(sp);
+
+ errno = 0;
+ struct spwd *s = fgetspent(stream);
+ if (!s && errno != ENOENT)
+ return errno_or_else(EIO);
+
+ *sp = s;
+ return !!s;
+}
+
+int fgetgrent_sane(FILE *stream, struct group **gr) {
+ assert(stream);
+ assert(gr);
+
+ errno = 0;
+ struct group *g = fgetgrent(stream);
+ if (!g && errno != ENOENT)
+ return errno_or_else(EIO);
+
+ *gr = g;
+ return !!g;
+}
+
+#if ENABLE_GSHADOW
+int fgetsgent_sane(FILE *stream, struct sgrp **sg) {
+ assert(stream);
+ assert(sg);
+
+ errno = 0;
+ struct sgrp *s = fgetsgent(stream);
+ if (!s && errno != ENOENT)
+ return errno_or_else(EIO);
+
+ *sg = s;
+ return !!s;
+}
+#endif
+
+int is_this_me(const char *username) {
+ uid_t uid;
+ int r;
+
+ /* Checks if the specified username is our current one. Passed string might be a UID or a user name. */
+
+ r = get_user_creds(&username, &uid, NULL, NULL, NULL, USER_CREDS_ALLOW_MISSING);
+ if (r < 0)
+ return r;
+
+ return uid == getuid();
+}
+
+const char *get_home_root(void) {
+ const char *e;
+
+ /* For debug purposes allow overriding where we look for home dirs */
+ e = secure_getenv("SYSTEMD_HOME_ROOT");
+ if (e && path_is_absolute(e) && path_is_normalized(e))
+ return e;
+
+ return "/home";
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-14 07:08:09 +0000