Adding upstream version 241.upstream/241upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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