/* SPDX-License-Identifier: LGPL-2.1+ */ #include #include #include #include #include #include #include #include #include #include #include #include #include #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); } #if 0 /// UNNEEDED by elogind char *getusername_malloc(void) { const char *e; e = getenv("USER"); if (e) return strdup(e); return uid_to_name(getuid()); } #endif // 0 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 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 = "/"; if (shell) *shell = "/sbin/nologin"; 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; } static inline 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"); } #if 0 /// UNNEEDED by elogind 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) || is_nologin_shell(*shell))) *shell = NULL; if (home && empty_or_root(*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 (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 { 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; } #endif // 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; } #if 0 /// UNNEEDED by elogind 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); 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; } #endif // 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; } #if 0 /// UNNEEDED by elogind 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; } #endif // 0 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) { #ifdef NOLEGACY return true; #else /* 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/elogind/dont-synthesize-nobody", F_OK) < 0; return cache; #endif } #if 0 /// UNNEEDED by elogind 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 #endif // 0