/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include #include #include #include #include #include #include "sd-messages.h" #include "alloc-util.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 "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"); } 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 : 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 (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_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 (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; 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 (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; 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 **_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_valid(e) && path_is_absolute(e)) { h = strdup(e); if (!h) return -ENOMEM; *_h = path_simplify(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_or_else(ESRCH); if (!path_is_valid(p->pw_dir) || !path_is_absolute(p->pw_dir)) return -EINVAL; h = strdup(p->pw_dir); if (!h) return -ENOMEM; *_h = path_simplify(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 = secure_getenv("SHELL"); if (e && path_is_valid(e) && path_is_absolute(e)) { s = strdup(e); if (!s) return -ENOMEM; *_s = path_simplify(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(NOLOGIN); if (!s) return -ENOMEM; *_s = s; return 0; } /* Check the database... */ errno = 0; p = getpwuid(u); if (!p) return errno_or_else(ESRCH); if (!path_is_valid(p->pw_shell) || !path_is_absolute(p->pw_shell)) return -EINVAL; s = strdup(p->pw_shell); if (!s) return -ENOMEM; *_s = 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 (!(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; 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) { struct passwd *p; assert(pw); assert(stream); errno = 0; p = fgetpwent(stream); if (!p && errno != ENOENT) return errno_or_else(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_or_else(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_or_else(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_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"; }