diff options
Diffstat (limited to 'src/nss-systemd/nss-systemd.c')
| -rw-r--r-- | src/nss-systemd/nss-systemd.c | 640 |
1 files changed, 640 insertions, 0 deletions
diff --git a/src/nss-systemd/nss-systemd.c b/src/nss-systemd/nss-systemd.c new file mode 100644 index 0000000..758f381 --- /dev/null +++ b/src/nss-systemd/nss-systemd.c @@ -0,0 +1,640 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <nss.h> +#include <pthread.h> + +#include "env-util.h" +#include "errno-util.h" +#include "fd-util.h" +#include "macro.h" +#include "nss-systemd.h" +#include "nss-util.h" +#include "pthread-util.h" +#include "signal-util.h" +#include "strv.h" +#include "user-record-nss.h" +#include "user-util.h" +#include "userdb-glue.h" +#include "userdb.h" + +static const struct passwd root_passwd = { + .pw_name = (char*) "root", + .pw_passwd = (char*) "x", /* see shadow file */ + .pw_uid = 0, + .pw_gid = 0, + .pw_gecos = (char*) "Super User", + .pw_dir = (char*) "/root", + .pw_shell = (char*) "/bin/sh", +}; + +static const struct passwd nobody_passwd = { + .pw_name = (char*) NOBODY_USER_NAME, + .pw_passwd = (char*) "*", /* locked */ + .pw_uid = UID_NOBODY, + .pw_gid = GID_NOBODY, + .pw_gecos = (char*) "User Nobody", + .pw_dir = (char*) "/", + .pw_shell = (char*) NOLOGIN, +}; + +static const struct group root_group = { + .gr_name = (char*) "root", + .gr_gid = 0, + .gr_passwd = (char*) "x", /* see shadow file */ + .gr_mem = (char*[]) { NULL }, +}; + +static const struct group nobody_group = { + .gr_name = (char*) NOBODY_GROUP_NAME, + .gr_gid = GID_NOBODY, + .gr_passwd = (char*) "*", /* locked */ + .gr_mem = (char*[]) { NULL }, +}; + +typedef struct GetentData { + /* As explained in NOTES section of getpwent_r(3) as 'getpwent_r() is not really reentrant since it + * shares the reading position in the stream with all other threads', we need to protect the data in + * UserDBIterator from multithreaded programs which may call setpwent(), getpwent_r(), or endpwent() + * simultaneously. So, each function locks the data by using the mutex below. */ + pthread_mutex_t mutex; + UserDBIterator *iterator; + + /* Applies to group iterations only: true while we iterate over groups defined through NSS, false + * otherwise. */ + bool by_membership; +} GetentData; + +static GetentData getpwent_data = { + .mutex = PTHREAD_MUTEX_INITIALIZER +}; + +static GetentData getgrent_data = { + .mutex = PTHREAD_MUTEX_INITIALIZER +}; + +NSS_GETPW_PROTOTYPES(systemd); +NSS_GETGR_PROTOTYPES(systemd); +NSS_PWENT_PROTOTYPES(systemd); +NSS_GRENT_PROTOTYPES(systemd); +NSS_INITGROUPS_PROTOTYPE(systemd); + +enum nss_status _nss_systemd_getpwnam_r( + const char *name, + struct passwd *pwd, + char *buffer, size_t buflen, + int *errnop) { + + enum nss_status status; + int e; + + PROTECT_ERRNO; + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + assert(name); + assert(pwd); + assert(errnop); + + /* If the username is not valid, then we don't know it. Ideally libc would filter these for us + * anyway. We don't generate EINVAL here, because it isn't really out business to complain about + * invalid user names. */ + if (!valid_user_group_name(name, VALID_USER_RELAX)) + return NSS_STATUS_NOTFOUND; + + /* Synthesize entries for the root and nobody users, in case they are missing in /etc/passwd */ + if (getenv_bool_secure("SYSTEMD_NSS_BYPASS_SYNTHETIC") <= 0) { + + if (streq(name, root_passwd.pw_name)) { + *pwd = root_passwd; + return NSS_STATUS_SUCCESS; + } + + if (streq(name, nobody_passwd.pw_name)) { + if (!synthesize_nobody()) + return NSS_STATUS_NOTFOUND; + + *pwd = nobody_passwd; + return NSS_STATUS_SUCCESS; + } + + } else if (STR_IN_SET(name, root_passwd.pw_name, nobody_passwd.pw_name)) + return NSS_STATUS_NOTFOUND; + + status = userdb_getpwnam(name, pwd, buffer, buflen, &e); + if (IN_SET(status, NSS_STATUS_UNAVAIL, NSS_STATUS_TRYAGAIN)) { + UNPROTECT_ERRNO; + *errnop = e; + return status; + } + + return status; +} + +enum nss_status _nss_systemd_getpwuid_r( + uid_t uid, + struct passwd *pwd, + char *buffer, size_t buflen, + int *errnop) { + + enum nss_status status; + int e; + + PROTECT_ERRNO; + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + assert(pwd); + assert(errnop); + + if (!uid_is_valid(uid)) + return NSS_STATUS_NOTFOUND; + + /* Synthesize data for the root user and for nobody in case they are missing from /etc/passwd */ + if (getenv_bool_secure("SYSTEMD_NSS_BYPASS_SYNTHETIC") <= 0) { + + if (uid == root_passwd.pw_uid) { + *pwd = root_passwd; + return NSS_STATUS_SUCCESS; + } + + if (uid == nobody_passwd.pw_uid) { + if (!synthesize_nobody()) + return NSS_STATUS_NOTFOUND; + + *pwd = nobody_passwd; + return NSS_STATUS_SUCCESS; + } + + } else if (uid == root_passwd.pw_uid || uid == nobody_passwd.pw_uid) + return NSS_STATUS_NOTFOUND; + + status = userdb_getpwuid(uid, pwd, buffer, buflen, &e); + if (IN_SET(status, NSS_STATUS_UNAVAIL, NSS_STATUS_TRYAGAIN)) { + UNPROTECT_ERRNO; + *errnop = e; + return status; + } + + return status; +} + +#pragma GCC diagnostic ignored "-Wsizeof-pointer-memaccess" + +enum nss_status _nss_systemd_getgrnam_r( + const char *name, + struct group *gr, + char *buffer, size_t buflen, + int *errnop) { + + enum nss_status status; + int e; + + PROTECT_ERRNO; + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + assert(name); + assert(gr); + assert(errnop); + + if (!valid_user_group_name(name, VALID_USER_RELAX)) + return NSS_STATUS_NOTFOUND; + + /* Synthesize records for root and nobody, in case they are missing from /etc/group */ + if (getenv_bool_secure("SYSTEMD_NSS_BYPASS_SYNTHETIC") <= 0) { + + if (streq(name, root_group.gr_name)) { + *gr = root_group; + return NSS_STATUS_SUCCESS; + } + + if (streq(name, nobody_group.gr_name)) { + if (!synthesize_nobody()) + return NSS_STATUS_NOTFOUND; + + *gr = nobody_group; + return NSS_STATUS_SUCCESS; + } + + } else if (STR_IN_SET(name, root_group.gr_name, nobody_group.gr_name)) + return NSS_STATUS_NOTFOUND; + + status = userdb_getgrnam(name, gr, buffer, buflen, &e); + if (IN_SET(status, NSS_STATUS_UNAVAIL, NSS_STATUS_TRYAGAIN)) { + UNPROTECT_ERRNO; + *errnop = e; + return status; + } + + return status; +} + +enum nss_status _nss_systemd_getgrgid_r( + gid_t gid, + struct group *gr, + char *buffer, size_t buflen, + int *errnop) { + + enum nss_status status; + int e; + + PROTECT_ERRNO; + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + assert(gr); + assert(errnop); + + if (!gid_is_valid(gid)) + return NSS_STATUS_NOTFOUND; + + /* Synthesize records for root and nobody, in case they are missing from /etc/group */ + if (getenv_bool_secure("SYSTEMD_NSS_BYPASS_SYNTHETIC") <= 0) { + + if (gid == root_group.gr_gid) { + *gr = root_group; + return NSS_STATUS_SUCCESS; + } + + if (gid == nobody_group.gr_gid) { + if (!synthesize_nobody()) + return NSS_STATUS_NOTFOUND; + + *gr = nobody_group; + return NSS_STATUS_SUCCESS; + } + + } else if (gid == root_group.gr_gid || gid == nobody_group.gr_gid) + return NSS_STATUS_NOTFOUND; + + status = userdb_getgrgid(gid, gr, buffer, buflen, &e); + if (IN_SET(status, NSS_STATUS_UNAVAIL, NSS_STATUS_TRYAGAIN)) { + UNPROTECT_ERRNO; + *errnop = e; + return status; + } + + return status; +} + +static enum nss_status nss_systemd_endent(GetentData *p) { + PROTECT_ERRNO; + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + assert(p); + + _cleanup_(pthread_mutex_unlock_assertp) pthread_mutex_t *_l = NULL; + _l = pthread_mutex_lock_assert(&p->mutex); + + p->iterator = userdb_iterator_free(p->iterator); + p->by_membership = false; + + return NSS_STATUS_SUCCESS; +} + +enum nss_status _nss_systemd_endpwent(void) { + return nss_systemd_endent(&getpwent_data); +} + +enum nss_status _nss_systemd_endgrent(void) { + return nss_systemd_endent(&getgrent_data); +} + +enum nss_status _nss_systemd_setpwent(int stayopen) { + PROTECT_ERRNO; + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + if (_nss_systemd_is_blocked()) + return NSS_STATUS_NOTFOUND; + + _cleanup_(pthread_mutex_unlock_assertp) pthread_mutex_t *_l = NULL; + int r; + + _l = pthread_mutex_lock_assert(&getpwent_data.mutex); + + getpwent_data.iterator = userdb_iterator_free(getpwent_data.iterator); + getpwent_data.by_membership = false; + + /* Don't synthesize root/nobody when iterating. Let nss-files take care of that. If the two records + * are missing there, then that's fine, after all getpwent() is known to be possibly incomplete + * (think: LDAP/NIS type situations), and our synthesizing of root/nobody is a robustness fallback + * only, which matters for getpwnam()/getpwuid() primarily, which are the main NSS entrypoints to the + * user database. */ + r = userdb_all(nss_glue_userdb_flags() | USERDB_DONT_SYNTHESIZE, &getpwent_data.iterator); + return r < 0 ? NSS_STATUS_UNAVAIL : NSS_STATUS_SUCCESS; +} + +enum nss_status _nss_systemd_setgrent(int stayopen) { + PROTECT_ERRNO; + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + if (_nss_systemd_is_blocked()) + return NSS_STATUS_NOTFOUND; + + _cleanup_(pthread_mutex_unlock_assertp) pthread_mutex_t *_l = NULL; + int r; + + _l = pthread_mutex_lock_assert(&getgrent_data.mutex); + + getgrent_data.iterator = userdb_iterator_free(getgrent_data.iterator); + getpwent_data.by_membership = false; + + /* See _nss_systemd_setpwent() for an explanation why we use USERDB_DONT_SYNTHESIZE here */ + r = groupdb_all(nss_glue_userdb_flags() | USERDB_DONT_SYNTHESIZE, &getgrent_data.iterator); + return r < 0 ? NSS_STATUS_UNAVAIL : NSS_STATUS_SUCCESS; +} + +enum nss_status _nss_systemd_getpwent_r( + struct passwd *result, + char *buffer, size_t buflen, + int *errnop) { + + _cleanup_(user_record_unrefp) UserRecord *ur = NULL; + int r; + + PROTECT_ERRNO; + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + assert(result); + assert(errnop); + + if (_nss_systemd_is_blocked()) + return NSS_STATUS_NOTFOUND; + + _cleanup_(pthread_mutex_unlock_assertp) pthread_mutex_t *_l = NULL; + + _l = pthread_mutex_lock_assert(&getpwent_data.mutex); + + if (!getpwent_data.iterator) { + UNPROTECT_ERRNO; + *errnop = EHOSTDOWN; + return NSS_STATUS_UNAVAIL; + } + + r = userdb_iterator_get(getpwent_data.iterator, &ur); + if (r == -ESRCH) + return NSS_STATUS_NOTFOUND; + if (r < 0) { + UNPROTECT_ERRNO; + *errnop = -r; + return NSS_STATUS_UNAVAIL; + } + + r = nss_pack_user_record(ur, result, buffer, buflen); + if (r < 0) { + UNPROTECT_ERRNO; + *errnop = -r; + return NSS_STATUS_TRYAGAIN; + } + + return NSS_STATUS_SUCCESS; +} + +enum nss_status _nss_systemd_getgrent_r( + struct group *result, + char *buffer, size_t buflen, + int *errnop) { + + _cleanup_(group_record_unrefp) GroupRecord *gr = NULL; + _cleanup_free_ char **members = NULL; + int r; + + PROTECT_ERRNO; + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + assert(result); + assert(errnop); + + if (_nss_systemd_is_blocked()) + return NSS_STATUS_NOTFOUND; + + _cleanup_(pthread_mutex_unlock_assertp) pthread_mutex_t *_l = NULL; + + _l = pthread_mutex_lock_assert(&getgrent_data.mutex); + + if (!getgrent_data.iterator) { + UNPROTECT_ERRNO; + *errnop = EHOSTDOWN; + return NSS_STATUS_UNAVAIL; + } + + if (!getgrent_data.by_membership) { + r = groupdb_iterator_get(getgrent_data.iterator, &gr); + if (r == -ESRCH) { + /* So we finished iterating native groups now. Let's now continue with iterating + * native memberships, and generate additional group entries for any groups + * referenced there that are defined in NSS only. This means for those groups there + * will be two or more entries generated during iteration, but this is apparently how + * this is supposed to work, and what other implementations do too. Clients are + * supposed to merge the group records found during iteration automatically. */ + getgrent_data.iterator = userdb_iterator_free(getgrent_data.iterator); + + r = membershipdb_all(nss_glue_userdb_flags(), &getgrent_data.iterator); + if (r < 0) { + UNPROTECT_ERRNO; + *errnop = -r; + return NSS_STATUS_UNAVAIL; + } + + getgrent_data.by_membership = true; + } else if (r < 0) { + UNPROTECT_ERRNO; + *errnop = -r; + return NSS_STATUS_UNAVAIL; + } else if (!STR_IN_SET(gr->group_name, root_group.gr_name, nobody_group.gr_name)) { + r = membershipdb_by_group_strv(gr->group_name, nss_glue_userdb_flags(), &members); + if (r < 0) { + UNPROTECT_ERRNO; + *errnop = -r; + return NSS_STATUS_UNAVAIL; + } + } + } + + if (getgrent_data.by_membership) { + _cleanup_(_nss_systemd_unblockp) bool blocked = false; + + for (;;) { + _cleanup_free_ char *user_name = NULL, *group_name = NULL; + + r = membershipdb_iterator_get(getgrent_data.iterator, &user_name, &group_name); + if (r == -ESRCH) + return NSS_STATUS_NOTFOUND; + if (r < 0) { + UNPROTECT_ERRNO; + *errnop = -r; + return NSS_STATUS_UNAVAIL; + } + + if (STR_IN_SET(user_name, root_passwd.pw_name, nobody_passwd.pw_name)) + continue; + if (STR_IN_SET(group_name, root_group.gr_name, nobody_group.gr_name)) + continue; + + /* We are about to recursively call into NSS, let's make sure we disable recursion into our own code. */ + if (!blocked) { + r = _nss_systemd_block(true); + if (r < 0) { + UNPROTECT_ERRNO; + *errnop = -r; + return NSS_STATUS_UNAVAIL; + } + + blocked = true; + } + + r = nss_group_record_by_name(group_name, false, &gr); + if (r == -ESRCH) + continue; + if (r < 0) { + log_debug_errno(r, "Failed to do NSS check for group '%s', ignoring: %m", group_name); + continue; + } + + members = strv_new(user_name); + if (!members) { + UNPROTECT_ERRNO; + *errnop = ENOMEM; + return NSS_STATUS_TRYAGAIN; + } + + /* Note that we currently generate one group entry per user that is part of a + * group. It's a bit ugly, but equivalent to generating a single entry with a set of + * members in them. */ + break; + } + } + + r = nss_pack_group_record(gr, members, result, buffer, buflen); + if (r < 0) { + UNPROTECT_ERRNO; + *errnop = -r; + return NSS_STATUS_TRYAGAIN; + } + + return NSS_STATUS_SUCCESS; +} + +enum nss_status _nss_systemd_initgroups_dyn( + const char *user_name, + gid_t gid, + long *start, + long *size, + gid_t **groupsp, + long int limit, + int *errnop) { + + _cleanup_(userdb_iterator_freep) UserDBIterator *iterator = NULL; + bool any = false; + int r; + + PROTECT_ERRNO; + BLOCK_SIGNALS(NSS_SIGNALS_BLOCK); + + assert(user_name); + assert(start); + assert(size); + assert(groupsp); + assert(errnop); + + if (!valid_user_group_name(user_name, VALID_USER_RELAX)) + return NSS_STATUS_NOTFOUND; + + /* Don't allow extending these two special users, the same as we won't resolve them via getpwnam() */ + if (STR_IN_SET(user_name, root_passwd.pw_name, nobody_passwd.pw_name)) + return NSS_STATUS_NOTFOUND; + + if (_nss_systemd_is_blocked()) + return NSS_STATUS_NOTFOUND; + + r = membershipdb_by_user(user_name, nss_glue_userdb_flags(), &iterator); + if (r < 0) { + UNPROTECT_ERRNO; + *errnop = -r; + return NSS_STATUS_UNAVAIL; + } + + for (;;) { + _cleanup_(group_record_unrefp) GroupRecord *g = NULL; + _cleanup_free_ char *group_name = NULL; + + r = membershipdb_iterator_get(iterator, NULL, &group_name); + if (r == -ESRCH) + break; + if (r < 0) { + UNPROTECT_ERRNO; + *errnop = -r; + return NSS_STATUS_UNAVAIL; + } + + /* The group might be defined via traditional NSS only, hence let's do a full look-up without + * disabling NSS. This means we are operating recursively here. */ + + r = groupdb_by_name(group_name, (nss_glue_userdb_flags() & ~USERDB_AVOID_NSS) | USERDB_AVOID_SHADOW, &g); + if (r == -ESRCH) + continue; + if (r < 0) { + log_debug_errno(r, "Failed to resolve group '%s', ignoring: %m", group_name); + continue; + } + + if (g->gid == gid) + continue; + + if (*start >= *size) { + gid_t *new_groups; + long new_size; + + if (limit > 0 && *size >= limit) /* Reached the limit.? */ + break; + + if (*size > LONG_MAX/2) { /* Check for overflow */ + UNPROTECT_ERRNO; + *errnop = ENOMEM; + return NSS_STATUS_TRYAGAIN; + } + + new_size = *start * 2; + if (limit > 0 && new_size > limit) + new_size = limit; + + /* Enlarge buffer */ + new_groups = reallocarray(*groupsp, new_size, sizeof(**groupsp)); + if (!new_groups) { + UNPROTECT_ERRNO; + *errnop = ENOMEM; + return NSS_STATUS_TRYAGAIN; + } + + *groupsp = new_groups; + *size = new_size; + } + + (*groupsp)[(*start)++] = g->gid; + any = true; + } + + return any ? NSS_STATUS_SUCCESS : NSS_STATUS_NOTFOUND; +} + +static thread_local unsigned _blocked = 0; + +_public_ int _nss_systemd_block(bool b) { + + /* This blocks recursively: it's blocked for as many times this function is called with `true` until + * it is called an equal time with `false`. */ + + if (b) { + if (_blocked >= UINT_MAX) + return -EOVERFLOW; + + _blocked++; + } else { + if (_blocked <= 0) + return -EOVERFLOW; + + _blocked--; + } + + return b; /* Return what is passed in, i.e. the new state from the PoV of the caller */ +} + +_public_ bool _nss_systemd_is_blocked(void) { + return _blocked > 0; +} |