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v260
src/userdb/userwork.c
597 строк
24 KB
Luca Boccassi
userdbd: avoid sending gshadow hash to unprivileged callers via varlink
25 фев 2026, 04:52
25 фев 2026, 04:52
1012c6c
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/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include <poll.h> #include "sd-daemon.h" #include "sd-varlink.h" #include "alloc-util.h" #include "argv-util.h" #include "env-util.h" #include "errno-util.h" #include "fd-util.h" #include "group-record.h" #include "io-util.h" #include "json-util.h" #include "main-func.h" #include "pidref.h" #include "string-util.h" #include "time-util.h" #include "user-record.h" #include "user-util.h" #include "userdb.h" #include "varlink-io.systemd.UserDatabase.h" #include "varlink-util.h" #define ITERATIONS_MAX 64U #define RUNTIME_MAX_USEC (5 * USEC_PER_MINUTE) #define PRESSURE_SLEEP_TIME_USEC (50 * USEC_PER_MSEC) #define CONNECTION_IDLE_USEC (15 * USEC_PER_SEC) #define LISTEN_IDLE_USEC (90 * USEC_PER_SEC) typedef struct LookupParameters { const char *name; union { uid_t uid; gid_t gid; }; const char *service; UserDBMatch match; } LookupParameters; static void lookup_parameters_done(LookupParameters *p) { assert(p); userdb_match_done(&p->match); } static int add_nss_service(sd_json_variant **v) { _cleanup_(sd_json_variant_unrefp) sd_json_variant *status = NULL, *z = NULL; sd_id128_t mid; int r; assert(v); /* Patch in service field if it's missing. The assumption here is that this field is unset only for * NSS records */ if (sd_json_variant_by_key(*v, "service")) return 0; r = sd_id128_get_machine(&mid); if (r < 0) return r; status = sd_json_variant_ref(sd_json_variant_by_key(*v, "status")); z = sd_json_variant_ref(sd_json_variant_by_key(status, SD_ID128_TO_STRING(mid))); if (sd_json_variant_by_key(z, "service")) return 0; r = sd_json_variant_set_field_string(&z, "service", "io.systemd.NameServiceSwitch"); if (r < 0) return r; r = sd_json_variant_set_field(&status, SD_ID128_TO_STRING(mid), z); if (r < 0) return r; return sd_json_variant_set_field(v, "status", status); } static int build_user_json(sd_varlink *link, UserRecord *ur, sd_json_variant **ret) { _cleanup_(user_record_unrefp) UserRecord *stripped = NULL; _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL; UserRecordLoadFlags flags; uid_t peer_uid; bool trusted; int r; assert(ur); assert(ret); r = sd_varlink_get_peer_uid(link, &peer_uid); if (r < 0) { log_debug_errno(r, "Unable to query peer UID, ignoring: %m"); trusted = false; } else trusted = peer_uid == 0 || peer_uid == ur->uid; flags = USER_RECORD_REQUIRE_REGULAR|USER_RECORD_ALLOW_PER_MACHINE|USER_RECORD_ALLOW_BINDING|USER_RECORD_STRIP_SECRET|USER_RECORD_ALLOW_STATUS|USER_RECORD_ALLOW_SIGNATURE|USER_RECORD_PERMISSIVE; if (trusted) flags |= USER_RECORD_ALLOW_PRIVILEGED; else flags |= USER_RECORD_STRIP_PRIVILEGED; r = user_record_clone(ur, flags, &stripped); if (r < 0) return r; stripped->incomplete = ur->incomplete || (FLAGS_SET(ur->mask, USER_RECORD_PRIVILEGED) && !FLAGS_SET(stripped->mask, USER_RECORD_PRIVILEGED)); v = sd_json_variant_ref(stripped->json); r = add_nss_service(&v); if (r < 0) return r; return sd_json_buildo( ret, SD_JSON_BUILD_PAIR_VARIANT("record", v), SD_JSON_BUILD_PAIR_BOOLEAN("incomplete", stripped->incomplete)); } static int userdb_flags_from_service(sd_varlink *link, const char *service, UserDBFlags *ret) { assert(link); assert(ret); if (streq_ptr(service, "io.systemd.NameServiceSwitch")) *ret = USERDB_NSS_ONLY|USERDB_AVOID_MULTIPLEXER; else if (streq_ptr(service, "io.systemd.DropIn")) *ret = USERDB_DROPIN_ONLY|USERDB_AVOID_MULTIPLEXER; else if (streq_ptr(service, "io.systemd.Multiplexer")) *ret = USERDB_AVOID_MULTIPLEXER; else return sd_varlink_error(link, "io.systemd.UserDatabase.BadService", NULL); return 0; } static int vl_method_get_user_record(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) { static const sd_json_dispatch_field dispatch_table[] = { { "uid", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uid_gid, offsetof(LookupParameters, uid), 0 }, { "userName", SD_JSON_VARIANT_STRING, json_dispatch_const_user_group_name, offsetof(LookupParameters, name), SD_JSON_RELAX }, { "service", SD_JSON_VARIANT_STRING, sd_json_dispatch_const_string, offsetof(LookupParameters, service), 0 }, { "fuzzyNames", SD_JSON_VARIANT_ARRAY, sd_json_dispatch_strv, offsetof(LookupParameters, match.fuzzy_names), 0 }, { "dispositionMask", SD_JSON_VARIANT_ARRAY, json_dispatch_dispositions_mask, offsetof(LookupParameters, match.disposition_mask), 0 }, { "uidMin", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uid_gid, offsetof(LookupParameters, match.uid_min), 0 }, { "uidMax", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uid_gid, offsetof(LookupParameters, match.uid_max), 0 }, { "uuid", SD_JSON_VARIANT_STRING, sd_json_dispatch_id128, offsetof(LookupParameters, match.uuid), 0 }, {} }; _cleanup_(user_record_unrefp) UserRecord *hr = NULL; _cleanup_(lookup_parameters_done) LookupParameters p = { .uid = UID_INVALID, .match = USERDB_MATCH_NULL, }; UserDBFlags userdb_flags; int r; assert(parameters); r = sd_varlink_dispatch(link, parameters, dispatch_table, &p); if (r != 0) return r; r = userdb_flags_from_service(link, p.service, &userdb_flags); if (r != 0) /* return value of < 0 means error (as usual); > 0 means 'already processed and replied, * we are done'; == 0 means 'not processed, caller should process now' */ return r; r = varlink_set_sentinel(link, "io.systemd.UserDatabase.NoRecordFound"); if (r < 0) return r; if (uid_is_valid(p.uid)) r = userdb_by_uid(p.uid, &p.match, userdb_flags, &hr); else if (p.name) r = userdb_by_name(p.name, &p.match, userdb_flags, &hr); else { _cleanup_(userdb_iterator_freep) UserDBIterator *iterator = NULL; r = userdb_all(&p.match, userdb_flags, &iterator); if (IN_SET(r, -ESRCH, -ENOLINK)) /* We turn off Varlink lookups in various cases (e.g. in case we only enable DropIn * backend) — this might make userdb_all return ENOLINK (which indicates that varlink * was off and no other suitable source or entries were found). Let's hide this * implementation detail and always return NoRecordFound in this case, since from a * client's perspective it's irrelevant if there was no entry at all or just not on * the service that the query was limited to. */ return 0; if (r < 0) return r; for (;;) { _cleanup_(user_record_unrefp) UserRecord *z = NULL; r = userdb_iterator_get(iterator, &p.match, &z); if (r == -ESRCH) break; if (r < 0) return r; _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL; r = build_user_json(link, z, &v); if (r < 0) return r; r = sd_varlink_reply(link, v); if (r < 0) return r; } return 0; } if (r == -ESRCH) return 0; if (r == -ENOEXEC) return sd_varlink_error(link, "io.systemd.UserDatabase.NonMatchingRecordFound", NULL); if (r < 0) { log_debug_errno(r, "User lookup failed abnormally: %m"); return sd_varlink_error(link, "io.systemd.UserDatabase.ServiceNotAvailable", NULL); } if ((uid_is_valid(p.uid) && hr->uid != p.uid) || (p.name && !user_record_matches_user_name(hr, p.name))) return sd_varlink_error(link, "io.systemd.UserDatabase.ConflictingRecordFound", NULL); _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL; r = build_user_json(link, hr, &v); if (r < 0) return r; return sd_varlink_reply(link, v); } static int build_group_json(sd_varlink *link, GroupRecord *gr, sd_json_variant **ret) { _cleanup_(group_record_unrefp) GroupRecord *stripped = NULL; _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL; UserRecordLoadFlags flags; uid_t peer_uid; bool trusted; int r; assert(gr); assert(ret); r = sd_varlink_get_peer_uid(link, &peer_uid); if (r < 0) { log_debug_errno(r, "Unable to query peer UID, ignoring: %m"); trusted = false; } else trusted = peer_uid == 0; flags = USER_RECORD_REQUIRE_REGULAR|USER_RECORD_ALLOW_PER_MACHINE|USER_RECORD_ALLOW_BINDING|USER_RECORD_STRIP_SECRET|USER_RECORD_ALLOW_STATUS|USER_RECORD_ALLOW_SIGNATURE|USER_RECORD_PERMISSIVE; if (trusted) flags |= USER_RECORD_ALLOW_PRIVILEGED; else flags |= USER_RECORD_STRIP_PRIVILEGED; r = group_record_clone(gr, flags, &stripped); if (r < 0) return r; stripped->incomplete = gr->incomplete || (FLAGS_SET(gr->mask, USER_RECORD_PRIVILEGED) && !FLAGS_SET(stripped->mask, USER_RECORD_PRIVILEGED)); v = sd_json_variant_ref(stripped->json); r = add_nss_service(&v); if (r < 0) return r; return sd_json_buildo( ret, SD_JSON_BUILD_PAIR_VARIANT("record", v), SD_JSON_BUILD_PAIR_BOOLEAN("incomplete", stripped->incomplete)); } static int vl_method_get_group_record(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) { static const sd_json_dispatch_field dispatch_table[] = { { "gid", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uid_gid, offsetof(LookupParameters, gid), 0 }, { "groupName", SD_JSON_VARIANT_STRING, json_dispatch_const_user_group_name, offsetof(LookupParameters, name), SD_JSON_RELAX }, { "service", SD_JSON_VARIANT_STRING, sd_json_dispatch_const_string, offsetof(LookupParameters, service), 0 }, { "fuzzyNames", SD_JSON_VARIANT_ARRAY, sd_json_dispatch_strv, offsetof(LookupParameters, match.fuzzy_names), 0 }, { "dispositionMask", SD_JSON_VARIANT_ARRAY, json_dispatch_dispositions_mask, offsetof(LookupParameters, match.disposition_mask), 0 }, { "gidMin", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uid_gid, offsetof(LookupParameters, match.gid_min), 0 }, { "gidMax", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uid_gid, offsetof(LookupParameters, match.gid_max), 0 }, { "uuid", SD_JSON_VARIANT_STRING, sd_json_dispatch_id128, offsetof(LookupParameters, match.uuid), 0 }, {} }; _cleanup_(group_record_unrefp) GroupRecord *g = NULL; _cleanup_(lookup_parameters_done) LookupParameters p = { .gid = GID_INVALID, .match = USERDB_MATCH_NULL, }; UserDBFlags userdb_flags; int r; assert(parameters); r = sd_varlink_dispatch(link, parameters, dispatch_table, &p); if (r != 0) return r; r = userdb_flags_from_service(link, p.service, &userdb_flags); if (r != 0) return r; r = varlink_set_sentinel(link, "io.systemd.UserDatabase.NoRecordFound"); if (r < 0) return r; if (gid_is_valid(p.gid)) r = groupdb_by_gid(p.gid, &p.match, userdb_flags, &g); else if (p.name) r = groupdb_by_name(p.name, &p.match, userdb_flags, &g); else { _cleanup_(userdb_iterator_freep) UserDBIterator *iterator = NULL; r = groupdb_all(&p.match, userdb_flags, &iterator); if (IN_SET(r, -ESRCH, -ENOLINK)) return 0; if (r < 0) return r; for (;;) { _cleanup_(group_record_unrefp) GroupRecord *z = NULL; r = groupdb_iterator_get(iterator, &p.match, &z); if (r == -ESRCH) break; if (r < 0) return r; _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL; r = build_group_json(link, z, &v); if (r < 0) return r; r = sd_varlink_reply(link, v); if (r < 0) return r; } return 0; } if (r == -ESRCH) return 0; if (r == -ENOEXEC) return sd_varlink_error(link, "io.systemd.UserDatabase.NonMatchingRecordFound", NULL); if (r < 0) { log_debug_errno(r, "Group lookup failed abnormally: %m"); return sd_varlink_error(link, "io.systemd.UserDatabase.ServiceNotAvailable", NULL); } if ((uid_is_valid(p.gid) && g->gid != p.gid) || (p.name && !group_record_matches_group_name(g, p.name))) return sd_varlink_error(link, "io.systemd.UserDatabase.ConflictingRecordFound", NULL); _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL; r = build_group_json(link, g, &v); if (r < 0) return r; return sd_varlink_reply(link, v); } typedef struct MembershipLookupParameters { const char *user_name; const char *group_name; const char *service; } MembershipLookupParameters; static int vl_method_get_memberships(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) { static const sd_json_dispatch_field dispatch_table[] = { { "userName", SD_JSON_VARIANT_STRING, json_dispatch_const_user_group_name, offsetof(MembershipLookupParameters, user_name), SD_JSON_RELAX }, { "groupName", SD_JSON_VARIANT_STRING, json_dispatch_const_user_group_name, offsetof(MembershipLookupParameters, group_name), SD_JSON_RELAX }, { "service", SD_JSON_VARIANT_STRING, sd_json_dispatch_const_string, offsetof(MembershipLookupParameters, service), 0 }, {} }; _cleanup_(userdb_iterator_freep) UserDBIterator *iterator = NULL; MembershipLookupParameters p = {}; UserDBFlags userdb_flags; int r; assert(parameters); r = sd_varlink_dispatch(link, parameters, dispatch_table, &p); if (r != 0) return r; r = userdb_flags_from_service(link, p.service, &userdb_flags); if (r != 0) return r; r = varlink_set_sentinel(link, "io.systemd.UserDatabase.NoRecordFound"); if (r < 0) return r; if (p.group_name) r = membershipdb_by_group(p.group_name, userdb_flags, &iterator); else if (p.user_name) r = membershipdb_by_user(p.user_name, userdb_flags, &iterator); else r = membershipdb_all(userdb_flags, &iterator); if (IN_SET(r, -ESRCH, -ENOLINK)) return 0; if (r < 0) return r; for (;;) { _cleanup_free_ char *user_name = NULL, *group_name = NULL; r = membershipdb_iterator_get(iterator, &user_name, &group_name); if (r == -ESRCH) break; if (r < 0) return r; /* If both group + user are specified do a-posteriori filtering */ if (p.group_name && p.user_name && !streq(group_name, p.group_name)) continue; r = sd_varlink_replybo( link, SD_JSON_BUILD_PAIR_STRING("userName", user_name), SD_JSON_BUILD_PAIR_STRING("groupName", group_name)); if (r < 0) return r; } return 0; } static int process_connection(sd_varlink_server *server, int _fd) { _cleanup_close_ int fd = TAKE_FD(_fd); /* always take possession */ _cleanup_(sd_varlink_close_unrefp) sd_varlink *vl = NULL; int r; assert(server); assert(fd >= 0); r = sd_varlink_server_add_connection(server, fd, &vl); if (r < 0) return log_error_errno(r, "Failed to add connection: %m"); TAKE_FD(fd); vl = sd_varlink_ref(vl); for (;;) { r = sd_varlink_process(vl); if (r == -ENOTCONN) { log_debug("Connection terminated."); break; } if (r < 0) return log_error_errno(r, "Failed to process connection: %m"); if (r > 0) continue; r = sd_varlink_wait(vl, CONNECTION_IDLE_USEC); if (r < 0) return log_error_errno(r, "Failed to wait for connection events: %m"); if (r == 0) break; } return 0; } static int run(int argc, char *argv[]) { usec_t start_time, listen_idle_usec, last_busy_usec = USEC_INFINITY; _cleanup_(sd_varlink_server_unrefp) sd_varlink_server *server = NULL; _cleanup_(pidref_done) PidRef parent = PIDREF_NULL; unsigned n_iterations = 0; int m, listen_fd, r; log_setup(); m = sd_listen_fds(false); if (m < 0) return log_error_errno(m, "Failed to determine number of listening fds: %m"); if (m == 0) return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "No socket to listen on received."); if (m > 1) return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Worker can only listen on a single socket at a time."); listen_fd = SD_LISTEN_FDS_START; r = fd_nonblock(listen_fd, false); if (r < 0) return log_error_errno(r, "Failed to turn off non-blocking mode for listening socket: %m"); r = varlink_server_new(&server, 0, NULL); if (r < 0) return log_error_errno(r, "Failed to allocate varlink server: %m"); r = sd_varlink_server_add_interface(server, &vl_interface_io_systemd_UserDatabase); if (r < 0) return log_error_errno(r, "Failed to add UserDatabase interface to varlink server: %m"); r = sd_varlink_server_bind_method_many( server, "io.systemd.UserDatabase.GetUserRecord", vl_method_get_user_record, "io.systemd.UserDatabase.GetGroupRecord", vl_method_get_group_record, "io.systemd.UserDatabase.GetMemberships", vl_method_get_memberships); if (r < 0) return log_error_errno(r, "Failed to bind methods: %m"); r = getenv_bool("USERDB_FIXED_WORKER"); if (r < 0) return log_error_errno(r, "Failed to parse USERDB_FIXED_WORKER: %m"); listen_idle_usec = r ? USEC_INFINITY : LISTEN_IDLE_USEC; r = userdb_block_nss_systemd(true); if (r < 0) return log_error_errno(r, "Failed to disable userdb NSS compatibility: %m"); r = pidref_set_parent(&parent); if (r < 0) return log_error_errno(r, "Failed to acquire pidfd of parent process: %m"); if (parent.pid == 1) /* We got reparented away from userdbd? */ return log_error_errno(SYNTHETIC_ERRNO(ESRCH), "Parent already died, exiting."); start_time = now(CLOCK_MONOTONIC); for (;;) { _cleanup_close_ int fd = -EBADF; usec_t n; /* Exit the worker in regular intervals, to flush out all memory use */ if (n_iterations++ > ITERATIONS_MAX) { log_debug("Exiting worker, processed %u iterations, that's enough.", n_iterations); break; } n = now(CLOCK_MONOTONIC); if (n >= usec_add(start_time, RUNTIME_MAX_USEC)) { log_debug("Exiting worker, ran for %s, that's enough.", FORMAT_TIMESPAN(usec_sub_unsigned(n, start_time), 0)); break; } if (last_busy_usec == USEC_INFINITY) last_busy_usec = n; else if (listen_idle_usec != USEC_INFINITY && n >= usec_add(last_busy_usec, listen_idle_usec)) { log_debug("Exiting worker, been idle for %s.", FORMAT_TIMESPAN(usec_sub_unsigned(n, last_busy_usec), 0)); break; } (void) rename_process("systemd-userwork: waiting..."); fd = RET_NERRNO(accept4(listen_fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC)); (void) rename_process("systemd-userwork: processing..."); if (fd == -EAGAIN) continue; /* The listening socket has SO_RECVTIMEO set, hence a timeout is expected * after a while, let's check if it's time to exit though. */ if (fd == -EINTR) continue; /* Might be that somebody attached via strace, let's just continue in that * case */ if (fd < 0) return log_error_errno(fd, "Failed to accept() from listening socket: %m"); if (now(CLOCK_MONOTONIC) <= usec_add(n, PRESSURE_SLEEP_TIME_USEC)) { /* We only slept a very short time? If so, let's see if there are more sockets * pending, and if so, let's ask our parent for more workers */ r = fd_wait_for_event(listen_fd, POLLIN, 0); if (r < 0) return log_error_errno(r, "Failed to test for POLLIN on listening socket: %m"); if (FLAGS_SET(r, POLLIN)) { r = pidref_kill(&parent, SIGUSR2); if (r == -ESRCH) return log_error_errno(r, "Parent already died?"); if (r < 0) return log_error_errno(r, "Failed to send SIGUSR2 signal to parent: %m"); } } (void) process_connection(server, TAKE_FD(fd)); last_busy_usec = USEC_INFINITY; } return 0; } DEFINE_MAIN_FUNCTION(run);