Adding upstream version 255.4.upstream/255.4

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

6 files changed, 2346 insertions, 0 deletions

diff --git a/src/userdb/meson.build b/src/userdb/meson.build
new file mode 100644
index 0000000..2d701c8
--- /dev/null
+++ b/src/userdb/meson.build
@@ -0,0 +1,25 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+executables += [
+        libexec_template + {
+                'name' : 'systemd-userwork',
+                'conditions' : ['ENABLE_USERDB'],
+                'sources' : files('userwork.c'),
+                'dependencies' : threads,
+        },
+        libexec_template + {
+                'name' : 'systemd-userdbd',
+                'conditions' : ['ENABLE_USERDB'],
+                'sources' : files(
+                        'userdbd-manager.c',
+                        'userdbd.c',
+                ),
+                'dependencies' : threads,
+        },
+        executable_template + {
+                'name' : 'userdbctl',
+                'conditions' : ['ENABLE_USERDB'],
+                'sources' : files('userdbctl.c'),
+                'dependencies' : threads,
+        },
+]
diff --git a/src/userdb/userdbctl.c b/src/userdb/userdbctl.c
new file mode 100644
index 0000000..a7db3fb
--- /dev/null
+++ b/src/userdb/userdbctl.c
@@ -0,0 +1,1334 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <getopt.h>
+#include <utmp.h>
+
+#include "build.h"
+#include "dirent-util.h"
+#include "errno-list.h"
+#include "escape.h"
+#include "fd-util.h"
+#include "format-table.h"
+#include "format-util.h"
+#include "main-func.h"
+#include "pager.h"
+#include "parse-argument.h"
+#include "parse-util.h"
+#include "pretty-print.h"
+#include "socket-util.h"
+#include "strv.h"
+#include "terminal-util.h"
+#include "uid-range.h"
+#include "user-record-show.h"
+#include "user-util.h"
+#include "userdb.h"
+#include "verbs.h"
+
+static enum {
+        OUTPUT_CLASSIC,
+        OUTPUT_TABLE,
+        OUTPUT_FRIENDLY,
+        OUTPUT_JSON,
+        _OUTPUT_INVALID = -EINVAL,
+} arg_output = _OUTPUT_INVALID;
+
+static PagerFlags arg_pager_flags = 0;
+static bool arg_legend = true;
+static char** arg_services = NULL;
+static UserDBFlags arg_userdb_flags = 0;
+static JsonFormatFlags arg_json_format_flags = JSON_FORMAT_OFF;
+static bool arg_chain = false;
+
+STATIC_DESTRUCTOR_REGISTER(arg_services, strv_freep);
+
+static const char *user_disposition_to_color(UserDisposition d) {
+        assert(d >= 0);
+        assert(d < _USER_DISPOSITION_MAX);
+
+        switch (d) {
+        case USER_INTRINSIC:
+                return ansi_red();
+
+        case USER_SYSTEM:
+        case USER_DYNAMIC:
+                return ansi_green();
+
+        case USER_CONTAINER:
+                return ansi_cyan();
+
+        case USER_RESERVED:
+                return ansi_red();
+
+        default:
+                return NULL;
+        }
+}
+
+static int show_user(UserRecord *ur, Table *table) {
+        int r;
+
+        assert(ur);
+
+        switch (arg_output) {
+
+        case OUTPUT_CLASSIC:
+                if (!uid_is_valid(ur->uid))
+                        break;
+
+                printf("%s:x:" UID_FMT ":" GID_FMT ":%s:%s:%s\n",
+                       ur->user_name,
+                       ur->uid,
+                       user_record_gid(ur),
+                       strempty(user_record_real_name(ur)),
+                       user_record_home_directory(ur),
+                       user_record_shell(ur));
+
+                break;
+
+        case OUTPUT_JSON:
+                json_variant_dump(ur->json, arg_json_format_flags, NULL, 0);
+                break;
+
+        case OUTPUT_FRIENDLY:
+                user_record_show(ur, true);
+
+                if (ur->incomplete) {
+                        fflush(stdout);
+                        log_warning("Warning: lacking rights to acquire privileged fields of user record of '%s', output incomplete.", ur->user_name);
+                }
+
+                break;
+
+        case OUTPUT_TABLE: {
+                UserDisposition d;
+
+                assert(table);
+                d = user_record_disposition(ur);
+
+                r = table_add_many(
+                                table,
+                                TABLE_STRING, "",
+                                TABLE_STRING, ur->user_name,
+                                TABLE_SET_COLOR, user_disposition_to_color(d),
+                                TABLE_STRING, user_disposition_to_string(d),
+                                TABLE_UID, ur->uid,
+                                TABLE_GID, user_record_gid(ur),
+                                TABLE_STRING, empty_to_null(ur->real_name),
+                                TABLE_STRING, user_record_home_directory(ur),
+                                TABLE_STRING, user_record_shell(ur),
+                                TABLE_INT, 0);
+                if (r < 0)
+                        return table_log_add_error(r);
+
+                break;
+        }
+
+        default:
+                assert_not_reached();
+        }
+
+        return 0;
+}
+
+static const struct {
+        uid_t first, last;
+        const char *name;
+        UserDisposition disposition;
+} uid_range_table[] = {
+        {
+                .first = 1,
+                .last = SYSTEM_UID_MAX,
+                .name = "system",
+                .disposition = USER_SYSTEM,
+        },
+        {
+                .first = DYNAMIC_UID_MIN,
+                .last = DYNAMIC_UID_MAX,
+                .name = "dynamic system",
+                .disposition = USER_DYNAMIC,
+        },
+        {
+                .first = CONTAINER_UID_BASE_MIN,
+                .last = CONTAINER_UID_BASE_MAX,
+                .name = "container",
+                .disposition = USER_CONTAINER,
+        },
+#if ENABLE_HOMED
+        {
+                .first = HOME_UID_MIN,
+                .last = HOME_UID_MAX,
+                .name = "systemd-homed",
+                .disposition = USER_REGULAR,
+        },
+#endif
+        {
+                .first = MAP_UID_MIN,
+                .last = MAP_UID_MAX,
+                .name = "mapped",
+                .disposition = USER_REGULAR,
+        },
+};
+
+static int table_add_uid_boundaries(Table *table, const UidRange *p) {
+        int r;
+
+        assert(table);
+
+        for (size_t i = 0; i < ELEMENTSOF(uid_range_table); i++) {
+                _cleanup_free_ char *name = NULL, *comment = NULL;
+
+                if (!uid_range_covers(p, uid_range_table[i].first, uid_range_table[i].last - uid_range_table[i].first + 1))
+                        continue;
+
+                name = strjoin(special_glyph(SPECIAL_GLYPH_ARROW_DOWN),
+                               " begin ", uid_range_table[i].name, " users ",
+                               special_glyph(SPECIAL_GLYPH_ARROW_DOWN));
+                if (!name)
+                        return log_oom();
+
+                comment = strjoin("First ", uid_range_table[i].name, " user");
+                if (!comment)
+                        return log_oom();
+
+                r = table_add_many(
+                                table,
+                                TABLE_STRING, special_glyph(SPECIAL_GLYPH_TREE_TOP),
+                                TABLE_STRING, name,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_STRING, user_disposition_to_string(uid_range_table[i].disposition),
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_UID, uid_range_table[i].first,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_EMPTY,
+                                TABLE_STRING, comment,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_EMPTY,
+                                TABLE_EMPTY,
+                                TABLE_INT, -1); /* sort before any other entry with the same UID */
+                if (r < 0)
+                        return table_log_add_error(r);
+
+                free(name);
+                name = strjoin(special_glyph(SPECIAL_GLYPH_ARROW_UP),
+                               " end ", uid_range_table[i].name, " users ",
+                               special_glyph(SPECIAL_GLYPH_ARROW_UP));
+                if (!name)
+                        return log_oom();
+
+                free(comment);
+                comment = strjoin("Last ", uid_range_table[i].name, " user");
+                if (!comment)
+                        return log_oom();
+
+                r = table_add_many(
+                                table,
+                                TABLE_STRING, special_glyph(SPECIAL_GLYPH_TREE_RIGHT),
+                                TABLE_STRING, name,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_STRING, user_disposition_to_string(uid_range_table[i].disposition),
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_UID, uid_range_table[i].last,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_EMPTY,
+                                TABLE_STRING, comment,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_EMPTY,
+                                TABLE_EMPTY,
+                                TABLE_INT, 1); /* sort after any other entry with the same UID */
+                if (r < 0)
+                        return table_log_add_error(r);
+        }
+
+        return ELEMENTSOF(uid_range_table) * 2;
+}
+
+static int add_unavailable_uid(Table *table, uid_t start, uid_t end) {
+        _cleanup_free_ char *name = NULL;
+        int r;
+
+        assert(table);
+        assert(start <= end);
+
+        name = strjoin(special_glyph(SPECIAL_GLYPH_ARROW_DOWN),
+                       " begin unavailable users ",
+                       special_glyph(SPECIAL_GLYPH_ARROW_DOWN));
+        if (!name)
+                return log_oom();
+
+        r = table_add_many(
+                        table,
+                        TABLE_STRING, special_glyph(SPECIAL_GLYPH_TREE_TOP),
+                        TABLE_STRING, name,
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_EMPTY,
+                        TABLE_UID, start,
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_EMPTY,
+                        TABLE_STRING, "First unavailable user",
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_EMPTY,
+                        TABLE_EMPTY,
+                        TABLE_INT, -1); /* sort before an other entry with the same UID */
+        if (r < 0)
+                return table_log_add_error(r);
+
+        free(name);
+        name = strjoin(special_glyph(SPECIAL_GLYPH_ARROW_UP),
+                       " end unavailable users ",
+                       special_glyph(SPECIAL_GLYPH_ARROW_UP));
+        if (!name)
+                return log_oom();
+
+        r = table_add_many(
+                        table,
+                        TABLE_STRING, special_glyph(SPECIAL_GLYPH_TREE_RIGHT),
+                        TABLE_STRING, name,
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_EMPTY,
+                        TABLE_UID, end,
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_EMPTY,
+                        TABLE_STRING, "Last unavailable user",
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_EMPTY,
+                        TABLE_EMPTY,
+                        TABLE_INT, 1); /* sort after any other entry with the same UID */
+        if (r < 0)
+                return table_log_add_error(r);
+
+        return 2;
+}
+
+static int table_add_uid_map(
+                Table *table,
+                const UidRange *p,
+                int (*add_unavailable)(Table *t, uid_t start, uid_t end)) {
+
+        uid_t focus = 0;
+        int n_added = 0, r;
+
+        assert(table);
+        assert(add_unavailable);
+
+        for (size_t i = 0; p && i < p->n_entries; i++) {
+                UidRangeEntry *x = p->entries + i;
+
+                if (focus < x->start) {
+                        r = add_unavailable(table, focus, x->start-1);
+                        if (r < 0)
+                                return r;
+
+                        n_added += r;
+                }
+
+                if (x->start > UINT32_MAX - x->nr) { /* overflow check */
+                        focus = UINT32_MAX;
+                        break;
+                }
+
+                focus = x->start + x->nr;
+        }
+
+        if (focus < UINT32_MAX-1) {
+                r = add_unavailable(table, focus, UINT32_MAX-1);
+                if (r < 0)
+                        return r;
+
+                n_added += r;
+        }
+
+        return n_added;
+}
+
+static int display_user(int argc, char *argv[], void *userdata) {
+        _cleanup_(table_unrefp) Table *table = NULL;
+        bool draw_separator = false;
+        int ret = 0, r;
+
+        if (arg_output < 0)
+                arg_output = argc > 1 ? OUTPUT_FRIENDLY : OUTPUT_TABLE;
+
+        if (arg_output == OUTPUT_TABLE) {
+                table = table_new(" ", "name", "disposition", "uid", "gid", "realname", "home", "shell", "order");
+                if (!table)
+                        return log_oom();
+
+                (void) table_set_align_percent(table, table_get_cell(table, 0, 3), 100);
+                (void) table_set_align_percent(table, table_get_cell(table, 0, 4), 100);
+                table_set_ersatz_string(table, TABLE_ERSATZ_DASH);
+                (void) table_set_sort(table, (size_t) 3, (size_t) 8);
+                (void) table_set_display(table, (size_t) 0, (size_t) 1, (size_t) 2, (size_t) 3, (size_t) 4, (size_t) 5, (size_t) 6, (size_t) 7);
+        }
+
+        if (argc > 1)
+                STRV_FOREACH(i, argv + 1) {
+                        _cleanup_(user_record_unrefp) UserRecord *ur = NULL;
+                        uid_t uid;
+
+                        if (parse_uid(*i, &uid) >= 0)
+                                r = userdb_by_uid(uid, arg_userdb_flags, &ur);
+                        else
+                                r = userdb_by_name(*i, arg_userdb_flags, &ur);
+                        if (r < 0) {
+                                if (r == -ESRCH)
+                                        log_error_errno(r, "User %s does not exist.", *i);
+                                else if (r == -EHOSTDOWN)
+                                        log_error_errno(r, "Selected user database service is not available for this request.");
+                                else
+                                        log_error_errno(r, "Failed to find user %s: %m", *i);
+
+                                if (ret >= 0)
+                                        ret = r;
+                        } else {
+                                if (draw_separator && arg_output == OUTPUT_FRIENDLY)
+                                        putchar('\n');
+
+                                r = show_user(ur, table);
+                                if (r < 0)
+                                        return r;
+
+                                draw_separator = true;
+                        }
+                }
+        else {
+                _cleanup_(userdb_iterator_freep) UserDBIterator *iterator = NULL;
+
+                r = userdb_all(arg_userdb_flags, &iterator);
+                if (r == -ENOLINK) /* ENOLINK → Didn't find answer without Varlink, and didn't try Varlink because was configured to off. */
+                        log_debug_errno(r, "No entries found. (Didn't check via Varlink.)");
+                else if (r == -ESRCH) /* ESRCH → Couldn't find any suitable entry, but we checked all sources */
+                        log_debug_errno(r, "No entries found.");
+                else if (r < 0)
+                        return log_error_errno(r, "Failed to enumerate users: %m");
+                else {
+                        for (;;) {
+                                _cleanup_(user_record_unrefp) UserRecord *ur = NULL;
+
+                                r = userdb_iterator_get(iterator, &ur);
+                                if (r == -ESRCH)
+                                        break;
+                                if (r == -EHOSTDOWN)
+                                        return log_error_errno(r, "Selected user database service is not available for this request.");
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed acquire next user: %m");
+
+                                if (draw_separator && arg_output == OUTPUT_FRIENDLY)
+                                        putchar('\n');
+
+                                r = show_user(ur, table);
+                                if (r < 0)
+                                        return r;
+
+                                draw_separator = true;
+                        }
+                }
+        }
+
+        if (table) {
+                _cleanup_(uid_range_freep) UidRange *uid_range = NULL;
+                int boundary_lines, uid_map_lines;
+
+                r = uid_range_load_userns(&uid_range, "/proc/self/uid_map");
+                if (r < 0)
+                        log_debug_errno(r, "Failed to load /proc/self/uid_map, ignoring: %m");
+
+                boundary_lines = table_add_uid_boundaries(table, uid_range);
+                if (boundary_lines < 0)
+                        return boundary_lines;
+
+                uid_map_lines = table_add_uid_map(table, uid_range, add_unavailable_uid);
+                if (uid_map_lines < 0)
+                        return uid_map_lines;
+
+                if (table_get_rows(table) > 1) {
+                        r = table_print_with_pager(table, arg_json_format_flags, arg_pager_flags, arg_legend);
+                        if (r < 0)
+                                return table_log_print_error(r);
+                }
+
+                if (arg_legend) {
+                        size_t k;
+
+                        k = table_get_rows(table) - 1 - boundary_lines - uid_map_lines;
+                        if (k > 0)
+                                printf("\n%zu users listed.\n", k);
+                        else
+                                printf("No users.\n");
+                }
+        }
+
+        return ret;
+}
+
+static int show_group(GroupRecord *gr, Table *table) {
+        int r;
+
+        assert(gr);
+
+        switch (arg_output) {
+
+        case OUTPUT_CLASSIC: {
+                _cleanup_free_ char *m = NULL;
+
+                if (!gid_is_valid(gr->gid))
+                        break;
+
+                m = strv_join(gr->members, ",");
+                if (!m)
+                        return log_oom();
+
+                printf("%s:x:" GID_FMT ":%s\n",
+                       gr->group_name,
+                       gr->gid,
+                       m);
+                break;
+        }
+
+        case OUTPUT_JSON:
+                json_variant_dump(gr->json, arg_json_format_flags, NULL, 0);
+                break;
+
+        case OUTPUT_FRIENDLY:
+                group_record_show(gr, true);
+
+                if (gr->incomplete) {
+                        fflush(stdout);
+                        log_warning("Warning: lacking rights to acquire privileged fields of group record of '%s', output incomplete.", gr->group_name);
+                }
+
+                break;
+
+        case OUTPUT_TABLE: {
+                UserDisposition d;
+
+                assert(table);
+                d = group_record_disposition(gr);
+
+                r = table_add_many(
+                                table,
+                                TABLE_STRING, "",
+                                TABLE_STRING, gr->group_name,
+                                TABLE_SET_COLOR, user_disposition_to_color(d),
+                                TABLE_STRING, user_disposition_to_string(d),
+                                TABLE_GID, gr->gid,
+                                TABLE_STRING, gr->description,
+                                TABLE_INT, 0);
+                if (r < 0)
+                        return table_log_add_error(r);
+
+                break;
+        }
+
+        default:
+                assert_not_reached();
+        }
+
+        return 0;
+}
+
+static int table_add_gid_boundaries(Table *table, const UidRange *p) {
+        int r;
+
+        assert(table);
+
+        for (size_t i = 0; i < ELEMENTSOF(uid_range_table); i++) {
+                _cleanup_free_ char *name = NULL, *comment = NULL;
+
+                if (!uid_range_covers(p, uid_range_table[i].first, uid_range_table[i].last))
+                        continue;
+
+                name = strjoin(special_glyph(SPECIAL_GLYPH_ARROW_DOWN),
+                               " begin ", uid_range_table[i].name, " groups ",
+                               special_glyph(SPECIAL_GLYPH_ARROW_DOWN));
+                if (!name)
+                        return log_oom();
+
+                comment = strjoin("First ", uid_range_table[i].name, " group");
+                if (!comment)
+                        return log_oom();
+
+                r = table_add_many(
+                                table,
+                                TABLE_STRING, special_glyph(SPECIAL_GLYPH_TREE_TOP),
+                                TABLE_STRING, name,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_STRING, user_disposition_to_string(uid_range_table[i].disposition),
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_GID, uid_range_table[i].first,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_STRING, comment,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_INT, -1); /* sort before any other entry with the same GID */
+                if (r < 0)
+                        return table_log_add_error(r);
+
+                free(name);
+                name = strjoin(special_glyph(SPECIAL_GLYPH_ARROW_UP),
+                               " end ", uid_range_table[i].name, " groups ",
+                               special_glyph(SPECIAL_GLYPH_ARROW_UP));
+                if (!name)
+                        return log_oom();
+
+                free(comment);
+                comment = strjoin("Last ", uid_range_table[i].name, " group");
+                if (!comment)
+                        return log_oom();
+
+                r = table_add_many(
+                                table,
+                                TABLE_STRING, special_glyph(SPECIAL_GLYPH_TREE_RIGHT),
+                                TABLE_STRING, name,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_STRING, user_disposition_to_string(uid_range_table[i].disposition),
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_GID, uid_range_table[i].last,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_STRING, comment,
+                                TABLE_SET_COLOR, ansi_grey(),
+                                TABLE_INT, 1); /* sort after any other entry with the same GID */
+                if (r < 0)
+                        return table_log_add_error(r);
+        }
+
+        return ELEMENTSOF(uid_range_table) * 2;
+}
+
+static int add_unavailable_gid(Table *table, uid_t start, uid_t end) {
+        _cleanup_free_ char *name = NULL;
+        int r;
+
+        assert(table);
+        assert(start <= end);
+
+        name = strjoin(special_glyph(SPECIAL_GLYPH_ARROW_DOWN),
+                       " begin unavailable groups ",
+                       special_glyph(SPECIAL_GLYPH_ARROW_DOWN));
+        if (!name)
+                return log_oom();
+
+        r = table_add_many(
+                        table,
+                        TABLE_STRING, special_glyph(SPECIAL_GLYPH_TREE_TOP),
+                        TABLE_STRING, name,
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_EMPTY,
+                        TABLE_GID, start,
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_STRING, "First unavailable group",
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_INT, -1); /* sort before any other entry with the same GID */
+        if (r < 0)
+                return table_log_add_error(r);
+
+        free(name);
+        name = strjoin(special_glyph(SPECIAL_GLYPH_ARROW_UP),
+                       " end unavailable groups ",
+                       special_glyph(SPECIAL_GLYPH_ARROW_UP));
+        if (!name)
+                return log_oom();
+
+        r = table_add_many(
+                        table,
+                        TABLE_STRING, special_glyph(SPECIAL_GLYPH_TREE_RIGHT),
+                        TABLE_STRING, name,
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_EMPTY,
+                        TABLE_GID, end,
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_STRING, "Last unavailable group",
+                        TABLE_SET_COLOR, ansi_grey(),
+                        TABLE_INT, 1); /* sort after any other entry with the same GID */
+        if (r < 0)
+                return table_log_add_error(r);
+
+        return 2;
+}
+
+static int display_group(int argc, char *argv[], void *userdata) {
+        _cleanup_(table_unrefp) Table *table = NULL;
+        bool draw_separator = false;
+        int ret = 0, r;
+
+        if (arg_output < 0)
+                arg_output = argc > 1 ? OUTPUT_FRIENDLY : OUTPUT_TABLE;
+
+        if (arg_output == OUTPUT_TABLE) {
+                table = table_new(" ", "name", "disposition", "gid", "description", "order");
+                if (!table)
+                        return log_oom();
+
+                (void) table_set_align_percent(table, table_get_cell(table, 0, 3), 100);
+                table_set_ersatz_string(table, TABLE_ERSATZ_DASH);
+                (void) table_set_sort(table, (size_t) 3, (size_t) 5);
+                (void) table_set_display(table, (size_t) 0, (size_t) 1, (size_t) 2, (size_t) 3, (size_t) 4);
+        }
+
+        if (argc > 1)
+                STRV_FOREACH(i, argv + 1) {
+                        _cleanup_(group_record_unrefp) GroupRecord *gr = NULL;
+                        gid_t gid;
+
+                        if (parse_gid(*i, &gid) >= 0)
+                                r = groupdb_by_gid(gid, arg_userdb_flags, &gr);
+                        else
+                                r = groupdb_by_name(*i, arg_userdb_flags, &gr);
+                        if (r < 0) {
+                                if (r == -ESRCH)
+                                        log_error_errno(r, "Group %s does not exist.", *i);
+                                else if (r == -EHOSTDOWN)
+                                        log_error_errno(r, "Selected group database service is not available for this request.");
+                                else
+                                        log_error_errno(r, "Failed to find group %s: %m", *i);
+
+                                if (ret >= 0)
+                                        ret = r;
+                        } else {
+                                if (draw_separator && arg_output == OUTPUT_FRIENDLY)
+                                        putchar('\n');
+
+                                r = show_group(gr, table);
+                                if (r < 0)
+                                        return r;
+
+                                draw_separator = true;
+                        }
+                }
+        else {
+                _cleanup_(userdb_iterator_freep) UserDBIterator *iterator = NULL;
+
+                r = groupdb_all(arg_userdb_flags, &iterator);
+                if (r == -ENOLINK)
+                        log_debug_errno(r, "No entries found. (Didn't check via Varlink.)");
+                else if (r == -ESRCH)
+                        log_debug_errno(r, "No entries found.");
+                else if (r < 0)
+                        return log_error_errno(r, "Failed to enumerate groups: %m");
+                else {
+                        for (;;) {
+                                _cleanup_(group_record_unrefp) GroupRecord *gr = NULL;
+
+                                r = groupdb_iterator_get(iterator, &gr);
+                                if (r == -ESRCH)
+                                        break;
+                                if (r == -EHOSTDOWN)
+                                        return log_error_errno(r, "Selected group database service is not available for this request.");
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed acquire next group: %m");
+
+                                if (draw_separator && arg_output == OUTPUT_FRIENDLY)
+                                        putchar('\n');
+
+                                r = show_group(gr, table);
+                                if (r < 0)
+                                        return r;
+
+                                draw_separator = true;
+                        }
+                }
+        }
+
+        if (table) {
+                _cleanup_(uid_range_freep) UidRange *gid_range = NULL;
+                int boundary_lines, gid_map_lines;
+
+                r = uid_range_load_userns(&gid_range, "/proc/self/gid_map");
+                if (r < 0)
+                        log_debug_errno(r, "Failed to load /proc/self/gid_map, ignoring: %m");
+
+                boundary_lines = table_add_gid_boundaries(table, gid_range);
+                if (boundary_lines < 0)
+                        return boundary_lines;
+
+                gid_map_lines = table_add_uid_map(table, gid_range, add_unavailable_gid);
+                if (gid_map_lines < 0)
+                        return gid_map_lines;
+
+                if (table_get_rows(table) > 1) {
+                        r = table_print_with_pager(table, arg_json_format_flags, arg_pager_flags, arg_legend);
+                        if (r < 0)
+                                return table_log_print_error(r);
+                }
+
+                if (arg_legend) {
+                        size_t k;
+
+                        k = table_get_rows(table) - 1 - boundary_lines - gid_map_lines;
+                        if (k > 0)
+                                printf("\n%zu groups listed.\n", k);
+                        else
+                                printf("No groups.\n");
+                }
+        }
+
+        return ret;
+}
+
+static int show_membership(const char *user, const char *group, Table *table) {
+        int r;
+
+        assert(user);
+        assert(group);
+
+        switch (arg_output) {
+
+        case OUTPUT_CLASSIC:
+                /* Strictly speaking there's no 'classic' output for this concept, but let's output it in
+                 * similar style to the classic output for user/group info */
+
+                printf("%s:%s\n", user, group);
+                break;
+
+        case OUTPUT_JSON: {
+                _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+
+                r = json_build(&v, JSON_BUILD_OBJECT(
+                                               JSON_BUILD_PAIR("user", JSON_BUILD_STRING(user)),
+                                               JSON_BUILD_PAIR("group", JSON_BUILD_STRING(group))));
+                if (r < 0)
+                        return log_error_errno(r, "Failed to build JSON object: %m");
+
+                json_variant_dump(v, arg_json_format_flags, NULL, NULL);
+                break;
+        }
+
+        case OUTPUT_FRIENDLY:
+                /* Hmm, this is not particularly friendly, but not sure how we could do this better */
+                printf("%s: %s\n", group, user);
+                break;
+
+        case OUTPUT_TABLE:
+                assert(table);
+
+                r = table_add_many(
+                                table,
+                                TABLE_STRING, user,
+                                TABLE_STRING, group);
+                if (r < 0)
+                        return table_log_add_error(r);
+
+                break;
+
+        default:
+                assert_not_reached();
+        }
+
+        return 0;
+}
+
+static int display_memberships(int argc, char *argv[], void *userdata) {
+        _cleanup_(table_unrefp) Table *table = NULL;
+        int ret = 0, r;
+
+        if (arg_output < 0)
+                arg_output = OUTPUT_TABLE;
+
+        if (arg_output == OUTPUT_TABLE) {
+                table = table_new("user", "group");
+                if (!table)
+                        return log_oom();
+
+                (void) table_set_sort(table, (size_t) 0, (size_t) 1);
+        }
+
+        if (argc > 1)
+                STRV_FOREACH(i, argv + 1) {
+                        _cleanup_(userdb_iterator_freep) UserDBIterator *iterator = NULL;
+
+                        if (streq(argv[0], "users-in-group")) {
+                                r = membershipdb_by_group(*i, arg_userdb_flags, &iterator);
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed to enumerate users in group: %m");
+                        } else if (streq(argv[0], "groups-of-user")) {
+                                r = membershipdb_by_user(*i, arg_userdb_flags, &iterator);
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed to enumerate groups of user: %m");
+                        } else
+                                assert_not_reached();
+
+                        for (;;) {
+                                _cleanup_free_ char *user = NULL, *group = NULL;
+
+                                r = membershipdb_iterator_get(iterator, &user, &group);
+                                if (r == -ESRCH)
+                                        break;
+                                if (r == -EHOSTDOWN)
+                                        return log_error_errno(r, "Selected membership database service is not available for this request.");
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed acquire next membership: %m");
+
+                                r = show_membership(user, group, table);
+                                if (r < 0)
+                                        return r;
+                        }
+                }
+        else {
+                _cleanup_(userdb_iterator_freep) UserDBIterator *iterator = NULL;
+
+                r = membershipdb_all(arg_userdb_flags, &iterator);
+                if (r == -ENOLINK)
+                        log_debug_errno(r, "No entries found. (Didn't check via Varlink.)");
+                else if (r == -ESRCH)
+                        log_debug_errno(r, "No entries found.");
+                else if (r < 0)
+                        return log_error_errno(r, "Failed to enumerate memberships: %m");
+                else {
+                        for (;;) {
+                                _cleanup_free_ char *user = NULL, *group = NULL;
+
+                                r = membershipdb_iterator_get(iterator, &user, &group);
+                                if (r == -ESRCH)
+                                        break;
+                                if (r == -EHOSTDOWN)
+                                        return log_error_errno(r, "Selected membership database service is not available for this request.");
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed acquire next membership: %m");
+
+                                r = show_membership(user, group, table);
+                                if (r < 0)
+                                        return r;
+                        }
+                }
+        }
+
+        if (table) {
+                if (table_get_rows(table) > 1) {
+                        r = table_print_with_pager(table, arg_json_format_flags, arg_pager_flags, arg_legend);
+                        if (r < 0)
+                                return table_log_print_error(r);
+                }
+
+                if (arg_legend) {
+                        if (table_get_rows(table) > 1)
+                                printf("\n%zu memberships listed.\n", table_get_rows(table) - 1);
+                        else
+                                printf("No memberships.\n");
+                }
+        }
+
+        return ret;
+}
+
+static int display_services(int argc, char *argv[], void *userdata) {
+        _cleanup_(table_unrefp) Table *t = NULL;
+        _cleanup_closedir_ DIR *d = NULL;
+        int r;
+
+        d = opendir("/run/systemd/userdb/");
+        if (!d) {
+                if (errno == ENOENT) {
+                        log_info("No services.");
+                        return 0;
+                }
+
+                return log_error_errno(errno, "Failed to open /run/systemd/userdb/: %m");
+        }
+
+        t = table_new("service", "listening");
+        if (!t)
+                return log_oom();
+
+        (void) table_set_sort(t, (size_t) 0);
+
+        FOREACH_DIRENT(de, d, return -errno) {
+                _cleanup_free_ char *j = NULL, *no = NULL;
+                _cleanup_close_ int fd = -EBADF;
+
+                j = path_join("/run/systemd/userdb/", de->d_name);
+                if (!j)
+                        return log_oom();
+
+                fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+                if (fd < 0)
+                        return log_error_errno(errno, "Failed to allocate AF_UNIX/SOCK_STREAM socket: %m");
+
+                r = connect_unix_path(fd, dirfd(d), de->d_name);
+                if (r < 0) {
+                        no = strjoin("No (", errno_to_name(r), ")");
+                        if (!no)
+                                return log_oom();
+                }
+
+                r = table_add_many(t,
+                                   TABLE_STRING, de->d_name,
+                                   TABLE_STRING, no ?: "yes",
+                                   TABLE_SET_COLOR, no ? ansi_highlight_red() : ansi_highlight_green());
+                if (r < 0)
+                        return table_log_add_error(r);
+        }
+
+        if (table_get_rows(t) > 1) {
+                r = table_print_with_pager(t, arg_json_format_flags, arg_pager_flags, arg_legend);
+                if (r < 0)
+                        return table_log_print_error(r);
+        }
+
+        if (arg_legend && arg_output != OUTPUT_JSON) {
+                if (table_get_rows(t) > 1)
+                        printf("\n%zu services listed.\n", table_get_rows(t) - 1);
+                else
+                        printf("No services.\n");
+        }
+
+        return 0;
+}
+
+static int ssh_authorized_keys(int argc, char *argv[], void *userdata) {
+        _cleanup_(user_record_unrefp) UserRecord *ur = NULL;
+        char **chain_invocation;
+        int r;
+
+        assert(argc >= 2);
+
+        if (arg_chain) {
+                /* If --chain is specified, the rest of the command line is the chain command */
+
+                if (argc < 3)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                               "No chain command line specified, refusing.");
+
+                /* Make similar restrictions on the chain command as OpenSSH itself makes on the primary command. */
+                if (!path_is_absolute(argv[2]))
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                               "Chain invocation of ssh-authorized-keys commands requires an absolute binary path argument.");
+
+                if (!path_is_normalized(argv[2]))
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                               "Chain invocation of ssh-authorized-keys commands requires an normalized binary path argument.");
+
+                chain_invocation = argv + 2;
+        } else {
+                /* If --chain is not specified, then refuse any further arguments */
+
+                if (argc > 2)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Too many arguments.");
+
+                chain_invocation = NULL;
+        }
+
+        r = userdb_by_name(argv[1], arg_userdb_flags, &ur);
+        if (r == -ESRCH)
+                log_error_errno(r, "User %s does not exist.", argv[1]);
+        else if (r == -EHOSTDOWN)
+                log_error_errno(r, "Selected user database service is not available for this request.");
+        else if (r == -EINVAL)
+                log_error_errno(r, "Failed to find user %s: %m (Invalid user name?)", argv[1]);
+        else if (r < 0)
+                log_error_errno(r, "Failed to find user %s: %m", argv[1]);
+        else {
+                if (strv_isempty(ur->ssh_authorized_keys))
+                        log_debug("User record for %s has no public SSH keys.", argv[1]);
+                else
+                        STRV_FOREACH(i, ur->ssh_authorized_keys)
+                                printf("%s\n", *i);
+
+                if (ur->incomplete) {
+                        fflush(stdout);
+                        log_warning("Warning: lacking rights to acquire privileged fields of user record of '%s', output incomplete.", ur->user_name);
+                }
+        }
+
+        if (chain_invocation) {
+                if (DEBUG_LOGGING) {
+                        _cleanup_free_ char *s = NULL;
+
+                        s = quote_command_line(chain_invocation, SHELL_ESCAPE_EMPTY);
+                        if (!s)
+                                return log_oom();
+
+                        log_debug("Chain invoking: %s", s);
+                }
+
+                fflush(stdout);
+                execv(chain_invocation[0], chain_invocation);
+                if (errno == ENOENT) /* Let's handle ENOENT gracefully */
+                        log_warning_errno(errno, "Chain executable '%s' does not exist, ignoring chain invocation.", chain_invocation[0]);
+                else {
+                        log_error_errno(errno, "Failed to invoke chain executable '%s': %m", chain_invocation[0]);
+                        if (r >= 0)
+                                r = -errno;
+                }
+        }
+
+        return r;
+}
+
+static int help(int argc, char *argv[], void *userdata) {
+        _cleanup_free_ char *link = NULL;
+        int r;
+
+        pager_open(arg_pager_flags);
+
+        r = terminal_urlify_man("userdbctl", "1", &link);
+        if (r < 0)
+                return log_oom();
+
+        printf("%s [OPTIONS...] COMMAND ...\n\n"
+               "%sShow user and group information.%s\n"
+               "\nCommands:\n"
+               "  user [USER…]               Inspect user\n"
+               "  group [GROUP…]             Inspect group\n"
+               "  users-in-group [GROUP…]    Show users that are members of specified groups\n"
+               "  groups-of-user [USER…]     Show groups the specified users are members of\n"
+               "  services                   Show enabled database services\n"
+               "  ssh-authorized-keys USER   Show SSH authorized keys for user\n"
+               "\nOptions:\n"
+               "  -h --help                  Show this help\n"
+               "     --version               Show package version\n"
+               "     --no-pager              Do not pipe output into a pager\n"
+               "     --no-legend             Do not show the headers and footers\n"
+               "     --output=MODE           Select output mode (classic, friendly, table, json)\n"
+               "  -j                         Equivalent to --output=json\n"
+               "  -s --service=SERVICE[:SERVICE…]\n"
+               "                             Query the specified service\n"
+               "     --with-nss=BOOL         Control whether to include glibc NSS data\n"
+               "  -N                         Do not synthesize or include glibc NSS data\n"
+               "                             (Same as --synthesize=no --with-nss=no)\n"
+               "     --synthesize=BOOL       Synthesize root/nobody user\n"
+               "     --with-dropin=BOOL      Control whether to include drop-in records\n"
+               "     --with-varlink=BOOL     Control whether to talk to services at all\n"
+               "     --multiplexer=BOOL      Control whether to use the multiplexer\n"
+               "     --json=pretty|short     JSON output mode\n"
+               "     --chain                 Chain another command\n"
+               "\nSee the %s for details.\n",
+               program_invocation_short_name,
+               ansi_highlight(),
+               ansi_normal(),
+               link);
+
+        return 0;
+}
+
+static int parse_argv(int argc, char *argv[]) {
+
+        enum {
+                ARG_VERSION = 0x100,
+                ARG_NO_PAGER,
+                ARG_NO_LEGEND,
+                ARG_OUTPUT,
+                ARG_WITH_NSS,
+                ARG_WITH_DROPIN,
+                ARG_WITH_VARLINK,
+                ARG_SYNTHESIZE,
+                ARG_MULTIPLEXER,
+                ARG_JSON,
+                ARG_CHAIN,
+        };
+
+        static const struct option options[] = {
+                { "help",         no_argument,       NULL, 'h'              },
+                { "version",      no_argument,       NULL, ARG_VERSION      },
+                { "no-pager",     no_argument,       NULL, ARG_NO_PAGER     },
+                { "no-legend",    no_argument,       NULL, ARG_NO_LEGEND    },
+                { "output",       required_argument, NULL, ARG_OUTPUT       },
+                { "service",      required_argument, NULL, 's'              },
+                { "with-nss",     required_argument, NULL, ARG_WITH_NSS     },
+                { "with-dropin",  required_argument, NULL, ARG_WITH_DROPIN  },
+                { "with-varlink", required_argument, NULL, ARG_WITH_VARLINK },
+                { "synthesize",   required_argument, NULL, ARG_SYNTHESIZE   },
+                { "multiplexer",  required_argument, NULL, ARG_MULTIPLEXER  },
+                { "json",         required_argument, NULL, ARG_JSON         },
+                { "chain",        no_argument,       NULL, ARG_CHAIN        },
+                {}
+        };
+
+        const char *e;
+        int r;
+
+        assert(argc >= 0);
+        assert(argv);
+
+        /* We are going to update this environment variable with our own, hence let's first read what is already set */
+        e = getenv("SYSTEMD_ONLY_USERDB");
+        if (e) {
+                char **l;
+
+                l = strv_split(e, ":");
+                if (!l)
+                        return log_oom();
+
+                strv_free(arg_services);
+                arg_services = l;
+        }
+
+        /* Resetting to 0 forces the invocation of an internal initialization routine of getopt_long()
+         * that checks for GNU extensions in optstring ('-' or '+' at the beginning). */
+        optind = 0;
+
+        for (;;) {
+                int c;
+
+                c = getopt_long(argc, argv,
+                                arg_chain ? "+hjs:N" : "hjs:N", /* When --chain was used disable parsing of further switches */
+                                options, NULL);
+                if (c < 0)
+                        break;
+
+                switch (c) {
+
+                case 'h':
+                        return help(0, NULL, NULL);
+
+                case ARG_VERSION:
+                        return version();
+
+                case ARG_NO_PAGER:
+                        arg_pager_flags |= PAGER_DISABLE;
+                        break;
+
+                case ARG_NO_LEGEND:
+                        arg_legend = false;
+                        break;
+
+                case ARG_OUTPUT:
+                        if (isempty(optarg))
+                                arg_output = _OUTPUT_INVALID;
+                        else if (streq(optarg, "classic"))
+                                arg_output = OUTPUT_CLASSIC;
+                        else if (streq(optarg, "friendly"))
+                                arg_output = OUTPUT_FRIENDLY;
+                        else if (streq(optarg, "json"))
+                                arg_output = OUTPUT_JSON;
+                        else if (streq(optarg, "table"))
+                                arg_output = OUTPUT_TABLE;
+                        else if (streq(optarg, "help")) {
+                                puts("classic\n"
+                                     "friendly\n"
+                                     "json\n"
+                                     "table");
+                                return 0;
+                        } else
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid --output= mode: %s", optarg);
+
+                        arg_json_format_flags = arg_output == OUTPUT_JSON ? JSON_FORMAT_PRETTY|JSON_FORMAT_COLOR_AUTO : JSON_FORMAT_OFF;
+                        break;
+
+                case ARG_JSON:
+                        r = parse_json_argument(optarg, &arg_json_format_flags);
+                        if (r <= 0)
+                                return r;
+
+                        arg_output = FLAGS_SET(arg_json_format_flags, JSON_FORMAT_OFF) ? _OUTPUT_INVALID : OUTPUT_JSON;
+                        break;
+
+                case 'j':
+                        arg_json_format_flags = JSON_FORMAT_PRETTY|JSON_FORMAT_COLOR_AUTO;
+                        arg_output = OUTPUT_JSON;
+                        break;
+
+                case 's':
+                        if (isempty(optarg))
+                                arg_services = strv_free(arg_services);
+                        else {
+                                _cleanup_strv_free_ char **l = NULL;
+
+                                l = strv_split(optarg, ":");
+                                if (!l)
+                                        return log_oom();
+
+                                r = strv_extend_strv(&arg_services, l, true);
+                                if (r < 0)
+                                        return log_oom();
+                        }
+
+                        break;
+
+                case 'N':
+                        arg_userdb_flags |= USERDB_EXCLUDE_NSS|USERDB_DONT_SYNTHESIZE;
+                        break;
+
+                case ARG_WITH_NSS:
+                        r = parse_boolean_argument("--with-nss=", optarg, NULL);
+                        if (r < 0)
+                                return r;
+
+                        SET_FLAG(arg_userdb_flags, USERDB_EXCLUDE_NSS, !r);
+                        break;
+
+                case ARG_WITH_DROPIN:
+                        r = parse_boolean_argument("--with-dropin=", optarg, NULL);
+                        if (r < 0)
+                                return r;
+
+                        SET_FLAG(arg_userdb_flags, USERDB_EXCLUDE_DROPIN, !r);
+                        break;
+
+                case ARG_WITH_VARLINK:
+                        r = parse_boolean_argument("--with-varlink=", optarg, NULL);
+                        if (r < 0)
+                                return r;
+
+                        SET_FLAG(arg_userdb_flags, USERDB_EXCLUDE_VARLINK, !r);
+                        break;
+
+                case ARG_SYNTHESIZE:
+                        r = parse_boolean_argument("--synthesize=", optarg, NULL);
+                        if (r < 0)
+                                return r;
+
+                        SET_FLAG(arg_userdb_flags, USERDB_DONT_SYNTHESIZE, !r);
+                        break;
+
+                case ARG_MULTIPLEXER:
+                        r = parse_boolean_argument("--multiplexer=", optarg, NULL);
+                        if (r < 0)
+                                return r;
+
+                        SET_FLAG(arg_userdb_flags, USERDB_AVOID_MULTIPLEXER, !r);
+                        break;
+
+                case ARG_CHAIN:
+                        arg_chain = true;
+                        break;
+
+                case '?':
+                        return -EINVAL;
+
+                default:
+                        assert_not_reached();
+                }
+        }
+
+        return 1;
+}
+
+static int run(int argc, char *argv[]) {
+        static const Verb verbs[] = {
+                { "help",                VERB_ANY, VERB_ANY, 0,            help                },
+                { "user",                VERB_ANY, VERB_ANY, VERB_DEFAULT, display_user        },
+                { "group",               VERB_ANY, VERB_ANY, 0,            display_group       },
+                { "users-in-group",      VERB_ANY, VERB_ANY, 0,            display_memberships },
+                { "groups-of-user",      VERB_ANY, VERB_ANY, 0,            display_memberships },
+                { "services",            VERB_ANY, 1,        0,            display_services    },
+
+                /* This one is a helper for sshd_config's AuthorizedKeysCommand= setting, it's not a
+                 * user-facing verb and thus should not appear in man pages or --help texts. */
+                { "ssh-authorized-keys", 2,        VERB_ANY, 0,            ssh_authorized_keys },
+                {}
+        };
+
+        int r;
+
+        log_setup();
+
+        r = parse_argv(argc, argv);
+        if (r <= 0)
+                return r;
+
+        if (arg_services) {
+                _cleanup_free_ char *e = NULL;
+
+                e = strv_join(arg_services, ":");
+                if (!e)
+                        return log_oom();
+
+                if (setenv("SYSTEMD_ONLY_USERDB", e, true) < 0)
+                        return log_error_errno(r, "Failed to set $SYSTEMD_ONLY_USERDB: %m");
+
+                log_info("Enabled services: %s", e);
+        } else
+                assert_se(unsetenv("SYSTEMD_ONLY_USERDB") == 0);
+
+        return dispatch_verb(argc, argv, verbs, NULL);
+}
+
+DEFINE_MAIN_FUNCTION(run);
diff --git a/src/userdb/userdbd-manager.c b/src/userdb/userdbd-manager.c
new file mode 100644
index 0000000..c1dfe47
--- /dev/null
+++ b/src/userdb/userdbd-manager.c
@@ -0,0 +1,321 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/wait.h>
+
+#include "sd-daemon.h"
+
+#include "common-signal.h"
+#include "fd-util.h"
+#include "fs-util.h"
+#include "mkdir.h"
+#include "process-util.h"
+#include "set.h"
+#include "signal-util.h"
+#include "socket-util.h"
+#include "stdio-util.h"
+#include "umask-util.h"
+#include "userdbd-manager.h"
+
+#define LISTEN_TIMEOUT_USEC (25 * USEC_PER_SEC)
+
+static int start_workers(Manager *m, bool explicit_request);
+
+static int on_worker_exit(sd_event_source *s, const siginfo_t *si, void *userdata) {
+        Manager *m = ASSERT_PTR(userdata);
+
+        assert(s);
+
+        assert_se(!set_remove(m->workers_dynamic, s) != !set_remove(m->workers_fixed, s));
+        sd_event_source_disable_unref(s);
+
+        if (si->si_code == CLD_EXITED) {
+                if (si->si_status == EXIT_SUCCESS)
+                        log_debug("Worker " PID_FMT " exited successfully.", si->si_pid);
+                else
+                        log_warning("Worker " PID_FMT " died with a failure exit status %i, ignoring.", si->si_pid, si->si_status);
+        } else if (si->si_code == CLD_KILLED)
+                log_warning("Worker " PID_FMT " was killed by signal %s, ignoring.", si->si_pid, signal_to_string(si->si_status));
+        else if (si->si_code == CLD_DUMPED)
+                log_warning("Worker " PID_FMT " dumped core by signal %s, ignoring.", si->si_pid, signal_to_string(si->si_status));
+        else
+                log_warning("Can't handle SIGCHLD of this type");
+
+        (void) start_workers(m, /* explicit_request= */ false); /* Fill up workers again if we fell below the low watermark */
+        return 0;
+}
+
+static int on_sigusr2(sd_event_source *s, const struct signalfd_siginfo *si, void *userdata) {
+        Manager *m = ASSERT_PTR(userdata);
+
+        assert(s);
+
+        (void) start_workers(m, /* explicit_request=*/ true); /* Workers told us there's more work, let's add one more worker as long as we are below the high watermark */
+        return 0;
+}
+
+static int on_deferred_start_worker(sd_event_source *s, uint64_t usec, void *userdata) {
+        Manager *m = ASSERT_PTR(userdata);
+
+        assert(s);
+
+        m->deferred_start_worker_event_source = sd_event_source_unref(m->deferred_start_worker_event_source);
+
+        (void) start_workers(m, /* explicit_request=*/ false);
+        return 0;
+}
+
+DEFINE_HASH_OPS_WITH_KEY_DESTRUCTOR(
+                event_source_hash_ops,
+                sd_event_source,
+                (void (*)(const sd_event_source*, struct siphash*)) trivial_hash_func,
+                (int (*)(const sd_event_source*, const sd_event_source*)) trivial_compare_func,
+                sd_event_source_disable_unref);
+
+int manager_new(Manager **ret) {
+        _cleanup_(manager_freep) Manager *m = NULL;
+        int r;
+
+        m = new(Manager, 1);
+        if (!m)
+                return -ENOMEM;
+
+        *m = (Manager) {
+                .listen_fd = -EBADF,
+                .worker_ratelimit = {
+                        .interval = 2 * USEC_PER_SEC,
+                        .burst = 2500,
+                },
+        };
+
+        r = sd_event_new(&m->event);
+        if (r < 0)
+                return r;
+
+        r = sd_event_set_signal_exit(m->event, true);
+        if (r < 0)
+                return r;
+
+        r = sd_event_add_signal(m->event, NULL, (SIGRTMIN+18)|SD_EVENT_SIGNAL_PROCMASK, sigrtmin18_handler, NULL);
+        if (r < 0)
+                return r;
+
+        r = sd_event_add_memory_pressure(m->event, NULL, NULL, NULL);
+        if (r < 0)
+                log_debug_errno(r, "Failed allocate memory pressure event source, ignoring: %m");
+
+        r = sd_event_set_watchdog(m->event, true);
+        if (r < 0)
+                log_debug_errno(r, "Failed to enable watchdog handling, ignoring: %m");
+
+        r = sd_event_add_signal(m->event, NULL, SIGUSR2|SD_EVENT_SIGNAL_PROCMASK, on_sigusr2, m);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(m);
+        return 0;
+}
+
+Manager* manager_free(Manager *m) {
+        if (!m)
+                return NULL;
+
+        set_free(m->workers_fixed);
+        set_free(m->workers_dynamic);
+
+        m->deferred_start_worker_event_source = sd_event_source_unref(m->deferred_start_worker_event_source);
+
+        safe_close(m->listen_fd);
+
+        sd_event_unref(m->event);
+
+        return mfree(m);
+}
+
+static size_t manager_current_workers(Manager *m) {
+        assert(m);
+
+        return set_size(m->workers_fixed) + set_size(m->workers_dynamic);
+}
+
+static int start_one_worker(Manager *m) {
+        _cleanup_(sd_event_source_disable_unrefp) sd_event_source *source = NULL;
+        bool fixed;
+        pid_t pid;
+        int r;
+
+        assert(m);
+
+        fixed = set_size(m->workers_fixed) < USERDB_WORKERS_MIN;
+
+        r = safe_fork_full(
+                        "(sd-worker)",
+                        /* stdio_fds= */ NULL,
+                        &m->listen_fd, 1,
+                        FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGTERM|FORK_REOPEN_LOG|FORK_LOG|FORK_CLOSE_ALL_FDS,
+                        &pid);
+        if (r < 0)
+                return log_error_errno(r, "Failed to fork new worker child: %m");
+        if (r == 0) {
+                char pids[DECIMAL_STR_MAX(pid_t)];
+                /* Child */
+
+                if (m->listen_fd == 3) {
+                        r = fd_cloexec(3, false);
+                        if (r < 0) {
+                                log_error_errno(r, "Failed to turn off O_CLOEXEC for fd 3: %m");
+                                _exit(EXIT_FAILURE);
+                        }
+                } else {
+                        if (dup2(m->listen_fd, 3) < 0) { /* dup2() creates with O_CLOEXEC off */
+                                log_error_errno(errno, "Failed to move listen fd to 3: %m");
+                                _exit(EXIT_FAILURE);
+                        }
+
+                        safe_close(m->listen_fd);
+                }
+
+                xsprintf(pids, PID_FMT, pid);
+                if (setenv("LISTEN_PID", pids, 1) < 0) {
+                        log_error_errno(errno, "Failed to set $LISTEN_PID: %m");
+                        _exit(EXIT_FAILURE);
+                }
+
+                if (setenv("LISTEN_FDS", "1", 1) < 0) {
+                        log_error_errno(errno, "Failed to set $LISTEN_FDS: %m");
+                        _exit(EXIT_FAILURE);
+                }
+
+
+                if (setenv("USERDB_FIXED_WORKER", one_zero(fixed), 1) < 0) {
+                        log_error_errno(errno, "Failed to set $USERDB_FIXED_WORKER: %m");
+                        _exit(EXIT_FAILURE);
+                }
+
+                /* execl("/home/lennart/projects/systemd/build/systemd-userwork", "systemd-userwork", "xxxxxxxxxxxxxxxx", NULL); /\* With some extra space rename_process() can make use of *\/ */
+                /* execl("/usr/bin/valgrind", "valgrind", "/home/lennart/projects/systemd/build/systemd-userwork", "systemd-userwork", "xxxxxxxxxxxxxxxx", NULL); /\* With some extra space rename_process() can make use of *\/ */
+
+                execl(SYSTEMD_USERWORK_PATH, "systemd-userwork", "xxxxxxxxxxxxxxxx", NULL); /* With some extra space rename_process() can make use of */
+                log_error_errno(errno, "Failed start worker process: %m");
+                _exit(EXIT_FAILURE);
+        }
+
+        r = sd_event_add_child(m->event, &source, pid, WEXITED, on_worker_exit, m);
+        if (r < 0)
+                return log_error_errno(r, "Failed to watch child " PID_FMT ": %m", pid);
+
+        r = set_ensure_put(
+                        fixed ? &m->workers_fixed : &m->workers_dynamic,
+                        &event_source_hash_ops,
+                        source);
+        if (r < 0)
+                return log_error_errno(r, "Failed to add child process to set: %m");
+
+        TAKE_PTR(source);
+
+        return 0;
+}
+
+static int start_workers(Manager *m, bool explicit_request) {
+        int r;
+
+        assert(m);
+
+        for (;;)  {
+                size_t n;
+
+                n = manager_current_workers(m);
+                if (n >= USERDB_WORKERS_MIN && (!explicit_request || n >= USERDB_WORKERS_MAX))
+                        break;
+
+                if (!ratelimit_below(&m->worker_ratelimit)) {
+
+                        /* If we keep starting workers too often but none sticks, let's fail the whole
+                         * daemon, something is wrong */
+                        if (n == 0) {
+                                sd_event_exit(m->event, EXIT_FAILURE);
+                                return log_error_errno(SYNTHETIC_ERRNO(EUCLEAN), "Worker threads requested too frequently, but worker count is zero, something is wrong.");
+                        }
+
+                        /* Otherwise, let's stop spawning more for a while. */
+                        log_warning("Worker threads requested too frequently, not starting new ones for a while.");
+
+                        if (!m->deferred_start_worker_event_source) {
+                                r = sd_event_add_time(
+                                                m->event,
+                                                &m->deferred_start_worker_event_source,
+                                                CLOCK_MONOTONIC,
+                                                ratelimit_end(&m->worker_ratelimit),
+                                                /* accuracy_usec= */ 0,
+                                                on_deferred_start_worker,
+                                                m);
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed to allocate deferred start worker event source: %m");
+                        }
+
+                        break;
+                }
+
+                r = start_one_worker(m);
+                if (r < 0)
+                        return r;
+
+                explicit_request = false;
+        }
+
+        return 0;
+}
+
+int manager_startup(Manager *m) {
+        int n, r;
+
+        assert(m);
+        assert(m->listen_fd < 0);
+
+        n = sd_listen_fds(false);
+        if (n < 0)
+                return log_error_errno(n, "Failed to determine number of passed file descriptors: %m");
+        if (n > 1)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Expected one listening fd, got %i.", n);
+        if (n == 1)
+                m->listen_fd = SD_LISTEN_FDS_START;
+        else {
+                static const union sockaddr_union sockaddr = {
+                        .un.sun_family = AF_UNIX,
+                        .un.sun_path = "/run/systemd/userdb/io.systemd.Multiplexer",
+                };
+
+                r = mkdir_p("/run/systemd/userdb", 0755);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to create /run/systemd/userdb: %m");
+
+                m->listen_fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
+                if (m->listen_fd < 0)
+                        return log_error_errno(errno, "Failed to bind on socket: %m");
+
+                (void) sockaddr_un_unlink(&sockaddr.un);
+
+                WITH_UMASK(0000)
+                        if (bind(m->listen_fd, &sockaddr.sa, SOCKADDR_UN_LEN(sockaddr.un)) < 0)
+                                return log_error_errno(errno, "Failed to bind socket: %m");
+
+                r = symlink_idempotent("io.systemd.Multiplexer",
+                                       "/run/systemd/userdb/io.systemd.NameServiceSwitch", false);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to bind io.systemd.Multiplexer: %m");
+
+                r = symlink_idempotent("io.systemd.Multiplexer",
+                                       "/run/systemd/userdb/io.systemd.DropIn", false);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to bind io.systemd.Multiplexer: %m");
+
+                if (listen(m->listen_fd, SOMAXCONN_DELUXE) < 0)
+                        return log_error_errno(errno, "Failed to listen on socket: %m");
+        }
+
+        /* Let's make sure every accept() call on this socket times out after 25s. This allows workers to be
+         * GC'ed on idle */
+        if (setsockopt(m->listen_fd, SOL_SOCKET, SO_RCVTIMEO, TIMEVAL_STORE(LISTEN_TIMEOUT_USEC), sizeof(struct timeval)) < 0)
+                return log_error_errno(errno, "Failed to se SO_RCVTIMEO: %m");
+
+        return start_workers(m, /* explicit_request= */ false);
+}
diff --git a/src/userdb/userdbd-manager.h b/src/userdb/userdbd-manager.h
new file mode 100644
index 0000000..c39f79d
--- /dev/null
+++ b/src/userdb/userdbd-manager.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sd-bus.h"
+#include "sd-event.h"
+
+typedef struct Manager Manager;
+
+#include "hashmap.h"
+#include "ratelimit.h"
+
+#define USERDB_WORKERS_MIN 3
+#define USERDB_WORKERS_MAX 4096
+
+struct Manager {
+        sd_event *event;
+
+        Set *workers_fixed;    /* Workers 0…USERDB_WORKERS_MIN */
+        Set *workers_dynamic;  /* Workers USERD_WORKERS_MIN+1…USERDB_WORKERS_MAX */
+
+        int listen_fd;
+
+        RateLimit worker_ratelimit;
+
+        sd_event_source *deferred_start_worker_event_source;
+};
+
+int manager_new(Manager **ret);
+Manager* manager_free(Manager *m);
+DEFINE_TRIVIAL_CLEANUP_FUNC(Manager*, manager_free);
+
+int manager_startup(Manager *m);
diff --git a/src/userdb/userdbd.c b/src/userdb/userdbd.c
new file mode 100644
index 0000000..89ac9c7
--- /dev/null
+++ b/src/userdb/userdbd.c
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "daemon-util.h"
+#include "userdbd-manager.h"
+#include "log.h"
+#include "main-func.h"
+#include "signal-util.h"
+
+/* This service offers two Varlink services, both implementing io.systemd.UserDatabase:
+ *
+ *         → io.systemd.NameServiceSwitch: this is a compatibility interface for glibc NSS: it responds to
+ *           name lookups by checking the classic NSS interfaces and responding that.
+ *
+ *         → io.systemd.Multiplexer: this multiplexes lookup requests to all Varlink services that have a
+ *           socket in /run/systemd/userdb/. It's supposed to simplify clients that don't want to implement
+ *           the full iterative logic on their own.
+ *
+ *         → io.systemd.DropIn: this makes JSON user/group records dropped into /run/userdb/ available as
+ *           regular users.
+ */
+
+static int run(int argc, char *argv[]) {
+        _cleanup_(manager_freep) Manager *m = NULL;
+        _unused_ _cleanup_(notify_on_cleanup) const char *notify_stop = NULL;
+        int r;
+
+        log_setup();
+
+        umask(0022);
+
+        if (argc != 1)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "This program takes no arguments.");
+
+        if (setenv("SYSTEMD_BYPASS_USERDB", "io.systemd.NameServiceSwitch:io.systemd.Multiplexer:io.systemd.DropIn", 1) < 0)
+                return log_error_errno(errno, "Failed to set $SYSTEMD_BYPASS_USERDB: %m");
+
+        assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGCHLD, -1) >= 0);
+
+        r = manager_new(&m);
+        if (r < 0)
+                return log_error_errno(r, "Could not create manager: %m");
+
+        r = manager_startup(m);
+        if (r < 0)
+                return log_error_errno(r, "Failed to start up daemon: %m");
+
+        notify_stop = notify_start(NOTIFY_READY, NOTIFY_STOPPING);
+
+        r = sd_event_loop(m->event);
+        if (r < 0)
+                return log_error_errno(r, "Event loop failed: %m");
+
+        return 0;
+}
+
+DEFINE_MAIN_FUNCTION(run);
diff --git a/src/userdb/userwork.c b/src/userdb/userwork.c
new file mode 100644
index 0000000..b49dbbd
--- /dev/null
+++ b/src/userdb/userwork.c
@@ -0,0 +1,575 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <poll.h>
+#include <sys/wait.h>
+
+#include "sd-daemon.h"
+
+#include "env-util.h"
+#include "fd-util.h"
+#include "group-record.h"
+#include "io-util.h"
+#include "main-func.h"
+#include "process-util.h"
+#include "strv.h"
+#include "time-util.h"
+#include "user-record-nss.h"
+#include "user-record.h"
+#include "user-util.h"
+#include "userdb.h"
+#include "varlink.h"
+#include "varlink-io.systemd.UserDatabase.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 *user_name;
+        const char *group_name;
+        union {
+                uid_t uid;
+                gid_t gid;
+        };
+        const char *service;
+} LookupParameters;
+
+static int add_nss_service(JsonVariant **v) {
+        _cleanup_(json_variant_unrefp) JsonVariant *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 (json_variant_by_key(*v, "service"))
+                return 0;
+
+        r = sd_id128_get_machine(&mid);
+        if (r < 0)
+                return r;
+
+        status = json_variant_ref(json_variant_by_key(*v, "status"));
+        z = json_variant_ref(json_variant_by_key(status, SD_ID128_TO_STRING(mid)));
+
+        if (json_variant_by_key(z, "service"))
+                return 0;
+
+        r = json_variant_set_field_string(&z, "service", "io.systemd.NameServiceSwitch");
+        if (r < 0)
+                return r;
+
+        r = json_variant_set_field(&status, SD_ID128_TO_STRING(mid), z);
+        if (r < 0)
+                return r;
+
+        return json_variant_set_field(v, "status", status);
+}
+
+static int build_user_json(Varlink *link, UserRecord *ur, JsonVariant **ret) {
+        _cleanup_(user_record_unrefp) UserRecord *stripped = NULL;
+        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+        UserRecordLoadFlags flags;
+        uid_t peer_uid;
+        bool trusted;
+        int r;
+
+        assert(ur);
+        assert(ret);
+
+        r = 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 = json_variant_ref(stripped->json);
+        r = add_nss_service(&v);
+        if (r < 0)
+                return r;
+
+        return json_build(ret, JSON_BUILD_OBJECT(
+                                          JSON_BUILD_PAIR("record", JSON_BUILD_VARIANT(v)),
+                                          JSON_BUILD_PAIR("incomplete", JSON_BUILD_BOOLEAN(stripped->incomplete))));
+}
+
+static int userdb_flags_from_service(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 varlink_error(link, "io.systemd.UserDatabase.BadService", NULL);
+
+        return 0;
+}
+
+static int vl_method_get_user_record(Varlink *link, JsonVariant *parameters, VarlinkMethodFlags flags, void *userdata) {
+
+        static const JsonDispatch dispatch_table[] = {
+                { "uid",      JSON_VARIANT_UNSIGNED, json_dispatch_uid_gid,      offsetof(LookupParameters, uid),       0 },
+                { "userName", JSON_VARIANT_STRING,   json_dispatch_const_string, offsetof(LookupParameters, user_name), 0 },
+                { "service",  JSON_VARIANT_STRING,   json_dispatch_const_string, offsetof(LookupParameters, service),   0 },
+                {}
+        };
+
+        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+        _cleanup_(user_record_unrefp) UserRecord *hr = NULL;
+        LookupParameters p = {
+                .uid = UID_INVALID,
+        };
+        UserDBFlags userdb_flags;
+        int r;
+
+        assert(parameters);
+
+        r = 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;
+
+        if (uid_is_valid(p.uid))
+                r = userdb_by_uid(p.uid, userdb_flags, &hr);
+        else if (p.user_name)
+                r = userdb_by_name(p.user_name, userdb_flags, &hr);
+        else {
+                _cleanup_(userdb_iterator_freep) UserDBIterator *iterator = NULL;
+                _cleanup_(json_variant_unrefp) JsonVariant *last = NULL;
+
+                r = userdb_all(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 varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+                if (r < 0)
+                        return r;
+
+                for (;;) {
+                        _cleanup_(user_record_unrefp) UserRecord *z = NULL;
+
+                        r = userdb_iterator_get(iterator, &z);
+                        if (r == -ESRCH)
+                                break;
+                        if (r < 0)
+                                return r;
+
+                        if (last) {
+                                r = varlink_notify(link, last);
+                                if (r < 0)
+                                        return r;
+
+                                last = json_variant_unref(last);
+                        }
+
+                        r = build_user_json(link, z, &last);
+                        if (r < 0)
+                                return r;
+                }
+
+                if (!last)
+                        return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+
+                return varlink_reply(link, last);
+        }
+        if (r == -ESRCH)
+                return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+        if (r < 0) {
+                log_debug_errno(r, "User lookup failed abnormally: %m");
+                return varlink_error(link, "io.systemd.UserDatabase.ServiceNotAvailable", NULL);
+        }
+
+        if ((uid_is_valid(p.uid) && hr->uid != p.uid) ||
+            (p.user_name && !streq(hr->user_name, p.user_name)))
+                return varlink_error(link, "io.systemd.UserDatabase.ConflictingRecordFound", NULL);
+
+        r = build_user_json(link, hr, &v);
+        if (r < 0)
+                return r;
+
+        return varlink_reply(link, v);
+}
+
+static int build_group_json(Varlink *link, GroupRecord *gr, JsonVariant **ret) {
+        _cleanup_(group_record_unrefp) GroupRecord *stripped = NULL;
+        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+        UserRecordLoadFlags flags;
+        uid_t peer_uid;
+        bool trusted;
+        int r;
+
+        assert(gr);
+        assert(ret);
+
+        r = 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 = json_variant_ref(gr->json);
+        r = add_nss_service(&v);
+        if (r < 0)
+                return r;
+
+        return json_build(ret, JSON_BUILD_OBJECT(
+                                          JSON_BUILD_PAIR("record", JSON_BUILD_VARIANT(v)),
+                                          JSON_BUILD_PAIR("incomplete", JSON_BUILD_BOOLEAN(stripped->incomplete))));
+}
+
+static int vl_method_get_group_record(Varlink *link, JsonVariant *parameters, VarlinkMethodFlags flags, void *userdata) {
+
+        static const JsonDispatch dispatch_table[] = {
+                { "gid",       JSON_VARIANT_UNSIGNED, json_dispatch_uid_gid,      offsetof(LookupParameters, gid),        0 },
+                { "groupName", JSON_VARIANT_STRING,   json_dispatch_const_string, offsetof(LookupParameters, group_name), 0 },
+                { "service",   JSON_VARIANT_STRING,   json_dispatch_const_string, offsetof(LookupParameters, service),    0 },
+                {}
+        };
+
+        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+        _cleanup_(group_record_unrefp) GroupRecord *g = NULL;
+        LookupParameters p = {
+                .gid = GID_INVALID,
+        };
+        UserDBFlags userdb_flags;
+        int r;
+
+        assert(parameters);
+
+        r = 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;
+
+        if (gid_is_valid(p.gid))
+                r = groupdb_by_gid(p.gid, userdb_flags, &g);
+        else if (p.group_name)
+                r = groupdb_by_name(p.group_name, userdb_flags, &g);
+        else {
+                _cleanup_(userdb_iterator_freep) UserDBIterator *iterator = NULL;
+                _cleanup_(json_variant_unrefp) JsonVariant *last = NULL;
+
+                r = groupdb_all(userdb_flags, &iterator);
+                if (IN_SET(r, -ESRCH, -ENOLINK))
+                        return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+                if (r < 0)
+                        return r;
+
+                for (;;) {
+                        _cleanup_(group_record_unrefp) GroupRecord *z = NULL;
+
+                        r = groupdb_iterator_get(iterator, &z);
+                        if (r == -ESRCH)
+                                break;
+                        if (r < 0)
+                                return r;
+
+                        if (last) {
+                                r = varlink_notify(link, last);
+                                if (r < 0)
+                                        return r;
+
+                                last = json_variant_unref(last);
+                        }
+
+                        r = build_group_json(link, z, &last);
+                        if (r < 0)
+                                return r;
+                }
+
+                if (!last)
+                        return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+
+                return varlink_reply(link, last);
+        }
+        if (r == -ESRCH)
+                return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+        if (r < 0) {
+                log_debug_errno(r, "Group lookup failed abnormally: %m");
+                return varlink_error(link, "io.systemd.UserDatabase.ServiceNotAvailable", NULL);
+        }
+
+        if ((uid_is_valid(p.gid) && g->gid != p.gid) ||
+            (p.group_name && !streq(g->group_name, p.group_name)))
+                return varlink_error(link, "io.systemd.UserDatabase.ConflictingRecordFound", NULL);
+
+        r = build_group_json(link, g, &v);
+        if (r < 0)
+                return r;
+
+        return varlink_reply(link, v);
+}
+
+static int vl_method_get_memberships(Varlink *link, JsonVariant *parameters, VarlinkMethodFlags flags, void *userdata) {
+        static const JsonDispatch dispatch_table[] = {
+                { "userName",  JSON_VARIANT_STRING, json_dispatch_const_string, offsetof(LookupParameters, user_name), 0 },
+                { "groupName", JSON_VARIANT_STRING, json_dispatch_const_string, offsetof(LookupParameters, group_name), 0 },
+                { "service",   JSON_VARIANT_STRING, json_dispatch_const_string, offsetof(LookupParameters, service),   0 },
+                {}
+        };
+
+        _cleanup_free_ char *last_user_name = NULL, *last_group_name = NULL;
+        _cleanup_(userdb_iterator_freep) UserDBIterator *iterator = NULL;
+        LookupParameters p = {};
+        UserDBFlags userdb_flags;
+        int r;
+
+        assert(parameters);
+
+        r = 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;
+
+        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 varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+        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;
+
+                if (last_user_name) {
+                        assert(last_group_name);
+
+                        r = varlink_notifyb(link, JSON_BUILD_OBJECT(
+                                                            JSON_BUILD_PAIR("userName", JSON_BUILD_STRING(last_user_name)),
+                                                            JSON_BUILD_PAIR("groupName", JSON_BUILD_STRING(last_group_name))));
+                        if (r < 0)
+                                return r;
+                }
+
+                free_and_replace(last_user_name, user_name);
+                free_and_replace(last_group_name, group_name);
+        }
+
+        if (!last_user_name) {
+                assert(!last_group_name);
+                return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+        }
+
+        assert(last_group_name);
+
+        return varlink_replyb(link, JSON_BUILD_OBJECT(
+                                              JSON_BUILD_PAIR("userName", JSON_BUILD_STRING(last_user_name)),
+                                              JSON_BUILD_PAIR("groupName", JSON_BUILD_STRING(last_group_name))));
+}
+
+static int process_connection(VarlinkServer *server, int fd) {
+        _cleanup_(varlink_close_unrefp) Varlink *vl = NULL;
+        int r;
+
+        r = varlink_server_add_connection(server, fd, &vl);
+        if (r < 0) {
+                fd = safe_close(fd);
+                return log_error_errno(r, "Failed to add connection: %m");
+        }
+
+        vl = varlink_ref(vl);
+
+        for (;;) {
+                r = 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 = 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_(varlink_server_unrefp) VarlinkServer *server = 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);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate server: %m");
+
+        r = 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 = 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");
+
+        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)) {
+                                pid_t parent;
+
+                                parent = getppid();
+                                if (parent <= 1)
+                                        return log_error_errno(SYNTHETIC_ERRNO(ESRCH), "Parent already died?");
+
+                                if (kill(parent, SIGUSR2) < 0)
+                                        return log_error_errno(errno, "Failed to kill our own parent: %m");
+                        }
+                }
+
+                (void) process_connection(server, TAKE_FD(fd));
+                last_busy_usec = USEC_INFINITY;
+        }
+
+        return 0;
+}
+
+DEFINE_MAIN_FUNCTION(run);