core: add user/group resolution varlink interface to PID 1

5 files changed, 329 insertions, 1 deletions

diff --git a/src/core/core-varlink.c b/src/core/core-varlink.c
new file mode 100644
index 0000000000..628b9ccaaa
--- /dev/null
+++ b/src/core/core-varlink.c
@@ -0,0 +1,310 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include "core-varlink.h"
+#include "mkdir.h"
+#include "user-util.h"
+#include "varlink.h"
+
+typedef struct LookupParameters {
+        const char *user_name;
+        const char *group_name;
+        union {
+                uid_t uid;
+                gid_t gid;
+        };
+        const char *service;
+} LookupParameters;
+
+static int build_user_json(const char *user_name, uid_t uid, JsonVariant **ret) {
+        assert(user_name);
+        assert(uid_is_valid(uid));
+        assert(ret);
+
+        return json_build(ret, JSON_BUILD_OBJECT(
+                                          JSON_BUILD_PAIR("record", JSON_BUILD_OBJECT(
+                                                                          JSON_BUILD_PAIR("userName", JSON_BUILD_STRING(user_name)),
+                                                                          JSON_BUILD_PAIR("uid", JSON_BUILD_UNSIGNED(uid)),
+                                                                          JSON_BUILD_PAIR("gid", JSON_BUILD_UNSIGNED(uid)),
+                                                                          JSON_BUILD_PAIR("realName", JSON_BUILD_STRING("Dynamic User")),
+                                                                          JSON_BUILD_PAIR("homeDirectory", JSON_BUILD_STRING("/")),
+                                                                          JSON_BUILD_PAIR("shell", JSON_BUILD_STRING(NOLOGIN)),
+                                                                          JSON_BUILD_PAIR("locked", JSON_BUILD_BOOLEAN(true)),
+                                                                          JSON_BUILD_PAIR("service", JSON_BUILD_STRING("io.systemd.DynamicUser")),
+                                                                          JSON_BUILD_PAIR("disposition", JSON_BUILD_STRING("dynamic"))))));
+}
+
+static bool user_match_lookup_parameters(LookupParameters *p, const char *name, uid_t uid) {
+        assert(p);
+
+        if (p->user_name && !streq(name, p->user_name))
+                return false;
+
+        if (uid_is_valid(p->uid) && uid != p->uid)
+                return false;
+
+        return true;
+}
+
+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), JSON_SAFE },
+                { "service",  JSON_VARIANT_STRING,   json_dispatch_const_string, offsetof(LookupParameters, service),   0         },
+                {}
+        };
+
+        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+        LookupParameters p = {
+                .uid = UID_INVALID,
+        };
+        _cleanup_free_ char *found_name = NULL;
+        uid_t found_uid = UID_INVALID, uid;
+        Manager *m = userdata;
+        const char *un;
+        int r;
+
+        assert(parameters);
+        assert(m);
+
+        r = json_dispatch(parameters, dispatch_table, NULL, 0, &p);
+        if (r < 0)
+                return r;
+
+        if (!streq_ptr(p.service, "io.systemd.DynamicUser"))
+                return varlink_error(link, "io.systemd.UserDatabase.BadService", NULL);
+
+        if (uid_is_valid(p.uid))
+                r = dynamic_user_lookup_uid(m, p.uid, &found_name);
+        else if (p.user_name)
+                r = dynamic_user_lookup_name(m, p.user_name, &found_uid);
+        else {
+                Iterator i;
+                DynamicUser *d;
+
+                HASHMAP_FOREACH(d, m->dynamic_users, i) {
+                        r = dynamic_user_current(d, &uid);
+                        if (r == -EAGAIN) /* not realized yet? */
+                                continue;
+                        if (r < 0)
+                                return r;
+
+                        if (!user_match_lookup_parameters(&p, d->name, uid))
+                                continue;
+
+                        if (v) {
+                                r = varlink_notify(link, v);
+                                if (r < 0)
+                                        return r;
+
+                                v = json_variant_unref(v);
+                        }
+
+                        r = build_user_json(d->name, uid, &v);
+                        if (r < 0)
+                                return r;
+                }
+
+                if (!v)
+                        return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+
+                return varlink_reply(link, v);
+        }
+        if (r == -ESRCH)
+                return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+        if (r < 0)
+                return r;
+
+        uid = uid_is_valid(found_uid) ? found_uid : p.uid;
+        un = found_name ?: p.user_name;
+
+        if (!user_match_lookup_parameters(&p, un, uid))
+                return varlink_error(link, "io.systemd.UserDatabase.ConflictingRecordFound", NULL);
+
+        r = build_user_json(un, uid, &v);
+        if (r < 0)
+                return r;
+
+        return varlink_reply(link, v);
+}
+
+static int build_group_json(const char *group_name, gid_t gid, JsonVariant **ret) {
+        assert(group_name);
+        assert(gid_is_valid(gid));
+        assert(ret);
+
+        return json_build(ret, JSON_BUILD_OBJECT(
+                                          JSON_BUILD_PAIR("record", JSON_BUILD_OBJECT(
+                                                                          JSON_BUILD_PAIR("groupName", JSON_BUILD_STRING(group_name)),
+                                                                          JSON_BUILD_PAIR("gid", JSON_BUILD_UNSIGNED(gid)),
+                                                                          JSON_BUILD_PAIR("service", JSON_BUILD_STRING("io.systemd.DynamicUser")),
+                                                                          JSON_BUILD_PAIR("disposition", JSON_BUILD_STRING("dynamic"))))));
+}
+
+static bool group_match_lookup_parameters(LookupParameters *p, const char *name, gid_t gid) {
+        assert(p);
+
+        if (p->group_name && !streq(name, p->group_name))
+                return false;
+
+        if (gid_is_valid(p->gid) && gid != p->gid)
+                return false;
+
+        return true;
+}
+
+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), JSON_SAFE },
+                { "service",   JSON_VARIANT_STRING,   json_dispatch_const_string, offsetof(LookupParameters, service),    0         },
+                {}
+        };
+
+        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+        LookupParameters p = {
+                .gid = GID_INVALID,
+        };
+        _cleanup_free_ char *found_name = NULL;
+        uid_t found_gid = GID_INVALID, gid;
+        Manager *m = userdata;
+        const char *gn;
+        int r;
+
+        assert(parameters);
+        assert(m);
+
+        r = json_dispatch(parameters, dispatch_table, NULL, 0, &p);
+        if (r < 0)
+                return r;
+
+        if (!streq_ptr(p.service, "io.systemd.DynamicUser"))
+                return varlink_error(link, "io.systemd.UserDatabase.BadService", NULL);
+
+        if (gid_is_valid(p.gid))
+                r = dynamic_user_lookup_uid(m, (uid_t) p.gid, &found_name);
+        else if (p.group_name)
+                r = dynamic_user_lookup_name(m, p.group_name, (uid_t*) &found_gid);
+        else {
+                DynamicUser *d;
+                Iterator i;
+
+                HASHMAP_FOREACH(d, m->dynamic_users, i) {
+                        uid_t uid;
+
+                        r = dynamic_user_current(d, &uid);
+                        if (r == -EAGAIN)
+                                continue;
+                        if (r < 0)
+                                return r;
+
+                        if (!group_match_lookup_parameters(&p, d->name, (gid_t) uid))
+                                continue;
+
+                        if (v) {
+                                r = varlink_notify(link, v);
+                                if (r < 0)
+                                        return r;
+
+                                v = json_variant_unref(v);
+                        }
+
+                        r = build_group_json(d->name, (gid_t) uid, &v);
+                        if (r < 0)
+                                return r;
+                }
+
+                if (!v)
+                        return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+
+                return varlink_reply(link, v);
+        }
+        if (r == -ESRCH)
+                return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+        if (r < 0)
+                return r;
+
+        gid = gid_is_valid(found_gid) ? found_gid : p.gid;
+        gn = found_name ?: p.group_name;
+
+        if (!group_match_lookup_parameters(&p, gn, gid))
+                return varlink_error(link, "io.systemd.UserDatabase.ConflictingRecordFound", NULL);
+
+        r = build_group_json(gn, gid, &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),  JSON_SAFE },
+                { "groupName", JSON_VARIANT_STRING, json_dispatch_const_string, offsetof(LookupParameters, group_name), JSON_SAFE },
+                { "service",   JSON_VARIANT_STRING, json_dispatch_const_string, offsetof(LookupParameters, service),    0         },
+                {}
+        };
+
+        LookupParameters p = {};
+        int r;
+
+        assert(parameters);
+
+        r = json_dispatch(parameters, dispatch_table, NULL, 0, &p);
+        if (r < 0)
+                return r;
+
+        if (!streq_ptr(p.service, "io.systemd.DynamicUser"))
+                return varlink_error(link, "io.systemd.UserDatabase.BadService", NULL);
+
+        /* We don't support auxiliary groups with dynamic users. */
+        return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
+}
+
+int manager_varlink_init(Manager *m) {
+        _cleanup_(varlink_server_unrefp) VarlinkServer *s = NULL;
+        int r;
+
+        assert(m);
+
+        if (m->varlink_server)
+                return 0;
+
+        if (!MANAGER_IS_SYSTEM(m))
+                return 0;
+
+        r = varlink_server_new(&s, VARLINK_SERVER_ACCOUNT_UID);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate varlink server object: %m");
+
+        varlink_server_set_userdata(s, m);
+
+        r = varlink_server_bind_method_many(
+                        s,
+                        "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 register varlink methods: %m");
+
+        (void) mkdir_p("/run/systemd/userdb", 0755);
+
+        r = varlink_server_listen_address(s, "/run/systemd/userdb/io.systemd.DynamicUser", 0666);
+        if (r < 0)
+                return log_error_errno(r, "Failed to bind to varlink socket: %m");
+
+        r = varlink_server_attach_event(s, m->event, SD_EVENT_PRIORITY_NORMAL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to attach varlink connection to event loop: %m");
+
+        m->varlink_server = TAKE_PTR(s);
+        return 0;
+}
+
+void manager_varlink_done(Manager *m) {
+        assert(m);
+
+        m->varlink_server = varlink_server_unref(m->varlink_server);
+}
diff --git a/src/core/core-varlink.h b/src/core/core-varlink.h
new file mode 100644
index 0000000000..89818e2766
--- /dev/null
+++ b/src/core/core-varlink.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+#pragma once
+
+#include "manager.h"
+
+int manager_varlink_init(Manager *m);
+void manager_varlink_done(Manager *m);
diff --git a/src/core/manager.c b/src/core/manager.c
index dbd25af27e..cb0633e2ab 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -29,6 +29,7 @@
 #include "bus-util.h"
 #include "clean-ipc.h"
 #include "clock-util.h"
+#include "core-varlink.h"
 #include "dbus-job.h"
 #include "dbus-manager.h"
 #include "dbus-unit.h"
@@ -44,8 +45,8 @@
 #include "fileio.h"
 #include "fs-util.h"
 #include "hashmap.h"
-#include "io-util.h"
 #include "install.h"
+#include "io-util.h"
 #include "label.h"
 #include "locale-setup.h"
 #include "log.h"
@@ -1346,6 +1347,7 @@ Manager* manager_free(Manager *m) {
         lookup_paths_flush_generator(&m->lookup_paths);
 
         bus_done(m);
+        manager_varlink_done(m);
 
         exec_runtime_vacuum(m);
         hashmap_free(m->exec_runtime_by_id);
@@ -1703,6 +1705,10 @@ int manager_startup(Manager *m, FILE *serialization, FDSet *fds) {
                         log_warning_errno(r, "Failed to deserialized tracked clients, ignoring: %m");
                 m->deserialized_subscribed = strv_free(m->deserialized_subscribed);
 
+                r = manager_varlink_init(m);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to set up Varlink server, ignoring: %m");
+
                 /* Third, fire things up! */
                 manager_coldplug(m);
 
diff --git a/src/core/manager.h b/src/core/manager.h
index 8ca8e3885f..67f9af5fc6 100644
--- a/src/core/manager.h
+++ b/src/core/manager.h
@@ -16,6 +16,7 @@
 #include "list.h"
 #include "prioq.h"
 #include "ratelimit.h"
+#include "varlink.h"
 
 struct libmnt_monitor;
 typedef struct Unit Unit;
@@ -422,6 +423,8 @@ struct Manager {
         unsigned notifygen;
 
         bool honor_device_enumeration;
+
+        VarlinkServer *varlink_server;
 };
 
 static inline usec_t manager_default_timeout_abort_usec(Manager *m) {
diff --git a/src/core/meson.build b/src/core/meson.build
index e0f08c057e..3586838f59 100644
--- a/src/core/meson.build
+++ b/src/core/meson.build
@@ -22,6 +22,8 @@ libcore_sources = '''
         bpf-firewall.h
         cgroup.c
         cgroup.h
+        core-varlink.c
+        core-varlink.h
         dbus-automount.c
         dbus-automount.h
         dbus-cgroup.c