Merge branch 'wip/smcv/gdbus-cross-namespace' into 'main'

GDBus: Use namespace-friendly protocol for Linux message buses, and optionally other connections

See merge request GNOME/glib!2832

10 files changed, 70 insertions, 24 deletions

diff --git a/gio/gdbusauth.c b/gio/gdbusauth.c
index 89cbbf67c..671036805 100644
--- a/gio/gdbusauth.c
+++ b/gio/gdbusauth.c
@@ -417,6 +417,7 @@ hexdecode (const gchar  *str,
 static GDBusAuthMechanism *
 client_choose_mech_and_send_initial_response (GDBusAuth           *auth,
                                               GCredentials        *credentials_that_were_sent,
+                                              GDBusConnectionFlags conn_flags,
                                               const gchar* const  *supported_auth_mechs,
                                               GPtrArray           *attempted_auth_mechs,
                                               GDataOutputStream   *dos,
@@ -507,6 +508,7 @@ client_choose_mech_and_send_initial_response (GDBusAuth           *auth,
 
   initial_response_len = 0;
   initial_response = _g_dbus_auth_mechanism_client_initiate (mech,
+                                                             conn_flags,
                                                              &initial_response_len);
 #if 0
   g_printerr ("using auth mechanism with name '%s' of type '%s' with initial response '%s'\n",
@@ -556,6 +558,7 @@ typedef enum
 gchar *
 _g_dbus_auth_run_client (GDBusAuth     *auth,
                          GDBusAuthObserver     *observer,
+                         GDBusConnectionFlags conn_flags,
                          GDBusCapabilityFlags offered_capabilities,
                          GDBusCapabilityFlags *out_negotiated_capabilities,
                          GCancellable  *cancellable,
@@ -574,6 +577,9 @@ _g_dbus_auth_run_client (GDBusAuth     *auth,
   ClientState state;
   GDBusCapabilityFlags negotiated_capabilities;
 
+  g_return_val_if_fail ((conn_flags & G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_CLIENT), NULL);
+  g_return_val_if_fail (!(conn_flags & G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_SERVER), NULL);
+
   debug_print ("CLIENT: initiating");
 
   _g_dbus_auth_add_mechs (auth, observer);
@@ -667,6 +673,7 @@ _g_dbus_auth_run_client (GDBusAuth     *auth,
           g_free (line);
           mech = client_choose_mech_and_send_initial_response (auth,
                                                                credentials,
+                                                               conn_flags,
                                                                (const gchar* const *) supported_auth_mechs,
                                                                attempted_auth_mechs,
                                                                dos,
diff --git a/gio/gdbusauth.h b/gio/gdbusauth.h
index 30140fb98..8fa89444a 100644
--- a/gio/gdbusauth.h
+++ b/gio/gdbusauth.h
@@ -78,6 +78,7 @@ gboolean    _g_dbus_auth_run_server (GDBusAuth             *auth,
 
 gchar      *_g_dbus_auth_run_client (GDBusAuth     *auth,
                                      GDBusAuthObserver     *observer,
+                                     GDBusConnectionFlags   conn_flags,
                                      GDBusCapabilityFlags offered_capabilities,
                                      GDBusCapabilityFlags *out_negotiated_capabilities,
                                      GCancellable  *cancellable,
diff --git a/gio/gdbusauthmechanism.c b/gio/gdbusauthmechanism.c
index 38d7210e5..6e494dbd9 100644
--- a/gio/gdbusauthmechanism.c
+++ b/gio/gdbusauthmechanism.c
@@ -301,11 +301,13 @@ _g_dbus_auth_mechanism_client_get_state (GDBusAuthMechanism *mechanism)
 }
 
 gchar *
-_g_dbus_auth_mechanism_client_initiate (GDBusAuthMechanism *mechanism,
-                                        gsize              *out_initial_response_len)
+_g_dbus_auth_mechanism_client_initiate (GDBusAuthMechanism   *mechanism,
+                                        GDBusConnectionFlags  conn_flags,
+                                        gsize                *out_initial_response_len)
 {
   g_return_val_if_fail (G_IS_DBUS_AUTH_MECHANISM (mechanism), NULL);
   return G_DBUS_AUTH_MECHANISM_GET_CLASS (mechanism)->client_initiate (mechanism,
+                                                                       conn_flags,
                                                                        out_initial_response_len);
 }
 
diff --git a/gio/gdbusauthmechanism.h b/gio/gdbusauthmechanism.h
index bc4afe74d..f0edd19a3 100644
--- a/gio/gdbusauthmechanism.h
+++ b/gio/gdbusauthmechanism.h
@@ -93,6 +93,7 @@ struct _GDBusAuthMechanismClass
   /* functions for client-side authentication */
   GDBusAuthMechanismState   (*client_get_state)         (GDBusAuthMechanism   *mechanism);
   gchar                    *(*client_initiate)          (GDBusAuthMechanism   *mechanism,
+                                                         GDBusConnectionFlags  conn_flags,
                                                          gsize                *out_initial_response_len);
   void                      (*client_data_receive)      (GDBusAuthMechanism   *mechanism,
                                                          const gchar          *data,
@@ -140,6 +141,7 @@ void                      _g_dbus_auth_mechanism_server_shutdown          (GDBus
 
 GDBusAuthMechanismState   _g_dbus_auth_mechanism_client_get_state         (GDBusAuthMechanism   *mechanism);
 gchar                    *_g_dbus_auth_mechanism_client_initiate          (GDBusAuthMechanism   *mechanism,
+                                                                           GDBusConnectionFlags  conn_flags,
                                                                            gsize                *out_initial_response_len);
 void                      _g_dbus_auth_mechanism_client_data_receive      (GDBusAuthMechanism   *mechanism,
                                                                            const gchar          *data,
diff --git a/gio/gdbusauthmechanismanon.c b/gio/gdbusauthmechanismanon.c
index 903907f86..5f59d4a61 100644
--- a/gio/gdbusauthmechanismanon.c
+++ b/gio/gdbusauthmechanismanon.c
@@ -60,6 +60,7 @@ static gchar                   *mechanism_server_get_reject_reason  (GDBusAuthMe
 static void                     mechanism_server_shutdown           (GDBusAuthMechanism   *mechanism);
 static GDBusAuthMechanismState  mechanism_client_get_state          (GDBusAuthMechanism   *mechanism);
 static gchar                   *mechanism_client_initiate           (GDBusAuthMechanism   *mechanism,
+                                                                     GDBusConnectionFlags  conn_flags,
                                                                      gsize                *out_initial_response_len);
 static void                     mechanism_client_data_receive       (GDBusAuthMechanism   *mechanism,
                                                                      const gchar          *data,
@@ -261,6 +262,7 @@ mechanism_client_get_state (GDBusAuthMechanism   *mechanism)
 
 static gchar *
 mechanism_client_initiate (GDBusAuthMechanism   *mechanism,
+                           GDBusConnectionFlags  conn_flags,
                            gsize                *out_initial_response_len)
 {
   GDBusAuthMechanismAnon *m = G_DBUS_AUTH_MECHANISM_ANON (mechanism);
diff --git a/gio/gdbusauthmechanismexternal.c b/gio/gdbusauthmechanismexternal.c
index a465862d1..6fe8b1bed 100644
--- a/gio/gdbusauthmechanismexternal.c
+++ b/gio/gdbusauthmechanismexternal.c
@@ -68,6 +68,7 @@ static gchar                   *mechanism_server_get_reject_reason  (GDBusAuthMe
 static void                     mechanism_server_shutdown           (GDBusAuthMechanism   *mechanism);
 static GDBusAuthMechanismState  mechanism_client_get_state          (GDBusAuthMechanism   *mechanism);
 static gchar                   *mechanism_client_initiate           (GDBusAuthMechanism   *mechanism,
+                                                                     GDBusConnectionFlags  conn_flags,
                                                                      gsize                *out_initial_response_len);
 static void                     mechanism_client_data_receive       (GDBusAuthMechanism   *mechanism,
                                                                      const gchar          *data,
@@ -360,38 +361,51 @@ mechanism_client_get_state (GDBusAuthMechanism   *mechanism)
 
 static gchar *
 mechanism_client_initiate (GDBusAuthMechanism   *mechanism,
+                           GDBusConnectionFlags  conn_flags,
                            gsize                *out_initial_response_len)
 {
   GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
   gchar *initial_response = NULL;
-#if defined(G_OS_UNIX)
-  GCredentials *credentials;
-#endif
 
   g_return_val_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism), NULL);
   g_return_val_if_fail (!m->priv->is_server && !m->priv->is_client, NULL);
 
   m->priv->is_client = TRUE;
-  m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_REJECTED;
+  m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_WAITING_FOR_DATA;
 
   *out_initial_response_len = 0;
 
-  /* return the uid */
+  if (conn_flags & G_DBUS_CONNECTION_FLAGS_CROSS_NAMESPACE)
+    {
+      /* If backwards-compatibility with GDBus servers < 2.73.3 is not a
+       * concern, we do not send an initial response, because there is
+       * no way to express an empty authorization identity this way.
+       * Instead, we'll reply to the server's first (empty) challenge
+       * with an empty authorization identity in our first response.  */
+      g_debug ("Using cross-namespace EXTERNAL authentication (this will deadlock if server is GDBus < 2.73.3)");
+    }
+  else
+    {
+      /* Send the Unix uid or Windows SID as an initial response.
+       * This is the only thing that is interoperable with GDBus 2.73.3
+       * servers. */
 #if defined(G_OS_UNIX)
-  credentials = _g_dbus_auth_mechanism_get_credentials (mechanism);
-  g_assert (credentials != NULL);
+      GCredentials *credentials;
+
+      credentials = _g_dbus_auth_mechanism_get_credentials (mechanism);
+      g_assert (credentials != NULL);
 
-  initial_response = g_strdup_printf ("%" G_GINT64_FORMAT, (gint64) g_credentials_get_unix_user (credentials, NULL));
+      initial_response = g_strdup_printf ("%" G_GINT64_FORMAT, (gint64) g_credentials_get_unix_user (credentials, NULL));
 #elif defined(G_OS_WIN32)
-  initial_response = _g_win32_current_process_sid_string (NULL);
+      initial_response = _g_win32_current_process_sid_string (NULL);
 #else
-#ifdef __GNUC__
-#pragma GCC diagnostic push
-#pragma GCC diagnostic warning "-Wcpp"
-#warning Dont know how to send credentials on this OS. The EXTERNAL D-Bus authentication mechanism will not work.
-#pragma GCC diagnostic pop
-#endif
+      /* GDBus < 2.73.3 servers can't have worked on this platform anyway,
+       * so it isn't a regression to behave as though
+       * G_DBUS_CONNECTION_FLAGS_CROSS_NAMESPACE had been set. */
+      g_debug ("Unknown platform, cannot use initial response in EXTERNAL");
 #endif
+    }
+
   if (initial_response)
     {
       m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_ACCEPTED;
@@ -411,8 +425,9 @@ mechanism_client_data_receive (GDBusAuthMechanism   *mechanism,
   g_return_if_fail (m->priv->is_client && !m->priv->is_server);
   g_return_if_fail (m->priv->state == G_DBUS_AUTH_MECHANISM_STATE_WAITING_FOR_DATA);
 
-  /* can never end up here because we are never in the WAITING_FOR_DATA state */
-  g_assert_not_reached ();
+  /* The server sent us a challenge, which should normally
+   * be empty.  We respond with our authorization identity.  */
+  m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_HAVE_DATA_TO_SEND;
 }
 
 static gchar *
@@ -425,10 +440,11 @@ mechanism_client_data_send (GDBusAuthMechanism   *mechanism,
   g_return_val_if_fail (m->priv->is_client && !m->priv->is_server, NULL);
   g_return_val_if_fail (m->priv->state == G_DBUS_AUTH_MECHANISM_STATE_HAVE_DATA_TO_SEND, NULL);
 
-  /* can never end up here because we are never in the HAVE_DATA_TO_SEND state */
-  g_assert_not_reached ();
-
-  return NULL;
+  /* We respond to the server's challenge by sending our
+   * authorization identity, which is the empty string, meaning
+   * whoever the out-of-band credentials say we are.  */
+  *out_data_len = 0;
+  return g_strdup ("");
 }
 
 static void
diff --git a/gio/gdbusauthmechanismsha1.c b/gio/gdbusauthmechanismsha1.c
index a11c9f38d..fb6488a2a 100644
--- a/gio/gdbusauthmechanismsha1.c
+++ b/gio/gdbusauthmechanismsha1.c
@@ -119,6 +119,7 @@ static gchar                   *mechanism_server_get_reject_reason  (GDBusAuthMe
 static void                     mechanism_server_shutdown           (GDBusAuthMechanism   *mechanism);
 static GDBusAuthMechanismState  mechanism_client_get_state          (GDBusAuthMechanism   *mechanism);
 static gchar                   *mechanism_client_initiate           (GDBusAuthMechanism   *mechanism,
+                                                                     GDBusConnectionFlags  conn_flags,
                                                                      gsize                *out_initial_response_len);
 static void                     mechanism_client_data_receive       (GDBusAuthMechanism   *mechanism,
                                                                      const gchar          *data,
@@ -1160,6 +1161,7 @@ mechanism_client_get_state (GDBusAuthMechanism   *mechanism)
 
 static gchar *
 mechanism_client_initiate (GDBusAuthMechanism   *mechanism,
+                           GDBusConnectionFlags  conn_flags,
                            gsize                *out_initial_response_len)
 {
   GDBusAuthMechanismSha1 *m = G_DBUS_AUTH_MECHANISM_SHA1 (mechanism);
diff --git a/gio/gdbusconnection.c b/gio/gdbusconnection.c
index f0d50f7d8..663cd95ab 100644
--- a/gio/gdbusconnection.c
+++ b/gio/gdbusconnection.c
@@ -2569,6 +2569,7 @@ initable_init (GInitable     *initable,
       connection->auth = _g_dbus_auth_new (connection->stream);
       connection->guid = _g_dbus_auth_run_client (connection->auth,
                                                   connection->authentication_observer,
+                                                  connection->flags,
                                                   get_offered_capabilities_max (connection),
                                                   &connection->capabilities,
                                                   cancellable,
@@ -7368,6 +7369,9 @@ get_uninitialized_connection (GBusType       bus_type,
       ret = g_object_new (G_TYPE_DBUS_CONNECTION,
                           "address", address,
                           "flags", G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_CLIENT |
+#ifdef __linux__
+                                   G_DBUS_CONNECTION_FLAGS_CROSS_NAMESPACE |
+#endif
                                    G_DBUS_CONNECTION_FLAGS_MESSAGE_BUS_CONNECTION,
                           "exit-on-close", TRUE,
                           NULL);
diff --git a/gio/gioenums.h b/gio/gioenums.h
index fb5944996..3ba1d5b75 100644
--- a/gio/gioenums.h
+++ b/gio/gioenums.h
@@ -1216,6 +1216,12 @@ typedef enum
  * delayed until g_dbus_connection_start_message_processing() is called.
  * @G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_REQUIRE_SAME_USER: When authenticating
  * as a server, require the UID of the peer to be the same as the UID of the server. (Since: 2.68)
+ * @G_DBUS_CONNECTION_FLAGS_CROSS_NAMESPACE: When authenticating, try to use
+ *  protocols that work across a Linux user namespace boundary, even if this
+ *  reduces interoperability with older D-Bus implementations. This currently
+ *  affects client-side `EXTERNAL` authentication, for which this flag makes
+ *  connections to a server in another user namespace succeed, but causes
+ *  a deadlock when connecting to a GDBus server older than 2.73.3. Since: 2.74
  *
  * Flags used when creating a new #GDBusConnection.
  *
@@ -1228,7 +1234,8 @@ typedef enum {
   G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_ALLOW_ANONYMOUS = (1<<2),
   G_DBUS_CONNECTION_FLAGS_MESSAGE_BUS_CONNECTION = (1<<3),
   G_DBUS_CONNECTION_FLAGS_DELAY_MESSAGE_PROCESSING = (1<<4),
-  G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_REQUIRE_SAME_USER GLIB_AVAILABLE_ENUMERATOR_IN_2_68 = (1<<5)
+  G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_REQUIRE_SAME_USER GLIB_AVAILABLE_ENUMERATOR_IN_2_68 = (1<<5),
+  G_DBUS_CONNECTION_FLAGS_CROSS_NAMESPACE GLIB_AVAILABLE_ENUMERATOR_IN_2_74 = (1<<6)
 } GDBusConnectionFlags;
 
 /**
diff --git a/gio/tests/gdbus-connection.c b/gio/tests/gdbus-connection.c
index 61ca5c4b7..d04dd0446 100644
--- a/gio/tests/gdbus-connection.c
+++ b/gio/tests/gdbus-connection.c
@@ -1234,6 +1234,9 @@ test_connection_basic (void)
                  flags == G_DBUS_CAPABILITY_FLAGS_UNIX_FD_PASSING);
 
   connection_flags = g_dbus_connection_get_flags (connection);
+  /* Ignore G_DBUS_CONNECTION_FLAGS_CROSS_NAMESPACE, it's an
+   * implementation detail whether we set it */
+  connection_flags &= ~G_DBUS_CONNECTION_FLAGS_CROSS_NAMESPACE;
   g_assert_cmpint (connection_flags, ==,
                    G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_CLIENT |
                    G_DBUS_CONNECTION_FLAGS_MESSAGE_BUS_CONNECTION);