document-portal: Implement GetHostPaths

This method allows apps to get path as exists on the host filesystem for
documents exported through the document portal.

This method takes a list of document IDs as a string array and returns
a dictionary mapping document IDs to the paths in the host filesystem.
It is expected an app making this request to have access to given list
of documents.

This is based on initial work made by @JakobDev

Fixes flatpak#475

data/org.freedesktop.portal.Documents.xml

@@ -48,7 +48,7 @@
       bus name org.freedesktop.portal.Documents and the object path
       /org/freedesktop/portal/documents.
 
-      This documentation describes version 4 of this interface.
+      This documentation describes version 5 of this interface.
   -->
   <interface name='org.freedesktop.portal.Documents'>
     <property name="version" type="u" access="read"/>
@@ -273,5 +273,21 @@
       <arg type='s' name='app_id' direction='in'/>
       <arg type='a{say}' name='docs' direction='out'/>
     </method>
+
+    <!--
+        GetHostPaths:
+        @doc_ids: the list of IDs of the files in the document store
+        @paths: a dictionary mapping document IDs to the paths in the host filesystem
+
+        Gets the host filesystem paths for document store entries.
+
+        This call is available inside the sandbox, if the application has the ``read`` permission for the documents.
+
+        This method was added in version 5 of this interface.
+    -->
+    <method name="GetHostPaths">
+      <arg type='as' name='doc_ids' direction='in'/>
+      <arg type='a{say}' name='paths' direction='out'/>
+    </method>
   </interface>
 </node>

document-portal/document-portal.c

@@ -1416,6 +1416,102 @@ portal_list (GDBusMethodInvocation *invocation,
   return TRUE;
 }
 
+const char *
+get_host_path_internal (GDBusMethodInvocation *invocation,
+                        XdpAppInfo            *app_info,
+                        const char            *id,
+                        GError                **error)
+{
+  g_autoptr(PermissionDbEntry) entry = NULL;
+
+  XDP_AUTOLOCK (db);
+
+  entry = permission_db_lookup (db, id);
+
+  if (!entry)
+    {
+      if (error != NULL && *error == NULL)
+        {
+          g_set_error (error,
+                      XDG_DESKTOP_PORTAL_ERROR,
+                      XDG_DESKTOP_PORTAL_ERROR_INVALID_ARGUMENT,
+                      "Invalid ID passed (%s)", id);
+        }
+
+      return NULL;
+    }
+
+  if (!xdp_app_info_is_host (app_info))
+    {
+      g_autofree const char **apps = NULL;
+      const char *app_id = NULL;
+      gboolean app_found = FALSE;
+
+      app_id = xdp_app_info_get_id (app_info);
+
+      apps = permission_db_entry_list_apps (entry);
+      for (size_t i = 0; apps[i] != NULL; i++)
+        {
+          if (g_strcmp0 (app_id, apps[i]) == 0)
+            {
+              app_found = TRUE;
+              break;
+            }
+        }
+
+      if (!app_found)
+        {
+          if (error != NULL && *error == NULL)
+            {
+              g_set_error (error,
+                           XDG_DESKTOP_PORTAL_ERROR,
+                           XDG_DESKTOP_PORTAL_ERROR_NOT_ALLOWED,
+                           "Not enough permissions");
+            }
+
+          return NULL;
+        }
+    }
+
+  return document_entry_get_path (entry);
+}
+
+static gboolean
+portal_get_host_paths (GDBusMethodInvocation *invocation,
+                       GVariant              *parameters,
+                       XdpAppInfo            *app_info)
+{
+  g_autofree const char **id_list = NULL;
+  GVariantBuilder builder;
+  size_t i = 0;
+
+  g_variant_get (parameters, "(^a&s)", &id_list);
+
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("(a{say})"));
+  g_variant_builder_open (&builder, G_VARIANT_TYPE ("a{say}"));
+
+  for (i = 0; id_list[i] != NULL; i++)
+    {
+      g_autoptr(GError) error = NULL;
+      g_autofree const char *path = NULL;
+
+      path = get_host_path_internal (invocation, app_info, id_list[i], &error);
+      if (path == NULL)
+        {
+          g_warning ("Failed to get host path for %s: %s", id_list[i], error->message);
+          continue;
+        }
+
+      g_variant_builder_add (&builder, "{s@ay}", id_list[i], g_variant_new_bytestring (path));
+    }
+
+  g_variant_builder_close (&builder);
+
+  g_dbus_method_invocation_return_value (invocation, g_variant_builder_end (&builder));
+
+  return TRUE;
+}
+
 static void
 peer_died_cb (const char *name)
 {
@@ -1432,7 +1528,7 @@ on_bus_acquired (GDBusConnection *connection,
 
   dbus_api = xdp_dbus_documents_skeleton_new ();
 
-  xdp_dbus_documents_set_version (XDP_DBUS_DOCUMENTS (dbus_api), 4);
+  xdp_dbus_documents_set_version (XDP_DBUS_DOCUMENTS (dbus_api), 5);
 
   g_signal_connect_swapped (dbus_api, "handle-get-mount-point", G_CALLBACK (handle_get_mount_point), NULL);
   g_signal_connect_swapped (dbus_api, "handle-add", G_CALLBACK (handle_method), portal_add);
@@ -1445,6 +1541,7 @@ on_bus_acquired (GDBusConnection *connection,
   g_signal_connect_swapped (dbus_api, "handle-lookup", G_CALLBACK (handle_method), portal_lookup);
   g_signal_connect_swapped (dbus_api, "handle-info", G_CALLBACK (handle_method), portal_info);
   g_signal_connect_swapped (dbus_api, "handle-list", G_CALLBACK (handle_method), portal_list);
+  g_signal_connect_swapped (dbus_api, "handle-get-host-paths", G_CALLBACK (handle_method), portal_get_host_paths);
 
   file_transfer = file_transfer_create ();
   g_dbus_interface_skeleton_set_flags (file_transfer,

tests/test-doc-portal.c

@@ -687,6 +687,57 @@ test_add_named (void)
   assert_doc_not_exist (id1, basename1, "com.test.App2");
 }
 
+static void
+test_get_host_paths (void)
+{
+  g_autofree char *doc_id = NULL;
+  g_autofree char *expected_real_path = NULL;
+  g_autofree char *real_path = NULL;
+  const char *basename = "host-path";
+  GVariant *path = NULL;
+  g_autoptr(GVariant) reply = NULL;
+  g_autoptr(GVariant) result = NULL;
+  g_autoptr(GVariantIter) iter = NULL;
+  GVariantBuilder builder;
+  GError *error = NULL;
+  const gchar* key = NULL;
+
+  if (!check_fuse_or_skip_test ())
+    return;
+
+  doc_id = export_new_file (basename, "content", FALSE);
+
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("(as)"));
+  g_variant_builder_open (&builder, G_VARIANT_TYPE ("as"));
+  g_variant_builder_add (&builder, "s", doc_id);
+  g_variant_builder_close (&builder);
+
+  reply = g_dbus_connection_call_sync (session_bus,
+                                       "org.freedesktop.portal.Documents",
+                                       "/org/freedesktop/portal/documents",
+                                       "org.freedesktop.portal.Documents",
+                                       "GetHostPaths", g_variant_builder_end (&builder),
+                                       G_VARIANT_TYPE ("(a{say})"),
+                                       0, -1,
+                                       NULL,
+                                       &error);
+
+  g_assert_no_error (error);
+  result = g_variant_get_child_value (reply, 0);
+
+  g_assert (g_variant_is_of_type (result, G_VARIANT_TYPE ("a{say}")));
+
+  expected_real_path = g_build_filename (outdir, basename, NULL);
+  iter = g_variant_iter_new (result);
+  while (g_variant_iter_loop (iter, "{&s@ay}", &key, &path))
+    {
+      g_assert_cmpstr (key, ==, doc_id);
+      g_assert_cmpstr (g_variant_get_bytestring (path), ==, expected_real_path);
+      g_variant_unref (path);
+      path = NULL;
+    }
+}
+
 static void
 global_setup (void)
 {
@@ -853,7 +904,7 @@ test_version (void)
   if (!check_fuse_or_skip_test ())
     return;
 
-  g_assert_cmpint (xdp_dbus_documents_get_version (documents), ==, 4);
+  g_assert_cmpint (xdp_dbus_documents_get_version (documents), ==, 5);
 }
 
 int
@@ -871,6 +922,7 @@ main (int argc, char **argv)
   g_test_add_func ("/db/recursive_doc", test_recursive_doc);
   g_test_add_func ("/db/create_docs", test_create_docs);
   g_test_add_func ("/db/add_named", test_add_named);
+  g_test_add_func ("/db/get_host_paths", test_get_host_paths);
 
   global_setup ();