libmalcontent: Add support for filtering by content type

This is useful for example if blacklisting all apps that can
handle certain content types is desired.

Signed-off-by: Andre Moreira Magalhaes <andre@endlessm.com>

libmalcontent/app-filter.c

@@ -1,6 +1,6 @@
 /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
  *
- * Copyright © 2018 Endless Mobile, Inc.
+ * Copyright © 2018-2019 Endless Mobile, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -18,6 +18,7 @@
  *
  * Authors:
  *  - Philip Withnall <withnall@endlessm.com>
+ *  - Andre Moreira Magalhaes <andre@endlessm.com>
  */
 
 #include "config.h"
@@ -142,6 +143,34 @@ mct_app_filter_is_path_allowed (MctAppFilter *filter,
     }
 }
 
+/* Check whether a given @ref is a valid flatpak ref.
+ *
+ * For simplicity and to avoid duplicating the whole logic behind
+ * flatpak_ref_parse() this method will only check whether:
+ * - the @ref contains exactly 3 slash chars
+ * - the @ref starts with either app/ or runtime/
+ * - the name, arch and branch components of the @ref are not empty
+ *
+ * We avoid using flatpak_ref_parse() to allow for libflatpak
+ * to depend on malcontent without causing a cyclic dependency.
+ */
+static gboolean
+is_valid_flatpak_ref (const gchar *ref)
+{
+  g_auto(GStrv) parts = NULL;
+
+  if (ref == NULL)
+    return FALSE;
+
+  parts = g_strsplit (ref, "/", 0);
+  return (g_strv_length (parts) == 4 &&
+          (strcmp (parts[0], "app") == 0 ||
+           strcmp (parts[0], "runtime") == 0) &&
+          *parts[1] != '\0' &&
+          *parts[2] != '\0' &&
+          *parts[3] != '\0');
+}
+
 /**
  * mct_app_filter_is_flatpak_ref_allowed:
  * @filter: an #MctAppFilter
@@ -161,6 +190,7 @@ mct_app_filter_is_flatpak_ref_allowed (MctAppFilter *filter,
   g_return_val_if_fail (filter != NULL, FALSE);
   g_return_val_if_fail (filter->ref_count >= 1, FALSE);
   g_return_val_if_fail (app_ref != NULL, FALSE);
+  g_return_val_if_fail (is_valid_flatpak_ref (app_ref), FALSE);
 
   gboolean ref_in_list = g_strv_contains ((const gchar * const *) filter->app_list,
                                           app_ref);
@@ -205,9 +235,8 @@ mct_app_filter_is_flatpak_app_allowed (MctAppFilter *filter,
   gboolean id_in_list = FALSE;
   for (gsize i = 0; filter->app_list[i] != NULL; i++)
     {
-      /* Avoid using flatpak_ref_parse() to avoid a dependency on libflatpak
+      if (is_valid_flatpak_ref (filter->app_list[i]) &&
-       * just for that one function. */
+          g_str_has_prefix (filter->app_list[i], "app/") &&
-      if (g_str_has_prefix (filter->app_list[i], "app/") &&
           strncmp (filter->app_list[i] + strlen ("app/"), app_id, app_id_len) == 0 &&
           filter->app_list[i][strlen ("app/") + app_id_len] == '/')
         {
@@ -246,6 +275,7 @@ mct_app_filter_is_appinfo_allowed (MctAppFilter *filter,
                                    GAppInfo     *app_info)
 {
   g_autofree gchar *abs_path = NULL;
+  const gchar * const *types = NULL;
 
   g_return_val_if_fail (filter != NULL, FALSE);
   g_return_val_if_fail (filter->ref_count >= 1, FALSE);
@@ -257,6 +287,13 @@ mct_app_filter_is_appinfo_allowed (MctAppFilter *filter,
       !mct_app_filter_is_path_allowed (filter, abs_path))
     return FALSE;
 
+  types = g_app_info_get_supported_types (app_info);
+  for (gsize i = 0; types != NULL && types[i] != NULL; i++)
+    {
+      if (!mct_app_filter_is_content_type_allowed (filter, types[i]))
+        return FALSE;
+    }
+
   if (G_IS_DESKTOP_APP_INFO (app_info))
     {
       g_autofree gchar *flatpak_app = NULL;
@@ -296,6 +333,67 @@ mct_app_filter_is_appinfo_allowed (MctAppFilter *filter,
   return TRUE;
 }
 
+/* Check whether a given @content_type is valid.
+ *
+ * For simplicity this method will only check whether:
+ * - the @content_type contains exactly 1 slash char
+ * - the @content_type does not start with a slash char
+ * - the type and subtype components of the @content_type are not empty
+ */
+static gboolean
+is_valid_content_type (const gchar *content_type)
+{
+  g_auto(GStrv) parts = NULL;
+
+  if (content_type == NULL)
+    return FALSE;
+
+  parts = g_strsplit (content_type, "/", 0);
+  return (g_strv_length (parts) == 2 &&
+          *parts[0] != '\0' &&
+          *parts[1] != '\0');
+}
+
+/**
+ * mct_app_filter_is_content_type_allowed:
+ * @filter: an #MctAppFilter
+ * @content_type: content type to check
+ *
+ * Check whether apps handling the given @content_type are allowed to be run
+ * according to this app filter.
+ *
+ * Note that this method doesn’t match content subtypes. For example, if
+ * `application/xml` is added to the blacklist but `application/xspf+xml` is not,
+ * a check for whether `application/xspf+xml` is blacklisted would return false.
+ *
+ * Returns: %TRUE if the user this @filter corresponds to is allowed to run
+ *    programs handling @content_type according to the @filter policy;
+ *    %FALSE otherwise
+ * Since: 0.4.0
+ */
+gboolean
+mct_app_filter_is_content_type_allowed (MctAppFilter *filter,
+                                        const gchar  *content_type)
+{
+  g_return_val_if_fail (filter != NULL, FALSE);
+  g_return_val_if_fail (filter->ref_count >= 1, FALSE);
+  g_return_val_if_fail (content_type != NULL, FALSE);
+  g_return_val_if_fail (is_valid_content_type (content_type), FALSE);
+
+  gboolean ref_in_list = g_strv_contains ((const gchar * const *) filter->app_list,
+                                          content_type);
+
+  switch (filter->app_list_type)
+    {
+    case MCT_APP_FILTER_LIST_BLACKLIST:
+      return !ref_in_list;
+    case MCT_APP_FILTER_LIST_WHITELIST:
+      return ref_in_list;
+    default:
+      g_assert_not_reached ();
+    }
+}
+
 static gint
 strcmp_cb (gconstpointer a,
            gconstpointer b)
@@ -700,12 +798,44 @@ mct_app_filter_builder_blacklist_flatpak_ref (MctAppFilterBuilder *builder,
   g_return_if_fail (_builder != NULL);
   g_return_if_fail (_builder->blacklist != NULL);
   g_return_if_fail (app_ref != NULL);
+  g_return_if_fail (is_valid_flatpak_ref (app_ref));
 
   if (!g_ptr_array_find_with_equal_func (_builder->blacklist,
                                          app_ref, g_str_equal, NULL))
     g_ptr_array_add (_builder->blacklist, g_strdup (app_ref));
 }
 
+/**
+ * mct_app_filter_builder_blacklist_content_type:
+ * @builder: an initialised #MctAppFilterBuilder
+ * @content_type: a content type to blacklist
+ *
+ * Add @content_type to the blacklist of content types in the filter under
+ * construction. The @content_type will not be added again if it’s already been
+ * added.
+ *
+ * Note that this method doesn’t handle content subtypes. For example, if
+ * `application/xml` is added to the blacklist but `application/xspf+xml` is not,
+ * a check for whether `application/xspf+xml` is blacklisted would return false.
+ *
+ * Since: 0.4.0
+ */
+void
+mct_app_filter_builder_blacklist_content_type (MctAppFilterBuilder *builder,
+                                               const gchar         *content_type)
+{
+  MctAppFilterBuilderReal *_builder = (MctAppFilterBuilderReal *) builder;
+
+  g_return_if_fail (_builder != NULL);
+  g_return_if_fail (_builder->blacklist != NULL);
+  g_return_if_fail (content_type != NULL);
+  g_return_if_fail (is_valid_content_type (content_type));
+
+  if (!g_ptr_array_find_with_equal_func (_builder->blacklist,
+                                         content_type, g_str_equal, NULL))
+    g_ptr_array_add (_builder->blacklist, g_strdup (content_type));
+}
+
 /**
  * mct_app_filter_builder_set_oars_value:
  * @builder: an initialised #MctAppFilterBuilder

libmalcontent/app-filter.h

@@ -1,6 +1,6 @@
 /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
  *
- * Copyright © 2018 Endless Mobile, Inc.
+ * Copyright © 2018-2019 Endless Mobile, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -18,6 +18,7 @@
  *
  * Authors:
  *  - Philip Withnall <withnall@endlessm.com>
+ *  - Andre Moreira Magalhaes <andre@endlessm.com>
  */
 
 #pragma once
@@ -109,6 +110,8 @@ gboolean mct_app_filter_is_flatpak_app_allowed (MctAppFilter *filter,
                                                 const gchar  *app_id);
 gboolean mct_app_filter_is_appinfo_allowed     (MctAppFilter *filter,
                                                 GAppInfo     *app_info);
+gboolean mct_app_filter_is_content_type_allowed (MctAppFilter *filter,
+                                                 const gchar  *content_type);
 
 const gchar           **mct_app_filter_get_oars_sections (MctAppFilter *filter);
 MctAppFilterOarsValue   mct_app_filter_get_oars_value    (MctAppFilter *filter,
@@ -182,6 +185,9 @@ void mct_app_filter_builder_blacklist_path        (MctAppFilterBuilder   *builde
                                                    const gchar           *path);
 void mct_app_filter_builder_blacklist_flatpak_ref (MctAppFilterBuilder *builder,
                                                    const gchar         *app_ref);
+void mct_app_filter_builder_blacklist_content_type (MctAppFilterBuilder *builder,
+                                                    const gchar         *content_type);
+
 void mct_app_filter_builder_set_oars_value        (MctAppFilterBuilder   *builder,
                                                    const gchar           *oars_section,
                                                    MctAppFilterOarsValue  value);