[epiphany/wip/google-safe-browsing: 7/12] gsb-service: Implement URL verification logic



commit 03f6e8f0e4e746f421aaef865ed226d0dc0b21ea
Author: Gabriel Ivascu <gabrielivascu gnome org>
Date:   Mon Sep 18 20:18:53 2017 +0300

    gsb-service: Implement URL verification logic

 lib/safe-browsing/ephy-gsb-service.c |  249 +++++++++++++++++++++++++++++++--
 lib/safe-browsing/ephy-gsb-service.h |   14 ++-
 lib/safe-browsing/ephy-gsb-storage.c |    6 +-
 lib/safe-browsing/ephy-gsb-utils.c   |   54 ++++++++
 lib/safe-browsing/ephy-gsb-utils.h   |    6 +
 5 files changed, 307 insertions(+), 22 deletions(-)
---
diff --git a/lib/safe-browsing/ephy-gsb-service.c b/lib/safe-browsing/ephy-gsb-service.c
index 5d26bae..f9f0bc0 100644
--- a/lib/safe-browsing/ephy-gsb-service.c
+++ b/lib/safe-browsing/ephy-gsb-service.c
@@ -58,22 +58,41 @@ static GParamSpec *obj_properties[LAST_PROP];
 static gboolean ephy_gsb_service_update (EphyGSBService *self);
 
 typedef struct {
-  EphyGSBService *service;
-  GList          *prefixes;
+  EphyGSBService                  *service;
+  GHashTable                      *threats;
+  GList                           *matching_prefixes;
+  GList                           *matching_hashes;
+  EphyGSBServiceVerifyURLCallback  callback;
+  gpointer                         user_data;
 } FindFullHashesData;
 
 static FindFullHashesData *
-find_full_hashes_data_new (EphyGSBService *service,
-                                 GList          *prefixes)
+find_full_hashes_data_new (EphyGSBService                  *service,
+                           GHashTable                      *threats,
+                           GList                           *matching_prefixes,
+                           GList                           *matching_hashes,
+                           EphyGSBServiceVerifyURLCallback  callback,
+                           gpointer                         user_data)
 {
   FindFullHashesData *data;
 
   g_assert (EPHY_IS_GSB_SERVICE (service));
-  g_assert (prefixes);
+  g_assert (threats);
+  g_assert (matching_prefixes);
+  g_assert (matching_hashes);
+  g_assert (callback);
 
   data = g_slice_new (FindFullHashesData);
   data->service = g_object_ref (service);
-  data->prefixes = g_list_copy_deep (prefixes, (GCopyFunc)g_bytes_ref, NULL);
+  data->threats = g_hash_table_ref (threats);
+  data->matching_prefixes = g_list_copy_deep (matching_prefixes,
+                                              (GCopyFunc)g_bytes_ref,
+                                              NULL);
+  data->matching_hashes = g_list_copy_deep (matching_hashes,
+                                            (GCopyFunc)g_bytes_ref,
+                                            NULL);
+  data->callback = callback;
+  data->user_data = user_data;
 
   return data;
 }
@@ -84,7 +103,9 @@ find_full_hashes_data_free (FindFullHashesData *data)
   g_assert (data);
 
   g_object_unref (data->service);
-  g_list_free_full (data->prefixes, (GDestroyNotify)g_bytes_unref);
+  g_hash_table_unref (data->threats);
+  g_list_free_full (data->matching_prefixes, (GDestroyNotify)g_bytes_unref);
+  g_list_free_full (data->matching_hashes, (GDestroyNotify)g_bytes_unref);
   g_slice_free (FindFullHashesData, data);
 }
 
@@ -441,6 +462,7 @@ ephy_gsb_service_find_full_hashes_cb (SoupSession *session,
   JsonNode *body_node = NULL;
   JsonObject *body_obj;
   JsonArray *matches;
+  GList *hashes_lookup = NULL;
   GError *error = NULL;
   const char *negative_duration;
   double duration;
@@ -461,6 +483,7 @@ ephy_gsb_service_find_full_hashes_cb (SoupSession *session,
   body_obj = json_node_get_object (body_node);
   matches = json_object_get_array_member (body_obj, "matches");
 
+  /* Update full hashes in database. */
   for (guint i = 0; i < json_array_get_length (matches); i++) {
     EphyGSBThreatList *list;
     JsonObject *match = json_array_get_object_element (matches, i);
@@ -494,21 +517,44 @@ ephy_gsb_service_find_full_hashes_cb (SoupSession *session,
   /* Update negative cache duration. */
   negative_duration = json_object_get_string_member (body_obj, "negativeCacheDuration");
   sscanf (negative_duration, "%lfs", &duration);
-  for (GList *l = data->prefixes; l && l->data; l = l->next)
+  for (GList *l = data->matching_prefixes; l && l->data; l = l->next)
     ephy_gsb_storage_update_hash_prefix_expiration (self->storage, l->data, floor (duration));
 
   /* TODO: Handle minimumWaitDuration. */
 
+  /* Repeat the full hash verification. */
+  hashes_lookup = ephy_gsb_storage_lookup_full_hashes (self->storage, data->matching_hashes);
+  for (GList *l = hashes_lookup; l && l->data; l = l->next) {
+    EphyGSBHashFullLookup *lookup = (EphyGSBHashFullLookup *)l->data;
+    EphyGSBThreatList *list;
+
+    if (!lookup->expired) {
+      list = ephy_gsb_threat_list_new (lookup->threat_type,
+                                       lookup->platform_type,
+                                       lookup->threat_entry_type,
+                                       NULL, 0);
+      g_hash_table_add (data->threats, list);
+    }
+  }
+
 out:
+  data->callback (data->threats, data->user_data);
+
   if (body_node)
     json_node_unref (body_node);
+  g_list_free_full (hashes_lookup, (GDestroyNotify)ephy_gsb_hash_full_lookup_free);
   find_full_hashes_data_free (data);
 }
 
 static void
-ephy_gsb_service_find_full_hashes (EphyGSBService *self,
-                                   GList          *prefixes)
+ephy_gsb_service_find_full_hashes (EphyGSBService                  *self,
+                                   GHashTable                      *threats,
+                                   GList                           *matching_prefixes,
+                                   GList                           *matching_hashes,
+                                   EphyGSBServiceVerifyURLCallback  callback,
+                                   gpointer                         user_data)
 {
+  FindFullHashesData *data;
   SoupMessage *msg;
   GList *threat_lists;
   JsonNode *body_node;
@@ -518,13 +564,20 @@ ephy_gsb_service_find_full_hashes (EphyGSBService *self,
 
   g_assert (EPHY_IS_GSB_SERVICE (self));
   g_assert (ephy_gsb_storage_is_operable (self->storage));
-  g_assert (prefixes);
-
-  LOG ("Updating full hashes of %u prefixes", g_list_length (prefixes));
+  g_assert (threats);
+  g_assert (matching_prefixes);
+  g_assert (matching_hashes);
+  g_assert (callback);
 
   threat_lists = ephy_gsb_storage_get_threat_lists (self->storage);
-  body_obj = ephy_gsb_utils_make_full_hashes_request (threat_lists, prefixes);
+  if (!threat_lists) {
+    callback (threats, user_data);
+    return;
+  }
 
+  LOG ("Requesting full hashes for %u prefixes", g_list_length (matching_prefixes));
+
+  body_obj = ephy_gsb_utils_make_full_hashes_request (threat_lists, matching_prefixes);
   body_node = json_node_new (JSON_NODE_OBJECT);
   json_node_set_object (body_node, body_obj);
   body = json_to_string (body_node, FALSE);
@@ -532,12 +585,176 @@ ephy_gsb_service_find_full_hashes (EphyGSBService *self,
   url = g_strdup_printf ("%sfullHashes:find?key=%s", API_PREFIX, self->api_key);
   msg = soup_message_new (SOUP_METHOD_POST, url);
   soup_message_set_request (msg, "application/json", SOUP_MEMORY_TAKE, body, strlen (body));
+
+  data = find_full_hashes_data_new (self, threats,
+                                    matching_prefixes, matching_hashes,
+                                    callback, user_data);
   soup_session_queue_message (self->session, msg,
-                              ephy_gsb_service_find_full_hashes_cb,
-                              find_full_hashes_data_new (self, prefixes));
+                              ephy_gsb_service_find_full_hashes_cb, data);
 
   g_free (url);
   json_object_unref (body_obj);
   json_node_unref (body_node);
   g_list_free_full (threat_lists, (GDestroyNotify)ephy_gsb_threat_list_free);
 }
+
+static void
+ephy_gsb_service_verify_hashes (EphyGSBService                  *self,
+                                GList                           *hashes,
+                                GHashTable                      *threats,
+                                EphyGSBServiceVerifyURLCallback  callback,
+                                gpointer                         user_data)
+{
+  GList *cues;
+  GList *prefixes_lookup = NULL;
+  GList *hashes_lookup = NULL;
+  GList *matching_prefixes = NULL;
+  GList *matching_hashes = NULL;
+  GHashTable *matching_prefixes_set;
+  GHashTable *matching_hashes_set;
+  GHashTableIter iter;
+  gpointer value;
+  gboolean has_matching_expired_hashes = FALSE;
+  gboolean has_matching_expired_prefixes = FALSE;
+
+  g_assert (EPHY_IS_GSB_SERVICE (self));
+  g_assert (ephy_gsb_storage_is_operable (self->storage));
+  g_assert (threats);
+  g_assert (hashes);
+  g_assert (callback);
+
+  matching_prefixes_set = g_hash_table_new (g_bytes_hash, g_bytes_equal);
+  matching_hashes_set = g_hash_table_new (g_bytes_hash, g_bytes_equal);
+
+  /* Check for hash prefixes in database that match any of the full hashes. */
+  cues = ephy_gsb_utils_get_hash_cues (hashes);
+  prefixes_lookup = ephy_gsb_storage_lookup_hash_prefixes (self->storage, cues);
+  for (GList *p = prefixes_lookup; p && p->data; p = p->next) {
+    EphyGSBHashPrefixLookup *lookup = (EphyGSBHashPrefixLookup *)p->data;
+
+    for (GList *h = hashes; h && h->data; h = h->next) {
+      if (ephy_gsb_utils_hash_has_prefix (h->data, lookup->prefix)) {
+        value = g_hash_table_lookup (matching_prefixes_set, lookup->prefix);
+
+        /* Consider the prefix expired if it's expired in at least one threat list. */
+        g_hash_table_replace (matching_prefixes_set,
+                              lookup->prefix,
+                              GINT_TO_POINTER (GPOINTER_TO_INT (value) || lookup->negative_expired));
+        g_hash_table_add (matching_hashes_set, h->data);
+      }
+    }
+  }
+
+  /* If there are no database matches, then the URL is safe. */
+  if (g_hash_table_size (matching_hashes_set) == 0) {
+    LOG ("No database match, URL is safe");
+    goto return_result;
+  }
+
+  /* Check for full hashes matches.
+   * All unexpired full hash matches are added directly to the result set.
+   */
+  matching_hashes = g_hash_table_get_keys (matching_hashes_set);
+  hashes_lookup = ephy_gsb_storage_lookup_full_hashes (self->storage, matching_hashes);
+  for (GList *l = hashes_lookup; l && l->data; l = l->next) {
+    EphyGSBHashFullLookup *lookup = (EphyGSBHashFullLookup *)l->data;
+    EphyGSBThreatList *list;
+
+    if (lookup->expired) {
+      has_matching_expired_hashes = TRUE;
+    } else {
+      list = ephy_gsb_threat_list_new (lookup->threat_type,
+                                       lookup->platform_type,
+                                       lookup->threat_entry_type,
+                                       NULL, 0);
+      g_hash_table_add (threats, list);
+    }
+  }
+
+  /* Check for positive cache hit.
+   * That is, there is at least one unexpired full hash match.
+   */
+  if (g_hash_table_size (threats) > 0) {
+    LOG ("Positive cache hit, URL is not safe");
+    goto return_result;
+  }
+
+  /* Check for negative cache hit. That is, there are no expired
+   * full hash matches and all hash prefix matches are negative-unexpired.
+   */
+  g_hash_table_iter_init (&iter, matching_prefixes_set);
+  while (g_hash_table_iter_next (&iter, NULL, &value)) {
+    if (GPOINTER_TO_INT (value) == TRUE) {
+      has_matching_expired_prefixes = TRUE;
+      break;
+    }
+  }
+  if (!has_matching_expired_hashes && !has_matching_expired_prefixes) {
+    LOG ("Negative cache hit, URL is safe");
+    goto return_result;
+  }
+
+  /* At this point we have either expired full hash matches and/or
+   * negative-expired hash prefix matches, so we need to find from
+   * the server whether the URL is safe or not. We do this by updating
+   * the full hashes of the matching prefixes with fresh values from
+   * server and re-checking for positive cache hits.
+   * See ephy_gsb_service_find_full_hashes_cb().
+   */
+  matching_prefixes = g_hash_table_get_keys (matching_prefixes_set);
+  ephy_gsb_service_find_full_hashes (self, threats,
+                                     matching_prefixes, matching_hashes,
+                                     callback, user_data);
+  goto out;
+
+return_result:
+  callback (threats, user_data);
+
+out:
+  g_list_free (matching_prefixes);
+  g_list_free (matching_hashes);
+  g_list_free_full (cues, (GDestroyNotify)g_bytes_unref);
+  g_list_free_full (prefixes_lookup, (GDestroyNotify)ephy_gsb_hash_prefix_lookup_free);
+  g_list_free_full (hashes_lookup, (GDestroyNotify)ephy_gsb_hash_full_lookup_free);
+  g_hash_table_unref (matching_prefixes_set);
+  g_hash_table_unref (matching_hashes_set);
+}
+
+void
+ephy_gsb_service_verify_url (EphyGSBService                  *self,
+                             const char                      *url,
+                             EphyGSBServiceVerifyURLCallback  callback,
+                             gpointer                         user_data)
+{
+  GHashTable *threats;
+  GList *hashes;
+
+  g_assert (EPHY_IS_GSB_SERVICE (self));
+  g_assert (url);
+
+  if (!callback)
+    return;
+
+  threats = g_hash_table_new_full (g_direct_hash,
+                                   (GEqualFunc)ephy_gsb_threat_list_equal,
+                                   (GDestroyNotify)ephy_gsb_threat_list_free,
+                                   NULL);
+
+  /* If the local database is broken or an update is in course, we cannot
+   * really verify the URL, so we have no choice other than to consider it safe.
+   */
+  if (!ephy_gsb_storage_is_operable (self->storage) || self->is_updating) {
+    LOG ("Local GSB storage is not available at the moment, cannot verify URL");
+    callback (threats, user_data);
+    return;
+  }
+
+  hashes = ephy_gsb_utils_compute_hashes (url);
+  if (!hashes) {
+    callback (threats, user_data);
+    return;
+  }
+
+  ephy_gsb_service_verify_hashes (self, hashes, threats, callback, user_data);
+  g_list_free_full (hashes, (GDestroyNotify)g_bytes_unref);
+}
diff --git a/lib/safe-browsing/ephy-gsb-service.h b/lib/safe-browsing/ephy-gsb-service.h
index 8371394..eb7175e 100644
--- a/lib/safe-browsing/ephy-gsb-service.h
+++ b/lib/safe-browsing/ephy-gsb-service.h
@@ -28,7 +28,17 @@ G_BEGIN_DECLS
 
 G_DECLARE_FINAL_TYPE (EphyGSBService, ephy_gsb_service, EPHY, GSB_SERVICE, GObject)
 
-EphyGSBService *ephy_gsb_service_new (const char *api_key,
-                                      const char *db_path);
+/* @threats is a set of EphyGSBThreatList where the URL is considered unsafe.
+ * The caller takes ownership of the GHashTable and needs to free it.
+ */
+typedef void (*EphyGSBServiceVerifyURLCallback) (GHashTable *threats,
+                                                 gpointer    user_data);
+
+EphyGSBService *ephy_gsb_service_new        (const char *api_key,
+                                             const char *db_path);
+void            ephy_gsb_service_verify_url (EphyGSBService                  *self,
+                                             const char                      *url,
+                                             EphyGSBServiceVerifyURLCallback  callback,
+                                             gpointer                         user_data);
 
 G_END_DECLS
diff --git a/lib/safe-browsing/ephy-gsb-storage.c b/lib/safe-browsing/ephy-gsb-storage.c
index 3f6e330..19183a2 100644
--- a/lib/safe-browsing/ephy-gsb-storage.c
+++ b/lib/safe-browsing/ephy-gsb-storage.c
@@ -28,8 +28,6 @@
 #include <glib/gstdio.h>
 #include <string.h>
 
-#define CUE_LEN 4
-
 /* Keep this lower than 200 or else you'll get "too many SQL variables" error
  * in ephy_gsb_storage_insert_batch(). SQLITE_MAX_VARIABLE_NUMBER is hardcoded
  * in sqlite3 as 999.
@@ -1062,7 +1060,7 @@ ephy_gsb_storage_insert_hash_prefix_batch (EphyGSBStorage      *self,
   }
 
   for (gsize k = start; k < end; k += len) {
-    if (!ephy_sqlite_statement_bind_blob (statement, id++, prefixes + k, CUE_LEN, NULL) ||
+    if (!ephy_sqlite_statement_bind_blob (statement, id++, prefixes + k, GSB_CUE_LEN, NULL) ||
         !ephy_sqlite_statement_bind_blob (statement, id++, prefixes + k, len, NULL) ||
         !bind_threat_list_params (statement, list, id, id + 1, id + 2, -1)) {
       g_warning ("Failed to bind values in hash prefix statement");
@@ -1165,7 +1163,7 @@ ephy_gsb_storage_lookup_hash_prefixes (EphyGSBStorage *self,
 
   for (GList *l = cues; l && l->data; l = l->next) {
     ephy_sqlite_statement_bind_blob (statement, id++,
-                                     g_bytes_get_data (l->data, NULL), CUE_LEN,
+                                     g_bytes_get_data (l->data, NULL), GSB_CUE_LEN,
                                      &error);
     if (error) {
       g_warning ("Failed to bind cue value as blob: %s", error->message);
diff --git a/lib/safe-browsing/ephy-gsb-utils.c b/lib/safe-browsing/ephy-gsb-utils.c
index 0b64ff0..5b72182 100644
--- a/lib/safe-browsing/ephy-gsb-utils.c
+++ b/lib/safe-browsing/ephy-gsb-utils.c
@@ -66,6 +66,23 @@ ephy_gsb_threat_list_free (EphyGSBThreatList *list)
   g_slice_free (EphyGSBThreatList, list);
 }
 
+gboolean
+ephy_gsb_threat_list_equal (EphyGSBThreatList *l1,
+                            EphyGSBThreatList *l2)
+{
+  g_assert (l1);
+  g_assert (l2);
+
+  if (g_strcmp0 (l1->threat_type, l2->threat_type) != 0)
+    return FALSE;
+  if (g_strcmp0 (l1->platform_type, l2->platform_type) != 0)
+    return FALSE;
+  if (g_strcmp0 (l1->threat_entry_type, l2->threat_entry_type) != 0)
+    return FALSE;
+
+  return TRUE;
+}
+
 EphyGSBHashPrefixLookup *
 ephy_gsb_hash_prefix_lookup_new (const guint8 *prefix,
                                  gsize         length,
@@ -636,3 +653,40 @@ ephy_gsb_utils_compute_hashes (const char *url)
 
   return g_list_reverse (retval);
 }
+
+GList *
+ephy_gsb_utils_get_hash_cues (GList *hashes)
+{
+  GList *retval = NULL;
+
+  g_assert (hashes);
+
+  for (GList *l = hashes; l && l->data; l = l->next) {
+    const char *hash = g_bytes_get_data (l->data, NULL);
+    retval = g_list_prepend (retval, g_bytes_new (hash, GSB_CUE_LEN));
+  }
+
+  return g_list_reverse (retval);
+}
+
+gboolean
+ephy_gsb_utils_hash_has_prefix (GBytes *hash,
+                                GBytes *prefix)
+{
+  const guint8 *hash_data;
+  const guint8 *prefix_data;
+  gsize prefix_len;
+
+  g_assert (hash);
+  g_assert (prefix);
+
+  hash_data = g_bytes_get_data (hash, NULL);
+  prefix_data = g_bytes_get_data (prefix, &prefix_len);
+
+  for (gsize i = 0; i < prefix_len; i++) {
+    if (hash_data[i] != prefix_data[i])
+      return FALSE;
+  }
+
+  return TRUE;
+}
diff --git a/lib/safe-browsing/ephy-gsb-utils.h b/lib/safe-browsing/ephy-gsb-utils.h
index 759f525..81c06c3 100644
--- a/lib/safe-browsing/ephy-gsb-utils.h
+++ b/lib/safe-browsing/ephy-gsb-utils.h
@@ -25,6 +25,7 @@
 
 G_BEGIN_DECLS
 
+#define GSB_CUE_LEN   4
 #define GSB_HASH_TYPE G_CHECKSUM_SHA256
 #define GSB_HASH_SIZE (g_checksum_type_get_length (GSB_HASH_TYPE))
 
@@ -60,6 +61,8 @@ EphyGSBThreatList       *ephy_gsb_threat_list_new                 (const char *t
                                                                    const char *client_state,
                                                                    gint64      timestamp);
 void                     ephy_gsb_threat_list_free                (EphyGSBThreatList *list);
+gboolean                 ephy_gsb_threat_list_equal               (EphyGSBThreatList *l1,
+                                                                   EphyGSBThreatList *l2);
 
 EphyGSBHashPrefixLookup *ephy_gsb_hash_prefix_lookup_new          (const guint8 *prefix,
                                                                    gsize         length,
@@ -87,5 +90,8 @@ char                    *ephy_gsb_utils_canonicalize              (const char  *
                                                                    char       **path_out,
                                                                    char       **query_out);
 GList                   *ephy_gsb_utils_compute_hashes            (const char *url);
+GList                   *ephy_gsb_utils_get_hash_cues             (GList *hashes);
+gboolean                 ephy_gsb_utils_hash_has_prefix           (GBytes *hash,
+                                                                   GBytes *prefix);
 
 G_END_DECLS


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