Get next SEI only once (#438)

The next available SEI is searched for in several places. It is
only necessary to do it once, when preparing for validation.

This commit passes that SEI on for further validation.

Author: bjornvolcker

lib/src/sv_auth.c

@@ -51,6 +51,7 @@ static void
 detect_lost_sei(signed_video_t *self);
 static bool
 verify_hashes_with_hash_list(signed_video_t *self,
+    bu_list_item_t *sei,
     int *num_expected,
     int *num_received,
     bool order_ok);
@@ -61,9 +62,9 @@ set_validation_status_of_pending_items_used_in_gop_hash(signed_video_t *self,
 static bool
 verify_hashes_without_sei(signed_video_t *self, int num_skips);
 static void
-validate_authenticity(signed_video_t *self);
+validate_authenticity(signed_video_t *self, bu_list_item_t *sei);
 static svrc_t
-prepare_for_validation(signed_video_t *self);
+prepare_for_validation(signed_video_t *self, bu_list_item_t **sei);
 static bool
 is_recurrent_data_decoded(signed_video_t *self);
 static bool
@@ -341,11 +342,12 @@ extend_partial_gop(signed_video_t *self, const bu_list_item_t *sei)
  * Returns false if we failed verifying hashes. Otherwise, returns true. */
 static bool
 verify_hashes_with_hash_list(signed_video_t *self,
+    bu_list_item_t *sei,
     int *num_expected,
     int *num_received,
     bool order_ok)
 {
-  assert(self);
+  assert(self && sei);
 
   const size_t hash_size = self->verify_data->hash_size;
   assert(hash_size > 0);
@@ -361,12 +363,6 @@ verify_hashes_with_hash_list(signed_video_t *self,
 
   bu_list_print(bu_list);
 
-  // Get the SEI associated with the oldest pending GOP.
-  bu_list_item_t *sei = bu_list_get_next_sei_item(bu_list);
-  // TODO: Investigate if we can end up without finding a SEI. If so, should we fail the validation
-  // or call verify_hashes_without_sei()?
-  if (!sei) return false;
-
   // First of all we need to know if the SEI itself is authentic, that is, the SEI |document_hash|
   // has successfully been verified (= 1). If the document could not be verified sucessfully, that
   // is, the SEI is invalid, all BUs become invalid. Hence, verify_hashes_without_sei().
@@ -564,14 +560,16 @@ set_validation_status_of_pending_items_used_in_gop_hash(signed_video_t *self,
  *    to reflect the total number of expected and received BUs.
  */
 static bool
-verify_hashes_with_sei(signed_video_t *self, int *num_expected, int *num_received)
+verify_hashes_with_sei(signed_video_t *self,
+    bu_list_item_t *sei,
+    int *num_expected,
+    int *num_received)
 {
   assert(self);
 
   int num_expected_hashes = -1;
   int num_received_hashes = -1;
   char validation_status = 'P';
-  bu_list_item_t *sei = bu_list_get_next_sei_item(self->bu_list);
 
   bool gop_is_ok = verify_gop_hash(self);
   bool order_ok = verify_linked_hash(self);
@@ -588,7 +586,7 @@ verify_hashes_with_sei(signed_video_t *self, int *num_expected, int *num_receive
     if (validation_status != '.' && self->gop_info->list_idx > 0) {
       // Extend partial GOP with more items, since the failure can be due to added BUs.
       extend_partial_gop(self, sei);
-      return verify_hashes_with_hash_list(self, num_expected, num_received, order_ok);
+      return verify_hashes_with_hash_list(self, sei, num_expected, num_received, order_ok);
     }
   } else if (self->gop_info->verified_signature_hash == 0) {
     validation_status = 'N';
@@ -747,7 +745,7 @@ verify_hashes_without_sei(signed_video_t *self, int num_skips)
  * - Update |latest_validation| with the validation result.
  */
 static void
-validate_authenticity(signed_video_t *self)
+validate_authenticity(signed_video_t *self, bu_list_item_t *sei)
 {
   assert(self);
 
@@ -768,7 +766,7 @@ validate_authenticity(signed_video_t *self)
     // verify this GOP. Marking this GOP as not OK by verify_hashes_without_sei().
     verify_success = verify_hashes_without_sei(self, self->gop_info->num_sent);
   } else {
-    verify_success = verify_hashes_with_sei(self, &num_expected, &num_received);
+    verify_success = verify_hashes_with_sei(self, sei, &num_expected, &num_received);
     // Set |latest_validated_gop| to recived gop counter for the next validation.
     self->gop_info->latest_validated_gop = self->gop_info->current_partial_gop;
   }
@@ -921,7 +919,7 @@ prepare_golden_sei(signed_video_t *self, bu_list_item_t *sei)
     SV_THROW(hash_and_add_for_auth(self, sei));
     memcpy(verify_data->hash, sei->hash, verify_data->hash_size);
 
-    SV_THROW(prepare_for_validation(self));
+    SV_THROW(prepare_for_validation(self, &sei));
   SV_CATCH()
   SV_DONE(status)
 
@@ -938,7 +936,7 @@ prepare_golden_sei(signed_video_t *self, bu_list_item_t *sei)
  * 5) verify the associated hash using the signature.
  */
 static svrc_t
-prepare_for_validation(signed_video_t *self)
+prepare_for_validation(signed_video_t *self, bu_list_item_t **sei)
 {
   assert(self);
 
@@ -947,23 +945,26 @@ prepare_for_validation(signed_video_t *self)
   sign_or_verify_data_t *verify_data = self->verify_data;
   const size_t hash_size = verify_data->hash_size;
 
+  *sei = bu_list_get_next_sei_item(bu_list);
+  if (!(*sei)) {
+    // No reason to proceed with preparations if no pending SEI is found.
+    return SV_OK;
+  }
+
   svrc_t status = SV_UNKNOWN_FAILURE;
   SV_TRY()
-    bu_list_item_t *sei = bu_list_get_next_sei_item(bu_list);
-    if (sei) {
-      sei->in_validation = true;
-      if (!sei->has_been_decoded) {
-        // Decode the SEI and set signature->hash
-        self->latest_validation->public_key_has_changed = false;
-        const uint8_t *tlv_data = sei->bu->tlv_data;
-        size_t tlv_size = sei->bu->tlv_size;
-        SV_THROW(decode_sei_data(self, tlv_data, tlv_size));
-        sei->has_been_decoded = true;
-        memcpy(verify_data->hash, sei->hash, hash_size);
-      }
-      detect_lost_sei(self);
-      SV_THROW(prepare_for_link_and_gop_hash_verification(self, sei));
+    (*sei)->in_validation = true;
+    if (!(*sei)->has_been_decoded) {
+      // Decode the SEI and set signature->hash
+      self->latest_validation->public_key_has_changed = false;
+      const uint8_t *tlv_data = (*sei)->bu->tlv_data;
+      size_t tlv_size = (*sei)->bu->tlv_size;
+      SV_THROW(decode_sei_data(self, tlv_data, tlv_size));
+      (*sei)->has_been_decoded = true;
+      memcpy(verify_data->hash, (*sei)->hash, hash_size);
     }
+    detect_lost_sei(self);
+    SV_THROW(prepare_for_link_and_gop_hash_verification(self, *sei));
 
     SV_THROW_IF_WITH_MSG(validation_flags->signing_present && !self->has_public_key,
         SV_NOT_SUPPORTED, "No public key present");
@@ -997,12 +998,10 @@ prepare_for_validation(signed_video_t *self)
 #endif
 
     // For SEIs, transfer the result of the signature verification.
-    if (sei) {
-      if (sei->bu->is_signed) {
-        self->gop_info->verified_signature_hash = sei->verified_signature;
-      } else {
-        self->gop_info->verified_signature_hash = 1;
-      }
+    if ((*sei)->bu->is_signed) {
+      self->gop_info->verified_signature_hash = (*sei)->verified_signature;
+    } else {
+      self->gop_info->verified_signature_hash = 1;
     }
 
   SV_CATCH()
@@ -1216,6 +1215,7 @@ maybe_validate_gop(signed_video_t *self, bu_info_t *bu)
     // Keep validating as long as there are pending GOPs.
     bool stop_validating = false;
     while (has_pending_partial_gop(self) && !stop_validating) {
+      bu_list_item_t *sei = NULL;
       // Initialize latest validation.
       if (!self->validation_flags.has_auth_result || validation_flags->is_first_validation) {
         latest->authenticity = SV_AUTH_RESULT_SIGNATURE_PRESENT;
@@ -1227,7 +1227,7 @@ maybe_validate_gop(signed_video_t *self, bu_info_t *bu)
         update_sei_in_validation(self, true, NULL, NULL);
       }
 
-      SV_THROW(prepare_for_validation(self));
+      SV_THROW(prepare_for_validation(self, &sei));
       update_link_hash_for_auth(self);
 
       if (!validation_flags->signing_present) {
@@ -1236,7 +1236,7 @@ maybe_validate_gop(signed_video_t *self, bu_info_t *bu)
         // to avoid a dead lock.
         stop_validating = true;
       } else {
-        validate_authenticity(self);
+        validate_authenticity(self, sei);
       }
 
       if (validation_flags->is_first_validation && (latest->authenticity != SV_AUTH_RESULT_OK)) {