Certificate Transparency: Parse Signed Tree Heads and validate them

net/cert/ct_log_verifier.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/cert/ct_log_verifier.h"
 
 #include "base/logging.h"
 #include "net/cert/ct_serialization.h"
+#include "net/cert/signed_tree_head.h"
 
 namespace net {
 
 // static
 scoped_ptr<CTLogVerifier> CTLogVerifier::Create(
     const base::StringPiece& public_key,
     const base::StringPiece& description) {
   scoped_ptr<CTLogVerifier> result(new CTLogVerifier());
   if (!result->Init(public_key, description))
     result.reset();
   return result.Pass();
 }
 
 bool CTLogVerifier::Verify(const ct::LogEntry& entry,
                            const ct::SignedCertificateTimestamp& sct) {
   if (sct.log_id != key_id()) {
     DVLOG(1) << "SCT is not signed by this log.";
     return false;
   }
 
-  if (sct.signature.hash_algorithm != hash_algorithm_) {
-    DVLOG(1) << "Mismatched hash algorithm. Expected " << hash_algorithm_
-             << ", got " << sct.signature.hash_algorithm << ".";
+  if (!SignatureParametersMatch(sct.signature))
     return false;
-  }
-
-  if (sct.signature.signature_algorithm != signature_algorithm_) {
-    DVLOG(1) << "Mismatched sig algorithm. Expected " << signature_algorithm_
-             << ", got " << sct.signature.signature_algorithm << ".";
-    return false;
-  }
 
   std::string serialized_log_entry;
   if (!ct::EncodeLogEntry(entry, &serialized_log_entry)) {
     DVLOG(1) << "Unable to serialize entry.";
     return false;
   }
   std::string serialized_data;
   if (!ct::EncodeV1SCTSignedData(sct.timestamp, serialized_log_entry,
                                  sct.extensions, &serialized_data)) {
     DVLOG(1) << "Unable to create SCT to verify.";
     return false;
   }
 
   return VerifySignature(serialized_data, sct.signature.signature_data);
 }
 
+bool CTLogVerifier::SetSignedTreeHead(
+    scoped_ptr<ct::SignedTreeHead> signed_tree_head) {
+  if (!SignatureParametersMatch(signed_tree_head->signature))
+    return false;
+
+  std::string serialized_data;
+  ct::EncodeTreeHeadSignature(*signed_tree_head.get(), &serialized_data);
+  if (VerifySignature(serialized_data,
+                      signed_tree_head->signature.signature_data)) {
+    signed_tree_head_.reset(signed_tree_head.release());
+    return true;
+  }
+  return false;
+}
+
+bool CTLogVerifier::SignatureParametersMatch(
+    const ct::DigitallySigned& signature) {
+  if (!signature.SignatureParametersMatch(hash_algorithm_,
+                                          signature_algorithm_)) {
+    DVLOG(1) << "Mismatched hash or signature algorithm. Hash: "
+             << hash_algorithm_ << " vs " << signature.hash_algorithm
+             << " Signature: " << signature_algorithm_ << " vs "
+             << signature.signature_algorithm << ".";
+    return false;
+  }
+
+  return true;
+}
+
 }  // namespace net