Check TBSCertificate.algorithm and Certificate.signatureAlgorithm for

net/cert/internal/signature_algorithm.cc

 // Copyright 2015 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/internal/signature_algorithm.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/memory/ptr_util.h"
@@ skipping 495 matching lines @@
   // There must not be any unconsumed data left. (RFC 5912 does not explicitly
   // include an extensibility point for RSASSA-PSS-params)
   if (params_parser.HasMore())
     return nullptr;
 
   return SignatureAlgorithm::CreateRsaPss(hash, mgf1_hash, salt_length);
 }
 
 }  // namespace
 
-WARN_UNUSED_RESULT bool ParseHashAlgorithm(const der::Input input,
+WARN_UNUSED_RESULT bool ParseHashAlgorithm(const der::Input& input,
                                            DigestAlgorithm* out) {
   der::Input oid;
   der::Input params;
   if (!ParseAlgorithmIdentifier(input, &oid, &params))
     return false;
 
   DigestAlgorithm hash;
 
   if (oid == der::Input(kOidSha1)) {
     hash = DigestAlgorithm::Sha1;
@@ skipping 104 matching lines @@
       SignatureAlgorithmId::RsaPss, digest,
       base::MakeUnique<RsaPssParameters>(mgf1_hash, salt_length)));
 }
 
 const RsaPssParameters* SignatureAlgorithm::ParamsForRsaPss() const {
   if (algorithm_ == SignatureAlgorithmId::RsaPss)
     return static_cast<RsaPssParameters*>(params_.get());
   return nullptr;
 }
 
+bool SignatureAlgorithm::IsEquivalent(const der::Input& alg1_tlv,
+                                      const der::Input& alg2_tlv) {
+  if (alg1_tlv == alg2_tlv)
+    return true;
+
+  auto alg1 = Create(alg1_tlv, nullptr);
+  auto alg2 = Create(alg2_tlv, nullptr);
+
+  if (!alg1 || !alg2 || (alg1->algorithm() != alg2->algorithm()) ||
+      (alg1->digest() != alg2->digest())) {
+    return false;
+  }
+
+  // For simplicity don't check the parsed parameters (only applicable
+  // for RSA-PSS). This does mean RSA-PSS AlgorithmIdentifiers need to
+  // use identical encodings to be considered equivalent by this
+  // function.
+  return !alg1->has_params() && !alg2->has_params();
+}
+
 SignatureAlgorithm::SignatureAlgorithm(
     SignatureAlgorithmId algorithm,
     DigestAlgorithm digest,
     std::unique_ptr<SignatureAlgorithmParameters> params)
     : algorithm_(algorithm), digest_(digest), params_(std::move(params)) {}
 
 }  // namespace net