Check TBSCertificate.algorithm and Certificate.signatureAlgorithm for

net/cert/asn1_util.h

 // Copyright (c) 2012 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.
 
 #ifndef NET_CERT_ASN1_UTIL_H_
 #define NET_CERT_ASN1_UTIL_H_
 
 #include <vector>
 
 #include "base/strings/string_piece.h"
@@ skipping 32 matching lines @@
     base::StringPiece cert,
     std::vector<base::StringPiece>* urls_out);
 
 // HasTLSFeatureExtension parses the DER encoded certificate in |cert|
 // and extracts the TLS feature extension
 // (https://tools.ietf.org/html/rfc7633) if present. Returns true if the
 // TLS feature extension was present, and false if the extension was not
 // present or if there was a parsing failure.
 NET_EXPORT_PRIVATE bool HasTLSFeatureExtension(base::StringPiece cert);
 
+// Extracts the two (SEQUENCE) tag-length-values for the signature
+// AlgorithmIdentifiers in a DER encoded certificate. Does not use strict
+// parsing or validate the resulting AlgorithmIdentifiers.
+//
+// On success returns true, and assigns |cert_signature_algorithm_sequence| and
+// |tbs_signature_algorithm_sequence| to point into |cert|:
+//
+// * |cert_signature_algorithm_sequence| points at the TLV for
+//   Certificate.signatureAlgorithm.
+//
+// * |tbs_signature_algorithm_sequence| points at the TLV for
+//   TBSCertificate.algorithm.
+NET_EXPORT_PRIVATE bool ExtractSignatureAlgorithmsFromDERCert(
+    base::StringPiece cert,
+    base::StringPiece* cert_signature_algorithm_sequence,
+    base::StringPiece* tbs_signature_algorithm_sequence);
+
 } // namespace asn1
 
 } // namespace net
 
 #endif // NET_CERT_ASN1_UTIL_H_