Add a new ExtractSubjectPublicKeyFromSPKI method to asn1_utils.

net/base/asn1_util.cc

 // Copyright (c) 2011 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/base/asn1_util.h"
 
 namespace net {
 
 namespace asn1 {
 
@@ skipping 139 matching lines @@
 
 bool ExtractSPKIFromDERCert(base::StringPiece cert,
                             base::StringPiece* spki_out) {
   if (!SeekToSPKI(&cert))
     return false;
   if (!ParseElement(&cert, kSEQUENCE, spki_out, NULL))
     return false;
   return true;
 }
 
+bool ExtractSubjectPublicKeyFromSPKI(base::StringPiece spki,
+                                     base::StringPiece* spk_out) {
+  // From RFC 5280, Section 4.1
+  //   SubjectPublicKeyInfo  ::=  SEQUENCE  {
+  //     algorithm            AlgorithmIdentifier,
+  //     subjectPublicKey     BIT STRING  }
+  //
+  //   AlgorithmIdentifier  ::=  SEQUENCE  {
+  //     algorithm               OBJECT IDENTIFIER,
+  //     parameters              ANY DEFINED BY algorithm OPTIONAL  }
+
+  // Step into SubjectPublicKeyInfo sequence.
+  base::StringPiece spki_contents;
+  if (!asn1::GetElement(&spki, asn1::kSEQUENCE, &spki_contents))
+    return false;
+
+  // Step over algorithm field (a SEQUENCE).
+  base::StringPiece algorithm;
+  if (!asn1::GetElement(&spki_contents, asn1::kSEQUENCE, &algorithm))
+    return false;
+
+  // Extract the subjectPublicKey field.
+  if (!asn1::GetElement(&spki_contents, asn1::kBITSTRING, spk_out))
+    return false;
+  return true;
+}
+
+
 bool ExtractCRLURLsFromDERCert(base::StringPiece cert,
                                std::vector<base::StringPiece>* urls_out) {
   urls_out->clear();
   std::vector<base::StringPiece> tmp_urls_out;
 
   if (!SeekToSPKI(&cert))
     return false;
 
   // From RFC 5280, section 4.1
   // TBSCertificate  ::=  SEQUENCE  {
@@ skipping 124 matching lines @@
     }
   }
 
   urls_out->swap(tmp_urls_out);
   return true;
 }
 
 } // namespace asn1
 
 } // namespace net