Extract Certificate Transparency SCTs from stapled OCSP responses

net/cert/ct_objects_extractor.h

 // 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.
 
 #ifndef NET_CERT_CT_OBJECTS_EXTRACTOR_H_
 #define NET_CERT_CT_OBJECTS_EXTRACTOR_H_
 
 #include <string>
 
 #include "net/base/net_export.h"
@@ skipping 27 matching lines @@
 
 // Obtains an X509Chain log entry for |leaf|, an X.509v3 certificate that
 // is not expected to contain an X.509v3 extension with the OID
 // 1.3.6.1.4.1.11129.2.4.2 (meaning a certificate without an embedded SCT).
 // On success, fills |result| with the data for an X509Chain log entry and
 // returns true.
 // The filled |*result| should be verified using ct::CTLogVerifier::Verify
 NET_EXPORT_PRIVATE bool GetX509LogEntry(X509Certificate::OSCertHandle leaf,
                                         LogEntry* result);
 
+// Extracts a SignedCertificateTimestampList that has been embedded within
+// an OCSP response as an extension with the OID 1.3.6.1.4.1.11129.2.4.5.
+// If the extension is present, and matches the serial number of the leaf
+// certificate, returns true, updating |*sct_list| to contain
+// the encoded list, minus the DER encoding necessary for the extension.
+// |*sct_list| can then be further decoded with ct::DecodeSCTList.
+//
+// TODO(ekasper): change this to match by the entire CertID in an OCSP response.
+// We currently do response matching by serial number only, so if the response
+// contains statuses for different certificates with the same serial number,
+// this method does not work. However, repeating serial numbers within the same
+// OCSP response are unlikely to begin with (different CAs would have to be
+// using the same serial number AND delegating to the same OCSP responder),
+// and since CT further only uses stapled OCSP responses which are known to
+// pertain to the server (leaf) certificate, this is a very low concern for us.
+NET_EXPORT_PRIVATE bool ExtractSCTListFromOCSPResponse(
+    X509Certificate::OSCertHandle leaf,

[wtc, 2013/12/03 21:04:25]

Nit: If CT can also be used for CA certificates, I suggest renaming this
parameter |cert| to be more general.

If you rename it, you should update the comment "the serial number of the leaf
certificate" on lines 50-51 accordingly.

[ekasper, 2013/12/04 19:25:15]

I've changed it to take a serial number directly.

+    const std::string& ocsp_response,
+    std::string* sct_list);
+
 }  // namespace ct
 
 }  // namespace net
 
 #endif  // NET_CERT_CT_OBJECTS_EXTRACTOR_H_