Do not allow the server certificate to change in a renegotiation.

net/socket/ssl_client_socket_nss.cc

 // 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.
 
 // This file includes code SSLClientSocketNSS::DoVerifyCertComplete() derived
 // from AuthCertificateCallback() in
 // mozilla/security/manager/ssl/src/nsNSSCallbacks.cpp.
 
 /* ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
@@ skipping 1269 matching lines @@
     if (rv != SECSuccess || !negotiated_extension) {
       rv = SSL_HandshakeNegotiatedExtension(socket,
                                             ssl_next_proto_nego_xtn,
                                             &negotiated_extension);
     }
     if (rv != SECSuccess || !negotiated_extension) {
       // If the server doesn't support NPN or ALPN, then we don't do False
       // Start with it.
       SSL_OptionSet(socket, SSL_ENABLE_FALSE_START, PR_FALSE);
     }
+  } else {
+    // Disallow the server certificate to change in a renegotiation.

[wtc, 2013/10/14 23:11:11]

This can also be enforced by NSS.

+    CERTCertificate* old_cert = core->nss_handshake_state_.server_cert_chain[0];
+    CERTCertificate* new_cert = SSL_PeerCertificate(socket);
+    if (new_cert->derCert.len != old_cert->derCert.len ||
+        memcmp(new_cert->derCert.data, old_cert->derCert.data,
+               new_cert->derCert.len) != 0) {
+      PORT_SetError(SSL_ERROR_BAD_CERTIFICATE);
+      return SECFailure;
+    }
   }
 
   // Tell NSS to not verify the certificate.
   return SECSuccess;
 }
 
 #if defined(NSS_PLATFORM_CLIENT_AUTH)
 // static
 SECStatus SSLClientSocketNSS::Core::PlatformClientAuthHandler(
     void* arg,
@@ skipping 2191 matching lines @@
   EnsureThreadIdAssigned();
   base::AutoLock auto_lock(lock_);
   return valid_thread_id_ == base::PlatformThread::CurrentId();
 }
 
 ServerBoundCertService* SSLClientSocketNSS::GetServerBoundCertService() const {
   return server_bound_cert_service_;
 }
 
 }  // namespace net