Avoid a crash in X.509 NSS certificate verification glue

net/base/x509_certificate_nss.cc

 // Copyright (c) 2006-2008 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/x509_certificate.h"
 
 // Work around https://bugzilla.mozilla.org/show_bug.cgi?id=455424
 // until NSS 3.12.2 comes out and we update to it.
 #define Lock FOO_NSS_Lock
 #include <cert.h>
@@ skipping 154 matching lines @@
   }
 }
 
 // Saves some information about the certificate chain cert_list in
 // *verify_result.  The caller MUST initialize *verify_result before calling
 // this function.
 // Note that cert_list[0] is the end entity certificate and cert_list doesn't
 // contain the root CA certificate.
 void GetCertChainInfo(CERTCertList* cert_list,
                       CertVerifyResult* verify_result) {
+  if (!cert_list) {
+    return;
+  }
+
   int i = 0;
   for (CERTCertListNode* node = CERT_LIST_HEAD(cert_list);
        !CERT_LIST_END(node, cert_list);
        node = CERT_LIST_NEXT(node), i++) {
     SECAlgorithmID& signature = node->cert->signature;
     SECOidTag oid_tag = SECOID_FindOIDTag(&signature.algorithm);
     switch (oid_tag) {
       case SEC_OID_PKCS1_MD5_WITH_RSA_ENCRYPTION:
         verify_result->has_md5 = true;
         if (i != 0)
@@ skipping 419 matching lines @@
   DCHECK(0 != cert->derCert.len);
 
   SECStatus rv = HASH_HashBuf(HASH_AlgSHA1, sha1.data,
                               cert->derCert.data, cert->derCert.len);
   DCHECK(rv == SECSuccess);
 
   return sha1;
 }
 
 }  // namespace net