Merge 117080 - Fix null deref when walking cert chain.

chrome/browser/safe_browsing/signature_util_win.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 "chrome/browser/safe_browsing/signature_util.h"
 
 #include <windows.h>
 #include <softpub.h>
 #include <wintrust.h>
 
@@ skipping 46 matching lines @@
 
   CRYPT_PROVIDER_DATA* prov_data = WTHelperProvDataFromStateData(
       wintrust_data.hWVTStateData);
   if (prov_data) {
     if (prov_data->csSigners > 0) {
       signature_info->set_trusted(result == ERROR_SUCCESS);
     }
     for (DWORD i = 0; i < prov_data->csSigners; ++i) {
       const CERT_CHAIN_CONTEXT* cert_chain_context =
           prov_data->pasSigners[i].pChainContext;
+      if (!cert_chain_context)
+        break;
       for (DWORD j = 0; j < cert_chain_context->cChain; ++j) {
         CERT_SIMPLE_CHAIN* simple_chain = cert_chain_context->rgpChain[j];
         ClientDownloadRequest_CertificateChain* chain =
             signature_info->add_certificate_chain();
+        if (!simple_chain)
+          break;
         for (DWORD k = 0; k < simple_chain->cElement; ++k) {
           CERT_CHAIN_ELEMENT* element = simple_chain->rgpElement[k];
           chain->add_element()->set_certificate(
               element->pCertContext->pbCertEncoded,
               element->pCertContext->cbCertEncoded);
         }
       }
     }
 
     // Free the provider data.
     wintrust_data.dwStateAction = WTD_STATEACTION_CLOSE;
     WinVerifyTrust(static_cast<HWND>(INVALID_HANDLE_VALUE),
                    &policy_guid, &wintrust_data);
   }
 }
 
 }  // namespace safe_browsing