The Tor Browser / file revision

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 #include <stdio.h>

 #include <stdlib.h>

 #include <windows.h>

 #include <softpub.h>

 #include <wintrust.h>

 #include "certificatecheck.h"

 #include "servicebase.h"

 #pragma comment(lib, "wintrust.lib")

 #pragma comment(lib, "crypt32.lib")

 static const int ENCODING = X509_ASN_ENCODING | PKCS_7_ASN_ENCODING;

 /**

  * Checks to see if a file stored at filePath matches the specified info.

  *

  * @param  filePath    The PE file path to check

  * @param  infoToMatch The acceptable information to match

  * @return ERROR_SUCCESS if successful, ERROR_NOT_FOUND if the info 

  *         does not match, or the last error otherwise.

  */

 DWORD

 CheckCertificateForPEFile(LPCWSTR filePath, 

                           CertificateCheckInfo &infoToMatch)

 {

   HCERTSTORE certStore = nullptr;

   HCRYPTMSG cryptMsg = nullptr; 

   PCCERT_CONTEXT certContext = nullptr;

   PCMSG_SIGNER_INFO signerInfo = nullptr;

   DWORD lastError = ERROR_SUCCESS;

   // Get the HCERTSTORE and HCRYPTMSG from the signed file.

   DWORD encoding, contentType, formatType;

   BOOL result = CryptQueryObject(CERT_QUERY_OBJECT_FILE,

                                   filePath, 

                                   CERT_QUERY_CONTENT_FLAG_PKCS7_SIGNED_EMBED,

                                   CERT_QUERY_CONTENT_FLAG_ALL, 

                                   0, &encoding, &contentType,

                                   &formatType, &certStore, &cryptMsg, nullptr);

   if (!result) {

     lastError = GetLastError();

     LOG_WARN(("CryptQueryObject failed.  (%d)", lastError));

     goto cleanup;

   }

   // Pass in nullptr to get the needed signer information size.

   DWORD signerInfoSize;

   result = CryptMsgGetParam(cryptMsg, CMSG_SIGNER_INFO_PARAM, 0, 

                             nullptr, &signerInfoSize);

   if (!result) {

     lastError = GetLastError();

     LOG_WARN(("CryptMsgGetParam failed.  (%d)", lastError));

     goto cleanup;

   }

   // Allocate the needed size for the signer information.

   signerInfo = (PCMSG_SIGNER_INFO)LocalAlloc(LPTR, signerInfoSize);

   if (!signerInfo) {

     lastError = GetLastError();

     LOG_WARN(("Unable to allocate memory for Signer Info.  (%d)", lastError));

     goto cleanup;

   }

   // Get the signer information (PCMSG_SIGNER_INFO).

   // In particular we want the issuer and serial number.

   result = CryptMsgGetParam(cryptMsg, CMSG_SIGNER_INFO_PARAM, 0, 

                             (PVOID)signerInfo, &signerInfoSize);

   if (!result) {

     lastError = GetLastError();

     LOG_WARN(("CryptMsgGetParam failed.  (%d)", lastError));

     goto cleanup;

   }

   // Search for the signer certificate in the certificate store.

   CERT_INFO certInfo;     

   certInfo.Issuer = signerInfo->Issuer;

   certInfo.SerialNumber = signerInfo->SerialNumber;

   certContext = CertFindCertificateInStore(certStore, ENCODING, 0, 

                                            CERT_FIND_SUBJECT_CERT,

                                            (PVOID)&certInfo, nullptr);

   if (!certContext) {

     lastError = GetLastError();

     LOG_WARN(("CertFindCertificateInStore failed.  (%d)", lastError));

     goto cleanup;

   }

   if (!DoCertificateAttributesMatch(certContext, infoToMatch)) {

     lastError = ERROR_NOT_FOUND;

     LOG_WARN(("Certificate did not match issuer or name.  (%d)", lastError));

     goto cleanup;

   }

 cleanup:

   if (signerInfo) {

     LocalFree(signerInfo);

   }

   if (certContext) {

     CertFreeCertificateContext(certContext);

   }

   if (certStore) { 

     CertCloseStore(certStore, 0);

   }

   if (cryptMsg) { 

     CryptMsgClose(cryptMsg);

   }

   return lastError;

 }

 /**

  * Checks to see if a file stored at filePath matches the specified info.

  *

  * @param  certContext  The certificate context of the file

  * @param  infoToMatch  The acceptable information to match

  * @return FALSE if the info does not match or if any error occurs in the check

  */

 BOOL 

 DoCertificateAttributesMatch(PCCERT_CONTEXT certContext, 

                              CertificateCheckInfo &infoToMatch)

 {

   DWORD dwData;

   LPTSTR szName = nullptr;

   if (infoToMatch.issuer) {

     // Pass in nullptr to get the needed size of the issuer buffer.

     dwData = CertGetNameString(certContext, 

                                CERT_NAME_SIMPLE_DISPLAY_TYPE,

                                CERT_NAME_ISSUER_FLAG, nullptr,

                                nullptr, 0);

     if (!dwData) {

       LOG_WARN(("CertGetNameString failed.  (%d)", GetLastError()));

       return FALSE;

     }

     // Allocate memory for Issuer name buffer.

     LPTSTR szName = (LPTSTR)LocalAlloc(LPTR, dwData * sizeof(WCHAR));

     if (!szName) {

       LOG_WARN(("Unable to allocate memory for issuer name.  (%d)",

                 GetLastError()));

       return FALSE;

     }

     // Get Issuer name.

     if (!CertGetNameString(certContext, CERT_NAME_SIMPLE_DISPLAY_TYPE,

                            CERT_NAME_ISSUER_FLAG, nullptr, szName, dwData)) {

       LOG_WARN(("CertGetNameString failed.  (%d)", GetLastError()));

       LocalFree(szName);

       return FALSE;

     }

     // If the issuer does not match, return a failure.

     if (!infoToMatch.issuer ||

         wcscmp(szName, infoToMatch.issuer)) {

       LocalFree(szName);

       return FALSE;

     }

     LocalFree(szName);

     szName = nullptr;

   }

   if (infoToMatch.name) {

     // Pass in nullptr to get the needed size of the name buffer.

     dwData = CertGetNameString(certContext, CERT_NAME_SIMPLE_DISPLAY_TYPE,

                                0, nullptr, nullptr, 0);

     if (!dwData) {

       LOG_WARN(("CertGetNameString failed.  (%d)", GetLastError()));

       return FALSE;

     }

     // Allocate memory for the name buffer.

     szName = (LPTSTR)LocalAlloc(LPTR, dwData * sizeof(WCHAR));

     if (!szName) {

       LOG_WARN(("Unable to allocate memory for subject name.  (%d)",

                 GetLastError()));

       return FALSE;

     }

     // Obtain the name.

     if (!(CertGetNameString(certContext, CERT_NAME_SIMPLE_DISPLAY_TYPE, 0,

                             nullptr, szName, dwData))) {

       LOG_WARN(("CertGetNameString failed.  (%d)", GetLastError()));

       LocalFree(szName);

       return FALSE;

     }

     // If the issuer does not match, return a failure.

     if (!infoToMatch.name || 

         wcscmp(szName, infoToMatch.name)) {

       LocalFree(szName);

       return FALSE;

     }

     // We have a match!

     LocalFree(szName);

   }

   // If there were any errors we would have aborted by now.

   return TRUE;

 }

 /**

  * Duplicates the specified string

  *

  * @param  inputString The string to duplicate

  * @return The duplicated string which should be freed by the caller.

  */

 LPWSTR 

 AllocateAndCopyWideString(LPCWSTR inputString)

 {

   LPWSTR outputString = 

     (LPWSTR)LocalAlloc(LPTR, (wcslen(inputString) + 1) * sizeof(WCHAR));

   if (outputString) {

     lstrcpyW(outputString, inputString);

   }

   return outputString;

 }

 /**

  * Verifies the trust of the specified file path.

  *

  * @param  filePath  The file path to check.

  * @return ERROR_SUCCESS if successful, or the last error code otherwise.

  */

 DWORD

 VerifyCertificateTrustForFile(LPCWSTR filePath)

 {

   // Setup the file to check.

   WINTRUST_FILE_INFO fileToCheck;

   ZeroMemory(&fileToCheck, sizeof(fileToCheck));

   fileToCheck.cbStruct = sizeof(WINTRUST_FILE_INFO);

   fileToCheck.pcwszFilePath = filePath;

   // Setup what to check, we want to check it is signed and trusted.

   WINTRUST_DATA trustData;

   ZeroMemory(&trustData, sizeof(trustData));

   trustData.cbStruct = sizeof(trustData);

   trustData.pPolicyCallbackData = nullptr;

   trustData.pSIPClientData = nullptr;

   trustData.dwUIChoice = WTD_UI_NONE;

   trustData.fdwRevocationChecks = WTD_REVOKE_NONE; 

   trustData.dwUnionChoice = WTD_CHOICE_FILE;

   trustData.dwStateAction = 0;

   trustData.hWVTStateData = nullptr;

   trustData.pwszURLReference = nullptr;

   // no UI

   trustData.dwUIContext = 0;

   trustData.pFile = &fileToCheck;

   GUID policyGUID = WINTRUST_ACTION_GENERIC_VERIFY_V2;

   // Check if the file is signed by something that is trusted.

   LONG ret = WinVerifyTrust(nullptr, &policyGUID, &trustData);

   if (ERROR_SUCCESS == ret) {

     // The hash that represents the subject is trusted and there were no

     // verification errors.  No publisher nor time stamp chain errors.

     LOG(("The file \"%ls\" is signed and the signature was verified.",

          filePath));

       return ERROR_SUCCESS;

   }

   DWORD lastError = GetLastError();

   LOG_WARN(("There was an error validating trust of the certificate for file"

             " \"%ls\". Returned: %d.  (%d)", filePath, ret, lastError));

   return ret;

 }