certificatecheck.cxx

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/* 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.hxx"
#include "servicebase.hxx"
 
#pragma comment(lib, "wintrust.lib")
#pragma comment(lib, "crypt32.lib")
 
static const int ENCODING = X509_ASN_ENCODING | PKCS_7_ASN_ENCODING;
 
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;
}
 
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;
}
 
LPWSTR
AllocateAndCopyWideString(LPCWSTR inputString)
{
    LPWSTR outputString =
        (LPWSTR)LocalAlloc(LPTR, (wcslen(inputString) + 1) * sizeof(WCHAR));
    if (outputString)
    {
        lstrcpyW(outputString, inputString);
    }
    return outputString;
}
 
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;
}