/* Copyright (C) 2014 by Bundesamt für Sicherheit in der Informationstechnik
 * Software engineering by Intevation GmbH
 *
 * This file is Free Software under the GNU GPL (v>=2)
 * and comes with ABSOLUTELY NO WARRANTY!
 * See LICENSE.txt for details.
 */

#include "binverify.h"

#include "strhelp.h"
#include "logging.h"

#ifdef RELEASE_BUILD
#include "pubkey-release.h"
#else
#include "pubkey-test.h"
#endif

bin_verify_result
verify_binary(const char *filename, size_t name_len) {
#ifdef WIN32
  return verify_binary_win(filename, name_len);
#else
  /* TODO */
  if (filename && name_len)
    return VerifyValid;
  return VerifyUnknownError;
#endif
}

#ifdef WIN32

#include <polarssl/x509_crt.h>

#include <windows.h>
#include <wincrypt.h>
#include <wintrust.h>
#include <stdio.h>


/** @brief Check if the certificate @a pCCertContext is pinned
  *
  * Compares the certificate's binary data (public key and attributes)
  * with each other to validate that the certificate pCCertContext has
  * exactly the same data as the builtin public certificate.
  *
  * @param[in] pCCertContext pointer to the certificate to check
  *
  * @returns true if the certificate matches, false otherwise.
  */
static bool
check_certificate (PCCERT_CONTEXT pCCertContext)
{
  x509_crt codesign_cert;
  int ret = 0;
  DWORD dwI = 0;
  bool retval = false;

  if (pCCertContext == NULL)
    {
      ERRORPRINTF ("Invalid call to check_certificate");
      return false;
    }

  x509_crt_init(&codesign_cert);

  /* Parse the pinned certificate */
  ret = x509_crt_parse(&codesign_cert,
                       public_key_codesign_pem,
                       public_key_codesign_pem_size);
  if (ret != 0)
    {
      ERRORPRINTF ("x509_crt_parse failed with -0x%04x\n\n", -ret);
      goto done;
    }

  if (codesign_cert.raw.len != pCCertContext->cbCertEncoded ||
      codesign_cert.raw.len <= 0)
    {
      ERRORPRINTF ("Certificate size mismatch");
      goto done;
    }

  /* Check that the certificate is exactly the same as the pinned one */
  for (dwI = 0; dwI < pCCertContext->cbCertEncoded; dwI++)
    {
      if (pCCertContext->pbCertEncoded[dwI] != codesign_cert.raw.p[dwI])
        {
          ERRORPRINTF ("Certificate content mismatch");
          goto done;
        }
    }

  retval = true;

done:
  x509_crt_free(&codesign_cert);
  return retval;
}

bin_verify_result
verify_binary_win(const char *filename, size_t name_len) {
  bin_verify_result retval = VerifyUnknownError;
  WCHAR *filenameW = NULL;
  BOOL result = FALSE;
  DWORD dwEncoding = 0,
        dwContentType = 0,
        dwFormatType = 0,
        dwSignerInfoSize = 0;
  HCERTSTORE hStore = NULL;
  HCRYPTMSG hMsg = NULL;
  PCERT_INFO pSignerCert = NULL;
  PCCERT_CONTEXT pSignerCertContext = NULL;

  if (!filename || name_len > MAX_PATH || strlen(filename) != name_len)
    {
      ERRORPRINTF ("Invalid parameters\n");
      return VerifyUnknownError;
    }

  filenameW = utf8_to_wchar(filename, name_len);

  result = CryptQueryObject (CERT_QUERY_OBJECT_FILE,
                             filenameW,
                             CERT_QUERY_CONTENT_FLAG_PKCS7_SIGNED_EMBED,
                             CERT_QUERY_FORMAT_FLAG_BINARY,
                             0,
                             &dwEncoding,
                             &dwContentType,
                             &dwFormatType,
                             &hStore,
                             &hMsg,
                             NULL);

  if (!result || !hMsg)
    {
      PRINTLASTERROR ("Failed to query crypto object");
      retval = VerifyReadFailed;
      goto done;
    }

  /* Get the cert info so that we can look up the signer in the store later */
  if (CryptMsgGetParam(hMsg,
                       CMSG_SIGNER_CERT_INFO_PARAM,
                       0,
                       NULL,
                       &dwSignerInfoSize) && dwSignerInfoSize > 0)
    {
      pSignerCert = xmalloc (dwSignerInfoSize);
    }
  else
    {
      ERRORPRINTF ("Failed to get signer cert size.");
      retval = VerifyUnknownError;
      goto done;
    }

  if (!(CryptMsgGetParam(hMsg,
                         CMSG_SIGNER_CERT_INFO_PARAM,
                         0,
                         pSignerCert,
                         &dwSignerInfoSize)))
    {
      ERRORPRINTF ("Failed to get signer cert.");
      retval = VerifyUnknownError;
      goto done;
    }

  pSignerCertContext = CertGetSubjectCertificateFromStore(
          hStore,
          PKCS_7_ASN_ENCODING | X509_ASN_ENCODING,
          pSignerCert);

  if (!pSignerCertContext)
    {
      ERRORPRINTF ("Failed to find signer cert in store.");
      retval = VerifyUnknownError;
      goto done;
    }

  /* Verify that the signature is actually valid */
  if(!CryptMsgControl(hMsg,
                      0,
                      CMSG_CTRL_VERIFY_SIGNATURE,
                      pSignerCertContext->pCertInfo))
    {
      ERRORPRINTF ("The signature is invalid. \n");
      retval = VerifyInvalidSignature;
      syslog_error_printf ("Software update embedded signature is invalid.");
      goto done;
    }

  if(check_certificate(pSignerCertContext))
    {
      DEBUGPRINTF ("Valid signature with pinned certificate.");
      retval = VerifyValid;
      goto done;
    }
  else
    {
      ERRORPRINTF ("Certificate mismatch. \n");
      retval = VerifyInvalidSignature;
      syslog_error_printf ("Software update embedded signature "
                           "created with wrong certificate.");
      goto done;
    }

done:
  xfree(filenameW);
  xfree(pSignerCert);

  if(pSignerCertContext)
    {
      CertFreeCertificateContext(pSignerCertContext);
    }
  if (hStore)
    {
      CertCloseStore(hStore, 0);
    }
  if (hMsg)
    {
      CryptMsgClose(hMsg);
    }
  return retval;
}
#endif /* WIN32 */