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devmauv's questions

Martin Hope
devmauv
Asked: 2025-04-26 05:09:10 +0800 CST
  • 6

Estou gerando um p7s com CryptSignMessage e etoken (safenet), mas após inseri-lo no PDF, o Adobe indica que a assinatura não pode ser validada porque o documento foi modificado ou corrompido.

Esta é minha função C:

int GeneratePKCS7Signature(const BYTE * pbData, DWORD cbData,
  const CERTIFICATES_INFO * certInfo, BYTE ** ppbPkcs7, DWORD * pcbPkcs7) {
  if (!pbData || cbData == 0 || !certInfo || !certInfo -> signerCert || !ppbPkcs7 || !pcbPkcs7) {
    printf("Invalid parameters.\n");
    return 1;
  }
  printf("Start GeneratePKCS7Signature\n");
  // Verify that the signing certificate has its private key associated (using SafeNet etoken)
  NCRYPT_KEY_HANDLE hKey = 0;
  BOOL freeKey = FALSE;
  if (!CryptAcquireCertificatePrivateKey(certInfo -> signerCert,
      CRYPT_ACQUIRE_ALLOW_NCRYPT_KEY_FLAG,
      NULL,
      (HCRYPTPROV_OR_NCRYPT_KEY_HANDLE * ) & hKey,
      NULL, &
      freeKey)) {
    printf("Error searching for the private key of the signing certificate: %lu\n", GetLastError());
    return 1;
  }

  if (freeKey && hKey)
    NCryptFreeObject(hKey);

  // Build the array of certificates to be included in thePKCS#7:
  // The signing certificate is included, then the intermediate certificates and finally the root certificates
  size_t totalCertCount = 1 + certInfo -> numIntermediates + certInfo -> numRoots;
  PCCERT_CONTEXT * rgpCerts = (PCCERT_CONTEXT * ) malloc(totalCertCount * sizeof(PCCERT_CONTEXT));
  if (!rgpCerts) {
    printf("Error allocating memory for the certificate array.\n");
    return 1;
  }
  size_t idx = 0;
  rgpCerts[idx++] = certInfo -> signerCert;
  for (size_t i = 0; i < certInfo -> numIntermediates; i++) {
    rgpCerts[idx++] = certInfo -> intermediates[i];
  }
  for (size_t i = 0; i < certInfo -> numRoots; i++) {
    rgpCerts[idx++] = certInfo -> roots[i];
  }

  // Configure the structure CRYPT_SIGN_MESSAGE_PARA.

  CRYPT_SIGN_MESSAGE_PARA signPara;
  memset( & signPara, 0, sizeof(signPara));
  signPara.cbSize = sizeof(CRYPT_SIGN_MESSAGE_PARA);
  signPara.dwMsgEncodingType = PKCS_7_ASN_ENCODING | X509_ASN_ENCODING;
  signPara.pSigningCert = certInfo -> signerCert;
  signPara.HashAlgorithm.pszObjId = OID_RSA_SHA256; // SHA256
  signPara.cMsgCert = (DWORD) totalCertCount;
  signPara.rgpMsgCert = rgpCerts;
  signPara.cAuthAttr = 0;
  signPara.dwFlags = 0;
  signPara.dwInnerContentType = 0;

  // Prepare the parameters for the function CryptSignMessage.
  const BYTE * rgpbToBeSigned[1] = {
    pbData
  };
  DWORD rgcbToBeSigned[1] = {
    cbData
  };

  // First call to get the required size of the PKCS#7.
  DWORD cbPkcs7 = 0;
  if (!CryptSignMessage( & signPara,
      TRUE, // Sign detached
      1,
      rgpbToBeSigned,
      rgcbToBeSigned,
      NULL, &
      cbPkcs7)) {
    printf("Error calculating the size of the PKCS#7: 0x%x\n", GetLastError());
    free(rgpCerts);
    return 1;
  }

  BYTE * pbPkcs7 = (BYTE * ) HeapAlloc(GetProcessHeap(), 0, cbPkcs7);
  if (!pbPkcs7) {
    printf("Error allocating memory for the PKCS#7.\n");
    free(rgpCerts);
    return 1;
  }

  // Second call to generate the PKCS#7.
  if (!CryptSignMessage( & signPara,
      TRUE, // Sign detached
      1,
      rgpbToBeSigned,
      rgcbToBeSigned,
      pbPkcs7, &
      cbPkcs7)) {
    printf("Error generating the PKCS#7: 0x%x\n", GetLastError());
    HeapFree(GetProcessHeap(), 0, pbPkcs7);
    free(rgpCerts);
    return 1;
  }

  * ppbPkcs7 = pbPkcs7;
  * pcbPkcs7 = cbPkcs7;

  free(rgpCerts);
  return 0;
}

o p7s gerado é: firma.p7s teste pdf assinado: pdf

Testei vários PDFs diferentes. Também verifiquei os hashes SHA256 antes e depois da assinatura. Analisei a estrutura do PDF com diferentes ferramentas, como o QPDF. Portanto, acredito que o problema esteja no PKCS7, em algum atributo ou na própria assinatura que está impedindo a Adobe de validá-la. Também verifiquei com o decodificador ANS.1 e, embora tenha corrigido algumas coisas, o erro continua o mesmo.

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