I'm attempting to verify a RS512 JWT using the WIN32 cryptography functions. I've got the public key, data to be verified, and signature data as in-memory arrays. I'm able to create the certificate context and import the public key, but so far I haven't been able to verify the signature. Regardless of what I attempt, I get a STATUS_INVALID_PARAMETER result.
I've seen several posts about having to reverse some or all of the data:
BCRYPT_ALG_HANDLE cryptAlg = nullptr;
if( BCRYPT_SUCCESS( BCryptOpenAlgorithmProvider( &cryptAlg, BCRYPT_RSA_ALGORITHM, nullptr, 0 ) ) )
{
auto signingKeyBuffer = signingKey.publicKeyBuffer();
PCCERT_CONTEXT cryptCert = CertCreateCertificateContext( X509_ASN_ENCODING, signingKeyBuffer.getBuffer(), signingKeyBuffer.getSize() );
if( cryptCert != nullptr )
{
BCRYPT_KEY_HANDLE cryptKey;
if( BCRYPT_SUCCESS( CryptImportPublicKeyInfoEx2( X509_ASN_ENCODING, &cryptCert->pCertInfo->SubjectPublicKeyInfo, 0, nullptr, &cryptKey ) ) )
{
BCRYPT_PKCS1_PADDING_INFO pkcs1Info;
pkcs1Info.pszAlgId = BCRYPT_SHA512_ALGORITHM;
auto dataBuffer = data;//.reversed();
auto signatureBuffer = signature;//.reversed();
auto status = BCryptVerifySignature( cryptKey, &pkcs1Info, dataBuffer.getBuffer(), dataBuffer.getSize(), signatureBuffer.getBuffer(), signatureBuffer.getSize(), BCRYPT_PAD_PKCS1 );
//status is always STATUS_INVALID_PARAMETER here...
BCryptDestroyKey( cryptKey );
}
CertFreeCertificateContext( cryptCert );
}
BCryptCloseAlgorithmProvider( cryptAlg, 0 );
}
I missed the part in the documentation that says the data needs to be hashed. After applying the same hash to the data (SHA512) I am able to verify the signature. Here is the working code minus error checking:
//Hash data here.
auto hashedData = data.hash( HashType::SHA512 );
auto signingKeyBuffer = signingKey.publicKeyBuffer();
PCCERT_CONTEXT cryptCert = CertCreateCertificateContext( X509_ASN_ENCODING, signingKeyBuffer.getBuffer(), signingKeyBuffer.getSize() );
if( cryptCert != nullptr )
{
BCRYPT_KEY_HANDLE cryptKey;
if( BCRYPT_SUCCESS( CryptImportPublicKeyInfoEx2( X509_ASN_ENCODING, &cryptCert->pCertInfo->SubjectPublicKeyInfo, 0, nullptr, &cryptKey ) ) )
{
BCRYPT_PKCS1_PADDING_INFO pkcs1Info;
pkcs1Info.pszAlgId = cNEHash::algorithmIdForHashType( cAlgorithmType::hashType( algorithm ) );
auto status = BCryptVerifySignature( cryptKey, &pkcs1Info, hashedData.getBuffer(), hashedData.getSize(), signature.getBuffer(), signature.getSize(), BCRYPT_PAD_PKCS1 );
if( BCRYPT_SUCCESS( status ) )
verified = true;
BCryptDestroyKey( cryptKey );
}
CertFreeCertificateContext( cryptCert );
}