public bool Verify(byte[] nis)
{
var digestAlgo = string.Empty;
switch (OIDDSMessageDigestHashAlgo)
{
case "2.16.840.1.101.3.4.2.1":
digestAlgo = "SHA256";
break;
case "2.16.840.1.101.3.4.2.3":
digestAlgo = "SHA512";
break;
default:
throw new Exception("hash algoritm not valid");
}
/*Get hashed data of
* - ID servizi
* - Seriale carta
* - Certificato utente
* - Chiave pubblica di internal authentication
* - Chiave pubblica di internal authentication per i servizi
* contained in SignedDataObject and calculate hash of hash*/
var digestRecalculation = SignedDataObject.DeepChild(1, 0).Data.ToMessageDigest(digestAlgo);
//Compare recalculation of hash with data contained in signer message digest object to verify equality
if (digestRecalculation.ToHexString() != SignerMessageDigest.Data.ToHexString())
{
return(false); // Digest SOD not correspond to data
}
//Get Document Signer public key from SignedCert data
var dsPubKey = DSCertificate.DeepChild(0, 6, 1, 0);
//Get modulus and exponent from Document Signer public key
var dsModPubKey = dsPubKey.Child(0, 0x02).Data; // modulus. 0x02 Verify that result is a INTEGER
var dsExpPubKey = dsPubKey.Child(1, 0x02).Data; // exp. 0x02 Verify that result is a INTEGER
//Verify SOD sign using DS public key and sign algoritm
using (var rsa = new RSAService(dsModPubKey, dsExpPubKey))
{
var isValidSod = false;
switch (OIDDSMessageDigestSignAlgo)
{
case "1.2.840.113549.1.1.5":
isValidSod = rsa.CheckSHA1withRSAEncryption(Signature.Data, SignatureAlgoritmIdentifier.MakeTag(0x31));
break;
case "1.2.840.113549.1.1.10":
isValidSod = rsa.CheckRSASSAPSS(Signature.Data, SignatureAlgoritmIdentifier.MakeTag(0x31), digestAlgo);
break;
default:
throw new Exception("Sign aloritm not supported");
}
if (!isValidSod)
{
throw new Exception("SOD sign wrong"); //SOD sign wrong
}
}
//Get issuer information from Document Signer certificate and compare it with data in IssuerName ASN1 tag
var issuer = DSCertificate.DeepChild(0).Child(3, 0x30); //0x30 Verify that result is a SEQUENCE
//Compare issuer information obtained from DS certificate with information stored directly in IssuerName tag
if (issuer.Data.ToHexString() != IssuerName.Data.ToHexString())
{
return(false); //Issuer name check failed
}
//Get serial number information from Document Signer certificate and compare it with data in SignerCertSerialNumber ASN1 tag
var serialNumber = DSCertificate.DeepChild(0).Child(1, 0x02); //02 Verify that result is a INTEGER
if (serialNumber.Data.ToHexString() != SerialNumber.Data.ToHexString())
{
return(false); // Serial Number of certificate wrong
}
//Get hash of NIS and verify it with NIS stored in file system
var dgsHash = SignedData.Child(2, 0x30); //0x30 Verify that result is a SEQUENCE
var isValidNis = false;
foreach (var dg in dgsHash.children)
{
/*
* 0xa1 : IdServizi
* 0xa2 : Seriale carta
* 0xa3 : Certificato utente
* 0xa4 : Chiave pubblica di Internal Authentication
* 0xa5 : Chiave pubblica di Internal Authentication per i Servizi
* 0x1b : Parametri DH
*/
var oID = dg.Child(0, 02); //02 Verify that result is a INTEGER
if (oID.Data.ToHexString() == "a1")
{
//Get hashed NIS from DG
var hashedNis = dg.Child(1, 04).Data; //04 Verify that result is a OCTECT STRING
//Calculate hash of file nis and compare it with the other in dg
if (hashedNis.ToHexString() == nis.ToMessageDigest(digestAlgo).ToHexString())
{
isValidNis = true;
}
}
}
//TODO: Check that certificate is issued by https://csca-ita.interno.gov.it/index_ITA.htm (CSCA certificate)
return(isValidNis);
}
