internal ECDsaCng MakeECDsa(COSE.Algorithm alg, COSE.EllipticCurve crv)
{
ECCurve curve;
switch (alg)
{
case COSE.Algorithm.ES256:
switch (crv)
{
case COSE.EllipticCurve.P256:
case COSE.EllipticCurve.P256K:
curve = ECCurve.NamedCurves.nistP256;
break;
default:
throw new ArgumentOutOfRangeException(string.Format("Missing or unknown crv {0}", crv.ToString()));
}
break;
case COSE.Algorithm.ES384:
switch (crv) // https://www.iana.org/assignments/cose/cose.xhtml#elliptic-curves
{
case COSE.EllipticCurve.P384:
curve = ECCurve.NamedCurves.nistP384;
break;
default:
throw new ArgumentOutOfRangeException(string.Format("Missing or unknown crv {0}", crv.ToString()));
}
break;
case COSE.Algorithm.ES512:
switch (crv) // https://www.iana.org/assignments/cose/cose.xhtml#elliptic-curves
{
case COSE.EllipticCurve.P521:
curve = ECCurve.NamedCurves.nistP521;
break;
default:
throw new ArgumentOutOfRangeException(string.Format("Missing or unknown crv {0}", crv.ToString()));
}
break;
default:
throw new ArgumentOutOfRangeException(string.Format("Missing or unknown alg {0}", alg.ToString()));
}
return(new ECDsaCng(curve));
}
internal async void MakeAssertionResponse(COSE.KeyType kty, COSE.Algorithm alg, COSE.EllipticCurve crv = COSE.EllipticCurve.P256)
{
const string rp = "fido2.azurewebsites.net";
byte[] rpId = System.Text.Encoding.UTF8.GetBytes(rp);
var rpIdHash = SHA256.Create().ComputeHash(rpId);
var flags = AuthenticatorFlags.AT | AuthenticatorFlags.ED | AuthenticatorFlags.UP | AuthenticatorFlags.UV;
const UInt16 signCount = 0xf1d0;
var aaguid = new Guid("F1D0F1D0-F1D0-F1D0-F1D0-F1D0F1D0F1D0");
var credentialID = new byte[] { 0xf1, 0xd0, 0xf1, 0xd0, 0xf1, 0xd0, 0xf1, 0xd0, 0xf1, 0xd0, 0xf1, 0xd0, 0xf1, 0xd0, 0xf1, 0xd0, };
CredentialPublicKey cpk = null;
ECDsaCng ecdsa = null;
RSACng rsa = null;
byte[] privateKeySeed, publicKey, expandedPrivateKey = null;
switch (kty)
{
case COSE.KeyType.EC2:
{
ecdsa = MakeECDsa(alg, crv);
var ecparams = ecdsa.ExportParameters(true);
cpk = MakeCredentialPublicKey(kty, alg, crv, ecparams.Q.X, ecparams.Q.Y);
break;
}
case COSE.KeyType.RSA:
{
rsa = new RSACng();
var rsaparams = rsa.ExportParameters(true);
cpk = MakeCredentialPublicKey(kty, alg, rsaparams.Modulus, rsaparams.Exponent);
break;
}
case COSE.KeyType.OKP:
{
MakeEdDSA(out privateKeySeed, out publicKey, out expandedPrivateKey);
cpk = MakeCredentialPublicKey(kty, alg, COSE.EllipticCurve.Ed25519, publicKey);
break;
}
throw new ArgumentOutOfRangeException(string.Format("Missing or unknown kty {0}", kty.ToString()));
}
var acd = new AttestedCredentialData(aaguid, credentialID, cpk);
var extBytes = CBORObject.NewMap().Add("testing", true).EncodeToBytes();
var exts = new Extensions(extBytes);
var ad = new AuthenticatorData(rpIdHash, flags, signCount, acd, exts);
var authData = ad.ToByteArray();
var challenge = new byte[128];
var rng = RandomNumberGenerator.Create();
rng.GetBytes(challenge);
var clientData = new
{
Type = "webauthn.get",
Challenge = challenge,
Origin = rp,
};
var clientDataJson = System.Text.Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(clientData));
var sha = SHA256.Create();
var hashedClientDataJson = sha.ComputeHash(clientDataJson);
byte[] data = new byte[authData.Length + hashedClientDataJson.Length];
Buffer.BlockCopy(authData, 0, data, 0, authData.Length);
Buffer.BlockCopy(hashedClientDataJson, 0, data, authData.Length, hashedClientDataJson.Length);
byte[] signature = null;
switch (kty)
{
case COSE.KeyType.EC2:
{
signature = ecdsa.SignData(data, CryptoUtils.algMap[(int)alg]);
break;
}
case COSE.KeyType.RSA:
{
RSASignaturePadding padding;
switch (alg) // https://www.iana.org/assignments/cose/cose.xhtml#algorithms
{
case COSE.Algorithm.PS256:
case COSE.Algorithm.PS384:
case COSE.Algorithm.PS512:
padding = RSASignaturePadding.Pss;
break;
case COSE.Algorithm.RS1:
case COSE.Algorithm.RS256:
case COSE.Algorithm.RS384:
case COSE.Algorithm.RS512:
padding = RSASignaturePadding.Pkcs1;
break;
default:
throw new ArgumentOutOfRangeException(string.Format("Missing or unknown alg {0}", alg.ToString()));
}
signature = rsa.SignData(data, CryptoUtils.algMap[(int)alg], padding);
break;
}
case COSE.KeyType.OKP:
{
data = CryptoUtils.GetHasher(HashAlgorithmName.SHA512).ComputeHash(data);
signature = Chaos.NaCl.Ed25519.Sign(data, expandedPrivateKey);
break;
}
throw new ArgumentOutOfRangeException(string.Format("Missing or unknown kty {0}", kty.ToString()));
}
if (kty == COSE.KeyType.EC2)
{
signature = EcDsaSigFromSig(signature, ecdsa.KeySize);
}
var userHandle = new byte[16];
rng.GetBytes(userHandle);
var assertion = new AuthenticatorAssertionRawResponse.AssertionResponse()
{
AuthenticatorData = authData,
Signature = signature,
ClientDataJson = clientDataJson,
UserHandle = userHandle,
};
var lib = new Fido2(new Fido2Configuration()
{
ServerDomain = rp,
ServerName = rp,
Origin = rp,
});
List <PublicKeyCredentialDescriptor> existingCredentials = new List <PublicKeyCredentialDescriptor>();
var cred = new PublicKeyCredentialDescriptor();
cred.Type = PublicKeyCredentialType.PublicKey;
cred.Id = new byte[] { 0xf1, 0xd0 };
existingCredentials.Add(cred);
var options = lib.GetAssertionOptions(existingCredentials, null, null);
options.Challenge = challenge;
var response = new AuthenticatorAssertionRawResponse()
{
Response = assertion,
Type = PublicKeyCredentialType.PublicKey,
Id = new byte[] { 0xf1, 0xd0 },
RawId = new byte[] { 0xf1, 0xd0 },
};
IsUserHandleOwnerOfCredentialIdAsync callback = (args) =>
{
return(Task.FromResult(true));
};
var res = await lib.MakeAssertionAsync(response, options, cpk.GetBytes(), signCount - 1, callback);
}