PKCS11 unwrap private RSA key to eToken HSM

Question

I am trying to transfer an RSA private key to my HSM (SafeNet eToken) via PKCS#11 interop, and and then unwrap it on the HSM.

This is my code (updated):

            session.Login(CKU.CKU_USER, pin);
            var x509Certificate = new X509Certificate2(File.ReadAllBytes(path), "", X509KeyStorageFlags.Exportable);
            var privateKey = x509Certificate.PrivateKey as RSACryptoServiceProvider;
            var keyPair = DotNetUtilities.GetRsaKeyPair(privateKey);
            byte[] privateKeyBytes;
            using (var memoryStream = new MemoryStream())
            {
                using (TextWriter streamWriter = new StreamWriter(memoryStream))
                {
                    var pemWriter = new PemWriter(streamWriter);
                    pemWriter.WriteObject(keyPair.Private);
                    streamWriter.Flush();
                }
                privateKeyBytes = memoryStream.GetBuffer();
            }

            // Create temporary DES3 key for wrapping/unwrapping
            var tempKeyAttributes = new List<ObjectAttribute>
            {
                new ObjectAttribute(CKA.CKA_CLASS, CKO.CKO_SECRET_KEY),
                new ObjectAttribute(CKA.CKA_KEY_TYPE, CKK.CKK_DES3),
                new ObjectAttribute(CKA.CKA_ENCRYPT, true),
                new ObjectAttribute(CKA.CKA_UNWRAP, true)
            };
            var tempKey = session.GenerateKey(new Mechanism(CKM.CKM_DES3_KEY_GEN), tempKeyAttributes);

            var encrypted =
                session.Encrypt(new Mechanism(CKM.CKM_DES3_ECB), tempKey, privateKeyBytes);

            string label = "private1";

            // Define how the new RSA private key should look like on the HSM
            var privateKeyAttributes = new List<ObjectAttribute>
            {
                new ObjectAttribute(CKA.CKA_CLASS, CKO.CKO_PRIVATE_KEY),
                new ObjectAttribute(CKA.CKA_TOKEN, true),
                new ObjectAttribute(CKA.CKA_PRIVATE, true),
                new ObjectAttribute(CKA.CKA_MODIFIABLE, true),
                new ObjectAttribute(CKA.CKA_SENSITIVE, false),
                new ObjectAttribute(CKA.CKA_LABEL, label),
                new ObjectAttribute(CKA.CKA_ID, Encoding.ASCII.GetBytes(label)),
                new ObjectAttribute(CKA.CKA_ALWAYS_AUTHENTICATE, false),
                new ObjectAttribute(CKA.CKA_KEY_TYPE, CKK.CKK_RSA),

            };
            var privateKeyHandle = session.UnwrapKey(new Mechanism(CKM.CKM_DES3_ECB), tempKey,
                encrypted, privateKeyAttributes);


//results in: Method C_UnwrapKey returned CKR_WRAPPED_KEY_INVALID

But it does not work - fails with Net.Pkcs11Interop.Common.Pkcs11Exception: Method C_UnwrapKey returned CKR_TEMPLATE_INCONSISTENT.

(UPDATED) Now it results in CKR_WRAPPED_KEY_INVALID. But if I import the same PFX file manuall using SafeNet, no errors occur - everything seems fine.

Any ideas? Maybe there are some parameters I used wrong?

Answer 1

FINALLY the code that does the thing:

   var x509Certificate = new X509Certificate2(File.ReadAllBytes(path), "",
                X509KeyStorageFlags.Exportable);
            var privateKey = x509Certificate.PrivateKey as RSACryptoServiceProvider;
            if (privateKey == null) throw new Exception($"Private key is null for {x509Certificate.SerialNumber}");
            var privateKeyParams = privateKey.ExportParameters(true);
            session.Login(CKU.CKU_USER, pin);
            // Create temporary DES3 key for wrapping/unwrapping
            var tempKeyAttributes = new List<ObjectAttribute>
            {
                new ObjectAttribute(CKA.CKA_CLASS, CKO.CKO_SECRET_KEY),
                new ObjectAttribute(CKA.CKA_KEY_TYPE, CKK.CKK_DES3),
                new ObjectAttribute(CKA.CKA_ENCRYPT, true),
                new ObjectAttribute(CKA.CKA_DECRYPT, true),
                new ObjectAttribute(CKA.CKA_UNWRAP, true),
                new ObjectAttribute(CKA.CKA_WRAP, true)
            };
            // Preparing unencrypted private key
            var unencryptedPrivateKey = PrivateKeyInfoFactory.CreatePrivateKeyInfo(
                new RsaPrivateCrtKeyParameters(
                    new BigInteger(1, privateKeyParams.Modulus),
                    new BigInteger(1, privateKeyParams.Exponent),
                    new BigInteger(1, privateKeyParams.D),
                    new BigInteger(1, privateKeyParams.P),
                    new BigInteger(1, privateKeyParams.Q),
                    new BigInteger(1, privateKeyParams.DP),
                    new BigInteger(1, privateKeyParams.DQ),
                    new BigInteger(1, privateKeyParams.InverseQ))).GetEncoded();
            var tempKey = session.GenerateKey(new Mechanism(CKM.CKM_DES3_KEY_GEN), tempKeyAttributes);
            var result = new MemoryStream();
            var stream = new MemoryStream(unencryptedPrivateKey);
            //Encrypting
            session.Encrypt(new Mechanism(CKM.CKM_DES3_ECB), tempKey, stream,
                result);
            var encrypted = result.ToArray();
            string label = x509Certificate.SerialNumber;
            // Define how the new RSA private key should look like on the HSM
            var privateKeyAttributes = new List<ObjectAttribute>
            {
                new ObjectAttribute(CKA.CKA_CLASS, CKO.CKO_PRIVATE_KEY),
                new ObjectAttribute(CKA.CKA_TOKEN, true),
                new ObjectAttribute(CKA.CKA_PRIVATE, true),
                new ObjectAttribute(CKA.CKA_MODIFIABLE, true),
                new ObjectAttribute(CKA.CKA_SENSITIVE, false),
                new ObjectAttribute(CKA.CKA_LABEL, label),
                new ObjectAttribute(CKA.CKA_ID, Encoding.ASCII.GetBytes(label)),
                new ObjectAttribute(CKA.CKA_KEY_TYPE, CKK.CKK_RSA)
            };
            var privateKeyHandle = session.UnwrapKey(new Mechanism(CKM.CKM_DES3_ECB), tempKey,
                encrypted, privateKeyAttributes);
            return privateKeyHandle;