Pkcs11Interop read key value from HSM

I'm trying to use Pkcs11Interop to extract the value of the key from the HSM. I know, the key has to stay in the HSM, but I need it, so...

I already do it with NCryptoki and I'd like to do it also with Pkcs11Interop

I tried this code:

// Prepare attribute template that defines search criteria
List<ObjectAttribute> objectAttributes = new List<ObjectAttribute>();
objectAttributes.Add(new ObjectAttribute(CKA.CKA_CLASS, CKO.CKO_SECRET_KEY));
objectAttributes.Add(new ObjectAttribute(CKA.CKA_KEY_TYPE, CKK.CKK_DES));
objectAttributes.Add(new ObjectAttribute(CKA.CKA_LABEL, "MY_KEY"));

// Find all objects that match provided attributes
List<ObjectHandle> foundObjects = session.FindAllObjects(objectAttributes);

var key = foundObjects[0];
 byte[] plainKeyValue = null;
 List<ObjectAttribute> readAttrs = session.GetAttributeValue(key, new List<CKA>() { CKA.CKA_VALUE });
 if (readAttrs[0].CannotBeRead)
     throw new Exception("Key cannot be exported");
 else
     plainKeyValue = readAttrs[0].GetValueAsByteArray();

But the plainKeyValue is all zeros, but, as you can imagine, this is not true.

SO, how can I reach my goal?

I solved it with this code

static public byte[] findTargetKeySValue(String label, String type, string command)
{
    try
    {
        string pkcs11LibraryPath = @"C:\Program Files\SafeNet\Protect Toolkit 5\Protect Toolkit C SDK\bin\hsm\cryptoki.dll";
        Utility.Logger("cryptoki dll path " + pkcs11LibraryPath, command);
        using (Pkcs11 pkcs11 = new Pkcs11(pkcs11LibraryPath, Inter_Settings.AppType))
        {
            // Find first slot with token present
            Slot slot = Inter_Helpers.GetUsableSlot(pkcs11);
            // Open RW session
            using (Session session = slot.OpenSession(SessionType.ReadOnly))
            {
                // Login as normal user
                session.Login(CKU.CKU_USER, Inter_Settings.NormalUserPin);
                // Prepare attribute template that defines search criteria
                List<ObjectAttribute> objectAttributes = new List<ObjectAttribute>();
                objectAttributes.Add(new ObjectAttribute(CKA.CKA_CLASS, CKO.CKO_SECRET_KEY));
                if (type == "DES")
                    objectAttributes.Add(new ObjectAttribute(CKA.CKA_KEY_TYPE, CKK.CKK_DES));
                else if (type == "DES2")
                    objectAttributes.Add(new ObjectAttribute(CKA.CKA_KEY_TYPE, CKK.CKK_DES2));
                else if (type == "DES3")
                    objectAttributes.Add(new ObjectAttribute(CKA.CKA_KEY_TYPE, CKK.CKK_DES3));
                objectAttributes.Add(new ObjectAttribute(CKA.CKA_LABEL, label));//PROVAK

                List<ObjectHandle> foundObjects = session.FindAllObjects(objectAttributes);
                var key = foundObjects[0];
                byte[] plainKeyValue = null;
                List<ObjectAttribute> readAttrsSensitive = session.GetAttributeValue(key, new List<CKA>() { CKA.CKA_SENSITIVE });
                if (!readAttrsSensitive[0].GetValueAsBool())
                {
                    Utility.Logger("findTargetKeySValue chiave " + label + " non senstive", command);
                    List<ObjectAttribute> readAttrs = session.GetAttributeValue(key, new List<CKA>() { CKA.CKA_VALUE });
                    if (readAttrs[0].CannotBeRead)
                        throw new Exception("Key cannot be exported");
                    else
                        plainKeyValue = readAttrs[0].GetValueAsByteArray();
                    //Console.WriteLine(ByteArrayToAsciiHEX(plainKeyValue));
                    session.Logout();
                    return plainKeyValue;
                }
                else
                {
                    Utility.Logger("findTargetKeySValue chiave " + label + " senstive", command);
                    Console.WriteLine("wrap/unwrap");
                    objectAttributes = new List<ObjectAttribute>();
                    objectAttributes.Add(new ObjectAttribute(CKA.CKA_CLASS, CKO.CKO_SECRET_KEY));
                    objectAttributes.Add(new ObjectAttribute(CKA.CKA_KEY_TYPE, CKK.CKK_DES3));
                    objectAttributes.Add(new ObjectAttribute(CKA.CKA_LABEL, "WRAPPING_KEY")); //WRAPPING_KEY WRK
                    foundObjects = session.FindAllObjects(objectAttributes);

                    var wrappingKey = foundObjects[0];
                    Mechanism m = new Mechanism(CKM.CKM_DES3_ECB);

                    var wrapped = session.WrapKey(m, wrappingKey, key);
                    //Console.WriteLine("wrapped " + ByteArrayToAsciiHEX(wrapped));

                    //Console.WriteLine(ByteArrayToAsciiHEX(session.Decrypt(m, wrappingKey, wrapped)));
                    var k = session.Decrypt(m, wrappingKey, wrapped); 
                    session.Logout();
                    return k;

                }
            }
        }
    }
    catch (Exception e)
    {
        //Console.WriteLine(e.ToSafeString());
        Utility.Logger("findTargetKeySValue " + e.ToSafeString(), command);
        return null;
    }
}