PKCS11 key wrapping using openssl

Question

I'm tring to perform key wrapping operation on a smart card hardware using C_WrapKey() with a public key loaded by CreateObject. I get back an encrypted byte array as a result. Is it possible to perform the same operation using openssl?

I tried using opensal as follows:

openssl rsautl -encrypt -in symkey.data -out symkey.enc -pubin rsaPub.der -keyform DER -pkcs

symkey.data: 192 bits DES3 key 
rsaPub.der : 128 bit RSA Public key in DER format

The resulting symkey.enc file is 128 bytes in size, but the result from my hardware is always 256 bytes. I suppose it's about padding but not sure.

Answer 1

To answer your specific case:

RFC3447 says that RSAES-PKCS1-v1_5 encryption scheme can operate on messages of length up to k - 11 octets (k is the octet length of the RSA modulus) so there is no way you can use 128bit RSA key to encrypt 192bit DES3 key. OpenSSL would end up with the following error:

openssl rsautl -encrypt -in symkey.data -out symkey.enc -pubin -inkey rsaPub.der -keyform DER -pkcs
RSA operation error
7240:error:0406D06D:rsa routines:RSA_padding_add_PKCS1_type_2:data too large for key size:.\crypto\rsa\rsa_pk1.c:151:

Are you sure that you have provided correct information in your question?

To answer key wrapping with OpenSSL in general:

Yes it is possible to wrap/unwrap DES3 key with the RSA key using OpenSSL. Mechanism CKM_RSA_PKCS you are using with your PKCS#11 library identifies RSAES-PKCS1-v1_5 encryption scheme (RSA encryption with PKCS#1 v1.5 padding) which is fully supported by OpenSSL.

You can easily check out that my answer is correct with the command line OpenSSL tool and a few lines of code that use PKCS#11 library:

1. Generate RSA key pair:

   openssl genrsa -out private.key 2048
   

2. Extract RSA public key from generated RSA key pair:

   openssl rsa -in private.key -pubout -out public.key
   

3. Extract modulus and exponent from RSA public key:

   openssl rsa -in public.key -pubin -text
   

4. Import RSA public key into your PKCS#11 token, generate DES3 key, wrap DES3 key with RSA public key and save results (code is written in C#):

   using (Pkcs11 pkcs11 = new Pkcs11("siecap11.dll", false))
   {
       // Find first slot with token present
       Slot slot = pkcs11.GetSlotList(true)[0];
   
       // Open RW session
       using (Session session = slot.OpenSession(false))
       {
           // Login as normal user
           session.Login(CKU.CKU_USER, "11111111");
   
           // Define attributes of RSA public key
           List<ObjectAttribute> publicKeyAttributes = new List<ObjectAttribute>();
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_CLASS, CKO.CKO_PUBLIC_KEY));
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_KEY_TYPE, CKK.CKK_RSA));
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_TOKEN, true));
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_PRIVATE, false));
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_LABEL, "WrapTest"));
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_ID, ConvertUtils.HexStringToBytes("00010203040506070809")));
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_ENCRYPT, true));
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_VERIFY, true));
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_VERIFY_RECOVER, true));
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_WRAP, true));
           // Use modulus extracted from RSA public key
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_MODULUS, ConvertUtils.HexStringToBytes("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")));
           // Use exponent extracted from RSA public key
           publicKeyAttributes.Add(new ObjectAttribute(CKA.CKA_PUBLIC_EXPONENT, ConvertUtils.HexStringToBytes("010001")));
   
           // Import public key
           ObjectHandle pubKey = session.CreateObject(publicKeyAttributes);
   
           // Define attributes of DES key
           List<ObjectAttribute> desKeyAttributes = new List<ObjectAttribute>();
           desKeyAttributes.Add(new ObjectAttribute(CKA.CKA_CLASS, CKO.CKO_SECRET_KEY));
           desKeyAttributes.Add(new ObjectAttribute(CKA.CKA_KEY_TYPE, CKK.CKK_DES3));
           desKeyAttributes.Add(new ObjectAttribute(CKA.CKA_ENCRYPT, true));
           desKeyAttributes.Add(new ObjectAttribute(CKA.CKA_DECRYPT, true));
           desKeyAttributes.Add(new ObjectAttribute(CKA.CKA_DERIVE, true));
           desKeyAttributes.Add(new ObjectAttribute(CKA.CKA_EXTRACTABLE, true));
   
           // Generate DES key
           ObjectHandle desKey = session.GenerateKey(new Mechanism(CKM.CKM_DES3_KEY_GEN), desKeyAttributes);
   
           // Read value of DES key
           desKeyAttributes = session.GetAttributeValue(desKey, new List<CKA>() { CKA.CKA_VALUE });
           byte[] desKeyValue = desKeyAttributes[0].GetValueAsByteArray();
           System.IO.File.WriteAllBytes(@"des.key", desKeyValue);
   
           // Wrap key
           byte[] wrappedKey = session.WrapKey(new Mechanism(CKM.CKM_RSA_PKCS), pubKey, desKey);
           System.IO.File.WriteAllBytes(@"wrapped.key", wrappedKey);
   
           session.DestroyObject(pubKey);
           session.DestroyObject(desKey);
           session.Logout();
       }
   }
   

5. Unwrap DES3 key with RSA private key:

   openssl rsautl -decrypt -pkcs -inkey private.key -in wrapped.key -out unwrapped.key
   

6. There is exactly same content/key stored in "des.key" and "unwrapped.key" files. This indicates successful unwrapping.

7. Alternatively use OpenSSL to wrap DES3 key with RSA public key:

   openssl rsautl -encrypt -pkcs -pubin -inkey public.key -in unwrapped.key -out wrapped2.key