Wrap a secret key with a public key using PKCS#11

Question

In my C program, I generate a public/private key pair with the function C_GenerateKeyPair and a sensitive (secret) key with C_GenerateKey. The aim is to wrap the secret key with the public key, but when I call the function C_WrapKey, I get the error CKR_KEY_TYPE_INCONSISTENT. The code runs if I use another wrapping secret key with attributes Wrap and Encrypt set. The template used for the public key is the one proposed in PKCS#11 documentation:

CK_SESSION_HANDLE hSession;
CK_OBJECT_HANDLE hPublicKey, hPrivateKey;
CK_MECHANISM mechanism = {
   CKM_RSA_PKCS_KEY_PAIR_GEN, NULL_PTR, 0
};
CK_ULONG modulusBits = 768;
CK_BYTE publicExponent[] = { 3 };
CK_BYTE id[] = {123};
CK_BBOOL true = CK_TRUE;
CK_ATTRIBUTE publicKeyTemplate[] = {
   {CKA_ENCRYPT, &true, sizeof(true)},
   {CKA_VERIFY, &true, sizeof(true)},
   {CKA_WRAP, &true, sizeof(true)},
   {CKA_MODULUS_BITS, &modulusBits, sizeof(modulusBits)},
   {CKA_PUBLIC_EXPONENT, publicExponent, sizeof(publicExponent)}
};

The Wrap and Encrypt attribute are correctly specified, while for the secret key to be wrapped I add the attribute CKA_EXTRACTABLE. Thanks in advance for your help.

Answer 1

The error CKR_KEY_TYPE_INCONSISTENT is due to a wrong CK_MECHANISM, used in the function C_WrapKey. If we want to wrap a secret key with a RSA public key, set the following mechanism:

CK_MECHANISM dec_mec = {CKM_RSA_PKCS, NULL_PTR, 0};