HMAC.c

// This file was extracted from the TCG Published
// Trusted Platform Module Library
// Part 3: Commands
// Family "2.0"
// Level 00 Revision 01.16
// October 30, 2014

#include "InternalRoutines.h"
#include "HMAC_fp.h"
//
//
//     Error Returns                     Meaning
//
//     TPM_RC_ATTRIBUTES                 key referenced by handle is not a signing key or is a restricted key
//     TPM_RC_TYPE                       key referenced by handle is not an HMAC key
//     TPM_RC_VALUE                      hashAlg is not compatible with the hash algorithm of the scheme of
//                                       the object referenced by handle
//
TPM_RC
TPM2_HMAC(
   HMAC_In           *in,                 // IN: input parameter list
   HMAC_Out          *out                 // OUT: output parameter list
   )
{
   HMAC_STATE                 hmacState;
   OBJECT                    *hmacObject;
   TPMI_ALG_HASH              hashAlg;
   TPMT_PUBLIC               *publicArea;

// Input Validation

   // Get HMAC key object and public area pointers
   hmacObject = ObjectGet(in->handle);
   publicArea = &hmacObject->publicArea;

   // Make sure that the key is an HMAC key
   if(publicArea->type != TPM_ALG_KEYEDHASH)
       return TPM_RCS_TYPE + RC_HMAC_handle;

   // and that it is unrestricted
   if(publicArea->objectAttributes.restricted == SET)
       return TPM_RCS_ATTRIBUTES + RC_HMAC_handle;

   // and that it is a signing key
   if(publicArea->objectAttributes.sign != SET)
       return TPM_RCS_KEY + RC_HMAC_handle;

   // See if the key has a default
   if(publicArea->parameters.keyedHashDetail.scheme.scheme == TPM_ALG_NULL)
       // it doesn't so use the input value
       hashAlg = in->hashAlg;
   else
   {
       // key has a default so use it
       hashAlg
           = publicArea->parameters.keyedHashDetail.scheme.details.hmac.hashAlg;
       // and verify that the input was either the TPM_ALG_NULL or the default
       if(in->hashAlg != TPM_ALG_NULL && in->hashAlg != hashAlg)
           hashAlg = TPM_ALG_NULL;
   }
   // if we ended up without a hash algorith then return an error
   if(hashAlg == TPM_ALG_NULL)
       return TPM_RCS_VALUE + RC_HMAC_hashAlg;

// Command Output

  // Start HMAC stack
  out->outHMAC.t.size = CryptStartHMAC2B(hashAlg,
                                         &hmacObject->sensitive.sensitive.bits.b,
                                         &hmacState);
  // Adding HMAC data
  CryptUpdateDigest2B(&hmacState, &in->buffer.b);

  // Complete HMAC
  CryptCompleteHMAC2B(&hmacState, &out->outHMAC.b);

   return TPM_RC_SUCCESS;
}