signmsg.c

This is an example of how to call the SDK member APIs.

/*############################################################################
  # Copyright 2016 Intel Corporation
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  ############################################################################*/

#include <stdlib.h>
#include <string.h>
#include "src/signmsg.h"
#include "src/prng.h"
#include "util/envutil.h"
#include "util/stdtypes.h"
#include "util/buffutil.h"

bool IsCaCertAuthorizedByRootCa(void const* data, size_t size) {
  // Implementation of this function is out of scope of the sample.
  // In an actual implementation Issuing CA certificate must be validated
  // with CA Root certificate before using it in parse functions.
  (void)data;
  (void)size;
  return true;
}

EpidStatus SignMsg(void const* msg, size_t msg_len, void const* basename,
                   size_t basename_len, unsigned char const* signed_sig_rl,
                   size_t signed_sig_rl_size,
                   unsigned char const* signed_pubkey,
                   size_t signed_pubkey_size, unsigned char const* priv_key_ptr,
                   size_t privkey_size, HashAlg hash_alg,
                   MemberPrecomp* member_precomp, bool member_precomp_is_input,
                   EpidSignature** sig, size_t* sig_len,
                   EpidCaCertificate const* cacert) {
  EpidStatus sts = kEpidErr;
  void* prng = NULL;
  MemberCtx* member = NULL;

  SigRl* sig_rl = NULL;
  size_t sig_rl_size = 0;

  do {
    GroupPubKey pub_key = {0};
    PrivKey priv_key = {0};

    if (!sig) {
      sts = kEpidBadArgErr;
      break;
    }

    // authenticate and extract group public key
    sts = EpidParseGroupPubKeyFile(signed_pubkey, signed_pubkey_size, cacert,
                                   &pub_key);
    if (kEpidNoErr != sts) {
      break;
    }

    if (signed_sig_rl) {
      // authenticate and determine space needed for SigRl
      sts = EpidParseSigRlFile(signed_sig_rl, signed_sig_rl_size, cacert,
                               sig_rl, &sig_rl_size);
      if (kEpidSigInvalid == sts) {
        // authentication failure
        break;
      }
      if (kEpidNoErr != sts) {
        break;
      }
      sig_rl = AllocBuffer(sig_rl_size);
      if (!sig_rl) {
        sts = kEpidMemAllocErr;
        break;
      }

      // fill the SigRl
      sts = EpidParseSigRlFile(signed_sig_rl, signed_sig_rl_size, cacert,
                               sig_rl, &sig_rl_size);
      if (kEpidSigInvalid == sts) {
        // authentication failure
        break;
      }
      if (kEpidNoErr != sts) {
        break;
      }
    }

    // acquire PRNG
    sts = PrngCreate(&prng);
    if (kEpidNoErr != sts) {
      break;
    }

    // decompress private key
    if (privkey_size == sizeof(PrivKey)) {
      priv_key = *(PrivKey*)priv_key_ptr;
    } else if (privkey_size == sizeof(CompressedPrivKey)) {
      sts = EpidDecompressPrivKey(&pub_key, (CompressedPrivKey*)priv_key_ptr,
                                  &priv_key);
      if (kEpidNoErr != sts) {
        break;
      }
    } else {
      sts = kEpidErr;
      break;
    }

    // create member
    sts = EpidMemberCreate(&pub_key, &priv_key,
                           member_precomp_is_input ? member_precomp : NULL,
                           PrngGen, prng, &member);
    if (kEpidNoErr != sts) {
      break;
    }

    // return member pre-computation blob if requested
    sts = EpidMemberWritePrecomp(member, member_precomp);
    if (kEpidNoErr != sts) {
      break;
    }

    // register any provided basename as allowed
    if (0 != basename_len) {
      sts = EpidRegisterBaseName(member, basename, basename_len);
      if (kEpidNoErr != sts) {
        break;
      }
    }

    sts = EpidMemberSetHashAlg(member, hash_alg);
    if (kEpidNoErr != sts) {
      break;
    }

    // Signature
    // Note: Signature size must be computed after sig_rl is loaded.
    *sig_len = EpidGetSigSize(sig_rl);

    *sig = AllocBuffer(*sig_len);
    if (!*sig) {
      sts = kEpidMemAllocErr;
      break;
    }

    // sign message
    sts = EpidSign(member, msg, msg_len, basename, basename_len, sig_rl,
                   sig_rl_size, *sig, *sig_len);
    if (kEpidNoErr != sts) {
      break;
    }
    sts = kEpidNoErr;
  } while (0);

  PrngDelete(&prng);
  EpidMemberDelete(&member);

  if (sig_rl) free(sig_rl);

  return sts;
}