epid/member/src/sign.c

/*############################################################################
  # Copyright 2016-2017 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.
  ############################################################################*/
/// EpidSign implementation.
/*! \file */
#include <epid/member/api.h>

#include <string.h>
#include "epid/common/src/endian_convert.h"
#include "epid/common/src/memory.h"
#include "epid/common/src/sigrlvalid.h"
#include "epid/member/src/context.h"
#include "epid/member/src/nrprove.h"
#include "epid/member/src/signbasic.h"

/// Handle SDK Error with Break
#define BREAK_ON_EPID_ERROR(ret) \
  if (kEpidNoErr != (ret)) {     \
    break;                       \
  }

EpidStatus EpidSign(MemberCtx const* ctx, void const* msg, size_t msg_len,
                    void const* basename, size_t basename_len,
                    EpidSignature* sig, size_t sig_len) {
  EpidStatus sts = kEpidErr;
  uint32_t num_sig_rl = 0;
  OctStr32 octstr32_0 = {{0x00, 0x00, 0x00, 0x00}};
  BigNumStr rnd_bsn = {0};
  if (!ctx || !sig) {
    return kEpidBadArgErr;
  }
  if (!msg && (0 != msg_len)) {
    // if message is non-empty it must have both length and content
    return kEpidBadArgErr;
  }
  if (!basename && (0 != basename_len)) {
    // if basename is non-empty it must have both length and content
    return kEpidBadArgErr;
  }
  if (!ctx->is_provisioned) {
    return kEpidOutOfSequenceError;
  }
  if (EpidGetSigSize(ctx->sig_rl) > sig_len) {
    return kEpidBadArgErr;
  }

  // 11. The member sets sigma0 = (B, K, T, c, sx, sf, sa, sb).
  sts = EpidSignBasic(ctx, msg, msg_len, basename, basename_len, &sig->sigma0,
                      &rnd_bsn);
  if (kEpidNoErr != sts) {
    return sts;
  }

  if (!ctx->sig_rl) {
    // 12. If SigRL is not provided as input,
    //   a. The member sets RLver = 0 and n2 = 0.
    //   b. The member outputs (sigma0, RLver, n2) and returns "succeeded".
    sig->rl_ver = octstr32_0;
    sig->n2 = octstr32_0;
    return kEpidNoErr;
  } else {
    uint32_t i = 0;
    EpidStatus nr_prove_status = kEpidNoErr;
    // 13. If SigRL is provided as input, the member proceeds with
    //     the following steps:
    //   a. The member verifies that gid in public key and in SigRL
    //      match.
    //      This was done under EpidMemberSetSigRl function.
    //   b. The member copies RLver and n2 values in SigRL to the
    //      signature.
    sig->rl_ver = ctx->sig_rl->version;
    sig->n2 = ctx->sig_rl->n2;
    //   c. For i = 0, ..., n2-1, the member computes sigma[i] =
    //      nrProve(f, B, K, B[i], K[i]). The details of nrProve()
    //      will be given in the next subsection.
    num_sig_rl = ntohl(ctx->sig_rl->n2);
    for (i = 0; i < num_sig_rl; i++) {
      if (basename) {
        sts = EpidNrProve(ctx, msg, msg_len, basename, basename_len,
                          &sig->sigma0, &ctx->sig_rl->bk[i], &sig->sigma[i]);
      } else {
        sts = EpidNrProve(ctx, msg, msg_len, &rnd_bsn, sizeof(rnd_bsn),
                          &sig->sigma0, &ctx->sig_rl->bk[i], &sig->sigma[i]);
      }
      if (kEpidNoErr != sts) {
        nr_prove_status = sts;
      }
    }
    if (kEpidNoErr != nr_prove_status) {
      memset(&sig->sigma[0], 0, num_sig_rl * sizeof(sig->sigma[0]));
      return nr_prove_status;
    }
  }
  //   d. The member outputs (sigma0, RLver, n2, sigma[0], ...,
  //      sigma[n2-1]).
  //   e. If any of the nrProve() functions outputs "failed", the
  //      member returns "revoked", otherwise returns "succeeded".
  return kEpidNoErr;
}