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/*############################################################################
# Copyright 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.
############################################################################*/
/// Tpm2Commit implementation.
/*! \file */
#include "epid/member/tpm2/commit.h"
#include "epid/common/math/ecgroup.h"
#include "epid/common/math/finitefield.h"
#include "epid/common/src/epid2params.h"
#include "epid/common/src/memory.h"
#include "epid/member/tpm2/src/state.h"
/// Handle Intel(R) EPID Error with Break
#define BREAK_ON_EPID_ERROR(ret) \
if (kEpidNoErr != (ret)) { \
break; \
}
static EpidStatus InsertR(Tpm2Ctx* ctx, FfElement* r, uint16_t* counter) {
uint16_t index = 0;
if (!ctx || !r || !counter) {
return kEpidBadArgErr;
}
for (index = 0; index < MAX_COMMIT_COUNT; ++index) {
if (!ctx->commit_data[index]) {
ctx->commit_data[index] = r;
break;
}
}
if (index == MAX_COMMIT_COUNT) {
return kEpidMemAllocErr;
}
*counter = index + 1; // counter == 0 should be invalid
return kEpidNoErr;
}
static void DeleteR(Tpm2Ctx* ctx, uint16_t* counter) {
if (counter && *counter != 0 && *counter <= MAX_COMMIT_COUNT) {
DeleteFfElement(&ctx->commit_data[*counter - 1]);
*counter = 0;
}
}
EpidStatus Tpm2Commit(Tpm2Ctx* ctx, EcPoint const* p1, void const* s2,
size_t s2_len, FfElement const* y2, EcPoint* k,
EcPoint* l, EcPoint* e, uint16_t* counter) {
EpidStatus sts = kEpidErr;
FiniteField* Fp = NULL;
FiniteField* Fq = NULL;
EcGroup* G1 = NULL;
FfElement* x2 = NULL;
FfElement* r = NULL;
EcPoint* point = NULL;
EcPoint* infinity = NULL;
uint16_t ctr = 0;
if (!ctx || !ctx->epid2_params || !ctx->f) {
return kEpidBadArgErr;
}
if (s2 && s2_len <= 0) {
return kEpidBadArgErr;
}
if ((!s2 && y2) || (s2 && !y2)) {
return kEpidBadArgErr;
}
if (s2 && (!k || !l)) {
return kEpidBadArgErr;
}
if (!e || !counter) {
return kEpidBadArgErr;
}
do {
G1ElemStr point_str = {0};
BigNumStr r_str = {0};
const BigNumStr kOne = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
bool is_equal = false;
Fp = ctx->epid2_params->Fp;
Fq = ctx->epid2_params->Fq;
G1 = ctx->epid2_params->G1;
sts = NewEcPoint(G1, &infinity);
BREAK_ON_EPID_ERROR(sts);
// step b
if (s2) {
// step c: compute x2 := HnameAlg(s2) mod p
sts = NewFfElement(Fq, &x2);
BREAK_ON_EPID_ERROR(sts);
sts = FfHash(Fq, s2, s2_len, ctx->hash_alg, x2);
BREAK_ON_EPID_ERROR(sts);
// step d: if (x2, y2) is not a point on the curve of signHandle, return
// TPM_RC_ECC_POINT
sts = NewEcPoint(G1, &point);
BREAK_ON_EPID_ERROR(sts);
sts = WriteFfElement(Fq, x2, &point_str.x, sizeof(point_str.x));
BREAK_ON_EPID_ERROR(sts);
sts = WriteFfElement(Fq, y2, &point_str.y, sizeof(point_str.y));
BREAK_ON_EPID_ERROR(sts);
sts = ReadEcPoint(G1, &point_str, sizeof(point_str), point);
BREAK_ON_EPID_ERROR(sts);
}
// step e: if p1 is not an Empty Point and p1 is not a point on the curve of
// signHandle, return TPM_RC_ECC_POINT
// This step is guranteed by ReadEcPoint SDK function
// step g: generate or derive r (see C.2.2)
// step h: set r = r mod n
sts = NewFfElement(Fp, &r);
BREAK_ON_EPID_ERROR(sts);
sts = FfGetRandom(Fp, &kOne, ctx->rnd_func, ctx->rnd_param, r);
BREAK_ON_EPID_ERROR(sts);
sts = InsertR(ctx, r, &ctr);
BREAK_ON_EPID_ERROR(sts);
sts = WriteFfElement(Fp, r, &r_str, sizeof(r_str));
BREAK_ON_EPID_ERROR(sts);
// step i: if s2 is not an Empty Buffer, set K = [ds](x2, y2) and L =
// [r](x2, y2)
if (s2) {
BigNumStr f_str = {0};
do {
sts = WriteFfElement(Fp, ctx->f, &f_str, sizeof(f_str));
BREAK_ON_EPID_ERROR(sts);
sts = EcExp(G1, point, &f_str, k);
BREAK_ON_EPID_ERROR(sts);
} while (0);
EpidZeroMemory(&f_str, sizeof(f_str));
BREAK_ON_EPID_ERROR(sts);
sts = EcExp(G1, point, &r_str, l);
BREAK_ON_EPID_ERROR(sts);
sts = EcIsEqual(G1, k, infinity, &is_equal);
BREAK_ON_EPID_ERROR(sts);
if (is_equal) {
sts = kEpidBadArgErr;
break;
}
sts = EcIsEqual(G1, l, infinity, &is_equal);
BREAK_ON_EPID_ERROR(sts);
if (is_equal) {
sts = kEpidBadArgErr;
break;
}
}
// step j: if p1 is not an Empty Point, set E = [r](p1 )
if (p1) {
sts = EcExp(G1, p1, &r_str, e);
BREAK_ON_EPID_ERROR(sts);
} else {
// step k: if p1 is an Empty Point and s2 is an Empty Buffer, set E = [r]G
sts = EcExp(G1, ctx->epid2_params->g1, &r_str, e);
BREAK_ON_EPID_ERROR(sts);
}
sts = EcIsEqual(G1, e, infinity, &is_equal);
BREAK_ON_EPID_ERROR(sts);
if (is_equal) {
sts = kEpidBadArgErr;
break;
}
*counter = ctr;
} while (0);
if (sts != kEpidNoErr) {
DeleteR(ctx, &ctr);
}
DeleteEcPoint(&infinity);
DeleteEcPoint(&point);
DeleteFfElement(&x2);
return sts;
}
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