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/*
* Copyright 2020, The Android Open Source Project
*
* 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 <inttypes.h>
#include "EicCommon.h"
#include "EicSession.h"
// Global used for assigning ids for session objects.
//
static uint32_t gSessionLastIdAssigned = 0;
// The current session object or NULL if never initialized or if it has been shut down.
//
static EicSession* gSessionCurrent = NULL;
EicSession* eicSessionGetForId(uint32_t sessionId) {
if (gSessionCurrent != NULL && gSessionCurrent->id == sessionId) {
return gSessionCurrent;
}
return NULL;
}
bool eicSessionInit(EicSession* ctx) {
eicMemSet(ctx, '\0', sizeof(EicSession));
if (!eicNextId(&gSessionLastIdAssigned)) {
eicDebug("Error getting id for object");
return false;
}
ctx->id = gSessionLastIdAssigned;
do {
if (!eicOpsRandom((uint8_t*)&(ctx->authChallenge), sizeof(ctx->authChallenge))) {
eicDebug("Failed generating random challenge");
return false;
}
} while (ctx->authChallenge == EIC_KM_AUTH_CHALLENGE_UNSET);
if (!eicOpsCreateEcKey(ctx->ephemeralPrivateKey, ctx->ephemeralPublicKey)) {
eicDebug("Error creating ephemeral key-pair");
return false;
}
gSessionCurrent = ctx;
eicDebug("Initialized session with id %" PRIu32, ctx->id);
return true;
}
bool eicSessionShutdown(EicSession* ctx) {
if (ctx->id == 0) {
eicDebug("Trying to shut down session with id 0");
return false;
}
eicDebug("Shut down session with id %" PRIu32, ctx->id);
eicMemSet(ctx, '\0', sizeof(EicSession));
gSessionCurrent = NULL;
return true;
}
bool eicSessionGetId(EicSession* ctx, uint32_t* outId) {
*outId = ctx->id;
return true;
}
bool eicSessionGetAuthChallenge(EicSession* ctx, uint64_t* outAuthChallenge) {
*outAuthChallenge = ctx->authChallenge;
return true;
}
bool eicSessionGetEphemeralKeyPair(EicSession* ctx,
uint8_t ephemeralPrivateKey[EIC_P256_PRIV_KEY_SIZE]) {
eicMemCpy(ephemeralPrivateKey, ctx->ephemeralPrivateKey, EIC_P256_PRIV_KEY_SIZE);
return true;
}
bool eicSessionSetReaderEphemeralPublicKey(
EicSession* ctx, const uint8_t readerEphemeralPublicKey[EIC_P256_PUB_KEY_SIZE]) {
eicMemCpy(ctx->readerEphemeralPublicKey, readerEphemeralPublicKey, EIC_P256_PUB_KEY_SIZE);
return true;
}
bool eicSessionSetSessionTranscript(EicSession* ctx, const uint8_t* sessionTranscript,
size_t sessionTranscriptSize) {
// Only accept the SessionTranscript if X and Y from the ephemeral key
// we created is somewhere in SessionTranscript...
//
if (eicMemMem(sessionTranscript, sessionTranscriptSize, ctx->ephemeralPublicKey,
EIC_P256_PUB_KEY_SIZE / 2) == NULL) {
eicDebug("Error finding X from ephemeralPublicKey in sessionTranscript");
return false;
}
if (eicMemMem(sessionTranscript, sessionTranscriptSize,
ctx->ephemeralPublicKey + EIC_P256_PUB_KEY_SIZE / 2,
EIC_P256_PUB_KEY_SIZE / 2) == NULL) {
eicDebug("Error finding Y from ephemeralPublicKey in sessionTranscript");
return false;
}
// To save space we only store the SHA-256 of SessionTranscript
//
EicSha256Ctx shaCtx;
eicOpsSha256Init(&shaCtx);
eicOpsSha256Update(&shaCtx, sessionTranscript, sessionTranscriptSize);
eicOpsSha256Final(&shaCtx, ctx->sessionTranscriptSha256);
return true;
}
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