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/*
* Copyright (C) 2016 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.
*/
#define LOG_TAG "hwservicemanager"
#include "TokenManager.h"
#include <fcntl.h>
#include <hwbinder/IPCThreadState.h>
#include <log/log.h>
#include <openssl/hmac.h>
#include <openssl/rand.h>
#include <functional>
namespace android {
namespace hidl {
namespace token {
namespace V1_0 {
namespace implementation {
static void ReadRandomBytes(uint8_t *buf, size_t len) {
int fd = TEMP_FAILURE_RETRY(open("/dev/urandom", O_RDONLY | O_CLOEXEC | O_NOFOLLOW));
if (fd == -1) {
ALOGE("%s: cannot read /dev/urandom", __func__);
return;
}
size_t n;
while ((n = TEMP_FAILURE_RETRY(read(fd, buf, len))) > 0) {
len -= n;
buf += n;
}
if (len > 0) {
ALOGW("%s: there are %d bytes skipped", __func__, (int)len);
}
close(fd);
}
TokenManager::TokenManager() {
ReadRandomBytes(mKey.data(), mKey.size());
}
static void noteTmUsage(const char* action, size_t size) {
using android::hardware::IPCThreadState;
const auto& self = IPCThreadState::self();
ALOGI("TokenManager tokens count %s by (uid: %d, pid: %d), now: %zu", action,
self->getCallingUid(), self->getCallingPid(), size);
}
// Methods from ::android::hidl::token::V1_0::ITokenManager follow.
Return<void> TokenManager::createToken(const sp<IBase>& store, createToken_cb hidl_cb) {
TokenInterface interface = generateToken(store);
if (interface.interface == nullptr) {
hidl_cb({});
return Void();
}
uint64_t id = getTokenId(interface.token);
if (id != interface.id) {
ALOGE("Token creation failed.");
hidl_cb({});
return Void();
}
if (id == TOKEN_ID_NONE) {
hidl_cb({});
return Void();
}
mMap[id] = interface;
noteTmUsage("added", mMap.size());
hidl_cb(interface.token);
return Void();
}
std::unordered_map<uint64_t, TokenManager::TokenInterface>::const_iterator
TokenManager::lookupToken(const hidl_vec<uint8_t> &token) {
uint64_t tokenId = getTokenId(token);
if (tokenId == TOKEN_ID_NONE) {
return mMap.end();
}
auto it = mMap.find(tokenId);
if (it == mMap.end()) {
return mMap.end();
}
const TokenInterface &interface = it->second;
if (!constantTimeCompare(token, interface.token)) {
ALOGE("Fetch of token with invalid hash.");
return mMap.end();
}
return it;
}
Return<bool> TokenManager::unregister(const hidl_vec<uint8_t> &token) {
auto it = lookupToken(token);
if (it == mMap.end()) {
return false;
}
mMap.erase(it);
noteTmUsage("removed", mMap.size());
return true;
}
Return<sp<IBase>> TokenManager::get(const hidl_vec<uint8_t> &token) {
auto it = lookupToken(token);
if (it == mMap.end()) {
return nullptr;
}
return it->second.interface;
}
TokenManager::TokenInterface TokenManager::generateToken(const sp<IBase> &interface) {
uint64_t id = ++mTokenIndex;
std::array<uint8_t, EVP_MAX_MD_SIZE> hmac;
uint32_t hmacSize;
uint8_t *hmacOut = HMAC(EVP_sha256(),
mKey.data(), mKey.size(),
(uint8_t*) &id, sizeof(id),
hmac.data(), &hmacSize);
if (hmacOut == nullptr ||
hmacOut != hmac.data()) {
ALOGE("Generating token failed, got %p.", hmacOut);
return { nullptr, TOKEN_ID_NONE, {} };
}
// only care about the first HMAC_SIZE bytes of the HMAC
const hidl_vec<uint8_t> &token = makeToken(id, hmac.data(), hmacSize);
return { interface, id, token };
}
__attribute__((optnone))
bool TokenManager::constantTimeCompare(const hidl_vec<uint8_t> &t1, const hidl_vec<uint8_t> &t2) {
if (t1.size() != t2.size()) {
return false;
}
uint8_t x = 0;
for (size_t i = 0; i < t1.size(); i++) {
x |= t1[i] ^ t2[i];
}
return x == 0;
}
uint64_t TokenManager::getTokenId(const hidl_vec<uint8_t> &token) {
uint64_t id = 0;
if (token.size() < sizeof(id)) {
return TOKEN_ID_NONE;
}
memcpy(&id, token.data(), sizeof(id));
return id;
}
hidl_vec<uint8_t> TokenManager::makeToken(const uint64_t id, const uint8_t *hmac, uint64_t hmacSize) {
hidl_vec<uint8_t> token;
token.resize(sizeof(id) + hmacSize);
memcpy(token.data(), &id, sizeof(id));
memcpy(token.data() + sizeof(id), hmac, hmacSize);
return token;
}
} // namespace implementation
} // namespace V1_0
} // namespace token
} // namespace hidl
} // namespace android
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