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128 lines
4.3 KiB
128 lines
4.3 KiB
/*
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* Copyright (C) 2017 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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//#define LOG_NDEBUG 0
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#define LOG_TAG "ClearKeyFetcher"
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#include <algorithm>
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#include <inttypes.h>
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#include <string>
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#include "ClearKeyFetcher.h"
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#include "ecm.h"
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#include "LicenseFetcher.h"
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#include <media/stagefright/foundation/ADebug.h>
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#include <utils/Log.h>
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namespace android {
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namespace clearkeycas {
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ClearKeyFetcher::ClearKeyFetcher(
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std::unique_ptr<LicenseFetcher> license_fetcher) :
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initialized_(false),
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license_fetcher_(std::move(license_fetcher)) {
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CHECK(license_fetcher_);
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}
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ClearKeyFetcher::~ClearKeyFetcher() {}
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// This is a no-op but other KeyFetcher subclasses require initialization
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// so this is necessary to preserve the contract.
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status_t ClearKeyFetcher::Init() {
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initialized_ = true;
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return OK;
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}
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status_t ClearKeyFetcher::ObtainKey(const sp<ABuffer>& buffer,
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uint64_t* asset_id, std::vector<KeyInfo>* keys) {
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CHECK(asset_id);
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CHECK(keys);
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CHECK(initialized_);
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*asset_id = 0;
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keys->clear();
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EcmContainer container;
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status_t status = container.Parse(buffer);
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if (status != OK) {
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return status;
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}
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ALOGV("descriptor_size=%zu", container.descriptor_size());
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// Validate that the BroadcastEncryptor is sending a properly formed
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// EcmContainer. If it contains two Ecms, the ids should have different
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// parity (one odd, one even). This does not necessarily affect decryption
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// but indicates a problem with Ecm generation.
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if (container.descriptor_size() == 2) {
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// XOR the least significant bits to verify different parity.
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bool same_parity = (((container.descriptor(0).id() & 0x01) ^
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(container.descriptor(1).id() & 0x01)) == 0);
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if (same_parity) {
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ALOGW("asset_id=%" PRIu64 ": malformed Ecm, "
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"content keys have same parity, id0=%d, id1=%d",
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container.descriptor(0).ecm().asset_id(),
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container.descriptor(0).id(),
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container.descriptor(1).id());
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}
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}
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*asset_id = container.descriptor(0).ecm().asset_id();
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// Detect asset_id change. This could be caused by a configuration change
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// in the BroadcastEncryptor. This is unusual so log it in case it is an
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// operational mistake. This invalidates the current asset_key causing a
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// new license to be fetched.
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// TODO(rkint): test against BroadcastEncryptor to verify what BE sends on
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// asset_id change. If it sends an EcmContainer with 2 Ecms with different
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// asset_ids (old and new) then it might be best to prefetch the Emm.
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if ((asset_.id() != 0) && (*asset_id != asset_.id())) {
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ALOGW("Asset_id change from %" PRIu64 " to %" PRIu64, asset_.id(), *asset_id);
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asset_.Clear();
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}
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// Fetch license to get asset_id
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if (!asset_.has_id()) {
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status = license_fetcher_->FetchLicense(*asset_id, &asset_);
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if (status != OK) {
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*asset_id = 0;
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return status;
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}
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ALOGV("FetchLicense succeeded, has_id=%d", asset_.has_id());
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}
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keys->resize(container.descriptor_size());
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for (size_t i = 0; i < container.descriptor_size(); ++i) {
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status = container.mutable_descriptor(i)->mutable_ecm()->Decrypt(
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container.descriptor(i).ecm().buffer(), asset_);
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if (status != OK) {
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*asset_id = 0;
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keys->clear();
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return status;
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}
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// TODO: if 2 Ecms have same parity, key from Ecm with higher id
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// should be keys[1].
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KeyInfo key;
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key.key_id = container.descriptor(i).id();
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key.key_bytes = container.descriptor(i).ecm().content_key();
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keys->at(key.key_id & 1) = key;
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}
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return OK;
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}
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} // namespace clearkeycas
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} // namespace android
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