//
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// Copyright (C) 2018 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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#include "update_engine/payload_consumer/verity_writer_android.h"
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#include <fcntl.h>
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#include <algorithm>
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#include <memory>
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#include <base/logging.h>
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#include <base/posix/eintr_wrapper.h>
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#include <fec/ecc.h>
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extern "C" {
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#include <fec.h>
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}
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#include "update_engine/common/utils.h"
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namespace chromeos_update_engine {
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namespace verity_writer {
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std::unique_ptr<VerityWriterInterface> CreateVerityWriter() {
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return std::make_unique<VerityWriterAndroid>();
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}
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} // namespace verity_writer
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bool VerityWriterAndroid::Init(const InstallPlan::Partition& partition) {
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partition_ = &partition;
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if (partition_->hash_tree_size != 0 || partition_->fec_size != 0) {
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utils::SetBlockDeviceReadOnly(partition_->target_path, false);
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}
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if (partition_->hash_tree_size != 0) {
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auto hash_function =
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HashTreeBuilder::HashFunction(partition_->hash_tree_algorithm);
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if (hash_function == nullptr) {
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LOG(ERROR) << "Verity hash algorithm not supported: "
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<< partition_->hash_tree_algorithm;
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return false;
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}
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hash_tree_builder_ = std::make_unique<HashTreeBuilder>(
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partition_->block_size, hash_function);
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TEST_AND_RETURN_FALSE(hash_tree_builder_->Initialize(
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partition_->hash_tree_data_size, partition_->hash_tree_salt));
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if (hash_tree_builder_->CalculateSize(partition_->hash_tree_data_size) !=
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partition_->hash_tree_size) {
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LOG(ERROR) << "Verity hash tree size does not match, stored: "
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<< partition_->hash_tree_size << ", calculated: "
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<< hash_tree_builder_->CalculateSize(
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partition_->hash_tree_data_size);
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return false;
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}
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}
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return true;
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}
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bool VerityWriterAndroid::Update(uint64_t offset,
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const uint8_t* buffer,
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size_t size) {
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if (partition_->hash_tree_size != 0) {
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uint64_t hash_tree_data_end =
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partition_->hash_tree_data_offset + partition_->hash_tree_data_size;
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uint64_t start_offset = std::max(offset, partition_->hash_tree_data_offset);
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uint64_t end_offset = std::min(offset + size, hash_tree_data_end);
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if (start_offset < end_offset) {
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TEST_AND_RETURN_FALSE(hash_tree_builder_->Update(
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buffer + start_offset - offset, end_offset - start_offset));
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if (end_offset == hash_tree_data_end) {
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// All hash tree data blocks has been hashed, write hash tree to disk.
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int fd = HANDLE_EINTR(open(partition_->target_path.c_str(), O_WRONLY));
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if (fd < 0) {
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PLOG(ERROR) << "Failed to open " << partition_->target_path
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<< " to write hash tree.";
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return false;
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}
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ScopedFdCloser fd_closer(&fd);
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LOG(INFO) << "Writing verity hash tree to " << partition_->target_path;
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TEST_AND_RETURN_FALSE(hash_tree_builder_->BuildHashTree());
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TEST_AND_RETURN_FALSE(hash_tree_builder_->WriteHashTreeToFd(
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fd, partition_->hash_tree_offset));
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hash_tree_builder_.reset();
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}
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}
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}
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if (partition_->fec_size != 0) {
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uint64_t fec_data_end =
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partition_->fec_data_offset + partition_->fec_data_size;
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if (offset < fec_data_end && offset + size >= fec_data_end) {
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LOG(INFO) << "Writing verity FEC to " << partition_->target_path;
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TEST_AND_RETURN_FALSE(EncodeFEC(partition_->target_path,
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partition_->fec_data_offset,
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partition_->fec_data_size,
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partition_->fec_offset,
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partition_->fec_size,
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partition_->fec_roots,
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partition_->block_size,
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false /* verify_mode */));
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}
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}
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return true;
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}
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bool VerityWriterAndroid::EncodeFEC(const std::string& path,
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uint64_t data_offset,
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uint64_t data_size,
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uint64_t fec_offset,
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uint64_t fec_size,
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uint32_t fec_roots,
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uint32_t block_size,
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bool verify_mode) {
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TEST_AND_RETURN_FALSE(data_size % block_size == 0);
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TEST_AND_RETURN_FALSE(fec_roots >= 0 && fec_roots < FEC_RSM);
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// This is the N in RS(M, N), which is the number of bytes for each rs block.
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size_t rs_n = FEC_RSM - fec_roots;
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uint64_t rounds = utils::DivRoundUp(data_size / block_size, rs_n);
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TEST_AND_RETURN_FALSE(rounds * fec_roots * block_size == fec_size);
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std::unique_ptr<void, decltype(&free_rs_char)> rs_char(
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init_rs_char(FEC_PARAMS(fec_roots)), &free_rs_char);
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TEST_AND_RETURN_FALSE(rs_char != nullptr);
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int fd = HANDLE_EINTR(open(path.c_str(), verify_mode ? O_RDONLY : O_RDWR));
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if (fd < 0) {
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PLOG(ERROR) << "Failed to open " << path << " to write FEC.";
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return false;
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}
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ScopedFdCloser fd_closer(&fd);
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for (size_t i = 0; i < rounds; i++) {
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// Encodes |block_size| number of rs blocks each round so that we can read
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// one block each time instead of 1 byte to increase random read
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// performance. This uses about 1 MiB memory for 4K block size.
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brillo::Blob rs_blocks(block_size * rs_n);
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for (size_t j = 0; j < rs_n; j++) {
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brillo::Blob buffer(block_size, 0);
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uint64_t offset =
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fec_ecc_interleave(i * rs_n * block_size + j, rs_n, rounds);
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// Don't read past |data_size|, treat them as 0.
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if (offset < data_size) {
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ssize_t bytes_read = 0;
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TEST_AND_RETURN_FALSE(utils::PReadAll(fd,
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buffer.data(),
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buffer.size(),
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data_offset + offset,
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&bytes_read));
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TEST_AND_RETURN_FALSE(bytes_read ==
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static_cast<ssize_t>(buffer.size()));
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}
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for (size_t k = 0; k < buffer.size(); k++) {
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rs_blocks[k * rs_n + j] = buffer[k];
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}
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}
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brillo::Blob fec(block_size * fec_roots);
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for (size_t j = 0; j < block_size; j++) {
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// Encode [j * rs_n : (j + 1) * rs_n) in |rs_blocks| and write |fec_roots|
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// number of parity bytes to |j * fec_roots| in |fec|.
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encode_rs_char(rs_char.get(),
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rs_blocks.data() + j * rs_n,
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fec.data() + j * fec_roots);
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}
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if (verify_mode) {
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brillo::Blob fec_read(fec.size());
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ssize_t bytes_read = 0;
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TEST_AND_RETURN_FALSE(utils::PReadAll(
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fd, fec_read.data(), fec_read.size(), fec_offset, &bytes_read));
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TEST_AND_RETURN_FALSE(bytes_read ==
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static_cast<ssize_t>(fec_read.size()));
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TEST_AND_RETURN_FALSE(fec == fec_read);
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} else {
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TEST_AND_RETURN_FALSE(
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utils::PWriteAll(fd, fec.data(), fec.size(), fec_offset));
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}
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fec_offset += fec.size();
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}
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return true;
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}
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} // namespace chromeos_update_engine
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