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https://fuchsia.googlesource.com/third_party/pigweed.googlesource.com/pigweed/pigweed
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38cfa98998
- Always pad entries to their alignment instead of the flash's alignment, which may be smaller. - Checksum entire entries, including padding. The checksum is calculated with the checksum field set to 0. Change-Id: Ie354bf3fb93f23354d2278e5b16bd7d448728d95
140 lines
4.4 KiB
C++
140 lines
4.4 KiB
C++
// Copyright 2020 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://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, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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#include "pw_kvs_private/format.h"
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#include <cinttypes>
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#include "pw_kvs_private/macros.h"
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#include "pw_log/log.h"
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namespace pw::kvs {
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using std::byte;
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using std::string_view;
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Entry::Entry(uint32_t magic,
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ChecksumAlgorithm* algorithm,
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string_view key,
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span<const byte> value,
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uint16_t value_length_bytes,
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size_t alignment_bytes,
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uint32_t key_version)
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: header_{.magic = magic,
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.checksum = 0,
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.alignment_units = alignment_bytes_to_units(alignment_bytes),
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.key_length_bytes = static_cast<uint8_t>(key.size()),
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.value_length_bytes = value_length_bytes,
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.key_version = key_version} {
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if (algorithm != nullptr) {
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span<const byte> checksum = CalculateChecksum(algorithm, key, value);
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std::memcpy(&header_.checksum,
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checksum.data(),
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std::min(checksum.size(), sizeof(header_.checksum)));
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}
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// TODO: 0 is an invalid alignment value. There should be an assert for this.
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// DCHECK_NE(alignment_bytes, 0);
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}
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Status Entry::VerifyChecksum(ChecksumAlgorithm* algorithm,
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string_view key,
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span<const byte> value) const {
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if (algorithm == nullptr) {
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return checksum() == 0 ? Status::OK : Status::DATA_LOSS;
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}
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CalculateChecksum(algorithm, key, value);
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return algorithm->Verify(checksum_bytes());
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}
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Status Entry::VerifyChecksumInFlash(FlashPartition* partition,
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FlashPartition::Address address,
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ChecksumAlgorithm* algorithm) const {
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// Read the entire entry piece-by-piece into a small buffer. If the entry is
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// 32 B or less, only one read is required.
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union {
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EntryHeader header_to_verify;
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byte buffer[sizeof(EntryHeader) * 2];
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};
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size_t bytes_to_read = size();
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size_t read_size = std::min(sizeof(buffer), bytes_to_read);
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// Read the first chunk, which includes the header, and compare the checksum.
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TRY(partition->Read(address, read_size, buffer));
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if (header_to_verify.checksum != checksum()) {
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PW_LOG_ERROR("Expected checksum %08" PRIx32 ", found %08" PRIx32,
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checksum(),
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header_to_verify.checksum);
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return Status::DATA_LOSS;
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}
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if (algorithm == nullptr) {
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return Status::OK;
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}
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// The checksum is calculated as if the header's checksum field were 0.
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header_to_verify.checksum = 0;
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algorithm->Reset();
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while (true) {
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// Add the chunk in the buffer to the checksum.
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algorithm->Update(buffer, read_size);
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bytes_to_read -= read_size;
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if (bytes_to_read == 0u) {
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break;
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}
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// Read the next chunk into the buffer.
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address += read_size;
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read_size = std::min(sizeof(buffer), bytes_to_read);
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TRY(partition->Read(address, read_size, buffer));
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}
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algorithm->Finish();
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return algorithm->Verify(checksum_bytes());
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}
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span<const byte> Entry::CalculateChecksum(ChecksumAlgorithm* algorithm,
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const string_view key,
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span<const byte> value) const {
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algorithm->Reset();
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{
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EntryHeader header_for_checksum = header_;
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header_for_checksum.checksum = 0;
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algorithm->Update(&header_for_checksum, sizeof(header_for_checksum));
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algorithm->Update(as_bytes(span(key)));
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algorithm->Update(value);
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}
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// Update the checksum with 0s to pad the entry to its alignment boundary.
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constexpr byte padding[kMinAlignmentBytes - 1] = {};
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size_t padding_to_add = Padding(content_size(), alignment_bytes());
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while (padding_to_add > 0u) {
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const size_t chunk_size = std::min(padding_to_add, sizeof(padding));
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algorithm->Update(padding, chunk_size);
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padding_to_add -= chunk_size;
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}
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return algorithm->Finish();
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}
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} // namespace pw::kvs
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