308 lines
11 KiB
C++
308 lines
11 KiB
C++
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/*
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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 "liblp/reader.h"
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#include <stddef.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <functional>
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#include <android-base/file.h>
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#include <android-base/unique_fd.h>
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#include "utility.h"
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namespace android {
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namespace fs_mgr {
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// Parse an LpMetadataGeometry from a buffer. The buffer must be at least
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// LP_METADATA_GEOMETRY_SIZE bytes in size.
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static bool ParseGeometry(const void* buffer, LpMetadataGeometry* geometry) {
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static_assert(sizeof(*geometry) <= LP_METADATA_GEOMETRY_SIZE);
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memcpy(geometry, buffer, sizeof(*geometry));
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// Check the magic signature.
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if (geometry->magic != LP_METADATA_GEOMETRY_MAGIC) {
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LERROR << "Logical partition metadata has invalid geometry magic signature.";
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return false;
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}
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// Recompute and check the CRC32.
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{
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LpMetadataGeometry temp = *geometry;
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memset(&temp.checksum, 0, sizeof(temp.checksum));
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SHA256(&temp, sizeof(temp), temp.checksum);
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if (memcmp(temp.checksum, geometry->checksum, sizeof(temp.checksum)) != 0) {
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LERROR << "Logical partition metadata has invalid geometry checksum.";
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return false;
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}
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}
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// Check that the struct size is equal (this will have to change if we ever
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// change the struct size in a release).
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if (geometry->struct_size != sizeof(LpMetadataGeometry)) {
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LERROR << "Logical partition metadata has invalid struct size.";
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return false;
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}
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if (geometry->metadata_slot_count == 0) {
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LERROR << "Logical partition metadata has invalid slot count.";
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return false;
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}
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// Check that the metadata area and logical partition areas don't overlap.
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int64_t end_of_metadata =
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GetPrimaryMetadataOffset(*geometry, geometry->metadata_slot_count - 1) +
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geometry->metadata_max_size;
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if (uint64_t(end_of_metadata) > geometry->first_logical_sector * LP_SECTOR_SIZE) {
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LERROR << "Logical partition metadata overlaps with logical partition contents.";
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return false;
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}
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return true;
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}
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// Read and validate geometry information from a block device that holds
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// logical partitions. If the information is corrupted, this will attempt
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// to read it from a secondary backup location.
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static bool ReadLogicalPartitionGeometry(int fd, LpMetadataGeometry* geometry) {
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// Read the first 4096 bytes.
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std::unique_ptr<uint8_t[]> buffer = std::make_unique<uint8_t[]>(LP_METADATA_GEOMETRY_SIZE);
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if (SeekFile64(fd, 0, SEEK_SET) < 0) {
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PERROR << __PRETTY_FUNCTION__ << "lseek failed";
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return false;
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}
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if (!android::base::ReadFully(fd, buffer.get(), LP_METADATA_GEOMETRY_SIZE)) {
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PERROR << __PRETTY_FUNCTION__ << "read " << LP_METADATA_GEOMETRY_SIZE << " bytes failed";
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return false;
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}
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if (ParseGeometry(buffer.get(), geometry)) {
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return true;
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}
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// Try the backup copy in the last 4096 bytes.
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if (SeekFile64(fd, -LP_METADATA_GEOMETRY_SIZE, SEEK_END) < 0) {
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PERROR << __PRETTY_FUNCTION__ << "lseek failed, offset " << -LP_METADATA_GEOMETRY_SIZE;
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return false;
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}
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if (!android::base::ReadFully(fd, buffer.get(), LP_METADATA_GEOMETRY_SIZE)) {
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PERROR << __PRETTY_FUNCTION__ << "backup read " << LP_METADATA_GEOMETRY_SIZE
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<< " bytes failed";
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return false;
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}
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return ParseGeometry(buffer.get(), geometry);
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}
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// Helper function to read geometry from a device without an open descriptor.
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bool ReadLogicalPartitionGeometry(const char* block_device, LpMetadataGeometry* geometry) {
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android::base::unique_fd fd(open(block_device, O_RDONLY));
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if (fd < 0) {
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PERROR << __PRETTY_FUNCTION__ << "open failed: " << block_device;
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return false;
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}
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return ReadLogicalPartitionGeometry(fd, geometry);
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}
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static bool ValidateTableBounds(const LpMetadataHeader& header,
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const LpMetadataTableDescriptor& table) {
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if (table.offset > header.tables_size) {
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return false;
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}
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uint64_t table_size = uint64_t(table.num_entries) * table.entry_size;
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if (header.tables_size - table.offset < table_size) {
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return false;
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}
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return true;
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}
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static bool ValidateMetadataHeader(const LpMetadataHeader& header) {
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// To compute the header's checksum, we have to temporarily set its checksum
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// field to 0.
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{
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LpMetadataHeader temp = header;
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memset(&temp.header_checksum, 0, sizeof(temp.header_checksum));
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SHA256(&temp, sizeof(temp), temp.header_checksum);
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if (memcmp(temp.header_checksum, header.header_checksum, sizeof(temp.header_checksum)) != 0) {
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LERROR << "Logical partition metadata has invalid checksum.";
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return false;
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}
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}
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// Do basic validation of key metadata bits.
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if (header.magic != LP_METADATA_HEADER_MAGIC) {
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LERROR << "Logical partition metadata has invalid magic value.";
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return false;
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}
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// Check that the version is compatible.
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if (header.major_version != LP_METADATA_MAJOR_VERSION ||
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header.minor_version > LP_METADATA_MINOR_VERSION) {
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LERROR << "Logical partition metadata has incompatible version.";
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return false;
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}
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if (!ValidateTableBounds(header, header.partitions) ||
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!ValidateTableBounds(header, header.extents)) {
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LERROR << "Logical partition metadata has invalid table bounds.";
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return false;
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}
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// Check that table entry sizes can accomodate their respective structs. If
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// table sizes change, these checks will have to be adjusted.
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if (header.partitions.entry_size != sizeof(LpMetadataPartition)) {
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LERROR << "Logical partition metadata has invalid partition table entry size.";
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return false;
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}
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if (header.extents.entry_size != sizeof(LpMetadataExtent)) {
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LERROR << "Logical partition metadata has invalid extent table entry size.";
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return false;
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}
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return true;
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}
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using ReadMetadataFn = std::function<bool(void* buffer, size_t num_bytes)>;
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// Parse and validate all metadata at the current position in the given file
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// descriptor.
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static std::unique_ptr<LpMetadata> ParseMetadata(int fd) {
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// First read and validate the header.
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std::unique_ptr<LpMetadata> metadata = std::make_unique<LpMetadata>();
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if (!android::base::ReadFully(fd, &metadata->header, sizeof(metadata->header))) {
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PERROR << __PRETTY_FUNCTION__ << "read " << sizeof(metadata->header) << "bytes failed";
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return nullptr;
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}
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if (!ValidateMetadataHeader(metadata->header)) {
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return nullptr;
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}
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LpMetadataHeader& header = metadata->header;
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// Read the metadata payload. Allocation is fallible in case the metadata is
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// corrupt and has some huge value.
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std::unique_ptr<uint8_t[]> buffer(new (std::nothrow) uint8_t[header.tables_size]);
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if (!buffer) {
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LERROR << "Out of memory reading logical partition tables.";
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return nullptr;
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}
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if (!android::base::ReadFully(fd, buffer.get(), header.tables_size)) {
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PERROR << __PRETTY_FUNCTION__ << "read " << header.tables_size << "bytes failed";
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return nullptr;
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}
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uint8_t checksum[32];
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SHA256(buffer.get(), header.tables_size, checksum);
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if (memcmp(checksum, header.tables_checksum, sizeof(checksum)) != 0) {
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LERROR << "Logical partition metadata has invalid table checksum.";
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return nullptr;
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}
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// ValidateTableSize ensured that |cursor| is valid for the number of
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// entries in the table.
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uint8_t* cursor = buffer.get() + header.partitions.offset;
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for (size_t i = 0; i < header.partitions.num_entries; i++) {
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LpMetadataPartition partition;
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memcpy(&partition, cursor, sizeof(partition));
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cursor += header.partitions.entry_size;
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if (partition.attributes & ~LP_PARTITION_ATTRIBUTE_MASK) {
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LERROR << "Logical partition has invalid attribute set.";
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return nullptr;
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}
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if (partition.first_extent_index + partition.num_extents > header.extents.num_entries) {
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LERROR << "Logical partition has invalid extent list.";
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return nullptr;
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}
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metadata->partitions.push_back(partition);
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}
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cursor = buffer.get() + header.extents.offset;
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for (size_t i = 0; i < header.extents.num_entries; i++) {
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LpMetadataExtent extent;
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memcpy(&extent, cursor, sizeof(extent));
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cursor += header.extents.entry_size;
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metadata->extents.push_back(extent);
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}
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return metadata;
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}
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std::unique_ptr<LpMetadata> ReadMetadata(const char* block_device, uint32_t slot_number) {
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android::base::unique_fd fd(open(block_device, O_RDONLY));
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if (fd < 0) {
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PERROR << __PRETTY_FUNCTION__ << "open failed: " << block_device;
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return nullptr;
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}
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LpMetadataGeometry geometry;
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if (!ReadLogicalPartitionGeometry(fd, &geometry)) {
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return nullptr;
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}
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// First try the primary copy.
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int64_t offset = GetPrimaryMetadataOffset(geometry, slot_number);
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if (SeekFile64(fd, offset, SEEK_SET) < 0) {
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PERROR << __PRETTY_FUNCTION__ << "lseek failed: offset " << offset;
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return nullptr;
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}
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if (std::unique_ptr<LpMetadata> metadata = ParseMetadata(fd)) {
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return metadata;
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}
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// Next try the backup copy.
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offset = GetBackupMetadataOffset(geometry, slot_number);
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if (SeekFile64(fd, offset, SEEK_END) < 0) {
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PERROR << __PRETTY_FUNCTION__ << "lseek failed: offset " << offset;
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return nullptr;
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}
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return ParseMetadata(fd);
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}
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std::unique_ptr<LpMetadata> ReadFromImageFile(const char* file) {
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android::base::unique_fd fd(open(file, O_RDONLY));
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if (fd < 0) {
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PERROR << __PRETTY_FUNCTION__ << "open failed: " << file;
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return nullptr;
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}
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LpMetadataGeometry geometry;
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if (!ReadLogicalPartitionGeometry(fd, &geometry)) {
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return nullptr;
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}
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if (SeekFile64(fd, LP_METADATA_GEOMETRY_SIZE, SEEK_SET) < 0) {
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PERROR << __PRETTY_FUNCTION__ << "lseek failed: offset " << LP_METADATA_GEOMETRY_SIZE;
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return nullptr;
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}
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std::unique_ptr<LpMetadata> metadata = ParseMetadata(fd);
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if (!metadata) {
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return nullptr;
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}
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metadata->geometry = geometry;
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return metadata;
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}
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static std::string NameFromFixedArray(const char* name, size_t buffer_size) {
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// If the end of the buffer has a null character, it's safe to assume the
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// buffer is null terminated. Otherwise, we cap the string to the input
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// buffer size.
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if (name[buffer_size - 1] == '\0') {
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return std::string(name);
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}
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return std::string(name, buffer_size);
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}
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std::string GetPartitionName(const LpMetadataPartition& partition) {
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return NameFromFixedArray(partition.name, sizeof(partition.name));
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}
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} // namespace fs_mgr
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} // namespace android
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