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/*
* Copyright (C) 2021 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.
*/
#include "install/spl_check.h"
bool ViolatesSPLDowngrade(const build::tools::releasetools::OtaMetadata& metadata,
std::string_view current_spl) {
const auto& post_spl = metadata.postcondition().security_patch_level();
if (current_spl.empty()) {
LOG(WARNING) << "Failed to get device's current security patch level. Target SPL is "
<< post_spl << " permitting OTA install";
return false;
}
// SPL(security patch level) is expected to be in format yyyy-mm-dd, e.g. 2018-05-29. Given this
// specific format, comparing two SPL can be done by just regular string comparison. If the format
// must lay out year/month/date in the exact order, and must properly prepend dates with 0(for
// example, 05 for May). Otherwise this comparison doesn't work. We don't expect SPL date formats
// to change, leave this as is.
if (post_spl < current_spl) {
LOG(ERROR) << "Current SPL: " << current_spl << " Target SPL: " << post_spl
<< " this is considered a downgrade";
if (metadata.spl_downgrade() || metadata.downgrade()) {
LOG(WARNING)
<< "SPL downgrade detected, but OTA package explicitly permitts this(OtaMetadata has "
"spl_downgrade / downgrade bit set).Permitting update anyway.Installing a SPL "
"downgrade OTA can cause /data fail to decrypt and device fails to boot.";
return false;
}
return true;
} else {
LOG(INFO) << "old spl: " << current_spl << " new spl: " << post_spl << " CHECK passes";
}
return false;
}
bool ViolatesSPLDowngrade(ZipArchiveHandle zip, std::string_view current_spl) {
static constexpr auto&& OTA_OTA_METADATA = "META-INF/com/android/metadata.pb";
ZipEntry64 metadata_entry;
if (FindEntry(zip, OTA_OTA_METADATA, &metadata_entry) != 0) {
LOG(WARNING) << "Failed to find " << OTA_OTA_METADATA
<< " treating this as non-spl-downgrade, permit OTA install. If device bricks "
"after installing, check kernel log to see if /data failed to decrypt";
return false;
}
const auto metadata_entry_length = metadata_entry.uncompressed_length;
if (metadata_entry_length > std::numeric_limits<size_t>::max()) {
LOG(ERROR) << "Failed to extract " << OTA_OTA_METADATA
<< " because's uncompressed size exceeds size of address space. "
<< metadata_entry_length;
return false;
}
std::vector<uint8_t> ota_metadata(metadata_entry_length);
int32_t err = ExtractToMemory(zip, &metadata_entry, ota_metadata.data(), metadata_entry_length);
if (err != 0) {
LOG(ERROR) << "Failed to extract " << OTA_OTA_METADATA << ": " << ErrorCodeString(err);
return false;
}
using build::tools::releasetools::OtaMetadata;
OtaMetadata metadata;
if (!metadata.ParseFromArray(ota_metadata.data(), ota_metadata.size())) {
LOG(ERROR) << "Failed to parse ota_medata";
return false;
}
return ViolatesSPLDowngrade(metadata, current_spl);
}
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