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