1 /*
2 * Copyright (C) 2021 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "install/spl_check.h"
18
ViolatesSPLDowngrade(const build::tools::releasetools::OtaMetadata & metadata,std::string_view current_spl)19 bool ViolatesSPLDowngrade(const build::tools::releasetools::OtaMetadata& metadata,
20 std::string_view current_spl) {
21 const auto& post_spl = metadata.postcondition().security_patch_level();
22 if (current_spl.empty()) {
23 LOG(WARNING) << "Failed to get device's current security patch level. Target SPL is "
24 << post_spl << " permitting OTA install";
25 return false;
26 }
27 // SPL(security patch level) is expected to be in format yyyy-mm-dd, e.g. 2018-05-29. Given this
28 // specific format, comparing two SPL can be done by just regular string comparison. If the format
29 // must lay out year/month/date in the exact order, and must properly prepend dates with 0(for
30 // example, 05 for May). Otherwise this comparison doesn't work. We don't expect SPL date formats
31 // to change, leave this as is.
32 if (post_spl < current_spl) {
33 LOG(ERROR) << "Current SPL: " << current_spl << " Target SPL: " << post_spl
34 << " this is considered a downgrade";
35 if (metadata.spl_downgrade() || metadata.downgrade()) {
36 LOG(WARNING)
37 << "SPL downgrade detected, but OTA package explicitly permitts this(OtaMetadata has "
38 "spl_downgrade / downgrade bit set).Permitting update anyway.Installing a SPL "
39 "downgrade OTA can cause /data fail to decrypt and device fails to boot.";
40 return false;
41 }
42 return true;
43 } else {
44 LOG(INFO) << "old spl: " << current_spl << " new spl: " << post_spl << " CHECK passes";
45 }
46 return false;
47 }
48
ViolatesSPLDowngrade(ZipArchiveHandle zip,std::string_view current_spl)49 bool ViolatesSPLDowngrade(ZipArchiveHandle zip, std::string_view current_spl) {
50 static constexpr auto&& OTA_OTA_METADATA = "META-INF/com/android/metadata.pb";
51 ZipEntry64 metadata_entry;
52 if (FindEntry(zip, OTA_OTA_METADATA, &metadata_entry) != 0) {
53 LOG(WARNING) << "Failed to find " << OTA_OTA_METADATA
54 << " treating this as non-spl-downgrade, permit OTA install. If device bricks "
55 "after installing, check kernel log to see if /data failed to decrypt";
56 return false;
57 }
58 const auto metadata_entry_length = metadata_entry.uncompressed_length;
59 if (metadata_entry_length > std::numeric_limits<size_t>::max()) {
60 LOG(ERROR) << "Failed to extract " << OTA_OTA_METADATA
61 << " because's uncompressed size exceeds size of address space. "
62 << metadata_entry_length;
63 return false;
64 }
65 std::vector<uint8_t> ota_metadata(metadata_entry_length);
66 int32_t err = ExtractToMemory(zip, &metadata_entry, ota_metadata.data(), metadata_entry_length);
67 if (err != 0) {
68 LOG(ERROR) << "Failed to extract " << OTA_OTA_METADATA << ": " << ErrorCodeString(err);
69 return false;
70 }
71 using build::tools::releasetools::OtaMetadata;
72 OtaMetadata metadata;
73 if (!metadata.ParseFromArray(ota_metadata.data(), ota_metadata.size())) {
74 LOG(ERROR) << "Failed to parse ota_medata";
75 return false;
76 }
77 return ViolatesSPLDowngrade(metadata, current_spl);
78 }
79