/*
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* Copyright (C) 2016 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 "fs_avb/fs_avb.h"
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#include <fcntl.h>
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#include <libgen.h>
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#include <string.h>
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#include <sys/ioctl.h>
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#include <sys/types.h>
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#include <sstream>
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#include <string>
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#include <vector>
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#include <android-base/file.h>
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#include <android-base/parseint.h>
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#include <android-base/stringprintf.h>
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#include <android-base/strings.h>
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#include <libavb/libavb.h>
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#include <libdm/dm.h>
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#include "avb_ops.h"
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#include "avb_util.h"
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#include "sha.h"
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#include "util.h"
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using android::base::Basename;
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using android::base::ParseUint;
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using android::base::ReadFileToString;
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using android::base::Split;
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using android::base::StringPrintf;
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namespace android {
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namespace fs_mgr {
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template <typename Hasher>
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std::pair<size_t, bool> VerifyVbmetaDigest(const std::vector<VBMetaData>& vbmeta_images,
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const uint8_t* expected_digest) {
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size_t total_size = 0;
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Hasher hasher;
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for (const auto& vbmeta : vbmeta_images) {
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hasher.update(vbmeta.data(), vbmeta.size());
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total_size += vbmeta.size();
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}
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bool matched = (memcmp(hasher.finalize(), expected_digest, Hasher::DIGEST_SIZE) == 0);
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return std::make_pair(total_size, matched);
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}
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template <typename Hasher>
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std::pair<std::string, size_t> CalculateVbmetaDigest(const std::vector<VBMetaData>& vbmeta_images) {
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std::string digest;
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size_t total_size = 0;
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Hasher hasher;
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for (const auto& vbmeta : vbmeta_images) {
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hasher.update(vbmeta.data(), vbmeta.size());
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total_size += vbmeta.size();
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}
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// Converts digest bytes to a hex string.
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digest = BytesToHex(hasher.finalize(), Hasher::DIGEST_SIZE);
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return std::make_pair(digest, total_size);
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}
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// class AvbVerifier
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// -----------------
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// Reads the following values from kernel cmdline and provides the
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// VerifyVbmetaImages() to verify AvbSlotVerifyData.
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// - androidboot.vbmeta.hash_alg
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// - androidboot.vbmeta.size
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// - androidboot.vbmeta.digest
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class AvbVerifier {
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public:
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// The factory method to return a unique_ptr<AvbVerifier>
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static std::unique_ptr<AvbVerifier> Create();
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bool VerifyVbmetaImages(const std::vector<VBMetaData>& vbmeta_images);
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protected:
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AvbVerifier() = default;
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private:
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HashAlgorithm hash_alg_;
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uint8_t digest_[SHA512_DIGEST_LENGTH];
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size_t vbmeta_size_;
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};
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std::unique_ptr<AvbVerifier> AvbVerifier::Create() {
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std::unique_ptr<AvbVerifier> avb_verifier(new AvbVerifier());
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if (!avb_verifier) {
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LERROR << "Failed to create unique_ptr<AvbVerifier>";
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return nullptr;
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}
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std::string value;
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if (!fs_mgr_get_boot_config("vbmeta.size", &value) ||
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!ParseUint(value.c_str(), &avb_verifier->vbmeta_size_)) {
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LERROR << "Invalid hash size: " << value.c_str();
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return nullptr;
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}
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// Reads hash algorithm.
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size_t expected_digest_size = 0;
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std::string hash_alg;
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fs_mgr_get_boot_config("vbmeta.hash_alg", &hash_alg);
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if (hash_alg == "sha256") {
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expected_digest_size = SHA256_DIGEST_LENGTH * 2;
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avb_verifier->hash_alg_ = HashAlgorithm::kSHA256;
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} else if (hash_alg == "sha512") {
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expected_digest_size = SHA512_DIGEST_LENGTH * 2;
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avb_verifier->hash_alg_ = HashAlgorithm::kSHA512;
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} else {
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LERROR << "Unknown hash algorithm: " << hash_alg.c_str();
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return nullptr;
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}
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// Reads digest.
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std::string digest;
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fs_mgr_get_boot_config("vbmeta.digest", &digest);
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if (digest.size() != expected_digest_size) {
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LERROR << "Unexpected digest size: " << digest.size()
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<< " (expected: " << expected_digest_size << ")";
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return nullptr;
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}
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if (!HexToBytes(avb_verifier->digest_, sizeof(avb_verifier->digest_), digest)) {
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LERROR << "Hash digest contains non-hexidecimal character: " << digest.c_str();
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return nullptr;
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}
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return avb_verifier;
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}
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bool AvbVerifier::VerifyVbmetaImages(const std::vector<VBMetaData>& vbmeta_images) {
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if (vbmeta_images.empty()) {
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LERROR << "No vbmeta images";
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return false;
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}
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size_t total_size = 0;
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bool digest_matched = false;
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if (hash_alg_ == HashAlgorithm::kSHA256) {
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std::tie(total_size, digest_matched) =
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VerifyVbmetaDigest<SHA256Hasher>(vbmeta_images, digest_);
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} else if (hash_alg_ == HashAlgorithm::kSHA512) {
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std::tie(total_size, digest_matched) =
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VerifyVbmetaDigest<SHA512Hasher>(vbmeta_images, digest_);
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}
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if (total_size != vbmeta_size_) {
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LERROR << "total vbmeta size mismatch: " << total_size << " (expected: " << vbmeta_size_
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<< ")";
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return false;
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}
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if (!digest_matched) {
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LERROR << "vbmeta digest mismatch";
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return false;
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}
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return true;
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}
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// class AvbHandle
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// ---------------
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AvbUniquePtr AvbHandle::LoadAndVerifyVbmeta(
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const std::string& partition_name, const std::string& ab_suffix,
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const std::string& ab_other_suffix, const std::string& expected_public_key_path,
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const HashAlgorithm& hash_algorithm, bool allow_verification_error,
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bool load_chained_vbmeta, bool rollback_protection,
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std::function<std::string(const std::string&)> custom_device_path) {
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AvbUniquePtr avb_handle(new AvbHandle());
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if (!avb_handle) {
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LERROR << "Failed to allocate AvbHandle";
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return nullptr;
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}
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std::string expected_key_blob;
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if (!expected_public_key_path.empty()) {
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if (access(expected_public_key_path.c_str(), F_OK) != 0) {
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LERROR << "Expected public key path doesn't exist: " << expected_public_key_path;
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return nullptr;
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} else if (!ReadFileToString(expected_public_key_path, &expected_key_blob)) {
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LERROR << "Failed to load: " << expected_public_key_path;
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return nullptr;
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}
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}
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auto android_by_name_symlink = [](const std::string& partition_name_with_ab) {
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return "/dev/block/by-name/" + partition_name_with_ab;
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};
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auto device_path = custom_device_path ? custom_device_path : android_by_name_symlink;
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auto verify_result = LoadAndVerifyVbmetaByPartition(
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partition_name, ab_suffix, ab_other_suffix, expected_key_blob, allow_verification_error,
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load_chained_vbmeta, rollback_protection, device_path, false,
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/* is_chained_vbmeta */ &avb_handle->vbmeta_images_);
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switch (verify_result) {
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case VBMetaVerifyResult::kSuccess:
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avb_handle->status_ = AvbHandleStatus::kSuccess;
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break;
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case VBMetaVerifyResult::kErrorVerification:
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avb_handle->status_ = AvbHandleStatus::kVerificationError;
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break;
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default:
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LERROR << "LoadAndVerifyVbmetaByPartition failed, result: " << verify_result;
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return nullptr;
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}
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// Sanity check here because we have to use vbmeta_images_[0] below.
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if (avb_handle->vbmeta_images_.size() < 1) {
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LERROR << "LoadAndVerifyVbmetaByPartition failed, no vbmeta loaded";
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return nullptr;
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}
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// Sets the MAJOR.MINOR for init to set it into "ro.boot.avb_version".
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avb_handle->avb_version_ = StringPrintf("%d.%d", AVB_VERSION_MAJOR, AVB_VERSION_MINOR);
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// Checks any disabled flag is set.
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std::unique_ptr<AvbVBMetaImageHeader> vbmeta_header =
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avb_handle->vbmeta_images_[0].GetVBMetaHeader();
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bool verification_disabled = ((AvbVBMetaImageFlags)vbmeta_header->flags &
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AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED);
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bool hashtree_disabled =
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((AvbVBMetaImageFlags)vbmeta_header->flags & AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED);
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if (verification_disabled) {
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avb_handle->status_ = AvbHandleStatus::kVerificationDisabled;
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} else if (hashtree_disabled) {
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avb_handle->status_ = AvbHandleStatus::kHashtreeDisabled;
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}
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// Calculates the summary info for all vbmeta_images_;
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std::string digest;
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size_t total_size;
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if (hash_algorithm == HashAlgorithm::kSHA256) {
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std::tie(digest, total_size) =
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CalculateVbmetaDigest<SHA256Hasher>(avb_handle->vbmeta_images_);
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} else if (hash_algorithm == HashAlgorithm::kSHA512) {
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std::tie(digest, total_size) =
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CalculateVbmetaDigest<SHA512Hasher>(avb_handle->vbmeta_images_);
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} else {
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LERROR << "Invalid hash algorithm";
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return nullptr;
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}
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avb_handle->vbmeta_info_ = VBMetaInfo(digest, hash_algorithm, total_size);
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LINFO << "Returning avb_handle with status: " << avb_handle->status_;
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return avb_handle;
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}
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AvbUniquePtr AvbHandle::LoadAndVerifyVbmeta(const FstabEntry& fstab_entry) {
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if (fstab_entry.avb_keys.empty()) {
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LERROR << "avb_keys=/path/to/key(s) is missing for " << fstab_entry.mount_point;
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return nullptr;
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}
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// Binds allow_verification_error and rollback_protection to device unlock state.
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bool allow_verification_error = IsDeviceUnlocked();
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bool rollback_protection = !allow_verification_error;
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std::string public_key_data;
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bool verification_disabled = false;
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VBMetaVerifyResult verify_result = VBMetaVerifyResult::kError;
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std::unique_ptr<VBMetaData> vbmeta = LoadAndVerifyVbmetaByPath(
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fstab_entry.blk_device, "" /* partition_name, no need for a standalone path */,
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"" /* expected_public_key_blob, */, allow_verification_error, rollback_protection,
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false /* not is_chained_vbmeta */, &public_key_data, &verification_disabled,
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&verify_result);
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if (!vbmeta) {
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LERROR << "Failed to load vbmeta: " << fstab_entry.blk_device;
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return nullptr;
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}
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AvbUniquePtr avb_handle(new AvbHandle());
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if (!avb_handle) {
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LERROR << "Failed to allocate AvbHandle";
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return nullptr;
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}
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avb_handle->vbmeta_images_.emplace_back(std::move(*vbmeta));
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switch (verify_result) {
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case VBMetaVerifyResult::kSuccess:
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avb_handle->status_ = AvbHandleStatus::kSuccess;
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break;
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case VBMetaVerifyResult::kErrorVerification:
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avb_handle->status_ = AvbHandleStatus::kVerificationError;
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break;
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default:
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LERROR << "LoadAndVerifyVbmetaByPath failed, result: " << verify_result;
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return nullptr;
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}
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if (!ValidatePublicKeyBlob(public_key_data, Split(fstab_entry.avb_keys, ":"))) {
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avb_handle->status_ = AvbHandleStatus::kVerificationError;
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LWARNING << "Found unknown public key used to sign " << fstab_entry.mount_point;
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if (!allow_verification_error) {
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LERROR << "Unknown public key is not allowed";
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return nullptr;
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}
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}
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if (verification_disabled) {
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LINFO << "AVB verification disabled on: " << fstab_entry.mount_point;
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avb_handle->status_ = AvbHandleStatus::kVerificationDisabled;
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}
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LINFO << "Returning avb_handle for '" << fstab_entry.mount_point
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<< "' with status: " << avb_handle->status_;
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return avb_handle;
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}
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AvbUniquePtr AvbHandle::LoadAndVerifyVbmeta() {
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// Loads inline vbmeta images, starting from /vbmeta.
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return LoadAndVerifyVbmeta("vbmeta", fs_mgr_get_slot_suffix(), fs_mgr_get_other_slot_suffix(),
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{} /* expected_public_key, already checked by bootloader */,
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HashAlgorithm::kSHA256,
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IsDeviceUnlocked(), /* allow_verification_error */
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true, /* load_chained_vbmeta */
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false, /* rollback_protection, already checked by bootloader */
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nullptr /* custom_device_path */);
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}
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// TODO(b/128807537): removes this function.
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AvbUniquePtr AvbHandle::Open() {
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bool is_device_unlocked = IsDeviceUnlocked();
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AvbUniquePtr avb_handle(new AvbHandle());
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if (!avb_handle) {
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LERROR << "Failed to allocate AvbHandle";
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return nullptr;
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}
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FsManagerAvbOps avb_ops;
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AvbSlotVerifyFlags flags = is_device_unlocked ? AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR
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: AVB_SLOT_VERIFY_FLAGS_NONE;
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AvbSlotVerifyResult verify_result =
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avb_ops.AvbSlotVerify(fs_mgr_get_slot_suffix(), flags, &avb_handle->vbmeta_images_);
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// Only allow the following verify results:
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// - AVB_SLOT_VERIFY_RESULT_OK.
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// - AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION (UNLOCKED only).
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// Might occur in either the top-level vbmeta or a chained vbmeta.
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// - AVB_SLOT_VERIFY_RESULT_ERROR_PUBLIC_KEY_REJECTED (UNLOCKED only).
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// Could only occur in a chained vbmeta. Because we have *dummy* operations in
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// FsManagerAvbOps such that avb_ops->validate_vbmeta_public_key() used to validate
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// the public key of the top-level vbmeta always pass in userspace here.
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//
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// The following verify result won't happen, because the *dummy* operation
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// avb_ops->read_rollback_index() always returns the minimum value zero. So rollbacked
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// vbmeta images, which should be caught in the bootloader stage, won't be detected here.
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// - AVB_SLOT_VERIFY_RESULT_ERROR_ROLLBACK_INDEX
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switch (verify_result) {
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case AVB_SLOT_VERIFY_RESULT_OK:
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avb_handle->status_ = AvbHandleStatus::kSuccess;
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break;
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case AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION:
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case AVB_SLOT_VERIFY_RESULT_ERROR_PUBLIC_KEY_REJECTED:
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if (!is_device_unlocked) {
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LERROR << "ERROR_VERIFICATION / PUBLIC_KEY_REJECTED isn't allowed "
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<< "if the device is LOCKED";
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return nullptr;
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}
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avb_handle->status_ = AvbHandleStatus::kVerificationError;
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break;
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default:
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LERROR << "avb_slot_verify failed, result: " << verify_result;
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return nullptr;
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}
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// Sets the MAJOR.MINOR for init to set it into "ro.boot.avb_version".
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avb_handle->avb_version_ = StringPrintf("%d.%d", AVB_VERSION_MAJOR, AVB_VERSION_MINOR);
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// Checks whether FLAGS_VERIFICATION_DISABLED is set:
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// - Only the top-level vbmeta struct is read.
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// - vbmeta struct in other partitions are NOT processed, including AVB HASH descriptor(s)
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// and AVB HASHTREE descriptor(s).
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AvbVBMetaImageHeader vbmeta_header;
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avb_vbmeta_image_header_to_host_byte_order(
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(AvbVBMetaImageHeader*)avb_handle->vbmeta_images_[0].data(), &vbmeta_header);
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bool verification_disabled = ((AvbVBMetaImageFlags)vbmeta_header.flags &
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AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED);
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if (verification_disabled) {
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avb_handle->status_ = AvbHandleStatus::kVerificationDisabled;
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} else {
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// Verifies vbmeta structs against the digest passed from bootloader in kernel cmdline.
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std::unique_ptr<AvbVerifier> avb_verifier = AvbVerifier::Create();
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if (!avb_verifier) {
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LERROR << "Failed to create AvbVerifier";
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return nullptr;
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}
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if (!avb_verifier->VerifyVbmetaImages(avb_handle->vbmeta_images_)) {
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LERROR << "VerifyVbmetaImages failed";
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return nullptr;
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}
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// Checks whether FLAGS_HASHTREE_DISABLED is set.
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bool hashtree_disabled = ((AvbVBMetaImageFlags)vbmeta_header.flags &
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AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED);
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if (hashtree_disabled) {
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avb_handle->status_ = AvbHandleStatus::kHashtreeDisabled;
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}
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}
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LINFO << "Returning avb_handle with status: " << avb_handle->status_;
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return avb_handle;
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}
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AvbHashtreeResult AvbHandle::SetUpStandaloneAvbHashtree(FstabEntry* fstab_entry,
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bool wait_for_verity_dev) {
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auto avb_handle = LoadAndVerifyVbmeta(*fstab_entry);
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if (!avb_handle) {
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return AvbHashtreeResult::kFail;
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}
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return avb_handle->SetUpAvbHashtree(fstab_entry, wait_for_verity_dev);
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}
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AvbHashtreeResult AvbHandle::SetUpAvbHashtree(FstabEntry* fstab_entry, bool wait_for_verity_dev) {
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if (!fstab_entry || status_ == AvbHandleStatus::kUninitialized || vbmeta_images_.size() < 1) {
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return AvbHashtreeResult::kFail;
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}
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if (status_ == AvbHandleStatus::kHashtreeDisabled ||
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status_ == AvbHandleStatus::kVerificationDisabled) {
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LINFO << "AVB HASHTREE disabled on: " << fstab_entry->mount_point;
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return AvbHashtreeResult::kDisabled;
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}
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if (!LoadAvbHashtreeToEnableVerity(fstab_entry, wait_for_verity_dev, vbmeta_images_,
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fs_mgr_get_slot_suffix(), fs_mgr_get_other_slot_suffix())) {
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return AvbHashtreeResult::kFail;
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}
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return AvbHashtreeResult::kSuccess;
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}
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bool AvbHandle::TearDownAvbHashtree(FstabEntry* fstab_entry, bool wait) {
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if (!fstab_entry) {
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return false;
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}
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const std::string device_name(GetVerityDeviceName(*fstab_entry));
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// TODO: remove duplicated code with UnmapDevice()
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android::dm::DeviceMapper& dm = android::dm::DeviceMapper::Instance();
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std::string path;
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if (wait) {
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dm.GetDmDevicePathByName(device_name, &path);
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}
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if (!dm.DeleteDevice(device_name)) {
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return false;
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}
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if (!path.empty() && !WaitForFile(path, 1000ms, FileWaitMode::DoesNotExist)) {
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return false;
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}
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return true;
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}
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std::string AvbHandle::GetSecurityPatchLevel(const FstabEntry& fstab_entry) const {
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if (vbmeta_images_.size() < 1) {
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return "";
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}
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std::string avb_partition_name = DeriveAvbPartitionName(fstab_entry, fs_mgr_get_slot_suffix(),
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fs_mgr_get_other_slot_suffix());
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auto avb_prop_name = "com.android.build." + avb_partition_name + ".security_patch";
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return GetAvbPropertyDescriptor(avb_prop_name, vbmeta_images_);
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}
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bool AvbHandle::IsDeviceUnlocked() {
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return android::fs_mgr::IsDeviceUnlocked();
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}
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} // namespace fs_mgr
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} // namespace android
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