/*
* Copyright (C) 2015 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.
*/
/*
* update_verifier verifies the integrity of the partitions after an A/B OTA update. It gets invoked
* by init, and will only perform the verification if it's the first boot post an A/B OTA update
* (https://source.android.com/devices/tech/ota/ab/#after_reboot).
*
* update_verifier relies on device-mapper-verity (dm-verity) to capture any corruption on the
* partitions being verified (https://source.android.com/security/verifiedboot). The verification
* will be skipped, if dm-verity is not enabled on the device.
*
* Upon detecting verification failures, the device will be rebooted, although the trigger of the
* reboot depends on the dm-verity mode.
* enforcing mode: dm-verity reboots the device
* eio mode: dm-verity fails the read and update_verifier reboots the device
* other mode: not supported and update_verifier reboots the device
*
* All these reboots prevent the device from booting into a known corrupt state. If the device
* continuously fails to boot into the new slot, the bootloader should mark the slot as unbootable
* and trigger a fallback to the old slot.
*
* The current slot will be marked as having booted successfully if the verifier reaches the end
* after the verification.
*/
#include "update_verifier/update_verifier.h"
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <algorithm>
#include <future>
#include <string>
#include <vector>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/parseint.h>
#include <android-base/properties.h>
#include <android-base/strings.h>
#include <android-base/unique_fd.h>
#include <android/hardware/boot/1.0/IBootControl.h>
#include <cutils/android_reboot.h>
#include "otautil/rangeset.h"
using android::sp;
using android::hardware::boot::V1_0::IBootControl;
using android::hardware::boot::V1_0::BoolResult;
using android::hardware::boot::V1_0::CommandResult;
// Find directories in format of "/sys/block/dm-X".
static int dm_name_filter(const dirent* de) {
if (android::base::StartsWith(de->d_name, "dm-")) {
return 1;
}
return 0;
}
static bool read_blocks(const std::string& partition, const std::string& range_str) {
if (partition != "system" && partition != "vendor" && partition != "product") {
LOG(ERROR) << "Invalid partition name \"" << partition << "\"";
return false;
}
// Iterate the content of "/sys/block/dm-X/dm/name". If it matches one of "system", "vendor" or
// "product", then dm-X is a dm-wrapped device for that target. We will later read all the
// ("cared") blocks from "/dev/block/dm-X" to ensure the target partition's integrity.
static constexpr auto DM_PATH_PREFIX = "/sys/block/";
dirent** namelist;
int n = scandir(DM_PATH_PREFIX, &namelist, dm_name_filter, alphasort);
if (n == -1) {
PLOG(ERROR) << "Failed to scan dir " << DM_PATH_PREFIX;
return false;
}
if (n == 0) {
LOG(ERROR) << "dm block device not found for " << partition;
return false;
}
static constexpr auto DM_PATH_SUFFIX = "/dm/name";
static constexpr auto DEV_PATH = "/dev/block/";
std::string dm_block_device;
while (n--) {
std::string path = DM_PATH_PREFIX + std::string(namelist[n]->d_name) + DM_PATH_SUFFIX;
std::string content;
if (!android::base::ReadFileToString(path, &content)) {
PLOG(WARNING) << "Failed to read " << path;
} else {
std::string dm_block_name = android::base::Trim(content);
// AVB is using 'vroot' for the root block device but we're expecting 'system'.
if (dm_block_name == "vroot") {
dm_block_name = "system";
}
if (dm_block_name == partition) {
dm_block_device = DEV_PATH + std::string(namelist[n]->d_name);
while (n--) {
free(namelist[n]);
}
break;
}
}
free(namelist[n]);
}
free(namelist);
if (dm_block_device.empty()) {
LOG(ERROR) << "Failed to find dm block device for " << partition;
return false;
}
// For block range string, first integer 'count' equals 2 * total number of valid ranges,
// followed by 'count' number comma separated integers. Every two integers reprensent a
// block range with the first number included in range but second number not included.
// For example '4,64536,65343,74149,74150' represents: [64536,65343) and [74149,74150).
RangeSet ranges = RangeSet::Parse(range_str);
if (!ranges) {
LOG(ERROR) << "Error parsing RangeSet string " << range_str;
return false;
}
// RangeSet::Split() splits the ranges into multiple groups with same number of blocks (except for
// the last group).
size_t thread_num = std::thread::hardware_concurrency() ?: 4;
std::vector<RangeSet> groups = ranges.Split(thread_num);
std::vector<std::future<bool>> threads;
for (const auto& group : groups) {
auto thread_func = [&group, &dm_block_device, &partition]() {
android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(dm_block_device.c_str(), O_RDONLY)));
if (fd.get() == -1) {
PLOG(ERROR) << "Error reading " << dm_block_device << " for partition " << partition;
return false;
}
static constexpr size_t kBlockSize = 4096;
std::vector<uint8_t> buf(1024 * kBlockSize);
size_t block_count = 0;
for (const auto& range : group) {
size_t range_start = range.first;
size_t range_end = range.second;
if (lseek64(fd.get(), static_cast<off64_t>(range_start) * kBlockSize, SEEK_SET) == -1) {
PLOG(ERROR) << "lseek to " << range_start << " failed";
return false;
}
size_t remain = (range_end - range_start) * kBlockSize;
while (remain > 0) {
size_t to_read = std::min(remain, 1024 * kBlockSize);
if (!android::base::ReadFully(fd.get(), buf.data(), to_read)) {
PLOG(ERROR) << "Failed to read blocks " << range_start << " to " << range_end;
return false;
}
remain -= to_read;
}
block_count += (range_end - range_start);
}
LOG(INFO) << "Finished reading " << block_count << " blocks on " << dm_block_device;
return true;
};
threads.emplace_back(std::async(std::launch::async, thread_func));
}
bool ret = true;
for (auto& t : threads) {
ret = t.get() && ret;
}
LOG(INFO) << "Finished reading blocks on " << dm_block_device << " with " << thread_num
<< " threads.";
return ret;
}
// Returns true to indicate a passing verification (or the error should be ignored); Otherwise
// returns false on fatal errors, where we should reject the current boot and trigger a fallback.
// Note that update_verifier should be backward compatible to not reject care_map.txt from old
// releases, which could otherwise fail to boot into the new release. For example, we've changed
// the care_map format between N and O. An O update_verifier would fail to work with N
// care_map.txt. This could be a result of sideloading an O OTA while the device having a pending N
// update.
bool verify_image(const std::string& care_map_name) {
android::base::unique_fd care_map_fd(TEMP_FAILURE_RETRY(open(care_map_name.c_str(), O_RDONLY)));
// If the device is flashed before the current boot, it may not have care_map.txt
// in /data/ota_package. To allow the device to continue booting in this situation,
// we should print a warning and skip the block verification.
if (care_map_fd.get() == -1) {
PLOG(WARNING) << "Failed to open " << care_map_name;
return true;
}
// care_map file has up to six lines, where every two lines make a pair. Within each pair, the
// first line has the partition name (e.g. "system"), while the second line holds the ranges of
// all the blocks to verify.
std::string file_content;
if (!android::base::ReadFdToString(care_map_fd.get(), &file_content)) {
LOG(ERROR) << "Error reading care map contents to string.";
return false;
}
std::vector<std::string> lines;
lines = android::base::Split(android::base::Trim(file_content), "\n");
if (lines.size() != 2 && lines.size() != 4 && lines.size() != 6) {
LOG(ERROR) << "Invalid lines in care_map: found " << lines.size()
<< " lines, expecting 2 or 4 or 6 lines.";
return false;
}
for (size_t i = 0; i < lines.size(); i += 2) {
// We're seeing an N care_map.txt. Skip the verification since it's not compatible with O
// update_verifier (the last few metadata blocks can't be read via device mapper).
if (android::base::StartsWith(lines[i], "/dev/block/")) {
LOG(WARNING) << "Found legacy care_map.txt; skipped.";
return true;
}
if (!read_blocks(lines[i], lines[i+1])) {
return false;
}
}
return true;
}
static int reboot_device() {
if (android_reboot(ANDROID_RB_RESTART2, 0, nullptr) == -1) {
LOG(ERROR) << "Failed to reboot.";
return -1;
}
while (true) pause();
}
int update_verifier(int argc, char** argv) {
for (int i = 1; i < argc; i++) {
LOG(INFO) << "Started with arg " << i << ": " << argv[i];
}
sp<IBootControl> module = IBootControl::getService();
if (module == nullptr) {
LOG(ERROR) << "Error getting bootctrl module.";
return reboot_device();
}
uint32_t current_slot = module->getCurrentSlot();
BoolResult is_successful = module->isSlotMarkedSuccessful(current_slot);
LOG(INFO) << "Booting slot " << current_slot << ": isSlotMarkedSuccessful="
<< static_cast<int32_t>(is_successful);
if (is_successful == BoolResult::FALSE) {
// The current slot has not booted successfully.
bool skip_verification = false;
std::string verity_mode = android::base::GetProperty("ro.boot.veritymode", "");
if (verity_mode.empty()) {
// Skip the verification if ro.boot.veritymode property is not set. This could be a result
// that device doesn't support dm-verity, or has disabled that.
LOG(WARNING) << "dm-verity not enabled; marking without verification.";
skip_verification = true;
} else if (android::base::EqualsIgnoreCase(verity_mode, "eio")) {
// We shouldn't see verity in EIO mode if the current slot hasn't booted successfully before.
// Continue the verification until we fail to read some blocks.
LOG(WARNING) << "Found dm-verity in EIO mode.";
} else if (android::base::EqualsIgnoreCase(verity_mode, "disabled")) {
LOG(WARNING) << "dm-verity in disabled mode; marking without verification.";
skip_verification = true;
} else if (verity_mode != "enforcing") {
LOG(ERROR) << "Unexpected dm-verity mode: " << verity_mode << ", expecting enforcing.";
return reboot_device();
}
if (!skip_verification) {
static constexpr auto CARE_MAP_FILE = "/data/ota_package/care_map.txt";
if (!verify_image(CARE_MAP_FILE)) {
LOG(ERROR) << "Failed to verify all blocks in care map file.";
return reboot_device();
}
}
CommandResult cr;
module->markBootSuccessful([&cr](CommandResult result) { cr = result; });
if (!cr.success) {
LOG(ERROR) << "Error marking booted successfully: " << cr.errMsg;
return reboot_device();
}
LOG(INFO) << "Marked slot " << current_slot << " as booted successfully.";
}
LOG(INFO) << "Leaving update_verifier.";
return 0;
}
