payload_consumer/delta_performer.cc

//
// Copyright (C) 2012 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 "update_engine/payload_consumer/delta_performer.h"

#include <errno.h>
#include <linux/fs.h>

#include <algorithm>
#include <cstring>
#include <map>
#include <memory>
#include <set>
#include <string>
#include <utility>
#include <vector>

#include <base/files/file_util.h>
#include <base/format_macros.h>
#include <base/metrics/histogram_macros.h>
#include <base/strings/string_number_conversions.h>
#include <base/time/time.h>
#include <brillo/data_encoding.h>
#include <bsdiff/bspatch.h>
#include <google/protobuf/repeated_field.h>
#include <puffin/puffpatch.h>

#include "update_engine/common/constants.h"
#include "update_engine/common/download_action.h"
#include "update_engine/common/error_code.h"
#include "update_engine/common/error_code_utils.h"
#include "update_engine/common/hardware_interface.h"
#include "update_engine/common/prefs_interface.h"
#include "update_engine/common/subprocess.h"
#include "update_engine/common/terminator.h"
#include "update_engine/common/utils.h"
#include "update_engine/payload_consumer/bzip_extent_writer.h"
#include "update_engine/payload_consumer/cached_file_descriptor.h"
#include "update_engine/payload_consumer/certificate_parser_interface.h"
#include "update_engine/payload_consumer/extent_reader.h"
#include "update_engine/payload_consumer/extent_writer.h"
#include "update_engine/payload_consumer/partition_update_generator_interface.h"
#include "update_engine/payload_consumer/partition_writer.h"
#if USE_FEC
#include "update_engine/payload_consumer/fec_file_descriptor.h"
#endif  // USE_FEC
#include "update_engine/payload_consumer/file_descriptor_utils.h"
#include "update_engine/payload_consumer/mount_history.h"
#include "update_engine/payload_consumer/payload_constants.h"
#include "update_engine/payload_consumer/payload_verifier.h"
#include "update_engine/payload_consumer/xz_extent_writer.h"

using google::protobuf::RepeatedPtrField;
using std::min;
using std::string;
using std::vector;

namespace chromeos_update_engine {
const unsigned DeltaPerformer::kProgressLogMaxChunks = 10;
const unsigned DeltaPerformer::kProgressLogTimeoutSeconds = 30;
const unsigned DeltaPerformer::kProgressDownloadWeight = 50;
const unsigned DeltaPerformer::kProgressOperationsWeight = 50;
const uint64_t DeltaPerformer::kCheckpointFrequencySeconds = 1;

namespace {
const int kUpdateStateOperationInvalid = -1;
const int kMaxResumedUpdateFailures = 10;

}  // namespace

// Computes the ratio of |part| and |total|, scaled to |norm|, using integer
// arithmetic.
static uint64_t IntRatio(uint64_t part, uint64_t total, uint64_t norm) {
  return part * norm / total;
}

void DeltaPerformer::LogProgress(const char* message_prefix) {
  // Format operations total count and percentage.
  string total_operations_str("?");
  string completed_percentage_str("");
  if (num_total_operations_) {
    total_operations_str = std::to_string(num_total_operations_);
    // Upcasting to 64-bit to avoid overflow, back to size_t for formatting.
    completed_percentage_str = base::StringPrintf(
        " (%" PRIu64 "%%)",
        IntRatio(next_operation_num_, num_total_operations_, 100));
  }

  // Format download total count and percentage.
  size_t payload_size = payload_->size;
  string payload_size_str("?");
  string downloaded_percentage_str("");
  if (payload_size) {
    payload_size_str = std::to_string(payload_size);
    // Upcasting to 64-bit to avoid overflow, back to size_t for formatting.
    downloaded_percentage_str = base::StringPrintf(
        " (%" PRIu64 "%%)", IntRatio(total_bytes_received_, payload_size, 100));
  }

  LOG(INFO) << (message_prefix ? message_prefix : "") << next_operation_num_
            << "/" << total_operations_str << " operations"
            << completed_percentage_str << ", " << total_bytes_received_ << "/"
            << payload_size_str << " bytes downloaded"
            << downloaded_percentage_str << ", overall progress "
            << overall_progress_ << "%";
}

void DeltaPerformer::UpdateOverallProgress(bool force_log,
                                           const char* message_prefix) {
  // Compute our download and overall progress.
  unsigned new_overall_progress = 0;
  static_assert(kProgressDownloadWeight + kProgressOperationsWeight == 100,
                "Progress weights don't add up");
  // Only consider download progress if its total size is known; otherwise
  // adjust the operations weight to compensate for the absence of download
  // progress. Also, make sure to cap the download portion at
  // kProgressDownloadWeight, in case we end up downloading more than we
  // initially expected (this indicates a problem, but could generally happen).
  // TODO(garnold) the correction of operations weight when we do not have the
  // total payload size, as well as the conditional guard below, should both be
  // eliminated once we ensure that the payload_size in the install plan is
  // always given and is non-zero. This currently isn't the case during unit
  // tests (see chromium-os:37969).
  size_t payload_size = payload_->size;
  unsigned actual_operations_weight = kProgressOperationsWeight;
  if (payload_size)
    new_overall_progress +=
        min(static_cast<unsigned>(IntRatio(
                total_bytes_received_, payload_size, kProgressDownloadWeight)),
            kProgressDownloadWeight);
  else
    actual_operations_weight += kProgressDownloadWeight;

  // Only add completed operations if their total number is known; we definitely
  // expect an update to have at least one operation, so the expectation is that
  // this will eventually reach |actual_operations_weight|.
  if (num_total_operations_)
    new_overall_progress += IntRatio(
        next_operation_num_, num_total_operations_, actual_operations_weight);

  // Progress ratio cannot recede, unless our assumptions about the total
  // payload size, total number of operations, or the monotonicity of progress
  // is breached.
  if (new_overall_progress < overall_progress_) {
    LOG(WARNING) << "progress counter receded from " << overall_progress_
                 << "% down to " << new_overall_progress << "%; this is a bug";
    force_log = true;
  }
  overall_progress_ = new_overall_progress;

  // Update chunk index, log as needed: if forced by called, or we completed a
  // progress chunk, or a timeout has expired.
  base::TimeTicks curr_time = base::TimeTicks::Now();
  unsigned curr_progress_chunk =
      overall_progress_ * kProgressLogMaxChunks / 100;
  if (force_log || curr_progress_chunk > last_progress_chunk_ ||
      curr_time > forced_progress_log_time_) {
    forced_progress_log_time_ = curr_time + forced_progress_log_wait_;
    LogProgress(message_prefix);
  }
  last_progress_chunk_ = curr_progress_chunk;
}

size_t DeltaPerformer::CopyDataToBuffer(const char** bytes_p,
                                        size_t* count_p,
                                        size_t max) {
  const size_t count = *count_p;
  if (!count)
    return 0;  // Special case shortcut.
  size_t read_len = min(count, max - buffer_.size());
  const char* bytes_start = *bytes_p;
  const char* bytes_end = bytes_start + read_len;
  buffer_.reserve(max);
  buffer_.insert(buffer_.end(), bytes_start, bytes_end);
  *bytes_p = bytes_end;
  *count_p = count - read_len;
  return read_len;
}

bool DeltaPerformer::HandleOpResult(bool op_result,
                                    const char* op_type_name,
                                    ErrorCode* error) {
  if (op_result)
    return true;

  LOG(ERROR) << "Failed to perform " << op_type_name << " operation "
             << next_operation_num_ << ", which is the operation "
             << GetPartitionOperationNum() << " in partition \""
             << partitions_[current_partition_].partition_name() << "\"";
  if (*error == ErrorCode::kSuccess)
    *error = ErrorCode::kDownloadOperationExecutionError;
  return false;
}

int DeltaPerformer::Close() {
  int err = -CloseCurrentPartition();
  LOG_IF(ERROR,
         !payload_hash_calculator_.Finalize() ||
             !signed_hash_calculator_.Finalize())
      << "Unable to finalize the hash.";
  if (!buffer_.empty()) {
    LOG(INFO) << "Discarding " << buffer_.size() << " unused downloaded bytes";
    if (err >= 0)
      err = 1;
  }
  return -err;
}

int DeltaPerformer::CloseCurrentPartition() {
  if (!partition_writer_) {
    return 0;
  }
  int err = partition_writer_->Close();
  partition_writer_ = nullptr;
  return err;
}

bool DeltaPerformer::OpenCurrentPartition() {
  if (current_partition_ >= partitions_.size())
    return false;

  const PartitionUpdate& partition = partitions_[current_partition_];
  size_t num_previous_partitions =
      install_plan_->partitions.size() - partitions_.size();
  const InstallPlan::Partition& install_part =
      install_plan_->partitions[num_previous_partitions + current_partition_];
  auto dynamic_control = boot_control_->GetDynamicPartitionControl();
  partition_writer_ = CreatePartitionWriter(
      partition,
      install_part,
      dynamic_control,
      block_size_,
      interactive_,
      IsDynamicPartition(install_part.name, install_plan_->target_slot));
  // Open source fds if we have a delta payload, or for partitions in the
  // partial update.
  const bool source_may_exist = manifest_.partial_update() ||
                                payload_->type == InstallPayloadType::kDelta;
  const size_t partition_operation_num = GetPartitionOperationNum();

  TEST_AND_RETURN_FALSE(partition_writer_->Init(
      install_plan_, source_may_exist, partition_operation_num));
  CheckpointUpdateProgress(true);
  return true;
}

size_t DeltaPerformer::GetPartitionOperationNum() {
  return next_operation_num_ -
         (current_partition_ ? acc_num_operations_[current_partition_ - 1] : 0);
}

namespace {

void LogPartitionInfoHash(const PartitionInfo& info, const string& tag) {
  string sha256 = HexEncode(info.hash());
  LOG(INFO) << "PartitionInfo " << tag << " sha256: " << sha256
            << " size: " << info.size();
}

void LogPartitionInfo(const vector<PartitionUpdate>& partitions) {
  for (const PartitionUpdate& partition : partitions) {
    if (partition.has_old_partition_info()) {
      LogPartitionInfoHash(partition.old_partition_info(),
                           "old " + partition.partition_name());
    }
    LogPartitionInfoHash(partition.new_partition_info(),
                         "new " + partition.partition_name());
  }
}

}  // namespace

bool DeltaPerformer::IsHeaderParsed() const {
  return metadata_size_ != 0;
}

MetadataParseResult DeltaPerformer::ParsePayloadMetadata(
    const brillo::Blob& payload, ErrorCode* error) {
  *error = ErrorCode::kSuccess;

  if (!IsHeaderParsed()) {
    MetadataParseResult result =
        payload_metadata_.ParsePayloadHeader(payload, error);
    if (result != MetadataParseResult::kSuccess)
      return result;

    metadata_size_ = payload_metadata_.GetMetadataSize();
    metadata_signature_size_ = payload_metadata_.GetMetadataSignatureSize();
    major_payload_version_ = payload_metadata_.GetMajorVersion();

    // If the metadata size is present in install plan, check for it immediately
    // even before waiting for that many number of bytes to be downloaded in the
    // payload. This will prevent any attack which relies on us downloading data
    // beyond the expected metadata size.
    if (install_plan_->hash_checks_mandatory) {
      if (payload_->metadata_size != metadata_size_) {
        LOG(ERROR) << "Mandatory metadata size in Omaha response ("
                   << payload_->metadata_size
                   << ") is missing/incorrect, actual = " << metadata_size_;
        *error = ErrorCode::kDownloadInvalidMetadataSize;
        return MetadataParseResult::kError;
      }
    }

    // Check that the |metadata signature size_| and |metadata_size_| are not
    // very big numbers. This is necessary since |update_engine| needs to write
    // these values into the buffer before being able to use them, and if an
    // attacker sets these values to a very big number, the buffer will overflow
    // and |update_engine| will crash. A simple way of solving this is to check
    // that the size of both values is smaller than the payload itself.
    if (metadata_size_ + metadata_signature_size_ > payload_->size) {
      LOG(ERROR) << "The size of the metadata_size(" << metadata_size_ << ")"
                 << " or metadata signature(" << metadata_signature_size_ << ")"
                 << " is greater than the size of the payload"
                 << "(" << payload_->size << ")";
      *error = ErrorCode::kDownloadInvalidMetadataSize;
      return MetadataParseResult::kError;
    }
  }

  // Now that we have validated the metadata size, we should wait for the full
  // metadata and its signature (if exist) to be read in before we can parse it.
  if (payload.size() < metadata_size_ + metadata_signature_size_)
    return MetadataParseResult::kInsufficientData;

  // Log whether we validated the size or simply trusting what's in the payload
  // here. This is logged here (after we received the full metadata data) so
  // that we just log once (instead of logging n times) if it takes n
  // DeltaPerformer::Write calls to download the full manifest.
  if (payload_->metadata_size == metadata_size_) {
    LOG(INFO) << "Manifest size in payload matches expected value from Omaha";
  } else {
    // For mandatory-cases, we'd have already returned a kMetadataParseError
    // above. We'll be here only for non-mandatory cases. Just send a UMA stat.
    LOG(WARNING) << "Ignoring missing/incorrect metadata size ("
                 << payload_->metadata_size
                 << ") in Omaha response as validation is not mandatory. "
                 << "Trusting metadata size in payload = " << metadata_size_;
  }

  // NOLINTNEXTLINE(whitespace/braces)
  auto [payload_verifier, perform_verification] = CreatePayloadVerifier();
  if (!payload_verifier) {
    LOG(ERROR) << "Failed to create payload verifier.";
    *error = ErrorCode::kDownloadMetadataSignatureVerificationError;
    if (perform_verification) {
      return MetadataParseResult::kError;
    }
  } else {
    // We have the full metadata in |payload|. Verify its integrity
    // and authenticity based on the information we have in Omaha response.
    *error = payload_metadata_.ValidateMetadataSignature(
        payload, payload_->metadata_signature, *payload_verifier);
  }
  if (*error != ErrorCode::kSuccess) {
    if (install_plan_->hash_checks_mandatory) {
      // The autoupdate_CatchBadSignatures test checks for this string
      // in log-files. Keep in sync.
      LOG(ERROR) << "Mandatory metadata signature validation failed";
      return MetadataParseResult::kError;
    }

    // For non-mandatory cases, just send a UMA stat.
    LOG(WARNING) << "Ignoring metadata signature validation failures";
    *error = ErrorCode::kSuccess;
  }

  // The payload metadata is deemed valid, it's safe to parse the protobuf.
  if (!payload_metadata_.GetManifest(payload, &manifest_)) {
    LOG(ERROR) << "Unable to parse manifest in update file.";
    *error = ErrorCode::kDownloadManifestParseError;
    return MetadataParseResult::kError;
  }

  manifest_parsed_ = true;
  return MetadataParseResult::kSuccess;
}

#define OP_DURATION_HISTOGRAM(_op_name, _start_time)                        \
  LOCAL_HISTOGRAM_CUSTOM_TIMES(                                             \
      "UpdateEngine.DownloadAction.InstallOperation::" + string(_op_name) + \
          ".Duration",                                                      \
      (base::TimeTicks::Now() - _start_time),                               \
      base::TimeDelta::FromMilliseconds(10),                                \
      base::TimeDelta::FromMinutes(5),                                      \
      20);

// Wrapper around write. Returns true if all requested bytes
// were written, or false on any error, regardless of progress
// and stores an action exit code in |error|.
bool DeltaPerformer::Write(const void* bytes, size_t count, ErrorCode* error) {
  *error = ErrorCode::kSuccess;
  const char* c_bytes = reinterpret_cast<const char*>(bytes);

  // Update the total byte downloaded count and the progress logs.
  total_bytes_received_ += count;
  UpdateOverallProgress(false, "Completed ");

  while (!manifest_valid_) {
    // Read data up to the needed limit; this is either maximium payload header
    // size, or the full metadata size (once it becomes known).
    const bool do_read_header = !IsHeaderParsed();
    CopyDataToBuffer(
        &c_bytes,
        &count,
        (do_read_header ? kMaxPayloadHeaderSize
                        : metadata_size_ + metadata_signature_size_));

    MetadataParseResult result = ParsePayloadMetadata(buffer_, error);
    if (result == MetadataParseResult::kError)
      return false;
    if (result == MetadataParseResult::kInsufficientData) {
      // If we just processed the header, make an attempt on the manifest.
      if (do_read_header && IsHeaderParsed())
        continue;

      return true;
    }

    // Checks the integrity of the payload manifest.
    if ((*error = ValidateManifest()) != ErrorCode::kSuccess)
      return false;
    manifest_valid_ = true;
    if (!install_plan_->is_resume) {
      auto begin = reinterpret_cast<const char*>(buffer_.data());
      prefs_->SetString(kPrefsManifestBytes, {begin, buffer_.size()});
    }

    // Clear the download buffer.
    DiscardBuffer(false, metadata_size_);

    block_size_ = manifest_.block_size();

    // This populates |partitions_| and the |install_plan.partitions| with the
    // list of partitions from the manifest.
    if (!ParseManifestPartitions(error))
      return false;

    // |install_plan.partitions| was filled in, nothing need to be done here if
    // the payload was already applied, returns false to terminate http fetcher,
    // but keep |error| as ErrorCode::kSuccess.
    if (payload_->already_applied)
      return false;

    num_total_operations_ = 0;
    for (const auto& partition : partitions_) {
      num_total_operations_ += partition.operations_size();
      acc_num_operations_.push_back(num_total_operations_);
    }

    LOG_IF(WARNING,
           !prefs_->SetInt64(kPrefsManifestMetadataSize, metadata_size_))
        << "Unable to save the manifest metadata size.";
    LOG_IF(WARNING,
           !prefs_->SetInt64(kPrefsManifestSignatureSize,
                             metadata_signature_size_))
        << "Unable to save the manifest signature size.";

    if (!PrimeUpdateState()) {
      *error = ErrorCode::kDownloadStateInitializationError;
      LOG(ERROR) << "Unable to prime the update state.";
      return false;
    }

    if (next_operation_num_ < acc_num_operations_[current_partition_]) {
      if (!OpenCurrentPartition()) {
        *error = ErrorCode::kInstallDeviceOpenError;
        return false;
      }
    }

    if (next_operation_num_ > 0)
      UpdateOverallProgress(true, "Resuming after ");
    LOG(INFO) << "Starting to apply update payload operations";
  }

  while (next_operation_num_ < num_total_operations_) {
    // Check if we should cancel the current attempt for any reason.
    // In this case, *error will have already been populated with the reason
    // why we're canceling.
    if (download_delegate_ && download_delegate_->ShouldCancel(error))
      return false;

    // We know there are more operations to perform because we didn't reach the
    // |num_total_operations_| limit yet.
    if (next_operation_num_ >= acc_num_operations_[current_partition_]) {
      if (partition_writer_) {
        if (!partition_writer_->FinishedInstallOps()) {
          *error = ErrorCode::kDownloadWriteError;
          return false;
        }
      }
      CloseCurrentPartition();
      // Skip until there are operations for current_partition_.
      while (next_operation_num_ >= acc_num_operations_[current_partition_]) {
        current_partition_++;
      }
      if (!OpenCurrentPartition()) {
        *error = ErrorCode::kInstallDeviceOpenError;
        return false;
      }
    }

    const InstallOperation& op =
        partitions_[current_partition_].operations(GetPartitionOperationNum());

    CopyDataToBuffer(&c_bytes, &count, op.data_length());

    // Check whether we received all of the next operation's data payload.
    if (!CanPerformInstallOperation(op))
      return true;

    // Validate the operation unconditionally. This helps prevent the
    // exploitation of vulnerabilities in the patching libraries, e.g. bspatch.
    // The hash of the patch data for a given operation is embedded in the
    // payload metadata; and thus has been verified against the public key on
    // device.
    // Note: Validate must be called only if CanPerformInstallOperation is
    // called. Otherwise, we might be failing operations before even if there
    // isn't sufficient data to compute the proper hash.
    *error = ValidateOperationHash(op);
    if (*error != ErrorCode::kSuccess) {
      if (install_plan_->hash_checks_mandatory) {
        LOG(ERROR) << "Mandatory operation hash check failed";
        return false;
      }

      // For non-mandatory cases, just send a UMA stat.
      LOG(WARNING) << "Ignoring operation validation errors";
      *error = ErrorCode::kSuccess;
    }

    // Makes sure we unblock exit when this operation completes.
    ScopedTerminatorExitUnblocker exit_unblocker =
        ScopedTerminatorExitUnblocker();  // Avoids a compiler unused var bug.

    base::TimeTicks op_start_time = base::TimeTicks::Now();

    bool op_result;
    const string op_name = InstallOperationTypeName(op.type());
    switch (op.type()) {
      case InstallOperation::REPLACE:
      case InstallOperation::REPLACE_BZ:
      case InstallOperation::REPLACE_XZ:
        op_result = PerformReplaceOperation(op);
        OP_DURATION_HISTOGRAM("REPLACE", op_start_time);
        break;
      case InstallOperation::ZERO:
      case InstallOperation::DISCARD:
        op_result = PerformZeroOrDiscardOperation(op);
        OP_DURATION_HISTOGRAM("ZERO_OR_DISCARD", op_start_time);
        break;
      case InstallOperation::SOURCE_COPY:
        op_result = PerformSourceCopyOperation(op, error);
        OP_DURATION_HISTOGRAM("SOURCE_COPY", op_start_time);
        break;
      case InstallOperation::SOURCE_BSDIFF:
      case InstallOperation::BROTLI_BSDIFF:
      case InstallOperation::PUFFDIFF:
      case InstallOperation::ZUCCHINI:
      case InstallOperation::LZ4DIFF_PUFFDIFF:
      case InstallOperation::LZ4DIFF_BSDIFF:
        op_result = PerformDiffOperation(op, error);
        OP_DURATION_HISTOGRAM(op_name, op_start_time);
        break;
      default:
        op_result = false;
    }
    if (!HandleOpResult(op_result, op_name.c_str(), error))
      return false;

    next_operation_num_++;
    UpdateOverallProgress(false, "Completed ");
    CheckpointUpdateProgress(false);
  }

  if (partition_writer_) {
    TEST_AND_RETURN_FALSE(partition_writer_->FinishedInstallOps());
  }
  CloseCurrentPartition();

  // In major version 2, we don't add unused operation to the payload.
  // If we already extracted the signature we should skip this step.
  if (manifest_.has_signatures_offset() && manifest_.has_signatures_size() &&
      signatures_message_data_.empty()) {
    if (manifest_.signatures_offset() != buffer_offset_) {
      LOG(ERROR) << "Payload signatures offset points to blob offset "
                 << manifest_.signatures_offset()
                 << " but signatures are expected at offset " << buffer_offset_;
      *error = ErrorCode::kDownloadPayloadVerificationError;
      return false;
    }
    CopyDataToBuffer(&c_bytes, &count, manifest_.signatures_size());
    // Needs more data to cover entire signature.
    if (buffer_.size() < manifest_.signatures_size())
      return true;
    if (!ExtractSignatureMessage()) {
      LOG(ERROR) << "Extract payload signature failed.";
      *error = ErrorCode::kDownloadPayloadVerificationError;
      return false;
    }
    DiscardBuffer(true, 0);
    // Since we extracted the SignatureMessage we need to advance the
    // checkpoint, otherwise we would reload the signature and try to extract
    // it again.
    // This is the last checkpoint for an update, force this checkpoint to be
    // saved.
    CheckpointUpdateProgress(true);
  }

  return true;
}

bool DeltaPerformer::IsManifestValid() {
  return manifest_valid_;
}

bool DeltaPerformer::ParseManifestPartitions(ErrorCode* error) {
  partitions_.assign(manifest_.partitions().begin(),
                     manifest_.partitions().end());

  // For VAB and partial updates, the partition preparation will copy the
  // dynamic partitions metadata to the target metadata slot, and rename the
  // slot suffix of the partitions in the metadata.
  if (install_plan_->target_slot != BootControlInterface::kInvalidSlot) {
    uint64_t required_size = 0;
    if (!PreparePartitionsForUpdate(&required_size)) {
      if (required_size > 0) {
        *error = ErrorCode::kNotEnoughSpace;
      } else {
        *error = ErrorCode::kInstallDeviceOpenError;
      }
      return false;
    }
  }

  // Partitions in manifest are no longer needed after preparing partitions.
  manifest_.clear_partitions();
  // TODO(xunchang) TBD: allow partial update only on devices with dynamic
  // partition.
  if (manifest_.partial_update()) {
    std::set<std::string> touched_partitions;
    for (const auto& partition_update : partitions_) {
      touched_partitions.insert(partition_update.partition_name());
    }

    auto generator = partition_update_generator::Create(boot_control_,
                                                        manifest_.block_size());
    std::vector<PartitionUpdate> untouched_static_partitions;
    TEST_AND_RETURN_FALSE(
        generator->GenerateOperationsForPartitionsNotInPayload(
            install_plan_->source_slot,
            install_plan_->target_slot,
            touched_partitions,
            &untouched_static_partitions));
    partitions_.insert(partitions_.end(),
                       untouched_static_partitions.begin(),
                       untouched_static_partitions.end());

    // Save the untouched dynamic partitions in install plan.
    std::vector<std::string> dynamic_partitions;
    if (!boot_control_->GetDynamicPartitionControl()
             ->ListDynamicPartitionsForSlot(install_plan_->source_slot,
                                            boot_control_->GetCurrentSlot(),
                                            &dynamic_partitions)) {
      LOG(ERROR) << "Failed to load dynamic partitions from slot "
                 << install_plan_->source_slot;
      return false;
    }
    install_plan_->untouched_dynamic_partitions.clear();
    for (const auto& name : dynamic_partitions) {
      if (touched_partitions.find(name) == touched_partitions.end()) {
        install_plan_->untouched_dynamic_partitions.push_back(name);
      }
    }
  }

  if (!install_plan_->ParsePartitions(
          partitions_, boot_control_, block_size_, error)) {
    return false;
  }

  LogPartitionInfo(partitions_);
  return true;
}

bool DeltaPerformer::PreparePartitionsForUpdate(uint64_t* required_size) {
  // Call static PreparePartitionsForUpdate with hash from
  // kPrefsUpdateCheckResponseHash to ensure hash of payload that space is
  // preallocated for is the same as the hash of payload being applied.
  string update_check_response_hash;
  ignore_result(prefs_->GetString(kPrefsUpdateCheckResponseHash,
                                  &update_check_response_hash));
  return PreparePartitionsForUpdate(prefs_,
                                    boot_control_,
                                    install_plan_->target_slot,
                                    manifest_,
                                    update_check_response_hash,
                                    required_size);
}

bool DeltaPerformer::PreparePartitionsForUpdate(
    PrefsInterface* prefs,
    BootControlInterface* boot_control,
    BootControlInterface::Slot target_slot,
    const DeltaArchiveManifest& manifest,
    const std::string& update_check_response_hash,
    uint64_t* required_size) {
  string last_hash;
  ignore_result(
      prefs->GetString(kPrefsDynamicPartitionMetadataUpdated, &last_hash));

  bool is_resume = !update_check_response_hash.empty() &&
                   last_hash == update_check_response_hash;

  if (is_resume) {
    LOG(INFO) << "Using previously prepared partitions for update. hash = "
              << last_hash;
  } else {
    LOG(INFO) << "Preparing partitions for new update. last hash = "
              << last_hash << ", new hash = " << update_check_response_hash;
    ResetUpdateProgress(prefs, false);
  }

  if (!boot_control->GetDynamicPartitionControl()->PreparePartitionsForUpdate(
          boot_control->GetCurrentSlot(),
          target_slot,
          manifest,
          !is_resume /* should update */,
          required_size)) {
    LOG(ERROR) << "Unable to initialize partition metadata for slot "
               << BootControlInterface::SlotName(target_slot);
    return false;
  }

  TEST_AND_RETURN_FALSE(prefs->SetString(kPrefsDynamicPartitionMetadataUpdated,
                                         update_check_response_hash));
  LOG(INFO) << "PreparePartitionsForUpdate done.";

  return true;
}

bool DeltaPerformer::CanPerformInstallOperation(
    const chromeos_update_engine::InstallOperation& operation) {
  // If we don't have a data blob we can apply it right away.
  if (!operation.has_data_offset() && !operation.has_data_length())
    return true;

  // See if we have the entire data blob in the buffer
  if (operation.data_offset() < buffer_offset_) {
    LOG(ERROR) << "we threw away data it seems?";
    return false;
  }

  return (operation.data_offset() + operation.data_length() <=
          buffer_offset_ + buffer_.size());
}

bool DeltaPerformer::PerformReplaceOperation(
    const InstallOperation& operation) {
  CHECK(operation.type() == InstallOperation::REPLACE ||
        operation.type() == InstallOperation::REPLACE_BZ ||
        operation.type() == InstallOperation::REPLACE_XZ);

  // Since we delete data off the beginning of the buffer as we use it,
  // the data we need should be exactly at the beginning of the buffer.
  TEST_AND_RETURN_FALSE(buffer_.size() >= operation.data_length());

  TEST_AND_RETURN_FALSE(partition_writer_->PerformReplaceOperation(
      operation, buffer_.data(), buffer_.size()));
  // Update buffer
  DiscardBuffer(true, buffer_.size());
  return true;
}

bool DeltaPerformer::PerformZeroOrDiscardOperation(
    const InstallOperation& operation) {
  CHECK(operation.type() == InstallOperation::DISCARD ||
        operation.type() == InstallOperation::ZERO);

  // These operations have no blob.
  TEST_AND_RETURN_FALSE(!operation.has_data_offset());
  TEST_AND_RETURN_FALSE(!operation.has_data_length());

  return partition_writer_->PerformZeroOrDiscardOperation(operation);
}

bool DeltaPerformer::PerformSourceCopyOperation(
    const InstallOperation& operation, ErrorCode* error) {
  if (operation.has_src_length())
    TEST_AND_RETURN_FALSE(operation.src_length() % block_size_ == 0);
  if (operation.has_dst_length())
    TEST_AND_RETURN_FALSE(operation.dst_length() % block_size_ == 0);
  return partition_writer_->PerformSourceCopyOperation(operation, error);
}

bool DeltaPerformer::ExtentsToBsdiffPositionsString(
    const RepeatedPtrField<Extent>& extents,
    uint64_t block_size,
    uint64_t full_length,
    string* positions_string) {
  string ret;
  uint64_t length = 0;
  for (const Extent& extent : extents) {
    int64_t start = extent.start_block() * block_size;
    uint64_t this_length =
        min(full_length - length,
            static_cast<uint64_t>(extent.num_blocks()) * block_size);
    ret += base::StringPrintf("%" PRIi64 ":%" PRIu64 ",", start, this_length);
    length += this_length;
  }
  TEST_AND_RETURN_FALSE(length == full_length);
  if (!ret.empty())
    ret.resize(ret.size() - 1);  // Strip trailing comma off
  *positions_string = ret;
  return true;
}

bool DeltaPerformer::PerformDiffOperation(const InstallOperation& operation,
                                          ErrorCode* error) {
  // Since we delete data off the beginning of the buffer as we use it,
  // the data we need should be exactly at the beginning of the buffer.
  TEST_AND_RETURN_FALSE(buffer_offset_ == operation.data_offset());
  TEST_AND_RETURN_FALSE(buffer_.size() >= operation.data_length());
  if (operation.has_src_length())
    TEST_AND_RETURN_FALSE(operation.src_length() % block_size_ == 0);
  if (operation.has_dst_length())
    TEST_AND_RETURN_FALSE(operation.dst_length() % block_size_ == 0);

  TEST_AND_RETURN_FALSE(partition_writer_->PerformDiffOperation(
      operation, error, buffer_.data(), buffer_.size()));
  DiscardBuffer(true, buffer_.size());
  return true;
}

bool DeltaPerformer::ExtractSignatureMessage() {
  TEST_AND_RETURN_FALSE(signatures_message_data_.empty());
  TEST_AND_RETURN_FALSE(buffer_offset_ == manifest_.signatures_offset());
  TEST_AND_RETURN_FALSE(buffer_.size() >= manifest_.signatures_size());
  signatures_message_data_.assign(
      buffer_.begin(), buffer_.begin() + manifest_.signatures_size());

  LOG(INFO) << "Extracted signature data of size "
            << manifest_.signatures_size() << " at "
            << manifest_.signatures_offset();
  return true;
}

bool DeltaPerformer::GetPublicKey(string* out_public_key) {
  out_public_key->clear();

  if (utils::FileExists(public_key_path_.c_str())) {
    LOG(INFO) << "Verifying using public key: " << public_key_path_;
    return utils::ReadFile(public_key_path_, out_public_key);
  }

  // If this is an official build then we are not allowed to use public key
  // from Omaha response.
  if (!hardware_->IsOfficialBuild() && !install_plan_->public_key_rsa.empty()) {
    LOG(INFO) << "Verifying using public key from Omaha response.";
    return brillo::data_encoding::Base64Decode(install_plan_->public_key_rsa,
                                               out_public_key);
  }
  LOG(INFO) << "No public keys found for verification.";
  return true;
}

std::pair<std::unique_ptr<PayloadVerifier>, bool>
DeltaPerformer::CreatePayloadVerifier() {
  if (utils::FileExists(update_certificates_path_.c_str())) {
    LOG(INFO) << "Verifying using certificates: " << update_certificates_path_;
    return {
        PayloadVerifier::CreateInstanceFromZipPath(update_certificates_path_),
        true};
  }

  string public_key;
  if (!GetPublicKey(&public_key)) {
    LOG(ERROR) << "Failed to read public key";
    return {nullptr, true};
  }

  // Skips the verification if the public key is empty.
  if (public_key.empty()) {
    return {nullptr, false};
  }
  LOG(INFO) << "Verifing using public key: " << public_key;
  return {PayloadVerifier::CreateInstance(public_key), true};
}

ErrorCode DeltaPerformer::ValidateManifest() {
  // Perform assorted checks to validation check the manifest, make sure it
  // matches data from other sources, and that it is a supported version.
  bool has_old_fields = std::any_of(manifest_.partitions().begin(),
                                    manifest_.partitions().end(),
                                    [](const PartitionUpdate& partition) {
                                      return partition.has_old_partition_info();
                                    });

  // The presence of an old partition hash is the sole indicator for a delta
  // update. Also, always treat the partial update as delta so that we can
  // perform the minor version check correctly.
  InstallPayloadType actual_payload_type =
      (has_old_fields || manifest_.partial_update())
          ? InstallPayloadType::kDelta
          : InstallPayloadType::kFull;

  if (payload_->type == InstallPayloadType::kUnknown) {
    LOG(INFO) << "Detected a '"
              << InstallPayloadTypeToString(actual_payload_type)
              << "' payload.";
    payload_->type = actual_payload_type;
  } else if (payload_->type != actual_payload_type) {
    LOG(ERROR) << "InstallPlan expected a '"
               << InstallPayloadTypeToString(payload_->type)
               << "' payload but the downloaded manifest contains a '"
               << InstallPayloadTypeToString(actual_payload_type)
               << "' payload.";
    return ErrorCode::kPayloadMismatchedType;
  }
  // Check that the minor version is compatible.
  // TODO(xunchang) increment minor version & add check for partial update
  if (actual_payload_type == InstallPayloadType::kFull) {
    if (manifest_.minor_version() != kFullPayloadMinorVersion) {
      LOG(ERROR) << "Manifest contains minor version "
                 << manifest_.minor_version()
                 << ", but all full payloads should have version "
                 << kFullPayloadMinorVersion << ".";
      return ErrorCode::kUnsupportedMinorPayloadVersion;
    }
  } else {
    if (manifest_.minor_version() < kMinSupportedMinorPayloadVersion ||
        manifest_.minor_version() > kMaxSupportedMinorPayloadVersion) {
      LOG(ERROR) << "Manifest contains minor version "
                 << manifest_.minor_version()
                 << " not in the range of supported minor versions ["
                 << kMinSupportedMinorPayloadVersion << ", "
                 << kMaxSupportedMinorPayloadVersion << "].";
      return ErrorCode::kUnsupportedMinorPayloadVersion;
    }
  }

  ErrorCode error_code = CheckTimestampError();
  if (error_code != ErrorCode::kSuccess) {
    if (error_code == ErrorCode::kPayloadTimestampError) {
      if (!hardware_->AllowDowngrade()) {
        return ErrorCode::kPayloadTimestampError;
      }
      LOG(INFO) << "The current OS build allows downgrade, continuing to apply"
                   " the payload with an older timestamp.";
    } else {
      LOG(ERROR) << "Timestamp check returned "
                 << utils::ErrorCodeToString(error_code);
      return error_code;
    }
  }

  // TODO(crbug.com/37661) we should be adding more and more manifest checks,
  // such as partition boundaries, etc.

  return ErrorCode::kSuccess;
}

ErrorCode DeltaPerformer::CheckTimestampError() const {
  bool is_partial_update =
      manifest_.has_partial_update() && manifest_.partial_update();
  const auto& partitions = manifest_.partitions();

  // Check version field for a given PartitionUpdate object. If an error
  // is encountered, set |error_code| accordingly. If downgrade is detected,
  // |downgrade_detected| is set. Return true if the program should continue
  // to check the next partition or not, or false if it should exit early due
  // to errors.
  auto&& timestamp_valid = [this](const PartitionUpdate& partition,
                                  bool allow_empty_version,
                                  bool* downgrade_detected) -> ErrorCode {
    const auto& partition_name = partition.partition_name();
    if (!partition.has_version()) {
      if (hardware_->GetVersionForLogging(partition_name).empty()) {
        LOG(INFO) << partition_name << " does't have version, skipping "
                  << "downgrade check.";
        return ErrorCode::kSuccess;
      }

      if (allow_empty_version) {
        return ErrorCode::kSuccess;
      }
      LOG(ERROR)
          << "PartitionUpdate " << partition_name
          << " doesn't have a version field. Not allowed in partial updates.";
      return ErrorCode::kDownloadManifestParseError;
    }

    auto error_code =
        hardware_->IsPartitionUpdateValid(partition_name, partition.version());
    switch (error_code) {
      case ErrorCode::kSuccess:
        break;
      case ErrorCode::kPayloadTimestampError:
        *downgrade_detected = true;
        LOG(WARNING) << "PartitionUpdate " << partition_name
                     << " has an older version than partition on device.";
        break;
      default:
        LOG(ERROR) << "IsPartitionUpdateValid(" << partition_name
                   << ") returned" << utils::ErrorCodeToString(error_code);
        break;
    }
    return error_code;
  };

  bool downgrade_detected = false;

  if (is_partial_update) {
    // for partial updates, all partition MUST have valid timestamps
    // But max_timestamp can be empty
    for (const auto& partition : partitions) {
      auto error_code = timestamp_valid(
          partition, false /* allow_empty_version */, &downgrade_detected);
      if (error_code != ErrorCode::kSuccess &&
          error_code != ErrorCode::kPayloadTimestampError) {
        return error_code;
      }
    }
    if (downgrade_detected) {
      return ErrorCode::kPayloadTimestampError;
    }
    return ErrorCode::kSuccess;
  }

  // For non-partial updates, check max_timestamp first.
  if (manifest_.max_timestamp() < hardware_->GetBuildTimestamp()) {
    LOG(ERROR) << "The current OS build timestamp ("
               << hardware_->GetBuildTimestamp()
               << ") is newer than the maximum timestamp in the manifest ("
               << manifest_.max_timestamp() << ")";
    return ErrorCode::kPayloadTimestampError;
  }
  // Otherwise... partitions can have empty timestamps.
  for (const auto& partition : partitions) {
    auto error_code = timestamp_valid(
        partition, true /* allow_empty_version */, &downgrade_detected);
    if (error_code != ErrorCode::kSuccess &&
        error_code != ErrorCode::kPayloadTimestampError) {
      return error_code;
    }
  }
  if (downgrade_detected) {
    return ErrorCode::kPayloadTimestampError;
  }
  return ErrorCode::kSuccess;
}

ErrorCode DeltaPerformer::ValidateOperationHash(
    const InstallOperation& operation) {
  if (!operation.data_sha256_hash().size()) {
    if (!operation.data_length()) {
      // Operations that do not have any data blob won't have any operation
      // hash either. So, these operations are always considered validated
      // since the metadata that contains all the non-data-blob portions of
      // the operation has already been validated. This is true for both HTTP
      // and HTTPS cases.
      return ErrorCode::kSuccess;
    }

    // No hash is present for an operation that has data blobs. This shouldn't
    // happen normally for any client that has this code, because the
    // corresponding update should have been produced with the operation
    // hashes. So if it happens it means either we've turned operation hash
    // generation off in DeltaDiffGenerator or it's a regression of some sort.
    // One caveat though: The last operation is a unused signature operation
    // that doesn't have a hash at the time the manifest is created. So we
    // should not complaint about that operation. This operation can be
    // recognized by the fact that it's offset is mentioned in the manifest.
    if (manifest_.signatures_offset() &&
        manifest_.signatures_offset() == operation.data_offset()) {
      LOG(INFO) << "Skipping hash verification for signature operation "
                << next_operation_num_ + 1;
    } else {
      if (install_plan_->hash_checks_mandatory) {
        LOG(ERROR) << "Missing mandatory operation hash for operation "
                   << next_operation_num_ + 1;
        return ErrorCode::kDownloadOperationHashMissingError;
      }

      LOG(WARNING) << "Cannot validate operation " << next_operation_num_ + 1
                   << " as there's no operation hash in manifest";
    }
    return ErrorCode::kSuccess;
  }

  brillo::Blob expected_op_hash;
  expected_op_hash.assign(operation.data_sha256_hash().data(),
                          (operation.data_sha256_hash().data() +
                           operation.data_sha256_hash().size()));

  brillo::Blob calculated_op_hash;
  if (!HashCalculator::RawHashOfBytes(
          buffer_.data(), operation.data_length(), &calculated_op_hash)) {
    LOG(ERROR) << "Unable to compute actual hash of operation "
               << next_operation_num_;
    return ErrorCode::kDownloadOperationHashVerificationError;
  }

  if (calculated_op_hash != expected_op_hash) {
    LOG(ERROR) << "Hash verification failed for operation "
               << next_operation_num_
               << ". Expected hash = " << HexEncode(expected_op_hash);
    LOG(ERROR) << "Calculated hash over " << operation.data_length()
               << " bytes at offset: " << operation.data_offset() << " = "
               << HexEncode(calculated_op_hash);
    return ErrorCode::kDownloadOperationHashMismatch;
  }

  return ErrorCode::kSuccess;
}

#define TEST_AND_RETURN_VAL(_retval, _condition)              \
  do {                                                        \
    if (!(_condition)) {                                      \
      LOG(ERROR) << "VerifyPayload failure: " << #_condition; \
      return _retval;                                         \
    }                                                         \
  } while (0);

ErrorCode DeltaPerformer::VerifyPayload(
    const brillo::Blob& update_check_response_hash,
    const uint64_t update_check_response_size) {
  // Verifies the download size.
  if (update_check_response_size !=
      metadata_size_ + metadata_signature_size_ + buffer_offset_) {
    LOG(ERROR) << "update_check_response_size (" << update_check_response_size
               << ") doesn't match metadata_size (" << metadata_size_
               << ") + metadata_signature_size (" << metadata_signature_size_
               << ") + buffer_offset (" << buffer_offset_ << ").";
    return ErrorCode::kPayloadSizeMismatchError;
  }

  // Verifies the payload hash.
  TEST_AND_RETURN_VAL(ErrorCode::kDownloadPayloadVerificationError,
                      !payload_hash_calculator_.raw_hash().empty());
  if (payload_hash_calculator_.raw_hash() != update_check_response_hash) {
    LOG(ERROR) << "Actual hash: "
               << HexEncode(payload_hash_calculator_.raw_hash())
               << ", expected hash: " << HexEncode(update_check_response_hash);
    return ErrorCode::kPayloadHashMismatchError;
  }

  // NOLINTNEXTLINE(whitespace/braces)
  auto [payload_verifier, perform_verification] = CreatePayloadVerifier();
  if (!perform_verification) {
    LOG(WARNING) << "Not verifying signed delta payload -- missing public key.";
    return ErrorCode::kSuccess;
  }
  if (!payload_verifier) {
    LOG(ERROR) << "Failed to create the payload verifier.";
    return ErrorCode::kDownloadPayloadPubKeyVerificationError;
  }

  TEST_AND_RETURN_VAL(ErrorCode::kSignedDeltaPayloadExpectedError,
                      !signatures_message_data_.empty());
  brillo::Blob hash_data = signed_hash_calculator_.raw_hash();
  TEST_AND_RETURN_VAL(ErrorCode::kDownloadPayloadPubKeyVerificationError,
                      hash_data.size() == kSHA256Size);

  if (!payload_verifier->VerifySignature(signatures_message_data_, hash_data)) {
    // The autoupdate_CatchBadSignatures test checks for this string
    // in log-files. Keep in sync.
    LOG(ERROR) << "Public key verification failed, thus update failed.";
    return ErrorCode::kDownloadPayloadPubKeyVerificationError;
  }

  LOG(INFO) << "Payload hash matches value in payload.";
  return ErrorCode::kSuccess;
}

void DeltaPerformer::DiscardBuffer(bool do_advance_offset,
                                   size_t signed_hash_buffer_size) {
  // Update the buffer offset.
  if (do_advance_offset)
    buffer_offset_ += buffer_.size();

  // Hash the content.
  payload_hash_calculator_.Update(buffer_.data(), buffer_.size());
  signed_hash_calculator_.Update(buffer_.data(), signed_hash_buffer_size);

  // Swap content with an empty vector to ensure that all memory is released.
  brillo::Blob().swap(buffer_);
}

bool DeltaPerformer::CanResumeUpdate(PrefsInterface* prefs,
                                     const string& update_check_response_hash) {
  int64_t next_operation = kUpdateStateOperationInvalid;
  if (!(prefs->GetInt64(kPrefsUpdateStateNextOperation, &next_operation) &&
        next_operation != kUpdateStateOperationInvalid && next_operation > 0))
    return false;

  string interrupted_hash;
  if (!(prefs->GetString(kPrefsUpdateCheckResponseHash, &interrupted_hash) &&
        !interrupted_hash.empty() &&
        interrupted_hash == update_check_response_hash))
    return false;

  int64_t resumed_update_failures;
  // Note that storing this value is optional, but if it is there it should
  // not be more than the limit.
  if (prefs->GetInt64(kPrefsResumedUpdateFailures, &resumed_update_failures) &&
      resumed_update_failures > kMaxResumedUpdateFailures)
    return false;

  // Validation check the rest.
  int64_t next_data_offset = -1;
  if (!(prefs->GetInt64(kPrefsUpdateStateNextDataOffset, &next_data_offset) &&
        next_data_offset >= 0))
    return false;

  string sha256_context;
  if (!(prefs->GetString(kPrefsUpdateStateSHA256Context, &sha256_context) &&
        !sha256_context.empty()))
    return false;

  int64_t manifest_metadata_size = 0;
  if (!(prefs->GetInt64(kPrefsManifestMetadataSize, &manifest_metadata_size) &&
        manifest_metadata_size > 0))
    return false;

  int64_t manifest_signature_size = 0;
  if (!(prefs->GetInt64(kPrefsManifestSignatureSize,
                        &manifest_signature_size) &&
        manifest_signature_size >= 0))
    return false;

  return true;
}

bool DeltaPerformer::ResetUpdateProgress(
    PrefsInterface* prefs,
    bool quick,
    bool skip_dynamic_partititon_metadata_updated) {
  TEST_AND_RETURN_FALSE(prefs->SetInt64(kPrefsUpdateStateNextOperation,
                                        kUpdateStateOperationInvalid));
  if (!quick) {
    prefs->SetInt64(kPrefsUpdateStateNextDataOffset, -1);
    prefs->SetInt64(kPrefsUpdateStateNextDataLength, 0);
    prefs->SetString(kPrefsUpdateStateSHA256Context, "");
    prefs->SetString(kPrefsUpdateStateSignedSHA256Context, "");
    prefs->SetString(kPrefsUpdateStateSignatureBlob, "");
    prefs->SetInt64(kPrefsManifestMetadataSize, -1);
    prefs->SetInt64(kPrefsManifestSignatureSize, -1);
    prefs->SetInt64(kPrefsResumedUpdateFailures, 0);
    prefs->Delete(kPrefsPostInstallSucceeded);
    prefs->Delete(kPrefsVerityWritten);

    if (!skip_dynamic_partititon_metadata_updated) {
      LOG(INFO) << "Resetting recorded hash for prepared partitions.";
      prefs->Delete(kPrefsDynamicPartitionMetadataUpdated);
    }
  }
  return true;
}

bool DeltaPerformer::ShouldCheckpoint() {
  base::TimeTicks curr_time = base::TimeTicks::Now();
  if (curr_time > update_checkpoint_time_) {
    update_checkpoint_time_ = curr_time + update_checkpoint_wait_;
    return true;
  }
  return false;
}

bool DeltaPerformer::CheckpointUpdateProgress(bool force) {
  if (!force && !ShouldCheckpoint()) {
    return false;
  }
  Terminator::set_exit_blocked(true);
  if (last_updated_operation_num_ != next_operation_num_ || force) {
    // Resets the progress in case we die in the middle of the state update.
    ResetUpdateProgress(prefs_, true);
    if (!signatures_message_data_.empty()) {
      // Save the signature blob because if the update is interrupted after the
      // download phase we don't go through this path anymore. Some alternatives
      // to consider:
      //
      // 1. On resume, re-download the signature blob from the server and
      // re-verify it.
      //
      // 2. Verify the signature as soon as it's received and don't checkpoint
      // the blob and the signed sha-256 context.
      LOG_IF(WARNING,
             !prefs_->SetString(kPrefsUpdateStateSignatureBlob,
                                signatures_message_data_))
          << "Unable to store the signature blob.";
    }
    TEST_AND_RETURN_FALSE(prefs_->SetString(
        kPrefsUpdateStateSHA256Context, payload_hash_calculator_.GetContext()));
    TEST_AND_RETURN_FALSE(
        prefs_->SetString(kPrefsUpdateStateSignedSHA256Context,
                          signed_hash_calculator_.GetContext()));
    TEST_AND_RETURN_FALSE(
        prefs_->SetInt64(kPrefsUpdateStateNextDataOffset, buffer_offset_));
    last_updated_operation_num_ = next_operation_num_;

    if (next_operation_num_ < num_total_operations_) {
      size_t partition_index = current_partition_;
      while (next_operation_num_ >= acc_num_operations_[partition_index]) {
        partition_index++;
      }
      const size_t partition_operation_num =
          next_operation_num_ -
          (partition_index ? acc_num_operations_[partition_index - 1] : 0);
      const InstallOperation& op =
          partitions_[partition_index].operations(partition_operation_num);
      TEST_AND_RETURN_FALSE(
          prefs_->SetInt64(kPrefsUpdateStateNextDataLength, op.data_length()));
    } else {
      TEST_AND_RETURN_FALSE(
          prefs_->SetInt64(kPrefsUpdateStateNextDataLength, 0));
    }
    if (partition_writer_) {
      partition_writer_->CheckpointUpdateProgress(GetPartitionOperationNum());
    } else {
      CHECK_EQ(next_operation_num_, num_total_operations_)
          << "Partition writer is null, we are expected to finish all "
             "operations: "
          << next_operation_num_ << "/" << num_total_operations_;
    }
  }
  TEST_AND_RETURN_FALSE(
      prefs_->SetInt64(kPrefsUpdateStateNextOperation, next_operation_num_));
  return true;
}

bool DeltaPerformer::PrimeUpdateState() {
  CHECK(manifest_valid_);

  int64_t next_operation = kUpdateStateOperationInvalid;
  if (!prefs_->GetInt64(kPrefsUpdateStateNextOperation, &next_operation) ||
      next_operation == kUpdateStateOperationInvalid || next_operation <= 0) {
    // Initiating a new update, no more state needs to be initialized.
    return true;
  }
  next_operation_num_ = next_operation;

  // Resuming an update -- load the rest of the update state.
  int64_t next_data_offset = -1;
  TEST_AND_RETURN_FALSE(
      prefs_->GetInt64(kPrefsUpdateStateNextDataOffset, &next_data_offset) &&
      next_data_offset >= 0);
  buffer_offset_ = next_data_offset;

  // The signed hash context and the signature blob may be empty if the
  // interrupted update didn't reach the signature.
  string signed_hash_context;
  if (prefs_->GetString(kPrefsUpdateStateSignedSHA256Context,
                        &signed_hash_context)) {
    TEST_AND_RETURN_FALSE(
        signed_hash_calculator_.SetContext(signed_hash_context));
  }

  prefs_->GetString(kPrefsUpdateStateSignatureBlob, &signatures_message_data_);

  string hash_context;
  TEST_AND_RETURN_FALSE(
      prefs_->GetString(kPrefsUpdateStateSHA256Context, &hash_context) &&
      payload_hash_calculator_.SetContext(hash_context));

  int64_t manifest_metadata_size = 0;
  TEST_AND_RETURN_FALSE(
      prefs_->GetInt64(kPrefsManifestMetadataSize, &manifest_metadata_size) &&
      manifest_metadata_size > 0);
  metadata_size_ = manifest_metadata_size;

  int64_t manifest_signature_size = 0;
  TEST_AND_RETURN_FALSE(
      prefs_->GetInt64(kPrefsManifestSignatureSize, &manifest_signature_size) &&
      manifest_signature_size >= 0);
  metadata_signature_size_ = manifest_signature_size;

  // Advance the download progress to reflect what doesn't need to be
  // re-downloaded.
  total_bytes_received_ += buffer_offset_;

  // Speculatively count the resume as a failure.
  int64_t resumed_update_failures;
  if (prefs_->GetInt64(kPrefsResumedUpdateFailures, &resumed_update_failures)) {
    resumed_update_failures++;
  } else {
    resumed_update_failures = 1;
  }
  prefs_->SetInt64(kPrefsResumedUpdateFailures, resumed_update_failures);
  return true;
}

bool DeltaPerformer::IsDynamicPartition(const std::string& part_name,
                                        uint32_t slot) {
  return boot_control_->GetDynamicPartitionControl()->IsDynamicPartition(
      part_name, slot);
}

std::unique_ptr<PartitionWriterInterface> DeltaPerformer::CreatePartitionWriter(
    const PartitionUpdate& partition_update,
    const InstallPlan::Partition& install_part,
    DynamicPartitionControlInterface* dynamic_control,
    size_t block_size,
    bool is_interactive,
    bool is_dynamic_partition) {
  return partition_writer::CreatePartitionWriter(
      partition_update,
      install_part,
      dynamic_control,
      block_size_,
      interactive_,
      IsDynamicPartition(install_part.name, install_plan_->target_slot));
}

}  // namespace chromeos_update_engine