Split payload application code into a subdirectory.

This patch splits from the main libupdate_engine code the part that
is strictly used to download and apply a payload into a new static
library, moving the code to subdirectories. The new library is divided
in two subdirectories: common/ and payload_consumer/, and should not
depend on other update_engine files outside those two subdirectories.
The main difference between those two is that the common/ tools are more
generic and not tied to the payload consumer process, but otherwise they
are both compiled together.

There are still dependencies from the new libpayload_consumer library
into the main directory files and DBus generated files. Those will be
addressed in follow up CLs.

Bug: 25197634
Test: FEATURES=test emerge-link update_engine; `mm` on Brillo.

Change-Id: Id8d0204ea573627e6e26ca9ea17b9592ca95bc23
diff --git a/payload_consumer/delta_performer.cc b/payload_consumer/delta_performer.cc
new file mode 100644
index 0000000..1df5214
--- /dev/null
+++ b/payload_consumer/delta_performer.cc
@@ -0,0 +1,1744 @@
+//
+// 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 <endian.h>
+#include <errno.h>
+#include <linux/fs.h>
+
+#include <algorithm>
+#include <cstring>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <base/files/file_util.h>
+#include <base/format_macros.h>
+#include <base/strings/string_util.h>
+#include <base/strings/stringprintf.h>
+#include <brillo/data_encoding.h>
+#include <brillo/make_unique_ptr.h>
+#include <google/protobuf/repeated_field.h>
+
+#include "update_engine/common/constants.h"
+#include "update_engine/common/hardware_interface.h"
+#include "update_engine/payload_consumer/bzip_extent_writer.h"
+#include "update_engine/payload_consumer/extent_writer.h"
+#if USE_MTD
+#include "update_engine/payload_consumer/mtd_file_descriptor.h"
+#endif
+#include "update_engine/common/prefs_interface.h"
+#include "update_engine/common/subprocess.h"
+#include "update_engine/common/terminator.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"
+#include "update_engine/payload_state_interface.h"
+#include "update_engine/update_attempter.h"
+
+using google::protobuf::RepeatedPtrField;
+using std::min;
+using std::string;
+using std::vector;
+
+namespace chromeos_update_engine {
+
+const uint64_t DeltaPerformer::kDeltaVersionOffset = sizeof(kDeltaMagic);
+const uint64_t DeltaPerformer::kDeltaVersionSize = 8;
+const uint64_t DeltaPerformer::kDeltaManifestSizeOffset =
+    kDeltaVersionOffset + kDeltaVersionSize;
+const uint64_t DeltaPerformer::kDeltaManifestSizeSize = 8;
+const uint64_t DeltaPerformer::kDeltaMetadataSignatureSizeSize = 4;
+const uint64_t DeltaPerformer::kMaxPayloadHeaderSize = 24;
+const uint64_t DeltaPerformer::kSupportedMajorPayloadVersion = 2;
+const uint32_t DeltaPerformer::kSupportedMinorPayloadVersion = 2;
+
+const unsigned DeltaPerformer::kProgressLogMaxChunks = 10;
+const unsigned DeltaPerformer::kProgressLogTimeoutSeconds = 30;
+const unsigned DeltaPerformer::kProgressDownloadWeight = 50;
+const unsigned DeltaPerformer::kProgressOperationsWeight = 50;
+
+namespace {
+const int kUpdateStateOperationInvalid = -1;
+const int kMaxResumedUpdateFailures = 10;
+#if USE_MTD
+const int kUbiVolumeAttachTimeout = 5 * 60;
+#endif
+
+FileDescriptorPtr CreateFileDescriptor(const char* path) {
+  FileDescriptorPtr ret;
+#if USE_MTD
+  if (strstr(path, "/dev/ubi") == path) {
+    if (!UbiFileDescriptor::IsUbi(path)) {
+      // The volume might not have been attached at boot time.
+      int volume_no;
+      if (utils::SplitPartitionName(path, nullptr, &volume_no)) {
+        utils::TryAttachingUbiVolume(volume_no, kUbiVolumeAttachTimeout);
+      }
+    }
+    if (UbiFileDescriptor::IsUbi(path)) {
+      LOG(INFO) << path << " is a UBI device.";
+      ret.reset(new UbiFileDescriptor);
+    }
+  } else if (MtdFileDescriptor::IsMtd(path)) {
+    LOG(INFO) << path << " is an MTD device.";
+    ret.reset(new MtdFileDescriptor);
+  } else {
+    LOG(INFO) << path << " is not an MTD nor a UBI device.";
+#endif
+    ret.reset(new EintrSafeFileDescriptor);
+#if USE_MTD
+  }
+#endif
+  return ret;
+}
+
+// Opens path for read/write. On success returns an open FileDescriptor
+// and sets *err to 0. On failure, sets *err to errno and returns nullptr.
+FileDescriptorPtr OpenFile(const char* path, int mode, int* err) {
+  FileDescriptorPtr fd = CreateFileDescriptor(path);
+#if USE_MTD
+  // On NAND devices, we can either read, or write, but not both. So here we
+  // use O_WRONLY.
+  if (UbiFileDescriptor::IsUbi(path) || MtdFileDescriptor::IsMtd(path)) {
+    mode = O_WRONLY;
+  }
+#endif
+  if (!fd->Open(path, mode, 000)) {
+    *err = errno;
+    PLOG(ERROR) << "Unable to open file " << path;
+    return nullptr;
+  }
+  *err = 0;
+  return fd;
+}
+}  // 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 = install_plan_->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;
+  COMPILE_ASSERT(kProgressDownloadWeight + kProgressOperationsWeight == 100,
+                 progress_weight_dont_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 = install_plan_->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::Time curr_time = base::Time::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_.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_;
+  *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() {
+  int err = 0;
+  if (source_fd_ && !source_fd_->Close()) {
+    err = errno;
+    PLOG(ERROR) << "Error closing source partition";
+    if (!err)
+      err = 1;
+  }
+  source_fd_.reset();
+  source_path_.clear();
+
+  if (target_fd_ && !target_fd_->Close()) {
+    err = errno;
+    PLOG(ERROR) << "Error closing target partition";
+    if (!err)
+      err = 1;
+  }
+  target_fd_.reset();
+  target_path_.clear();
+  return -err;
+}
+
+bool DeltaPerformer::OpenCurrentPartition() {
+  if (current_partition_ >= partitions_.size())
+    return false;
+
+  const PartitionUpdate& partition = partitions_[current_partition_];
+  // Open source fds if we have a delta payload with minor version 2.
+  if (!install_plan_->is_full_update &&
+      GetMinorVersion() == kSourceMinorPayloadVersion) {
+    source_path_ = install_plan_->partitions[current_partition_].source_path;
+    int err;
+    source_fd_ = OpenFile(source_path_.c_str(), O_RDONLY, &err);
+    if (!source_fd_) {
+      LOG(ERROR) << "Unable to open source partition "
+                 << partition.partition_name() << " on slot "
+                 << BootControlInterface::SlotName(install_plan_->source_slot)
+                 << ", file " << source_path_;
+      return false;
+    }
+  }
+
+  target_path_ = install_plan_->partitions[current_partition_].target_path;
+  int err;
+  target_fd_ = OpenFile(target_path_.c_str(), O_RDWR, &err);
+  if (!target_fd_) {
+    LOG(ERROR) << "Unable to open target partition "
+               << partition.partition_name() << " on slot "
+               << BootControlInterface::SlotName(install_plan_->target_slot)
+               << ", file " << target_path_;
+    return false;
+  }
+  return true;
+}
+
+namespace {
+
+void LogPartitionInfoHash(const PartitionInfo& info, const string& tag) {
+  string sha256 = brillo::data_encoding::Base64Encode(info.hash());
+  LOG(INFO) << "PartitionInfo " << tag << " sha256: " << sha256
+            << " size: " << info.size();
+}
+
+void LogPartitionInfo(const vector<PartitionUpdate>& partitions) {
+  for (const PartitionUpdate& partition : partitions) {
+    LogPartitionInfoHash(partition.old_partition_info(),
+                         "old " + partition.partition_name());
+    LogPartitionInfoHash(partition.new_partition_info(),
+                         "new " + partition.partition_name());
+  }
+}
+
+}  // namespace
+
+bool DeltaPerformer::GetMetadataSignatureSizeOffset(
+    uint64_t* out_offset) const {
+  if (GetMajorVersion() == kBrilloMajorPayloadVersion) {
+    *out_offset = kDeltaManifestSizeOffset + kDeltaManifestSizeSize;
+    return true;
+  }
+  return false;
+}
+
+bool DeltaPerformer::GetManifestOffset(uint64_t* out_offset) const {
+  // Actual manifest begins right after the manifest size field or
+  // metadata signature size field if major version >= 2.
+  if (major_payload_version_ == kChromeOSMajorPayloadVersion) {
+    *out_offset = kDeltaManifestSizeOffset + kDeltaManifestSizeSize;
+    return true;
+  }
+  if (major_payload_version_ == kBrilloMajorPayloadVersion) {
+    *out_offset = kDeltaManifestSizeOffset + kDeltaManifestSizeSize +
+                  kDeltaMetadataSignatureSizeSize;
+    return true;
+  }
+  LOG(ERROR) << "Unknown major payload version: " << major_payload_version_;
+  return false;
+}
+
+uint64_t DeltaPerformer::GetMetadataSize() const {
+  return metadata_size_;
+}
+
+uint64_t DeltaPerformer::GetMajorVersion() const {
+  return major_payload_version_;
+}
+
+uint32_t DeltaPerformer::GetMinorVersion() const {
+  if (manifest_.has_minor_version()) {
+    return manifest_.minor_version();
+  } else {
+    return (install_plan_->is_full_update ?
+            kFullPayloadMinorVersion :
+            kSupportedMinorPayloadVersion);
+  }
+}
+
+bool DeltaPerformer::GetManifest(DeltaArchiveManifest* out_manifest_p) const {
+  if (!manifest_parsed_)
+    return false;
+  *out_manifest_p = manifest_;
+  return true;
+}
+
+bool DeltaPerformer::IsHeaderParsed() const {
+  return metadata_size_ != 0;
+}
+
+DeltaPerformer::MetadataParseResult DeltaPerformer::ParsePayloadMetadata(
+    const brillo::Blob& payload, ErrorCode* error) {
+  *error = ErrorCode::kSuccess;
+  uint64_t manifest_offset;
+
+  if (!IsHeaderParsed()) {
+    // Ensure we have data to cover the major payload version.
+    if (payload.size() < kDeltaManifestSizeOffset)
+      return kMetadataParseInsufficientData;
+
+    // Validate the magic string.
+    if (memcmp(payload.data(), kDeltaMagic, sizeof(kDeltaMagic)) != 0) {
+      LOG(ERROR) << "Bad payload format -- invalid delta magic.";
+      *error = ErrorCode::kDownloadInvalidMetadataMagicString;
+      return kMetadataParseError;
+    }
+
+    // Extract the payload version from the metadata.
+    COMPILE_ASSERT(sizeof(major_payload_version_) == kDeltaVersionSize,
+                   major_payload_version_size_mismatch);
+    memcpy(&major_payload_version_,
+           &payload[kDeltaVersionOffset],
+           kDeltaVersionSize);
+    // switch big endian to host
+    major_payload_version_ = be64toh(major_payload_version_);
+
+    if (major_payload_version_ != supported_major_version_ &&
+        major_payload_version_ != kChromeOSMajorPayloadVersion) {
+      LOG(ERROR) << "Bad payload format -- unsupported payload version: "
+          << major_payload_version_;
+      *error = ErrorCode::kUnsupportedMajorPayloadVersion;
+      return kMetadataParseError;
+    }
+
+    // Get the manifest offset now that we have payload version.
+    if (!GetManifestOffset(&manifest_offset)) {
+      *error = ErrorCode::kUnsupportedMajorPayloadVersion;
+      return kMetadataParseError;
+    }
+    // Check again with the manifest offset.
+    if (payload.size() < manifest_offset)
+      return kMetadataParseInsufficientData;
+
+    // Next, parse the manifest size.
+    COMPILE_ASSERT(sizeof(manifest_size_) == kDeltaManifestSizeSize,
+                   manifest_size_size_mismatch);
+    memcpy(&manifest_size_,
+           &payload[kDeltaManifestSizeOffset],
+           kDeltaManifestSizeSize);
+    manifest_size_ = be64toh(manifest_size_);  // switch big endian to host
+
+    if (GetMajorVersion() == kBrilloMajorPayloadVersion) {
+      // Parse the metadata signature size.
+      COMPILE_ASSERT(sizeof(metadata_signature_size_) ==
+                     kDeltaMetadataSignatureSizeSize,
+                     metadata_signature_size_size_mismatch);
+      uint64_t metadata_signature_size_offset;
+      if (!GetMetadataSignatureSizeOffset(&metadata_signature_size_offset)) {
+        *error = ErrorCode::kError;
+        return kMetadataParseError;
+      }
+      memcpy(&metadata_signature_size_,
+             &payload[metadata_signature_size_offset],
+             kDeltaMetadataSignatureSizeSize);
+      metadata_signature_size_ = be32toh(metadata_signature_size_);
+    }
+
+    // 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.
+    metadata_size_ = manifest_offset + manifest_size_;
+    if (install_plan_->hash_checks_mandatory) {
+      if (install_plan_->metadata_size != metadata_size_) {
+        LOG(ERROR) << "Mandatory metadata size in Omaha response ("
+                   << install_plan_->metadata_size
+                   << ") is missing/incorrect, actual = " << metadata_size_;
+        *error = ErrorCode::kDownloadInvalidMetadataSize;
+        return kMetadataParseError;
+      }
+    }
+  }
+
+  // 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 kMetadataParseInsufficientData;
+
+  // 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 (install_plan_->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 ("
+                 << install_plan_->metadata_size
+                 << ") in Omaha response as validation is not mandatory. "
+                 << "Trusting metadata size in payload = " << metadata_size_;
+  }
+
+  // We have the full metadata in |payload|. Verify its integrity
+  // and authenticity based on the information we have in Omaha response.
+  *error = ValidateMetadataSignature(payload);
+  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 kMetadataParseError;
+    }
+
+    // For non-mandatory cases, just send a UMA stat.
+    LOG(WARNING) << "Ignoring metadata signature validation failures";
+    *error = ErrorCode::kSuccess;
+  }
+
+  if (!GetManifestOffset(&manifest_offset)) {
+    *error = ErrorCode::kUnsupportedMajorPayloadVersion;
+    return kMetadataParseError;
+  }
+  // The payload metadata is deemed valid, it's safe to parse the protobuf.
+  if (!manifest_.ParseFromArray(&payload[manifest_offset], manifest_size_)) {
+    LOG(ERROR) << "Unable to parse manifest in update file.";
+    *error = ErrorCode::kDownloadManifestParseError;
+    return kMetadataParseError;
+  }
+
+  manifest_parsed_ = true;
+  return kMetadataParseSuccess;
+}
+
+// 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);
+  system_state_->payload_state()->DownloadProgress(count);
+
+  // 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 == kMetadataParseError)
+      return false;
+    if (result == kMetadataParseInsufficientData) {
+      // 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;
+
+    // Clear the download buffer.
+    DiscardBuffer(false, metadata_size_);
+
+    // This populates |partitions_| and the |install_plan.partitions| with the
+    // list of partitions from the manifest.
+    if (!ParseManifestPartitions(error))
+      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.";
+
+    if (!PrimeUpdateState()) {
+      *error = ErrorCode::kDownloadStateInitializationError;
+      LOG(ERROR) << "Unable to prime the update state.";
+      return false;
+    }
+
+    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 (system_state_->update_attempter()->ShouldCancel(error))
+      return false;
+
+    // We know there are more operations to perform because we didn't reach the
+    // |num_total_operations_| limit yet.
+    while (next_operation_num_ >= acc_num_operations_[current_partition_]) {
+      CloseCurrentPartition();
+      current_partition_++;
+      if (!OpenCurrentPartition()) {
+        *error = ErrorCode::kInstallDeviceOpenError;
+        return false;
+      }
+    }
+    const size_t partition_operation_num = next_operation_num_ - (
+        current_partition_ ? acc_num_operations_[current_partition_ - 1] : 0);
+
+    const InstallOperation& op =
+        partitions_[current_partition_].operations(partition_operation_num);
+
+    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 only if the metadata signature is present.
+    // Otherwise, keep the old behavior. This serves as a knob to disable
+    // the validation logic in case we find some regression after rollout.
+    // NOTE: If hash checks are mandatory and if metadata_signature is empty,
+    // we would have already failed in ParsePayloadMetadata method and thus not
+    // even be here. So no need to handle that case again here.
+    if (!install_plan_->metadata_signature.empty()) {
+      // 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.
+
+    bool op_result;
+    switch (op.type()) {
+      case InstallOperation::REPLACE:
+      case InstallOperation::REPLACE_BZ:
+      case InstallOperation::REPLACE_XZ:
+        op_result = PerformReplaceOperation(op);
+        break;
+      case InstallOperation::ZERO:
+      case InstallOperation::DISCARD:
+        op_result = PerformZeroOrDiscardOperation(op);
+        break;
+      case InstallOperation::MOVE:
+        op_result = PerformMoveOperation(op);
+        break;
+      case InstallOperation::BSDIFF:
+        op_result = PerformBsdiffOperation(op);
+        break;
+      case InstallOperation::SOURCE_COPY:
+        op_result = PerformSourceCopyOperation(op);
+        break;
+      case InstallOperation::SOURCE_BSDIFF:
+        op_result = PerformSourceBsdiffOperation(op);
+        break;
+      default:
+       op_result = false;
+    }
+    if (!HandleOpResult(op_result, InstallOperationTypeName(op.type()), error))
+      return false;
+
+    next_operation_num_++;
+    UpdateOverallProgress(false, "Completed ");
+    CheckpointUpdateProgress();
+  }
+
+  // In major version 2, we don't add dummy operation to the payload.
+  if (major_payload_version_ == kBrilloMajorPayloadVersion &&
+      manifest_.has_signatures_offset() && manifest_.has_signatures_size()) {
+    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);
+  }
+
+  return true;
+}
+
+bool DeltaPerformer::IsManifestValid() {
+  return manifest_valid_;
+}
+
+bool DeltaPerformer::ParseManifestPartitions(ErrorCode* error) {
+  if (major_payload_version_ == kBrilloMajorPayloadVersion) {
+    partitions_.clear();
+    for (const PartitionUpdate& partition : manifest_.partitions()) {
+      partitions_.push_back(partition);
+    }
+    manifest_.clear_partitions();
+  } else if (major_payload_version_ == kChromeOSMajorPayloadVersion) {
+    LOG(INFO) << "Converting update information from old format.";
+    PartitionUpdate root_part;
+    root_part.set_partition_name(kLegacyPartitionNameRoot);
+#ifdef __ANDROID__
+    LOG(WARNING) << "Legacy payload major version provided to an Android "
+                    "build. Assuming no post-install. Please use major version "
+                    "2 or newer.";
+    root_part.set_run_postinstall(false);
+#else
+    root_part.set_run_postinstall(true);
+#endif  // __ANDROID__
+    if (manifest_.has_old_rootfs_info()) {
+      *root_part.mutable_old_partition_info() = manifest_.old_rootfs_info();
+      manifest_.clear_old_rootfs_info();
+    }
+    if (manifest_.has_new_rootfs_info()) {
+      *root_part.mutable_new_partition_info() = manifest_.new_rootfs_info();
+      manifest_.clear_new_rootfs_info();
+    }
+    *root_part.mutable_operations() = manifest_.install_operations();
+    manifest_.clear_install_operations();
+    partitions_.push_back(std::move(root_part));
+
+    PartitionUpdate kern_part;
+    kern_part.set_partition_name(kLegacyPartitionNameKernel);
+    kern_part.set_run_postinstall(false);
+    if (manifest_.has_old_kernel_info()) {
+      *kern_part.mutable_old_partition_info() = manifest_.old_kernel_info();
+      manifest_.clear_old_kernel_info();
+    }
+    if (manifest_.has_new_kernel_info()) {
+      *kern_part.mutable_new_partition_info() = manifest_.new_kernel_info();
+      manifest_.clear_new_kernel_info();
+    }
+    *kern_part.mutable_operations() = manifest_.kernel_install_operations();
+    manifest_.clear_kernel_install_operations();
+    partitions_.push_back(std::move(kern_part));
+  }
+
+  // TODO(deymo): Remove this block of code once we switched to optional
+  // source partition verification. This list of partitions in the InstallPlan
+  // is initialized with the expected hashes in the payload major version 1,
+  // so we need to check those now if already set. See b/23182225.
+  if (!install_plan_->partitions.empty()) {
+    if (!VerifySourcePartitions()) {
+      *error = ErrorCode::kDownloadStateInitializationError;
+      return false;
+    }
+  }
+
+  // Fill in the InstallPlan::partitions based on the partitions from the
+  // payload.
+  install_plan_->partitions.clear();
+  for (const auto& partition : partitions_) {
+    InstallPlan::Partition install_part;
+    install_part.name = partition.partition_name();
+    install_part.run_postinstall =
+        partition.has_run_postinstall() && partition.run_postinstall();
+
+    if (partition.has_old_partition_info()) {
+      const PartitionInfo& info = partition.old_partition_info();
+      install_part.source_size = info.size();
+      install_part.source_hash.assign(info.hash().begin(), info.hash().end());
+    }
+
+    if (!partition.has_new_partition_info()) {
+      LOG(ERROR) << "Unable to get new partition hash info on partition "
+                 << install_part.name << ".";
+      *error = ErrorCode::kDownloadNewPartitionInfoError;
+      return false;
+    }
+    const PartitionInfo& info = partition.new_partition_info();
+    install_part.target_size = info.size();
+    install_part.target_hash.assign(info.hash().begin(), info.hash().end());
+
+    install_plan_->partitions.push_back(install_part);
+  }
+
+  if (!install_plan_->LoadPartitionsFromSlots(system_state_)) {
+    LOG(ERROR) << "Unable to determine all the partition devices.";
+    *error = ErrorCode::kInstallDeviceOpenError;
+    return false;
+  }
+  LogPartitionInfo(partitions_);
+  return true;
+}
+
+bool DeltaPerformer::CanPerformInstallOperation(
+    const chromeos_update_engine::InstallOperation& operation) {
+  // Move and source_copy operations don't require any data blob, so they can
+  // always be performed.
+  if (operation.type() == InstallOperation::MOVE ||
+      operation.type() == InstallOperation::SOURCE_COPY)
+    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_offset_ == operation.data_offset());
+  TEST_AND_RETURN_FALSE(buffer_.size() >= operation.data_length());
+
+  // Extract the signature message if it's in this operation.
+  if (ExtractSignatureMessageFromOperation(operation)) {
+    // If this is dummy replace operation, we ignore it after extracting the
+    // signature.
+    DiscardBuffer(true, 0);
+    return true;
+  }
+
+  // Setup the ExtentWriter stack based on the operation type.
+  std::unique_ptr<ExtentWriter> writer =
+    brillo::make_unique_ptr(new ZeroPadExtentWriter(
+      brillo::make_unique_ptr(new DirectExtentWriter())));
+
+  if (operation.type() == InstallOperation::REPLACE_BZ) {
+    writer.reset(new BzipExtentWriter(std::move(writer)));
+  } else if (operation.type() == InstallOperation::REPLACE_XZ) {
+    writer.reset(new XzExtentWriter(std::move(writer)));
+  }
+
+  // Create a vector of extents to pass to the ExtentWriter.
+  vector<Extent> extents;
+  for (int i = 0; i < operation.dst_extents_size(); i++) {
+    extents.push_back(operation.dst_extents(i));
+  }
+
+  TEST_AND_RETURN_FALSE(writer->Init(target_fd_, extents, block_size_));
+  TEST_AND_RETURN_FALSE(writer->Write(buffer_.data(), operation.data_length()));
+  TEST_AND_RETURN_FALSE(writer->End());
+
+  // 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());
+
+  int request =
+      (operation.type() == InstallOperation::ZERO ? BLKZEROOUT : BLKDISCARD);
+
+  bool attempt_ioctl = true;
+  brillo::Blob zeros;
+  for (int i = 0; i < operation.dst_extents_size(); i++) {
+    Extent extent = operation.dst_extents(i);
+    const uint64_t start = extent.start_block() * block_size_;
+    const uint64_t length = extent.num_blocks() * block_size_;
+    if (attempt_ioctl) {
+      int result = 0;
+      if (target_fd_->BlkIoctl(request, start, length, &result) && result == 0)
+        continue;
+      attempt_ioctl = false;
+      zeros.resize(16 * block_size_);
+    }
+    // In case of failure, we fall back to writing 0 to the selected region.
+    for (uint64_t offset = 0; offset < length; offset += zeros.size()) {
+      uint64_t chunk_length = min(length - offset,
+                                  static_cast<uint64_t>(zeros.size()));
+      TEST_AND_RETURN_FALSE(
+          utils::PWriteAll(target_fd_, zeros.data(), chunk_length, start + offset));
+    }
+  }
+  return true;
+}
+
+bool DeltaPerformer::PerformMoveOperation(const InstallOperation& operation) {
+  // Calculate buffer size. Note, this function doesn't do a sliding
+  // window to copy in case the source and destination blocks overlap.
+  // If we wanted to do a sliding window, we could program the server
+  // to generate deltas that effectively did a sliding window.
+
+  uint64_t blocks_to_read = 0;
+  for (int i = 0; i < operation.src_extents_size(); i++)
+    blocks_to_read += operation.src_extents(i).num_blocks();
+
+  uint64_t blocks_to_write = 0;
+  for (int i = 0; i < operation.dst_extents_size(); i++)
+    blocks_to_write += operation.dst_extents(i).num_blocks();
+
+  DCHECK_EQ(blocks_to_write, blocks_to_read);
+  brillo::Blob buf(blocks_to_write * block_size_);
+
+  // Read in bytes.
+  ssize_t bytes_read = 0;
+  for (int i = 0; i < operation.src_extents_size(); i++) {
+    ssize_t bytes_read_this_iteration = 0;
+    const Extent& extent = operation.src_extents(i);
+    const size_t bytes = extent.num_blocks() * block_size_;
+    TEST_AND_RETURN_FALSE(extent.start_block() != kSparseHole);
+    TEST_AND_RETURN_FALSE(utils::PReadAll(target_fd_,
+                                          &buf[bytes_read],
+                                          bytes,
+                                          extent.start_block() * block_size_,
+                                          &bytes_read_this_iteration));
+    TEST_AND_RETURN_FALSE(
+        bytes_read_this_iteration == static_cast<ssize_t>(bytes));
+    bytes_read += bytes_read_this_iteration;
+  }
+
+  // Write bytes out.
+  ssize_t bytes_written = 0;
+  for (int i = 0; i < operation.dst_extents_size(); i++) {
+    const Extent& extent = operation.dst_extents(i);
+    const size_t bytes = extent.num_blocks() * block_size_;
+    TEST_AND_RETURN_FALSE(extent.start_block() != kSparseHole);
+    TEST_AND_RETURN_FALSE(utils::PWriteAll(target_fd_,
+                                           &buf[bytes_written],
+                                           bytes,
+                                           extent.start_block() * block_size_));
+    bytes_written += bytes;
+  }
+  DCHECK_EQ(bytes_written, bytes_read);
+  DCHECK_EQ(bytes_written, static_cast<ssize_t>(buf.size()));
+  return true;
+}
+
+namespace {
+
+// Takes |extents| and fills an empty vector |blocks| with a block index for
+// each block in |extents|. For example, [(3, 2), (8, 1)] would give [3, 4, 8].
+void ExtentsToBlocks(const RepeatedPtrField<Extent>& extents,
+                     vector<uint64_t>* blocks) {
+  for (Extent ext : extents) {
+    for (uint64_t j = 0; j < ext.num_blocks(); j++)
+      blocks->push_back(ext.start_block() + j);
+  }
+}
+
+// Takes |extents| and returns the number of blocks in those extents.
+uint64_t GetBlockCount(const RepeatedPtrField<Extent>& extents) {
+  uint64_t sum = 0;
+  for (Extent ext : extents) {
+    sum += ext.num_blocks();
+  }
+  return sum;
+}
+
+}  // namespace
+
+bool DeltaPerformer::PerformSourceCopyOperation(
+    const InstallOperation& operation) {
+  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);
+
+  uint64_t blocks_to_read = GetBlockCount(operation.src_extents());
+  uint64_t blocks_to_write = GetBlockCount(operation.dst_extents());
+  TEST_AND_RETURN_FALSE(blocks_to_write ==  blocks_to_read);
+
+  // Create vectors of all the individual src/dst blocks.
+  vector<uint64_t> src_blocks;
+  vector<uint64_t> dst_blocks;
+  ExtentsToBlocks(operation.src_extents(), &src_blocks);
+  ExtentsToBlocks(operation.dst_extents(), &dst_blocks);
+  DCHECK_EQ(src_blocks.size(), blocks_to_read);
+  DCHECK_EQ(src_blocks.size(), dst_blocks.size());
+
+  brillo::Blob buf(block_size_);
+  ssize_t bytes_read = 0;
+  // Read/write one block at a time.
+  for (uint64_t i = 0; i < blocks_to_read; i++) {
+    ssize_t bytes_read_this_iteration = 0;
+    uint64_t src_block = src_blocks[i];
+    uint64_t dst_block = dst_blocks[i];
+
+    // Read in bytes.
+    TEST_AND_RETURN_FALSE(
+        utils::PReadAll(source_fd_,
+                        buf.data(),
+                        block_size_,
+                        src_block * block_size_,
+                        &bytes_read_this_iteration));
+
+    // Write bytes out.
+    TEST_AND_RETURN_FALSE(
+        utils::PWriteAll(target_fd_,
+                         buf.data(),
+                         block_size_,
+                         dst_block * block_size_));
+
+    bytes_read += bytes_read_this_iteration;
+    TEST_AND_RETURN_FALSE(bytes_read_this_iteration ==
+                          static_cast<ssize_t>(block_size_));
+  }
+  DCHECK_EQ(bytes_read, static_cast<ssize_t>(blocks_to_read * block_size_));
+  return true;
+}
+
+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 (int i = 0; i < extents.size(); i++) {
+    Extent extent = extents.Get(i);
+    int64_t start = extent.start_block() * block_size;
+    uint64_t this_length = min(full_length - length,
+                               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::PerformBsdiffOperation(const InstallOperation& operation) {
+  // 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());
+
+  string input_positions;
+  TEST_AND_RETURN_FALSE(ExtentsToBsdiffPositionsString(operation.src_extents(),
+                                                       block_size_,
+                                                       operation.src_length(),
+                                                       &input_positions));
+  string output_positions;
+  TEST_AND_RETURN_FALSE(ExtentsToBsdiffPositionsString(operation.dst_extents(),
+                                                       block_size_,
+                                                       operation.dst_length(),
+                                                       &output_positions));
+
+  string temp_filename;
+  TEST_AND_RETURN_FALSE(utils::MakeTempFile("au_patch.XXXXXX",
+                                            &temp_filename,
+                                            nullptr));
+  ScopedPathUnlinker path_unlinker(temp_filename);
+  {
+    int fd = open(temp_filename.c_str(), O_WRONLY | O_CREAT | O_TRUNC, 0644);
+    ScopedFdCloser fd_closer(&fd);
+    TEST_AND_RETURN_FALSE(
+        utils::WriteAll(fd, buffer_.data(), operation.data_length()));
+  }
+
+  // Update the buffer to release the patch data memory as soon as the patch
+  // file is written out.
+  DiscardBuffer(true, buffer_.size());
+
+  vector<string> cmd{kBspatchPath, target_path_, target_path_, temp_filename,
+                     input_positions, output_positions};
+
+  int return_code = 0;
+  TEST_AND_RETURN_FALSE(
+      Subprocess::SynchronousExecFlags(cmd, Subprocess::kSearchPath,
+                                       &return_code, nullptr));
+  TEST_AND_RETURN_FALSE(return_code == 0);
+
+  if (operation.dst_length() % block_size_) {
+    // Zero out rest of final block.
+    // TODO(adlr): build this into bspatch; it's more efficient that way.
+    const Extent& last_extent =
+        operation.dst_extents(operation.dst_extents_size() - 1);
+    const uint64_t end_byte =
+        (last_extent.start_block() + last_extent.num_blocks()) * block_size_;
+    const uint64_t begin_byte =
+        end_byte - (block_size_ - operation.dst_length() % block_size_);
+    brillo::Blob zeros(end_byte - begin_byte);
+    TEST_AND_RETURN_FALSE(
+        utils::PWriteAll(target_fd_, zeros.data(), end_byte - begin_byte, begin_byte));
+  }
+  return true;
+}
+
+bool DeltaPerformer::PerformSourceBsdiffOperation(
+    const InstallOperation& operation) {
+  // 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);
+
+  string input_positions;
+  TEST_AND_RETURN_FALSE(ExtentsToBsdiffPositionsString(operation.src_extents(),
+                                                       block_size_,
+                                                       operation.src_length(),
+                                                       &input_positions));
+  string output_positions;
+  TEST_AND_RETURN_FALSE(ExtentsToBsdiffPositionsString(operation.dst_extents(),
+                                                       block_size_,
+                                                       operation.dst_length(),
+                                                       &output_positions));
+
+  string temp_filename;
+  TEST_AND_RETURN_FALSE(utils::MakeTempFile("au_patch.XXXXXX",
+                                            &temp_filename,
+                                            nullptr));
+  ScopedPathUnlinker path_unlinker(temp_filename);
+  {
+    int fd = open(temp_filename.c_str(), O_WRONLY | O_CREAT | O_TRUNC, 0644);
+    ScopedFdCloser fd_closer(&fd);
+    TEST_AND_RETURN_FALSE(
+        utils::WriteAll(fd, buffer_.data(), operation.data_length()));
+  }
+
+  // Update the buffer to release the patch data memory as soon as the patch
+  // file is written out.
+  DiscardBuffer(true, buffer_.size());
+
+  vector<string> cmd{kBspatchPath, source_path_, target_path_, temp_filename,
+                     input_positions, output_positions};
+
+  int return_code = 0;
+  TEST_AND_RETURN_FALSE(
+      Subprocess::SynchronousExecFlags(cmd, Subprocess::kSearchPath,
+                                       &return_code, nullptr));
+  TEST_AND_RETURN_FALSE(return_code == 0);
+  return true;
+}
+
+bool DeltaPerformer::ExtractSignatureMessageFromOperation(
+    const InstallOperation& operation) {
+  if (operation.type() != InstallOperation::REPLACE ||
+      !manifest_.has_signatures_offset() ||
+      manifest_.signatures_offset() != operation.data_offset()) {
+    return false;
+  }
+  TEST_AND_RETURN_FALSE(manifest_.has_signatures_size() &&
+                        manifest_.signatures_size() == operation.data_length());
+  TEST_AND_RETURN_FALSE(ExtractSignatureMessage());
+  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());
+
+  // 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,
+                                     string(signatures_message_data_.begin(),
+                                            signatures_message_data_.end())))
+      << "Unable to store the signature blob.";
+
+  LOG(INFO) << "Extracted signature data of size "
+            << manifest_.signatures_size() << " at "
+            << manifest_.signatures_offset();
+  return true;
+}
+
+bool DeltaPerformer::GetPublicKeyFromResponse(base::FilePath *out_tmp_key) {
+  if (system_state_->hardware()->IsOfficialBuild() ||
+      utils::FileExists(public_key_path_.c_str()) ||
+      install_plan_->public_key_rsa.empty())
+    return false;
+
+  if (!utils::DecodeAndStoreBase64String(install_plan_->public_key_rsa,
+                                         out_tmp_key))
+    return false;
+
+  return true;
+}
+
+ErrorCode DeltaPerformer::ValidateMetadataSignature(
+    const brillo::Blob& payload) {
+  if (payload.size() < metadata_size_ + metadata_signature_size_)
+    return ErrorCode::kDownloadMetadataSignatureError;
+
+  brillo::Blob metadata_signature_blob, metadata_signature_protobuf_blob;
+  if (!install_plan_->metadata_signature.empty()) {
+    // Convert base64-encoded signature to raw bytes.
+    if (!brillo::data_encoding::Base64Decode(
+        install_plan_->metadata_signature, &metadata_signature_blob)) {
+      LOG(ERROR) << "Unable to decode base64 metadata signature: "
+                 << install_plan_->metadata_signature;
+      return ErrorCode::kDownloadMetadataSignatureError;
+    }
+  } else if (major_payload_version_ == kBrilloMajorPayloadVersion) {
+    metadata_signature_protobuf_blob.assign(payload.begin() + metadata_size_,
+                                            payload.begin() + metadata_size_ +
+                                            metadata_signature_size_);
+  }
+
+  if (metadata_signature_blob.empty() &&
+      metadata_signature_protobuf_blob.empty()) {
+    if (install_plan_->hash_checks_mandatory) {
+      LOG(ERROR) << "Missing mandatory metadata signature in both Omaha "
+                 << "response and payload.";
+      return ErrorCode::kDownloadMetadataSignatureMissingError;
+    }
+
+    LOG(WARNING) << "Cannot validate metadata as the signature is empty";
+    return ErrorCode::kSuccess;
+  }
+
+  // See if we should use the public RSA key in the Omaha response.
+  base::FilePath path_to_public_key(public_key_path_);
+  base::FilePath tmp_key;
+  if (GetPublicKeyFromResponse(&tmp_key))
+    path_to_public_key = tmp_key;
+  ScopedPathUnlinker tmp_key_remover(tmp_key.value());
+  if (tmp_key.empty())
+    tmp_key_remover.set_should_remove(false);
+
+  LOG(INFO) << "Verifying metadata hash signature using public key: "
+            << path_to_public_key.value();
+
+  HashCalculator metadata_hasher;
+  metadata_hasher.Update(payload.data(), metadata_size_);
+  if (!metadata_hasher.Finalize()) {
+    LOG(ERROR) << "Unable to compute actual hash of manifest";
+    return ErrorCode::kDownloadMetadataSignatureVerificationError;
+  }
+
+  brillo::Blob calculated_metadata_hash = metadata_hasher.raw_hash();
+  PayloadVerifier::PadRSA2048SHA256Hash(&calculated_metadata_hash);
+  if (calculated_metadata_hash.empty()) {
+    LOG(ERROR) << "Computed actual hash of metadata is empty.";
+    return ErrorCode::kDownloadMetadataSignatureVerificationError;
+  }
+
+  if (!metadata_signature_blob.empty()) {
+    brillo::Blob expected_metadata_hash;
+    if (!PayloadVerifier::GetRawHashFromSignature(metadata_signature_blob,
+                                                  path_to_public_key.value(),
+                                                  &expected_metadata_hash)) {
+      LOG(ERROR) << "Unable to compute expected hash from metadata signature";
+      return ErrorCode::kDownloadMetadataSignatureError;
+    }
+    if (calculated_metadata_hash != expected_metadata_hash) {
+      LOG(ERROR) << "Manifest hash verification failed. Expected hash = ";
+      utils::HexDumpVector(expected_metadata_hash);
+      LOG(ERROR) << "Calculated hash = ";
+      utils::HexDumpVector(calculated_metadata_hash);
+      return ErrorCode::kDownloadMetadataSignatureMismatch;
+    }
+  } else {
+    if (!PayloadVerifier::VerifySignature(metadata_signature_protobuf_blob,
+                                          path_to_public_key.value(),
+                                          calculated_metadata_hash)) {
+      LOG(ERROR) << "Manifest hash verification failed.";
+      return ErrorCode::kDownloadMetadataSignatureMismatch;
+    }
+  }
+
+  // The autoupdate_CatchBadSignatures test checks for this string in
+  // log-files. Keep in sync.
+  LOG(INFO) << "Metadata hash signature matches value in Omaha response.";
+  return ErrorCode::kSuccess;
+}
+
+ErrorCode DeltaPerformer::ValidateManifest() {
+  // Perform assorted checks to sanity check the manifest, make sure it
+  // matches data from other sources, and that it is a supported version.
+  //
+  // TODO(garnold) in general, the presence of an old partition hash should be
+  // the sole indicator for a delta update, as we would generally like update
+  // payloads to be self contained and not assume an Omaha response to tell us
+  // that. However, since this requires some massive reengineering of the update
+  // flow (making filesystem copying happen conditionally only *after*
+  // downloading and parsing of the update manifest) we'll put it off for now.
+  // See chromium-os:7597 for further discussion.
+  if (install_plan_->is_full_update) {
+    if (manifest_.has_old_kernel_info() || manifest_.has_old_rootfs_info()) {
+      LOG(ERROR) << "Purported full payload contains old partition "
+                    "hash(es), aborting update";
+      return ErrorCode::kPayloadMismatchedType;
+    }
+
+    for (const PartitionUpdate& partition : manifest_.partitions()) {
+      if (partition.has_old_partition_info()) {
+        LOG(ERROR) << "Purported full payload contains old partition "
+                      "hash(es), aborting update";
+        return ErrorCode::kPayloadMismatchedType;
+      }
+    }
+
+    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() != supported_minor_version_) {
+      LOG(ERROR) << "Manifest contains minor version "
+                 << manifest_.minor_version()
+                 << " not the supported "
+                 << supported_minor_version_;
+      return ErrorCode::kUnsupportedMinorPayloadVersion;
+    }
+  }
+
+  if (major_payload_version_ != kChromeOSMajorPayloadVersion) {
+    if (manifest_.has_old_rootfs_info() ||
+        manifest_.has_new_rootfs_info() ||
+        manifest_.has_old_kernel_info() ||
+        manifest_.has_new_kernel_info() ||
+        manifest_.install_operations_size() != 0 ||
+        manifest_.kernel_install_operations_size() != 0) {
+      LOG(ERROR) << "Manifest contains deprecated field only supported in "
+                 << "major payload version 1, but the payload major version is "
+                 << major_payload_version_;
+      return ErrorCode::kPayloadMismatchedType;
+    }
+  }
+
+  // TODO(garnold) we should be adding more and more manifest checks, such as
+  // partition boundaries etc (see chromium-os:37661).
+
+  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 dummy 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()));
+
+  HashCalculator operation_hasher;
+  operation_hasher.Update(buffer_.data(), operation.data_length());
+  if (!operation_hasher.Finalize()) {
+    LOG(ERROR) << "Unable to compute actual hash of operation "
+               << next_operation_num_;
+    return ErrorCode::kDownloadOperationHashVerificationError;
+  }
+
+  brillo::Blob calculated_op_hash = operation_hasher.raw_hash();
+  if (calculated_op_hash != expected_op_hash) {
+    LOG(ERROR) << "Hash verification failed for operation "
+               << next_operation_num_ << ". Expected hash = ";
+    utils::HexDumpVector(expected_op_hash);
+    LOG(ERROR) << "Calculated hash over " << operation.data_length()
+               << " bytes at offset: " << operation.data_offset() << " = ";
+    utils::HexDumpVector(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 string& update_check_response_hash,
+    const uint64_t update_check_response_size) {
+
+  // See if we should use the public RSA key in the Omaha response.
+  base::FilePath path_to_public_key(public_key_path_);
+  base::FilePath tmp_key;
+  if (GetPublicKeyFromResponse(&tmp_key))
+    path_to_public_key = tmp_key;
+  ScopedPathUnlinker tmp_key_remover(tmp_key.value());
+  if (tmp_key.empty())
+    tmp_key_remover.set_should_remove(false);
+
+  LOG(INFO) << "Verifying payload using public key: "
+            << path_to_public_key.value();
+
+  // Verifies the download size.
+  TEST_AND_RETURN_VAL(ErrorCode::kPayloadSizeMismatchError,
+                      update_check_response_size ==
+                      metadata_size_ + metadata_signature_size_ +
+                      buffer_offset_);
+
+  // Verifies the payload hash.
+  const string& payload_hash_data = payload_hash_calculator_.hash();
+  TEST_AND_RETURN_VAL(ErrorCode::kDownloadPayloadVerificationError,
+                      !payload_hash_data.empty());
+  TEST_AND_RETURN_VAL(ErrorCode::kPayloadHashMismatchError,
+                      payload_hash_data == update_check_response_hash);
+
+  // Verifies the signed payload hash.
+  if (!utils::FileExists(path_to_public_key.value().c_str())) {
+    LOG(WARNING) << "Not verifying signed delta payload -- missing public key.";
+    return ErrorCode::kSuccess;
+  }
+  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,
+                      PayloadVerifier::PadRSA2048SHA256Hash(&hash_data));
+  TEST_AND_RETURN_VAL(ErrorCode::kDownloadPayloadPubKeyVerificationError,
+                      !hash_data.empty());
+
+  if (!PayloadVerifier::VerifySignature(
+      signatures_message_data_, path_to_public_key.value(), 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.";
+
+  // At this point, we are guaranteed to have downloaded a full payload, i.e
+  // the one whose size matches the size mentioned in Omaha response. If any
+  // errors happen after this, it's likely a problem with the payload itself or
+  // the state of the system and not a problem with the URL or network.  So,
+  // indicate that to the payload state so that AU can backoff appropriately.
+  system_state_->payload_state()->DownloadComplete();
+
+  return ErrorCode::kSuccess;
+}
+
+namespace {
+void LogVerifyError(const string& type,
+                    const string& device,
+                    uint64_t size,
+                    const string& local_hash,
+                    const string& expected_hash) {
+  LOG(ERROR) << "This is a server-side error due to "
+             << "mismatched delta update image!";
+  LOG(ERROR) << "The delta I've been given contains a " << type << " delta "
+             << "update that must be applied over a " << type << " with "
+             << "a specific checksum, but the " << type << " we're starting "
+             << "with doesn't have that checksum! This means that "
+             << "the delta I've been given doesn't match my existing "
+             << "system. The " << type << " partition I have has hash: "
+             << local_hash << " but the update expected me to have "
+             << expected_hash << " .";
+  LOG(INFO) << "To get the checksum of the " << type << " partition run this"
+               "command: dd if=" << device << " bs=1M count=" << size
+            << " iflag=count_bytes 2>/dev/null | openssl dgst -sha256 -binary "
+               "| openssl base64";
+  LOG(INFO) << "To get the checksum of partitions in a bin file, "
+            << "run: .../src/scripts/sha256_partitions.sh .../file.bin";
+}
+
+string StringForHashBytes(const void* bytes, size_t size) {
+  return brillo::data_encoding::Base64Encode(bytes, size);
+}
+}  // namespace
+
+bool DeltaPerformer::VerifySourcePartitions() {
+  LOG(INFO) << "Verifying source partitions.";
+  CHECK(manifest_valid_);
+  CHECK(install_plan_);
+  if (install_plan_->partitions.size() != partitions_.size()) {
+    DLOG(ERROR) << "The list of partitions in the InstallPlan doesn't match the "
+                   "list received in the payload. The InstallPlan has "
+                << install_plan_->partitions.size()
+                << " partitions while the payload has " << partitions_.size()
+                << " partitions.";
+    return false;
+  }
+  for (size_t i = 0; i < partitions_.size(); ++i) {
+    if (partitions_[i].partition_name() != install_plan_->partitions[i].name) {
+      DLOG(ERROR) << "The InstallPlan's partition " << i << " is \""
+                  << install_plan_->partitions[i].name
+                  << "\" but the payload expects it to be \""
+                  << partitions_[i].partition_name()
+                  << "\". This is an error in the DeltaPerformer setup.";
+      return false;
+    }
+    if (!partitions_[i].has_old_partition_info())
+      continue;
+    const PartitionInfo& info = partitions_[i].old_partition_info();
+    const InstallPlan::Partition& plan_part = install_plan_->partitions[i];
+    bool valid =
+        !plan_part.source_hash.empty() &&
+        plan_part.source_hash.size() == info.hash().size() &&
+        memcmp(plan_part.source_hash.data(),
+               info.hash().data(),
+               plan_part.source_hash.size()) == 0;
+    if (!valid) {
+      LogVerifyError(partitions_[i].partition_name(),
+                     plan_part.source_path,
+                     info.hash().size(),
+                     StringForHashBytes(plan_part.source_hash.data(),
+                                        plan_part.source_hash.size()),
+                     StringForHashBytes(info.hash().data(),
+                                        info.hash().size()));
+      return false;
+    }
+  }
+  return true;
+}
+
+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,
+                                     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;
+  if (!(prefs->GetInt64(kPrefsResumedUpdateFailures, &resumed_update_failures)
+        && resumed_update_failures > kMaxResumedUpdateFailures))
+    return false;
+
+  // Sanity 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;
+
+  return true;
+}
+
+bool DeltaPerformer::ResetUpdateProgress(PrefsInterface* prefs, bool quick) {
+  TEST_AND_RETURN_FALSE(prefs->SetInt64(kPrefsUpdateStateNextOperation,
+                                        kUpdateStateOperationInvalid));
+  if (!quick) {
+    prefs->SetString(kPrefsUpdateCheckResponseHash, "");
+    prefs->SetInt64(kPrefsUpdateStateNextDataOffset, -1);
+    prefs->SetInt64(kPrefsUpdateStateNextDataLength, 0);
+    prefs->SetString(kPrefsUpdateStateSHA256Context, "");
+    prefs->SetString(kPrefsUpdateStateSignedSHA256Context, "");
+    prefs->SetString(kPrefsUpdateStateSignatureBlob, "");
+    prefs->SetInt64(kPrefsManifestMetadataSize, -1);
+    prefs->SetInt64(kPrefsResumedUpdateFailures, 0);
+  }
+  return true;
+}
+
+bool DeltaPerformer::CheckpointUpdateProgress() {
+  Terminator::set_exit_blocked(true);
+  if (last_updated_buffer_offset_ != buffer_offset_) {
+    // Resets the progress in case we die in the middle of the state update.
+    ResetUpdateProgress(prefs_, true);
+    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_buffer_offset_ = buffer_offset_;
+
+    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));
+    }
+  }
+  TEST_AND_RETURN_FALSE(prefs_->SetInt64(kPrefsUpdateStateNextOperation,
+                                         next_operation_num_));
+  return true;
+}
+
+bool DeltaPerformer::PrimeUpdateState() {
+  CHECK(manifest_valid_);
+  block_size_ = manifest_.block_size();
+
+  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));
+  }
+
+  string signature_blob;
+  if (prefs_->GetString(kPrefsUpdateStateSignatureBlob, &signature_blob)) {
+    signatures_message_data_.assign(signature_blob.begin(),
+                                    signature_blob.end());
+  }
+
+  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;
+
+  // 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;
+}
+
+}  // namespace chromeos_update_engine