tools/releasetools/ota_from_target_files.py

#!/usr/bin/env python
#
# Copyright (C) 2008 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.

"""
Given a target-files zipfile, produces an OTA package that installs that build.
An incremental OTA is produced if -i is given, otherwise a full OTA is produced.

Usage:  ota_from_target_files [options] input_target_files output_ota_package

Common options that apply to both of non-A/B and A/B OTAs

  --downgrade
      Intentionally generate an incremental OTA that updates from a newer build
      to an older one (e.g. downgrading from P preview back to O MR1).
      "ota-downgrade=yes" will be set in the package metadata file. A data wipe
      will always be enforced when using this flag, so "ota-wipe=yes" will also
      be included in the metadata file. The update-binary in the source build
      will be used in the OTA package, unless --binary flag is specified. Please
      also check the comment for --override_timestamp below.

  -i  (--incremental_from) <file>
      Generate an incremental OTA using the given target-files zip as the
      starting build.

  -k  (--package_key) <key>
      Key to use to sign the package (default is the value of
      default_system_dev_certificate from the input target-files's
      META/misc_info.txt, or "build/make/target/product/security/testkey" if
      that value is not specified).

      For incremental OTAs, the default value is based on the source
      target-file, not the target build.

  --override_timestamp
      Intentionally generate an incremental OTA that updates from a newer build
      to an older one (based on timestamp comparison), by setting the downgrade
      flag in the package metadata. This differs from --downgrade flag, as we
      don't enforce a data wipe with this flag. Because we know for sure this is
      NOT an actual downgrade case, but two builds happen to be cut in a reverse
      order (e.g. from two branches). A legit use case is that we cut a new
      build C (after having A and B), but want to enfore an update path of A ->
      C -> B. Specifying --downgrade may not help since that would enforce a
      data wipe for C -> B update.

      We used to set a fake timestamp in the package metadata for this flow. But
      now we consolidate the two cases (i.e. an actual downgrade, or a downgrade
      based on timestamp) with the same "ota-downgrade=yes" flag, with the
      difference being whether "ota-wipe=yes" is set.

  --wipe_user_data
      Generate an OTA package that will wipe the user data partition when
      installed.

  --retrofit_dynamic_partitions
      Generates an OTA package that updates a device to support dynamic
      partitions (default False). This flag is implied when generating
      an incremental OTA where the base build does not support dynamic
      partitions but the target build does. For A/B, when this flag is set,
      --skip_postinstall is implied.

  --skip_compatibility_check
      Skip adding the compatibility package to the generated OTA package.

  --output_metadata_path
      Write a copy of the metadata to a separate file. Therefore, users can
      read the post build fingerprint without extracting the OTA package.

Non-A/B OTA specific options

  -b  (--binary) <file>
      Use the given binary as the update-binary in the output package, instead
      of the binary in the build's target_files. Use for development only.

  --block
      Generate a block-based OTA for non-A/B device. We have deprecated the
      support for file-based OTA since O. Block-based OTA will be used by
      default for all non-A/B devices. Keeping this flag here to not break
      existing callers.

  -e  (--extra_script) <file>
      Insert the contents of file at the end of the update script.

  --full_bootloader
      Similar to --full_radio. When generating an incremental OTA, always
      include a full copy of bootloader image.

  --full_radio
      When generating an incremental OTA, always include a full copy of radio
      image. This option is only meaningful when -i is specified, because a full
      radio is always included in a full OTA if applicable.

  --log_diff <file>
      Generate a log file that shows the differences in the source and target
      builds for an incremental package. This option is only meaningful when -i
      is specified.

  -o  (--oem_settings) <main_file[,additional_files...]>
      Comma seperated list of files used to specify the expected OEM-specific
      properties on the OEM partition of the intended device. Multiple expected
      values can be used by providing multiple files. Only the first dict will
      be used to compute fingerprint, while the rest will be used to assert
      OEM-specific properties.

  --oem_no_mount
      For devices with OEM-specific properties but without an OEM partition, do
      not mount the OEM partition in the updater-script. This should be very
      rarely used, since it's expected to have a dedicated OEM partition for
      OEM-specific properties. Only meaningful when -o is specified.

  --stash_threshold <float>
      Specify the threshold that will be used to compute the maximum allowed
      stash size (defaults to 0.8).

  -t  (--worker_threads) <int>
      Specify the number of worker-threads that will be used when generating
      patches for incremental updates (defaults to 3).

  --verify
      Verify the checksums of the updated system and vendor (if any) partitions.
      Non-A/B incremental OTAs only.

  -2  (--two_step)
      Generate a 'two-step' OTA package, where recovery is updated first, so
      that any changes made to the system partition are done using the new
      recovery (new kernel, etc.).

A/B OTA specific options

  --disable_fec_computation
      Disable the on device FEC data computation for incremental updates.

  --include_secondary
      Additionally include the payload for secondary slot images (default:
      False). Only meaningful when generating A/B OTAs.

      By default, an A/B OTA package doesn't contain the images for the
      secondary slot (e.g. system_other.img). Specifying this flag allows
      generating a separate payload that will install secondary slot images.

      Such a package needs to be applied in a two-stage manner, with a reboot
      in-between. During the first stage, the updater applies the primary
      payload only. Upon finishing, it reboots the device into the newly updated
      slot. It then continues to install the secondary payload to the inactive
      slot, but without switching the active slot at the end (needs the matching
      support in update_engine, i.e. SWITCH_SLOT_ON_REBOOT flag).

      Due to the special install procedure, the secondary payload will be always
      generated as a full payload.

  --payload_signer <signer>
      Specify the signer when signing the payload and metadata for A/B OTAs.
      By default (i.e. without this flag), it calls 'openssl pkeyutl' to sign
      with the package private key. If the private key cannot be accessed
      directly, a payload signer that knows how to do that should be specified.
      The signer will be supplied with "-inkey <path_to_key>",
      "-in <input_file>" and "-out <output_file>" parameters.

  --payload_signer_args <args>
      Specify the arguments needed for payload signer.

  --payload_signer_key_size <key_size>
      Specify the key size in bytes of the payload signer.

  --skip_postinstall
      Skip the postinstall hooks when generating an A/B OTA package (default:
      False). Note that this discards ALL the hooks, including non-optional
      ones. Should only be used if caller knows it's safe to do so (e.g. all the
      postinstall work is to dexopt apps and a data wipe will happen immediately
      after). Only meaningful when generating A/B OTAs.
"""

from __future__ import print_function

import collections
import logging
import multiprocessing
import os.path
import shlex
import shutil
import struct
import sys
import tempfile
import zipfile

import common
import edify_generator
import verity_utils

if sys.hexversion < 0x02070000:
  print("Python 2.7 or newer is required.", file=sys.stderr)
  sys.exit(1)

logger = logging.getLogger(__name__)

OPTIONS = common.OPTIONS
OPTIONS.package_key = None
OPTIONS.incremental_source = None
OPTIONS.verify = False
OPTIONS.patch_threshold = 0.95
OPTIONS.wipe_user_data = False
OPTIONS.downgrade = False
OPTIONS.extra_script = None
OPTIONS.worker_threads = multiprocessing.cpu_count() // 2
if OPTIONS.worker_threads == 0:
  OPTIONS.worker_threads = 1
OPTIONS.two_step = False
OPTIONS.include_secondary = False
OPTIONS.no_signing = False
OPTIONS.block_based = True
OPTIONS.updater_binary = None
OPTIONS.oem_source = None
OPTIONS.oem_no_mount = False
OPTIONS.full_radio = False
OPTIONS.full_bootloader = False
# Stash size cannot exceed cache_size * threshold.
OPTIONS.cache_size = None
OPTIONS.stash_threshold = 0.8
OPTIONS.log_diff = None
OPTIONS.payload_signer = None
OPTIONS.payload_signer_args = []
OPTIONS.payload_signer_key_size = None
OPTIONS.extracted_input = None
OPTIONS.key_passwords = []
OPTIONS.skip_postinstall = False
OPTIONS.retrofit_dynamic_partitions = False
OPTIONS.skip_compatibility_check = False
OPTIONS.output_metadata_path = None
OPTIONS.disable_fec_computation = False


METADATA_NAME = 'META-INF/com/android/metadata'
POSTINSTALL_CONFIG = 'META/postinstall_config.txt'
DYNAMIC_PARTITION_INFO = 'META/dynamic_partitions_info.txt'
AB_PARTITIONS = 'META/ab_partitions.txt'
UNZIP_PATTERN = ['IMAGES/*', 'META/*', 'OTA/*', 'RADIO/*']
# Files to be unzipped for target diffing purpose.
TARGET_DIFFING_UNZIP_PATTERN = ['BOOT', 'RECOVERY', 'SYSTEM/*', 'VENDOR/*',
                                'PRODUCT/*', 'SYSTEM_EXT/*', 'ODM/*']
RETROFIT_DAP_UNZIP_PATTERN = ['OTA/super_*.img', AB_PARTITIONS]


class BuildInfo(object):
  """A class that holds the information for a given build.

  This class wraps up the property querying for a given source or target build.
  It abstracts away the logic of handling OEM-specific properties, and caches
  the commonly used properties such as fingerprint.

  There are two types of info dicts: a) build-time info dict, which is generated
  at build time (i.e. included in a target_files zip); b) OEM info dict that is
  specified at package generation time (via command line argument
  '--oem_settings'). If a build doesn't use OEM-specific properties (i.e. not
  having "oem_fingerprint_properties" in build-time info dict), all the queries
  would be answered based on build-time info dict only. Otherwise if using
  OEM-specific properties, some of them will be calculated from two info dicts.

  Users can query properties similarly as using a dict() (e.g. info['fstab']),
  or to query build properties via GetBuildProp() or GetVendorBuildProp().

  Attributes:
    info_dict: The build-time info dict.
    is_ab: Whether it's a build that uses A/B OTA.
    oem_dicts: A list of OEM dicts.
    oem_props: A list of OEM properties that should be read from OEM dicts; None
        if the build doesn't use any OEM-specific property.
    fingerprint: The fingerprint of the build, which would be calculated based
        on OEM properties if applicable.
    device: The device name, which could come from OEM dicts if applicable.
  """

  _RO_PRODUCT_RESOLVE_PROPS = ["ro.product.brand", "ro.product.device",
                               "ro.product.manufacturer", "ro.product.model",
                               "ro.product.name"]
  _RO_PRODUCT_PROPS_DEFAULT_SOURCE_ORDER = ["product", "odm", "vendor",
                                            "system_ext", "system"]

  def __init__(self, info_dict, oem_dicts):
    """Initializes a BuildInfo instance with the given dicts.

    Note that it only wraps up the given dicts, without making copies.

    Arguments:
      info_dict: The build-time info dict.
      oem_dicts: A list of OEM dicts (which is parsed from --oem_settings). Note
          that it always uses the first dict to calculate the fingerprint or the
          device name. The rest would be used for asserting OEM properties only
          (e.g. one package can be installed on one of these devices).
    """
    self.info_dict = info_dict
    self.oem_dicts = oem_dicts

    self._is_ab = info_dict.get("ab_update") == "true"
    self._oem_props = info_dict.get("oem_fingerprint_properties")

    if self._oem_props:
      assert oem_dicts, "OEM source required for this build"

    # These two should be computed only after setting self._oem_props.
    self._device = self.GetOemProperty("ro.product.device")
    self._fingerprint = self.CalculateFingerprint()

  @property
  def is_ab(self):
    return self._is_ab

  @property
  def device(self):
    return self._device

  @property
  def fingerprint(self):
    return self._fingerprint

  @property
  def vendor_fingerprint(self):
    return self._fingerprint_of("vendor")

  @property
  def product_fingerprint(self):
    return self._fingerprint_of("product")

  @property
  def odm_fingerprint(self):
    return self._fingerprint_of("odm")

  def _fingerprint_of(self, partition):
    if partition + ".build.prop" not in self.info_dict:
      return None
    build_prop = self.info_dict[partition + ".build.prop"]
    if "ro." + partition + ".build.fingerprint" in build_prop:
      return build_prop["ro." + partition + ".build.fingerprint"]
    if "ro." + partition + ".build.thumbprint" in build_prop:
      return build_prop["ro." + partition + ".build.thumbprint"]
    return None

  @property
  def oem_props(self):
    return self._oem_props

  def __getitem__(self, key):
    return self.info_dict[key]

  def __setitem__(self, key, value):
    self.info_dict[key] = value

  def get(self, key, default=None):
    return self.info_dict.get(key, default)

  def items(self):
    return self.info_dict.items()

  def GetBuildProp(self, prop):
    """Returns the inquired build property."""
    if prop in BuildInfo._RO_PRODUCT_RESOLVE_PROPS:
      return self._ResolveRoProductBuildProp(prop)

    try:
      return self.info_dict.get("build.prop", {})[prop]
    except KeyError:
      raise common.ExternalError("couldn't find %s in build.prop" % (prop,))

  def _ResolveRoProductBuildProp(self, prop):
    """Resolves the inquired ro.product.* build property"""
    prop_val = self.info_dict.get("build.prop", {}).get(prop)
    if prop_val:
      return prop_val

    source_order_val = self.info_dict.get("build.prop", {}).get(
        "ro.product.property_source_order")
    if source_order_val:
      source_order = source_order_val.split(",")
    else:
      source_order = BuildInfo._RO_PRODUCT_PROPS_DEFAULT_SOURCE_ORDER

    # Check that all sources in ro.product.property_source_order are valid
    if any([x not in BuildInfo._RO_PRODUCT_PROPS_DEFAULT_SOURCE_ORDER
            for x in source_order]):
      raise common.ExternalError(
          "Invalid ro.product.property_source_order '{}'".format(source_order))

    for source in source_order:
      source_prop = prop.replace(
          "ro.product", "ro.product.{}".format(source), 1)
      prop_val = self.info_dict.get(
          "{}.build.prop".format(source), {}).get(source_prop)
      if prop_val:
        return prop_val

    raise common.ExternalError("couldn't resolve {}".format(prop))

  def GetVendorBuildProp(self, prop):
    """Returns the inquired vendor build property."""
    try:
      return self.info_dict.get("vendor.build.prop", {})[prop]
    except KeyError:
      raise common.ExternalError(
          "couldn't find %s in vendor.build.prop" % (prop,))

  def GetOemProperty(self, key):
    if self.oem_props is not None and key in self.oem_props:
      return self.oem_dicts[0][key]
    return self.GetBuildProp(key)

  def CalculateFingerprint(self):
    if self.oem_props is None:
      try:
        return self.GetBuildProp("ro.build.fingerprint")
      except common.ExternalError:
        return "{}/{}/{}:{}/{}/{}:{}/{}".format(
            self.GetBuildProp("ro.product.brand"),
            self.GetBuildProp("ro.product.name"),
            self.GetBuildProp("ro.product.device"),
            self.GetBuildProp("ro.build.version.release"),
            self.GetBuildProp("ro.build.id"),
            self.GetBuildProp("ro.build.version.incremental"),
            self.GetBuildProp("ro.build.type"),
            self.GetBuildProp("ro.build.tags"))
    return "%s/%s/%s:%s" % (
        self.GetOemProperty("ro.product.brand"),
        self.GetOemProperty("ro.product.name"),
        self.GetOemProperty("ro.product.device"),
        self.GetBuildProp("ro.build.thumbprint"))

  def WriteMountOemScript(self, script):
    assert self.oem_props is not None
    recovery_mount_options = self.info_dict.get("recovery_mount_options")
    script.Mount("/oem", recovery_mount_options)

  def WriteDeviceAssertions(self, script, oem_no_mount):
    # Read the property directly if not using OEM properties.
    if not self.oem_props:
      script.AssertDevice(self.device)
      return

    # Otherwise assert OEM properties.
    if not self.oem_dicts:
      raise common.ExternalError(
          "No OEM file provided to answer expected assertions")

    for prop in self.oem_props.split():
      values = []
      for oem_dict in self.oem_dicts:
        if prop in oem_dict:
          values.append(oem_dict[prop])
      if not values:
        raise common.ExternalError(
            "The OEM file is missing the property %s" % (prop,))
      script.AssertOemProperty(prop, values, oem_no_mount)


class PayloadSigner(object):
  """A class that wraps the payload signing works.

  When generating a Payload, hashes of the payload and metadata files will be
  signed with the device key, either by calling an external payload signer or
  by calling openssl with the package key. This class provides a unified
  interface, so that callers can just call PayloadSigner.Sign().

  If an external payload signer has been specified (OPTIONS.payload_signer), it
  calls the signer with the provided args (OPTIONS.payload_signer_args). Note
  that the signing key should be provided as part of the payload_signer_args.
  Otherwise without an external signer, it uses the package key
  (OPTIONS.package_key) and calls openssl for the signing works.
  """

  def __init__(self):
    if OPTIONS.payload_signer is None:
      # Prepare the payload signing key.
      private_key = OPTIONS.package_key + OPTIONS.private_key_suffix
      pw = OPTIONS.key_passwords[OPTIONS.package_key]

      cmd = ["openssl", "pkcs8", "-in", private_key, "-inform", "DER"]
      cmd.extend(["-passin", "pass:" + pw] if pw else ["-nocrypt"])
      signing_key = common.MakeTempFile(prefix="key-", suffix=".key")
      cmd.extend(["-out", signing_key])
      common.RunAndCheckOutput(cmd, verbose=False)

      self.signer = "openssl"
      self.signer_args = ["pkeyutl", "-sign", "-inkey", signing_key,
                          "-pkeyopt", "digest:sha256"]
      self.key_size = self._GetKeySizeInBytes(signing_key)
    else:
      self.signer = OPTIONS.payload_signer
      self.signer_args = OPTIONS.payload_signer_args
      if OPTIONS.payload_signer_key_size:
        self.key_size = int(OPTIONS.payload_signer_key_size)
        assert self.key_size == 256 or self.key_size == 512, \
            "Unsupported key size {}".format(OPTIONS.payload_signer_key_size)
      else:
        self.key_size = 256

  @staticmethod
  def _GetKeySizeInBytes(signing_key):
    modulus_file = common.MakeTempFile(prefix="modulus-")
    cmd = ["openssl", "rsa", "-inform", "PEM", "-in", signing_key, "-modulus",
           "-noout", "-out", modulus_file]
    common.RunAndCheckOutput(cmd, verbose=False)

    with open(modulus_file) as f:
      modulus_string = f.read()
    # The modulus string has the format "Modulus=$data", where $data is the
    # concatenation of hex dump of the modulus.
    MODULUS_PREFIX = "Modulus="
    assert modulus_string.startswith(MODULUS_PREFIX)
    modulus_string = modulus_string[len(MODULUS_PREFIX):]
    key_size = len(modulus_string) // 2
    assert key_size == 256 or key_size == 512, \
        "Unsupported key size {}".format(key_size)
    return key_size

  def Sign(self, in_file):
    """Signs the given input file. Returns the output filename."""
    out_file = common.MakeTempFile(prefix="signed-", suffix=".bin")
    cmd = [self.signer] + self.signer_args + ['-in', in_file, '-out', out_file]
    common.RunAndCheckOutput(cmd)
    return out_file


class Payload(object):
  """Manages the creation and the signing of an A/B OTA Payload."""

  PAYLOAD_BIN = 'payload.bin'
  PAYLOAD_PROPERTIES_TXT = 'payload_properties.txt'
  SECONDARY_PAYLOAD_BIN = 'secondary/payload.bin'
  SECONDARY_PAYLOAD_PROPERTIES_TXT = 'secondary/payload_properties.txt'

  def __init__(self, secondary=False):
    """Initializes a Payload instance.

    Args:
      secondary: Whether it's generating a secondary payload (default: False).
    """
    self.payload_file = None
    self.payload_properties = None
    self.secondary = secondary

  def _Run(self, cmd):  # pylint: disable=no-self-use
    # Don't pipe (buffer) the output if verbose is set. Let
    # brillo_update_payload write to stdout/stderr directly, so its progress can
    # be monitored.
    if OPTIONS.verbose:
      common.RunAndCheckOutput(cmd, stdout=None, stderr=None)
    else:
      common.RunAndCheckOutput(cmd)

  def Generate(self, target_file, source_file=None, additional_args=None):
    """Generates a payload from the given target-files zip(s).

    Args:
      target_file: The filename of the target build target-files zip.
      source_file: The filename of the source build target-files zip; or None if
          generating a full OTA.
      additional_args: A list of additional args that should be passed to
          brillo_update_payload script; or None.
    """
    if additional_args is None:
      additional_args = []

    payload_file = common.MakeTempFile(prefix="payload-", suffix=".bin")
    cmd = ["brillo_update_payload", "generate",
           "--payload", payload_file,
           "--target_image", target_file]
    if source_file is not None:
      cmd.extend(["--source_image", source_file])
      if OPTIONS.disable_fec_computation:
        cmd.extend(["--disable_fec_computation", "true"])
    cmd.extend(additional_args)
    self._Run(cmd)

    self.payload_file = payload_file
    self.payload_properties = None

  def Sign(self, payload_signer):
    """Generates and signs the hashes of the payload and metadata.

    Args:
      payload_signer: A PayloadSigner() instance that serves the signing work.

    Raises:
      AssertionError: On any failure when calling brillo_update_payload script.
    """
    assert isinstance(payload_signer, PayloadSigner)

    # 1. Generate hashes of the payload and metadata files.
    payload_sig_file = common.MakeTempFile(prefix="sig-", suffix=".bin")
    metadata_sig_file = common.MakeTempFile(prefix="sig-", suffix=".bin")
    cmd = ["brillo_update_payload", "hash",
           "--unsigned_payload", self.payload_file,
           "--signature_size", str(payload_signer.key_size),
           "--metadata_hash_file", metadata_sig_file,
           "--payload_hash_file", payload_sig_file]
    self._Run(cmd)

    # 2. Sign the hashes.
    signed_payload_sig_file = payload_signer.Sign(payload_sig_file)
    signed_metadata_sig_file = payload_signer.Sign(metadata_sig_file)

    # 3. Insert the signatures back into the payload file.
    signed_payload_file = common.MakeTempFile(prefix="signed-payload-",
                                              suffix=".bin")
    cmd = ["brillo_update_payload", "sign",
           "--unsigned_payload", self.payload_file,
           "--payload", signed_payload_file,
           "--signature_size", str(payload_signer.key_size),
           "--metadata_signature_file", signed_metadata_sig_file,
           "--payload_signature_file", signed_payload_sig_file]
    self._Run(cmd)

    # 4. Dump the signed payload properties.
    properties_file = common.MakeTempFile(prefix="payload-properties-",
                                          suffix=".txt")
    cmd = ["brillo_update_payload", "properties",
           "--payload", signed_payload_file,
           "--properties_file", properties_file]
    self._Run(cmd)

    if self.secondary:
      with open(properties_file, "a") as f:
        f.write("SWITCH_SLOT_ON_REBOOT=0\n")

    if OPTIONS.wipe_user_data:
      with open(properties_file, "a") as f:
        f.write("POWERWASH=1\n")

    self.payload_file = signed_payload_file
    self.payload_properties = properties_file

  def WriteToZip(self, output_zip):
    """Writes the payload to the given zip.

    Args:
      output_zip: The output ZipFile instance.
    """
    assert self.payload_file is not None
    assert self.payload_properties is not None

    if self.secondary:
      payload_arcname = Payload.SECONDARY_PAYLOAD_BIN
      payload_properties_arcname = Payload.SECONDARY_PAYLOAD_PROPERTIES_TXT
    else:
      payload_arcname = Payload.PAYLOAD_BIN
      payload_properties_arcname = Payload.PAYLOAD_PROPERTIES_TXT

    # Add the signed payload file and properties into the zip. In order to
    # support streaming, we pack them as ZIP_STORED. So these entries can be
    # read directly with the offset and length pairs.
    common.ZipWrite(output_zip, self.payload_file, arcname=payload_arcname,
                    compress_type=zipfile.ZIP_STORED)
    common.ZipWrite(output_zip, self.payload_properties,
                    arcname=payload_properties_arcname,
                    compress_type=zipfile.ZIP_STORED)


def SignOutput(temp_zip_name, output_zip_name):
  pw = OPTIONS.key_passwords[OPTIONS.package_key]

  common.SignFile(temp_zip_name, output_zip_name, OPTIONS.package_key, pw,
                  whole_file=True)


def _LoadOemDicts(oem_source):
  """Returns the list of loaded OEM properties dict."""
  if not oem_source:
    return None

  oem_dicts = []
  for oem_file in oem_source:
    with open(oem_file) as fp:
      oem_dicts.append(common.LoadDictionaryFromLines(fp.readlines()))
  return oem_dicts


def _WriteRecoveryImageToBoot(script, output_zip):
  """Find and write recovery image to /boot in two-step OTA.

  In two-step OTAs, we write recovery image to /boot as the first step so that
  we can reboot to there and install a new recovery image to /recovery.
  A special "recovery-two-step.img" will be preferred, which encodes the correct
  path of "/boot". Otherwise the device may show "device is corrupt" message
  when booting into /boot.

  Fall back to using the regular recovery.img if the two-step recovery image
  doesn't exist. Note that rebuilding the special image at this point may be
  infeasible, because we don't have the desired boot signer and keys when
  calling ota_from_target_files.py.
  """

  recovery_two_step_img_name = "recovery-two-step.img"
  recovery_two_step_img_path = os.path.join(
      OPTIONS.input_tmp, "OTA", recovery_two_step_img_name)
  if os.path.exists(recovery_two_step_img_path):
    common.ZipWrite(
        output_zip,
        recovery_two_step_img_path,
        arcname=recovery_two_step_img_name)
    logger.info(
        "two-step package: using %s in stage 1/3", recovery_two_step_img_name)
    script.WriteRawImage("/boot", recovery_two_step_img_name)
  else:
    logger.info("two-step package: using recovery.img in stage 1/3")
    # The "recovery.img" entry has been written into package earlier.
    script.WriteRawImage("/boot", "recovery.img")


def HasRecoveryPatch(target_files_zip):
  namelist = [name for name in target_files_zip.namelist()]
  return ("SYSTEM/recovery-from-boot.p" in namelist or
          "SYSTEM/etc/recovery.img" in namelist)


def HasPartition(target_files_zip, partition):
  try:
    target_files_zip.getinfo(partition.upper() + "/")
    return True
  except KeyError:
    return False


def HasVendorPartition(target_files_zip):
  return HasPartition(target_files_zip, "vendor")


def HasProductPartition(target_files_zip):
  return HasPartition(target_files_zip, "product")


def HasOdmPartition(target_files_zip):
  return HasPartition(target_files_zip, "odm")


def HasTrebleEnabled(target_files_zip, target_info):
  return (HasVendorPartition(target_files_zip) and
          target_info.GetBuildProp("ro.treble.enabled") == "true")


def WriteFingerprintAssertion(script, target_info, source_info):
  source_oem_props = source_info.oem_props
  target_oem_props = target_info.oem_props

  if source_oem_props is None and target_oem_props is None:
    script.AssertSomeFingerprint(
        source_info.fingerprint, target_info.fingerprint)
  elif source_oem_props is not None and target_oem_props is not None:
    script.AssertSomeThumbprint(
        target_info.GetBuildProp("ro.build.thumbprint"),
        source_info.GetBuildProp("ro.build.thumbprint"))
  elif source_oem_props is None and target_oem_props is not None:
    script.AssertFingerprintOrThumbprint(
        source_info.fingerprint,
        target_info.GetBuildProp("ro.build.thumbprint"))
  else:
    script.AssertFingerprintOrThumbprint(
        target_info.fingerprint,
        source_info.GetBuildProp("ro.build.thumbprint"))


def AddCompatibilityArchiveIfTrebleEnabled(target_zip, output_zip, target_info,
                                           source_info=None):
  """Adds compatibility info into the output zip if it's Treble-enabled target.

  Metadata used for on-device compatibility verification is retrieved from
  target_zip then added to compatibility.zip which is added to the output_zip
  archive.

  Compatibility archive should only be included for devices that have enabled
  Treble support.

  Args:
    target_zip: Zip file containing the source files to be included for OTA.
    output_zip: Zip file that will be sent for OTA.
    target_info: The BuildInfo instance that holds the target build info.
    source_info: The BuildInfo instance that holds the source build info, if
        generating an incremental OTA; None otherwise.
  """

  def AddCompatibilityArchive(framework_updated, device_updated):
    """Adds compatibility info based on update status of both sides of Treble
    boundary.

    Args:
      framework_updated: If True, the system / product image will be updated
          and therefore their metadata should be included.
      device_updated: If True, the vendor / odm image will be updated and
          therefore their metadata should be included.
    """
    # Determine what metadata we need. Files are names relative to META/.
    compatibility_files = []
    device_metadata = ("vendor_manifest.xml", "vendor_matrix.xml")
    framework_metadata = ("system_manifest.xml", "system_matrix.xml")
    if device_updated:
      compatibility_files += device_metadata
    if framework_updated:
      compatibility_files += framework_metadata

    # Create new archive.
    compatibility_archive = tempfile.NamedTemporaryFile()
    compatibility_archive_zip = zipfile.ZipFile(
        compatibility_archive, "w", compression=zipfile.ZIP_DEFLATED)

    # Add metadata.
    for file_name in compatibility_files:
      target_file_name = "META/" + file_name

      if target_file_name in target_zip.namelist():
        data = target_zip.read(target_file_name)
        common.ZipWriteStr(compatibility_archive_zip, file_name, data)

    # Ensure files are written before we copy into output_zip.
    compatibility_archive_zip.close()

    # Only add the archive if we have any compatibility info.
    if compatibility_archive_zip.namelist():
      common.ZipWrite(output_zip, compatibility_archive.name,
                      arcname="compatibility.zip",
                      compress_type=zipfile.ZIP_STORED)

  def FingerprintChanged(source_fp, target_fp):
    if source_fp is None or target_fp is None:
      return True
    return source_fp != target_fp

  # Will only proceed if the target has enabled the Treble support (as well as
  # having a /vendor partition).
  if not HasTrebleEnabled(target_zip, target_info):
    return

  # Skip adding the compatibility package as a workaround for b/114240221. The
  # compatibility will always fail on devices without qualified kernels.
  if OPTIONS.skip_compatibility_check:
    return

  # Full OTA carries the info for system/vendor/product/odm
  if source_info is None:
    AddCompatibilityArchive(True, True)
    return

  source_fp = source_info.fingerprint
  target_fp = target_info.fingerprint
  system_updated = source_fp != target_fp

  # other build fingerprints could be possibly blacklisted at build time. For
  # such a case, we consider those images being changed.
  vendor_updated = FingerprintChanged(source_info.vendor_fingerprint,
                                      target_info.vendor_fingerprint)
  product_updated = HasProductPartition(target_zip) and \
                    FingerprintChanged(source_info.product_fingerprint,
                                       target_info.product_fingerprint)
  odm_updated = HasOdmPartition(target_zip) and \
                FingerprintChanged(source_info.odm_fingerprint,
                                   target_info.odm_fingerprint)

  AddCompatibilityArchive(system_updated or product_updated,
                          vendor_updated or odm_updated)


def GetBlockDifferences(target_zip, source_zip, target_info, source_info,
                        device_specific):
  """Returns a ordered dict of block differences with partition name as key."""

  def GetIncrementalBlockDifferenceForPartition(name):
    if not HasPartition(source_zip, name):
      raise RuntimeError("can't generate incremental that adds {}".format(name))

    partition_src = common.GetUserImage(name, OPTIONS.source_tmp, source_zip,
                                        info_dict=source_info,
                                        allow_shared_blocks=allow_shared_blocks)

    hashtree_info_generator = verity_utils.CreateHashtreeInfoGenerator(
        name, 4096, target_info)
    partition_tgt = common.GetUserImage(name, OPTIONS.target_tmp, target_zip,
                                        info_dict=target_info,
                                        allow_shared_blocks=allow_shared_blocks,
                                        hashtree_info_generator=
                                        hashtree_info_generator)

    # Check the first block of the source system partition for remount R/W only
    # if the filesystem is ext4.
    partition_source_info = source_info["fstab"]["/" + name]
    check_first_block = partition_source_info.fs_type == "ext4"
    # Disable using imgdiff for squashfs. 'imgdiff -z' expects input files to be
    # in zip formats. However with squashfs, a) all files are compressed in LZ4;
    # b) the blocks listed in block map may not contain all the bytes for a
    # given file (because they're rounded to be 4K-aligned).
    partition_target_info = target_info["fstab"]["/" + name]
    disable_imgdiff = (partition_source_info.fs_type == "squashfs" or
                       partition_target_info.fs_type == "squashfs")
    return common.BlockDifference(name, partition_src, partition_tgt,
                                  check_first_block,
                                  version=blockimgdiff_version,
                                  disable_imgdiff=disable_imgdiff)

  if source_zip:
    # See notes in common.GetUserImage()
    allow_shared_blocks = (source_info.get('ext4_share_dup_blocks') == "true" or
                           target_info.get('ext4_share_dup_blocks') == "true")
    blockimgdiff_version = max(
        int(i) for i in target_info.get(
            "blockimgdiff_versions", "1").split(","))
    assert blockimgdiff_version >= 3

  block_diff_dict = collections.OrderedDict()
  partition_names = ["system", "vendor", "product", "odm", "system_ext"]
  for partition in partition_names:
    if not HasPartition(target_zip, partition):
      continue
    # Full OTA update.
    if not source_zip:
      tgt = common.GetUserImage(partition, OPTIONS.input_tmp, target_zip,
                                info_dict=target_info,
                                reset_file_map=True)
      block_diff_dict[partition] = common.BlockDifference(partition, tgt,
                                                          src=None)
    # Incremental OTA update.
    else:
      block_diff_dict[partition] = GetIncrementalBlockDifferenceForPartition(
          partition)
  assert "system" in block_diff_dict

  # Get the block diffs from the device specific script. If there is a
  # duplicate block diff for a partition, ignore the diff in the generic script
  # and use the one in the device specific script instead.
  if source_zip:
    device_specific_diffs = device_specific.IncrementalOTA_GetBlockDifferences()
    function_name = "IncrementalOTA_GetBlockDifferences"
  else:
    device_specific_diffs = device_specific.FullOTA_GetBlockDifferences()
    function_name = "FullOTA_GetBlockDifferences"

  if device_specific_diffs:
    assert all(isinstance(diff, common.BlockDifference)
               for diff in device_specific_diffs), \
        "{} is not returning a list of BlockDifference objects".format(
            function_name)
    for diff in device_specific_diffs:
      if diff.partition in block_diff_dict:
        logger.warning("Duplicate block difference found. Device specific block"
                       " diff for partition '%s' overrides the one in generic"
                       " script.", diff.partition)
      block_diff_dict[diff.partition] = diff

  return block_diff_dict


def WriteFullOTAPackage(input_zip, output_file):
  target_info = BuildInfo(OPTIONS.info_dict, OPTIONS.oem_dicts)

  # We don't know what version it will be installed on top of. We expect the API
  # just won't change very often. Similarly for fstab, it might have changed in
  # the target build.
  target_api_version = target_info["recovery_api_version"]
  script = edify_generator.EdifyGenerator(target_api_version, target_info)

  if target_info.oem_props and not OPTIONS.oem_no_mount:
    target_info.WriteMountOemScript(script)

  metadata = GetPackageMetadata(target_info)

  if not OPTIONS.no_signing:
    staging_file = common.MakeTempFile(suffix='.zip')
  else:
    staging_file = output_file

  output_zip = zipfile.ZipFile(
      staging_file, "w", compression=zipfile.ZIP_DEFLATED)

  device_specific = common.DeviceSpecificParams(
      input_zip=input_zip,
      input_version=target_api_version,
      output_zip=output_zip,
      script=script,
      input_tmp=OPTIONS.input_tmp,
      metadata=metadata,
      info_dict=OPTIONS.info_dict)

  assert HasRecoveryPatch(input_zip)

  # Assertions (e.g. downgrade check, device properties check).
  ts = target_info.GetBuildProp("ro.build.date.utc")
  ts_text = target_info.GetBuildProp("ro.build.date")
  script.AssertOlderBuild(ts, ts_text)

  target_info.WriteDeviceAssertions(script, OPTIONS.oem_no_mount)
  device_specific.FullOTA_Assertions()

  block_diff_dict = GetBlockDifferences(target_zip=input_zip, source_zip=None,
                                        target_info=target_info,
                                        source_info=None,
                                        device_specific=device_specific)

  # Two-step package strategy (in chronological order, which is *not*
  # the order in which the generated script has things):
  #
  # if stage is not "2/3" or "3/3":
  #    write recovery image to boot partition
  #    set stage to "2/3"
  #    reboot to boot partition and restart recovery
  # else if stage is "2/3":
  #    write recovery image to recovery partition
  #    set stage to "3/3"
  #    reboot to recovery partition and restart recovery
  # else:
  #    (stage must be "3/3")
  #    set stage to ""
  #    do normal full package installation:
  #       wipe and install system, boot image, etc.
  #       set up system to update recovery partition on first boot
  #    complete script normally
  #    (allow recovery to mark itself finished and reboot)

  recovery_img = common.GetBootableImage("recovery.img", "recovery.img",
                                         OPTIONS.input_tmp, "RECOVERY")
  if OPTIONS.two_step:
    if not target_info.get("multistage_support"):
      assert False, "two-step packages not supported by this build"
    fs = target_info["fstab"]["/misc"]
    assert fs.fs_type.upper() == "EMMC", \
        "two-step packages only supported on devices with EMMC /misc partitions"
    bcb_dev = {"bcb_dev": fs.device}
    common.ZipWriteStr(output_zip, "recovery.img", recovery_img.data)
    script.AppendExtra("""
if get_stage("%(bcb_dev)s") == "2/3" then
""" % bcb_dev)

    # Stage 2/3: Write recovery image to /recovery (currently running /boot).
    script.Comment("Stage 2/3")
    script.WriteRawImage("/recovery", "recovery.img")
    script.AppendExtra("""
set_stage("%(bcb_dev)s", "3/3");
reboot_now("%(bcb_dev)s", "recovery");
else if get_stage("%(bcb_dev)s") == "3/3" then
""" % bcb_dev)

    # Stage 3/3: Make changes.
    script.Comment("Stage 3/3")

  # Dump fingerprints
  script.Print("Target: {}".format(target_info.fingerprint))

  device_specific.FullOTA_InstallBegin()

  # All other partitions as well as the data wipe use 10% of the progress, and
  # the update of the system partition takes the remaining progress.
  system_progress = 0.9 - (len(block_diff_dict) - 1) * 0.1
  if OPTIONS.wipe_user_data:
    system_progress -= 0.1
  progress_dict = {partition: 0.1 for partition in block_diff_dict}
  progress_dict["system"] = system_progress

  if target_info.get('use_dynamic_partitions') == "true":
    # Use empty source_info_dict to indicate that all partitions / groups must
    # be re-added.
    dynamic_partitions_diff = common.DynamicPartitionsDifference(
        info_dict=OPTIONS.info_dict,
        block_diffs=block_diff_dict.values(),
        progress_dict=progress_dict)
    dynamic_partitions_diff.WriteScript(script, output_zip,
                                        write_verify_script=OPTIONS.verify)
  else:
    for block_diff in block_diff_dict.values():
      block_diff.WriteScript(script, output_zip,
                             progress=progress_dict.get(block_diff.partition),
                             write_verify_script=OPTIONS.verify)

  AddCompatibilityArchiveIfTrebleEnabled(input_zip, output_zip, target_info)

  boot_img = common.GetBootableImage(
      "boot.img", "boot.img", OPTIONS.input_tmp, "BOOT")
  common.CheckSize(boot_img.data, "boot.img", target_info)
  common.ZipWriteStr(output_zip, "boot.img", boot_img.data)

  script.WriteRawImage("/boot", "boot.img")

  script.ShowProgress(0.1, 10)
  device_specific.FullOTA_InstallEnd()

  if OPTIONS.extra_script is not None:
    script.AppendExtra(OPTIONS.extra_script)

  script.UnmountAll()

  if OPTIONS.wipe_user_data:
    script.ShowProgress(0.1, 10)
    script.FormatPartition("/data")

  if OPTIONS.two_step:
    script.AppendExtra("""
set_stage("%(bcb_dev)s", "");
""" % bcb_dev)
    script.AppendExtra("else\n")

    # Stage 1/3: Nothing to verify for full OTA. Write recovery image to /boot.
    script.Comment("Stage 1/3")
    _WriteRecoveryImageToBoot(script, output_zip)

    script.AppendExtra("""
set_stage("%(bcb_dev)s", "2/3");
reboot_now("%(bcb_dev)s", "");
endif;
endif;
""" % bcb_dev)

  script.SetProgress(1)
  script.AddToZip(input_zip, output_zip, input_path=OPTIONS.updater_binary)
  metadata["ota-required-cache"] = str(script.required_cache)

  # We haven't written the metadata entry, which will be done in
  # FinalizeMetadata.
  common.ZipClose(output_zip)

  needed_property_files = (
      NonAbOtaPropertyFiles(),
  )
  FinalizeMetadata(metadata, staging_file, output_file, needed_property_files)


def WriteMetadata(metadata, output):
  """Writes the metadata to the zip archive or a file.

  Args:
    metadata: The metadata dict for the package.
    output: A ZipFile object or a string of the output file path.
  """

  value = "".join(["%s=%s\n" % kv for kv in sorted(metadata.items())])
  if isinstance(output, zipfile.ZipFile):
    common.ZipWriteStr(output, METADATA_NAME, value,
                       compress_type=zipfile.ZIP_STORED)
    return

  with open(output, 'w') as f:
    f.write(value)


def HandleDowngradeMetadata(metadata, target_info, source_info):
  # Only incremental OTAs are allowed to reach here.
  assert OPTIONS.incremental_source is not None

  post_timestamp = target_info.GetBuildProp("ro.build.date.utc")
  pre_timestamp = source_info.GetBuildProp("ro.build.date.utc")
  is_downgrade = int(post_timestamp) < int(pre_timestamp)

  if OPTIONS.downgrade:
    if not is_downgrade:
      raise RuntimeError(
          "--downgrade or --override_timestamp specified but no downgrade "
          "detected: pre: %s, post: %s" % (pre_timestamp, post_timestamp))
    metadata["ota-downgrade"] = "yes"
  else:
    if is_downgrade:
      raise RuntimeError(
          "Downgrade detected based on timestamp check: pre: %s, post: %s. "
          "Need to specify --override_timestamp OR --downgrade to allow "
          "building the incremental." % (pre_timestamp, post_timestamp))


def GetPackageMetadata(target_info, source_info=None):
  """Generates and returns the metadata dict.

  It generates a dict() that contains the info to be written into an OTA
  package (META-INF/com/android/metadata). It also handles the detection of
  downgrade / data wipe based on the global options.

  Args:
    target_info: The BuildInfo instance that holds the target build info.
    source_info: The BuildInfo instance that holds the source build info, or
        None if generating full OTA.

  Returns:
    A dict to be written into package metadata entry.
  """
  assert isinstance(target_info, BuildInfo)
  assert source_info is None or isinstance(source_info, BuildInfo)

  metadata = {
      'post-build' : target_info.fingerprint,
      'post-build-incremental' : target_info.GetBuildProp(
          'ro.build.version.incremental'),
      'post-sdk-level' : target_info.GetBuildProp(
          'ro.build.version.sdk'),
      'post-security-patch-level' : target_info.GetBuildProp(
          'ro.build.version.security_patch'),
  }

  if target_info.is_ab:
    metadata['ota-type'] = 'AB'
    metadata['ota-required-cache'] = '0'
  else:
    metadata['ota-type'] = 'BLOCK'

  if OPTIONS.wipe_user_data:
    metadata['ota-wipe'] = 'yes'

  if OPTIONS.retrofit_dynamic_partitions:
    metadata['ota-retrofit-dynamic-partitions'] = 'yes'

  is_incremental = source_info is not None
  if is_incremental:
    metadata['pre-build'] = source_info.fingerprint
    metadata['pre-build-incremental'] = source_info.GetBuildProp(
        'ro.build.version.incremental')
    metadata['pre-device'] = source_info.device
  else:
    metadata['pre-device'] = target_info.device

  # Use the actual post-timestamp, even for a downgrade case.
  metadata['post-timestamp'] = target_info.GetBuildProp('ro.build.date.utc')

  # Detect downgrades and set up downgrade flags accordingly.
  if is_incremental:
    HandleDowngradeMetadata(metadata, target_info, source_info)

  return metadata


class PropertyFiles(object):
  """A class that computes the property-files string for an OTA package.

  A property-files string is a comma-separated string that contains the
  offset/size info for an OTA package. The entries, which must be ZIP_STORED,
  can be fetched directly with the package URL along with the offset/size info.
  These strings can be used for streaming A/B OTAs, or allowing an updater to
  download package metadata entry directly, without paying the cost of
  downloading entire package.

  Computing the final property-files string requires two passes. Because doing
  the whole package signing (with signapk.jar) will possibly reorder the ZIP
  entries, which may in turn invalidate earlier computed ZIP entry offset/size
  values.

  This class provides functions to be called for each pass. The general flow is
  as follows.

    property_files = PropertyFiles()
    # The first pass, which writes placeholders before doing initial signing.
    property_files.Compute()
    SignOutput()

    # The second pass, by replacing the placeholders with actual data.
    property_files.Finalize()
    SignOutput()

  And the caller can additionally verify the final result.

    property_files.Verify()
  """

  def __init__(self):
    self.name = None
    self.required = ()
    self.optional = ()

  def Compute(self, input_zip):
    """Computes and returns a property-files string with placeholders.

    We reserve extra space for the offset and size of the metadata entry itself,
    although we don't know the final values until the package gets signed.

    Args:
      input_zip: The input ZIP file.

    Returns:
      A string with placeholders for the metadata offset/size info, e.g.
      "payload.bin:679:343,payload_properties.txt:378:45,metadata:        ".
    """
    return self.GetPropertyFilesString(input_zip, reserve_space=True)

  class InsufficientSpaceException(Exception):
    pass

  def Finalize(self, input_zip, reserved_length):
    """Finalizes a property-files string with actual METADATA offset/size info.

    The input ZIP file has been signed, with the ZIP entries in the desired
    place (signapk.jar will possibly reorder the ZIP entries). Now we compute
    the ZIP entry offsets and construct the property-files string with actual
    data. Note that during this process, we must pad the property-files string
    to the reserved length, so that the METADATA entry size remains the same.
    Otherwise the entries' offsets and sizes may change again.

    Args:
      input_zip: The input ZIP file.
      reserved_length: The reserved length of the property-files string during
          the call to Compute(). The final string must be no more than this
          size.

    Returns:
      A property-files string including the metadata offset/size info, e.g.
      "payload.bin:679:343,payload_properties.txt:378:45,metadata:69:379  ".

    Raises:
      InsufficientSpaceException: If the reserved length is insufficient to hold
          the final string.
    """
    result = self.GetPropertyFilesString(input_zip, reserve_space=False)
    if len(result) > reserved_length:
      raise self.InsufficientSpaceException(
          'Insufficient reserved space: reserved={}, actual={}'.format(
              reserved_length, len(result)))

    result += ' ' * (reserved_length - len(result))
    return result

  def Verify(self, input_zip, expected):
    """Verifies the input ZIP file contains the expected property-files string.

    Args:
      input_zip: The input ZIP file.
      expected: The property-files string that's computed from Finalize().

    Raises:
      AssertionError: On finding a mismatch.
    """
    actual = self.GetPropertyFilesString(input_zip)
    assert actual == expected, \
        "Mismatching streaming metadata: {} vs {}.".format(actual, expected)

  def GetPropertyFilesString(self, zip_file, reserve_space=False):
    """
    Constructs the property-files string per request.

    Args:
      zip_file: The input ZIP file.
      reserved_length: The reserved length of the property-files string.

    Returns:
      A property-files string including the metadata offset/size info, e.g.
      "payload.bin:679:343,payload_properties.txt:378:45,metadata:     ".
    """

    def ComputeEntryOffsetSize(name):
      """Computes the zip entry offset and size."""
      info = zip_file.getinfo(name)
      offset = info.header_offset
      offset += zipfile.sizeFileHeader
      offset += len(info.extra) + len(info.filename)
      size = info.file_size
      return '%s:%d:%d' % (os.path.basename(name), offset, size)

    tokens = []
    tokens.extend(self._GetPrecomputed(zip_file))
    for entry in self.required:
      tokens.append(ComputeEntryOffsetSize(entry))
    for entry in self.optional:
      if entry in zip_file.namelist():
        tokens.append(ComputeEntryOffsetSize(entry))

    # 'META-INF/com/android/metadata' is required. We don't know its actual
    # offset and length (as well as the values for other entries). So we reserve
    # 15-byte as a placeholder ('offset:length'), which is sufficient to cover
    # the space for metadata entry. Because 'offset' allows a max of 10-digit
    # (i.e. ~9 GiB), with a max of 4-digit for the length. Note that all the
    # reserved space serves the metadata entry only.
    if reserve_space:
      tokens.append('metadata:' + ' ' * 15)
    else:
      tokens.append(ComputeEntryOffsetSize(METADATA_NAME))

    return ','.join(tokens)

  def _GetPrecomputed(self, input_zip):
    """Computes the additional tokens to be included into the property-files.

    This applies to tokens without actual ZIP entries, such as
    payload_metadadata.bin. We want to expose the offset/size to updaters, so
    that they can download the payload metadata directly with the info.

    Args:
      input_zip: The input zip file.

    Returns:
      A list of strings (tokens) to be added to the property-files string.
    """
    # pylint: disable=no-self-use
    # pylint: disable=unused-argument
    return []


class StreamingPropertyFiles(PropertyFiles):
  """A subclass for computing the property-files for streaming A/B OTAs."""

  def __init__(self):
    super(StreamingPropertyFiles, self).__init__()
    self.name = 'ota-streaming-property-files'
    self.required = (
        # payload.bin and payload_properties.txt must exist.
        'payload.bin',
        'payload_properties.txt',
    )
    self.optional = (
        # care_map is available only if dm-verity is enabled.
        'care_map.pb',
        'care_map.txt',
        # compatibility.zip is available only if target supports Treble.
        'compatibility.zip',
    )


class AbOtaPropertyFiles(StreamingPropertyFiles):
  """The property-files for A/B OTA that includes payload_metadata.bin info.

  Since P, we expose one more token (aka property-file), in addition to the ones
  for streaming A/B OTA, for a virtual entry of 'payload_metadata.bin'.
  'payload_metadata.bin' is the header part of a payload ('payload.bin'), which
  doesn't exist as a separate ZIP entry, but can be used to verify if the
  payload can be applied on the given device.

  For backward compatibility, we keep both of the 'ota-streaming-property-files'
  and the newly added 'ota-property-files' in P. The new token will only be
  available in 'ota-property-files'.
  """

  def __init__(self):
    super(AbOtaPropertyFiles, self).__init__()
    self.name = 'ota-property-files'

  def _GetPrecomputed(self, input_zip):
    offset, size = self._GetPayloadMetadataOffsetAndSize(input_zip)
    return ['payload_metadata.bin:{}:{}'.format(offset, size)]

  @staticmethod
  def _GetPayloadMetadataOffsetAndSize(input_zip):
    """Computes the offset and size of the payload metadata for a given package.

    (From system/update_engine/update_metadata.proto)
    A delta update file contains all the deltas needed to update a system from
    one specific version to another specific version. The update format is
    represented by this struct pseudocode:

    struct delta_update_file {
      char magic[4] = "CrAU";
      uint64 file_format_version;
      uint64 manifest_size;  // Size of protobuf DeltaArchiveManifest

      // Only present if format_version > 1:
      uint32 metadata_signature_size;

      // The Bzip2 compressed DeltaArchiveManifest
      char manifest[metadata_signature_size];

      // The signature of the metadata (from the beginning of the payload up to
      // this location, not including the signature itself). This is a
      // serialized Signatures message.
      char medatada_signature_message[metadata_signature_size];

      // Data blobs for files, no specific format. The specific offset
      // and length of each data blob is recorded in the DeltaArchiveManifest.
      struct {
        char data[];
      } blobs[];

      // These two are not signed:
      uint64 payload_signatures_message_size;
      char payload_signatures_message[];
    };

    'payload-metadata.bin' contains all the bytes from the beginning of the
    payload, till the end of 'medatada_signature_message'.
    """
    payload_info = input_zip.getinfo('payload.bin')
    payload_offset = payload_info.header_offset
    payload_offset += zipfile.sizeFileHeader
    payload_offset += len(payload_info.extra) + len(payload_info.filename)
    payload_size = payload_info.file_size

    with input_zip.open('payload.bin') as payload_fp:
      header_bin = payload_fp.read(24)

    # network byte order (big-endian)
    header = struct.unpack("!IQQL", header_bin)

    # 'CrAU'
    magic = header[0]
    assert magic == 0x43724155, "Invalid magic: {:x}".format(magic)

    manifest_size = header[2]
    metadata_signature_size = header[3]
    metadata_total = 24 + manifest_size + metadata_signature_size
    assert metadata_total < payload_size

    return (payload_offset, metadata_total)


class NonAbOtaPropertyFiles(PropertyFiles):
  """The property-files for non-A/B OTA.

  For non-A/B OTA, the property-files string contains the info for METADATA
  entry, with which a system updater can be fetched the package metadata prior
  to downloading the entire package.
  """

  def __init__(self):
    super(NonAbOtaPropertyFiles, self).__init__()
    self.name = 'ota-property-files'


def FinalizeMetadata(metadata, input_file, output_file, needed_property_files):
  """Finalizes the metadata and signs an A/B OTA package.

  In order to stream an A/B OTA package, we need 'ota-streaming-property-files'
  that contains the offsets and sizes for the ZIP entries. An example
  property-files string is as follows.

    "payload.bin:679:343,payload_properties.txt:378:45,metadata:69:379"

  OTA server can pass down this string, in addition to the package URL, to the
  system update client. System update client can then fetch individual ZIP
  entries (ZIP_STORED) directly at the given offset of the URL.

  Args:
    metadata: The metadata dict for the package.
    input_file: The input ZIP filename that doesn't contain the package METADATA
        entry yet.
    output_file: The final output ZIP filename.
    needed_property_files: The list of PropertyFiles' to be generated.
  """

  def ComputeAllPropertyFiles(input_file, needed_property_files):
    # Write the current metadata entry with placeholders.
    with zipfile.ZipFile(input_file) as input_zip:
      for property_files in needed_property_files:
        metadata[property_files.name] = property_files.Compute(input_zip)
      namelist = input_zip.namelist()

    if METADATA_NAME in namelist:
      common.ZipDelete(input_file, METADATA_NAME)
    output_zip = zipfile.ZipFile(input_file, 'a')
    WriteMetadata(metadata, output_zip)
    common.ZipClose(output_zip)

    if OPTIONS.no_signing:
      return input_file

    prelim_signing = common.MakeTempFile(suffix='.zip')
    SignOutput(input_file, prelim_signing)
    return prelim_signing

  def FinalizeAllPropertyFiles(prelim_signing, needed_property_files):
    with zipfile.ZipFile(prelim_signing) as prelim_signing_zip:
      for property_files in needed_property_files:
        metadata[property_files.name] = property_files.Finalize(
            prelim_signing_zip, len(metadata[property_files.name]))

  # SignOutput(), which in turn calls signapk.jar, will possibly reorder the ZIP
  # entries, as well as padding the entry headers. We do a preliminary signing
  # (with an incomplete metadata entry) to allow that to happen. Then compute
  # the ZIP entry offsets, write back the final metadata and do the final
  # signing.
  prelim_signing = ComputeAllPropertyFiles(input_file, needed_property_files)
  try:
    FinalizeAllPropertyFiles(prelim_signing, needed_property_files)
  except PropertyFiles.InsufficientSpaceException:
    # Even with the preliminary signing, the entry orders may change
    # dramatically, which leads to insufficiently reserved space during the
    # first call to ComputeAllPropertyFiles(). In that case, we redo all the
    # preliminary signing works, based on the already ordered ZIP entries, to
    # address the issue.
    prelim_signing = ComputeAllPropertyFiles(
        prelim_signing, needed_property_files)
    FinalizeAllPropertyFiles(prelim_signing, needed_property_files)

  # Replace the METADATA entry.
  common.ZipDelete(prelim_signing, METADATA_NAME)
  output_zip = zipfile.ZipFile(prelim_signing, 'a')
  WriteMetadata(metadata, output_zip)
  common.ZipClose(output_zip)

  # Re-sign the package after updating the metadata entry.
  if OPTIONS.no_signing:
    output_file = prelim_signing
  else:
    SignOutput(prelim_signing, output_file)

  # Reopen the final signed zip to double check the streaming metadata.
  with zipfile.ZipFile(output_file) as output_zip:
    for property_files in needed_property_files:
      property_files.Verify(output_zip, metadata[property_files.name].strip())

  # If requested, dump the metadata to a separate file.
  output_metadata_path = OPTIONS.output_metadata_path
  if output_metadata_path:
    WriteMetadata(metadata, output_metadata_path)


def WriteBlockIncrementalOTAPackage(target_zip, source_zip, output_file):
  target_info = BuildInfo(OPTIONS.target_info_dict, OPTIONS.oem_dicts)
  source_info = BuildInfo(OPTIONS.source_info_dict, OPTIONS.oem_dicts)

  target_api_version = target_info["recovery_api_version"]
  source_api_version = source_info["recovery_api_version"]
  if source_api_version == 0:
    logger.warning(
        "Generating edify script for a source that can't install it.")

  script = edify_generator.EdifyGenerator(
      source_api_version, target_info, fstab=source_info["fstab"])

  if target_info.oem_props or source_info.oem_props:
    if not OPTIONS.oem_no_mount:
      source_info.WriteMountOemScript(script)

  metadata = GetPackageMetadata(target_info, source_info)

  if not OPTIONS.no_signing:
    staging_file = common.MakeTempFile(suffix='.zip')
  else:
    staging_file = output_file

  output_zip = zipfile.ZipFile(
      staging_file, "w", compression=zipfile.ZIP_DEFLATED)

  device_specific = common.DeviceSpecificParams(
      source_zip=source_zip,
      source_version=source_api_version,
      source_tmp=OPTIONS.source_tmp,
      target_zip=target_zip,
      target_version=target_api_version,
      target_tmp=OPTIONS.target_tmp,
      output_zip=output_zip,
      script=script,
      metadata=metadata,
      info_dict=source_info)

  source_boot = common.GetBootableImage(
      "/tmp/boot.img", "boot.img", OPTIONS.source_tmp, "BOOT", source_info)
  target_boot = common.GetBootableImage(
      "/tmp/boot.img", "boot.img", OPTIONS.target_tmp, "BOOT", target_info)
  updating_boot = (not OPTIONS.two_step and
                   (source_boot.data != target_boot.data))

  target_recovery = common.GetBootableImage(
      "/tmp/recovery.img", "recovery.img", OPTIONS.target_tmp, "RECOVERY")

  block_diff_dict = GetBlockDifferences(target_zip=target_zip,
                                        source_zip=source_zip,
                                        target_info=target_info,
                                        source_info=source_info,
                                        device_specific=device_specific)

  AddCompatibilityArchiveIfTrebleEnabled(
      target_zip, output_zip, target_info, source_info)

  # Assertions (e.g. device properties check).
  target_info.WriteDeviceAssertions(script, OPTIONS.oem_no_mount)
  device_specific.IncrementalOTA_Assertions()

  # Two-step incremental package strategy (in chronological order,
  # which is *not* the order in which the generated script has
  # things):
  #
  # if stage is not "2/3" or "3/3":
  #    do verification on current system
  #    write recovery image to boot partition
  #    set stage to "2/3"
  #    reboot to boot partition and restart recovery
  # else if stage is "2/3":
  #    write recovery image to recovery partition
  #    set stage to "3/3"
  #    reboot to recovery partition and restart recovery
  # else:
  #    (stage must be "3/3")
  #    perform update:
  #       patch system files, etc.
  #       force full install of new boot image
  #       set up system to update recovery partition on first boot
  #    complete script normally
  #    (allow recovery to mark itself finished and reboot)

  if OPTIONS.two_step:
    if not source_info.get("multistage_support"):
      assert False, "two-step packages not supported by this build"
    fs = source_info["fstab"]["/misc"]
    assert fs.fs_type.upper() == "EMMC", \
        "two-step packages only supported on devices with EMMC /misc partitions"
    bcb_dev = {"bcb_dev" : fs.device}
    common.ZipWriteStr(output_zip, "recovery.img", target_recovery.data)
    script.AppendExtra("""
if get_stage("%(bcb_dev)s") == "2/3" then
""" % bcb_dev)

    # Stage 2/3: Write recovery image to /recovery (currently running /boot).
    script.Comment("Stage 2/3")
    script.AppendExtra("sleep(20);\n")
    script.WriteRawImage("/recovery", "recovery.img")
    script.AppendExtra("""
set_stage("%(bcb_dev)s", "3/3");
reboot_now("%(bcb_dev)s", "recovery");
else if get_stage("%(bcb_dev)s") != "3/3" then
""" % bcb_dev)

    # Stage 1/3: (a) Verify the current system.
    script.Comment("Stage 1/3")

  # Dump fingerprints
  script.Print("Source: {}".format(source_info.fingerprint))
  script.Print("Target: {}".format(target_info.fingerprint))

  script.Print("Verifying current system...")

  device_specific.IncrementalOTA_VerifyBegin()

  WriteFingerprintAssertion(script, target_info, source_info)

  # Check the required cache size (i.e. stashed blocks).
  required_cache_sizes = [diff.required_cache for diff in
                          block_diff_dict.values()]
  if updating_boot:
    boot_type, boot_device = common.GetTypeAndDevice("/boot", source_info)
    d = common.Difference(target_boot, source_boot)
    _, _, d = d.ComputePatch()
    if d is None:
      include_full_boot = True
      common.ZipWriteStr(output_zip, "boot.img", target_boot.data)
    else:
      include_full_boot = False

      logger.info(
          "boot      target: %d  source: %d  diff: %d", target_boot.size,
          source_boot.size, len(d))

      common.ZipWriteStr(output_zip, "boot.img.p", d)

      script.PatchPartitionCheck(
          "{}:{}:{}:{}".format(
              boot_type, boot_device, target_boot.size, target_boot.sha1),
          "{}:{}:{}:{}".format(
              boot_type, boot_device, source_boot.size, source_boot.sha1))

      required_cache_sizes.append(target_boot.size)

  if required_cache_sizes:
    script.CacheFreeSpaceCheck(max(required_cache_sizes))

  # Verify the existing partitions.
  for diff in block_diff_dict.values():
    diff.WriteVerifyScript(script, touched_blocks_only=True)

  device_specific.IncrementalOTA_VerifyEnd()

  if OPTIONS.two_step:
    # Stage 1/3: (b) Write recovery image to /boot.
    _WriteRecoveryImageToBoot(script, output_zip)

    script.AppendExtra("""
set_stage("%(bcb_dev)s", "2/3");
reboot_now("%(bcb_dev)s", "");
else
""" % bcb_dev)

    # Stage 3/3: Make changes.
    script.Comment("Stage 3/3")

  script.Comment("---- start making changes here ----")

  device_specific.IncrementalOTA_InstallBegin()

  progress_dict = {partition: 0.1 for partition in block_diff_dict}
  progress_dict["system"] = 1 - len(block_diff_dict) * 0.1

  if OPTIONS.source_info_dict.get("use_dynamic_partitions") == "true":
    if OPTIONS.target_info_dict.get("use_dynamic_partitions") != "true":
      raise RuntimeError(
          "can't generate incremental that disables dynamic partitions")
    dynamic_partitions_diff = common.DynamicPartitionsDifference(
        info_dict=OPTIONS.target_info_dict,
        source_info_dict=OPTIONS.source_info_dict,
        block_diffs=block_diff_dict.values(),
        progress_dict=progress_dict)
    dynamic_partitions_diff.WriteScript(
        script, output_zip, write_verify_script=OPTIONS.verify)
  else:
    for block_diff in block_diff_dict.values():
      block_diff.WriteScript(script, output_zip,
                             progress=progress_dict.get(block_diff.partition),
                             write_verify_script=OPTIONS.verify)

  if OPTIONS.two_step:
    common.ZipWriteStr(output_zip, "boot.img", target_boot.data)
    script.WriteRawImage("/boot", "boot.img")
    logger.info("writing full boot image (forced by two-step mode)")

  if not OPTIONS.two_step:
    if updating_boot:
      if include_full_boot:
        logger.info("boot image changed; including full.")
        script.Print("Installing boot image...")
        script.WriteRawImage("/boot", "boot.img")
      else:
        # Produce the boot image by applying a patch to the current
        # contents of the boot partition, and write it back to the
        # partition.
        logger.info("boot image changed; including patch.")
        script.Print("Patching boot image...")
        script.ShowProgress(0.1, 10)
        script.PatchPartition(
            '{}:{}:{}:{}'.format(
                boot_type, boot_device, target_boot.size, target_boot.sha1),
            '{}:{}:{}:{}'.format(
                boot_type, boot_device, source_boot.size, source_boot.sha1),
            'boot.img.p')
    else:
      logger.info("boot image unchanged; skipping.")

  # Do device-specific installation (eg, write radio image).
  device_specific.IncrementalOTA_InstallEnd()

  if OPTIONS.extra_script is not None:
    script.AppendExtra(OPTIONS.extra_script)

  if OPTIONS.wipe_user_data:
    script.Print("Erasing user data...")
    script.FormatPartition("/data")

  if OPTIONS.two_step:
    script.AppendExtra("""
set_stage("%(bcb_dev)s", "");
endif;
endif;
""" % bcb_dev)

  script.SetProgress(1)
  # For downgrade OTAs, we prefer to use the update-binary in the source
  # build that is actually newer than the one in the target build.
  if OPTIONS.downgrade:
    script.AddToZip(source_zip, output_zip, input_path=OPTIONS.updater_binary)
  else:
    script.AddToZip(target_zip, output_zip, input_path=OPTIONS.updater_binary)
  metadata["ota-required-cache"] = str(script.required_cache)

  # We haven't written the metadata entry yet, which will be handled in
  # FinalizeMetadata().
  common.ZipClose(output_zip)

  # Sign the generated zip package unless no_signing is specified.
  needed_property_files = (
      NonAbOtaPropertyFiles(),
  )
  FinalizeMetadata(metadata, staging_file, output_file, needed_property_files)


def GetTargetFilesZipForSecondaryImages(input_file, skip_postinstall=False):
  """Returns a target-files.zip file for generating secondary payload.

  Although the original target-files.zip already contains secondary slot
  images (i.e. IMAGES/system_other.img), we need to rename the files to the
  ones without _other suffix. Note that we cannot instead modify the names in
  META/ab_partitions.txt, because there are no matching partitions on device.

  For the partitions that don't have secondary images, the ones for primary
  slot will be used. This is to ensure that we always have valid boot, vbmeta,
  bootloader images in the inactive slot.

  Args:
    input_file: The input target-files.zip file.
    skip_postinstall: Whether to skip copying the postinstall config file.

  Returns:
    The filename of the target-files.zip for generating secondary payload.
  """
  target_file = common.MakeTempFile(prefix="targetfiles-", suffix=".zip")
  target_zip = zipfile.ZipFile(target_file, 'w', allowZip64=True)

  with zipfile.ZipFile(input_file, 'r') as input_zip:
    infolist = input_zip.infolist()

  input_tmp = common.UnzipTemp(input_file, UNZIP_PATTERN)
  for info in infolist:
    unzipped_file = os.path.join(input_tmp, *info.filename.split('/'))
    if info.filename == 'IMAGES/system_other.img':
      common.ZipWrite(target_zip, unzipped_file, arcname='IMAGES/system.img')

    # Primary images and friends need to be skipped explicitly.
    elif info.filename in ('IMAGES/system.img',
                           'IMAGES/system.map'):
      pass

    # Skip copying the postinstall config if requested.
    elif skip_postinstall and info.filename == POSTINSTALL_CONFIG:
      pass

    elif info.filename.startswith(('META/', 'IMAGES/', 'RADIO/')):
      common.ZipWrite(target_zip, unzipped_file, arcname=info.filename)

  common.ZipClose(target_zip)

  return target_file


def GetTargetFilesZipWithoutPostinstallConfig(input_file):
  """Returns a target-files.zip that's not containing postinstall_config.txt.

  This allows brillo_update_payload script to skip writing all the postinstall
  hooks in the generated payload. The input target-files.zip file will be
  duplicated, with 'META/postinstall_config.txt' skipped. If input_file doesn't
  contain the postinstall_config.txt entry, the input file will be returned.

  Args:
    input_file: The input target-files.zip filename.

  Returns:
    The filename of target-files.zip that doesn't contain postinstall config.
  """
  # We should only make a copy if postinstall_config entry exists.
  with zipfile.ZipFile(input_file, 'r') as input_zip:
    if POSTINSTALL_CONFIG not in input_zip.namelist():
      return input_file

  target_file = common.MakeTempFile(prefix="targetfiles-", suffix=".zip")
  shutil.copyfile(input_file, target_file)
  common.ZipDelete(target_file, POSTINSTALL_CONFIG)
  return target_file


def GetTargetFilesZipForRetrofitDynamicPartitions(input_file,
                                                  super_block_devices,
                                                  dynamic_partition_list):
  """Returns a target-files.zip for retrofitting dynamic partitions.

  This allows brillo_update_payload to generate an OTA based on the exact
  bits on the block devices. Postinstall is disabled.

  Args:
    input_file: The input target-files.zip filename.
    super_block_devices: The list of super block devices
    dynamic_partition_list: The list of dynamic partitions

  Returns:
    The filename of target-files.zip with *.img replaced with super_*.img for
    each block device in super_block_devices.
  """
  assert super_block_devices, "No super_block_devices are specified."

  replace = {'OTA/super_{}.img'.format(dev): 'IMAGES/{}.img'.format(dev)
             for dev in super_block_devices}

  target_file = common.MakeTempFile(prefix="targetfiles-", suffix=".zip")
  shutil.copyfile(input_file, target_file)

  with zipfile.ZipFile(input_file) as input_zip:
    namelist = input_zip.namelist()

  input_tmp = common.UnzipTemp(input_file, RETROFIT_DAP_UNZIP_PATTERN)

  # Remove partitions from META/ab_partitions.txt that is in
  # dynamic_partition_list but not in super_block_devices so that
  # brillo_update_payload won't generate update for those logical partitions.
  ab_partitions_file = os.path.join(input_tmp, *AB_PARTITIONS.split('/'))
  with open(ab_partitions_file) as f:
    ab_partitions_lines = f.readlines()
    ab_partitions = [line.strip() for line in ab_partitions_lines]
  # Assert that all super_block_devices are in ab_partitions
  super_device_not_updated = [partition for partition in super_block_devices
                              if partition not in ab_partitions]
  assert not super_device_not_updated, \
      "{} is in super_block_devices but not in {}".format(
          super_device_not_updated, AB_PARTITIONS)
  # ab_partitions -= (dynamic_partition_list - super_block_devices)
  new_ab_partitions = common.MakeTempFile(prefix="ab_partitions", suffix=".txt")
  with open(new_ab_partitions, 'w') as f:
    for partition in ab_partitions:
      if (partition in dynamic_partition_list and
          partition not in super_block_devices):
        logger.info("Dropping %s from ab_partitions.txt", partition)
        continue
      f.write(partition + "\n")
  to_delete = [AB_PARTITIONS]

  # Always skip postinstall for a retrofit update.
  to_delete += [POSTINSTALL_CONFIG]

  # Delete dynamic_partitions_info.txt so that brillo_update_payload thinks this
  # is a regular update on devices without dynamic partitions support.
  to_delete += [DYNAMIC_PARTITION_INFO]

  # Remove the existing partition images as well as the map files.
  to_delete += list(replace.values())
  to_delete += ['IMAGES/{}.map'.format(dev) for dev in super_block_devices]

  common.ZipDelete(target_file, to_delete)

  target_zip = zipfile.ZipFile(target_file, 'a', allowZip64=True)

  # Write super_{foo}.img as {foo}.img.
  for src, dst in replace.items():
    assert src in namelist, \
        'Missing {} in {}; {} cannot be written'.format(src, input_file, dst)
    unzipped_file = os.path.join(input_tmp, *src.split('/'))
    common.ZipWrite(target_zip, unzipped_file, arcname=dst)

  # Write new ab_partitions.txt file
  common.ZipWrite(target_zip, new_ab_partitions, arcname=AB_PARTITIONS)

  common.ZipClose(target_zip)

  return target_file


def GenerateAbOtaPackage(target_file, output_file, source_file=None):
  """Generates an Android OTA package that has A/B update payload."""
  # Stage the output zip package for package signing.
  if not OPTIONS.no_signing:
    staging_file = common.MakeTempFile(suffix='.zip')
  else:
    staging_file = output_file
  output_zip = zipfile.ZipFile(staging_file, "w",
                               compression=zipfile.ZIP_DEFLATED)

  if source_file is not None:
    target_info = BuildInfo(OPTIONS.target_info_dict, OPTIONS.oem_dicts)
    source_info = BuildInfo(OPTIONS.source_info_dict, OPTIONS.oem_dicts)
  else:
    target_info = BuildInfo(OPTIONS.info_dict, OPTIONS.oem_dicts)
    source_info = None

  # Metadata to comply with Android OTA package format.
  metadata = GetPackageMetadata(target_info, source_info)

  if OPTIONS.retrofit_dynamic_partitions:
    target_file = GetTargetFilesZipForRetrofitDynamicPartitions(
        target_file, target_info.get("super_block_devices").strip().split(),
        target_info.get("dynamic_partition_list").strip().split())
  elif OPTIONS.skip_postinstall:
    target_file = GetTargetFilesZipWithoutPostinstallConfig(target_file)

  # Generate payload.
  payload = Payload()

  # Enforce a max timestamp this payload can be applied on top of.
  if OPTIONS.downgrade:
    max_timestamp = source_info.GetBuildProp("ro.build.date.utc")
  else:
    max_timestamp = metadata["post-timestamp"]
  additional_args = ["--max_timestamp", max_timestamp]

  payload.Generate(target_file, source_file, additional_args)

  # Sign the payload.
  payload_signer = PayloadSigner()
  payload.Sign(payload_signer)

  # Write the payload into output zip.
  payload.WriteToZip(output_zip)

  # Generate and include the secondary payload that installs secondary images
  # (e.g. system_other.img).
  if OPTIONS.include_secondary:
    # We always include a full payload for the secondary slot, even when
    # building an incremental OTA. See the comments for "--include_secondary".
    secondary_target_file = GetTargetFilesZipForSecondaryImages(
        target_file, OPTIONS.skip_postinstall)
    secondary_payload = Payload(secondary=True)
    secondary_payload.Generate(secondary_target_file,
                               additional_args=additional_args)
    secondary_payload.Sign(payload_signer)
    secondary_payload.WriteToZip(output_zip)

  # If dm-verity is supported for the device, copy contents of care_map
  # into A/B OTA package.
  target_zip = zipfile.ZipFile(target_file, "r")
  if (target_info.get("verity") == "true" or
      target_info.get("avb_enable") == "true"):
    care_map_list = [x for x in ["care_map.pb", "care_map.txt"] if
                     "META/" + x in target_zip.namelist()]

    # Adds care_map if either the protobuf format or the plain text one exists.
    if care_map_list:
      care_map_name = care_map_list[0]
      care_map_data = target_zip.read("META/" + care_map_name)
      # In order to support streaming, care_map needs to be packed as
      # ZIP_STORED.
      common.ZipWriteStr(output_zip, care_map_name, care_map_data,
                         compress_type=zipfile.ZIP_STORED)
    else:
      logger.warning("Cannot find care map file in target_file package")

  AddCompatibilityArchiveIfTrebleEnabled(
      target_zip, output_zip, target_info, source_info)

  common.ZipClose(target_zip)

  # We haven't written the metadata entry yet, which will be handled in
  # FinalizeMetadata().
  common.ZipClose(output_zip)

  # AbOtaPropertyFiles intends to replace StreamingPropertyFiles, as it covers
  # all the info of the latter. However, system updaters and OTA servers need to
  # take time to switch to the new flag. We keep both of the flags for
  # P-timeframe, and will remove StreamingPropertyFiles in later release.
  needed_property_files = (
      AbOtaPropertyFiles(),
      StreamingPropertyFiles(),
  )
  FinalizeMetadata(metadata, staging_file, output_file, needed_property_files)


def GenerateNonAbOtaPackage(target_file, output_file, source_file=None):
  """Generates a non-A/B OTA package."""
  # Sanity check the loaded info dicts first.
  if OPTIONS.info_dict.get("no_recovery") == "true":
    raise common.ExternalError(
        "--- target build has specified no recovery ---")

  # Non-A/B OTAs rely on /cache partition to store temporary files.
  cache_size = OPTIONS.info_dict.get("cache_size")
  if cache_size is None:
    logger.warning("--- can't determine the cache partition size ---")
  OPTIONS.cache_size = cache_size

  if OPTIONS.extra_script is not None:
    with open(OPTIONS.extra_script) as fp:
      OPTIONS.extra_script = fp.read()

  if OPTIONS.extracted_input is not None:
    OPTIONS.input_tmp = OPTIONS.extracted_input
  else:
    logger.info("unzipping target target-files...")
    OPTIONS.input_tmp = common.UnzipTemp(target_file, UNZIP_PATTERN)
  OPTIONS.target_tmp = OPTIONS.input_tmp

  # If the caller explicitly specified the device-specific extensions path via
  # -s / --device_specific, use that. Otherwise, use META/releasetools.py if it
  # is present in the target target_files. Otherwise, take the path of the file
  # from 'tool_extensions' in the info dict and look for that in the local
  # filesystem, relative to the current directory.
  if OPTIONS.device_specific is None:
    from_input = os.path.join(OPTIONS.input_tmp, "META", "releasetools.py")
    if os.path.exists(from_input):
      logger.info("(using device-specific extensions from target_files)")
      OPTIONS.device_specific = from_input
    else:
      OPTIONS.device_specific = OPTIONS.info_dict.get("tool_extensions")

  if OPTIONS.device_specific is not None:
    OPTIONS.device_specific = os.path.abspath(OPTIONS.device_specific)

  # Generate a full OTA.
  if source_file is None:
    with zipfile.ZipFile(target_file) as input_zip:
      WriteFullOTAPackage(
          input_zip,
          output_file)

  # Generate an incremental OTA.
  else:
    logger.info("unzipping source target-files...")
    OPTIONS.source_tmp = common.UnzipTemp(
        OPTIONS.incremental_source, UNZIP_PATTERN)
    with zipfile.ZipFile(target_file) as input_zip, \
        zipfile.ZipFile(source_file) as source_zip:
      WriteBlockIncrementalOTAPackage(
          input_zip,
          source_zip,
          output_file)


def main(argv):

  def option_handler(o, a):
    if o in ("-k", "--package_key"):
      OPTIONS.package_key = a
    elif o in ("-i", "--incremental_from"):
      OPTIONS.incremental_source = a
    elif o == "--full_radio":
      OPTIONS.full_radio = True
    elif o == "--full_bootloader":
      OPTIONS.full_bootloader = True
    elif o == "--wipe_user_data":
      OPTIONS.wipe_user_data = True
    elif o == "--downgrade":
      OPTIONS.downgrade = True
      OPTIONS.wipe_user_data = True
    elif o == "--override_timestamp":
      OPTIONS.downgrade = True
    elif o in ("-o", "--oem_settings"):
      OPTIONS.oem_source = a.split(',')
    elif o == "--oem_no_mount":
      OPTIONS.oem_no_mount = True
    elif o in ("-e", "--extra_script"):
      OPTIONS.extra_script = a
    elif o in ("-t", "--worker_threads"):
      if a.isdigit():
        OPTIONS.worker_threads = int(a)
      else:
        raise ValueError("Cannot parse value %r for option %r - only "
                         "integers are allowed." % (a, o))
    elif o in ("-2", "--two_step"):
      OPTIONS.two_step = True
    elif o == "--include_secondary":
      OPTIONS.include_secondary = True
    elif o == "--no_signing":
      OPTIONS.no_signing = True
    elif o == "--verify":
      OPTIONS.verify = True
    elif o == "--block":
      OPTIONS.block_based = True
    elif o in ("-b", "--binary"):
      OPTIONS.updater_binary = a
    elif o == "--stash_threshold":
      try:
        OPTIONS.stash_threshold = float(a)
      except ValueError:
        raise ValueError("Cannot parse value %r for option %r - expecting "
                         "a float" % (a, o))
    elif o == "--log_diff":
      OPTIONS.log_diff = a
    elif o == "--payload_signer":
      OPTIONS.payload_signer = a
    elif o == "--payload_signer_args":
      OPTIONS.payload_signer_args = shlex.split(a)
    elif o == "--payload_signer_key_size":
      OPTIONS.payload_signer_key_size = a
    elif o == "--extracted_input_target_files":
      OPTIONS.extracted_input = a
    elif o == "--skip_postinstall":
      OPTIONS.skip_postinstall = True
    elif o == "--retrofit_dynamic_partitions":
      OPTIONS.retrofit_dynamic_partitions = True
    elif o == "--skip_compatibility_check":
      OPTIONS.skip_compatibility_check = True
    elif o == "--output_metadata_path":
      OPTIONS.output_metadata_path = a
    elif o == "--disable_fec_computation":
      OPTIONS.disable_fec_computation = True
    else:
      return False
    return True

  args = common.ParseOptions(argv, __doc__,
                             extra_opts="b:k:i:d:e:t:2o:",
                             extra_long_opts=[
                                 "package_key=",
                                 "incremental_from=",
                                 "full_radio",
                                 "full_bootloader",
                                 "wipe_user_data",
                                 "downgrade",
                                 "override_timestamp",
                                 "extra_script=",
                                 "worker_threads=",
                                 "two_step",
                                 "include_secondary",
                                 "no_signing",
                                 "block",
                                 "binary=",
                                 "oem_settings=",
                                 "oem_no_mount",
                                 "verify",
                                 "stash_threshold=",
                                 "log_diff=",
                                 "payload_signer=",
                                 "payload_signer_args=",
                                 "payload_signer_key_size=",
                                 "extracted_input_target_files=",
                                 "skip_postinstall",
                                 "retrofit_dynamic_partitions",
                                 "skip_compatibility_check",
                                 "output_metadata_path=",
                                 "disable_fec_computation",
                             ], extra_option_handler=option_handler)

  if len(args) != 2:
    common.Usage(__doc__)
    sys.exit(1)

  common.InitLogging()

  if OPTIONS.downgrade:
    # We should only allow downgrading incrementals (as opposed to full).
    # Otherwise the device may go back from arbitrary build with this full
    # OTA package.
    if OPTIONS.incremental_source is None:
      raise ValueError("Cannot generate downgradable full OTAs")

  # Load the build info dicts from the zip directly or the extracted input
  # directory. We don't need to unzip the entire target-files zips, because they
  # won't be needed for A/B OTAs (brillo_update_payload does that on its own).
  # When loading the info dicts, we don't need to provide the second parameter
  # to common.LoadInfoDict(). Specifying the second parameter allows replacing
  # some properties with their actual paths, such as 'selinux_fc',
  # 'ramdisk_dir', which won't be used during OTA generation.
  if OPTIONS.extracted_input is not None:
    OPTIONS.info_dict = common.LoadInfoDict(OPTIONS.extracted_input)
  else:
    with zipfile.ZipFile(args[0], 'r') as input_zip:
      OPTIONS.info_dict = common.LoadInfoDict(input_zip)

  logger.info("--- target info ---")
  common.DumpInfoDict(OPTIONS.info_dict)

  # Load the source build dict if applicable.
  if OPTIONS.incremental_source is not None:
    OPTIONS.target_info_dict = OPTIONS.info_dict
    with zipfile.ZipFile(OPTIONS.incremental_source, 'r') as source_zip:
      OPTIONS.source_info_dict = common.LoadInfoDict(source_zip)

    logger.info("--- source info ---")
    common.DumpInfoDict(OPTIONS.source_info_dict)

  # Load OEM dicts if provided.
  OPTIONS.oem_dicts = _LoadOemDicts(OPTIONS.oem_source)

  # Assume retrofitting dynamic partitions when base build does not set
  # use_dynamic_partitions but target build does.
  if (OPTIONS.source_info_dict and
      OPTIONS.source_info_dict.get("use_dynamic_partitions") != "true" and
      OPTIONS.target_info_dict.get("use_dynamic_partitions") == "true"):
    if OPTIONS.target_info_dict.get("dynamic_partition_retrofit") != "true":
      raise common.ExternalError(
          "Expect to generate incremental OTA for retrofitting dynamic "
          "partitions, but dynamic_partition_retrofit is not set in target "
          "build.")
    logger.info("Implicitly generating retrofit incremental OTA.")
    OPTIONS.retrofit_dynamic_partitions = True

  # Skip postinstall for retrofitting dynamic partitions.
  if OPTIONS.retrofit_dynamic_partitions:
    OPTIONS.skip_postinstall = True

  ab_update = OPTIONS.info_dict.get("ab_update") == "true"

  # Use the default key to sign the package if not specified with package_key.
  # package_keys are needed on ab_updates, so always define them if an
  # ab_update is getting created.
  if not OPTIONS.no_signing or ab_update:
    if OPTIONS.package_key is None:
      OPTIONS.package_key = OPTIONS.info_dict.get(
          "default_system_dev_certificate",
          "build/make/target/product/security/testkey")
    # Get signing keys
    OPTIONS.key_passwords = common.GetKeyPasswords([OPTIONS.package_key])

  if ab_update:
    GenerateAbOtaPackage(
        target_file=args[0],
        output_file=args[1],
        source_file=OPTIONS.incremental_source)

  else:
    GenerateNonAbOtaPackage(
        target_file=args[0],
        output_file=args[1],
        source_file=OPTIONS.incremental_source)

  # Post OTA generation works.
  if OPTIONS.incremental_source is not None and OPTIONS.log_diff:
    logger.info("Generating diff logs...")
    logger.info("Unzipping target-files for diffing...")
    target_dir = common.UnzipTemp(args[0], TARGET_DIFFING_UNZIP_PATTERN)
    source_dir = common.UnzipTemp(
        OPTIONS.incremental_source, TARGET_DIFFING_UNZIP_PATTERN)

    with open(OPTIONS.log_diff, 'w') as out_file:
      import target_files_diff
      target_files_diff.recursiveDiff(
          '', source_dir, target_dir, out_file)

  logger.info("done.")


if __name__ == '__main__':
  try:
    common.CloseInheritedPipes()
    main(sys.argv[1:])
  except common.ExternalError:
    logger.exception("\n   ERROR:\n")
    sys.exit(1)
  finally:
    common.Cleanup()