diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index d0ee6ae..d09f60c 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -25,6 +25,7 @@
 import re
 import shlex
 import shutil
+import string
 import subprocess
 import sys
 import tempfile
@@ -34,6 +35,7 @@
 from hashlib import sha1, sha256
 
 import blockimgdiff
+import sparse_img
 
 class Options(object):
   def __init__(self):
@@ -124,6 +126,11 @@
   return subprocess.Popen(args, **kwargs)
 
 
+def RoundUpTo4K(value):
+  rounded_up = value + 4095
+  return rounded_up - (rounded_up % 4096)
+
+
 def CloseInheritedPipes():
   """ Gmake in MAC OS has file descriptor (PIPE) leak. We close those fds
   before doing other work."""
@@ -618,6 +625,56 @@
   return tmp, zipfile.ZipFile(filename, "r")
 
 
+def GetSparseImage(which, tmpdir, input_zip):
+  """Returns a SparseImage object suitable for passing to BlockImageDiff.
+
+  This function loads the specified sparse image from the given path, and
+  performs additional processing for OTA purpose. For example, it always adds
+  block 0 to clobbered blocks list. It also detects files that cannot be
+  reconstructed from the block list, for whom we should avoid applying imgdiff.
+
+  Args:
+    which: The partition name, which must be "system" or "vendor".
+    tmpdir: The directory that contains the prebuilt image and block map file.
+    input_zip: The target-files ZIP archive.
+
+  Returns:
+    A SparseImage object, with file_map info loaded.
+  """
+  assert which in ("system", "vendor")
+
+  path = os.path.join(tmpdir, "IMAGES", which + ".img")
+  mappath = os.path.join(tmpdir, "IMAGES", which + ".map")
+
+  # The image and map files must have been created prior to calling
+  # ota_from_target_files.py (since LMP).
+  assert os.path.exists(path) and os.path.exists(mappath)
+
+  # In ext4 filesystems, block 0 might be changed even being mounted R/O. We add
+  # it to clobbered_blocks so that it will be written to the target
+  # unconditionally. Note that they are still part of care_map. (Bug: 20939131)
+  clobbered_blocks = "0"
+
+  image = sparse_img.SparseImage(path, mappath, clobbered_blocks)
+
+  # block.map may contain less blocks, because mke2fs may skip allocating blocks
+  # if they contain all zeros. We can't reconstruct such a file from its block
+  # list. Tag such entries accordingly. (Bug: 65213616)
+  for entry in image.file_map:
+    # "/system/framework/am.jar" => "SYSTEM/framework/am.jar".
+    arcname = string.replace(entry, which, which.upper(), 1)[1:]
+    # Skip artificial names, such as "__ZERO", "__NONZERO-1".
+    if arcname not in input_zip.namelist():
+      continue
+
+    info = input_zip.getinfo(arcname)
+    ranges = image.file_map[entry]
+    if RoundUpTo4K(info.file_size) > ranges.size() * 4096:
+      ranges.extra['incomplete'] = True
+
+  return image
+
+
 def GetKeyPasswords(keylist):
   """Given a list of keys, prompt the user to enter passwords for
   those which require them.  Return a {key: password} dict.  password
diff --git a/tools/releasetools/ota_from_target_files.py b/tools/releasetools/ota_from_target_files.py
index ab6c9ad..12b01c4 100755
--- a/tools/releasetools/ota_from_target_files.py
+++ b/tools/releasetools/ota_from_target_files.py
@@ -140,7 +140,6 @@
 
 import common
 import edify_generator
-import sparse_img
 
 if sys.hexversion < 0x02070000:
   print("Python 2.7 or newer is required.", file=sys.stderr)
@@ -360,6 +359,122 @@
     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'
+
+  def __init__(self):
+    # The place where the output from the subprocess should go.
+    self._log_file = sys.stdout if OPTIONS.verbose else subprocess.PIPE
+    self.payload_file = None
+    self.payload_properties = None
+
+  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])
+    cmd.extend(additional_args)
+    p = common.Run(cmd, stdout=self._log_file, stderr=subprocess.STDOUT)
+    stdoutdata, _ = p.communicate()
+    assert p.returncode == 0, \
+        "brillo_update_payload generate failed: {}".format(stdoutdata)
+
+    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", "256",
+           "--metadata_hash_file", metadata_sig_file,
+           "--payload_hash_file", payload_sig_file]
+    p1 = common.Run(cmd, stdout=self._log_file, stderr=subprocess.STDOUT)
+    p1.communicate()
+    assert p1.returncode == 0, "brillo_update_payload hash failed"
+
+    # 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", "256",
+           "--metadata_signature_file", signed_metadata_sig_file,
+           "--payload_signature_file", signed_payload_sig_file]
+    p1 = common.Run(cmd, stdout=self._log_file, stderr=subprocess.STDOUT)
+    p1.communicate()
+    assert p1.returncode == 0, "brillo_update_payload sign failed"
+
+    # 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]
+    p1 = common.Run(cmd, stdout=self._log_file, stderr=subprocess.STDOUT)
+    p1.communicate()
+    assert p1.returncode == 0, "brillo_update_payload properties failed"
+
+    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
+
+    # 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.PAYLOAD_BIN,
+                    compress_type=zipfile.ZIP_STORED)
+    common.ZipWrite(output_zip, self.payload_properties,
+                    arcname=Payload.PAYLOAD_PROPERTIES_TXT,
+                    compress_type=zipfile.ZIP_STORED)
+
+
 def SignOutput(temp_zip_name, output_zip_name):
   pw = OPTIONS.key_passwords[OPTIONS.package_key]
 
@@ -452,31 +567,6 @@
         source_info.GetBuildProp("ro.build.thumbprint"))
 
 
-def GetImage(which, tmpdir):
-  """Returns an image object suitable for passing to BlockImageDiff.
-
-  'which' partition must be "system" or "vendor". A prebuilt image and file
-  map must already exist in tmpdir.
-  """
-
-  assert which in ("system", "vendor")
-
-  path = os.path.join(tmpdir, "IMAGES", which + ".img")
-  mappath = os.path.join(tmpdir, "IMAGES", which + ".map")
-
-  # The image and map files must have been created prior to calling
-  # ota_from_target_files.py (since LMP).
-  assert os.path.exists(path) and os.path.exists(mappath)
-
-  # Bug: http://b/20939131
-  # In ext4 filesystems, block 0 might be changed even being mounted
-  # R/O. We add it to clobbered_blocks so that it will be written to the
-  # target unconditionally. Note that they are still part of care_map.
-  clobbered_blocks = "0"
-
-  return sparse_img.SparseImage(path, mappath, clobbered_blocks)
-
-
 def AddCompatibilityArchiveIfTrebleEnabled(target_zip, output_zip, target_info,
                                            source_info=None):
   """Adds compatibility info into the output zip if it's Treble-enabled target.
@@ -662,7 +752,7 @@
   # has the effect of writing new data from the package to the entire
   # partition, but lets us reuse the updater code that writes incrementals to
   # do it.
-  system_tgt = GetImage("system", OPTIONS.input_tmp)
+  system_tgt = common.GetSparseImage("system", OPTIONS.input_tmp, input_zip)
   system_tgt.ResetFileMap()
   system_diff = common.BlockDifference("system", system_tgt, src=None)
   system_diff.WriteScript(script, output_zip)
@@ -673,7 +763,7 @@
   if HasVendorPartition(input_zip):
     script.ShowProgress(0.1, 0)
 
-    vendor_tgt = GetImage("vendor", OPTIONS.input_tmp)
+    vendor_tgt = common.GetSparseImage("vendor", OPTIONS.input_tmp, input_zip)
     vendor_tgt.ResetFileMap()
     vendor_diff = common.BlockDifference("vendor", vendor_tgt)
     vendor_diff.WriteScript(script, output_zip)
@@ -778,6 +868,10 @@
       '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:
@@ -846,8 +940,8 @@
   target_recovery = common.GetBootableImage(
       "/tmp/recovery.img", "recovery.img", OPTIONS.target_tmp, "RECOVERY")
 
-  system_src = GetImage("system", OPTIONS.source_tmp)
-  system_tgt = GetImage("system", OPTIONS.target_tmp)
+  system_src = common.GetSparseImage("system", OPTIONS.source_tmp, source_zip)
+  system_tgt = common.GetSparseImage("system", OPTIONS.target_tmp, target_zip)
 
   blockimgdiff_version = max(
       int(i) for i in target_info.get("blockimgdiff_versions", "1").split(","))
@@ -872,8 +966,8 @@
   if HasVendorPartition(target_zip):
     if not HasVendorPartition(source_zip):
       raise RuntimeError("can't generate incremental that adds /vendor")
-    vendor_src = GetImage("vendor", OPTIONS.source_tmp)
-    vendor_tgt = GetImage("vendor", OPTIONS.target_tmp)
+    vendor_src = common.GetSparseImage("vendor", OPTIONS.source_tmp, source_zip)
+    vendor_tgt = common.GetSparseImage("vendor", OPTIONS.target_tmp, target_zip)
 
     # Check first block of vendor partition for remount R/W only if
     # disk type is ext4
@@ -1122,12 +1216,6 @@
       value += ' ' * (expected_length - len(value))
     return value
 
-  # The place where the output from the subprocess should go.
-  log_file = sys.stdout if OPTIONS.verbose else subprocess.PIPE
-
-  # Get the PayloadSigner to be used in step 3.
-  payload_signer = PayloadSigner()
-
   # Stage the output zip package for package signing.
   temp_zip_file = tempfile.NamedTemporaryFile()
   output_zip = zipfile.ZipFile(temp_zip_file, "w",
@@ -1143,72 +1231,15 @@
   # Metadata to comply with Android OTA package format.
   metadata = GetPackageMetadata(target_info, source_info)
 
-  # 1. Generate payload.
-  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])
-  p1 = common.Run(cmd, stdout=log_file, stderr=subprocess.STDOUT)
-  p1.communicate()
-  assert p1.returncode == 0, "brillo_update_payload generate failed"
+  # Generate payload.
+  payload = Payload()
+  payload.Generate(target_file, source_file)
 
-  # 2. 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", payload_file,
-         "--signature_size", "256",
-         "--metadata_hash_file", metadata_sig_file,
-         "--payload_hash_file", payload_sig_file]
-  p1 = common.Run(cmd, stdout=log_file, stderr=subprocess.STDOUT)
-  p1.communicate()
-  assert p1.returncode == 0, "brillo_update_payload hash failed"
+  # Sign the payload.
+  payload.Sign(PayloadSigner())
 
-  # 3. Sign the hashes and insert them back into the payload file.
-  # 3a. Sign the payload hash.
-  signed_payload_sig_file = payload_signer.Sign(payload_sig_file)
-
-  # 3b. Sign the metadata hash.
-  signed_metadata_sig_file = payload_signer.Sign(metadata_sig_file)
-
-  # 3c. 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", payload_file,
-         "--payload", signed_payload_file,
-         "--signature_size", "256",
-         "--metadata_signature_file", signed_metadata_sig_file,
-         "--payload_signature_file", signed_payload_sig_file]
-  p1 = common.Run(cmd, stdout=log_file, stderr=subprocess.STDOUT)
-  p1.communicate()
-  assert p1.returncode == 0, "brillo_update_payload sign failed"
-
-  # 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]
-  p1 = common.Run(cmd, stdout=log_file, stderr=subprocess.STDOUT)
-  p1.communicate()
-  assert p1.returncode == 0, "brillo_update_payload properties failed"
-
-  if OPTIONS.wipe_user_data:
-    with open(properties_file, "a") as f:
-      f.write("POWERWASH=1\n")
-
-  # Add the signed payload file and properties into the zip. In order to
-  # support streaming, we pack payload.bin, payload_properties.txt and
-  # care_map.txt as ZIP_STORED. So these entries can be read directly with
-  # the offset and length pairs.
-  common.ZipWrite(output_zip, signed_payload_file, arcname="payload.bin",
-                  compress_type=zipfile.ZIP_STORED)
-  common.ZipWrite(output_zip, properties_file,
-                  arcname="payload_properties.txt",
-                  compress_type=zipfile.ZIP_STORED)
+  # Write the payload into output zip.
+  payload.WriteToZip(output_zip)
 
   # If dm-verity is supported for the device, copy contents of care_map
   # into A/B OTA package.
@@ -1219,6 +1250,8 @@
     namelist = target_zip.namelist()
     if care_map_path in namelist:
       care_map_data = target_zip.read(care_map_path)
+      # In order to support streaming, care_map.txt needs to be packed as
+      # ZIP_STORED.
       common.ZipWriteStr(output_zip, "care_map.txt", care_map_data,
                          compress_type=zipfile.ZIP_STORED)
     else:
diff --git a/tools/releasetools/rangelib.py b/tools/releasetools/rangelib.py
index 87380a5..8af61c3 100644
--- a/tools/releasetools/rangelib.py
+++ b/tools/releasetools/rangelib.py
@@ -25,6 +25,7 @@
 
   def __init__(self, data=None):
     self.monotonic = False
+    self._extra = {}
     if isinstance(data, str):
       self._parse_internal(data)
     elif data:
@@ -56,6 +57,10 @@
   def __repr__(self):
     return '<RangeSet("' + self.to_string() + '")>'
 
+  @property
+  def extra(self):
+    return self._extra
+
   @classmethod
   def parse(cls, text):
     """Parse a text string consisting of a space-separated list of
diff --git a/tools/releasetools/test_ota_from_target_files.py b/tools/releasetools/test_ota_from_target_files.py
index fa6655b..de03be3 100644
--- a/tools/releasetools/test_ota_from_target_files.py
+++ b/tools/releasetools/test_ota_from_target_files.py
@@ -15,12 +15,14 @@
 #
 
 import copy
+import os
 import os.path
 import unittest
+import zipfile
 
 import common
 from ota_from_target_files import (
-    _LoadOemDicts, BuildInfo, GetPackageMetadata, PayloadSigner,
+    _LoadOemDicts, BuildInfo, GetPackageMetadata, Payload, PayloadSigner,
     WriteFingerprintAssertion)
 
 
@@ -318,6 +320,8 @@
           'ro.product.device' : 'product-device',
           'ro.build.fingerprint' : 'build-fingerprint-target',
           'ro.build.version.incremental' : 'build-version-incremental-target',
+          'ro.build.version.sdk' : '27',
+          'ro.build.version.security_patch' : '2017-12-01',
           'ro.build.date.utc' : '1500000000',
       },
   }
@@ -327,6 +331,8 @@
           'ro.product.device' : 'product-device',
           'ro.build.fingerprint' : 'build-fingerprint-source',
           'ro.build.version.incremental' : 'build-version-incremental-source',
+          'ro.build.version.sdk' : '25',
+          'ro.build.version.security_patch' : '2016-12-01',
           'ro.build.date.utc' : '1400000000',
       },
   }
@@ -349,6 +355,8 @@
             'ota-required-cache' : '0',
             'post-build' : 'build-fingerprint-target',
             'post-build-incremental' : 'build-version-incremental-target',
+            'post-sdk-level' : '27',
+            'post-security-patch-level' : '2017-12-01',
             'post-timestamp' : '1500000000',
             'pre-device' : 'product-device',
         },
@@ -367,6 +375,8 @@
             'ota-required-cache' : '0',
             'post-build' : 'build-fingerprint-target',
             'post-build-incremental' : 'build-version-incremental-target',
+            'post-sdk-level' : '27',
+            'post-security-patch-level' : '2017-12-01',
             'post-timestamp' : '1500000000',
             'pre-device' : 'product-device',
             'pre-build' : 'build-fingerprint-source',
@@ -382,6 +392,8 @@
             'ota-type' : 'BLOCK',
             'post-build' : 'build-fingerprint-target',
             'post-build-incremental' : 'build-version-incremental-target',
+            'post-sdk-level' : '27',
+            'post-security-patch-level' : '2017-12-01',
             'post-timestamp' : '1500000000',
             'pre-device' : 'product-device',
         },
@@ -397,6 +409,8 @@
             'ota-type' : 'BLOCK',
             'post-build' : 'build-fingerprint-target',
             'post-build-incremental' : 'build-version-incremental-target',
+            'post-sdk-level' : '27',
+            'post-security-patch-level' : '2017-12-01',
             'post-timestamp' : '1500000000',
             'pre-device' : 'product-device',
             'pre-build' : 'build-fingerprint-source',
@@ -414,6 +428,8 @@
             'ota-wipe' : 'yes',
             'post-build' : 'build-fingerprint-target',
             'post-build-incremental' : 'build-version-incremental-target',
+            'post-sdk-level' : '27',
+            'post-security-patch-level' : '2017-12-01',
             'post-timestamp' : '1500000000',
             'pre-device' : 'product-device',
         },
@@ -457,6 +473,8 @@
             'ota-wipe' : 'yes',
             'post-build' : 'build-fingerprint-target',
             'post-build-incremental' : 'build-version-incremental-target',
+            'post-sdk-level' : '27',
+            'post-security-patch-level' : '2017-12-01',
             'pre-device' : 'product-device',
             'pre-build' : 'build-fingerprint-source',
             'pre-build-incremental' : 'build-version-incremental-source',
@@ -479,6 +497,8 @@
             'ota-type' : 'BLOCK',
             'post-build' : 'build-fingerprint-target',
             'post-build-incremental' : 'build-version-incremental-target',
+            'post-sdk-level' : '27',
+            'post-security-patch-level' : '2017-12-01',
             'post-timestamp' : '1500000001',
             'pre-device' : 'product-device',
             'pre-build' : 'build-fingerprint-source',
@@ -564,3 +584,157 @@
 
     verify_file = os.path.join(self.testdata_dir, self.SIGNED_SIGFILE)
     self._assertFilesEqual(verify_file, signed_file)
+
+
+class PayloadTest(unittest.TestCase):
+
+  def setUp(self):
+    self.testdata_dir = get_testdata_dir()
+    self.assertTrue(os.path.exists(self.testdata_dir))
+
+    common.OPTIONS.wipe_user_data = False
+    common.OPTIONS.payload_signer = None
+    common.OPTIONS.payload_signer_args = None
+    common.OPTIONS.package_key = os.path.join(self.testdata_dir, 'testkey')
+    common.OPTIONS.key_passwords = {
+        common.OPTIONS.package_key : None,
+    }
+
+  def tearDown(self):
+    common.Cleanup()
+
+  @staticmethod
+  def _construct_target_files():
+    target_files = common.MakeTempFile(prefix='target_files-', suffix='.zip')
+    with zipfile.ZipFile(target_files, 'w') as target_files_zip:
+      # META/update_engine_config.txt
+      target_files_zip.writestr(
+          'META/update_engine_config.txt',
+          "PAYLOAD_MAJOR_VERSION=2\nPAYLOAD_MINOR_VERSION=4\n")
+
+      # META/ab_partitions.txt
+      ab_partitions = ['boot', 'system', 'vendor']
+      target_files_zip.writestr(
+          'META/ab_partitions.txt',
+          '\n'.join(ab_partitions))
+
+      # Create dummy images for each of them.
+      for partition in ab_partitions:
+        target_files_zip.writestr('IMAGES/' + partition + '.img',
+                                  os.urandom(len(partition)))
+
+    return target_files
+
+  def _create_payload_full(self):
+    target_file = self._construct_target_files()
+    payload = Payload()
+    payload.Generate(target_file)
+    return payload
+
+  def _create_payload_incremental(self):
+    target_file = self._construct_target_files()
+    source_file = self._construct_target_files()
+    payload = Payload()
+    payload.Generate(target_file, source_file)
+    return payload
+
+  def test_Generate_full(self):
+    payload = self._create_payload_full()
+    self.assertTrue(os.path.exists(payload.payload_file))
+
+  def test_Generate_incremental(self):
+    payload = self._create_payload_incremental()
+    self.assertTrue(os.path.exists(payload.payload_file))
+
+  def test_Generate_additionalArgs(self):
+    target_file = self._construct_target_files()
+    source_file = self._construct_target_files()
+    payload = Payload()
+    # This should work the same as calling payload.Generate(target_file,
+    # source_file).
+    payload.Generate(
+        target_file, additional_args=["--source_image", source_file])
+    self.assertTrue(os.path.exists(payload.payload_file))
+
+  def test_Generate_invalidInput(self):
+    target_file = self._construct_target_files()
+    common.ZipDelete(target_file, 'IMAGES/vendor.img')
+    payload = Payload()
+    self.assertRaises(AssertionError, payload.Generate, target_file)
+
+  def test_Sign_full(self):
+    payload = self._create_payload_full()
+    payload.Sign(PayloadSigner())
+
+    output_file = common.MakeTempFile(suffix='.zip')
+    with zipfile.ZipFile(output_file, 'w') as output_zip:
+      payload.WriteToZip(output_zip)
+
+    import check_ota_package_signature
+    check_ota_package_signature.VerifyAbOtaPayload(
+        os.path.join(self.testdata_dir, 'testkey.x509.pem'),
+        output_file)
+
+  def test_Sign_incremental(self):
+    payload = self._create_payload_incremental()
+    payload.Sign(PayloadSigner())
+
+    output_file = common.MakeTempFile(suffix='.zip')
+    with zipfile.ZipFile(output_file, 'w') as output_zip:
+      payload.WriteToZip(output_zip)
+
+    import check_ota_package_signature
+    check_ota_package_signature.VerifyAbOtaPayload(
+        os.path.join(self.testdata_dir, 'testkey.x509.pem'),
+        output_file)
+
+  def test_Sign_withDataWipe(self):
+    common.OPTIONS.wipe_user_data = True
+    payload = self._create_payload_full()
+    payload.Sign(PayloadSigner())
+
+    with open(payload.payload_properties) as properties_fp:
+      self.assertIn("POWERWASH=1", properties_fp.read())
+
+  def test_Sign_badSigner(self):
+    """Tests that signing failure can be captured."""
+    payload = self._create_payload_full()
+    payload_signer = PayloadSigner()
+    payload_signer.signer_args.append('bad-option')
+    self.assertRaises(AssertionError, payload.Sign, payload_signer)
+
+  def test_WriteToZip(self):
+    payload = self._create_payload_full()
+    payload.Sign(PayloadSigner())
+
+    output_file = common.MakeTempFile(suffix='.zip')
+    with zipfile.ZipFile(output_file, 'w') as output_zip:
+      payload.WriteToZip(output_zip)
+
+    with zipfile.ZipFile(output_file) as verify_zip:
+      # First make sure we have the essential entries.
+      namelist = verify_zip.namelist()
+      self.assertIn(Payload.PAYLOAD_BIN, namelist)
+      self.assertIn(Payload.PAYLOAD_PROPERTIES_TXT, namelist)
+
+      # Then assert these entries are stored.
+      for entry_info in verify_zip.infolist():
+        if entry_info.filename not in (Payload.PAYLOAD_BIN,
+                                       Payload.PAYLOAD_PROPERTIES_TXT):
+          continue
+        self.assertEqual(zipfile.ZIP_STORED, entry_info.compress_type)
+
+  def test_WriteToZip_unsignedPayload(self):
+    """Unsigned payloads should not be allowed to be written to zip."""
+    payload = self._create_payload_full()
+
+    output_file = common.MakeTempFile(suffix='.zip')
+    with zipfile.ZipFile(output_file, 'w') as output_zip:
+      self.assertRaises(AssertionError, payload.WriteToZip, output_zip)
+
+    # Also test with incremental payload.
+    payload = self._create_payload_incremental()
+
+    output_file = common.MakeTempFile(suffix='.zip')
+    with zipfile.ZipFile(output_file, 'w') as output_zip:
+      self.assertRaises(AssertionError, payload.WriteToZip, output_zip)
diff --git a/tools/releasetools/validate_target_files.py b/tools/releasetools/validate_target_files.py
index b590392..1b3eb73 100755
--- a/tools/releasetools/validate_target_files.py
+++ b/tools/releasetools/validate_target_files.py
@@ -29,35 +29,17 @@
 import sys
 
 import common
-import sparse_img
-
-
-def _GetImage(which, tmpdir):
-  assert which in ('system', 'vendor')
-
-  path = os.path.join(tmpdir, 'IMAGES', which + '.img')
-  mappath = os.path.join(tmpdir, 'IMAGES', which + '.map')
-
-  # Map file must exist (allowed to be empty).
-  assert os.path.exists(path) and os.path.exists(mappath)
-
-  clobbered_blocks = '0'
-  return sparse_img.SparseImage(path, mappath, clobbered_blocks)
 
 
 def _ReadFile(file_name, unpacked_name, round_up=False):
   """Constructs and returns a File object. Rounds up its size if needed."""
 
-  def RoundUpTo4K(value):
-    rounded_up = value + 4095
-    return rounded_up - (rounded_up % 4096)
-
   assert os.path.exists(unpacked_name)
   with open(unpacked_name, 'r') as f:
     file_data = f.read()
   file_size = len(file_data)
   if round_up:
-    file_size_rounded_up = RoundUpTo4K(file_size)
+    file_size_rounded_up = common.RoundUpTo4K(file_size)
     file_data += '\0' * (file_size_rounded_up - file_size)
   return common.File(file_name, file_data)
 
@@ -79,33 +61,28 @@
 
   def CheckAllFiles(which):
     logging.info('Checking %s image.', which)
-    image = _GetImage(which, input_tmp)
+    image = common.GetSparseImage(which, input_tmp, input_zip)
     prefix = '/' + which
     for entry in image.file_map:
+      # Skip entries like '__NONZERO-0'.
       if not entry.startswith(prefix):
         continue
 
       # Read the blocks that the file resides. Note that it will contain the
       # bytes past the file length, which is expected to be padded with '\0's.
       ranges = image.file_map[entry]
+
+      incomplete = ranges.extra.get('incomplete', False)
+      if incomplete:
+        logging.warning('Skipping %s that has incomplete block list', entry)
+        continue
+
       blocks_sha1 = image.RangeSha1(ranges)
 
       # The filename under unpacked directory, such as SYSTEM/bin/sh.
       unpacked_name = os.path.join(
           input_tmp, which.upper(), entry[(len(prefix) + 1):])
       unpacked_file = _ReadFile(entry, unpacked_name, True)
-      file_size = unpacked_file.size
-
-      # block.map may contain less blocks, because mke2fs may skip allocating
-      # blocks if they contain all zeros. We can't reconstruct such a file from
-      # its block list. (Bug: 65213616)
-      if file_size > ranges.size() * 4096:
-        logging.warning(
-            'Skipping %s that has less blocks: file size %d-byte,'
-            ' ranges %s (%d-byte)', entry, file_size, ranges,
-            ranges.size() * 4096)
-        continue
-
       file_sha1 = unpacked_file.sha1
       assert blocks_sha1 == file_sha1, \
           'file: %s, range: %s, blocks_sha1: %s, file_sha1: %s' % (