Merge "releasetools: Create VerityImageBuilder."

tools/releasetools/build_image.py

@@ -248,20 +248,9 @@ def BuildImage(in_dir, prop_dict, out_file, target_out=None):
   if fs_type.startswith("squash"):
     fs_spans_partition = False
 
-  is_verity_partition = "verity_block_device" in prop_dict
+  # Get a builder for creating an image that's to be verified by Verified Boot,
-  verity_supported = prop_dict.get("verity") == "true"
+  # or None if not applicable.
-  verity_fec_supported = prop_dict.get("verity_fec") == "true"
+  verity_image_builder = verity_utils.CreateVerityImageBuilder(prop_dict)
-
-  avb_footer_type = None
-  if prop_dict.get("avb_hash_enable") == "true":
-    avb_footer_type = "hash"
-  elif prop_dict.get("avb_hashtree_enable") == "true":
-    avb_footer_type = "hashtree"
-
-  if avb_footer_type:
-    avbtool = prop_dict.get("avb_avbtool")
-    avb_signing_args = prop_dict.get(
-        "avb_add_" + avb_footer_type + "_footer_args")
 
   if (prop_dict.get("use_dynamic_partition_size") == "true" and
       "partition_size" not in prop_dict):
@@ -273,13 +262,8 @@ def BuildImage(in_dir, prop_dict, out_file, target_out=None):
     size += int(prop_dict.get("partition_reserved_size", BYTES_IN_MB * 16))
     # Round this up to a multiple of 4K so that avbtool works
     size = common.RoundUpTo4K(size)
-    # Adjust partition_size to add more space for AVB footer, to prevent
+    if verity_image_builder:
-    # it from consuming partition_reserved_size.
+      size = verity_image_builder.CalculateDynamicPartitionSize(size)
-    if avb_footer_type:
-      size = verity_utils.AVBCalcMinPartitionSize(
-          size,
-          lambda x: verity_utils.AVBCalcMaxImageSize(
-              avbtool, avb_footer_type, x, avb_signing_args))
     prop_dict["partition_size"] = str(size)
     if fs_type.startswith("ext"):
       if "extfs_inode_count" not in prop_dict:
@@ -316,19 +300,8 @@ def BuildImage(in_dir, prop_dict, out_file, target_out=None):
   prop_dict["image_size"] = prop_dict["partition_size"]
 
   # Adjust the image size to make room for the hashes if this is to be verified.
-  if verity_supported and is_verity_partition:
+  if verity_image_builder:
-    partition_size = int(prop_dict.get("partition_size"))
+    max_image_size = verity_image_builder.CalculateMaxImageSize()
-    image_size, verity_size = verity_utils.AdjustPartitionSizeForVerity(
-        partition_size, verity_fec_supported)
-    prop_dict["image_size"] = str(image_size)
-    prop_dict["verity_size"] = str(verity_size)
-
-  # Adjust the image size for AVB hash footer or AVB hashtree footer.
-  if avb_footer_type:
-    partition_size = prop_dict["partition_size"]
-    # avb_add_hash_footer_args or avb_add_hashtree_footer_args.
-    max_image_size = verity_utils.AVBCalcMaxImageSize(
-        avbtool, avb_footer_type, partition_size, avb_signing_args)
     prop_dict["image_size"] = str(max_image_size)
 
   if fs_type.startswith("ext"):
@@ -441,33 +414,12 @@ def BuildImage(in_dir, prop_dict, out_file, target_out=None):
   if "partition_headroom" in prop_dict and fs_type.startswith("ext4"):
     CheckHeadroom(mkfs_output, prop_dict)
 
-  if not fs_spans_partition:
+  if not fs_spans_partition and verity_image_builder:
-    mount_point = prop_dict.get("mount_point")
+    verity_image_builder.PadSparseImage(out_file)
-    image_size = int(prop_dict["image_size"])
-    sparse_image_size = verity_utils.GetSimgSize(out_file)
-    if sparse_image_size > image_size:
-      raise BuildImageError(
-          "Error: {} image size of {} is larger than partition size of "
-          "{}".format(mount_point, sparse_image_size, image_size))
-    if verity_supported and is_verity_partition:
-      verity_utils.ZeroPadSimg(out_file, image_size - sparse_image_size)
 
   # Create the verified image if this is to be verified.
-  if verity_supported and is_verity_partition:
+  if verity_image_builder:
-    verity_utils.MakeVerityEnabledImage(
+    verity_image_builder.Build(out_file)
-        out_file, verity_fec_supported, prop_dict)
-
-  # Add AVB HASH or HASHTREE footer (metadata).
-  if avb_footer_type:
-    partition_size = prop_dict["partition_size"]
-    partition_name = prop_dict["partition_name"]
-    # key_path and algorithm are only available when chain partition is used.
-    key_path = prop_dict.get("avb_key_path")
-    algorithm = prop_dict.get("avb_algorithm")
-    salt = prop_dict.get("avb_salt")
-    verity_utils.AVBAddFooter(
-        out_file, avbtool, avb_footer_type, partition_size, partition_name,
-        key_path, algorithm, salt, avb_signing_args)
 
   if run_e2fsck and prop_dict.get("skip_fsck") != "true":
     unsparse_image = UnsparseImage(out_file, replace=False)

tools/releasetools/test_validate_target_files.py

@@ -24,6 +24,7 @@ import common
 import test_utils
 import verity_utils
 from validate_target_files import ValidateVerifiedBootImages
+from verity_utils import CreateVerityImageBuilder
 
 
 class ValidateTargetFilesTest(test_utils.ReleaseToolsTestCase):
@@ -107,10 +108,16 @@ class ValidateTargetFilesTest(test_utils.ReleaseToolsTestCase):
         options)
 
   def _generate_system_image(self, output_file):
-    verity_fec = True
+    prop_dict = {
-    partition_size = 1024 * 1024
+        'partition_size': str(1024 * 1024),
-    image_size, verity_size = verity_utils.AdjustPartitionSizeForVerity(
+        'verity': 'true',
-        partition_size, verity_fec)
+        'verity_block_device': '/dev/block/system',
+        'verity_key' : os.path.join(self.testdata_dir, 'testkey'),
+        'verity_fec': "true",
+        'verity_signer_cmd': 'verity_signer',
+    }
+    verity_image_builder = CreateVerityImageBuilder(prop_dict)
+    image_size = verity_image_builder.CalculateMaxImageSize()
 
     # Use an empty root directory.
     system_root = common.MakeTempDir()
@@ -124,15 +131,7 @@ class ValidateTargetFilesTest(test_utils.ReleaseToolsTestCase):
             stdoutdata))
 
     # Append the verity metadata.
-    prop_dict = {
+    verity_image_builder.Build(output_file)
-        'partition_size' : str(partition_size),
-        'image_size' : str(image_size),
-        'verity_block_device' : '/dev/block/system',
-        'verity_key' : os.path.join(self.testdata_dir, 'testkey'),
-        'verity_signer_cmd' : 'verity_signer',
-        'verity_size' : str(verity_size),
-    }
-    verity_utils.MakeVerityEnabledImage(output_file, verity_fec, prop_dict)
 
   def test_ValidateVerifiedBootImages_systemImage(self):
     input_tmp = common.MakeTempDir()

tools/releasetools/test_verity_utils.py

@@ -25,10 +25,11 @@ import sparse_img
 from rangelib import RangeSet
 from test_utils import get_testdata_dir, ReleaseToolsTestCase
 from verity_utils import (
-    AdjustPartitionSizeForVerity, AVBCalcMinPartitionSize, BLOCK_SIZE,
+    CreateHashtreeInfoGenerator, CreateVerityImageBuilder, HashtreeInfo,
-    CreateHashtreeInfoGenerator, HashtreeInfo, MakeVerityEnabledImage,
     VerifiedBootVersion1HashtreeInfoGenerator)
 
+BLOCK_SIZE = common.BLOCK_SIZE
+
 
 class VerifiedBootVersion1HashtreeInfoGeneratorTest(ReleaseToolsTestCase):
 
@@ -64,8 +65,17 @@ class VerifiedBootVersion1HashtreeInfoGeneratorTest(ReleaseToolsTestCase):
 
   def _generate_image(self):
     partition_size = 1024 * 1024
-    adjusted_size, verity_size = AdjustPartitionSizeForVerity(
+    prop_dict = {
-        partition_size, True)
+        'partition_size': str(partition_size),
+        'verity': 'true',
+        'verity_block_device': '/dev/block/system',
+        'verity_key': os.path.join(self.testdata_dir, 'testkey'),
+        'verity_fec': 'true',
+        'verity_signer_cmd': 'verity_signer',
+    }
+    verity_image_builder = CreateVerityImageBuilder(prop_dict)
+    self.assertIsNotNone(verity_image_builder)
+    adjusted_size = verity_image_builder.CalculateMaxImageSize()
 
     raw_image = ""
     for i in range(adjusted_size):
@@ -74,15 +84,7 @@ class VerifiedBootVersion1HashtreeInfoGeneratorTest(ReleaseToolsTestCase):
     output_file = self._create_simg(raw_image)
 
     # Append the verity metadata.
-    prop_dict = {
+    verity_image_builder.Build(output_file)
-        'partition_size': str(partition_size),
-        'image_size': str(adjusted_size),
-        'verity_block_device': '/dev/block/system',
-        'verity_key': os.path.join(self.testdata_dir, 'testkey'),
-        'verity_signer_cmd': 'verity_signer',
-        'verity_size': str(verity_size),
-    }
-    MakeVerityEnabledImage(output_file, True, prop_dict)
 
     return output_file
 
@@ -163,23 +165,33 @@ class VerifiedBootVersion1HashtreeInfoGeneratorTest(ReleaseToolsTestCase):
     self.assertEqual(self.expected_root_hash, info.root_hash)
 
 
-class VerityUtilsTest(ReleaseToolsTestCase):
+class VerifiedBootVersion2VerityImageBuilderTest(ReleaseToolsTestCase):
 
   def setUp(self):
-    # To test AVBCalcMinPartitionSize(), by using 200MB to 2GB image size.
+    # To test CalculateMinPartitionSize(), by using 200MB to 2GB image size.
     #   -  51200 = 200MB * 1024 * 1024 / 4096
     #   - 524288 = 2GB * 1024 * 1024 * 1024 / 4096
     self._image_sizes = [BLOCK_SIZE * random.randint(51200, 524288) + offset
                          for offset in range(BLOCK_SIZE)]
 
-  def test_AVBCalcMinPartitionSize_LinearFooterSize(self):
+    prop_dict = {
+        'partition_size': None,
+        'partition_name': 'system',
+        'avb_avbtool': 'avbtool',
+        'avb_hashtree_enable': 'true',
+        'avb_add_hashtree_footer_args': None,
+    }
+    self.builder = CreateVerityImageBuilder(prop_dict)
+    self.assertEqual(2, self.builder.version)
+
+  def test_CalculateMinPartitionSize_LinearFooterSize(self):
     """Tests with footer size which is linear to partition size."""
     for image_size in self._image_sizes:
       for ratio in 0.95, 0.56, 0.22:
         expected_size = common.RoundUpTo4K(int(math.ceil(image_size / ratio)))
         self.assertEqual(
             expected_size,
-            AVBCalcMinPartitionSize(
+            self.builder.CalculateMinPartitionSize(
                 image_size, lambda x, ratio=ratio: int(x * ratio)))
 
   def test_AVBCalcMinPartitionSize_SlowerGrowthFooterSize(self):
@@ -191,7 +203,8 @@ class VerityUtilsTest(ReleaseToolsTestCase):
       return partition_size - int(math.pow(partition_size, 0.95))
 
     for image_size in self._image_sizes:
-      min_partition_size = AVBCalcMinPartitionSize(image_size, _SizeCalculator)
+      min_partition_size = self.builder.CalculateMinPartitionSize(
+          image_size, _SizeCalculator)
       # Checks min_partition_size can accommodate image_size.
       self.assertGreaterEqual(
           _SizeCalculator(min_partition_size),
@@ -201,7 +214,7 @@ class VerityUtilsTest(ReleaseToolsTestCase):
           _SizeCalculator(min_partition_size - BLOCK_SIZE),
           image_size)
 
-  def test_AVBCalcMinPartitionSize_FasterGrowthFooterSize(self):
+  def test_CalculateMinPartitionSize_FasterGrowthFooterSize(self):
     """Tests with footer size which grows faster than partition size."""
 
     def _SizeCalculator(partition_size):
@@ -211,7 +224,8 @@ class VerityUtilsTest(ReleaseToolsTestCase):
       return int(math.pow(partition_size, 0.95))
 
     for image_size in self._image_sizes:
-      min_partition_size = AVBCalcMinPartitionSize(image_size, _SizeCalculator)
+      min_partition_size = self.builder.CalculateMinPartitionSize(
+          image_size, _SizeCalculator)
       # Checks min_partition_size can accommodate image_size.
       self.assertGreaterEqual(
           _SizeCalculator(min_partition_size),

tools/releasetools/verity_utils.py

@@ -39,30 +39,30 @@ class BuildVerityImageError(Exception):
     Exception.__init__(self, message)
 
 
-def GetVerityFECSize(partition_size):
+def GetVerityFECSize(image_size):
-  cmd = ["fec", "-s", str(partition_size)]
+  cmd = ["fec", "-s", str(image_size)]
   output = common.RunAndCheckOutput(cmd, verbose=False)
   return int(output)
 
 
-def GetVerityTreeSize(partition_size):
+def GetVerityTreeSize(image_size):
-  cmd = ["build_verity_tree", "-s", str(partition_size)]
+  cmd = ["build_verity_tree", "-s", str(image_size)]
   output = common.RunAndCheckOutput(cmd, verbose=False)
   return int(output)
 
 
-def GetVerityMetadataSize(partition_size):
+def GetVerityMetadataSize(image_size):
-  cmd = ["build_verity_metadata.py", "size", str(partition_size)]
+  cmd = ["build_verity_metadata.py", "size", str(image_size)]
   output = common.RunAndCheckOutput(cmd, verbose=False)
   return int(output)
 
 
-def GetVeritySize(partition_size, fec_supported):
+def GetVeritySize(image_size, fec_supported):
-  verity_tree_size = GetVerityTreeSize(partition_size)
+  verity_tree_size = GetVerityTreeSize(image_size)
-  verity_metadata_size = GetVerityMetadataSize(partition_size)
+  verity_metadata_size = GetVerityMetadataSize(image_size)
   verity_size = verity_tree_size + verity_metadata_size
   if fec_supported:
-    fec_size = GetVerityFECSize(partition_size + verity_size)
+    fec_size = GetVerityFECSize(image_size + verity_size)
     return verity_size + fec_size
   return verity_size
 
@@ -79,54 +79,6 @@ def ZeroPadSimg(image_file, pad_size):
   simg.AppendFillChunk(0, blocks)
 
 
-def AdjustPartitionSizeForVerity(partition_size, fec_supported):
-  """Modifies the provided partition size to account for the verity metadata.
-
-  This information is used to size the created image appropriately.
-
-  Args:
-    partition_size: the size of the partition to be verified.
-
-  Returns:
-    A tuple of the size of the partition adjusted for verity metadata, and
-    the size of verity metadata.
-  """
-  key = "%d %d" % (partition_size, fec_supported)
-  if key in AdjustPartitionSizeForVerity.results:
-    return AdjustPartitionSizeForVerity.results[key]
-
-  hi = partition_size
-  if hi % BLOCK_SIZE != 0:
-    hi = (hi // BLOCK_SIZE) * BLOCK_SIZE
-
-  # verity tree and fec sizes depend on the partition size, which
-  # means this estimate is always going to be unnecessarily small
-  verity_size = GetVeritySize(hi, fec_supported)
-  lo = partition_size - verity_size
-  result = lo
-
-  # do a binary search for the optimal size
-  while lo < hi:
-    i = ((lo + hi) // (2 * BLOCK_SIZE)) * BLOCK_SIZE
-    v = GetVeritySize(i, fec_supported)
-    if i + v <= partition_size:
-      if result < i:
-        result = i
-        verity_size = v
-      lo = i + BLOCK_SIZE
-    else:
-      hi = i
-
-  logger.info(
-      "Adjusted partition size for verity, partition_size: %s, verity_size: %s",
-      result, verity_size)
-  AdjustPartitionSizeForVerity.results[key] = (result, verity_size)
-  return (result, verity_size)
-
-
-AdjustPartitionSizeForVerity.results = {}
-
-
 def BuildVerityFEC(sparse_image_path, verity_path, verity_fec_path,
                    padding_size):
   cmd = ["fec", "-e", "-p", str(padding_size), sparse_image_path,
@@ -187,103 +139,243 @@ def Append(target, file_to_append, error_message):
     raise BuildVerityImageError(error_message)
 
 
-def BuildVerifiedImage(data_image_path, verity_image_path,
+def CreateVerityImageBuilder(prop_dict):
-                       verity_metadata_path, verity_fec_path,
+  """Returns a verity image builder based on the given build properties.
-                       padding_size, fec_supported):
-  Append(
-      verity_image_path, verity_metadata_path,
-      "Could not append verity metadata!")
-
-  if fec_supported:
-    # Build FEC for the entire partition, including metadata.
-    BuildVerityFEC(
-        data_image_path, verity_image_path, verity_fec_path, padding_size)
-    Append(verity_image_path, verity_fec_path, "Could not append FEC!")
-
-  Append2Simg(
-      data_image_path, verity_image_path, "Could not append verity data!")
-
-
-def MakeVerityEnabledImage(out_file, fec_supported, prop_dict):
-  """Creates an image that is verifiable using dm-verity.
 
   Args:
-    out_file: the location to write the verifiable image at
+    prop_dict: A dict that contains the build properties. In particular, it will
-    prop_dict: a dictionary of properties required for image creation and
+        look for verity-related property values.
-               verification
 
-  Raises:
+  Returns:
-    AssertionError: On invalid partition sizes.
+    A VerityImageBuilder instance for Verified Boot 1.0 or Verified Boot 2.0; or
+        None if the given build doesn't support Verified Boot.
   """
-  # get properties
+  partition_size = prop_dict.get("partition_size")
-  image_size = int(prop_dict["image_size"])
+  # partition_size could be None at this point, if using dynamic partitions.
-  block_dev = prop_dict["verity_block_device"]
+  if partition_size:
-  signer_key = prop_dict["verity_key"] + ".pk8"
+    partition_size = int(partition_size)
+
+  # Verified Boot 1.0
+  verity_supported = prop_dict.get("verity") == "true"
+  is_verity_partition = "verity_block_device" in prop_dict
+  if verity_supported and is_verity_partition:
     if OPTIONS.verity_signer_path is not None:
       signer_path = OPTIONS.verity_signer_path
     else:
       signer_path = prop_dict["verity_signer_cmd"]
-  signer_args = OPTIONS.verity_signer_args
+    return Version1VerityImageBuilder(
+        partition_size,
+        prop_dict["verity_block_device"],
+        prop_dict.get("verity_fec") == "true",
+        signer_path,
+        prop_dict["verity_key"] + ".pk8",
+        OPTIONS.verity_signer_args,
+        "verity_disable" in prop_dict)
 
+  # Verified Boot 2.0
+  if (prop_dict.get("avb_hash_enable") == "true" or
+      prop_dict.get("avb_hashtree_enable") == "true"):
+    # key_path and algorithm are only available when chain partition is used.
+    key_path = prop_dict.get("avb_key_path")
+    algorithm = prop_dict.get("avb_algorithm")
+    if prop_dict.get("avb_hash_enable") == "true":
+      return VerifiedBootVersion2VerityImageBuilder(
+          prop_dict["partition_name"],
+          partition_size,
+          VerifiedBootVersion2VerityImageBuilder.AVB_HASH_FOOTER,
+          prop_dict["avb_avbtool"],
+          key_path,
+          algorithm,
+          prop_dict.get("avb_salt"),
+          prop_dict["avb_add_hash_footer_args"])
+    else:
+      return VerifiedBootVersion2VerityImageBuilder(
+          prop_dict["partition_name"],
+          partition_size,
+          VerifiedBootVersion2VerityImageBuilder.AVB_HASHTREE_FOOTER,
+          prop_dict["avb_avbtool"],
+          key_path,
+          algorithm,
+          prop_dict.get("avb_salt"),
+          prop_dict["avb_add_hashtree_footer_args"])
+
+  return None
+
+
+class VerityImageBuilder(object):
+  """A builder that generates an image with verity metadata for Verified Boot.
+
+  A VerityImageBuilder instance handles the works for building an image with
+  verity metadata for supporting Android Verified Boot. This class defines the
+  common interface between Verified Boot 1.0 and Verified Boot 2.0. A matching
+  builder will be returned based on the given build properties.
+
+  More info on the verity image generation can be found at the following link.
+  https://source.android.com/security/verifiedboot/dm-verity#implementation
+  """
+
+  def CalculateMaxImageSize(self, partition_size):
+    """Calculates the filesystem image size for the given partition size."""
+    raise NotImplementedError
+
+  def CalculateDynamicPartitionSize(self, image_size):
+    """Calculates and sets the partition size for a dynamic partition."""
+    raise NotImplementedError
+
+  def PadSparseImage(self, out_file):
+    """Adds padding to the generated sparse image."""
+    raise NotImplementedError
+
+  def Build(self, out_file):
+    """Builds the verity image and writes it to the given file."""
+    raise NotImplementedError
+
+
+class Version1VerityImageBuilder(VerityImageBuilder):
+  """A VerityImageBuilder for Verified Boot 1.0."""
+
+  def __init__(self, partition_size, block_dev, fec_supported, signer_path,
+               signer_key, signer_args, verity_disable):
+    self.version = 1
+    self.partition_size = partition_size
+    self.block_device = block_dev
+    self.fec_supported = fec_supported
+    self.signer_path = signer_path
+    self.signer_key = signer_key
+    self.signer_args = signer_args
+    self.verity_disable = verity_disable
+    self.image_size = None
+    self.verity_size = None
+
+  def CalculateDynamicPartitionSize(self, image_size):
+    # This needs to be implemented. Note that returning the given image size as
+    # the partition size doesn't make sense, as it will fail later.
+    raise NotImplementedError
+
+  def CalculateMaxImageSize(self, partition_size=None):
+    """Calculates the max image size by accounting for the verity metadata.
+
+    Args:
+      partition_size: The partition size, which defaults to self.partition_size
+          if unspecified.
+
+    Returns:
+      The size of the image adjusted for verity metadata.
+    """
+    if partition_size is None:
+      partition_size = self.partition_size
+    assert partition_size > 0, \
+        "Invalid partition size: {}".format(partition_size)
+
+    hi = partition_size
+    if hi % BLOCK_SIZE != 0:
+      hi = (hi // BLOCK_SIZE) * BLOCK_SIZE
+
+    # verity tree and fec sizes depend on the partition size, which
+    # means this estimate is always going to be unnecessarily small
+    verity_size = GetVeritySize(hi, self.fec_supported)
+    lo = partition_size - verity_size
+    result = lo
+
+    # do a binary search for the optimal size
+    while lo < hi:
+      i = ((lo + hi) // (2 * BLOCK_SIZE)) * BLOCK_SIZE
+      v = GetVeritySize(i, self.fec_supported)
+      if i + v <= partition_size:
+        if result < i:
+          result = i
+          verity_size = v
+        lo = i + BLOCK_SIZE
+      else:
+        hi = i
+
+    self.image_size = result
+    self.verity_size = verity_size
+
+    logger.info(
+        "Calculated image size for verity: partition_size %d, image_size %d, "
+        "verity_size %d", partition_size, result, verity_size)
+    return result
+
+  def Build(self, out_file):
+    """Creates an image that is verifiable using dm-verity.
+
+    Args:
+      out_file: the location to write the verifiable image at
+
+    Returns:
+      AssertionError: On invalid partition sizes.
+      BuildVerityImageError: On other errors.
+    """
+    image_size = int(self.image_size)
     tempdir_name = common.MakeTempDir(suffix="_verity_images")
 
     # Get partial image paths.
     verity_image_path = os.path.join(tempdir_name, "verity.img")
     verity_metadata_path = os.path.join(tempdir_name, "verity_metadata.img")
-  verity_fec_path = os.path.join(tempdir_name, "verity_fec.img")
 
     # Build the verity tree and get the root hash and salt.
     root_hash, salt = BuildVerityTree(out_file, verity_image_path)
 
     # Build the metadata blocks.
-  verity_disable = "verity_disable" in prop_dict
     BuildVerityMetadata(
-      image_size, verity_metadata_path, root_hash, salt, block_dev, signer_path,
+        image_size, verity_metadata_path, root_hash, salt, self.block_device,
-      signer_key, signer_args, verity_disable)
+        self.signer_path, self.signer_key, self.signer_args,
+        self.verity_disable)
 
-  # Build the full verified image.
+    padding_size = self.partition_size - self.image_size - self.verity_size
-  partition_size = int(prop_dict["partition_size"])
-  verity_size = int(prop_dict["verity_size"])
-
-  padding_size = partition_size - image_size - verity_size
     assert padding_size >= 0
 
-  BuildVerifiedImage(
+    # Build the full verified image.
-      out_file, verity_image_path, verity_metadata_path, verity_fec_path,
+    Append(
-      padding_size, fec_supported)
+        verity_image_path, verity_metadata_path,
+        "Failed to append verity metadata")
 
+    if self.fec_supported:
+      # Build FEC for the entire partition, including metadata.
+      verity_fec_path = os.path.join(tempdir_name, "verity_fec.img")
+      BuildVerityFEC(
+          out_file, verity_image_path, verity_fec_path, padding_size)
+      Append(verity_image_path, verity_fec_path, "Failed to append FEC")
 
-def AVBCalcMaxImageSize(avbtool, footer_type, partition_size, additional_args):
+    Append2Simg(
-  """Calculates max image size for a given partition size.
+        out_file, verity_image_path, "Failed to append verity data")
 
-  Args:
+  def PadSparseImage(self, out_file):
-    avbtool: String with path to avbtool.
+    sparse_image_size = GetSimgSize(out_file)
-    footer_type: 'hash' or 'hashtree' for generating footer.
+    if sparse_image_size > self.image_size:
-    partition_size: The size of the partition in question.
-    additional_args: Additional arguments to pass to "avbtool add_hash_footer"
-        or "avbtool add_hashtree_footer".
-
-  Returns:
-    The maximum image size.
-
-  Raises:
-    BuildVerityImageError: On invalid image size.
-  """
-  cmd = [avbtool, "add_%s_footer" % footer_type,
-         "--partition_size", str(partition_size), "--calc_max_image_size"]
-  cmd.extend(shlex.split(additional_args))
-
-  output = common.RunAndCheckOutput(cmd)
-  image_size = int(output)
-  if image_size <= 0:
       raise BuildVerityImageError(
-        "Invalid max image size: {}".format(output))
+          "Error: image size of {} is larger than partition size of "
-  return image_size
+          "{}".format(sparse_image_size, self.image_size))
+    ZeroPadSimg(out_file, self.image_size - sparse_image_size)
 
 
-def AVBCalcMinPartitionSize(image_size, size_calculator):
+class VerifiedBootVersion2VerityImageBuilder(VerityImageBuilder):
+  """A VerityImageBuilder for Verified Boot 2.0."""
+
+  AVB_HASH_FOOTER = 1
+  AVB_HASHTREE_FOOTER = 2
+
+  def __init__(self, partition_name, partition_size, footer_type, avbtool,
+               key_path, algorithm, salt, signing_args):
+    self.version = 2
+    self.partition_name = partition_name
+    self.partition_size = partition_size
+    self.footer_type = footer_type
+    self.avbtool = avbtool
+    self.algorithm = algorithm
+    self.key_path = key_path
+    self.salt = salt
+    self.signing_args = signing_args
+    self.image_size = None
+
+  def CalculateMinPartitionSize(self, image_size, size_calculator=None):
     """Calculates min partition size for a given image size.
 
+    This is used when determining the partition size for a dynamic partition,
+    which should be cover the given image size (for filesystem files) as well as
+    the verity metadata size.
+
     Args:
       image_size: The size of the image in question.
       size_calculator: The function to calculate max image size
@@ -292,6 +384,9 @@ def AVBCalcMinPartitionSize(image_size, size_calculator):
     Returns:
       The minimum partition size required to accommodate the image size.
     """
+    if size_calculator is None:
+      size_calculator = self.CalculateMaxImageSize
+
     # Use image size as partition size to approximate final partition size.
     image_ratio = size_calculator(image_size) / float(image_size)
 
@@ -332,42 +427,77 @@ def AVBCalcMinPartitionSize(image_size, size_calculator):
         lo = mid + BLOCK_SIZE
 
     logger.info(
-      "AVBCalcMinPartitionSize(%d): partition_size: %d.",
+        "CalculateMinPartitionSize(%d): partition_size %d.", image_size,
-      image_size, partition_size)
+        partition_size)
 
     return partition_size
 
+  def CalculateDynamicPartitionSize(self, image_size):
+    self.partition_size = self.CalculateMinPartitionSize(image_size)
+    return self.partition_size
 
-def AVBAddFooter(image_path, avbtool, footer_type, partition_size,
+  def CalculateMaxImageSize(self, partition_size=None):
-                 partition_name, key_path, algorithm, salt,
+    """Calculates max image size for a given partition size.
-                 additional_args):
+
+    Args:
+      partition_size: The partition size, which defaults to self.partition_size
+          if unspecified.
+
+    Returns:
+      The maximum image size.
+
+    Raises:
+      BuildVerityImageError: On error or getting invalid image size.
+    """
+    if partition_size is None:
+      partition_size = self.partition_size
+    assert partition_size > 0, \
+        "Invalid partition size: {}".format(partition_size)
+
+    add_footer = ("add_hash_footer" if self.footer_type == self.AVB_HASH_FOOTER
+                  else "add_hashtree_footer")
+    cmd = [self.avbtool, add_footer, "--partition_size",
+           str(partition_size), "--calc_max_image_size"]
+    cmd.extend(shlex.split(self.signing_args))
+
+    proc = common.Run(cmd)
+    output, _ = proc.communicate()
+    if proc.returncode != 0:
+      raise BuildVerityImageError(
+          "Failed to calculate max image size:\n{}".format(output))
+    image_size = int(output)
+    if image_size <= 0:
+      raise BuildVerityImageError(
+          "Invalid max image size: {}".format(output))
+    self.image_size = image_size
+    return image_size
+
+  def PadSparseImage(self, out_file):
+    # No-op as the padding is taken care of by avbtool.
+    pass
+
+  def Build(self, out_file):
     """Adds dm-verity hashtree and AVB metadata to an image.
 
     Args:
-    image_path: Path to image to modify.
+      out_file: Path to image to modify.
-    avbtool: String with path to avbtool.
-    footer_type: 'hash' or 'hashtree' for generating footer.
-    partition_size: The size of the partition in question.
-    partition_name: The name of the partition - will be embedded in metadata.
-    key_path: Path to key to use or None.
-    algorithm: Name of algorithm to use or None.
-    salt: The salt to use (a hexadecimal string) or None.
-    additional_args: Additional arguments to pass to "avbtool add_hash_footer"
-        or "avbtool add_hashtree_footer".
     """
-  cmd = [avbtool, "add_%s_footer" % footer_type,
+    add_footer = ("add_hash_footer" if self.footer_type == self.AVB_HASH_FOOTER
-         "--partition_size", partition_size,
+                  else "add_hashtree_footer")
-         "--partition_name", partition_name,
+    cmd = [self.avbtool, add_footer,
-         "--image", image_path]
+           "--partition_size", str(self.partition_size),
+           "--partition_name", self.partition_name,
+           "--image", out_file]
+    if self.key_path and self.algorithm:
+      cmd.extend(["--key", self.key_path, "--algorithm", self.algorithm])
+    if self.salt:
+      cmd.extend(["--salt", self.salt])
+    cmd.extend(shlex.split(self.signing_args))
 
-  if key_path and algorithm:
+    proc = common.Run(cmd)
-    cmd.extend(["--key", key_path, "--algorithm", algorithm])
+    output, _ = proc.communicate()
-  if salt:
+    if proc.returncode != 0:
-    cmd.extend(["--salt", salt])
+      raise BuildVerityImageError("Failed to add AVB footer: {}".format(output))
-
-  cmd.extend(shlex.split(additional_args))
-
-  common.RunAndCheckOutput(cmd)
 
 
 class HashtreeInfoGenerationError(Exception):
@@ -431,6 +561,20 @@ class VerifiedBootVersion1HashtreeInfoGenerator(HashtreeInfoGenerator):
     self.hashtree_size = None
     self.metadata_size = None
 
+    prop_dict = {
+        'partition_size': str(partition_size),
+        'verity': 'true',
+        'verity_fec': 'true' if fec_supported else None,
+        # 'verity_block_device' needs to be present to indicate a verity-enabled
+        # partition.
+        'verity_block_device': '',
+        # We don't need the following properties that are needed for signing the
+        # verity metadata.
+        'verity_key': '',
+        'verity_signer_cmd': None,
+    }
+    self.verity_image_builder = CreateVerityImageBuilder(prop_dict)
+
     self.hashtree_info = HashtreeInfo()
 
   def DecomposeSparseImage(self, image):
@@ -447,8 +591,7 @@ class VerifiedBootVersion1HashtreeInfoGenerator(HashtreeInfoGenerator):
         "partition size {} doesn't match with the calculated image size." \
         " total_blocks: {}".format(self.partition_size, image.total_blocks)
 
-    adjusted_size, _ = AdjustPartitionSizeForVerity(
+    adjusted_size = self.verity_image_builder.CalculateMaxImageSize()
-        self.partition_size, self.fec_supported)
     assert adjusted_size % self.block_size == 0
 
     verity_tree_size = GetVerityTreeSize(adjusted_size)
@@ -504,7 +647,7 @@ class VerifiedBootVersion1HashtreeInfoGenerator(HashtreeInfoGenerator):
   def ValidateHashtree(self):
     """Checks that we can reconstruct the verity hash tree."""
 
-    # Writes the file system section to a temp file; and calls the executable
+    # Writes the filesystem section to a temp file; and calls the executable
     # build_verity_tree to construct the hash tree.
     adjusted_partition = common.MakeTempFile(prefix="adjusted_partition")
     with open(adjusted_partition, "wb") as fd: