diff --git a/core/Makefile b/core/Makefile
index 6926b26..35d744a 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -2830,6 +2830,41 @@
 endef
 
 # -----------------------------------------------------------------
+# custom images
+INSTALLED_CUSTOMIMAGES_TARGET :=
+
+ifneq ($(strip $(BOARD_CUSTOMIMAGES_PARTITION_LIST)),)
+INTERNAL_AVB_CUSTOMIMAGES_SIGNING_ARGS :=
+
+# Sign custom image.
+# $(1): the prebuilt custom image.
+# $(2): the mount point of the prebuilt custom image.
+# $(3): the signed custom image target.
+define sign_custom_image
+$(3): $(1) $(INTERNAL_USERIMAGES_DEPS)
+	@echo Target custom image: $(3)
+	mkdir -p $(dir $(3))
+	cp $(1) $(3)
+ifeq ($(BOARD_AVB_ENABLE),true)
+	PATH=$(INTERNAL_USERIMAGES_BINARY_PATHS):$$$$PATH \
+          $(AVBTOOL) add_hashtree_footer \
+          --image $(3) \
+          --key $(BOARD_AVB_$(call to-upper,$(2))_KEY_PATH) \
+          --algorithm $(BOARD_AVB_$(call to-upper,$(2))_ALGORITHM) \
+          --partition_size $(BOARD_AVB_$(call to-upper,$(2))_PARTITION_SIZE) \
+          --partition_name $(2) \
+          $(INTERNAL_AVB_CUSTOMIMAGES_SIGNING_ARGS) \
+          $(BOARD_AVB_$(call to-upper,$(2))_ADD_HASHTREE_FOOTER_ARGS)
+endif
+INSTALLED_CUSTOMIMAGES_TARGET += $(3)
+endef
+
+$(foreach partition,$(BOARD_CUSTOMIMAGES_PARTITION_LIST), \
+  $(foreach image,$(BOARD_AVB_$(call to-upper,$(partition))_IMAGE_LIST), \
+     $(eval $(call sign_custom_image,$(image),$(partition),$(PRODUCT_OUT)/$(notdir $(image))))))
+endif
+
+# -----------------------------------------------------------------
 # vbmeta image
 ifeq ($(BOARD_AVB_ENABLE),true)
 
@@ -3000,6 +3035,18 @@
             --include_descriptors_from_image $(call images-for-partitions,$(1)))))
 endef
 
+# Checks and sets build variables for a custom chained partition to include it into vbmeta.img.
+# $(1): the custom partition to enable AVB chain.
+define check-and-set-custom-avb-chain-args
+$(eval part := $(1))
+$(eval PART=$(call to-upper,$(part)))
+$(eval _rollback_index_location := BOARD_AVB_$(PART)_ROLLBACK_INDEX_LOCATION)
+$(if $($(_rollback_index_location)),,$(error $(_rollback_index_location) is not defined))
+
+INTERNAL_AVB_MAKE_VBMETA_IMAGE_ARGS += \
+    --chain_partition $(part):$($(_rollback_index_location)):$(AVB_CHAIN_KEY_DIR)/$(part).avbpubkey
+endef
+
 ifdef INSTALLED_BOOTIMAGE_TARGET
 $(eval $(call check-and-set-avb-args,boot))
 endif
@@ -3043,6 +3090,11 @@
 $(eval $(call check-and-set-avb-args,vbmeta_vendor))
 endif
 
+ifneq ($(strip $(BOARD_CUSTOMIMAGES_PARTITION_LIST)),)
+$(foreach partition,$(BOARD_CUSTOMIMAGES_PARTITION_LIST), \
+    $(eval $(call check-and-set-custom-avb-chain-args,$(partition))))
+endif
+
 # Add kernel cmdline descriptor for kernel to mount system.img as root with
 # dm-verity. This works when system.img is either chained or not-chained:
 # - chained: The --setup_as_rootfs_from_kernel option will add dm-verity kernel
@@ -3113,6 +3165,10 @@
   $(if $(BOARD_AVB_VBMETA_VENDOR_KEY_PATH),\
     $(hide) $(AVBTOOL) extract_public_key --key $(BOARD_AVB_VBMETA_VENDOR_KEY_PATH) \
         --output $(1)/vbmeta_vendor.avbpubkey)
+  $(if $(BOARD_CUSTOMIMAGES_PARTITION_LIST),\
+    $(hide) $(foreach partition,$(BOARD_CUSTOMIMAGES_PARTITION_LIST), \
+        $(AVBTOOL) extract_public_key --key $(BOARD_AVB_$(call to-upper,$(partition))_KEY_PATH) \
+            --output $(1)/$(partition).avbpubkey;))
 endef
 
 # Builds a chained VBMeta image. This VBMeta image will contain the descriptors for the partitions
@@ -3180,6 +3236,7 @@
 	    $(INSTALLED_SYSTEM_EXTIMAGE_TARGET) \
 	    $(INSTALLED_ODMIMAGE_TARGET) \
 	    $(INSTALLED_DTBOIMAGE_TARGET) \
+	    $(INSTALLED_CUSTOMIMAGES_TARGET) \
 	    $(INSTALLED_RECOVERYIMAGE_TARGET) \
 	    $(INSTALLED_VBMETA_SYSTEMIMAGE_TARGET) \
 	    $(INSTALLED_VBMETA_VENDORIMAGE_TARGET) \
@@ -3739,6 +3796,16 @@
 	$(hide) echo "avb_recovery_algorithm=$(BOARD_AVB_RECOVERY_ALGORITHM)" >> $@
 	$(hide) echo "avb_recovery_rollback_index_location=$(BOARD_AVB_RECOVERY_ROLLBACK_INDEX_LOCATION)" >> $@
 endif # BOARD_AVB_RECOVERY_KEY_PATH
+ifneq (,$(strip $(BOARD_CUSTOMIMAGES_PARTITION_LIST)))
+	$(hide) echo "avb_custom_images_partition_list=$(BOARD_CUSTOMIMAGES_PARTITION_LIST)" >> $@
+	$(hide) $(foreach partition,$(BOARD_CUSTOMIMAGES_PARTITION_LIST), \
+	    echo "avb_$(partition)_key_path=$(BOARD_AVB_$(call to-upper,$(partition))_KEY_PATH)"  >> $@; \
+	    echo "avb_$(partition)_algorithm=$(BOARD_AVB_$(call to-upper,$(partition))_ALGORITHM)"  >> $@; \
+	    echo "avb_$(partition)_add_hashtree_footer_args=$(BOARD_AVB_$(call to-upper,$(partition))_ADD_HASHTREE_FOOTER_ARGS)"  >> $@; \
+	    echo "avb_$(partition)_rollback_index_location=$(BOARD_AVB_$(call to-upper,$(partition))_ROLLBACK_INDEX_LOCATION)"  >> $@; \
+	    echo "avb_$(partition)_partition_size=$(BOARD_AVB_$(call to-upper,$(partition))_PARTITION_SIZE)"  >> $@; \
+	    echo "avb_$(partition)_image_list=$(foreach image,$(BOARD_AVB_$(call to-upper,$(partition))_IMAGE_LIST),$(notdir $(image)))" >> $@;)
+endif # BOARD_CUSTOMIMAGES_PARTITION_LIST
 ifneq (,$(strip $(BOARD_AVB_VBMETA_SYSTEM)))
 	$(hide) echo "avb_vbmeta_system=$(BOARD_AVB_VBMETA_SYSTEM)" >> $@
 	$(hide) echo "avb_vbmeta_system_args=$(BOARD_AVB_MAKE_VBMETA_SYSTEM_IMAGE_ARGS)" >> $@
@@ -3972,6 +4039,7 @@
 	    $(INSTALLED_VBMETAIMAGE_TARGET) \
 	    $(INSTALLED_ODMIMAGE_TARGET) \
 	    $(INSTALLED_DTBOIMAGE_TARGET) \
+	    $(INSTALLED_CUSTOMIMAGES_TARGET) \
 	    $(INTERNAL_SYSTEMOTHERIMAGE_FILES) \
 	    $(INSTALLED_ANDROID_INFO_TXT_TARGET) \
 	    $(INSTALLED_KERNEL_TARGET) \
@@ -4216,6 +4284,11 @@
 	$(hide) mkdir -p $(zip_root)/PREBUILT_IMAGES
 	$(hide) cp $(INSTALLED_DTBOIMAGE_TARGET) $(zip_root)/PREBUILT_IMAGES/
 endif # BOARD_PREBUILT_DTBOIMAGE
+ifneq ($(strip $(BOARD_CUSTOMIMAGES_PARTITION_LIST)),)
+	$(hide) mkdir -p $(zip_root)/PREBUILT_IMAGES
+	$(hide) $(foreach partition,$(BOARD_CUSTOMIMAGES_PARTITION_LIST), \
+	    $(foreach image,$(BOARD_AVB_$(call to-upper,$(partition))_IMAGE_LIST),cp $(image) $(zip_root)/PREBUILT_IMAGES/;))
+endif # BOARD_CUSTOMIMAGES_PARTITION_LIST
 	@# The radio images in BOARD_PACK_RADIOIMAGES will be additionally copied from RADIO/ into
 	@# IMAGES/, which then will be added into <product>-img.zip. Such images must be listed in
 	@# INSTALLED_RADIOIMAGE_TARGET.
diff --git a/tools/releasetools/add_img_to_target_files.py b/tools/releasetools/add_img_to_target_files.py
index 70ea967..490b44a 100755
--- a/tools/releasetools/add_img_to_target_files.py
+++ b/tools/releasetools/add_img_to_target_files.py
@@ -60,6 +60,7 @@
 import common
 import rangelib
 import sparse_img
+import verity_utils
 
 if sys.hexversion < 0x02070000:
   print("Python 2.7 or newer is required.", file=sys.stderr)
@@ -312,6 +313,56 @@
   img.Write()
   return img.name
 
+def AddCustomImages(output_zip, partition_name):
+  """Adds and signs custom images in IMAGES/.
+
+  Args:
+    output_zip: The output zip file (needs to be already open), or None to
+        write images to OPTIONS.input_tmp/.
+
+  Uses the image under IMAGES/ if it already exists. Otherwise looks for the
+  image under PREBUILT_IMAGES/, signs it as needed, and returns the image name.
+
+  Raises:
+    AssertionError: If image can't be found.
+  """
+
+  partition_size = OPTIONS.info_dict.get(
+      "avb_{}_partition_size".format(partition_name))
+  key_path = OPTIONS.info_dict.get("avb_{}_key_path".format(partition_name))
+  algorithm = OPTIONS.info_dict.get("avb_{}_algorithm".format(partition_name))
+  extra_args = OPTIONS.info_dict.get(
+      "avb_{}_add_hashtree_footer_args".format(partition_name))
+  partition_size = OPTIONS.info_dict.get(
+      "avb_{}_partition_size".format(partition_name))
+
+  builder = verity_utils.CreateCustomImageBuilder(
+      OPTIONS.info_dict, partition_name, partition_size,
+      key_path, algorithm, extra_args)
+
+  for img_name in OPTIONS.info_dict.get(
+      "avb_{}_image_list".format(partition_name)).split():
+    custom_image = OutputFile(output_zip, OPTIONS.input_tmp, "IMAGES", img_name)
+    if os.path.exists(custom_image.name):
+      continue
+
+    custom_image_prebuilt_path = os.path.join(
+        OPTIONS.input_tmp, "PREBUILT_IMAGES", img_name)
+    assert os.path.exists(custom_image_prebuilt_path), \
+      "Failed to find %s at %s" % (img_name, custom_image_prebuilt_path)
+
+    shutil.copy(custom_image_prebuilt_path, custom_image.name)
+
+    if builder is not None:
+      builder.Build(custom_image.name)
+
+    custom_image.Write()
+
+  default = os.path.join(OPTIONS.input_tmp, "IMAGES", partition_name + ".img")
+  assert os.path.exists(default), \
+      "There should be one %s.img" % (partition_name)
+  return default
+
 
 def CreateImage(input_dir, info_dict, what, output_file, block_list=None):
   logger.info("creating %s.img...", what)
@@ -411,8 +462,9 @@
   Args:
     output_zip: The output zip file, which needs to be already open.
     partitions: A dict that's keyed by partition names with image paths as
-        values. Only valid partition names are accepted, as listed in
-        common.AVB_PARTITIONS.
+        values. Only valid partition names are accepted, as partitions listed
+        in common.AVB_PARTITIONS and custom partitions listed in
+        OPTIONS.info_dict.get("avb_custom_images_partition_list")
     name: Name of the VBMeta partition, e.g. 'vbmeta', 'vbmeta_system'.
     needed_partitions: Partitions whose descriptors should be included into the
         generated VBMeta image.
@@ -831,11 +883,20 @@
     banner("dtbo")
     partitions['dtbo'] = AddDtbo(output_zip)
 
+  # Custom images.
+  custom_partitions = OPTIONS.info_dict.get(
+      "avb_custom_images_partition_list", "").strip().split()
+  for partition_name in custom_partitions:
+    partition_name = partition_name.strip()
+    banner("custom images for " + partition_name)
+    partitions[partition_name] = AddCustomImages(output_zip, partition_name)
+
   if OPTIONS.info_dict.get("avb_enable") == "true":
     # vbmeta_partitions includes the partitions that should be included into
     # top-level vbmeta.img, which are the ones that are not included in any
     # chained VBMeta image plus the chained VBMeta images themselves.
-    vbmeta_partitions = common.AVB_PARTITIONS[:]
+    # Currently custom_partitions are all chained to VBMeta image.
+    vbmeta_partitions = common.AVB_PARTITIONS[:] + tuple(custom_partitions)
 
     vbmeta_system = OPTIONS.info_dict.get("avb_vbmeta_system", "").strip()
     if vbmeta_system:
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 96f93a8..93e14e5 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -1132,8 +1132,9 @@
   Args:
     image_path: The output path for the new VBMeta image.
     partitions: A dict that's keyed by partition names with image paths as
-        values. Only valid partition names are accepted, as listed in
-        common.AVB_PARTITIONS.
+        values. Only valid partition names are accepted, as partitions listed
+        in common.AVB_PARTITIONS and custom partitions listed in
+        OPTIONS.info_dict.get("avb_custom_images_partition_list")
     name: Name of the VBMeta partition, e.g. 'vbmeta', 'vbmeta_system'.
     needed_partitions: Partitions whose descriptors should be included into the
         generated VBMeta image.
@@ -1145,11 +1146,15 @@
   cmd = [avbtool, "make_vbmeta_image", "--output", image_path]
   AppendAVBSigningArgs(cmd, name)
 
+  custom_partitions = OPTIONS.info_dict.get(
+      "avb_custom_images_partition_list", "").strip().split()
+
   for partition, path in partitions.items():
     if partition not in needed_partitions:
       continue
     assert (partition in AVB_PARTITIONS or
-            partition in AVB_VBMETA_PARTITIONS), \
+            partition in AVB_VBMETA_PARTITIONS or
+            partition in custom_partitions), \
         'Unknown partition: {}'.format(partition)
     assert os.path.exists(path), \
         'Failed to find {} for {}'.format(path, partition)
diff --git a/tools/releasetools/ota_from_target_files.py b/tools/releasetools/ota_from_target_files.py
index 16b278a..b753414 100755
--- a/tools/releasetools/ota_from_target_files.py
+++ b/tools/releasetools/ota_from_target_files.py
@@ -189,6 +189,13 @@
   --payload_signer_key_size <key_size>
       Deprecated. Use the '--payload_signer_maximum_signature_size' instead.
 
+  --boot_variable_file <path>
+      A file that contains the possible values of ro.boot.* properties. It's
+      used to calculate the possible runtime fingerprints when some
+      ro.product.* properties are overridden by the 'import' statement.
+      The file expects one property per line, and each line has the following
+      format: 'prop_name=value1,value2'. e.g. 'ro.boot.product.sku=std,pro'
+
   --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
@@ -257,8 +264,8 @@
 OPTIONS.skip_compatibility_check = False
 OPTIONS.output_metadata_path = None
 OPTIONS.disable_fec_computation = False
-OPTIONS.boot_variable_values = None
 OPTIONS.force_non_ab = False
+OPTIONS.boot_variable_file = None
 
 
 METADATA_NAME = 'META-INF/com/android/metadata'
@@ -931,13 +938,23 @@
   assert isinstance(target_info, common.BuildInfo)
   assert source_info is None or isinstance(source_info, common.BuildInfo)
 
+  separator = '|'
+
+  boot_variable_values = {}
+  if OPTIONS.boot_variable_file:
+    d = common.LoadDictionaryFromFile(OPTIONS.boot_variable_file)
+    for key, values in d.items():
+      boot_variable_values[key] = [val.strip() for val in values.split(',')]
+
+  post_build_devices, post_build_fingerprints = \
+      CalculateRuntimeDevicesAndFingerprints(target_info, boot_variable_values)
   metadata = {
-      'post-build' : target_info.fingerprint,
-      'post-build-incremental' : target_info.GetBuildProp(
+      'post-build': separator.join(sorted(post_build_fingerprints)),
+      'post-build-incremental': target_info.GetBuildProp(
           'ro.build.version.incremental'),
-      'post-sdk-level' : target_info.GetBuildProp(
+      'post-sdk-level': target_info.GetBuildProp(
           'ro.build.version.sdk'),
-      'post-security-patch-level' : target_info.GetBuildProp(
+      'post-security-patch-level': target_info.GetBuildProp(
           'ro.build.version.security_patch'),
   }
 
@@ -955,12 +972,15 @@
 
   is_incremental = source_info is not None
   if is_incremental:
-    metadata['pre-build'] = source_info.fingerprint
+    pre_build_devices, pre_build_fingerprints = \
+        CalculateRuntimeDevicesAndFingerprints(source_info,
+                                               boot_variable_values)
+    metadata['pre-build'] = separator.join(sorted(pre_build_fingerprints))
     metadata['pre-build-incremental'] = source_info.GetBuildProp(
         'ro.build.version.incremental')
-    metadata['pre-device'] = source_info.device
+    metadata['pre-device'] = separator.join(sorted(pre_build_devices))
   else:
-    metadata['pre-device'] = target_info.device
+    metadata['pre-device'] = separator.join(sorted(post_build_devices))
 
   # Use the actual post-timestamp, even for a downgrade case.
   metadata['post-timestamp'] = target_info.GetBuildProp('ro.build.date.utc')
@@ -1972,24 +1992,24 @@
           output_file)
 
 
-def CalculateRuntimeFingerprints():
-  """Returns a set of runtime fingerprints based on the boot variables."""
+def CalculateRuntimeDevicesAndFingerprints(build_info, boot_variable_values):
+  """Returns a tuple of sets for runtime devices and fingerprints"""
 
-  build_info = common.BuildInfo(OPTIONS.info_dict, OPTIONS.oem_dicts)
+  device_names = {build_info.device}
   fingerprints = {build_info.fingerprint}
 
-  if not OPTIONS.boot_variable_values:
-    return fingerprints
+  if not boot_variable_values:
+    return device_names, fingerprints
 
   # Calculate all possible combinations of the values for the boot variables.
-  keys = OPTIONS.boot_variable_values.keys()
-  value_list = OPTIONS.boot_variable_values.values()
+  keys = boot_variable_values.keys()
+  value_list = boot_variable_values.values()
   combinations = [dict(zip(keys, values))
                   for values in itertools.product(*value_list)]
   for placeholder_values in combinations:
     # Reload the info_dict as some build properties may change their values
     # based on the value of ro.boot* properties.
-    info_dict = copy.deepcopy(OPTIONS.info_dict)
+    info_dict = copy.deepcopy(build_info.info_dict)
     for partition in common.PARTITIONS_WITH_CARE_MAP:
       partition_prop_key = "{}.build.prop".format(partition)
       old_props = info_dict[partition_prop_key]
@@ -1997,9 +2017,10 @@
           old_props.input_file, partition, placeholder_values)
     info_dict["build.prop"] = info_dict["system.build.prop"]
 
-    build_info = common.BuildInfo(info_dict, OPTIONS.oem_dicts)
-    fingerprints.add(build_info.fingerprint)
-  return fingerprints
+    new_build_info = common.BuildInfo(info_dict, build_info.oem_dicts)
+    device_names.add(new_build_info.device)
+    fingerprints.add(new_build_info.fingerprint)
+  return device_names, fingerprints
 
 
 def main(argv):
@@ -2077,6 +2098,8 @@
       OPTIONS.disable_fec_computation = True
     elif o == "--force_non_ab":
       OPTIONS.force_non_ab = True
+    elif o == "--boot_variable_file":
+      OPTIONS.boot_variable_file = a
     else:
       return False
     return True
@@ -2114,6 +2137,7 @@
                                  "output_metadata_path=",
                                  "disable_fec_computation",
                                  "force_non_ab",
+                                 "boot_variable_file=",
                              ], extra_option_handler=option_handler)
 
   if len(args) != 2:
diff --git a/tools/releasetools/sign_target_files_apks.py b/tools/releasetools/sign_target_files_apks.py
index 52cd9a8..52b7889 100755
--- a/tools/releasetools/sign_target_files_apks.py
+++ b/tools/releasetools/sign_target_files_apks.py
@@ -112,6 +112,17 @@
       (e.g. "--signing_helper /path/to/helper"). The args will be appended to
       the existing ones in info dict.
 
+  --avb_extra_custom_image_key <partition=key>
+  --avb_extra_custom_image_algorithm <partition=algorithm>
+      Use the specified algorithm (e.g. SHA256_RSA4096) and the key to AVB-sign
+      the specified custom images mounted on the partition. Otherwise it uses
+      the existing values in info dict.
+
+  --avb_extra_custom_image_extra_args <partition=extra_args>
+      Specify any additional args that are needed to AVB-sign the custom images
+      mounted on the partition (e.g. "--signing_helper /path/to/helper"). The
+      args will be appended to the existing ones in info dict.
+
   --android_jar_path <path>
       Path to the android.jar to repack the apex file.
 """
@@ -956,12 +967,20 @@
     if extra_args:
       print('Setting extra AVB signing args for %s to "%s"' % (
           partition, extra_args))
-      args_key = AVB_FOOTER_ARGS_BY_PARTITION[partition]
+      if partition in AVB_FOOTER_ARGS_BY_PARTITION:
+        args_key = AVB_FOOTER_ARGS_BY_PARTITION[partition]
+      else:
+        # custom partition
+        args_key = "avb_{}_add_hashtree_footer_args".format(partition)
       misc_info[args_key] = (misc_info.get(args_key, '') + ' ' + extra_args)
 
   for partition in AVB_FOOTER_ARGS_BY_PARTITION:
     ReplaceAvbPartitionSigningKey(partition)
 
+  for custom_partition in misc_info.get(
+      "avb_custom_images_partition_list", "").strip().split():
+    ReplaceAvbPartitionSigningKey(custom_partition)
+
 
 def RewriteAvbProps(misc_info):
   """Rewrites the props in AVB signing args."""
@@ -1208,6 +1227,15 @@
       OPTIONS.avb_extra_args['vbmeta_vendor'] = a
     elif o == "--avb_apex_extra_args":
       OPTIONS.avb_extra_args['apex'] = a
+    elif o == "--avb_extra_custom_image_key":
+      partition, key = a.split("=")
+      OPTIONS.avb_keys[partition] = key
+    elif o == "--avb_extra_custom_image_algorithm":
+      partition, algorithm = a.split("=")
+      OPTIONS.avb_algorithms[partition] = algorithm
+    elif o == "--avb_extra_custom_image_extra_args":
+      partition, extra_args = a.split("=")
+      OPTIONS.avb_extra_args[partition] = extra_args
     else:
       return False
     return True
@@ -1252,6 +1280,9 @@
           "avb_vbmeta_vendor_algorithm=",
           "avb_vbmeta_vendor_key=",
           "avb_vbmeta_vendor_extra_args=",
+          "avb_extra_custom_image_key=",
+          "avb_extra_custom_image_algorithm=",
+          "avb_extra_custom_image_extra_args=",
       ],
       extra_option_handler=option_handler)
 
diff --git a/tools/releasetools/test_ota_from_target_files.py b/tools/releasetools/test_ota_from_target_files.py
index 4077d06..7783f96 100644
--- a/tools/releasetools/test_ota_from_target_files.py
+++ b/tools/releasetools/test_ota_from_target_files.py
@@ -27,7 +27,7 @@
     GetTargetFilesZipWithoutPostinstallConfig, NonAbOtaPropertyFiles,
     Payload, PayloadSigner, POSTINSTALL_CONFIG, PropertyFiles,
     StreamingPropertyFiles, WriteFingerprintAssertion,
-    CalculateRuntimeFingerprints)
+    CalculateRuntimeDevicesAndFingerprints)
 
 
 def construct_target_files(secondary=False):
@@ -1334,6 +1334,9 @@
       'ro.build.version.incremental=version-incremental',
       'ro.build.type=build-type',
       'ro.build.tags=build-tags',
+      'ro.build.version.sdk=30',
+      'ro.build.version.security_patch=2020',
+      'ro.build.date.utc=12345678'
   ]
 
   VENDOR_BUILD_PROP = [
@@ -1345,11 +1348,12 @@
   def setUp(self):
     common.OPTIONS.oem_dicts = None
     self.test_dir = common.MakeTempDir()
-    self.writeFiles({'META/misc_info.txt': '\n'.join(self.MISC_INFO)})
+    self.writeFiles({'META/misc_info.txt': '\n'.join(self.MISC_INFO)},
+                    self.test_dir)
 
-  def writeFiles(self, contents_dict):
+  def writeFiles(self, contents_dict, out_dir):
     for path, content in contents_dict.items():
-      abs_path = os.path.join(self.test_dir, path)
+      abs_path = os.path.join(out_dir, path)
       dir_name = os.path.dirname(abs_path)
       if not os.path.exists(dir_name):
         os.makedirs(dir_name)
@@ -1371,12 +1375,14 @@
     self.writeFiles({
         'SYSTEM/build.prop': '\n'.join(build_prop),
         'VENDOR/build.prop': '\n'.join(self.VENDOR_BUILD_PROP),
-    })
-    common.OPTIONS.info_dict = common.LoadInfoDict(self.test_dir)
+    }, self.test_dir)
 
-    self.assertEqual({
-        self.constructFingerprint('product-brand/product-name/product-device')
-    }, CalculateRuntimeFingerprints())
+    build_info = common.BuildInfo(common.LoadInfoDict(self.test_dir))
+    expected = ({'product-device'},
+                {self.constructFingerprint(
+                    'product-brand/product-name/product-device')})
+    self.assertEqual(expected,
+                     CalculateRuntimeDevicesAndFingerprints(build_info, {}))
 
   def test_CalculatePossibleFingerprints_single_override(self):
     vendor_build_prop = copy.deepcopy(self.VENDOR_BUILD_PROP)
@@ -1390,20 +1396,22 @@
         'ro.product.vendor.name=vendor-product-std',
         'VENDOR/etc/build_pro.prop':
         'ro.product.vendor.name=vendor-product-pro',
-    })
-    common.OPTIONS.info_dict = common.LoadInfoDict(self.test_dir)
-    common.OPTIONS.boot_variable_values = {
-        'ro.boot.sku_name': ['std', 'pro']
-    }
+    }, self.test_dir)
 
-    self.assertEqual({
+    build_info = common.BuildInfo(common.LoadInfoDict(self.test_dir))
+    boot_variable_values = {'ro.boot.sku_name': ['std', 'pro']}
+
+    expected = ({'vendor-product-device'}, {
         self.constructFingerprint(
             'vendor-product-brand/vendor-product-name/vendor-product-device'),
         self.constructFingerprint(
             'vendor-product-brand/vendor-product-std/vendor-product-device'),
         self.constructFingerprint(
             'vendor-product-brand/vendor-product-pro/vendor-product-device'),
-    }, CalculateRuntimeFingerprints())
+    })
+    self.assertEqual(
+        expected, CalculateRuntimeDevicesAndFingerprints(
+            build_info, boot_variable_values))
 
   def test_CalculatePossibleFingerprints_multiple_overrides(self):
     vendor_build_prop = copy.deepcopy(self.VENDOR_BUILD_PROP)
@@ -1422,14 +1430,17 @@
         'ro.product.vendor.name=vendor-product-pro',
         'VENDOR/etc/build_product2.prop':
         'ro.product.vendor.device=vendor-device-product2',
-    })
-    common.OPTIONS.info_dict = common.LoadInfoDict(self.test_dir)
-    common.OPTIONS.boot_variable_values = {
+    }, self.test_dir)
+
+    build_info = common.BuildInfo(common.LoadInfoDict(self.test_dir))
+    boot_variable_values = {
         'ro.boot.sku_name': ['std', 'pro'],
         'ro.boot.device_name': ['product1', 'product2'],
     }
 
-    self.assertEqual({
+    expected_devices = {'vendor-product-device', 'vendor-device-product1',
+                        'vendor-device-product2'}
+    expected_fingerprints = {
         self.constructFingerprint(
             'vendor-product-brand/vendor-product-name/vendor-product-device'),
         self.constructFingerprint(
@@ -1439,5 +1450,108 @@
         self.constructFingerprint(
             'vendor-product-brand/vendor-product-std/vendor-device-product2'),
         self.constructFingerprint(
-            'vendor-product-brand/vendor-product-pro/vendor-device-product2'),
-    }, CalculateRuntimeFingerprints())
+            'vendor-product-brand/vendor-product-pro/vendor-device-product2')
+    }
+    self.assertEqual((expected_devices, expected_fingerprints),
+                     CalculateRuntimeDevicesAndFingerprints(
+                         build_info, boot_variable_values))
+
+  def test_GetPackageMetadata_full_package(self):
+    vendor_build_prop = copy.deepcopy(self.VENDOR_BUILD_PROP)
+    vendor_build_prop.extend([
+        'import /vendor/etc/build_${ro.boot.sku_name}.prop',
+    ])
+    self.writeFiles({
+        'SYSTEM/build.prop': '\n'.join(self.BUILD_PROP),
+        'VENDOR/build.prop': '\n'.join(vendor_build_prop),
+        'VENDOR/etc/build_std.prop':
+        'ro.product.vendor.name=vendor-product-std',
+        'VENDOR/etc/build_pro.prop':
+        'ro.product.vendor.name=vendor-product-pro',
+    }, self.test_dir)
+
+    common.OPTIONS.boot_variable_file = common.MakeTempFile()
+    with open(common.OPTIONS.boot_variable_file, 'w') as f:
+      f.write('ro.boot.sku_name=std,pro')
+
+    build_info = common.BuildInfo(common.LoadInfoDict(self.test_dir))
+    metadata = GetPackageMetadata(build_info)
+    self.assertEqual('vendor-product-device', metadata['pre-device'])
+    fingerprints = [
+        self.constructFingerprint(
+            'vendor-product-brand/vendor-product-name/vendor-product-device'),
+        self.constructFingerprint(
+            'vendor-product-brand/vendor-product-pro/vendor-product-device'),
+        self.constructFingerprint(
+            'vendor-product-brand/vendor-product-std/vendor-product-device'),
+    ]
+    self.assertEqual('|'.join(fingerprints), metadata['post-build'])
+
+  def test_GetPackageMetadata_incremental_package(self):
+    vendor_build_prop = copy.deepcopy(self.VENDOR_BUILD_PROP)
+    vendor_build_prop.extend([
+        'import /vendor/etc/build_${ro.boot.sku_name}.prop',
+    ])
+    self.writeFiles({
+        'SYSTEM/build.prop': '\n'.join(self.BUILD_PROP),
+        'VENDOR/build.prop': '\n'.join(vendor_build_prop),
+        'VENDOR/etc/build_std.prop':
+        'ro.product.vendor.device=vendor-device-std',
+        'VENDOR/etc/build_pro.prop':
+        'ro.product.vendor.device=vendor-device-pro',
+    }, self.test_dir)
+
+    common.OPTIONS.boot_variable_file = common.MakeTempFile()
+    with open(common.OPTIONS.boot_variable_file, 'w') as f:
+      f.write('ro.boot.sku_name=std,pro')
+
+    source_dir = common.MakeTempDir()
+    source_build_prop = [
+        'ro.build.version.release=source-version-release',
+        'ro.build.id=source-build-id',
+        'ro.build.version.incremental=source-version-incremental',
+        'ro.build.type=build-type',
+        'ro.build.tags=build-tags',
+        'ro.build.version.sdk=29',
+        'ro.build.version.security_patch=2020',
+        'ro.build.date.utc=12340000'
+    ]
+    self.writeFiles({
+        'META/misc_info.txt': '\n'.join(self.MISC_INFO),
+        'SYSTEM/build.prop': '\n'.join(source_build_prop),
+        'VENDOR/build.prop': '\n'.join(vendor_build_prop),
+        'VENDOR/etc/build_std.prop':
+        'ro.product.vendor.device=vendor-device-std',
+        'VENDOR/etc/build_pro.prop':
+        'ro.product.vendor.device=vendor-device-pro',
+    }, source_dir)
+    common.OPTIONS.incremental_source = source_dir
+
+    target_info = common.BuildInfo(common.LoadInfoDict(self.test_dir))
+    source_info = common.BuildInfo(common.LoadInfoDict(source_dir))
+
+    metadata = GetPackageMetadata(target_info, source_info)
+    self.assertEqual(
+        'vendor-device-pro|vendor-device-std|vendor-product-device',
+        metadata['pre-device'])
+    suffix = ':source-version-release/source-build-id/' \
+             'source-version-incremental:build-type/build-tags'
+    pre_fingerprints = [
+        'vendor-product-brand/vendor-product-name/vendor-device-pro'
+        '{}'.format(suffix),
+        'vendor-product-brand/vendor-product-name/vendor-device-std'
+        '{}'.format(suffix),
+        'vendor-product-brand/vendor-product-name/vendor-product-device'
+        '{}'.format(suffix),
+    ]
+    self.assertEqual('|'.join(pre_fingerprints), metadata['pre-build'])
+
+    post_fingerprints = [
+        self.constructFingerprint(
+            'vendor-product-brand/vendor-product-name/vendor-device-pro'),
+        self.constructFingerprint(
+            'vendor-product-brand/vendor-product-name/vendor-device-std'),
+        self.constructFingerprint(
+            'vendor-product-brand/vendor-product-name/vendor-product-device'),
+    ]
+    self.assertEqual('|'.join(post_fingerprints), metadata['post-build'])
diff --git a/tools/releasetools/validate_target_files.py b/tools/releasetools/validate_target_files.py
index 1b918cc..69be511 100755
--- a/tools/releasetools/validate_target_files.py
+++ b/tools/releasetools/validate_target_files.py
@@ -352,8 +352,13 @@
     cmd = [info_dict['avb_avbtool'], 'verify_image', '--image', image,
            '--follow_chain_partitions']
 
+    # Custom images.
+    custom_partitions = info_dict.get(
+        "avb_custom_images_partition_list", "").strip().split()
+
     # Append the args for chained partitions if any.
-    for partition in common.AVB_PARTITIONS + common.AVB_VBMETA_PARTITIONS:
+    for partition in (common.AVB_PARTITIONS + common.AVB_VBMETA_PARTITIONS +
+                      tuple(custom_partitions)):
       key_name = 'avb_' + partition + '_key_path'
       if info_dict.get(key_name) is not None:
         if info_dict.get('ab_update') != 'true' and partition == 'recovery':
diff --git a/tools/releasetools/verity_utils.py b/tools/releasetools/verity_utils.py
index e7f84f5..fc83689 100644
--- a/tools/releasetools/verity_utils.py
+++ b/tools/releasetools/verity_utils.py
@@ -695,3 +695,22 @@
       raise HashtreeInfoGenerationError("Failed to reconstruct the verity tree")
 
     return self.hashtree_info
+
+
+def CreateCustomImageBuilder(info_dict, partition_name, partition_size,
+                            key_path, algorithm, signing_args):
+  builder = None
+  if info_dict.get("avb_enable") == "true":
+    builder = VerifiedBootVersion2VerityImageBuilder(
+        partition_name,
+        partition_size,
+        VerifiedBootVersion2VerityImageBuilder.AVB_HASHTREE_FOOTER,
+        info_dict.get("avb_avbtool"),
+        key_path,
+        algorithm,
+        # Salt is None because custom images have no fingerprint property to be
+        # used as the salt.
+        None,
+        signing_args)
+
+  return builder