Error correction: Append codes to verified partitions
Append error-correcting codes to verified partitions provided that
PRODUCT_SUPPORTS_VERITY_FEC is true.
This moves verity metadata to be after the hash tree, and requires
matching changes from
Ide48f581bbba77aed6132f77b309db71630d81ed
Bug: 21893453
Change-Id: I6945cbab99e214566a1f9d3702333f2dbbc35816
diff --git a/core/Makefile b/core/Makefile
index b1b3d13..0d24719 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -724,6 +724,9 @@
ifeq (true,$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VERITY))
INTERNAL_USERIMAGES_DEPS += $(BUILD_VERITY_TREE) $(APPEND2SIMG) $(VERITY_SIGNER)
+ifeq (true,$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VERITY_FEC))
+INTERNAL_USERIMAGES_DEPS += $(FEC)
+endif
endif
SELINUX_FC := $(TARGET_ROOT_OUT)/file_contexts.bin
@@ -754,6 +757,7 @@
$(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VERITY),$(hide) echo "verity=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VERITY)" >> $(1))
$(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VERITY),$(hide) echo "verity_key=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VERITY_SIGNING_KEY)" >> $(1))
$(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VERITY),$(hide) echo "verity_signer_cmd=$(notdir $(VERITY_SIGNER))" >> $(1))
+$(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VERITY_FEC),$(hide) echo "verity_fec=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VERITY_FEC)" >> $(1))
$(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_VERITY_PARTITION),$(hide) echo "system_verity_block_device=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_VERITY_PARTITION)" >> $(1))
$(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VENDOR_VERITY_PARTITION),$(hide) echo "vendor_verity_block_device=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VENDOR_VERITY_PARTITION)" >> $(1))
$(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VBOOT),$(hide) echo "vboot=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VBOOT)" >> $(1))
@@ -1363,7 +1367,8 @@
$(HOST_OUT_EXECUTABLES)/verity_signer \
$(HOST_OUT_EXECUTABLES)/append2simg \
$(HOST_OUT_EXECUTABLES)/img2simg \
- $(HOST_OUT_EXECUTABLES)/boot_signer
+ $(HOST_OUT_EXECUTABLES)/boot_signer \
+ $(HOST_OUT_EXECUTABLES)/fec
# Shared libraries.
OTATOOLS += \
diff --git a/core/config.mk b/core/config.mk
index 1db3d7a..2b7cb7f 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -515,6 +515,7 @@
BOOT_SIGNER := $(HOST_OUT_EXECUTABLES)/boot_signer
FUTILITY := prebuilts/misc/$(BUILD_OS)-$(HOST_PREBUILT_ARCH)/futility/futility
VBOOT_SIGNER := prebuilts/misc/scripts/vboot_signer/vboot_signer.sh
+FEC := $(HOST_OUT_EXECUTABLES)/fec
# ACP is always for the build OS, not for the host OS
ACP := $(BUILD_OUT_EXECUTABLES)/acp$(BUILD_EXECUTABLE_SUFFIX)
diff --git a/core/product.mk b/core/product.mk
index 2c846aa..f242e82 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -100,6 +100,7 @@
PRODUCT_SUPPORTS_BOOT_SIGNER \
PRODUCT_SUPPORTS_VBOOT \
PRODUCT_SUPPORTS_VERITY \
+ PRODUCT_SUPPORTS_VERITY_FEC \
PRODUCT_OEM_PROPERTIES \
PRODUCT_SYSTEM_PROPERTY_BLACKLIST \
PRODUCT_SYSTEM_SERVER_JARS \
diff --git a/target/product/verity.mk b/target/product/verity.mk
index 6676ffe..0badb9f 100644
--- a/target/product/verity.mk
+++ b/target/product/verity.mk
@@ -21,6 +21,7 @@
ifneq (,$(user_variant))
PRODUCT_SUPPORTS_BOOT_SIGNER := true
PRODUCT_SUPPORTS_VERITY := true
+ PRODUCT_SUPPORTS_VERITY_FEC := true
# The dev key is used to sign boot and recovery images, and the verity
# metadata table. Actual product deliverables will be re-signed by hand.
diff --git a/tools/releasetools/build_image.py b/tools/releasetools/build_image.py
index 470a108..cd750e8 100755
--- a/tools/releasetools/build_image.py
+++ b/tools/releasetools/build_image.py
@@ -33,6 +33,7 @@
OPTIONS = common.OPTIONS
FIXED_SALT = "aee087a5be3b982978c923f566a94613496b417f2af592639bc80d141e34dfe7"
+BLOCK_SIZE = 4096
def RunCommand(cmd):
"""Echo and run the given command.
@@ -48,6 +49,14 @@
print "%s" % (output.rstrip(),)
return (output, p.returncode)
+def GetVerityFECSize(partition_size):
+ cmd = "fec -s %d" % partition_size
+ status, output = commands.getstatusoutput(cmd)
+ if status:
+ print output
+ return False, 0
+ return True, int(output)
+
def GetVerityTreeSize(partition_size):
cmd = "build_verity_tree -s %d"
cmd %= partition_size
@@ -67,7 +76,22 @@
return False, 0
return True, int(output)
-def AdjustPartitionSizeForVerity(partition_size):
+def GetVeritySize(partition_size, fec_supported):
+ success, verity_tree_size = GetVerityTreeSize(partition_size)
+ if not success:
+ return 0
+ success, verity_metadata_size = GetVerityMetadataSize(partition_size)
+ if not success:
+ return 0
+ verity_size = verity_tree_size + verity_metadata_size
+ if fec_supported:
+ success, fec_size = GetVerityFECSize(partition_size + verity_size)
+ if not success:
+ return 0
+ return verity_size + fec_size
+ return verity_size
+
+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.
@@ -76,13 +100,43 @@
Returns:
The size of the partition adjusted for verity metadata.
"""
- success, verity_tree_size = GetVerityTreeSize(partition_size)
- if not success:
- return 0
- success, verity_metadata_size = GetVerityMetadataSize(partition_size)
- if not success:
- return 0
- return partition_size - verity_tree_size - verity_metadata_size
+ 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
+ lo = partition_size - GetVeritySize(hi, fec_supported)
+ result = lo
+
+ # do a binary search for the optimal size
+ while lo < hi:
+ i = ((lo + hi) // (2 * BLOCK_SIZE)) * BLOCK_SIZE
+ size = i + GetVeritySize(i, fec_supported)
+ if size <= partition_size:
+ if result < i:
+ result = i
+ lo = i + BLOCK_SIZE
+ else:
+ hi = i
+
+ AdjustPartitionSizeForVerity.results[key] = result
+ return result
+
+AdjustPartitionSizeForVerity.results = {}
+
+def BuildVerityFEC(sparse_image_path, verity_fec_path, prop_dict):
+ cmd = "fec -e %s %s" % (sparse_image_path, verity_fec_path)
+ print cmd
+ status, output = commands.getstatusoutput(cmd)
+ if status:
+ print "Could not build FEC data! Error: %s" % output
+ return False
+ return True
def BuildVerityTree(sparse_image_path, verity_image_path, prop_dict):
cmd = "build_verity_tree -A %s %s %s" % (
@@ -130,12 +184,12 @@
def BuildVerifiedImage(data_image_path, verity_image_path,
verity_metadata_path):
- if not Append2Simg(data_image_path, verity_metadata_path,
- "Could not append verity metadata!"):
- return False
if not Append2Simg(data_image_path, verity_image_path,
"Could not append verity tree!"):
return False
+ if not Append2Simg(data_image_path, verity_metadata_path,
+ "Could not append verity metadata!"):
+ return False
return True
def UnsparseImage(sparse_image_path, replace=True):
@@ -154,7 +208,7 @@
return False, None
return True, unsparse_image_path
-def MakeVerityEnabledImage(out_file, prop_dict):
+def MakeVerityEnabledImage(out_file, fec_supported, prop_dict):
"""Creates an image that is verifiable using dm-verity.
Args:
@@ -180,6 +234,7 @@
# 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
if not BuildVerityTree(out_file, verity_image_path, prop_dict):
@@ -201,6 +256,16 @@
shutil.rmtree(tempdir_name, ignore_errors=True)
return False
+ if fec_supported:
+ # build FEC for the entire partition, including metadata
+ if not BuildVerityFEC(out_file, verity_fec_path, prop_dict):
+ shutil.rmtree(tempdir_name, ignore_errors=True)
+ return False
+
+ if not Append2Simg(out_file, verity_fec_path, "Could not append FEC!"):
+ shutil.rmtree(tempdir_name, ignore_errors=True)
+ return False
+
shutil.rmtree(tempdir_name, ignore_errors=True)
return True
@@ -248,12 +313,14 @@
is_verity_partition = "verity_block_device" in prop_dict
verity_supported = prop_dict.get("verity") == "true"
+ verity_fec_supported = prop_dict.get("verity_fec") == "true"
+
# Adjust the partition size to make room for the hashes if this is to be
# verified.
if verity_supported and is_verity_partition and fs_spans_partition:
partition_size = int(prop_dict.get("partition_size"))
-
- adjusted_size = AdjustPartitionSizeForVerity(partition_size)
+ adjusted_size = AdjustPartitionSizeForVerity(partition_size,
+ verity_fec_supported)
if not adjusted_size:
return False
prop_dict["partition_size"] = str(adjusted_size)
@@ -366,7 +433,7 @@
"%d" % (mount_point, image_size, partition_size))
return False
if verity_supported and is_verity_partition:
- if 2 * image_size - AdjustPartitionSizeForVerity(image_size) > partition_size:
+ if 2 * image_size - AdjustPartitionSizeForVerity(image_size, verity_fec_supported) > partition_size:
print "Error: No more room on %s to fit verity data" % mount_point
return False
prop_dict["original_partition_size"] = prop_dict["partition_size"]
@@ -374,7 +441,7 @@
# create the verified image if this is to be verified
if verity_supported and is_verity_partition:
- if not MakeVerityEnabledImage(out_file, prop_dict):
+ if not MakeVerityEnabledImage(out_file, verity_fec_supported, prop_dict):
return False
if run_fsck and prop_dict.get("skip_fsck") != "true":
@@ -416,7 +483,8 @@
"skip_fsck",
"verity",
"verity_key",
- "verity_signer_cmd"
+ "verity_signer_cmd",
+ "verity_fec"
)
for p in common_props:
copy_prop(p, p)
