[meta-security][PATCH] dm-verity-img.bbclass: Fix the hash offset alignment issue

[meta-security][PATCH] dm-verity-img.bbclass: Fix the hash offset alignment issue

[Kevin Hao]

When using the kernel module parameter "dm-mod.create=" [1] to create
the device-mapper device, the hash offset address we passed to kernel
module is the hash block number. That means the hash offset address
would have to be aligned to the max(data_block_size, hash_block_size),
otherwise there would be no way to set the correct hash offset address
via "dm-mo.create=".

[1] https://www.kernel.org/doc/Documentation/admin-guide/device-mapper/dm-init.rst

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
---
 classes/dm-verity-img.bbclass | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/classes/dm-verity-img.bbclass b/classes/dm-verity-img.bbclass
index e5946bc3279c..8fc98de8a2bd 100644
--- a/classes/dm-verity-img.bbclass
+++ b/classes/dm-verity-img.bbclass
@@ -25,6 +25,9 @@ STAGING_VERITY_DIR ?= "${TMPDIR}/work-shared/${MACHINE}/dm-verity"
 # Define the data block size to use in veritysetup.
 DM_VERITY_IMAGE_DATA_BLOCK_SIZE ?= "1024"
 
+# Define the hash block size to use in veritysetup.
+DM_VERITY_IMAGE_HASH_BLOCK_SIZE ?= "4096"
+
 # Process the output from veritysetup and generate the corresponding .env
 # file. The output from veritysetup is not very machine-friendly so we need to
 # convert it to some better format. Let's drop the first line (doesn't contain
@@ -56,11 +59,18 @@ verity_setup() {
     local SIZE=$(stat --printf="%s" $INPUT)
     local OUTPUT=$INPUT.verity
 
+    if [ ${DM_VERITY_IMAGE_DATA_BLOCK_SIZE} -ge ${DM_VERITY_IMAGE_HASH_BLOCK_SIZE} ]; then
+        align=${DM_VERITY_IMAGE_DATA_BLOCK_SIZE}
+    else
+        align=${DM_VERITY_IMAGE_HASH_BLOCK_SIZE}
+    fi
+    SIZE=$(expr \( $SIZE + $align - 1 \) / $align \* $align)
+
     cp -a $INPUT $OUTPUT
 
     # Let's drop the first line of output (doesn't contain any useful info)
     # and feed the rest to another function.
-    veritysetup --data-block-size=${DM_VERITY_IMAGE_DATA_BLOCK_SIZE} --hash-offset=$SIZE format $OUTPUT $OUTPUT | tail -n +2 | process_verity
+    veritysetup --data-block-size=${DM_VERITY_IMAGE_DATA_BLOCK_SIZE} --hash-block-size=${DM_VERITY_IMAGE_HASH_BLOCK_SIZE} --hash-offset=$SIZE format $OUTPUT $OUTPUT | tail -n +2 | process_verity
 }
 
 VERITY_TYPES = " \
-- 
2.38.1