Merge changes from topic "incremental-workflow" into main

* changes:
  Apply-update: Script to apply updates to device
  create_snapshot: Derive source hash from device
  snapshotctl: Verify data blocks
diff --git a/fs_mgr/libsnapshot/Android.bp b/fs_mgr/libsnapshot/Android.bp
index 966696b..b5b976a 100644
--- a/fs_mgr/libsnapshot/Android.bp
+++ b/fs_mgr/libsnapshot/Android.bp
@@ -374,11 +374,15 @@
     srcs: [
         "snapshotctl.cpp",
         "scratch_super.cpp",
+        "android/snapshot/snapshot.proto",
     ],
     static_libs: [
         "libbrotli",
         "libfstab",
         "libz",
+        "libavb",
+        "libfs_avb",
+        "libcrypto_static",
         "update_metadata-protos",
     ],
     shared_libs: [
@@ -488,7 +492,10 @@
     host_supported: true,
     device_supported: false,
 
-    srcs: ["libsnapshot_cow/create_cow.cpp"],
+    srcs: [
+        "libsnapshot_cow/create_cow.cpp",
+        "android/snapshot/snapshot.proto",
+    ],
 
     cflags: [
         "-Wall",
@@ -498,14 +505,21 @@
     static_libs: [
         "liblog",
         "libbase",
+        "libfstab",
         "libext4_utils",
         "libsnapshot_cow",
         "libcrypto",
         "libbrotli",
         "libz",
+        "libdm",
         "liblz4",
         "libzstd",
         "libgflags",
+        "libavb",
+        "libext2_uuid",
+        "libfs_avb",
+        "libcrypto",
+        "libprotobuf-cpp-lite",
     ],
     shared_libs: [
     ],
diff --git a/fs_mgr/libsnapshot/android/snapshot/snapshot.proto b/fs_mgr/libsnapshot/android/snapshot/snapshot.proto
index 5fb71a3..6f31251 100644
--- a/fs_mgr/libsnapshot/android/snapshot/snapshot.proto
+++ b/fs_mgr/libsnapshot/android/snapshot/snapshot.proto
@@ -283,3 +283,14 @@
     // Size of v3 operation buffer. Needs to be determined during writer initialization
     uint64 estimated_op_count_max = 14;
 }
+
+message VerityHash {
+  // Partition name
+  string partition_name = 1;
+
+  // Salt used for verity hashes
+  string salt = 2;
+
+  // sha256 hash values of each block in the image
+  repeated bytes block_hash = 3;
+}
diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/create_cow.cpp b/fs_mgr/libsnapshot/libsnapshot_cow/create_cow.cpp
index 5497b72..fd4e7da 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/create_cow.cpp
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/create_cow.cpp
@@ -8,6 +8,7 @@
 
 #include <condition_variable>
 #include <cstring>
+#include <fstream>
 #include <future>
 #include <iostream>
 #include <limits>
@@ -17,26 +18,27 @@
 #include <unordered_map>
 #include <vector>
 
-#include <android-base/file.h>
-#include <android-base/logging.h>
-#include <android-base/stringprintf.h>
-#include <android-base/unique_fd.h>
-#include <ext4_utils/ext4_utils.h>
-#include <storage_literals/storage_literals.h>
-
 #include <android-base/chrono_utils.h>
+#include <android-base/file.h>
+#include <android-base/hex.h>
+#include <android-base/logging.h>
 #include <android-base/scopeguard.h>
+#include <android-base/stringprintf.h>
 #include <android-base/strings.h>
-
+#include <android-base/unique_fd.h>
+#include <android/snapshot/snapshot.pb.h>
+#include <ext4_utils/ext4_utils.h>
+#include <fs_avb/fs_avb_util.h>
 #include <gflags/gflags.h>
 #include <libsnapshot/cow_writer.h>
-
 #include <openssl/sha.h>
+#include <storage_literals/storage_literals.h>
 
 DEFINE_string(source, "", "Source partition image");
 DEFINE_string(target, "", "Target partition image");
 DEFINE_string(compression, "lz4",
               "Compression algorithm. Default is set to lz4. Available options: lz4, zstd, gz");
+DEFINE_bool(merkel_tree, false, "If true, source image hash is obtained from verity merkel tree");
 
 namespace android {
 namespace snapshot {
@@ -51,7 +53,8 @@
 class CreateSnapshot {
   public:
     CreateSnapshot(const std::string& src_file, const std::string& target_file,
-                   const std::string& patch_file, const std::string& compression);
+                   const std::string& patch_file, const std::string& compression,
+                   const bool& merkel_tree);
     bool CreateSnapshotPatch();
 
   private:
@@ -108,6 +111,14 @@
     bool WriteOrderedSnapshots();
     bool WriteNonOrderedSnapshots();
     bool VerifyMergeOrder();
+
+    bool CalculateDigest(const void* buffer, size_t size, const void* salt, uint32_t salt_length,
+                         uint8_t* digest);
+    bool ParseSourceMerkelTree();
+
+    bool use_merkel_tree_ = false;
+    std::vector<uint8_t> target_salt_;
+    std::vector<uint8_t> source_salt_;
 };
 
 void CreateSnapshotLogger(android::base::LogId, android::base::LogSeverity severity, const char*,
@@ -120,8 +131,12 @@
 }
 
 CreateSnapshot::CreateSnapshot(const std::string& src_file, const std::string& target_file,
-                               const std::string& patch_file, const std::string& compression)
-    : src_file_(src_file), target_file_(target_file), patch_file_(patch_file) {
+                               const std::string& patch_file, const std::string& compression,
+                               const bool& merkel_tree)
+    : src_file_(src_file),
+      target_file_(target_file),
+      patch_file_(patch_file),
+      use_merkel_tree_(merkel_tree) {
     if (!compression.empty()) {
         compression_ = compression;
     }
@@ -156,7 +171,76 @@
     if (!PrepareParse(src_file_, false)) {
         return false;
     }
-    return ParsePartition();
+
+    if (use_merkel_tree_) {
+        return ParseSourceMerkelTree();
+    } else {
+        return ParsePartition();
+    }
+}
+
+bool CreateSnapshot::CalculateDigest(const void* buffer, size_t size, const void* salt,
+                                     uint32_t salt_length, uint8_t* digest) {
+    SHA256_CTX ctx;
+    if (SHA256_Init(&ctx) != 1) {
+        return false;
+    }
+    if (SHA256_Update(&ctx, salt, salt_length) != 1) {
+        return false;
+    }
+    if (SHA256_Update(&ctx, buffer, size) != 1) {
+        return false;
+    }
+    if (SHA256_Final(digest, &ctx) != 1) {
+        return false;
+    }
+    return true;
+}
+
+bool CreateSnapshot::ParseSourceMerkelTree() {
+    std::string fname = android::base::Basename(target_file_.c_str());
+    std::string partitionName = fname.substr(0, fname.find(".img"));
+
+    auto vbmeta = android::fs_mgr::LoadAndVerifyVbmetaByPath(
+            target_file_, partitionName, "", true, false, false, nullptr, nullptr, nullptr);
+    if (vbmeta == nullptr) {
+        LOG(ERROR) << "LoadAndVerifyVbmetaByPath failed for partition: " << partitionName;
+        return false;
+    }
+    auto descriptor = android::fs_mgr::GetHashtreeDescriptor(partitionName, std::move(*vbmeta));
+    if (descriptor == nullptr) {
+        LOG(ERROR) << "GetHashtreeDescriptor failed for partition: " << partitionName;
+        return false;
+    }
+
+    std::fstream input(src_file_, std::ios::in | std::ios::binary);
+    VerityHash hash;
+    if (!hash.ParseFromIstream(&input)) {
+        LOG(ERROR) << "Failed to parse message.";
+        return false;
+    }
+
+    std::string source_salt = hash.salt();
+    source_salt.erase(std::remove(source_salt.begin(), source_salt.end(), '\0'), source_salt.end());
+    if (!android::base::HexToBytes(source_salt, &source_salt_)) {
+        LOG(ERROR) << "HexToBytes conversion failed for source salt: " << source_salt;
+        return false;
+    }
+
+    std::string target_salt = descriptor->salt;
+    if (!android::base::HexToBytes(target_salt, &target_salt_)) {
+        LOG(ERROR) << "HexToBytes conversion failed for target salt: " << target_salt;
+        return false;
+    }
+
+    std::vector<uint8_t> digest(32, 0);
+    for (int i = 0; i < hash.block_hash_size(); i++) {
+        CalculateDigest(hash.block_hash(i).data(), hash.block_hash(i).size(), target_salt_.data(),
+                        target_salt_.size(), digest.data());
+        source_block_hash_[ToHexString(digest.data(), 32)] = i;
+    }
+
+    return true;
 }
 
 /*
@@ -386,10 +470,21 @@
         while (num_blocks) {
             const void* bufptr = (char*)buffer.get() + buffer_offset;
             uint64_t blkindex = foffset / BLOCK_SZ;
+            std::string hash;
 
-            uint8_t checksum[32];
-            SHA256(bufptr, BLOCK_SZ, checksum);
-            std::string hash = ToHexString(checksum, sizeof(checksum));
+            if (create_snapshot_patch_ && use_merkel_tree_) {
+                std::vector<uint8_t> digest(32, 0);
+                CalculateDigest(bufptr, BLOCK_SZ, target_salt_.data(), target_salt_.size(),
+                                digest.data());
+                std::vector<uint8_t> final_digest(32, 0);
+                CalculateDigest(digest.data(), digest.size(), source_salt_.data(),
+                                source_salt_.size(), final_digest.data());
+                hash = ToHexString(final_digest.data(), final_digest.size());
+            } else {
+                uint8_t checksum[32];
+                SHA256(bufptr, BLOCK_SZ, checksum);
+                hash = ToHexString(checksum, sizeof(checksum));
+            }
 
             if (create_snapshot_patch_) {
                 PrepareMergeBlock(bufptr, blkindex, hash);
@@ -497,7 +592,7 @@
     auto parts = android::base::Split(fname, ".");
     std::string snapshotfile = parts[0] + ".patch";
     android::snapshot::CreateSnapshot snapshot(FLAGS_source, FLAGS_target, snapshotfile,
-                                               FLAGS_compression);
+                                               FLAGS_compression, FLAGS_merkel_tree);
 
     if (!snapshot.CreateSnapshotPatch()) {
         LOG(ERROR) << "Snapshot creation failed";
diff --git a/fs_mgr/libsnapshot/scripts/Android.bp b/fs_mgr/libsnapshot/scripts/Android.bp
index 829f5bc..b99da93 100644
--- a/fs_mgr/libsnapshot/scripts/Android.bp
+++ b/fs_mgr/libsnapshot/scripts/Android.bp
@@ -29,3 +29,8 @@
         "snapshot_proto_python",
     ],
 }
+
+sh_binary_host {
+    name: "apply_update",
+    src: "apply-update.sh",
+}
diff --git a/fs_mgr/libsnapshot/scripts/apply-update.sh b/fs_mgr/libsnapshot/scripts/apply-update.sh
index 90b0119..0b10721 100755
--- a/fs_mgr/libsnapshot/scripts/apply-update.sh
+++ b/fs_mgr/libsnapshot/scripts/apply-update.sh
@@ -1,77 +1,220 @@
 #!/bin/bash
 
-# This is a debug script to quicky test end-to-end flow
-# of snapshot updates without going through update-engine.
+# Copyright 2024 Google Inc. All rights reserved.
 #
-# Usage:
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-#  To update both dynamic and static partitions:
+#     http://www.apache.org/licenses/LICENSE-2.0
 #
-# ./system/core/fs_mgr/libsnapshot/apply_update.sh [--update-static-partitions] [--wipe]
-#
-# --update-static-partitions: This will update bootloader and static A/B
-# partitions
-# --wipe: Allows data wipe as part of update flow
-#
-#  To update dynamic partitions only (this should be used when static
-#  partitions are present in both the slots):
-#
-#  ./system/core/fs_mgr/libsnapshot/apply_update.sh
-#
-#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
-rm -f $OUT/*.patch
+# apply_update.sh: Script to update the device in incremental way
 
-# Compare images and create snapshot patches. Currently, this
-# just compares two identical images in $OUT. In general, any source
-# and target images could be passed to create snapshot patches. However,
-# care must be taken to ensure source images are already present on the device.
-#
-# create_snapshot is a host side binary. Build it with `m create_snapshot`
-create_snapshot --source=$OUT/system.img --target=$OUT/system.img &
-create_snapshot --source=$OUT/product.img --target=$OUT/product.img &
-create_snapshot --source=$OUT/vendor.img --target=$OUT/vendor.img &
-create_snapshot --source=$OUT/system_ext.img --target=$OUT/system_ext.img &
-create_snapshot --source=$OUT/vendor_dlkm.img --target=$OUT/vendor_dlkm.img &
-create_snapshot --source=$OUT/system_dlkm.img --target=$OUT/system_dlkm.img &
+# Ensure OUT directory exists
+if [ -z "$OUT" ]; then
+  echo "Error: OUT environment variable not set." >&2
+  exit 1
+fi
 
-echo "Waiting for snapshot patch creation"
-wait $(jobs -p)
-echo "Snapshot patch creation completed"
+DEVICE_PATH="/data/verity-hash"
+HOST_PATH="$OUT/verity-hash"
 
-mv *.patch $OUT/
+# Create the log file path
+log_file="$HOST_PATH/snapshot.log"
+
+# Function to log messages to both console and log file
+log_message() {
+    message="$1"
+    echo "$message"  # Print to stdout
+    echo "$(date '+%Y-%m-%d %H:%M:%S') - $message" >> "$log_file"  # Append to log file with timestamp
+}
+
+# Function to check for create_snapshot and build if needed
+ensure_create_snapshot() {
+  if ! command -v create_snapshot &> /dev/null; then
+    log_message "create_snapshot not found. Building..."
+    m create_snapshot
+    if [[ $? -ne 0 ]]; then
+      log_message "Error: Failed to build create_snapshot."
+      exit 1
+    fi
+  fi
+}
+
+ensure_create_snapshot
+
+# Function to flash static partitions
+flash_static_partitions() {
+  local wipe_flag="$1"
+
+  fastboot flash bootloader "$OUT"/bootloader.img
+  fastboot reboot bootloader
+  sleep 1
+  fastboot flash radio "$OUT"/radio.img
+  fastboot reboot bootloader
+  sleep 1
+  fastboot flashall --exclude-dynamic-partitions --disable-super-optimization --skip-reboot
+
+  if (( wipe_flag )); then
+      log_message "Wiping device..."
+      fastboot -w
+  fi
+  fastboot reboot
+}
+
+# Function to display the help message
+show_help() {
+  cat << EOF
+Usage: $0 [OPTIONS]
+
+This script updates an Android device with incremental flashing, optionally wiping data and flashing static partitions.
+
+Options:
+  --skip-static-partitions  Skip flashing static partitions (bootloader, radio, boot, vbmeta, dtbo and other static A/B partitions).
+                           * Requires manual update of static partitions on both A/B slots
+                             *before* using this flag.
+                           * Speeds up the update process and development iteration.
+                           * Ideal for development focused on the Android platform (AOSP,
+                             git_main).
+                           * Safe usage: First update static partitions on both slots, then
+                             use this flag for faster development iterations.
+                             Ex:
+                                1: Run this on both the slots - This will update the kernel and other static partitions:
+                                   $fastboot flashall --exclude-dynamic-partitions --disable-super-optimization --skip-reboot
+
+                                2: Update bootloader on both the slots:
+                                    $fastboot flash bootloader $OUT/bootloader.img --slot=all
+
+                                3: Update radio on both the slots:
+                                    $fastboot flash radio $OUT/radio.img --slot=all
+                            Now, the script can safely use this flag for update purpose.
+
+  --wipe                   Wipe user data during the update.
+  --help                   Display this help message.
+
+Environment Variables:
+  OUT                      Path to the directory containing build output.
+                           This is required for the script to function correctly.
+
+Examples:
+  <Development workflow for any project in the platform and build with 'm' to create the images>
+
+  Update the device:
+  $0
+
+  Update the device, but skip flashing static partitions (see above for the usage):
+  $0 --skip-static-partitions
+
+  Update the device and wipe user data:
+  $0 --wipe
+
+  Display this help message:
+  $0 --help
+EOF
+}
+
+skip_static_partitions=0
+wipe_flag=0
+help_flag=0
+
+# Parse arguments
+for arg in "$@"; do
+  case "$arg" in
+    --skip-static-partitions)
+      skip_static_partitions=1
+      ;;
+    --wipe)
+      wipe_flag=1
+      ;;
+    --help)
+      help_flag=1
+      ;;
+    *)
+      echo "Unknown argument: $arg" >&2
+      help_flag=1
+      ;;
+  esac
+done
+
+# Check if help flag is set
+if (( help_flag )); then
+  show_help
+  exit 0
+fi
+
+rm -rf $HOST_PATH
 
 adb root
 adb wait-for-device
-adb shell mkdir -p /data/update/
-adb push $OUT/*.patch /data/update/
 
-if [[ "$2" == "--wipe" ]]; then
-  adb shell snapshotctl apply-update /data/update/ -w
+adb shell rm -rf $DEVICE_PATH
+adb shell mkdir -p $DEVICE_PATH
+
+echo "Extracting device source hash from dynamic partitions"
+adb shell snapshotctl dump-verity-hash $DEVICE_PATH
+adb pull -q $DEVICE_PATH $OUT/
+
+log_message "Entering directory:"
+
+# Navigate to the verity-hash directory
+cd "$HOST_PATH" || { log_message "Error: Could not navigate to $HOST_PATH"; exit 1; }
+
+pwd
+
+# Iterate over all .pb files using a for loop
+for pb_file in *.pb; do
+  # Extract the base filename without the .pb extension
+  base_filename="${pb_file%.*}"
+
+  # Construct the source and target file names
+  source_file="$pb_file"
+  target_file="$OUT/$base_filename.img"
+
+  # Construct the create_snapshot command using an array
+  snapshot_args=(
+    "create_snapshot"
+    "--source" "$source_file"
+    "--target" "$target_file"
+    "--merkel_tree"
+  )
+
+  # Log the command about to be executed
+  log_message "Running: ${snapshot_args[*]}"
+
+  "${snapshot_args[@]}" >> "$log_file" 2>&1 &
+done
+
+log_message "Waiting for snapshot patch creation"
+
+# Wait for all background processes to complete
+wait $(jobs -p)
+
+log_message "Snapshot patches created successfully"
+
+adb push -q $HOST_PATH/*.patch $DEVICE_PATH
+
+log_message "Applying update"
+
+if (( wipe_flag )); then
+  adb shell snapshotctl apply-update $DEVICE_PATH -w
 else
-  adb shell snapshotctl apply-update /data/update/
+  adb shell snapshotctl apply-update $DEVICE_PATH
 fi
 
-# Check if the --update-static-partitions option is provided.
-# For quick developer workflow, there is no need to repeatedly
-# apply static partitions.
-if [[ "$1" == "--update-static-partitions" ]]; then
-  adb reboot bootloader
-  sleep 5
-  if [[ "$2" == "--wipe" ]]; then
-      fastboot -w
-  fi
-  fastboot flash bootloader $OUT/bootloader.img
-  sleep 1
-  fastboot reboot bootloader
-  sleep 1
-  fastboot flash radio $OUT/radio.img
-  sleep 1
-  fastboot reboot bootloader
-  sleep 1
-  fastboot flashall --exclude-dynamic-partitions --disable-super-optimization
+if (( skip_static_partitions )); then
+    log_message "Rebooting device - Skipping flashing static partitions"
+    adb reboot
 else
-  adb reboot
+    log_message "Rebooting device to bootloader"
+    adb reboot bootloader
+    log_message "Waiting to enter fastboot bootloader"
+    flash_static_partitions "$wipe_flag"
 fi
 
-echo "Update completed"
+log_message "Update completed"
diff --git a/fs_mgr/libsnapshot/snapshotctl.cpp b/fs_mgr/libsnapshot/snapshotctl.cpp
index 46de991..e1a3310 100644
--- a/fs_mgr/libsnapshot/snapshotctl.cpp
+++ b/fs_mgr/libsnapshot/snapshotctl.cpp
@@ -30,12 +30,15 @@
 #include <android-base/unique_fd.h>
 
 #include <android-base/chrono_utils.h>
+#include <android-base/hex.h>
 #include <android-base/parseint.h>
 #include <android-base/properties.h>
 #include <android-base/scopeguard.h>
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
+#include <android/snapshot/snapshot.pb.h>
 
+#include <fs_avb/fs_avb_util.h>
 #include <fs_mgr.h>
 #include <fs_mgr_dm_linear.h>
 #include <fstab/fstab.h>
@@ -44,9 +47,13 @@
 #include <libsnapshot/snapshot.h>
 #include <storage_literals/storage_literals.h>
 
+#include <openssl/sha.h>
+
 #include "partition_cow_creator.h"
 #include "scratch_super.h"
 
+#include "utility.h"
+
 #ifdef SNAPSHOTCTL_USERDEBUG_OR_ENG
 #include <BootControlClient.h>
 #endif
@@ -89,7 +96,12 @@
                  "  apply-update\n"
                  "    Apply the incremental OTA update wherein the snapshots are\n"
                  "    directly written to COW block device. This will bypass update-engine\n"
-                 "    and the device will be ready to boot from the target build.\n";
+                 "    and the device will be ready to boot from the target build.\n"
+                 "  dump-verity-hash <directory where verity merkel tree hashes are stored> "
+                 "[-verify]\n"
+                 "    Dump the verity merkel tree hashes at the specified path\n"
+                 "    -verify: Verify the dynamic partition blocks by comparing it with verity "
+                 "merkel tree\n";
     return EX_USAGE;
 }
 
@@ -631,6 +643,252 @@
     return true;
 }
 
+static bool GetBlockHashFromMerkelTree(android::base::borrowed_fd image_fd, uint64_t image_size,
+                                       uint32_t data_block_size, uint32_t hash_block_size,
+                                       uint64_t tree_offset,
+                                       std::vector<std::string>& out_block_hash) {
+    uint32_t padded_digest_size = 32;
+    if (image_size % data_block_size != 0) {
+        LOG(ERROR) << "Image_size: " << image_size
+                   << " not a multiple of data block size: " << data_block_size;
+        return false;
+    }
+
+    // vector of level-size and offset
+    std::vector<std::pair<uint64_t, uint64_t>> levels;
+    uint64_t data_block_count = image_size / data_block_size;
+    uint32_t digests_per_block = hash_block_size / padded_digest_size;
+    uint32_t level_block_count = data_block_count;
+    while (level_block_count > 1) {
+        uint32_t next_level_block_count =
+                (level_block_count + digests_per_block - 1) / digests_per_block;
+        levels.emplace_back(std::make_pair(next_level_block_count * hash_block_size, 0));
+        level_block_count = next_level_block_count;
+    }
+    // root digest
+    levels.emplace_back(std::make_pair(0, 0));
+    // initialize offset
+    for (auto level = std::prev(levels.end()); level != levels.begin(); level--) {
+        std::prev(level)->second = level->second + level->first;
+    }
+
+    // We just want level 0
+    auto level = levels.begin();
+    std::string hash_block(hash_block_size, '\0');
+    uint64_t block_offset = tree_offset + level->second;
+    uint64_t t_read_blocks = 0;
+    uint64_t blockidx = 0;
+    uint64_t num_hash_blocks = level->first / hash_block_size;
+    while ((t_read_blocks < num_hash_blocks) && (blockidx < data_block_count)) {
+        if (!android::base::ReadFullyAtOffset(image_fd, hash_block.data(), hash_block.size(),
+                                              block_offset)) {
+            LOG(ERROR) << "Failed to read tree block at offset: " << block_offset;
+            return false;
+        }
+
+        for (uint32_t offset = 0; offset < hash_block.size(); offset += padded_digest_size) {
+            std::string single_hash = hash_block.substr(offset, padded_digest_size);
+            out_block_hash.emplace_back(single_hash);
+
+            blockidx += 1;
+            if (blockidx >= data_block_count) {
+                break;
+            }
+        }
+
+        block_offset += hash_block_size;
+        t_read_blocks += 1;
+    }
+    return true;
+}
+
+static bool CalculateDigest(const void* buffer, size_t size, const void* salt, uint32_t salt_length,
+                            uint8_t* digest) {
+    SHA256_CTX ctx;
+    if (SHA256_Init(&ctx) != 1) {
+        return false;
+    }
+    if (SHA256_Update(&ctx, salt, salt_length) != 1) {
+        return false;
+    }
+    if (SHA256_Update(&ctx, buffer, size) != 1) {
+        return false;
+    }
+    if (SHA256_Final(digest, &ctx) != 1) {
+        return false;
+    }
+    return true;
+}
+
+bool verify_data_blocks(android::base::borrowed_fd fd, const std::vector<std::string>& block_hash,
+                        std::unique_ptr<android::fs_mgr::FsAvbHashtreeDescriptor>& descriptor,
+                        const std::vector<uint8_t>& salt) {
+    uint64_t data_block_count = descriptor->image_size / descriptor->data_block_size;
+    uint64_t foffset = 0;
+    uint64_t blk = 0;
+
+    std::string hash_block(descriptor->hash_block_size, '\0');
+    while (blk < data_block_count) {
+        if (!android::base::ReadFullyAtOffset(fd, hash_block.data(), descriptor->hash_block_size,
+                                              foffset)) {
+            LOG(ERROR) << "Failed to read from offset: " << foffset;
+            return false;
+        }
+
+        std::string digest(32, '\0');
+        CalculateDigest(hash_block.data(), descriptor->hash_block_size, salt.data(), salt.size(),
+                        reinterpret_cast<uint8_t*>(digest.data()));
+        if (digest != block_hash[blk]) {
+            LOG(ERROR) << "Hash mismatch for block: " << blk << " Expected: " << block_hash[blk]
+                       << " Received: " << digest;
+            return false;
+        }
+
+        foffset += descriptor->hash_block_size;
+        blk += 1;
+    }
+
+    return true;
+}
+
+bool DumpVerityHash(int argc, char** argv) {
+    android::base::InitLogging(argv, &android::base::KernelLogger);
+
+    if (::getuid() != 0) {
+        LOG(ERROR) << "Not running as root. Try \"adb root\" first.";
+        return EXIT_FAILURE;
+    }
+
+    if (argc < 3) {
+        std::cerr
+                << " dump-verity-hash <directory location where verity hash is saved> {-verify}\n";
+        return false;
+    }
+
+    bool verification_required = false;
+    std::string hash_file_path = argv[2];
+    bool metadata_on_super = false;
+    if (argc == 4) {
+        if (argv[3] == "-verify"s) {
+            verification_required = true;
+        }
+    }
+
+    auto& dm = android::dm::DeviceMapper::Instance();
+    auto dm_block_devices = dm.FindDmPartitions();
+    if (dm_block_devices.empty()) {
+        LOG(ERROR) << "No dm-enabled block device is found.";
+        return false;
+    }
+
+    android::fs_mgr::Fstab fstab;
+    if (!ReadDefaultFstab(&fstab)) {
+        LOG(ERROR) << "Failed to read fstab";
+        return false;
+    }
+
+    for (const auto& pair : dm_block_devices) {
+        std::string partition_name = pair.first;
+        android::fs_mgr::FstabEntry* fstab_entry =
+                GetEntryForMountPoint(&fstab, "/" + partition_name);
+        auto vbmeta = LoadAndVerifyVbmeta(*fstab_entry, "", nullptr, nullptr, nullptr);
+        if (vbmeta == nullptr) {
+            LOG(ERROR) << "LoadAndVerifyVbmetaByPath failed for partition: " << partition_name;
+            return false;
+        }
+
+        auto descriptor =
+                android::fs_mgr::GetHashtreeDescriptor(partition_name, std::move(*vbmeta));
+        if (descriptor == nullptr) {
+            LOG(ERROR) << "GetHashtreeDescriptor failed for partition: " << partition_name;
+            return false;
+        }
+
+        std::string device_path = fstab_entry->blk_device;
+        if (!dm.GetDmDevicePathByName(fstab_entry->blk_device, &device_path)) {
+            LOG(ERROR) << "Failed to resolve logical device path for: " << fstab_entry->blk_device;
+            return false;
+        }
+
+        android::base::unique_fd fd(open(device_path.c_str(), O_RDONLY));
+        if (fd < 0) {
+            LOG(ERROR) << "Failed to open file: " << device_path;
+            return false;
+        }
+        std::vector<std::string> block_hash;
+        if (!GetBlockHashFromMerkelTree(fd, descriptor->image_size, descriptor->data_block_size,
+                                        descriptor->hash_block_size, descriptor->tree_offset,
+                                        block_hash)) {
+            LOG(ERROR) << "GetBlockHashFromMerkelTree failed";
+            return false;
+        }
+
+        uint64_t dev_sz = lseek(fd, 0, SEEK_END);
+        uint64_t fec_size = dev_sz - descriptor->image_size;
+        if (fec_size % descriptor->data_block_size != 0) {
+            LOG(ERROR) << "fec_size: " << fec_size
+                       << " isn't multiple of: " << descriptor->data_block_size;
+            return false;
+        }
+
+        std::vector<uint8_t> salt;
+        const std::string& salt_str = descriptor->salt;
+        bool ok = android::base::HexToBytes(salt_str, &salt);
+        if (!ok) {
+            LOG(ERROR) << "HexToBytes conversion failed";
+            return false;
+        }
+        uint64_t file_offset = descriptor->image_size;
+        std::vector<uint8_t> hash_block(descriptor->hash_block_size, 0);
+        while (file_offset < dev_sz) {
+            if (!android::base::ReadFullyAtOffset(fd, hash_block.data(),
+                                                  descriptor->hash_block_size, file_offset)) {
+                LOG(ERROR) << "Failed to read tree block at offset: " << file_offset;
+                return false;
+            }
+            std::string digest(32, '\0');
+            CalculateDigest(hash_block.data(), descriptor->hash_block_size, salt.data(),
+                            salt.size(), reinterpret_cast<uint8_t*>(digest.data()));
+            block_hash.push_back(digest);
+            file_offset += descriptor->hash_block_size;
+            fec_size -= descriptor->hash_block_size;
+        }
+
+        if (fec_size != 0) {
+            LOG(ERROR) << "Checksum calculation pending: " << fec_size;
+            return false;
+        }
+
+        if (verification_required) {
+            if (!verify_data_blocks(fd, block_hash, descriptor, salt)) {
+                LOG(ERROR) << "verify_data_blocks failed";
+                return false;
+            }
+        }
+
+        VerityHash verity_hash;
+        verity_hash.set_partition_name(partition_name);
+        verity_hash.set_salt(salt_str);
+        for (auto hash : block_hash) {
+            verity_hash.add_block_hash(hash.data(), hash.size());
+        }
+        std::string hash_file = hash_file_path + "/" + partition_name + ".pb";
+        std::string content;
+        if (!verity_hash.SerializeToString(&content)) {
+            LOG(ERROR) << "Unable to serialize verity_hash";
+            return false;
+        }
+        if (!WriteStringToFileAtomic(content, hash_file)) {
+            PLOG(ERROR) << "Unable to write VerityHash to " << hash_file;
+            return false;
+        }
+
+        LOG(INFO) << partition_name
+                  << ": GetBlockHashFromMerkelTree success. Num Blocks: " << block_hash.size();
+    }
+    return true;
+}
+
 bool MapPrecreatedSnapshots(int argc, char** argv) {
     android::base::InitLogging(argv, &android::base::KernelLogger);
 
@@ -827,6 +1085,7 @@
         {"unmap-snapshots", UnMapPrecreatedSnapshots},
         {"delete-snapshots", DeletePrecreatedSnapshots},
         {"revert-snapshots", RemovePrecreatedSnapshots},
+        {"dump-verity-hash", DumpVerityHash},
 #endif
         {"unmap", UnmapCmdHandler},
         // clang-format on