diff --git a/fs_mgr/fs_mgr_slotselect.cpp b/fs_mgr/fs_mgr_slotselect.cpp
index 3cb718c..41cd7dd 100644
--- a/fs_mgr/fs_mgr_slotselect.cpp
+++ b/fs_mgr/fs_mgr_slotselect.cpp
@@ -34,6 +34,12 @@
     return "";
 }
 
+// Returns "_b" or "_a", which is *the other* slot of androidboot.slot_suffix
+// in kernel cmdline, or an empty string if that parameter does not exist.
+std::string fs_mgr_get_other_slot_suffix() {
+    return other_suffix(fs_mgr_get_slot_suffix());
+}
+
 // Returns "_a" or "_b" based on androidboot.slot_suffix in kernel cmdline, or an empty string
 // if that parameter does not exist.
 std::string fs_mgr_get_slot_suffix() {
diff --git a/fs_mgr/include_fstab/fstab/fstab.h b/fs_mgr/include_fstab/fstab/fstab.h
index 4a05949..38f96c0 100644
--- a/fs_mgr/include_fstab/fstab/fstab.h
+++ b/fs_mgr/include_fstab/fstab/fstab.h
@@ -98,6 +98,7 @@
 int fs_mgr_is_fs_verity(const struct fstab_rec* fstab);
 
 std::string fs_mgr_get_slot_suffix();
+std::string fs_mgr_get_other_slot_suffix();
 std::set<std::string> fs_mgr_get_boot_devices();
 
 struct FstabEntry {
diff --git a/fs_mgr/libfs_avb/Android.bp b/fs_mgr/libfs_avb/Android.bp
index 6f368e4..191e803 100644
--- a/fs_mgr/libfs_avb/Android.bp
+++ b/fs_mgr/libfs_avb/Android.bp
@@ -56,6 +56,11 @@
         "tests/data/*",
     ],
     static_libs: [
+        "libavb",
+        "libavb_host_sysdeps",
+        "libdm",
+        "libfs_avb",
+        "libfstab",
         "libgtest_host",
     ],
     shared_libs: [
@@ -86,8 +91,12 @@
     static_libs: [
         "libfs_avb_test_util",
     ],
+    shared_libs: [
+        "libcrypto",
+    ],
     srcs: [
         "tests/basic_test.cpp",
+        "tests/fs_avb_test.cpp",
     ],
 }
 
@@ -96,10 +105,11 @@
     defaults: ["libfs_avb_host_test_defaults"],
     static_libs: [
         "libfs_avb_test_util",
-        "libfstab",
     ],
     srcs: [
+        "avb_util.cpp",
         "util.cpp",
+        "tests/avb_util_test.cpp",
         "tests/util_test.cpp",
     ],
 }
diff --git a/fs_mgr/libfs_avb/avb_ops.cpp b/fs_mgr/libfs_avb/avb_ops.cpp
index 3efa794..6a3e2c0 100644
--- a/fs_mgr/libfs_avb/avb_ops.cpp
+++ b/fs_mgr/libfs_avb/avb_ops.cpp
@@ -29,6 +29,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
+
 #include <string>
 
 #include <android-base/macros.h>
@@ -190,7 +191,8 @@
     // Copies avb_slot_data->vbmeta_images[].
     for (size_t i = 0; i < avb_slot_data->num_vbmeta_images; i++) {
         out_vbmeta_images->emplace_back(VBMetaData(avb_slot_data->vbmeta_images[i].vbmeta_data,
-                                                   avb_slot_data->vbmeta_images[i].vbmeta_size));
+                                                   avb_slot_data->vbmeta_images[i].vbmeta_size,
+                                                   avb_slot_data->vbmeta_images[i].partition_name));
     }
 
     // Free the local resource.
diff --git a/fs_mgr/libfs_avb/avb_util.cpp b/fs_mgr/libfs_avb/avb_util.cpp
index 0ceb6ee..f57c9d6 100644
--- a/fs_mgr/libfs_avb/avb_util.cpp
+++ b/fs_mgr/libfs_avb/avb_util.cpp
@@ -16,19 +16,67 @@
 
 #include "avb_util.h"
 
+#include <unistd.h>
+
 #include <array>
 #include <sstream>
 
 #include <android-base/file.h>
+#include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 
 #include "util.h"
 
+using android::base::StartsWith;
 using android::base::unique_fd;
 
 namespace android {
 namespace fs_mgr {
 
+// Helper functions to print enum class VBMetaVerifyResult.
+const char* VBMetaVerifyResultToString(VBMetaVerifyResult result) {
+    // clang-format off
+    static const char* const name[] = {
+        "ResultSuccess",
+        "ResultError",
+        "ResultErrorVerification",
+        "ResultUnknown",
+    };
+    // clang-format on
+
+    uint32_t index = static_cast<uint32_t>(result);
+    uint32_t unknown_index = sizeof(name) / sizeof(char*) - 1;
+    if (index >= unknown_index) {
+        index = unknown_index;
+    }
+
+    return name[index];
+}
+
+std::ostream& operator<<(std::ostream& os, VBMetaVerifyResult result) {
+    os << VBMetaVerifyResultToString(result);
+    return os;
+}
+
+// class VBMetaData
+// ----------------
+std::unique_ptr<AvbVBMetaImageHeader> VBMetaData::GetVBMetaHeader(bool update_vbmeta_size) {
+    auto vbmeta_header(std::make_unique<AvbVBMetaImageHeader>());
+
+    if (!vbmeta_header) return nullptr;
+
+    /* Byteswap the header. */
+    avb_vbmeta_image_header_to_host_byte_order((AvbVBMetaImageHeader*)vbmeta_ptr_.get(),
+                                               vbmeta_header.get());
+    if (update_vbmeta_size) {
+        vbmeta_size_ = sizeof(AvbVBMetaImageHeader) +
+                       vbmeta_header->authentication_data_block_size +
+                       vbmeta_header->auxiliary_data_block_size;
+    }
+
+    return vbmeta_header;
+}
+
 // Constructs dm-verity arguments for sending DM_TABLE_LOAD ioctl to kernel.
 // See the following link for more details:
 // https://gitlab.com/cryptsetup/cryptsetup/wikis/DMVerity
@@ -173,5 +221,300 @@
     return true;
 }
 
+// Converts a AVB partition_name (without A/B suffix) to a device partition name.
+// e.g.,       "system" => "system_a",
+//       "system_other" => "system_b".
+//
+// If the device is non-A/B, converts it to a partition name without suffix.
+// e.g.,       "system" => "system",
+//       "system_other" => "system".
+std::string AvbPartitionToDevicePatition(const std::string& avb_partition_name,
+                                         const std::string& ab_suffix,
+                                         const std::string& ab_other_suffix) {
+    bool is_other_slot = false;
+    std::string sanitized_partition_name(avb_partition_name);
+
+    auto other_suffix = sanitized_partition_name.rfind("_other");
+    if (other_suffix != std::string::npos) {
+        sanitized_partition_name.erase(other_suffix);  // converts system_other => system
+        is_other_slot = true;
+    }
+
+    auto append_suffix = is_other_slot ? ab_other_suffix : ab_suffix;
+    return sanitized_partition_name + append_suffix;
+}
+
+off64_t GetTotalSize(int fd) {
+    off64_t saved_current = lseek64(fd, 0, SEEK_CUR);
+    if (saved_current == -1) {
+        PERROR << "Failed to get current position";
+        return -1;
+    }
+
+    // lseek64() returns the resulting offset location from the beginning of the file.
+    off64_t total_size = lseek64(fd, 0, SEEK_END);
+    if (total_size == -1) {
+        PERROR << "Failed to lseek64 to end of the partition";
+        return -1;
+    }
+
+    // Restores the original offset.
+    if (lseek64(fd, saved_current, SEEK_SET) == -1) {
+        PERROR << "Failed to lseek64 to the original offset: " << saved_current;
+    }
+
+    return total_size;
+}
+
+std::unique_ptr<AvbFooter> GetAvbFooter(int fd) {
+    std::array<uint8_t, AVB_FOOTER_SIZE> footer_buf;
+    auto footer(std::make_unique<AvbFooter>());
+
+    off64_t footer_offset = GetTotalSize(fd) - AVB_FOOTER_SIZE;
+
+    ssize_t num_read =
+            TEMP_FAILURE_RETRY(pread64(fd, footer_buf.data(), AVB_FOOTER_SIZE, footer_offset));
+    if (num_read < 0 || num_read != AVB_FOOTER_SIZE) {
+        PERROR << "Failed to read AVB footer";
+        return nullptr;
+    }
+
+    if (!avb_footer_validate_and_byteswap((const AvbFooter*)footer_buf.data(), footer.get())) {
+        PERROR << "AVB footer verification failed.";
+        return nullptr;
+    }
+
+    return footer;
+}
+
+bool VerifyPublicKeyBlob(const uint8_t* key, size_t length, const std::string& expected_key_blob) {
+    if (expected_key_blob.empty()) {  // no expectation of the key, return true.
+        return true;
+    }
+    if (expected_key_blob.size() != length) {
+        return false;
+    }
+    if (0 == memcmp(key, expected_key_blob.data(), length)) {
+        return true;
+    }
+    return false;
+}
+
+VBMetaVerifyResult VerifyVBMetaSignature(const VBMetaData& vbmeta,
+                                         const std::string& expected_public_key_blob) {
+    const uint8_t* pk_data;
+    size_t pk_len;
+    ::AvbVBMetaVerifyResult vbmeta_ret;
+
+    vbmeta_ret = avb_vbmeta_image_verify(vbmeta.data(), vbmeta.size(), &pk_data, &pk_len);
+
+    switch (vbmeta_ret) {
+        case AVB_VBMETA_VERIFY_RESULT_OK:
+            if (pk_data == nullptr || pk_len <= 0) {
+                LERROR << vbmeta.partition()
+                       << ": Error verifying vbmeta image: failed to get public key";
+                return VBMetaVerifyResult::kError;
+            }
+            if (!VerifyPublicKeyBlob(pk_data, pk_len, expected_public_key_blob)) {
+                LERROR << vbmeta.partition() << ": Error verifying vbmeta image: public key used to"
+                       << " sign data does not match key in chain descriptor";
+                return VBMetaVerifyResult::kErrorVerification;
+            }
+            return VBMetaVerifyResult::kSuccess;
+        case AVB_VBMETA_VERIFY_RESULT_OK_NOT_SIGNED:
+        case AVB_VBMETA_VERIFY_RESULT_HASH_MISMATCH:
+        case AVB_VBMETA_VERIFY_RESULT_SIGNATURE_MISMATCH:
+            LERROR << vbmeta.partition() << ": Error verifying vbmeta image: "
+                   << avb_vbmeta_verify_result_to_string(vbmeta_ret);
+            return VBMetaVerifyResult::kErrorVerification;
+        case AVB_VBMETA_VERIFY_RESULT_INVALID_VBMETA_HEADER:
+            // No way to continue this case.
+            LERROR << vbmeta.partition() << ": Error verifying vbmeta image: invalid vbmeta header";
+            break;
+        case AVB_VBMETA_VERIFY_RESULT_UNSUPPORTED_VERSION:
+            // No way to continue this case.
+            LERROR << vbmeta.partition()
+                   << ": Error verifying vbmeta image: unsupported AVB version";
+            break;
+        default:
+            LERROR << "Unknown vbmeta image verify return value: " << vbmeta_ret;
+            break;
+    }
+
+    return VBMetaVerifyResult::kError;
+}
+
+std::unique_ptr<VBMetaData> VerifyVBMetaData(int fd, const std::string& partition_name,
+                                             const std::string& expected_public_key_blob,
+                                             VBMetaVerifyResult* out_verify_result) {
+    uint64_t vbmeta_offset = 0;
+    uint64_t vbmeta_size = VBMetaData::kMaxVBMetaSize;
+    bool is_vbmeta_partition = StartsWith(partition_name, "vbmeta");
+
+    if (!is_vbmeta_partition) {
+        std::unique_ptr<AvbFooter> footer = GetAvbFooter(fd);
+        if (!footer) {
+            return nullptr;
+        }
+        vbmeta_offset = footer->vbmeta_offset;
+        vbmeta_size = footer->vbmeta_size;
+    }
+
+    if (vbmeta_size > VBMetaData::kMaxVBMetaSize) {
+        LERROR << "VbMeta size in footer exceeds kMaxVBMetaSize";
+        return nullptr;
+    }
+
+    auto vbmeta = std::make_unique<VBMetaData>(vbmeta_size, partition_name);
+    ssize_t num_read = TEMP_FAILURE_RETRY(pread64(fd, vbmeta->data(), vbmeta_size, vbmeta_offset));
+    // Allows partial read for vbmeta partition, because its vbmeta_size is kMaxVBMetaSize.
+    if (num_read < 0 || (!is_vbmeta_partition && static_cast<uint64_t>(num_read) != vbmeta_size)) {
+        PERROR << partition_name << ": Failed to read vbmeta at offset " << vbmeta_offset
+               << " with size " << vbmeta_size;
+        return nullptr;
+    }
+
+    auto verify_result = VerifyVBMetaSignature(*vbmeta, expected_public_key_blob);
+    if (out_verify_result != nullptr) *out_verify_result = verify_result;
+
+    if (verify_result == VBMetaVerifyResult::kSuccess ||
+        verify_result == VBMetaVerifyResult::kErrorVerification) {
+        return vbmeta;
+    }
+
+    return nullptr;
+}
+
+bool RollbackDetected(const std::string& partition_name ATTRIBUTE_UNUSED,
+                      uint64_t rollback_index ATTRIBUTE_UNUSED) {
+    // TODO(bowgotsai): Support rollback protection.
+    return false;
+}
+
+std::vector<ChainInfo> GetChainPartitionInfo(const VBMetaData& vbmeta, bool* fatal_error) {
+    CHECK(fatal_error != nullptr);
+    std::vector<ChainInfo> chain_partitions;
+
+    size_t num_descriptors;
+    std::unique_ptr<const AvbDescriptor* [], decltype(&avb_free)> descriptors(
+            avb_descriptor_get_all(vbmeta.data(), vbmeta.size(), &num_descriptors), avb_free);
+
+    if (!descriptors || num_descriptors < 1) {
+        return {};
+    }
+
+    for (size_t i = 0; i < num_descriptors; i++) {
+        AvbDescriptor desc;
+        if (!avb_descriptor_validate_and_byteswap(descriptors[i], &desc)) {
+            LERROR << "Descriptor[" << i << "] is invalid in vbmeta: " << vbmeta.partition();
+            *fatal_error = true;
+            return {};
+        }
+        if (desc.tag == AVB_DESCRIPTOR_TAG_CHAIN_PARTITION) {
+            AvbChainPartitionDescriptor chain_desc;
+            if (!avb_chain_partition_descriptor_validate_and_byteswap(
+                        (AvbChainPartitionDescriptor*)descriptors[i], &chain_desc)) {
+                LERROR << "Chain descriptor[" << i
+                       << "] is invalid in vbmeta: " << vbmeta.partition();
+                *fatal_error = true;
+                return {};
+            }
+            const char* chain_partition_name =
+                    ((const char*)descriptors[i]) + sizeof(AvbChainPartitionDescriptor);
+            const char* chain_public_key_blob =
+                    chain_partition_name + chain_desc.partition_name_len;
+            chain_partitions.emplace_back(
+                    std::string(chain_partition_name, chain_desc.partition_name_len),
+                    std::string(chain_public_key_blob, chain_desc.public_key_len));
+        }
+    }
+
+    return chain_partitions;
+}
+
+VBMetaVerifyResult LoadAndVerifyVbmetaImpl(
+        const std::string& partition_name, const std::string& ab_suffix,
+        const std::string& ab_other_suffix, const std::string& expected_public_key_blob,
+        bool allow_verification_error, bool load_chained_vbmeta, bool rollback_protection,
+        std::function<std::string(const std::string&)> device_path_constructor,
+        bool is_chained_vbmeta, std::vector<VBMetaData>* out_vbmeta_images) {
+    // Ensures the device path (might be a symlink created by init) is ready to access.
+    auto device_path = device_path_constructor(
+            AvbPartitionToDevicePatition(partition_name, ab_suffix, ab_other_suffix));
+    if (!WaitForFile(device_path, 1s)) {
+        PERROR << "No such partition: " << device_path;
+        return VBMetaVerifyResult::kError;
+    }
+
+    unique_fd fd(TEMP_FAILURE_RETRY(open(device_path.c_str(), O_RDONLY | O_CLOEXEC)));
+    if (fd < 0) {
+        PERROR << "Failed to open: " << device_path;
+        return VBMetaVerifyResult::kError;
+    }
+
+    VBMetaVerifyResult verify_result;
+    std::unique_ptr<VBMetaData> vbmeta =
+            VerifyVBMetaData(fd, partition_name, expected_public_key_blob, &verify_result);
+    if (!vbmeta) {
+        LERROR << partition_name << ": Failed to load vbmeta, result: " << verify_result;
+        return VBMetaVerifyResult::kError;
+    }
+
+    if (!allow_verification_error && verify_result == VBMetaVerifyResult::kErrorVerification) {
+        LERROR << partition_name << ": allow verification error is not allowed";
+        return VBMetaVerifyResult::kError;
+    }
+
+    std::unique_ptr<AvbVBMetaImageHeader> vbmeta_header =
+            vbmeta->GetVBMetaHeader(true /* update_vbmeta_size */);
+    if (!vbmeta_header) {
+        LERROR << partition_name << ": Failed to get vbmeta header";
+        return VBMetaVerifyResult::kError;
+    }
+
+    if (rollback_protection && RollbackDetected(partition_name, vbmeta_header->rollback_index)) {
+        return VBMetaVerifyResult::kError;
+    }
+
+    // vbmeta flags can only be set by the top-level vbmeta image.
+    if (is_chained_vbmeta && vbmeta_header->flags != 0) {
+        LERROR << partition_name << ": chained vbmeta image has non-zero flags";
+        return VBMetaVerifyResult::kError;
+    }
+
+    if (out_vbmeta_images) {
+        out_vbmeta_images->emplace_back(std::move(*vbmeta));
+    }
+
+    // If verification has been disabled by setting a bit in the image, we're done.
+    if (vbmeta_header->flags & AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED) {
+        LWARNING << "VERIFICATION_DISABLED bit is set for partition: " << partition_name;
+        return verify_result;
+    }
+
+    if (load_chained_vbmeta) {
+        bool fatal_error = false;
+        auto chain_partitions = GetChainPartitionInfo(*out_vbmeta_images->rbegin(), &fatal_error);
+        if (fatal_error) {
+            return VBMetaVerifyResult::kError;
+        }
+        for (auto& chain : chain_partitions) {
+            auto sub_ret = LoadAndVerifyVbmetaImpl(
+                    chain.partition_name, ab_suffix, ab_other_suffix, chain.public_key_blob,
+                    allow_verification_error, load_chained_vbmeta, rollback_protection,
+                    device_path_constructor, true, /* is_chained_vbmeta */
+                    out_vbmeta_images);
+            if (sub_ret != VBMetaVerifyResult::kSuccess) {
+                verify_result = sub_ret;  // might be 'ERROR' or 'ERROR VERIFICATION'.
+                if (verify_result == VBMetaVerifyResult::kError) {
+                    return verify_result;  // stop here if we got an 'ERROR'.
+                }
+            }
+        }
+    }
+
+    return verify_result;
+}
+
 }  // namespace fs_mgr
 }  // namespace android
diff --git a/fs_mgr/libfs_avb/avb_util.h b/fs_mgr/libfs_avb/avb_util.h
index b81e931..babbfef 100644
--- a/fs_mgr/libfs_avb/avb_util.h
+++ b/fs_mgr/libfs_avb/avb_util.h
@@ -16,9 +16,11 @@
 
 #pragma once
 
+#include <ostream>
 #include <string>
 #include <vector>
 
+#include <fstab/fstab.h>
 #include <libavb/libavb.h>
 #include <libdm/dm.h>
 
@@ -27,6 +29,22 @@
 namespace android {
 namespace fs_mgr {
 
+enum class VBMetaVerifyResult {
+    kSuccess = 0,
+    kError = 1,
+    kErrorVerification = 2,
+};
+
+std::ostream& operator<<(std::ostream& os, VBMetaVerifyResult);
+
+struct ChainInfo {
+    std::string partition_name;
+    std::string public_key_blob;
+
+    ChainInfo(const std::string& chain_partition_name, const std::string& chain_public_key_blob)
+        : partition_name(chain_partition_name), public_key_blob(chain_public_key_blob) {}
+};
+
 // AvbHashtreeDescriptor to dm-verity table setup.
 bool GetHashtreeDescriptor(const std::string& partition_name,
                            const std::vector<VBMetaData>& vbmeta_images,
@@ -41,5 +59,37 @@
                            const std::string& salt, const std::string& root_digest,
                            bool wait_for_verity_dev);
 
+// Maps AVB partition name to a device partition name.
+std::string AvbPartitionToDevicePatition(const std::string& avb_partition_name,
+                                         const std::string& ab_suffix,
+                                         const std::string& ab_other_suffix);
+
+// AvbFooter and AvbMetaImage maninpulations.
+off64_t GetTotalSize(int fd);
+
+std::unique_ptr<AvbFooter> GetAvbFooter(int fd);
+
+std::unique_ptr<VBMetaData> VerifyVBMetaData(int fd, const std::string& partition_name,
+                                             const std::string& expected_public_key_blob,
+                                             VBMetaVerifyResult* out_verify_result);
+
+VBMetaVerifyResult VerifyVBMetaSignature(const VBMetaData& vbmeta,
+                                         const std::string& expected_public_key_blob);
+
+bool VerifyPublicKeyBlob(const uint8_t* key, size_t length, const std::string& expected_key_blob);
+
+// Detects if whether a partition contains a rollback image.
+bool RollbackDetected(const std::string& partition_name, uint64_t rollback_index);
+
+// Extracts chain partition info.
+std::vector<ChainInfo> GetChainPartitionInfo(const VBMetaData& vbmeta, bool* fatal_error);
+
+VBMetaVerifyResult LoadAndVerifyVbmetaImpl(
+        const std::string& partition_name, const std::string& ab_suffix,
+        const std::string& ab_other_suffix, const std::string& expected_public_key_blob,
+        bool allow_verification_error, bool load_chained_vbmeta, bool rollback_protection,
+        std::function<std::string(const std::string&)> device_path_constructor,
+        bool is_chained_vbmeta, std::vector<VBMetaData>* out_vbmeta_images);
+
 }  // namespace fs_mgr
 }  // namespace android
diff --git a/fs_mgr/libfs_avb/fs_avb.cpp b/fs_mgr/libfs_avb/fs_avb.cpp
index 957aa87..9f8ad53 100644
--- a/fs_mgr/libfs_avb/fs_avb.cpp
+++ b/fs_mgr/libfs_avb/fs_avb.cpp
@@ -39,6 +39,7 @@
 
 using android::base::Basename;
 using android::base::ParseUint;
+using android::base::ReadFileToString;
 using android::base::StringPrintf;
 
 namespace android {
@@ -59,6 +60,51 @@
     return std::make_pair(total_size, matched);
 }
 
+template <typename Hasher>
+std::pair<std::string, size_t> CalculateVbmetaDigest(const std::vector<VBMetaData>& vbmeta_images) {
+    std::string digest;
+    size_t total_size = 0;
+
+    Hasher hasher;
+    for (const auto& vbmeta : vbmeta_images) {
+        hasher.update(vbmeta.data(), vbmeta.size());
+        total_size += vbmeta.size();
+    }
+
+    // Converts digest bytes to a hex string.
+    digest = BytesToHex(hasher.finalize(), Hasher::DIGEST_SIZE);
+    return std::make_pair(digest, total_size);
+}
+
+// Helper functions to dump enum class AvbHandleStatus.
+const char* AvbHandleStatusToString(AvbHandleStatus status) {
+    // clang-format off
+    static const char* const name[] = {
+        "Success",
+        "Uninitialized",
+        "HashtreeDisabled",
+        "VerificationDisabled",
+        "VerificationError",
+        "Unknown",
+    };
+    // clang-format on
+
+    uint32_t index = static_cast<uint32_t>(status);
+    uint32_t unknown_index = sizeof(name) / sizeof(char*) - 1;
+    if (index >= unknown_index) {
+        index = unknown_index;
+    }
+
+    return name[index];
+}
+
+std::ostream& operator<<(std::ostream& os, AvbHandleStatus status) {
+    os << AvbHandleStatusToString(status);
+    return os;
+}
+
+// class AvbVerifier
+// -----------------
 // Reads the following values from kernel cmdline and provides the
 // VerifyVbmetaImages() to verify AvbSlotVerifyData.
 //   - androidboot.vbmeta.hash_alg
@@ -74,12 +120,6 @@
     AvbVerifier() = default;
 
   private:
-    enum HashAlgorithm {
-        kInvalid = 0,
-        kSHA256 = 1,
-        kSHA512 = 2,
-    };
-
     HashAlgorithm hash_alg_;
     uint8_t digest_[SHA512_DIGEST_LENGTH];
     size_t vbmeta_size_;
@@ -105,10 +145,10 @@
     fs_mgr_get_boot_config("vbmeta.hash_alg", &hash_alg);
     if (hash_alg == "sha256") {
         expected_digest_size = SHA256_DIGEST_LENGTH * 2;
-        avb_verifier->hash_alg_ = kSHA256;
+        avb_verifier->hash_alg_ = HashAlgorithm::kSHA256;
     } else if (hash_alg == "sha512") {
         expected_digest_size = SHA512_DIGEST_LENGTH * 2;
-        avb_verifier->hash_alg_ = kSHA512;
+        avb_verifier->hash_alg_ = HashAlgorithm::kSHA512;
     } else {
         LERROR << "Unknown hash algorithm: " << hash_alg.c_str();
         return nullptr;
@@ -140,10 +180,10 @@
     size_t total_size = 0;
     bool digest_matched = false;
 
-    if (hash_alg_ == kSHA256) {
+    if (hash_alg_ == HashAlgorithm::kSHA256) {
         std::tie(total_size, digest_matched) =
                 VerifyVbmetaDigest<SHA256Hasher>(vbmeta_images, digest_);
-    } else if (hash_alg_ == kSHA512) {
+    } else if (hash_alg_ == HashAlgorithm::kSHA512) {
         std::tie(total_size, digest_matched) =
                 VerifyVbmetaDigest<SHA512Hasher>(vbmeta_images, digest_);
     }
@@ -162,6 +202,98 @@
     return true;
 }
 
+// class AvbHandle
+// ---------------
+AvbUniquePtr AvbHandle::LoadAndVerifyVbmeta(
+        const std::string& partition_name, const std::string& ab_suffix,
+        const std::string& ab_other_suffix, const std::string& expected_public_key_path,
+        const HashAlgorithm& hash_algorithm, bool allow_verification_error,
+        bool load_chained_vbmeta, bool rollback_protection,
+        std::function<std::string(const std::string&)> custom_device_path) {
+    AvbUniquePtr avb_handle(new AvbHandle());
+    if (!avb_handle) {
+        LERROR << "Failed to allocate AvbHandle";
+        return nullptr;
+    }
+
+    std::string expected_key_blob;
+    if (!expected_public_key_path.empty()) {
+        if (access(expected_public_key_path.c_str(), F_OK) != 0) {
+            LERROR << "Expected public key path doesn't exist: " << expected_public_key_path;
+            return nullptr;
+        } else if (!ReadFileToString(expected_public_key_path, &expected_key_blob)) {
+            LERROR << "Failed to load: " << expected_public_key_path;
+            return nullptr;
+        }
+    }
+
+    auto android_by_name_symlink = [](const std::string& partition_name_with_ab) {
+        return "/dev/block/by-name/" + partition_name_with_ab;
+    };
+
+    auto device_path = custom_device_path ? custom_device_path : android_by_name_symlink;
+
+    auto verify_result = LoadAndVerifyVbmetaImpl(
+            partition_name, ab_suffix, ab_other_suffix, expected_key_blob, allow_verification_error,
+            load_chained_vbmeta, rollback_protection, device_path, false,
+            /* is_chained_vbmeta */ &avb_handle->vbmeta_images_);
+    switch (verify_result) {
+        case VBMetaVerifyResult::kSuccess:
+            avb_handle->status_ = AvbHandleStatus::kSuccess;
+            break;
+        case VBMetaVerifyResult::kErrorVerification:
+            avb_handle->status_ = AvbHandleStatus::kVerificationError;
+            break;
+        default:
+            LERROR << "LoadAndVerifyVbmetaImpl failed, result: " << verify_result;
+            return nullptr;
+    }
+
+    // Sets the MAJOR.MINOR for init to set it into "ro.boot.avb_version".
+    avb_handle->avb_version_ = StringPrintf("%d.%d", AVB_VERSION_MAJOR, AVB_VERSION_MINOR);
+
+    // Checks any disabled flag is set.
+    std::unique_ptr<AvbVBMetaImageHeader> vbmeta_header =
+            avb_handle->vbmeta_images_[0].GetVBMetaHeader();
+    bool verification_disabled = ((AvbVBMetaImageFlags)vbmeta_header->flags &
+                                  AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED);
+    bool hashtree_disabled =
+            ((AvbVBMetaImageFlags)vbmeta_header->flags & AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED);
+    if (verification_disabled) {
+        avb_handle->status_ = AvbHandleStatus::kVerificationDisabled;
+    } else if (hashtree_disabled) {
+        avb_handle->status_ = AvbHandleStatus::kHashtreeDisabled;
+    }
+
+    // Calculates the summary info for all vbmeta_images_;
+    std::string digest;
+    size_t total_size;
+    if (hash_algorithm == HashAlgorithm::kSHA256) {
+        std::tie(digest, total_size) =
+                CalculateVbmetaDigest<SHA256Hasher>(avb_handle->vbmeta_images_);
+    } else if (hash_algorithm == HashAlgorithm::kSHA512) {
+        std::tie(digest, total_size) =
+                CalculateVbmetaDigest<SHA512Hasher>(avb_handle->vbmeta_images_);
+    } else {
+        LERROR << "Invalid hash algorithm";
+        return nullptr;
+    }
+    avb_handle->vbmeta_info_ = VBMetaInfo(digest, hash_algorithm, total_size);
+
+    LINFO << "Returning avb_handle with status: " << avb_handle->status_;
+    return avb_handle;
+}
+
+AvbUniquePtr AvbHandle::LoadAndVerifyVbmeta() {
+    // Loads inline vbmeta images, starting from /vbmeta.
+    return LoadAndVerifyVbmeta("vbmeta", fs_mgr_get_slot_suffix(), fs_mgr_get_other_slot_suffix(),
+                               {} /* expected_public_key, already checked by bootloader */,
+                               HashAlgorithm::kSHA256,
+                               IsDeviceUnlocked(), /* allow_verification_error */
+                               true,               /* load_chained_vbmeta */
+                               false, /* rollback_protection, already checked by bootloader */
+                               nullptr /* custom_device_path */);
+}
 
 AvbUniquePtr AvbHandle::Open() {
     bool is_device_unlocked = IsDeviceUnlocked();
@@ -192,14 +324,14 @@
     //     for more details.
     switch (verify_result) {
         case AVB_SLOT_VERIFY_RESULT_OK:
-            avb_handle->status_ = kAvbHandleSuccess;
+            avb_handle->status_ = AvbHandleStatus::kSuccess;
             break;
         case AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION:
             if (!is_device_unlocked) {
                 LERROR << "ERROR_VERIFICATION isn't allowed when the device is LOCKED";
                 return nullptr;
             }
-            avb_handle->status_ = kAvbHandleVerificationError;
+            avb_handle->status_ = AvbHandleStatus::kVerificationError;
             break;
         default:
             LERROR << "avb_slot_verify failed, result: " << verify_result;
@@ -220,7 +352,7 @@
                                   AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED);
 
     if (verification_disabled) {
-        avb_handle->status_ = kAvbHandleVerificationDisabled;
+        avb_handle->status_ = AvbHandleStatus::kVerificationDisabled;
     } else {
         // Verifies vbmeta structs against the digest passed from bootloader in kernel cmdline.
         std::unique_ptr<AvbVerifier> avb_verifier = AvbVerifier::Create();
@@ -237,7 +369,7 @@
         bool hashtree_disabled = ((AvbVBMetaImageFlags)vbmeta_header.flags &
                                   AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED);
         if (hashtree_disabled) {
-            avb_handle->status_ = kAvbHandleHashtreeDisabled;
+            avb_handle->status_ = AvbHandleStatus::kHashtreeDisabled;
         }
     }
 
@@ -246,11 +378,12 @@
 }
 
 AvbHashtreeResult AvbHandle::SetUpAvbHashtree(FstabEntry* fstab_entry, bool wait_for_verity_dev) {
-    if (!fstab_entry || status_ == kAvbHandleUninitialized || vbmeta_images_.size() < 1) {
+    if (!fstab_entry || status_ == AvbHandleStatus::kUninitialized || vbmeta_images_.size() < 1) {
         return AvbHashtreeResult::kFail;
     }
 
-    if (status_ == kAvbHandleHashtreeDisabled || status_ == kAvbHandleVerificationDisabled) {
+    if (status_ == AvbHandleStatus::kHashtreeDisabled ||
+        status_ == AvbHandleStatus::kVerificationDisabled) {
         LINFO << "AVB HASHTREE disabled on: " << fstab_entry->mount_point;
         return AvbHashtreeResult::kDisabled;
     }
diff --git a/fs_mgr/libfs_avb/include/fs_avb/fs_avb.h b/fs_mgr/libfs_avb/include/fs_avb/fs_avb.h
index eca6984..7af3c7e 100644
--- a/fs_mgr/libfs_avb/include/fs_avb/fs_avb.h
+++ b/fs_mgr/libfs_avb/include/fs_avb/fs_avb.h
@@ -16,6 +16,7 @@
 
 #pragma once
 
+#include <functional>
 #include <memory>
 #include <string>
 #include <vector>
@@ -32,23 +33,56 @@
     kDisabled,
 };
 
+enum class HashAlgorithm {
+    kInvalid = 0,
+    kSHA256 = 1,
+    kSHA512 = 2,
+};
+
+enum class AvbHandleStatus {
+    kSuccess = 0,
+    kUninitialized = 1,
+    kHashtreeDisabled = 2,
+    kVerificationDisabled = 3,
+    kVerificationError = 4,
+};
+
+struct VBMetaInfo {
+    std::string digest;
+    HashAlgorithm hash_algorithm;
+    size_t total_size;
+
+    VBMetaInfo() {}
+
+    VBMetaInfo(std::string digest_value, HashAlgorithm algorithm, size_t size)
+        : digest(std::move(digest_value)), hash_algorithm(algorithm), total_size(size) {}
+};
+
 class VBMetaData {
   public:
     // Constructors
     VBMetaData() : vbmeta_ptr_(nullptr), vbmeta_size_(0){};
 
-    VBMetaData(const uint8_t* data, size_t size)
-        : vbmeta_ptr_(new (std::nothrow) uint8_t[size]), vbmeta_size_(size) {
+    VBMetaData(const uint8_t* data, size_t size, const std::string& partition_name)
+        : vbmeta_ptr_(new (std::nothrow) uint8_t[size]),
+          vbmeta_size_(size),
+          partition_name_(partition_name) {
         // The ownership of data is NOT transferred, i.e., the caller still
         // needs to release the memory as we make a copy here.
         memcpy(vbmeta_ptr_.get(), data, size * sizeof(uint8_t));
     }
 
-    explicit VBMetaData(size_t size)
-        : vbmeta_ptr_(new (std::nothrow) uint8_t[size]), vbmeta_size_(size) {}
+    explicit VBMetaData(size_t size, const std::string& partition_name)
+        : vbmeta_ptr_(new (std::nothrow) uint8_t[size]),
+          vbmeta_size_(size),
+          partition_name_(partition_name) {}
+
+    // Extracts vbmeta header from the vbmeta buffer, set update_vbmeta_size to
+    // true to update vbmeta_size_ to the actual size with valid content.
+    std::unique_ptr<AvbVBMetaImageHeader> GetVBMetaHeader(bool update_vbmeta_size = false);
 
     // Get methods for each data member.
-    const std::string& device_path() const { return device_path_; }
+    const std::string& partition() const { return partition_name_; }
     uint8_t* data() const { return vbmeta_ptr_.get(); }
     const size_t& size() const { return vbmeta_size_; }
 
@@ -56,9 +90,9 @@
     static const size_t kMaxVBMetaSize = 64 * 1024;
 
   private:
-    std::string device_path_;
     std::unique_ptr<uint8_t[]> vbmeta_ptr_;
     size_t vbmeta_size_;
+    std::string partition_name_;
 };
 
 class FsManagerAvbOps;
@@ -71,7 +105,7 @@
 // descriptors to load verity table into kernel through ioctl.
 class AvbHandle {
   public:
-    // The factory method to return a AvbUniquePtr that holds
+    // The factory methods to return a AvbUniquePtr that holds
     // the verified AVB (external/avb) metadata of all verified partitions
     // in vbmeta_images_.
     //
@@ -79,31 +113,40 @@
     //   - androidboot.vbmeta.{hash_alg, size, digest}.
     //
     // A typical usage will be:
-    //   - AvbUniquePtr handle = AvbHandle::Open();
+    //   - AvbUniquePtr handle = AvbHandle::Open(); or
+    //   - AvbUniquePtr handle = AvbHandle::LoadAndVerifyVbmeta();
     //
     // Possible return values:
     //   - nullptr: any error when reading and verifying the metadata,
     //     e.g., I/O error, digest value mismatch, size mismatch, etc.
     //
-    //   - a valid unique_ptr with status kAvbHandleHashtreeDisabled:
+    //   - a valid unique_ptr with status AvbHandleStatus::HashtreeDisabled:
     //     to support the existing 'adb disable-verity' feature in Android.
     //     It's very helpful for developers to make the filesystem writable to
     //     allow replacing binaries on the device.
     //
-    //   - a valid unique_ptr with status kAvbHandleVerificationDisabled:
+    //   - a valid unique_ptr with status AvbHandleStatus::VerificationDisabled:
     //     to support 'avbctl disable-verification': only the top-level
     //     vbmeta is read, vbmeta structs in other partitions are not processed.
     //     It's needed to bypass AVB when using the generic system.img to run
     //     VTS for project Treble.
     //
-    //   - a valid unique_ptr with status kAvbHandleVerificationError:
+    //   - a valid unique_ptr with status AvbHandleStatus::VerificationError:
     //     there is verification error when libavb loads vbmeta from each
     //     partition. This is only allowed when the device is unlocked.
     //
-    //   - a valid unique_ptr with status kAvbHandleSuccess: the metadata
+    //   - a valid unique_ptr with status AvbHandleStatus::Success: the metadata
     //     is verified and can be trusted.
     //
-    static AvbUniquePtr Open();
+    // TODO(bowgotsai): remove Open() and switch to LoadAndVerifyVbmeta().
+    static AvbUniquePtr Open();                 // loads inline vbmeta, via libavb.
+    static AvbUniquePtr LoadAndVerifyVbmeta();  // loads inline vbmeta.
+    static AvbUniquePtr LoadAndVerifyVbmeta(    // loads offline vbmeta.
+            const std::string& partition_name, const std::string& ab_suffix,
+            const std::string& ab_other_suffix, const std::string& expected_public_key,
+            const HashAlgorithm& hash_algorithm, bool allow_verification_error,
+            bool load_chained_vbmeta, bool rollback_protection,
+            std::function<std::string(const std::string&)> custom_device_path = nullptr);
 
     // Sets up dm-verity on the given fstab entry.
     // The 'wait_for_verity_dev' parameter makes this function wait for the
@@ -118,6 +161,8 @@
     AvbHashtreeResult SetUpAvbHashtree(FstabEntry* fstab_entry, bool wait_for_verity_dev);
 
     const std::string& avb_version() const { return avb_version_; }
+    const VBMetaInfo& vbmeta_info() const { return vbmeta_info_; }
+    AvbHandleStatus status() const { return status_; }
 
     AvbHandle(const AvbHandle&) = delete;             // no copy
     AvbHandle& operator=(const AvbHandle&) = delete;  // no assignment
@@ -126,17 +171,10 @@
     AvbHandle& operator=(AvbHandle&&) noexcept = delete;  // no move assignment
 
   private:
-    enum AvbHandleStatus {
-        kAvbHandleSuccess = 0,
-        kAvbHandleUninitialized,
-        kAvbHandleHashtreeDisabled,
-        kAvbHandleVerificationDisabled,
-        kAvbHandleVerificationError,
-    };
-
-    AvbHandle() : status_(kAvbHandleUninitialized) {}
+    AvbHandle() : status_(AvbHandleStatus::kUninitialized) {}
 
     std::vector<VBMetaData> vbmeta_images_;
+    VBMetaInfo vbmeta_info_;  // A summary info for vbmeta_images_.
     AvbHandleStatus status_;
     std::string avb_version_;
 };
diff --git a/fs_mgr/libfs_avb/tests/avb_util_test.cpp b/fs_mgr/libfs_avb/tests/avb_util_test.cpp
new file mode 100644
index 0000000..26b3294
--- /dev/null
+++ b/fs_mgr/libfs_avb/tests/avb_util_test.cpp
@@ -0,0 +1,1088 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * 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
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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.
+ */
+
+#include <android-base/unique_fd.h>
+#include <base/files/file_util.h>
+#include <base/rand_util.h>
+#include <base/strings/string_util.h>
+
+#include "avb_util.h"
+#include "fs_avb_test_util.h"
+
+// Target classes or functions to test:
+using android::fs_mgr::AvbPartitionToDevicePatition;
+using android::fs_mgr::GetAvbFooter;
+using android::fs_mgr::GetChainPartitionInfo;
+using android::fs_mgr::GetTotalSize;
+using android::fs_mgr::LoadAndVerifyVbmetaImpl;
+using android::fs_mgr::VBMetaData;
+using android::fs_mgr::VBMetaVerifyResult;
+using android::fs_mgr::VerifyPublicKeyBlob;
+using android::fs_mgr::VerifyVBMetaData;
+using android::fs_mgr::VerifyVBMetaSignature;
+
+namespace fs_avb_host_test {
+
+class AvbUtilTest : public BaseFsAvbTest {
+  public:
+    AvbUtilTest(){};
+
+  protected:
+    ~AvbUtilTest(){};
+    // Helper function for VerifyVBMetaSignature test. Modifies vbmeta.data()
+    // in a number of places at |offset| of size |length| and checks that
+    // VerifyVBMetaSignature() returns |expected_result|.
+    bool TestVBMetaModification(VBMetaVerifyResult expected_result, const VBMetaData& vbmeta,
+                                size_t offset, size_t length);
+    // Modifies a random bit for a file, in the range of [offset, offset + length - 1].
+    void ModifyFile(const base::FilePath& file_path, size_t offset, ssize_t length);
+
+    // Loads the content of avb_image_path and comparies it with the content of vbmeta.
+    bool CompareVBMeta(const base::FilePath& avb_image_path, const VBMetaData& expected_vbmeta);
+};
+
+TEST_F(AvbUtilTest, AvbPartitionToDevicePatition) {
+    EXPECT_EQ("system", AvbPartitionToDevicePatition("system", "", ""));
+    EXPECT_EQ("system", AvbPartitionToDevicePatition("system", "", "_b"));
+
+    EXPECT_EQ("system_a", AvbPartitionToDevicePatition("system", "_a", ""));
+    EXPECT_EQ("system_a", AvbPartitionToDevicePatition("system", "_a", "_b"));
+
+    EXPECT_EQ("system_b", AvbPartitionToDevicePatition("system_other", "", "_b"));
+    EXPECT_EQ("system_b", AvbPartitionToDevicePatition("system_other", "_a", "_b"));
+}
+
+TEST_F(AvbUtilTest, GetFdTotalSize) {
+    // Generates a raw test.img via BaseFsAvbTest.
+    const size_t image_size = 5 * 1024 * 1024;
+    base::FilePath image_path = GenerateImage("test.img", image_size);
+
+    // Checks file size is as expected via base::GetFileSize().
+    int64_t file_size;
+    ASSERT_TRUE(base::GetFileSize(image_path, &file_size));
+    EXPECT_EQ(image_size, file_size);
+
+    // Checks file size is expected via libfs_avb internal utils.
+    auto fd = OpenUniqueReadFd(image_path);
+    EXPECT_EQ(image_size, GetTotalSize(fd));
+}
+
+TEST_F(AvbUtilTest, GetFdTotalSizeWithOffset) {
+    // Generates a raw test.img via BaseFsAvbTest.
+    const size_t image_size = 10 * 1024 * 1024;
+    base::FilePath image_path = GenerateImage("test.img", image_size);
+
+    // Checks file size is expected even with a non-zero offset at the beginning.
+    auto fd = OpenUniqueReadFd(image_path);
+    off_t initial_offset = 2019;
+    EXPECT_EQ(initial_offset, lseek(fd, initial_offset, SEEK_SET));
+    EXPECT_EQ(image_size, GetTotalSize(fd));            // checks that total size is still returned.
+    EXPECT_EQ(initial_offset, lseek(fd, 0, SEEK_CUR));  // checks original offset is restored.
+}
+
+TEST_F(AvbUtilTest, GetAvbFooter) {
+    // Generates a raw system.img
+    const size_t image_size = 10 * 1024 * 1024;
+    const size_t partition_size = 15 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system.img", image_size);
+    EXPECT_NE(0U, system_path.value().size());
+
+    // Checks image size is as expected.
+    int64_t file_size;
+    ASSERT_TRUE(base::GetFileSize(system_path, &file_size));
+    EXPECT_EQ(image_size, file_size);
+
+    // Appends AVB Hashtree Footer.
+    AddAvbFooter(system_path, "hashtree", "system", partition_size, "SHA512_RSA8192", 20,
+                 data_dir_.Append("testkey_rsa8192.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Checks partition size is as expected, after adding footer.
+    ASSERT_TRUE(base::GetFileSize(system_path, &file_size));
+    EXPECT_EQ(partition_size, file_size);
+
+    // Checks avb footer and avb vbmeta.
+    EXPECT_EQ(
+            "Footer version:           1.0\n"
+            "Image size:               15728640 bytes\n"
+            "Original image size:      10485760 bytes\n"
+            "VBMeta offset:            10661888\n"
+            "VBMeta size:              3648 bytes\n"
+            "--\n"
+            "Minimum libavb version:   1.0\n"
+            "Header Block:             256 bytes\n"
+            "Authentication Block:     1088 bytes\n"
+            "Auxiliary Block:          2304 bytes\n"
+            "Algorithm:                SHA512_RSA8192\n"
+            "Rollback Index:           20\n"
+            "Flags:                    0\n"
+            "Release String:           'unit test'\n"
+            "Descriptors:\n"
+            "    Hashtree descriptor:\n"
+            "      Version of dm-verity:  1\n"
+            "      Image Size:            10485760 bytes\n"
+            "      Tree Offset:           10485760\n"
+            "      Tree Size:             86016 bytes\n"
+            "      Data Block Size:       4096 bytes\n"
+            "      Hash Block Size:       4096 bytes\n"
+            "      FEC num roots:         2\n"
+            "      FEC offset:            10571776\n"
+            "      FEC size:              90112 bytes\n"
+            "      Hash Algorithm:        sha1\n"
+            "      Partition Name:        system\n"
+            "      Salt:                  d00df00d\n"
+            "      Root Digest:           a3d5dd307341393d85de356c384ff543ec1ed81b\n"
+            "      Flags:                 0\n",
+            InfoImage(system_path));
+
+    // Checks each field from GetAvbFooter(fd).
+    auto fd = OpenUniqueReadFd(system_path);
+    auto footer = GetAvbFooter(fd);
+    EXPECT_NE(nullptr, footer);
+    EXPECT_EQ(10485760, footer->original_image_size);
+    EXPECT_EQ(10661888, footer->vbmeta_offset);
+    EXPECT_EQ(3648, footer->vbmeta_size);
+}
+
+TEST_F(AvbUtilTest, GetAvbFooterErrorVerification) {
+    // Generates a raw system.img
+    const size_t image_size = 5 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system.img", image_size);
+
+    // Checks each field from GetAvbFooter(fd).
+    auto fd = OpenUniqueReadFd(system_path);
+    auto footer = GetAvbFooter(fd);
+    EXPECT_EQ(nullptr, footer);
+}
+
+TEST_F(AvbUtilTest, GetAvbFooterInsufficientSize) {
+    // Generates a raw system.img
+    const size_t image_size = AVB_FOOTER_SIZE - 10;
+    base::FilePath system_path = GenerateImage("system.img", image_size);
+
+    // Checks each field from GetAvbFooter(fd).
+    auto fd = OpenUniqueReadFd(system_path);
+    auto footer = GetAvbFooter(fd);
+    EXPECT_EQ(nullptr, footer);
+}
+
+TEST_F(AvbUtilTest, GetVBMetaHeader) {
+    // Generates a raw boot.img
+    const size_t image_size = 5 * 1024 * 1024;
+    const size_t partition_size = 10 * 1024 * 1024;
+    base::FilePath boot_path = GenerateImage("boot.img", image_size);
+    // Appends AVB Hash Footer.
+    AddAvbFooter(boot_path, "hash", "boot", partition_size, "SHA256_RSA4096", 10,
+                 data_dir_.Append("testkey_rsa4096.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+    // Extracts boot vbmeta from boot.img into boot-vbmeta.img.
+    base::FilePath boot_vbmeta = ExtractVBMetaImage(boot_path, "boot-vbmeta.img");
+    EXPECT_EQ(
+            "Minimum libavb version:   1.0\n"
+            "Header Block:             256 bytes\n"
+            "Authentication Block:     576 bytes\n"
+            "Auxiliary Block:          1216 bytes\n"
+            "Algorithm:                SHA256_RSA4096\n"
+            "Rollback Index:           10\n"
+            "Flags:                    0\n"
+            "Release String:           'unit test'\n"
+            "Descriptors:\n"
+            "    Hash descriptor:\n"
+            "      Image Size:            5242880 bytes\n"
+            "      Hash Algorithm:        sha256\n"
+            "      Partition Name:        boot\n"
+            "      Salt:                  d00df00d\n"
+            "      Digest:                "
+            "222dd01e98284a1fcd7781f85d1392e43a530511a64eff96db197db90ebc4df1\n"
+            "      Flags:                 0\n",
+            InfoImage("boot-vbmeta.img"));
+
+    // Creates a VBMetaData with the content from boot-vbmeta.img.
+    std::string content;
+    EXPECT_TRUE(base::ReadFileToString(boot_vbmeta, &content));
+    VBMetaData vbmeta((uint8_t*)content.data(), content.size(), "boot-vbmeta");
+    EXPECT_EQ(content.size(), vbmeta.size());
+
+    // Checks each field returned from GetVBMetaHeader().
+    auto vbmeta_header = vbmeta.GetVBMetaHeader(false /* update_vbmeta_size */);
+    EXPECT_NE(nullptr, vbmeta_header);
+    EXPECT_EQ(576, vbmeta_header->authentication_data_block_size);
+    EXPECT_EQ(1216, vbmeta_header->auxiliary_data_block_size);
+    EXPECT_EQ(AVB_ALGORITHM_TYPE_SHA256_RSA4096, vbmeta_header->algorithm_type);
+    EXPECT_EQ(0, vbmeta_header->hash_offset);
+    EXPECT_EQ(32, vbmeta_header->hash_size);
+    EXPECT_EQ(32, vbmeta_header->signature_offset);
+    EXPECT_EQ(512, vbmeta_header->signature_size);
+    EXPECT_EQ(176, vbmeta_header->public_key_offset);
+    EXPECT_EQ(1032, vbmeta_header->public_key_size);
+    EXPECT_EQ(0, vbmeta_header->descriptors_offset);
+    EXPECT_EQ(176, vbmeta_header->descriptors_size);
+    EXPECT_EQ(10, vbmeta_header->rollback_index);
+    EXPECT_EQ(0, vbmeta_header->flags);
+    EXPECT_EQ("unit test", std::string((const char*)vbmeta_header->release_string));
+
+    // Appends some garbage to the end of the vbmeta buffer, checks it still can work.
+    std::string padding(2020, 'A');  // Generate a padding with length 2020.
+    std::string content_padding = content + padding;
+    VBMetaData vbmeta_padding((const uint8_t*)content_padding.data(), content_padding.size(),
+                              "boot");
+    EXPECT_EQ(content_padding.size(), vbmeta_padding.size());
+
+    // Checks each field still can be parsed properly, even with garbage padding.
+    vbmeta_header = vbmeta_padding.GetVBMetaHeader(false /* update_vbmeta_size */);
+    EXPECT_NE(nullptr, vbmeta_header);
+    EXPECT_EQ(576, vbmeta_header->authentication_data_block_size);
+    EXPECT_EQ(1216, vbmeta_header->auxiliary_data_block_size);
+    EXPECT_EQ(AVB_ALGORITHM_TYPE_SHA256_RSA4096, vbmeta_header->algorithm_type);
+    EXPECT_EQ(0, vbmeta_header->hash_offset);
+    EXPECT_EQ(32, vbmeta_header->hash_size);
+    EXPECT_EQ(32, vbmeta_header->signature_offset);
+    EXPECT_EQ(512, vbmeta_header->signature_size);
+    EXPECT_EQ(176, vbmeta_header->public_key_offset);
+    EXPECT_EQ(1032, vbmeta_header->public_key_size);
+    EXPECT_EQ(0, vbmeta_header->descriptors_offset);
+    EXPECT_EQ(176, vbmeta_header->descriptors_size);
+    EXPECT_EQ(10, vbmeta_header->rollback_index);
+    EXPECT_EQ(0, vbmeta_header->flags);
+    EXPECT_EQ("unit test", std::string((const char*)vbmeta_header->release_string));
+
+    // Checks vbmeta size is updated to the actual size without padding.
+    vbmeta_header = vbmeta_padding.GetVBMetaHeader(true /* update_vbmeta_size */);
+    EXPECT_EQ(content_padding.size() - padding.size(), vbmeta_padding.size());
+}
+
+TEST_F(AvbUtilTest, VerifyPublicKeyBlob) {
+    // Generates a raw key.bin
+    const size_t key_size = 2048;
+    base::FilePath key_path = GenerateImage("key.bin", key_size);
+
+    uint8_t key_data[key_size];
+    EXPECT_EQ(key_size, base::ReadFile(key_path, (char*)key_data, key_size));
+
+    std::string expected_key_blob;
+    EXPECT_TRUE(base::ReadFileToString(key_path, &expected_key_blob));
+    EXPECT_TRUE(VerifyPublicKeyBlob(key_data, key_size, expected_key_blob));
+
+    key_data[10] ^= 0x80;  // toggles a bit and expects a failure
+    EXPECT_FALSE(VerifyPublicKeyBlob(key_data, key_size, expected_key_blob));
+    key_data[10] ^= 0x80;  // toggles the bit again, should pass
+    EXPECT_TRUE(VerifyPublicKeyBlob(key_data, key_size, expected_key_blob));
+}
+
+TEST_F(AvbUtilTest, VerifyEmptyPublicKeyBlob) {
+    // Generates a raw key.bin
+    const size_t key_size = 2048;
+    base::FilePath key_path = GenerateImage("key.bin", key_size);
+
+    uint8_t key_data[key_size];
+    EXPECT_EQ(key_size, base::ReadFile(key_path, (char*)key_data, key_size));
+
+    std::string expected_key_blob = "";  // empty means no expectation, thus return true.
+    EXPECT_TRUE(VerifyPublicKeyBlob(key_data, key_size, expected_key_blob));
+}
+
+TEST_F(AvbUtilTest, VerifyVBMetaSignature) {
+    const size_t image_size = 10 * 1024 * 1024;
+    const size_t partition_size = 15 * 1024 * 1024;
+    auto signing_key = data_dir_.Append("testkey_rsa4096.pem");
+    auto vbmeta = GenerateImageAndExtractVBMetaData("system", image_size, partition_size,
+                                                    "hashtree", signing_key, "SHA256_RSA4096",
+                                                    10 /* rollback_index */);
+
+    auto expected_public_key = ExtractPublicKeyAvbBlob(signing_key);
+    EXPECT_EQ(VBMetaVerifyResult::kSuccess, VerifyVBMetaSignature(vbmeta, expected_public_key));
+
+    // Converts the expected key into an 'unexpected' key.
+    expected_public_key[10] ^= 0x80;
+    EXPECT_EQ(VBMetaVerifyResult::kErrorVerification,
+              VerifyVBMetaSignature(vbmeta, expected_public_key));
+}
+
+bool AvbUtilTest::TestVBMetaModification(VBMetaVerifyResult expected_result,
+                                         const VBMetaData& vbmeta, size_t offset, size_t length) {
+    uint8_t* d = reinterpret_cast<uint8_t*>(vbmeta.data());
+    const int kNumCheckIntervals = 8;
+
+    // Tests |kNumCheckIntervals| modifications in the start, middle, and
+    // end of the given sub-array at offset with size.
+    for (int n = 0; n <= kNumCheckIntervals; n++) {
+        size_t o = std::min(length * n / kNumCheckIntervals, length - 1) + offset;
+        d[o] ^= 0x80;
+        VBMetaVerifyResult result = VerifyVBMetaSignature(vbmeta, "" /* expected_public_key */);
+        d[o] ^= 0x80;
+        if (result != expected_result) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+TEST_F(AvbUtilTest, VerifyVBMetaSignatureWithModification) {
+    const size_t image_size = 10 * 1024 * 1024;
+    const size_t partition_size = 15 * 1024 * 1024;
+    auto signing_key = data_dir_.Append("testkey_rsa4096.pem");
+    auto vbmeta = GenerateImageAndExtractVBMetaData("system", image_size, partition_size,
+                                                    "hashtree", signing_key, "SHA256_RSA4096",
+                                                    10 /* rollback_index */);
+
+    auto header = vbmeta.GetVBMetaHeader(true /* update_vbmeta_size */);
+    size_t header_block_offset = 0;
+    size_t authentication_block_offset = header_block_offset + sizeof(AvbVBMetaImageHeader);
+    size_t auxiliary_block_offset =
+            authentication_block_offset + header->authentication_data_block_size;
+
+    // Should detect modifications in the auxiliary data block.
+    EXPECT_TRUE(TestVBMetaModification(VBMetaVerifyResult::kErrorVerification, vbmeta,
+                                       auxiliary_block_offset, header->auxiliary_data_block_size));
+
+    // Sholud detect modifications in the hash part of authentication data block.
+    EXPECT_TRUE(TestVBMetaModification(VBMetaVerifyResult::kErrorVerification, vbmeta,
+                                       authentication_block_offset + header->hash_offset,
+                                       header->hash_size));
+
+    // Sholud detect modifications in the signature part of authentication data block.
+    EXPECT_TRUE(TestVBMetaModification(VBMetaVerifyResult::kErrorVerification, vbmeta,
+                                       authentication_block_offset + header->signature_offset,
+                                       header->signature_size));
+}
+
+TEST_F(AvbUtilTest, VerifyVBMetaSignatureNotSigned) {
+    const size_t image_size = 10 * 1024 * 1024;
+    const size_t partition_size = 15 * 1024 * 1024;
+    auto vbmeta = GenerateImageAndExtractVBMetaData(
+            "system", image_size, partition_size, "hashtree", {} /* avb_signing_key */,
+            "" /* avb_algorithm */, 10 /* rollback_index */);
+
+    EXPECT_EQ(VBMetaVerifyResult::kErrorVerification, VerifyVBMetaSignature(vbmeta, ""));
+}
+
+TEST_F(AvbUtilTest, VerifyVBMetaSignatureInvalidVBMeta) {
+    const size_t buffer_size = 5 * 1024 * 1024;
+    std::vector<uint8_t> vbmeta_buffer(buffer_size);
+    for (size_t n = 0; n < buffer_size; n++) {
+        vbmeta_buffer[n] = uint8_t(n);
+    }
+
+    VBMetaData invalid_vbmeta((const uint8_t*)vbmeta_buffer.data(), vbmeta_buffer.size(),
+                              "invalid_vbmeta");
+    EXPECT_EQ(VBMetaVerifyResult::kError, VerifyVBMetaSignature(invalid_vbmeta, ""));
+}
+
+bool AvbUtilTest::CompareVBMeta(const base::FilePath& avb_image_path,
+                                const VBMetaData& expected_vbmeta) {
+    if (!base::PathExists(avb_image_path)) return false;
+
+    std::string image_file_name = avb_image_path.RemoveExtension().BaseName().value();
+
+    base::FilePath extracted_vbmeta_path;
+    if (base::StartsWith(image_file_name, "vbmeta", base::CompareCase::INSENSITIVE_ASCII)) {
+        extracted_vbmeta_path = avb_image_path;  // no need to extract if it's a vbmeta image.
+    } else {
+        extracted_vbmeta_path = ExtractVBMetaImage(avb_image_path, image_file_name + "-vbmeta.img");
+    }
+
+    // Gets file size of the vbmeta image.
+    int64_t extracted_vbmeta_size;
+    EXPECT_TRUE(base::GetFileSize(extracted_vbmeta_path, &extracted_vbmeta_size));
+
+    // Reads the vbmeta into a vector.
+    std::vector<uint8_t> extracted_vbmeta_content(extracted_vbmeta_size);
+    EXPECT_TRUE(base::ReadFile(extracted_vbmeta_path,
+                               reinterpret_cast<char*>(extracted_vbmeta_content.data()),
+                               extracted_vbmeta_size));
+
+    // Compares extracted_vbmeta_content with the expected_vbmeta.
+    EXPECT_EQ(expected_vbmeta.size(), extracted_vbmeta_size);
+    return memcmp(reinterpret_cast<void*>(extracted_vbmeta_content.data()),
+                  reinterpret_cast<void*>(expected_vbmeta.data()), extracted_vbmeta_size) == 0;
+}
+
+TEST_F(AvbUtilTest, VerifyVBMetaDataWithoutFooter) {
+    // Generates chain partition descriptors.
+    base::FilePath rsa2048_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa2048.pem"));
+    base::FilePath rsa4096_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa4096.pem"));
+
+    // Makes a vbmeta image includeing 'boot' and 'system' chained descriptors.
+    auto vbmeta_path = GenerateVBMetaImage("vbmeta.img", "SHA256_RSA8192", 0,
+                                           data_dir_.Append("testkey_rsa8192.pem"),
+                                           {}, /* include_descriptor_image_paths */
+                                           {{"boot", 1, rsa2048_public_key}, /* chain_partitions */
+                                            {"system", 2, rsa4096_public_key}},
+                                           "--internal_release_string \"unit test\"");
+    EXPECT_EQ(
+            "Minimum libavb version:   1.0\n"
+            "Header Block:             256 bytes\n"
+            "Authentication Block:     1088 bytes\n"
+            "Auxiliary Block:          3840 bytes\n"
+            "Algorithm:                SHA256_RSA8192\n"
+            "Rollback Index:           0\n"
+            "Flags:                    0\n"
+            "Release String:           'unit test'\n"
+            "Descriptors:\n"
+            "    Chain Partition descriptor:\n"
+            "      Partition Name:          boot\n"
+            "      Rollback Index Location: 1\n"
+            "      Public key (sha1):       cdbb77177f731920bbe0a0f94f84d9038ae0617d\n"
+            "    Chain Partition descriptor:\n"
+            "      Partition Name:          system\n"
+            "      Rollback Index Location: 2\n"
+            "      Public key (sha1):       2597c218aae470a130f61162feaae70afd97f011\n",
+            InfoImage("vbmeta.img"));
+
+    android::base::unique_fd fd(open(vbmeta_path.value().c_str(), O_RDONLY | O_CLOEXEC));
+    ASSERT_TRUE(fd > 0);
+
+    VBMetaVerifyResult verify_result;
+    std::unique_ptr<VBMetaData> vbmeta =
+            VerifyVBMetaData(fd, "vbmeta", "" /*expected_public_key_blob */, &verify_result);
+    EXPECT_TRUE(vbmeta != nullptr);
+    EXPECT_EQ(VBMetaVerifyResult::kSuccess, verify_result);
+
+    // Checkes the returned vbmeta content is the same as that extracted via avbtool.
+    vbmeta->GetVBMetaHeader(true /* update_vbmeta_size */);
+    EXPECT_TRUE(CompareVBMeta(vbmeta_path, *vbmeta));
+}
+
+TEST_F(AvbUtilTest, VerifyVBMetaDataWithFooter) {
+    const size_t image_size = 10 * 1024 * 1024;
+    const size_t partition_size = 15 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system.img", image_size);
+
+    // Appends AVB Hashtree Footer.
+    AddAvbFooter(system_path, "hashtree", "system", partition_size, "SHA512_RSA8192", 20,
+                 data_dir_.Append("testkey_rsa8192.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    android::base::unique_fd fd(open(system_path.value().c_str(), O_RDONLY | O_CLOEXEC));
+    ASSERT_TRUE(fd > 0);
+
+    VBMetaVerifyResult verify_result;
+    std::unique_ptr<VBMetaData> vbmeta =
+            VerifyVBMetaData(fd, "system", "" /*expected_public_key_blob */, &verify_result);
+    EXPECT_TRUE(vbmeta != nullptr);
+    EXPECT_EQ(VBMetaVerifyResult::kSuccess, verify_result);
+
+    // Checkes the returned vbmeta content is the same as that extracted via avbtool.
+    EXPECT_TRUE(CompareVBMeta(system_path, *vbmeta));
+}
+
+// Modifies a random bit for a file, in the range of [offset, offset + length - 1].
+// Length < 0 means only resets previous modification without introducing new modification.
+void AvbUtilTest::ModifyFile(const base::FilePath& file_path, size_t offset, ssize_t length) {
+    static int last_modified_location = -1;
+    static std::string last_file_path;
+
+    int64_t file_size;
+    ASSERT_TRUE(base::GetFileSize(file_path, &file_size));
+
+    std::vector<uint8_t> file_content(file_size);
+    ASSERT_TRUE(base::ReadFile(file_path, reinterpret_cast<char*>(file_content.data()), file_size));
+
+    // Resets previous modification for consecutive calls on the same file.
+    if (last_file_path == file_path.value()) {
+        file_content[last_modified_location] ^= 0x80;
+    }
+
+    // Introduces a new modification.
+    if (length > 0) {
+        int modify_location = base::RandInt(offset, offset + length - 1);
+        file_content[modify_location] ^= 0x80;
+        last_file_path = file_path.value();
+        last_modified_location = modify_location;
+    }
+
+    ASSERT_EQ(file_size, static_cast<const size_t>(base::WriteFile(
+                                 file_path, reinterpret_cast<const char*>(file_content.data()),
+                                 file_content.size())));
+}
+
+TEST_F(AvbUtilTest, VerifyVBMetaDataError) {
+    const size_t image_size = 10 * 1024 * 1024;
+    const size_t partition_size = 15 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system.img", image_size);
+
+    // Appends AVB Hashtree Footer.
+    AddAvbFooter(system_path, "hashtree", "system", partition_size, "SHA512_RSA8192", 20,
+                 data_dir_.Append("testkey_rsa8192.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    android::base::unique_fd fd(open(system_path.value().c_str(), O_RDONLY | O_CLOEXEC));
+    ASSERT_TRUE(fd > 0);
+
+    std::unique_ptr<AvbFooter> footer = GetAvbFooter(fd);
+    EXPECT_TRUE(footer != nullptr);
+
+    VBMetaVerifyResult verify_result;
+    std::unique_ptr<VBMetaData> vbmeta =
+            VerifyVBMetaData(fd, "system", "" /*expected_public_key_blob */, &verify_result);
+    EXPECT_NE(nullptr, vbmeta);
+    EXPECT_EQ(VBMetaVerifyResult::kSuccess, verify_result);
+
+    // Modifies hash and signature, checks there is verification error.
+    auto header = vbmeta->GetVBMetaHeader(true /* update_vbmeta_size */);
+    size_t header_block_offset = 0;
+    size_t authentication_block_offset = header_block_offset + sizeof(AvbVBMetaImageHeader);
+
+    // Modifies the hash.
+    ModifyFile(system_path,
+               footer->vbmeta_offset + authentication_block_offset + header->hash_offset,
+               header->hash_size);
+    android::base::unique_fd hash_modified_fd(
+            open(system_path.value().c_str(), O_RDONLY | O_CLOEXEC));
+    ASSERT_TRUE(hash_modified_fd > 0);
+    // Should return ErrorVerification.
+    vbmeta = VerifyVBMetaData(hash_modified_fd, "system", "" /*expected_public_key_blob */,
+                              &verify_result);
+    EXPECT_NE(nullptr, vbmeta);
+    EXPECT_TRUE(CompareVBMeta(system_path, *vbmeta));
+    EXPECT_EQ(VBMetaVerifyResult::kErrorVerification, verify_result);
+
+    // Modifies the auxiliary data block.
+    size_t auxiliary_block_offset =
+            authentication_block_offset + header->authentication_data_block_size;
+    ModifyFile(system_path, footer->vbmeta_offset + auxiliary_block_offset,
+               header->auxiliary_data_block_size);
+    android::base::unique_fd aux_modified_fd(
+            open(system_path.value().c_str(), O_RDONLY | O_CLOEXEC));
+    ASSERT_TRUE(aux_modified_fd > 0);
+    // Should return ErrorVerification.
+    vbmeta = VerifyVBMetaData(aux_modified_fd, "system", "" /*expected_public_key_blob */,
+                              &verify_result);
+    EXPECT_NE(nullptr, vbmeta);
+    EXPECT_TRUE(CompareVBMeta(system_path, *vbmeta));
+    EXPECT_EQ(VBMetaVerifyResult::kErrorVerification, verify_result);
+
+    // Resets previous modification by setting offset to -1, and checks the verification can pass.
+    ModifyFile(system_path, 0 /* offset */, -1 /* length */);
+    android::base::unique_fd ok_fd(open(system_path.value().c_str(), O_RDONLY | O_CLOEXEC));
+    ASSERT_TRUE(ok_fd > 0);
+    // Should return ResultOK..
+    vbmeta = VerifyVBMetaData(ok_fd, "system", "" /*expected_public_key_blob */, &verify_result);
+    EXPECT_NE(nullptr, vbmeta);
+    EXPECT_TRUE(CompareVBMeta(system_path, *vbmeta));
+    EXPECT_EQ(VBMetaVerifyResult::kSuccess, verify_result);
+}
+
+TEST_F(AvbUtilTest, GetChainPartitionInfo) {
+    // Generates a raw boot.img
+    const size_t boot_image_size = 5 * 1024 * 1024;
+    const size_t boot_partition_size = 10 * 1024 * 1024;
+    base::FilePath boot_path = GenerateImage("boot.img", boot_image_size);
+    // Adds AVB Hash Footer.
+    AddAvbFooter(boot_path, "hash", "boot", boot_partition_size, "SHA256_RSA2048", 10,
+                 data_dir_.Append("testkey_rsa2048.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates a raw system.img, use a smaller size to speed-up unit test.
+    const size_t system_image_size = 10 * 1024 * 1024;
+    const size_t system_partition_size = 15 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system.img", system_image_size);
+    // Adds AVB Hashtree Footer.
+    AddAvbFooter(system_path, "hashtree", "system", system_partition_size, "SHA512_RSA4096", 20,
+                 data_dir_.Append("testkey_rsa4096.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates chain partition descriptors.
+    base::FilePath rsa2048_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa2048.pem"));
+    base::FilePath rsa4096_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa4096.pem"));
+    // Makes a vbmeta_system.img including the 'system' chained descriptor.
+    GenerateVBMetaImage("vbmeta_system.img", "SHA256_RSA4096", 0,
+                        data_dir_.Append("testkey_rsa4096.pem"),
+                        {},                                  /* include_descriptor_image_paths */
+                        {{"system", 3, rsa4096_public_key}}, /* chain_partitions */
+                        "--internal_release_string \"unit test\"");
+
+    // Makes a vbmeta image includeing 'boot' and 'vbmeta_system' chained descriptors.
+    GenerateVBMetaImage("vbmeta.img", "SHA256_RSA8192", 0, data_dir_.Append("testkey_rsa8192.pem"),
+                        {},                               /* include_descriptor_image_paths */
+                        {{"boot", 1, rsa2048_public_key}, /* chain_partitions */
+                         {"vbmeta_system", 2, rsa4096_public_key}},
+                        "--internal_release_string \"unit test\"");
+
+    // Calculates the digest of all chained partitions, to ensure the chained is formed properly.
+    EXPECT_EQ("6f4bf815a651aa35ec7102a88b7906b91aef284bc5e20d0bf527c7d460da3266",
+              CalcVBMetaDigest("vbmeta.img", "sha256"));
+    // Loads the key blobs for comparison.
+    std::string expected_key_blob_2048;
+    EXPECT_TRUE(base::ReadFileToString(rsa2048_public_key, &expected_key_blob_2048));
+    std::string expected_key_blob_4096;
+    EXPECT_TRUE(base::ReadFileToString(rsa4096_public_key, &expected_key_blob_4096));
+
+    // Checks chain descriptors in vbmeta.img
+    EXPECT_EQ(
+            "Minimum libavb version:   1.0\n"
+            "Header Block:             256 bytes\n"
+            "Authentication Block:     1088 bytes\n"
+            "Auxiliary Block:          3840 bytes\n"
+            "Algorithm:                SHA256_RSA8192\n"
+            "Rollback Index:           0\n"
+            "Flags:                    0\n"
+            "Release String:           'unit test'\n"
+            "Descriptors:\n"
+            "    Chain Partition descriptor:\n"
+            "      Partition Name:          boot\n"
+            "      Rollback Index Location: 1\n"
+            "      Public key (sha1):       cdbb77177f731920bbe0a0f94f84d9038ae0617d\n"
+            "    Chain Partition descriptor:\n"
+            "      Partition Name:          vbmeta_system\n"
+            "      Rollback Index Location: 2\n"
+            "      Public key (sha1):       2597c218aae470a130f61162feaae70afd97f011\n",
+            InfoImage("vbmeta.img"));
+
+    bool fatal_error = false;
+    auto chained_descriptors = GetChainPartitionInfo(LoadVBMetaData("vbmeta.img"), &fatal_error);
+    EXPECT_EQ(2, chained_descriptors.size());  // contains 'boot' and 'vbmeta_system'.
+    EXPECT_EQ(false, fatal_error);
+
+    EXPECT_EQ("boot", chained_descriptors[0].partition_name);
+    EXPECT_EQ(expected_key_blob_2048, chained_descriptors[0].public_key_blob);
+
+    EXPECT_EQ("vbmeta_system", chained_descriptors[1].partition_name);
+    EXPECT_EQ(expected_key_blob_4096, chained_descriptors[1].public_key_blob);
+
+    // Checks chain descriptors in vbmeta_system.img
+    EXPECT_EQ(
+            "Minimum libavb version:   1.0\n"
+            "Header Block:             256 bytes\n"
+            "Authentication Block:     576 bytes\n"
+            "Auxiliary Block:          2176 bytes\n"
+            "Algorithm:                SHA256_RSA4096\n"
+            "Rollback Index:           0\n"
+            "Flags:                    0\n"
+            "Release String:           'unit test'\n"
+            "Descriptors:\n"
+            "    Chain Partition descriptor:\n"
+            "      Partition Name:          system\n"
+            "      Rollback Index Location: 3\n"
+            "      Public key (sha1):       2597c218aae470a130f61162feaae70afd97f011\n",
+            InfoImage("vbmeta_system.img"));
+
+    chained_descriptors = GetChainPartitionInfo(LoadVBMetaData("vbmeta_system.img"), &fatal_error);
+    EXPECT_EQ(1, chained_descriptors.size());  // contains 'system' only.
+    EXPECT_EQ(false, fatal_error);
+    EXPECT_EQ("system", chained_descriptors[0].partition_name);
+    EXPECT_EQ(expected_key_blob_4096, chained_descriptors[0].public_key_blob);
+}
+
+TEST_F(AvbUtilTest, GetChainPartitionInfoNone) {
+    // Generates a raw boot.img
+    const size_t boot_image_size = 5 * 1024 * 1024;
+    const size_t boot_partition_size = 10 * 1024 * 1024;
+    base::FilePath boot_path = GenerateImage("boot.img", boot_image_size);
+    // Adds AVB Hash Footer.
+    AddAvbFooter(boot_path, "hash", "boot", boot_partition_size, "SHA256_RSA4096", 10,
+                 data_dir_.Append("testkey_rsa4096.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates a raw system.img, use a smaller size to speed-up unit test.
+    const size_t system_image_size = 10 * 1024 * 1024;
+    const size_t system_partition_size = 15 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system.img", system_image_size);
+    // Adds AVB Hashtree Footer.
+    AddAvbFooter(system_path, "hashtree", "system", system_partition_size, "SHA512_RSA8192", 20,
+                 data_dir_.Append("testkey_rsa8192.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Makes a vbmeta.img including both 'boot' and 'system' descriptors.
+    GenerateVBMetaImage("vbmeta.img", "SHA256_RSA2048", 0, data_dir_.Append("testkey_rsa2048.pem"),
+                        {boot_path, system_path}, /* include_descriptor_image_paths */
+                        {},                       /* chain_partitions */
+                        "--internal_release_string \"unit test\"");
+    EXPECT_EQ("a069cbfc30c816cddf3b53f1ad53b7ca5d61a3d93845eb596bbb1b40caa1c62f",
+              CalcVBMetaDigest("vbmeta.img", "sha256"));
+
+    EXPECT_EQ(
+            "Minimum libavb version:   1.0\n"
+            "Header Block:             256 bytes\n"
+            "Authentication Block:     320 bytes\n"
+            "Auxiliary Block:          960 bytes\n"
+            "Algorithm:                SHA256_RSA2048\n"
+            "Rollback Index:           0\n"
+            "Flags:                    0\n"
+            "Release String:           'unit test'\n"
+            "Descriptors:\n"
+            "    Hash descriptor:\n"
+            "      Image Size:            5242880 bytes\n"
+            "      Hash Algorithm:        sha256\n"
+            "      Partition Name:        boot\n"
+            "      Salt:                  d00df00d\n"
+            "      Digest:                "
+            "222dd01e98284a1fcd7781f85d1392e43a530511a64eff96db197db90ebc4df1\n"
+            "      Flags:                 0\n"
+            "    Hashtree descriptor:\n"
+            "      Version of dm-verity:  1\n"
+            "      Image Size:            10485760 bytes\n"
+            "      Tree Offset:           10485760\n"
+            "      Tree Size:             86016 bytes\n"
+            "      Data Block Size:       4096 bytes\n"
+            "      Hash Block Size:       4096 bytes\n"
+            "      FEC num roots:         2\n"
+            "      FEC offset:            10571776\n"
+            "      FEC size:              90112 bytes\n"
+            "      Hash Algorithm:        sha1\n"
+            "      Partition Name:        system\n"
+            "      Salt:                  d00df00d\n"
+            "      Root Digest:           a3d5dd307341393d85de356c384ff543ec1ed81b\n"
+            "      Flags:                 0\n",
+            InfoImage("vbmeta.img"));
+
+    // Checks none of chain descriptors is found.
+    bool fatal_error = false;
+    auto chained_descriptors = GetChainPartitionInfo(LoadVBMetaData("vbmeta.img"), &fatal_error);
+    EXPECT_EQ(0, chained_descriptors.size());  // There is no chain descriptors.
+    EXPECT_EQ(false, fatal_error);
+}
+
+TEST_F(AvbUtilTest, LoadAndVerifyVbmetaImpl) {
+    // Generates a raw boot.img
+    const size_t boot_image_size = 5 * 1024 * 1024;
+    const size_t boot_partition_size = 10 * 1024 * 1024;
+    base::FilePath boot_path = GenerateImage("boot.img", boot_image_size);
+
+    // Adds AVB Hash Footer.
+    AddAvbFooter(boot_path, "hash", "boot", boot_partition_size, "SHA256_RSA2048", 10,
+                 data_dir_.Append("testkey_rsa2048.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates a raw system.img, use a smaller size to speed-up unit test.
+    const size_t system_image_size = 10 * 1024 * 1024;
+    const size_t system_partition_size = 15 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system.img", system_image_size);
+    // Adds AVB Hashtree Footer.
+    AddAvbFooter(system_path, "hashtree", "system", system_partition_size, "SHA512_RSA4096", 20,
+                 data_dir_.Append("testkey_rsa4096.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates chain partition descriptors.
+    base::FilePath rsa2048_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa2048.pem"));
+    base::FilePath rsa4096_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa4096.pem"));
+    // Makes a vbmeta_system.img including the 'system' chained descriptor.
+    auto vbmeta_system_path = GenerateVBMetaImage(
+            "vbmeta_system.img", "SHA256_RSA4096", 0, data_dir_.Append("testkey_rsa4096.pem"),
+            {},                                  /* include_descriptor_image_paths */
+            {{"system", 3, rsa4096_public_key}}, /* chain_partitions */
+            "--internal_release_string \"unit test\"");
+
+    // Makes a vbmeta image includeing 'boot' and 'vbmeta_system' chained descriptors.
+    auto vbmeta_path = GenerateVBMetaImage("vbmeta.img", "SHA256_RSA8192", 0,
+                                           data_dir_.Append("testkey_rsa8192.pem"),
+                                           {}, /* include_descriptor_image_paths */
+                                           {{"boot", 1, rsa2048_public_key}, /* chain_partitions */
+                                            {"vbmeta_system", 2, rsa4096_public_key}},
+                                           "--internal_release_string \"unit test\"");
+
+    // Calculates the digest of all chained partitions, to ensure the chained is formed properly.
+    EXPECT_EQ("6f4bf815a651aa35ec7102a88b7906b91aef284bc5e20d0bf527c7d460da3266",
+              CalcVBMetaDigest("vbmeta.img", "sha256"));
+
+    // Starts to test LoadAndVerifyVbmetaImpl.
+    std::vector<VBMetaData> vbmeta_images;
+    auto vbmeta_image_path = [this](const std::string& partition_name) {
+        return test_dir_.Append(partition_name + ".img").value();
+    };
+
+    EXPECT_EQ(VBMetaVerifyResult::kSuccess,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+                      "" /* expected_public_key_blob*/, false /* allow_verification_error */,
+                      true /* load_chained_vbmeta */, true /* rollback_protection */,
+                      vbmeta_image_path, false /* is_chained_vbmeta*/, &vbmeta_images));
+
+    EXPECT_EQ(4UL, vbmeta_images.size());  // vbmeta, boot, vbmeta_system and system
+    // Binary comparison for each vbmeta image.
+    EXPECT_TRUE(CompareVBMeta(vbmeta_path, vbmeta_images[0]));
+    EXPECT_TRUE(CompareVBMeta(boot_path, vbmeta_images[1]));
+    EXPECT_TRUE(CompareVBMeta(vbmeta_system_path, vbmeta_images[2]));
+    EXPECT_TRUE(CompareVBMeta(system_path, vbmeta_images[3]));
+
+    // Skip loading chained vbmeta images.
+    vbmeta_images.clear();
+    EXPECT_EQ(VBMetaVerifyResult::kSuccess,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+                      "" /* expected_public_key_blob*/, false /* allow_verification_error */,
+                      false /* load_chained_vbmeta */, true /* rollback_protection */,
+                      vbmeta_image_path, false /* is_chained_vbmeta*/, &vbmeta_images));
+    // Only vbmeta is loaded.
+    EXPECT_EQ(1UL, vbmeta_images.size());
+    EXPECT_TRUE(CompareVBMeta(vbmeta_path, vbmeta_images[0]));
+}
+
+TEST_F(AvbUtilTest, LoadAndVerifyVbmetaImplWithSuffixes) {
+    // Tests the following chained partitions.
+    // vbmeta_a.img
+    // |--> boot_b.img (boot_other)
+    // |--> vbmeta_system_b.img (vbmeta_system_other)
+    //      |--> system_a.img
+
+    // Generates a raw boot_b.img
+    const size_t boot_image_size = 5 * 1024 * 1024;
+    const size_t boot_partition_size = 10 * 1024 * 1024;
+    base::FilePath boot_path = GenerateImage("boot_b.img", boot_image_size);
+
+    // Adds AVB Hash Footer.
+    AddAvbFooter(boot_path, "hash", "boot", boot_partition_size, "SHA256_RSA2048", 10,
+                 data_dir_.Append("testkey_rsa2048.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates a raw system_a.img, use a smaller size to speed-up unit test.
+    const size_t system_image_size = 10 * 1024 * 1024;
+    const size_t system_partition_size = 15 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system_a.img", system_image_size);
+    // Adds AVB Hashtree Footer.
+    AddAvbFooter(system_path, "hashtree", "system", system_partition_size, "SHA512_RSA4096", 20,
+                 data_dir_.Append("testkey_rsa4096.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates chain partition descriptors.
+    base::FilePath rsa2048_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa2048.pem"));
+    base::FilePath rsa4096_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa4096.pem"));
+    // Makes a vbmeta_system_b.img including the 'system' chained descriptor.
+    auto vbmeta_system_path = GenerateVBMetaImage(
+            "vbmeta_system_b.img", "SHA256_RSA4096", 0, data_dir_.Append("testkey_rsa4096.pem"),
+            {},                                  /* include_descriptor_image_paths */
+            {{"system", 3, rsa4096_public_key}}, /* chain_partitions */
+            "--internal_release_string \"unit test\"");
+
+    // Makes a vbmeta_a.img includeing 'boot_other' and 'vbmeta_system_other' chained descriptors.
+    auto vbmeta_path = GenerateVBMetaImage(
+            "vbmeta_a.img", "SHA256_RSA8192", 0, data_dir_.Append("testkey_rsa8192.pem"),
+            {},                                     /* include_descriptor_image_paths */
+            {{"boot_other", 1, rsa2048_public_key}, /* chain_partitions */
+             {"vbmeta_system_other", 2, rsa4096_public_key}},
+            "--internal_release_string \"unit test\"");
+
+    // Starts to test LoadAndVerifyVbmetaImpl with ab_suffix and ab_other_suffix.
+    auto vbmeta_image_path = [this](const std::string& partition_name) {
+        return test_dir_.Append(partition_name + ".img").value();
+    };
+
+    std::vector<VBMetaData> vbmeta_images;
+    EXPECT_EQ(VBMetaVerifyResult::kSuccess,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "_a" /* ab_suffix */, "_b" /* other_suffix */,
+                      "" /* expected_public_key_blob*/, false /* allow_verification_error */,
+                      true /* load_chained_vbmeta */, true /* rollback_protection */,
+                      vbmeta_image_path, false /* is_chained_vbmeta*/, &vbmeta_images));
+
+    EXPECT_EQ(4UL, vbmeta_images.size());  // vbmeta, boot_other, vbmeta_system_other and system
+    // Binary comparison for each vbmeta image.
+    EXPECT_TRUE(CompareVBMeta(vbmeta_path, vbmeta_images[0]));
+    EXPECT_TRUE(CompareVBMeta(boot_path, vbmeta_images[1]));
+    EXPECT_TRUE(CompareVBMeta(vbmeta_system_path, vbmeta_images[2]));
+    EXPECT_TRUE(CompareVBMeta(system_path, vbmeta_images[3]));
+
+    // Skips loading chained vbmeta images.
+    vbmeta_images.clear();
+    EXPECT_EQ(VBMetaVerifyResult::kSuccess,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "_a" /* ab_suffix */, "_b" /* other_suffix */,
+                      "" /* expected_public_key_blob*/, false /* allow_verification_error */,
+                      false /* load_chained_vbmeta */, true /* rollback_protection */,
+                      vbmeta_image_path, false /* is_chained_vbmeta*/, &vbmeta_images));
+    // Only vbmeta is loaded.
+    EXPECT_EQ(1UL, vbmeta_images.size());
+    EXPECT_TRUE(CompareVBMeta(vbmeta_path, vbmeta_images[0]));
+
+    // Using an invalid suffix for 'other' slot, checks it returns error.
+    EXPECT_EQ(VBMetaVerifyResult::kError,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "_a" /* ab_suffix */,
+                      "_invalid_suffix" /* other_suffix */, "" /* expected_public_key_blob*/,
+                      false /* allow_verification_error */, true /* load_chained_vbmeta */,
+                      true /* rollback_protection */, vbmeta_image_path,
+                      false /* is_chained_vbmeta*/, &vbmeta_images));
+}
+
+TEST_F(AvbUtilTest, LoadAndVerifyVbmetaImplErrorVerification) {
+    // Generates a raw boot.img
+    const size_t boot_image_size = 5 * 1024 * 1024;
+    const size_t boot_partition_size = 10 * 1024 * 1024;
+    base::FilePath boot_path = GenerateImage("boot.img", boot_image_size);
+
+    // Adds AVB Hash Footer.
+    AddAvbFooter(boot_path, "hash", "boot", boot_partition_size, "SHA256_RSA2048", 10,
+                 data_dir_.Append("testkey_rsa2048.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates a raw system.img, use a smaller size to speed-up unit test.
+    const size_t system_image_size = 10 * 1024 * 1024;
+    const size_t system_partition_size = 15 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system.img", system_image_size);
+    // Adds AVB Hashtree Footer.
+    AddAvbFooter(system_path, "hashtree", "system", system_partition_size, "SHA512_RSA4096", 20,
+                 data_dir_.Append("testkey_rsa4096.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates chain partition descriptors.
+    base::FilePath rsa2048_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa2048.pem"));
+    base::FilePath rsa4096_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa4096.pem"));
+
+    // Makes a vbmeta image includeing 'boot' and 'vbmeta_system' chained descriptors.
+    auto vbmeta_path = GenerateVBMetaImage("vbmeta.img", "SHA256_RSA8192", 0,
+                                           data_dir_.Append("testkey_rsa8192.pem"),
+                                           {}, /* include_descriptor_image_paths */
+                                           {{"boot", 1, rsa2048_public_key}, /* chain_partitions */
+                                            {"system", 2, rsa4096_public_key}},
+                                           "--internal_release_string \"unit test\"");
+
+    // Calculates the digest of all chained partitions, to ensure the chained is formed properly.
+    EXPECT_EQ("abbe11b316901f3336e26630f64c4732dadbe14532186ac8640e4141a403721f",
+              CalcVBMetaDigest("vbmeta.img", "sha256"));
+
+    auto vbmeta = LoadVBMetaData("vbmeta.img");
+
+    // Modifies hash, checks there is error if allow_verification_error is false.
+    auto header = vbmeta.GetVBMetaHeader(true /* update_vbmeta_size */);
+    size_t header_block_offset = 0;
+    size_t authentication_block_offset = header_block_offset + sizeof(AvbVBMetaImageHeader);
+
+    // Modifies the hash.
+    ModifyFile(vbmeta_path, authentication_block_offset + header->hash_offset, header->hash_size);
+
+    // Starts to test LoadAndVerifyVbmetaImpl.
+    std::vector<VBMetaData> vbmeta_images;
+    auto vbmeta_image_path = [this](const std::string& partition_name) {
+        return test_dir_.Append(partition_name + ".img").value();
+    };
+    EXPECT_EQ(VBMetaVerifyResult::kError,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+                      "" /* expected_public_key_blob*/, false /* allow_verification_error */,
+                      true /* load_chained_vbmeta */, true /* rollback_protection */,
+                      vbmeta_image_path, false /* is_chained_vbmeta*/, &vbmeta_images));
+    // Stops to load vbmeta because the top-level vbmeta has verification error.
+    EXPECT_EQ(0UL, vbmeta_images.size());
+
+    // Tries again with verification error allowed.
+    EXPECT_EQ(VBMetaVerifyResult::kErrorVerification,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "" /* ab_suffix */, "", /* other_suffix */
+                      "" /* expected_public_key_blob*/, true /* allow_verification_error */,
+                      true /* load_chained_vbmeta */, true /* rollback_protection */,
+                      vbmeta_image_path, false /* is_chained_vbmeta*/, &vbmeta_images));
+
+    EXPECT_EQ(3UL, vbmeta_images.size());  // vbmeta, boot, and system
+    // Binary comparison for each vbmeta image.
+    EXPECT_TRUE(CompareVBMeta(vbmeta_path, vbmeta_images[0]));
+    EXPECT_TRUE(CompareVBMeta(boot_path, vbmeta_images[1]));
+    EXPECT_TRUE(CompareVBMeta(system_path, vbmeta_images[2]));
+
+    // Resets the modification of the hash.
+    ModifyFile(vbmeta_path, 0 /* offset */, -1 /* length */);
+
+    // Modifies the auxiliary data of system.img
+    auto fd = OpenUniqueReadFd(system_path);
+    auto system_footer = GetAvbFooter(fd);
+    auto system_vbmeta = ExtractAndLoadVBMetaData(system_path, "system-vbmeta.img");
+    auto system_header = system_vbmeta.GetVBMetaHeader(true /* update_vbmeta_size */);
+    size_t auxiliary_block_offset =
+            authentication_block_offset + system_header->authentication_data_block_size;
+
+    // Modifies the auxiliary data block.
+    ModifyFile(system_path, system_footer->vbmeta_offset + auxiliary_block_offset,
+               system_header->auxiliary_data_block_size);
+    vbmeta_images.clear();
+    EXPECT_EQ(VBMetaVerifyResult::kError,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+                      "" /* expected_public_key_blob*/, false /* allow_verification_error */,
+                      true /* load_chained_vbmeta */, true /* rollback_protection */,
+                      vbmeta_image_path, false /* is_chained_vbmeta*/, &vbmeta_images));
+    // 'vbmeta', 'boot' but no 'system', because of verification error.
+    EXPECT_EQ(2UL, vbmeta_images.size());
+    // Binary comparison for the loaded 'vbmeta' and 'boot'.
+    EXPECT_TRUE(CompareVBMeta(vbmeta_path, vbmeta_images[0]));
+    EXPECT_TRUE(CompareVBMeta(boot_path, vbmeta_images[1]));
+
+    // Resets the modification of the auxiliary data.
+    ModifyFile(vbmeta_path, 0 /* offset */, -1 /* length */);
+
+    // Sets the vbmeta header flags on a chained partition, which introduces an error.
+    ModifyFile(system_path, system_footer->vbmeta_offset + offsetof(AvbVBMetaImageHeader, flags),
+               sizeof(uint32_t));
+    EXPECT_EQ(VBMetaVerifyResult::kError,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+                      "" /* expected_public_key_blob*/, true /* allow_verification_error */,
+                      true /* load_chained_vbmeta */, true /* rollback_protection */,
+                      vbmeta_image_path, false /* is_chained_vbmeta*/, &vbmeta_images));
+}
+
+TEST_F(AvbUtilTest, LoadAndVerifyVbmetaImplUnexpectedPublicKey) {
+    // Generates chain partition descriptors.
+    base::FilePath rsa2048_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa2048.pem"));
+    base::FilePath rsa4096_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa4096.pem"));
+    base::FilePath rsa8192_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa8192.pem"));
+
+    // Makes a vbmeta image includeing 'boot' and 'vbmeta_system' chained descriptors.
+    auto vbmeta_path = GenerateVBMetaImage("vbmeta.img", "SHA256_RSA8192", 0,
+                                           data_dir_.Append("testkey_rsa8192.pem"),
+                                           {}, /* include_descriptor_image_paths */
+                                           {{"boot", 1, rsa2048_public_key}, /* chain_partitions */
+                                            {"system", 2, rsa4096_public_key}},
+                                           "--internal_release_string \"unit test\"");
+    std::string expected_key_blob_4096;
+    EXPECT_TRUE(base::ReadFileToString(rsa4096_public_key, &expected_key_blob_4096));
+    std::string expected_key_blob_8192;
+    EXPECT_TRUE(base::ReadFileToString(rsa8192_public_key, &expected_key_blob_8192));
+
+    auto vbmeta_image_path = [this](const std::string& partition_name) {
+        return test_dir_.Append(partition_name + ".img").value();
+    };
+    std::vector<VBMetaData> vbmeta_images;
+    // Uses the correct expected public key.
+    EXPECT_EQ(VBMetaVerifyResult::kSuccess,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+                      expected_key_blob_8192, true /* allow_verification_error */,
+                      false /* load_chained_vbmeta */, true /* rollback_protection */,
+                      vbmeta_image_path, false /* is_chained_vbmeta*/, &vbmeta_images));
+
+    // Uses the wrong expected public key with allow_verification_error set to true.
+    vbmeta_images.clear();
+    EXPECT_EQ(VBMetaVerifyResult::kErrorVerification,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+                      expected_key_blob_4096, true /* allow_verification_error */,
+                      false /* load_chained_vbmeta */, true /* rollback_protection */,
+                      vbmeta_image_path, false /* is_chained_vbmeta*/, &vbmeta_images));
+
+    // Uses the wrong expected public key with allow_verification_error set to false.
+    vbmeta_images.clear();
+    EXPECT_EQ(VBMetaVerifyResult::kError,
+              LoadAndVerifyVbmetaImpl(
+                      "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+                      expected_key_blob_4096, false /* allow_verification_error */,
+                      false /* load_chained_vbmeta */, true /* rollback_protection */,
+                      vbmeta_image_path, false /* is_chained_vbmeta*/, &vbmeta_images));
+}
+
+}  // namespace fs_avb_host_test
diff --git a/fs_mgr/libfs_avb/tests/fs_avb_test.cpp b/fs_mgr/libfs_avb/tests/fs_avb_test.cpp
new file mode 100644
index 0000000..2c819a9
--- /dev/null
+++ b/fs_mgr/libfs_avb/tests/fs_avb_test.cpp
@@ -0,0 +1,311 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * 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
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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.
+ */
+
+#include <endian.h>
+#include <stdlib.h>
+
+#include <android-base/file.h>
+#include <base/files/file_util.h>
+#include <base/strings/string_util.h>
+#include <fs_avb/fs_avb.h>
+#include <libavb/libavb.h>
+
+#include "fs_avb_test_util.h"
+
+// Target classes or functions to test:
+using android::fs_mgr::AvbHandle;
+using android::fs_mgr::AvbHandleStatus;
+using android::fs_mgr::HashAlgorithm;
+
+namespace fs_avb_host_test {
+
+class PublicFsAvbTest : public BaseFsAvbTest {
+  public:
+    PublicFsAvbTest(){};
+
+  protected:
+    ~PublicFsAvbTest(){};
+    // Modifies |flags| field in the vbmeta header in an Avb image.
+    // e.g., AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED.
+    void ModifyVBMetaHeaderFlags(const base::FilePath& vbmeta_image_path, uint32_t flags);
+};
+
+void PublicFsAvbTest::ModifyVBMetaHeaderFlags(const base::FilePath& vbmeta_image_path,
+                                              uint32_t flags) {
+    if (!base::PathExists(vbmeta_image_path)) return;
+
+    // Only support modifying the flags in vbmeta*.img.
+    std::string image_file_name = vbmeta_image_path.RemoveExtension().BaseName().value();
+    ASSERT_TRUE(base::StartsWith(image_file_name, "vbmeta", base::CompareCase::INSENSITIVE_ASCII));
+
+    android::base::unique_fd fd(open(vbmeta_image_path.value().c_str(), O_RDWR | O_CLOEXEC));
+    EXPECT_TRUE(fd > 0);
+
+    auto flags_offset = offsetof(AvbVBMetaImageHeader, flags);
+    uint32_t flags_data = htobe32(flags);
+    EXPECT_EQ(flags_offset, lseek64(fd, flags_offset, SEEK_SET));
+    EXPECT_EQ(sizeof flags_data, write(fd, &flags_data, sizeof flags_data));
+}
+
+TEST_F(PublicFsAvbTest, LoadAndVerifyVbmeta) {
+    // Generates a raw boot.img
+    const size_t boot_image_size = 5 * 1024 * 1024;
+    const size_t boot_partition_size = 10 * 1024 * 1024;
+    base::FilePath boot_path = GenerateImage("boot.img", boot_image_size);
+
+    // Adds AVB Hash Footer.
+    AddAvbFooter(boot_path, "hash", "boot", boot_partition_size, "SHA256_RSA2048", 10,
+                 data_dir_.Append("testkey_rsa2048.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates a raw system.img, use a smaller size to speed-up unit test.
+    const size_t system_image_size = 10 * 1024 * 1024;
+    const size_t system_partition_size = 15 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system.img", system_image_size);
+    // Adds AVB Hashtree Footer.
+    AddAvbFooter(system_path, "hashtree", "system", system_partition_size, "SHA512_RSA4096", 20,
+                 data_dir_.Append("testkey_rsa4096.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates chain partition descriptors.
+    base::FilePath rsa2048_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa2048.pem"));
+    base::FilePath rsa4096_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa4096.pem"));
+
+    // Makes a vbmeta image includeing 'boot' and 'system' chained descriptors.
+    auto vbmeta_path = GenerateVBMetaImage("vbmeta.img", "SHA256_RSA8192", 0,
+                                           data_dir_.Append("testkey_rsa8192.pem"),
+                                           {}, /* include_descriptor_image_paths */
+                                           {{"boot", 1, rsa2048_public_key}, /* chain_partitions */
+                                            {"system", 2, rsa4096_public_key}},
+                                           "--internal_release_string \"unit test\"");
+
+    // Calculates the digest of all chained partitions, to ensure the chained is formed properly.
+    EXPECT_EQ("abbe11b316901f3336e26630f64c4732dadbe14532186ac8640e4141a403721f",
+              CalcVBMetaDigest("vbmeta.img", "sha256"));
+
+    // Invokes the public API from fs_avb.h.
+    auto vbmeta_image_path = [this](const std::string& partition_name) {
+        return test_dir_.Append(partition_name + ".img").value();
+    };
+    auto avb_handle = AvbHandle::LoadAndVerifyVbmeta(
+            "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+            "" /* expected_public_key_blob*/, HashAlgorithm::kSHA256,
+            false /* allow_verification_error */, true /* load_chained_vbmeta */,
+            true /* rollback_protection */, vbmeta_image_path);
+    EXPECT_NE(nullptr, avb_handle);
+    EXPECT_EQ(AvbHandleStatus::kSuccess, avb_handle->status());
+
+    // Checks the summary info for all vbmeta images.
+    // Checks the digest matches the value calculated by CalcVBMetaDigest().
+    EXPECT_EQ("abbe11b316901f3336e26630f64c4732dadbe14532186ac8640e4141a403721f",
+              avb_handle->vbmeta_info().digest);
+    EXPECT_EQ(8576UL, avb_handle->vbmeta_info().total_size);
+    EXPECT_EQ(HashAlgorithm::kSHA256, avb_handle->vbmeta_info().hash_algorithm);
+
+    // Skip loading chained vbmeta.
+    avb_handle = AvbHandle::LoadAndVerifyVbmeta(
+            "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+            "" /* expected_public_key_blob*/, HashAlgorithm::kSHA256,
+            false /* allow_verification_error */, false /* load_chained_vbmeta */,
+            true /* rollback_protection */, vbmeta_image_path);
+    EXPECT_NE(nullptr, avb_handle);
+    EXPECT_EQ(AvbHandleStatus::kSuccess, avb_handle->status());
+    EXPECT_EQ("5c31197992b3c72a854ec7dc0eb9609ffebcffab7917ffd381a99ecee328f09c",
+              avb_handle->vbmeta_info().digest);
+    EXPECT_EQ(5184UL, avb_handle->vbmeta_info().total_size);
+    EXPECT_EQ(HashAlgorithm::kSHA256, avb_handle->vbmeta_info().hash_algorithm);
+}
+
+TEST_F(PublicFsAvbTest, LoadAndVerifyVbmetaWithModifications) {
+    // Generates a raw boot.img
+    const size_t boot_image_size = 5 * 1024 * 1024;
+    const size_t boot_partition_size = 10 * 1024 * 1024;
+    base::FilePath boot_path = GenerateImage("boot.img", boot_image_size);
+
+    // Adds AVB Hash Footer.
+    AddAvbFooter(boot_path, "hash", "boot", boot_partition_size, "SHA256_RSA2048", 10,
+                 data_dir_.Append("testkey_rsa2048.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates a raw system.img, use a smaller size to speed-up unit test.
+    const size_t system_image_size = 10 * 1024 * 1024;
+    const size_t system_partition_size = 15 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system.img", system_image_size);
+    // Adds AVB Hashtree Footer.
+    AddAvbFooter(system_path, "hashtree", "system", system_partition_size, "SHA512_RSA4096", 20,
+                 data_dir_.Append("testkey_rsa4096.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates chain partition descriptors.
+    base::FilePath rsa2048_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa2048.pem"));
+    base::FilePath rsa4096_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa4096.pem"));
+
+    // Makes a vbmeta image includeing 'boot' and 'system' chained descriptors.
+    auto vbmeta_path = GenerateVBMetaImage("vbmeta.img", "SHA256_RSA8192", 0,
+                                           data_dir_.Append("testkey_rsa8192.pem"),
+                                           {}, /* include_descriptor_image_paths */
+                                           {{"boot", 1, rsa2048_public_key}, /* chain_partitions */
+                                            {"system", 2, rsa4096_public_key}},
+                                           "--internal_release_string \"unit test\"");
+
+    // Calculates the digest of all chained partitions, to ensure the chained is formed properly.
+    EXPECT_EQ("abbe11b316901f3336e26630f64c4732dadbe14532186ac8640e4141a403721f",
+              CalcVBMetaDigest("vbmeta.img", "sha256"));
+
+    // Sets AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED in the vbmeta.img.
+    ModifyVBMetaHeaderFlags(vbmeta_path, AVB_VBMETA_IMAGE_FLAGS_HASHTREE_DISABLED);
+
+    auto vbmeta_image_path = [this](const std::string& partition_name) {
+        return test_dir_.Append(partition_name + ".img").value();
+    };
+    auto avb_handle = AvbHandle::LoadAndVerifyVbmeta(
+            "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+            "" /* expected_public_key_blob*/, HashAlgorithm::kSHA256,
+            false /* allow_verification_error */, true /* load_chained_vbmeta */,
+            true /* rollback_protection */, vbmeta_image_path);
+    // Returns a null handler because allow_verification is not True.
+    EXPECT_EQ(nullptr, avb_handle);
+
+    // Try again with allow_verification_error set to true.
+    avb_handle = AvbHandle::LoadAndVerifyVbmeta(
+            "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+            "" /* expected_public_key_blob*/, HashAlgorithm::kSHA256,
+            true /* allow_verification_error */, true /* load_chained_vbmeta */,
+            true /* rollback_protection */, vbmeta_image_path);
+    EXPECT_NE(nullptr, avb_handle);
+    EXPECT_EQ(AvbHandleStatus::kHashtreeDisabled, avb_handle->status());
+
+    // Checks the summary info for all vbmeta images.
+    // Checks the digest matches the value calculated by CalcVBMetaDigest().
+    EXPECT_EQ("ae8f7ad95cbb7ce4f0feeeedc2a0a39824af5cd29dad4d028597cab4b8c2e83c",
+              CalcVBMetaDigest("vbmeta.img", "sha256"));
+    EXPECT_EQ("ae8f7ad95cbb7ce4f0feeeedc2a0a39824af5cd29dad4d028597cab4b8c2e83c",
+              avb_handle->vbmeta_info().digest);
+    EXPECT_EQ(8576UL, avb_handle->vbmeta_info().total_size);
+    EXPECT_EQ(HashAlgorithm::kSHA256, avb_handle->vbmeta_info().hash_algorithm);
+
+    // Sets AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED in the vbmeta.img.
+    ModifyVBMetaHeaderFlags(vbmeta_path, AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED);
+    // Loads the vbmeta with allow_verification_error set to true.
+    avb_handle = AvbHandle::LoadAndVerifyVbmeta(
+            "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+            "" /* expected_public_key_blob*/, HashAlgorithm::kSHA256,
+            true /* allow_verification_error */, true /* load_chained_vbmeta */,
+            true /* rollback_protection */, vbmeta_image_path);
+    EXPECT_NE(nullptr, avb_handle);
+    EXPECT_EQ(AvbHandleStatus::kVerificationDisabled, avb_handle->status());
+    // Only the top-level vbmeta.img is loaded, when VERIFICATION_DISABLED is set.
+    // However, CalcVBMetaDigest() reads all vbmeta structs to calculate the digest,
+    // including vbmeta.img, boot.img and syste.img. So we don't compare the digest here.
+    EXPECT_EQ(5184UL, avb_handle->vbmeta_info().total_size);
+
+    // Sets a unknown flag in the vbmeta.imgm and expects to get
+    // AvbHandleStatus::kVerificationError.
+    ModifyVBMetaHeaderFlags(vbmeta_path, 0x10000000);
+    // Loads the vbmeta with allow_verification_error set to true.
+    avb_handle = AvbHandle::LoadAndVerifyVbmeta(
+            "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+            "" /* expected_public_key_blob*/, HashAlgorithm::kSHA256,
+            true /* allow_verification_error */, true /* load_chained_vbmeta */,
+            true /* rollback_protection */, vbmeta_image_path);
+    EXPECT_NE(nullptr, avb_handle);
+    EXPECT_EQ(AvbHandleStatus::kVerificationError, avb_handle->status());
+    // Checks the digest matches the value calculated by CalcVBMetaDigest().
+    EXPECT_EQ("8fb99c4f54500053c3582df5eaf04e9a533137398879188aad9968ec19a664f1",
+              CalcVBMetaDigest("vbmeta.img", "sha256"));
+    EXPECT_EQ("8fb99c4f54500053c3582df5eaf04e9a533137398879188aad9968ec19a664f1",
+              avb_handle->vbmeta_info().digest);
+    EXPECT_EQ(8576UL, avb_handle->vbmeta_info().total_size);
+    EXPECT_EQ(HashAlgorithm::kSHA256, avb_handle->vbmeta_info().hash_algorithm);
+}
+
+TEST_F(PublicFsAvbTest, LoadAndVerifyVbmetaWithPublicKeys) {
+    // Generates a raw boot.img
+    const size_t boot_image_size = 5 * 1024 * 1024;
+    const size_t boot_partition_size = 10 * 1024 * 1024;
+    base::FilePath boot_path = GenerateImage("boot.img", boot_image_size);
+
+    // Adds AVB Hash Footer.
+    AddAvbFooter(boot_path, "hash", "boot", boot_partition_size, "SHA256_RSA2048", 10,
+                 data_dir_.Append("testkey_rsa2048.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates a raw system.img, use a smaller size to speed-up unit test.
+    const size_t system_image_size = 10 * 1024 * 1024;
+    const size_t system_partition_size = 15 * 1024 * 1024;
+    base::FilePath system_path = GenerateImage("system.img", system_image_size);
+    // Adds AVB Hashtree Footer.
+    AddAvbFooter(system_path, "hashtree", "system", system_partition_size, "SHA512_RSA4096", 20,
+                 data_dir_.Append("testkey_rsa4096.pem"), "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Generates chain partition descriptors.
+    base::FilePath rsa2048_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa2048.pem"));
+    base::FilePath rsa4096_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa4096.pem"));
+    base::FilePath rsa8192_public_key =
+            ExtractPublicKeyAvb(data_dir_.Append("testkey_rsa8192.pem"));
+
+    // Makes a vbmeta image includeing 'boot' and 'vbmeta_system' chained descriptors.
+    auto vbmeta_path = GenerateVBMetaImage("vbmeta.img", "SHA256_RSA8192", 0,
+                                           data_dir_.Append("testkey_rsa8192.pem"),
+                                           {}, /* include_descriptor_image_paths */
+                                           {{"boot", 1, rsa2048_public_key}, /* chain_partitions */
+                                            {"system", 2, rsa4096_public_key}},
+                                           "--internal_release_string \"unit test\"");
+
+    auto vbmeta_image_path = [this](const std::string& partition_name) {
+        return test_dir_.Append(partition_name + ".img").value();
+    };
+    std::vector<VBMetaData> vbmeta_images;
+    // Uses the correct expected public key.
+    auto avb_handle = AvbHandle::LoadAndVerifyVbmeta(
+            "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+            rsa8192_public_key.value(), HashAlgorithm::kSHA256, true /* allow_verification_error */,
+            true /* load_chained_vbmeta */, true /* rollback_protection */, vbmeta_image_path);
+    EXPECT_NE(nullptr, avb_handle);
+    EXPECT_EQ(AvbHandleStatus::kSuccess, avb_handle->status());
+
+    // Uses a non-existed public key.
+    avb_handle = AvbHandle::LoadAndVerifyVbmeta(
+            "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+            "/path/to/non-existed/key", HashAlgorithm::kSHA256, true /* allow_verification_error */,
+            true /* load_chained_vbmeta */, true /* rollback_protection */, vbmeta_image_path);
+    EXPECT_EQ(nullptr, avb_handle);
+
+    // Uses an incorrect public key, with allow_verification_error false.
+    avb_handle = AvbHandle::LoadAndVerifyVbmeta(
+            "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+            rsa4096_public_key.value(), HashAlgorithm::kSHA256,
+            false /* allow_verification_error */, true /* load_chained_vbmeta */,
+            true /* rollback_protection */, vbmeta_image_path);
+    EXPECT_EQ(nullptr, avb_handle);
+
+    // Uses an incorrect public key, with allow_verification_error true.
+    avb_handle = AvbHandle::LoadAndVerifyVbmeta(
+            "vbmeta" /* partition_name */, "" /* ab_suffix */, "" /* other_suffix */,
+            rsa4096_public_key.value(), HashAlgorithm::kSHA256, true /* allow_verification_error */,
+            true /* load_chained_vbmeta */, true /* rollback_protection */, vbmeta_image_path);
+    EXPECT_NE(nullptr, avb_handle);
+    EXPECT_EQ(AvbHandleStatus::kVerificationError, avb_handle->status());
+}
+
+}  // namespace fs_avb_host_test
diff --git a/fs_mgr/libfs_avb/tests/fs_avb_test_util.cpp b/fs_mgr/libfs_avb/tests/fs_avb_test_util.cpp
index 95b17d8..17f4c4e 100644
--- a/fs_mgr/libfs_avb/tests/fs_avb_test_util.cpp
+++ b/fs_mgr/libfs_avb/tests/fs_avb_test_util.cpp
@@ -69,7 +69,7 @@
     return trimmed_digest_data;
 }
 
-void BaseFsAvbTest::GenerateVBMetaImage(
+base::FilePath BaseFsAvbTest::GenerateVBMetaImage(
         const std::string& file_name, const std::string& avb_algorithm, uint64_t rollback_index,
         const base::FilePath& key_path,
         const std::vector<base::FilePath>& include_descriptor_image_paths,
@@ -107,17 +107,19 @@
                    chain_partition_options.c_str(), additional_options.c_str(),
                    vbmeta_image.path.value().c_str());
     int64_t file_size;
-    ASSERT_TRUE(base::GetFileSize(vbmeta_image.path, &file_size));
+    EXPECT_TRUE(base::GetFileSize(vbmeta_image.path, &file_size));
     vbmeta_image.content.resize(file_size);
-    ASSERT_TRUE(base::ReadFile(vbmeta_image.path,
+    EXPECT_TRUE(base::ReadFile(vbmeta_image.path,
                                reinterpret_cast<char*>(vbmeta_image.content.data()), file_size));
     // Stores the generated vbmeta image into vbmeta_images_ member object.
     vbmeta_images_.emplace(file_name, std::move(vbmeta_image));
+
+    return vbmeta_images_[file_name].path;  // returns the path.
 }
 
-void BaseFsAvbTest::ExtractVBMetaImage(const base::FilePath& image_path,
-                                       const std::string& output_file_name,
-                                       const size_t padding_size) {
+base::FilePath BaseFsAvbTest::ExtractVBMetaImage(const base::FilePath& image_path,
+                                                 const std::string& output_file_name,
+                                                 const size_t padding_size) {
     VBMetaImage vbmeta_image;
     vbmeta_image.path = test_dir_.Append(output_file_name);
     EXPECT_COMMAND(0,
@@ -127,12 +129,15 @@
                    " --padding_size %zu",
                    image_path.value().c_str(), vbmeta_image.path.value().c_str(), padding_size);
     int64_t file_size;
-    ASSERT_TRUE(base::GetFileSize(vbmeta_image.path, &file_size));
+    EXPECT_TRUE(base::GetFileSize(vbmeta_image.path, &file_size));
     vbmeta_image.content.resize(file_size);
-    ASSERT_TRUE(base::ReadFile(vbmeta_image.path,
+    EXPECT_TRUE(base::ReadFile(vbmeta_image.path,
                                reinterpret_cast<char*>(vbmeta_image.content.data()), file_size));
     // Stores the extracted vbmeta image into vbmeta_images_ member object.
     vbmeta_images_.emplace(output_file_name, std::move(vbmeta_image));
+
+    // Returns the output file path.
+    return vbmeta_images_[output_file_name].path;
 }
 
 // Generates a file with name |file_name| of size |image_size| with
@@ -179,6 +184,49 @@
                    additional_options.c_str());
 }
 
+VBMetaData BaseFsAvbTest::GenerateImageAndExtractVBMetaData(
+        const std::string& partition_name, const size_t image_size, const size_t partition_size,
+        const std::string& footer_type, const base::FilePath& avb_signing_key,
+        const std::string& avb_algorithm, const uint64_t rollback_index) {
+    // Generates a raw image first
+    base::FilePath image_path = GenerateImage(partition_name + ".img", image_size);
+
+    // Appends AVB Hashtree Footer.
+    AddAvbFooter(image_path, footer_type, partition_name, partition_size, avb_algorithm,
+                 rollback_index, avb_signing_key, "d00df00d",
+                 "--internal_release_string \"unit test\"");
+
+    // Extracts vbmeta from the ram image into another *-vbmeta.img.
+    auto vbmeta_image = ExtractVBMetaImage(image_path, partition_name + "-vbmeta.img");
+
+    // Loads *-vbmeta.img into a VBMetaData.
+    std::string vbmeta_buffer;
+    EXPECT_TRUE(base::ReadFileToString(vbmeta_image, &vbmeta_buffer));
+
+    return {(const uint8_t*)vbmeta_buffer.data(), vbmeta_buffer.size(), partition_name};
+}
+
+VBMetaData BaseFsAvbTest::LoadVBMetaData(const std::string& file_name) {
+    auto iter = vbmeta_images_.find(file_name);
+    EXPECT_NE(iter, vbmeta_images_.end());  // ensures file_name is generated before.
+
+    // Gets the image path from iterator->second.path: VBMetaImage.path.
+    base::FilePath image_path = iter->second.path;
+
+    // Loads the vbmeta_image into a VBMetaData.
+    std::string vbmeta_buffer;
+    EXPECT_TRUE(base::ReadFileToString(image_path, &vbmeta_buffer));
+
+    std::string partition_name = image_path.RemoveExtension().BaseName().value();
+    return {(const uint8_t*)vbmeta_buffer.data(), vbmeta_buffer.size(), partition_name};
+}
+
+VBMetaData BaseFsAvbTest::ExtractAndLoadVBMetaData(const base::FilePath& image_path,
+                                                   const std::string& output_file_name) {
+    ExtractVBMetaImage(image_path, output_file_name);
+    return LoadVBMetaData(output_file_name);
+}
+
 std::string BaseFsAvbTest::InfoImage(const base::FilePath& image_path) {
     base::FilePath tmp_path = test_dir_.Append("info_output.txt");
     EXPECT_COMMAND(0, "avbtool info_image --image %s --output %s", image_path.value().c_str(),
diff --git a/fs_mgr/libfs_avb/tests/fs_avb_test_util.h b/fs_mgr/libfs_avb/tests/fs_avb_test_util.h
index f80dc5f..2e46644 100644
--- a/fs_mgr/libfs_avb/tests/fs_avb_test_util.h
+++ b/fs_mgr/libfs_avb/tests/fs_avb_test_util.h
@@ -16,14 +16,20 @@
 
 #pragma once
 
+#include <fcntl.h>
 #include <inttypes.h>
 #include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 #include <sys/wait.h>
+
 #include <string>
 #include <vector>
 
+#include <android-base/unique_fd.h>
 #include <base/files/file_path.h>
 #include <base/strings/stringprintf.h>
+#include <fs_avb/fs_avb.h>
 #include <gtest/gtest.h>
 
 // Utility macro to run the command expressed by the printf()-style string
@@ -36,6 +42,8 @@
         EXPECT_EQ(WEXITSTATUS(rc), expected_exit_status);                           \
     } while (0);
 
+using android::fs_mgr::VBMetaData;
+
 namespace fs_avb_host_test {
 
 struct VBMetaImage {
@@ -51,6 +59,10 @@
     base::FilePath key_blob_path;
 };
 
+inline android::base::unique_fd OpenUniqueReadFd(const base::FilePath& file_path) {
+    return android::base::unique_fd(open(file_path.value().c_str(), O_RDONLY | O_CLOEXEC));
+}
+
 /* Base-class used for unit test. */
 class BaseFsAvbTest : public ::testing::Test {
   public:
@@ -66,16 +78,18 @@
     // Generates a vbmeta image with |file_name| by avbtool.
     // The generated vbmeta image will be written to disk, see the
     // |vbmeta_images_| variable for its path and the content.
-    void GenerateVBMetaImage(const std::string& file_name, const std::string& avb_algorithm,
-                             uint64_t rollback_index, const base::FilePath& key_path,
-                             const std::vector<base::FilePath>& include_descriptor_image_paths,
-                             const std::vector<ChainPartitionConfig>& chain_partitions,
-                             const std::string& additional_options = "");
+    base::FilePath GenerateVBMetaImage(
+            const std::string& file_name, const std::string& avb_algorithm, uint64_t rollback_index,
+            const base::FilePath& key_path,
+            const std::vector<base::FilePath>& include_descriptor_image_paths,
+            const std::vector<ChainPartitionConfig>& chain_partitions,
+            const std::string& additional_options = "");
     // Similar to above, but extracts a vbmeta image from the given image_path.
     // The extracted vbmeta image will be written to disk, with |output_file_name|.
     // See the |vbmeta_images_| variable for its path and the content.
-    void ExtractVBMetaImage(const base::FilePath& image_path, const std::string& output_file_name,
-                            const size_t padding_size = 0);
+    base::FilePath ExtractVBMetaImage(const base::FilePath& image_path,
+                                      const std::string& output_file_name,
+                                      const size_t padding_size = 0);
 
     // Generate a file with name |file_name| of size |image_size| with
     // known content (0x00 0x01 0x02 .. 0xff 0x00 0x01 ..).
@@ -86,9 +100,19 @@
     void AddAvbFooter(const base::FilePath& image_path, const std::string& footer_type,
                       const std::string& partition_name, const uint64_t partition_size,
                       const std::string& avb_algorithm, uint64_t rollback_index,
-                      const base::FilePath& key_path, const std::string& salt = "d00df00d",
+                      const base::FilePath& avb_signing_key, const std::string& salt = "d00df00d",
                       const std::string& additional_options = "");
 
+    VBMetaData GenerateImageAndExtractVBMetaData(
+            const std::string& partition_name, const size_t image_size, const size_t partition_size,
+            const std::string& footer_type, const base::FilePath& avb_signing_key,
+            const std::string& avb_algorithm, const uint64_t rollback_index);
+
+    VBMetaData ExtractAndLoadVBMetaData(const base::FilePath& image_path,
+                                        const std::string& output_file_name);
+
+    VBMetaData LoadVBMetaData(const std::string& file_name);
+
     // Returns the output of 'avbtool info_image' for the |image_path|.
     std::string InfoImage(const base::FilePath& image_path);
     // Same as above, but for an internal vbmeta image with |file_name| in |vbmeta_images_|.
diff --git a/fs_mgr/libfs_avb/tests/util_test.cpp b/fs_mgr/libfs_avb/tests/util_test.cpp
index 835e8fd..9e37d22 100644
--- a/fs_mgr/libfs_avb/tests/util_test.cpp
+++ b/fs_mgr/libfs_avb/tests/util_test.cpp
@@ -15,6 +15,7 @@
  */
 
 #include <unistd.h>
+
 #include <future>
 #include <string>
 #include <thread>
diff --git a/fs_mgr/libfs_avb/util.cpp b/fs_mgr/libfs_avb/util.cpp
index 17d47d9..9d4f05f 100644
--- a/fs_mgr/libfs_avb/util.cpp
+++ b/fs_mgr/libfs_avb/util.cpp
@@ -17,6 +17,7 @@
 #include "util.h"
 
 #include <sys/ioctl.h>
+
 #include <thread>
 
 #include <android-base/unique_fd.h>