diff --git a/fs_mgr/libfs_avb/Android.bp b/fs_mgr/libfs_avb/Android.bp
index 32702ae..bf51fe7 100644
--- a/fs_mgr/libfs_avb/Android.bp
+++ b/fs_mgr/libfs_avb/Android.bp
@@ -37,11 +37,9 @@
         "libfstab",
     ],
     shared_libs: [
+        "libbase",
         "libcrypto",
     ],
-    header_libs: [
-        "libbase_headers",
-    ],
     target: {
         darwin: {
             enabled: false,
diff --git a/fs_mgr/libfs_avb/fs_avb.cpp b/fs_mgr/libfs_avb/fs_avb.cpp
index c4d7511..8770a6b 100644
--- a/fs_mgr/libfs_avb/fs_avb.cpp
+++ b/fs_mgr/libfs_avb/fs_avb.cpp
@@ -22,6 +22,7 @@
 #include <sys/ioctl.h>
 #include <sys/types.h>
 
+#include <algorithm>
 #include <sstream>
 #include <string>
 #include <vector>
@@ -308,7 +309,18 @@
             return nullptr;
     }
 
-    if (!ValidatePublicKeyBlob(public_key_data, Split(fstab_entry.avb_keys, ":"))) {
+    // fstab_entry.avb_keys might be either a directory containing multiple keys,
+    // or a string indicating multiple keys separated by ':'.
+    std::vector<std::string> allowed_avb_keys;
+    auto list_avb_keys_in_dir = ListFiles(fstab_entry.avb_keys);
+    if (list_avb_keys_in_dir) {
+        std::sort(list_avb_keys_in_dir->begin(), list_avb_keys_in_dir->end());
+        allowed_avb_keys = *list_avb_keys_in_dir;
+    } else {
+        allowed_avb_keys = Split(fstab_entry.avb_keys, ":");
+    }
+
+    if (!ValidatePublicKeyBlob(public_key_data, allowed_avb_keys)) {
         avb_handle->status_ = AvbHandleStatus::kVerificationError;
         LWARNING << "Found unknown public key used to sign " << fstab_entry.mount_point;
         if (!allow_verification_error) {
diff --git a/fs_mgr/libfs_avb/tests/util_test.cpp b/fs_mgr/libfs_avb/tests/util_test.cpp
index 12b5acb..e64282b 100644
--- a/fs_mgr/libfs_avb/tests/util_test.cpp
+++ b/fs_mgr/libfs_avb/tests/util_test.cpp
@@ -16,10 +16,12 @@
 
 #include <unistd.h>
 
+#include <algorithm>
 #include <future>
 #include <string>
 #include <thread>
 
+#include <android-base/strings.h>
 #include <base/files/file_util.h>
 
 #include "fs_avb_test_util.h"
@@ -29,6 +31,7 @@
 using android::fs_mgr::BytesToHex;
 using android::fs_mgr::FileWaitMode;
 using android::fs_mgr::HexToBytes;
+using android::fs_mgr::ListFiles;
 using android::fs_mgr::NibbleValue;
 using android::fs_mgr::WaitForFile;
 
@@ -210,4 +213,102 @@
     ASSERT_TRUE(base::DeleteFile(wait_path, false /* resursive */));
 }
 
+TEST(BasicUtilTest, ListFiles) {
+    // Gets system tmp dir.
+    base::FilePath tmp_dir;
+    ASSERT_TRUE(GetTempDir(&tmp_dir));
+
+    // Creates a test dir for ListFiles testing.
+    base::FilePath test_dir;
+    ASSERT_TRUE(base::CreateTemporaryDirInDir(tmp_dir, "list-file-tests.", &test_dir));
+
+    // Generates dummy files to list.
+    base::FilePath file_path_1 = test_dir.Append("1.txt");
+    ASSERT_TRUE(base::WriteFile(file_path_1, "1", 1));
+    base::FilePath file_path_2 = test_dir.Append("2.txt");
+    ASSERT_TRUE(base::WriteFile(file_path_2, "22", 2));
+    base::FilePath file_path_3 = test_dir.Append("3.txt");
+    ASSERT_TRUE(base::WriteFile(file_path_3, "333", 3));
+
+    // List files for comparison.
+    auto result = ListFiles(test_dir.value());
+    ASSERT_TRUE(result);
+    ASSERT_TRUE(result.has_value());
+    auto files = result.value();
+    EXPECT_EQ(3UL, files.size());
+    // Sort them offline for comparison.
+    std::sort(files.begin(), files.end());
+    EXPECT_EQ(file_path_1.value(), files[0]);
+    EXPECT_EQ(file_path_2.value(), files[1]);
+    EXPECT_EQ(file_path_3.value(), files[2]);
+
+    ASSERT_TRUE(base::DeleteFile(test_dir, true /* resursive */));
+}
+
+TEST(BasicUtilTest, ListFilesShouldDiscardSymlink) {
+    // Gets system tmp dir.
+    base::FilePath tmp_dir;
+    ASSERT_TRUE(GetTempDir(&tmp_dir));
+
+    // Creates a test dir for ListFiles testing.
+    base::FilePath test_dir;
+    ASSERT_TRUE(base::CreateTemporaryDirInDir(tmp_dir, "list-file-tests.", &test_dir));
+
+    // Generates dummy files to list.
+    base::FilePath file_path_1 = test_dir.Append("1.txt");
+    ASSERT_TRUE(base::WriteFile(file_path_1, "1", 1));
+    base::FilePath file_path_2 = test_dir.Append("2.txt");
+    ASSERT_TRUE(base::WriteFile(file_path_2, "22", 2));
+    // Creates a symlink and checks it won't be returned by ListFiles.
+    base::FilePath file_path_3 = test_dir.Append("3.txt");
+    base::FilePath non_existent_target = test_dir.Append("non_existent_target.txt");
+    ASSERT_TRUE(base::CreateSymbolicLink(non_existent_target, file_path_3));
+
+    // List files for comparison.
+    auto result = ListFiles(test_dir.value());
+    ASSERT_TRUE(result);
+    ASSERT_TRUE(result.has_value());
+    auto files = result.value();
+    EXPECT_EQ(2UL, files.size());  // Should not include the symlink file.
+    // Sort them offline for comparison.
+    std::sort(files.begin(), files.end());
+    EXPECT_EQ(file_path_1.value(), files[0]);
+    EXPECT_EQ(file_path_2.value(), files[1]);
+
+    ASSERT_TRUE(base::DeleteFile(test_dir, true /* resursive */));
+}
+
+TEST(BasicUtilTest, ListFilesOpenDirFailure) {
+    // Gets system tmp dir.
+    base::FilePath tmp_dir;
+    ASSERT_TRUE(GetTempDir(&tmp_dir));
+
+    // Generates dummy files to list.
+    base::FilePath no_such_dir = tmp_dir.Append("not_such_dir");
+
+    auto fail = ListFiles(no_such_dir.value());
+    ASSERT_FALSE(fail);
+    EXPECT_EQ(ENOENT, fail.error().code());
+    EXPECT_TRUE(android::base::StartsWith(fail.error().message(), "Failed to opendir: "));
+}
+
+TEST(BasicUtilTest, ListFilesEmptyDir) {
+    // Gets system tmp dir.
+    base::FilePath tmp_dir;
+    ASSERT_TRUE(GetTempDir(&tmp_dir));
+
+    // Creates a test dir for ListFiles testing.
+    base::FilePath test_dir;
+    ASSERT_TRUE(base::CreateTemporaryDirInDir(tmp_dir, "list-file-tests.", &test_dir));
+
+    // List files without sorting.
+    auto result = ListFiles(test_dir.value());
+    ASSERT_TRUE(result);
+    ASSERT_TRUE(result.has_value());
+    auto files = result.value();
+    EXPECT_EQ(0UL, files.size());
+
+    ASSERT_TRUE(base::DeleteFile(test_dir, true /* resursive */));
+}
+
 }  // namespace fs_avb_host_test
diff --git a/fs_mgr/libfs_avb/util.cpp b/fs_mgr/libfs_avb/util.cpp
index d214b5b..7783d04 100644
--- a/fs_mgr/libfs_avb/util.cpp
+++ b/fs_mgr/libfs_avb/util.cpp
@@ -16,10 +16,13 @@
 
 #include "util.h"
 
+#include <dirent.h>
 #include <sys/ioctl.h>
+#include <sys/types.h>
 
 #include <thread>
 
+#include <android-base/stringprintf.h>
 #include <android-base/unique_fd.h>
 #include <linux/fs.h>
 
@@ -122,5 +125,23 @@
     return ioctl(fd, BLKROSET, &ON) == 0;
 }
 
+Result<std::vector<std::string>> ListFiles(const std::string& dir) {
+    struct dirent* de;
+    std::vector<std::string> files;
+
+    std::unique_ptr<DIR, int (*)(DIR*)> dirp(opendir(dir.c_str()), closedir);
+    if (!dirp) {
+        return ErrnoError() << "Failed to opendir: " << dir;
+    }
+
+    while ((de = readdir(dirp.get()))) {
+        if (de->d_type != DT_REG) continue;
+        std::string full_path = android::base::StringPrintf("%s/%s", dir.c_str(), de->d_name);
+        files.emplace_back(std::move(full_path));
+    }
+
+    return files;
+}
+
 }  // namespace fs_mgr
 }  // namespace android
diff --git a/fs_mgr/libfs_avb/util.h b/fs_mgr/libfs_avb/util.h
index 7763da5..427ab7c 100644
--- a/fs_mgr/libfs_avb/util.h
+++ b/fs_mgr/libfs_avb/util.h
@@ -18,6 +18,7 @@
 
 #include <chrono>
 #include <string>
+#include <vector>
 
 #ifdef HOST_TEST
 #include <base/logging.h>
@@ -25,6 +26,11 @@
 #include <android-base/logging.h>
 #endif
 
+#include <android-base/result.h>
+
+using android::base::ErrnoError;
+using android::base::Result;
+
 #define FS_AVB_TAG "[libfs_avb]"
 
 // Logs a message to kernel
@@ -60,5 +66,8 @@
 
 bool SetBlockDeviceReadOnly(const std::string& blockdev);
 
+// Returns a list of file under the dir, no order is guaranteed.
+Result<std::vector<std::string>> ListFiles(const std::string& dir);
+
 }  // namespace fs_mgr
 }  // namespace android