authfs: Add MerkleLeaves for integrity bookkeeping
MerkleLeaves will be used by a "writer" for remembering the hashes of
written blocks for integrity checking. For example, when a file is
written from a trusted environment to an untrusted storage / remote,
MerkleLeaves allows the writer to verify the reads later with a
cryptographical strong hash.
Besides verification, if requested, the tree can grow from the leaves(!)
to generate the root hash and fs-verity digest.
- fsverity/builder.rs: implements MerkleLeaves
- fsverity/verifier.rs: renamed from fsverity.rs with minor changes
- fsverity/common.rs: common utils from the original fsverity.rs with
one addition error in the enum
- crypto.rs: more helper function / constant
Bug: 171279640
Test: atest authfs_device_test_src_lib
Change-Id: I76e5ebd81a2f2afa017e3c670774ccbb797766df
diff --git a/authfs/src/fsverity/sys.rs b/authfs/src/fsverity/sys.rs
new file mode 100644
index 0000000..b3222db
--- /dev/null
+++ b/authfs/src/fsverity/sys.rs
@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+/// Magic used in fs-verity digest
+pub const FS_VERITY_MAGIC: &[u8; 8] = b"FSVerity";
+
+/// fs-verity version that we are using
+pub const FS_VERITY_VERSION: u8 = 1;
+
+/// Hash algorithm to use from linux/fsverity.h
+pub const FS_VERITY_HASH_ALG_SHA256: u8 = 1;
+
+/// Log 2 of the block size (only 4096 is supported now)
+pub const FS_VERITY_LOG_BLOCKSIZE: u8 = 12;