authfs: create a chunked reader with fs-verity verification

The new chunked reader uses a Merkle tree to verify each chunk read of
the corresponding backing file. The reader also accepts an
autheneticator for signature verification, though it is currently a fake
implementation due to the lack of PKCS#7 signature support in BoringSSL
(b/170494765).

Test: atest authfs_host_test_src_lib
Bug: 171310075

Change-Id: Ibf4151ab2a93f7515ad8c9c0462df6c21c10d767
10 files changed
tree: 37415e71e941c2aecb2ee096ad6599bffeaab9bc
  1. authfs/
  2. docs/
  3. .clang-format
  4. PREUPLOAD.cfg