RESTRICT AUTOMERGE: Fix HMAC Compare time attack

Added constant time HMAC comparison preventing attackers being able to
forge HMAC for input by measuring the time difference between
non-constant time comparison of HMAC

Bug: 261085213
Test: None
Tag: #security
Change-Id: I7cd6b68589fd0042b9396dc599b917a0f3220ff7
1 file changed