Original Motivation

SHA-256, SHA-512 and SHA-512/256 are secure hash algorithms specified in FIPS 180-4, NIST’s Secure Hash Standard. ZFS uses the above as block checksums (checksum=sha256, checksum=sha512) for data integrity and deduplication. There is currently no unit test coverage for this family of hash algorithms.

What does this commit introduce?

It adds a tests/unit/test_sha2.c with three types of tests that follow the FIPS 180-4 standard as defined in https://nvlpubs.nist.gov/nistpubs/fips/nist.fips.180-4.pdf :

• known answer tests (KAT) for SHA-256, SHA-512 and SHA-512/256, using the same NIST test messages and digests as tests/zfs-tests/cmd/checksum/sha2_test.c
• an incremental test: split updates across the 64- and 128-byte message block boundaries must produce the same digest as a single update
• a cross-implementation test via zfs_impl_get_ops(): every supported implementation must reproduce the known answer and compute the same digest for a multi-block message

Testing perfomed:

$ make unit T=sha2
  UNITTEST tests/unit/test_sha2
Running test suite with seed 0xcf392006...
sha2.sha256_known                    [ OK    ] [ 0.00002286 / 0.00001675 CPU ]
sha2.sha512_known                    [ OK    ] [ 0.00002044 / 0.00001995 CPU ]
sha2.sha512_256_known                [ OK    ] [ 0.00001542 / 0.00001524 CPU ]
sha2.incremental                     [ OK    ] [ 0.00019737 / 0.00019336 CPU ]
sha2.impls                           [ OK    ] [ 0.00026169 / 0.00026171 CPU ]
5 of 5 (100%) tests successful, 0 (0%) test skipped.

https://github.com/openzfs/zfs/pull/18779