cksum: add length support for shake128 and shake256 validation

[AldanTanneo]

As pure XOF hashes, shake* algos don't make much sense if we don't specify the length. This follows the current behaviour of the blake2b algo, where the length is appended (when not the default) in the same way as with the sha3 family.

It is unfortunate that bit and byte length are used in the same variable for different algos right now. I'm tempted to have another PR to make this uniform.

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/retry. tests/tail/retry is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/date/resolution (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/pr/bounded-memory (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tty/tty-eof (passes in this run but fails in the 'main' branch)

[oech3]

I think length's unit is coming from https://codeberg.org/maandree/sha3sum .

[RenjiSann]

I agree the length option being undecidedly in bits or bytes is an issue, and we should try to stay coherent. The only issue I have with that is that we should make sure we are not going against strongly established existing implementations

On another topic, tbh I am not a fan of not writing the length in the tagged output because it is the default length, and I think we should make our output as explicit as possible (while still being able to decode tagged lines that are missing the length.

WDYT ?

[oech3]

Just follow with

$ cksum -a blake2b -l 512 /dev/null
BLAKE2b (/dev/null) = 786a02f742015903c6c6fd852552d272912f4740e15847618a86e217f71f5419d25e1031afee585313896444934eb04b903a685b1448b755d56f701afe9be2ce
$ cksum -a blake2b -l 512 /dev/null > /tmp/b
$ cat /tmp/b | cksum -c
/dev/null: OK
$ sed "s/BLAKE2b/BLAKE2b-512/" /tmp/b | cksum -c -
/dev/null: OK

?

[RenjiSann]

Just follow with

$ cksum -a blake2b -l 512 /dev/null
BLAKE2b (/dev/null) = 786a02f742015903c6c6fd852552d272912f4740e15847618a86e217f71f5419d25e1031afee585313896444934eb04b903a685b1448b755d56f701afe9be2ce
$ cksum -a blake2b -l 512 /dev/null > /tmp/b
$ cat /tmp/b | cksum -c
/dev/null: OK
$ sed "s/BLAKE2b/BLAKE2b-512/" /tmp/b | cksum -c -
/dev/null: OK

?

The more I think of it, the less I'm convinced.
Not writing down the XOF length in tagged mode when the length is default isn't a good practice imo, as it prevents the validation step afterwards from easily parsing the length. Also, it adds unnecessary overhead in the code to handle this specific case.

I think we can deviate from GNU behavior here and provide the XOF length every time. The output will still be compatible with GNU, though, so it's not a big deal.

[oech3]

Since GNU does not have definition for them yet, including length always is useful.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/pr/bounded-memory (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/symlink (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.
Congrats! The gnu test tests/tail/tail-n0f is now passing!

[codspeed-hq]

Merging this PR will not alter performance

✅ 298 untouched benchmarks
⏩ 48 skipped benchmarks¹

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_{Comparing AldanTanneo:shake_validation (53bcdb9) with main (0f891cc)}

Footnotes

1. 48 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/pr/bounded-memory (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/symlink (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tty/tty-eof (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/tail/tail-n0f is now passing!

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tail/symlink (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/dd/no-allocate is now being skipped but was previously passing.
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.