cksum: Accept SHAKE algorithms

[RenjiSann]

#10002

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/usage_vs_getopt (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/shuf/shuf-reservoir (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/sort/sort-stale-thread-mem (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/usage_vs_getopt (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/shuf/shuf-reservoir (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/sort/sort-stale-thread-mem (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/tail-n0f. tests/tail/tail-n0f is passing on 'main'. Maybe you have to rebase?
Skipping an intermittent issue tests/misc/usage_vs_getopt (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/shuf/shuf-reservoir (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/sort/sort-stale-thread-mem (passes in this run but fails in the 'main' branch)

[oech3]

On Arch Linux, shake128sum -N non_negative_integer /dev/null is possible:

       -N, -O output-size
              Change the output size.

[RenjiSann]

On Arch Linux, shake128sum -N non_negative_integer /dev/null is possible:

       -N, -O output-size
              Change the output size.

Since we are embedding this in cksum, I'd rather keep -l to not pollute the --help and argument processing with algorithm-specific flags.

[RenjiSann]

I have an issue with what behavior should we prefer for --length sanitization. Since we're expecting a bit length we're always full bytes, any value not a multiple of 8 doesn't make sense. So either:
a) Like BLAKE2b, we make values that are not a multiple of 8 an invalid argument;
b) Or, like this website, we round this value to the biggest smaller multiple of 8.

For the sake of consistency within our tool, I'm more inclined to do a).

WDYT @oech3

[oech3]

Hmm...

$ shake128sum -N 1 /dev/null
01  /dev/null
$ shake128sum -N 2 /dev/null
03  /dev/null
$ shake128sum -N 3 /dev/null
07  /dev/null
$ shake128sum -N 4 /dev/null
0f  /dev/null
$ shake128sum -N 5 /dev/null
1f  /dev/null
$ shake128sum -N 6 /dev/null
3f  /dev/null
$ shake128sum -N 7 /dev/null
7f  /dev/null
$ shake128sum -N 8 /dev/null
7f  /dev/null

$ shake128sum /dev/null
7f9c2ba4e88f827d616045507605853e  /dev/null
$ shake128sum -N 128 /dev/null
7f9c2ba4e88f827d616045507605853e  /dev/null

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/usage_vs_getopt (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/follow-name (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tty/tty-eof (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/usage_vs_getopt (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/shuf/shuf-reservoir (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/sort/sort-stale-thread-mem (passes in this run but fails in the 'main' branch)

[RenjiSann]

I see, that's not what our hashsum implementation used to do, but it's quite easy to implement

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/symlink. tests/tail/symlink is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/misc/usage_vs_getopt (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/shuf/shuf-reservoir (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/sort/sort-stale-thread-mem (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/shuf/shuf-reservoir (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/sort/sort-stale-thread-mem (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/follow-name (fails in this run but passes in the 'main' branch)