Zeroize memory in SHA3 implementation

[aidenfoxivey]

Added a method to do aligned but also zeroed out freeing of context. Used this method within the liboqs's SHA3 implementation.

Doesn't quite fix all of 2163, but is a start.

• Does this PR change the input/output behaviour of a cryptographic algorithm (i.e., does it change known answer test values)? (If so, a version bump will be required from x.y.z to x.(y+1).0.)

No.

• Does this PR change the list of algorithms available -- either adding, removing, or renaming? Does this PR otherwise change an API? (If so, PRs in fully supported downstream projects dependent on these, i.e., oqs-provider will also need to be ready for review and merge by the time this is merged.)

No.

[coveralls]

coverage: 82.782% (+0.02%) from 82.763%
when pulling ac6593d on aidenfoxivey:main
into 47b8fdd on open-quantum-safe:main.

[SWilson4]

Thanks @aidenfoxivey!

[SWilson4]

Let's hold off on merging until #2167 lands and then rebase. I expect there will be merge conflicts, and they will be easier to resolve in this PR. If #2167 takes longer than expected to wrap up, then I will go ahead and merge this one.

[aidenfoxivey]

Sounds good to me @SWilson4 - anything I can do further wrt this issue? (or the broader one)

[SWilson4]

Sounds good to me @SWilson4 - anything I can do further wrt this issue? (or the broader one)

Based on Douglas's assessment in #2163, I'd say the next work would be either sntrup or McEliece—you could take a look at patching that code to clear secret values. However, I'd expect this to take quite a bit longer and to require some analysis to figure out exactly what needs to be cleared.

[aidenfoxivey]

Sounds good to me @SWilson4 - anything I can do further wrt this issue? (or the broader one)

Based on Douglas's assessment in #2163, I'd say the next work would be either sntrup or McEliece—you could take a look at patching that code to clear secret values. However, I'd expect this to take quite a bit longer and to require some analysis to figure out exactly what needs to be cleared.

Sounds good - I’ll take a look at McEliece to start.

[aidenfoxivey]

Woohoo!