🔒 Prevent Safeguard Mechanisms Bypassing

[pcaversaccio]

🕓 Changelog

This PR introduces a change that for the non-pseudo-random cases, the salt value salt is hashed as part of the _guard function to prevent the safeguard mechanisms from being bypassed. The reason is that if someone deploys on chain A with a preconfigured mechanism, anyone can calculate the inferred guardedSalt and reuse it on chain B. Since we didn't originally modify the salt value in this case, anyone could abuse this. To prevent this, we hash the salt value in those cases (I deliberately don't use inline assembly to have a simple one-liner with a ternary operator which increases readability). The exception is for pseudo-randomly generated salt values, where this is unnecessary. The h/t goes to @lastperson for making me aware of this issue, thanks a lot 🙏!

In the security considerations, the second section still holds true (it would only be frontrun-protected in the case salt == _generateSalt() for the frontrunner on another chain, which would require a hash collision), but the third section is not anymore true (since if you deploy on chain A with a pseudo-random value and someone else uses this on chain B, the value will now be hashed (except for the case if salt == _generateSalt() which is again not likely since you would need to find a hash collision)) and thus I remove it.

This PR is rebased on #37.

🐶 Cute Animal Picture

[github-actions[bot]]

Coverage after merging guard-fix into main will be

100.00%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src
CreateX.sol	100%	100%	100%	100%

[mds1]

Great catch!