feat: Add fuzz target, fix several panics

[folkertdev]

closes #6

turns out there are at least 3 overflow issues (and likely many more). Adding a fuzzer is easy, fixing the things it finds is not. I'm also not sure what the preferred way of running the fuzzer is (e.g. on CI for each PR?)

I've fixed one overflow where I think the solution is obvious. But quickly things get less obvious.

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cargo +nightly fuzz run no_panic fuzz/artifacts/no_panic/crash-92004600d4f07f7b413ba4b94bdb5d174e0a0876

fails on this line in rc-zip/src/parse/eocd.rs

let computed_directory_offset = res.located_directory_offset() - res.directory_size();

that needs to return some sort of format error, not sure which one yet (I suspect none of the existing errors fit).

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cargo +nightly fuzz run no_panic fuzz/artifacts/no_panic/crash-87fc6b172449245303df41752bc5742ee08e1ef5

fails with an overflow in rc-zip/src/parse/central_directory_file_header.rs:151, again the fix is not immediately obvious

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By staring at these specific cases I'm sure I could come up with a fix, but I'm not sure what a good general process for fixing these issues looks like. It seems very likely that there will be more issues.

[folkertdev]

I think all overflows are fixed now, the fuzzer has been running for many hours without finding more.

I also had reason to create a zip file with a unix extra field. This turned out to be more difficult than expected, but can be replicated using these files https://gist.github.com/folkertdev/79b31ab271602bf095957868aed449d4

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 75.72%. Comparing base (25b0610) to head (53dd872).

Files	Patch %	Lines
rc-zip/src/parse/extra_field.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #67      +/-   ##
==========================================
- Coverage   76.08%   75.72%   -0.37%     
==========================================
  Files          25       25              
  Lines        2409     2385      -24     
==========================================
- Hits         1833     1806      -27     
- Misses        576      579       +3     

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[fasterthanlime]

Thanks for tackling this!

The changes look good, I think I'm happy to merge it as-is, and we can do smaller fixes as follow-ups!