Security improvements to GitHub Actions

[frouioui]

Description

In this PR the Assign Milestone and Release GitHub actions were modified into to harden our GitHub Actions usage. The changes brought to these two workflows are made to avoid and limit potential pwn requests and cache poisoning attacks.

In addition to these two files, I have bumped the version of actions/checkout and made sure to disable persist-credentials where it was not needed.

Let's backport / do something similar on all release branches.

Assign Milestone

This workflow uses the pull_request_target trigger, meaning that the workflow is executed in the context of the PR's base commit, which can quickly become problematic if not handled correctly. I made the workflow a bit tighter by removing the setup-go step (which uses caching by default), limiting the permissions, by adding a sanity check on the ./go/vt/servenv/version.go file that we read, and most importantly by not checking out the PR's HEAD but rather the base's HEAD.

Release

I have added a verification of fpm's checksum and disabled caching for the setup-go step. Disabling the cache in that workflow is a SLSA level 3 requirement:

SLSA 3 provides much stronger protections against tampering than earlier levels by preventing specific classes of threats, such as cross-build contamination.

This workflow was tested here: https://github.com/frouioui/vitess/actions/runs/12776723633/job/35616102340

[vitess-bot]

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

• Ensure that the Pull Request has a descriptive title.
• Ensure there is a link to an issue (except for internal cleanup and flaky test fixes), new features should have an RFC that documents use cases and test cases.

Tests

• Bug fixes should have at least one unit or end-to-end test, enhancement and new features should have a sufficient number of tests.

Documentation

• Apply the release notes (needs details) label if users need to know about this change.
• New features should be documented.
• There should be some code comments as to why things are implemented the way they are.
• There should be a comment at the top of each new or modified test to explain what the test does.

New flags

• Is this flag really necessary?
• Flag names must be clear and intuitive, use dashes (-), and have a clear help text.

If a workflow is added or modified:

• Each item in Jobs should be named in order to mark it as required.
• If the workflow needs to be marked as required, the maintainer team must be notified.

Backward compatibility

• Protobuf changes should be wire-compatible.
• Changes to _vt tables and RPCs need to be backward compatible.
• RPC changes should be compatible with vitess-operator
• If a flag is removed, then it should also be removed from vitess-operator and arewefastyet, if used there.
• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.71%. Comparing base (a9d6969) to head (890c2a8).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17520      +/-   ##
==========================================
+ Coverage   67.69%   67.71%   +0.01%     
==========================================
  Files        1584     1584              
  Lines      254541   254509      -32     
==========================================
+ Hits       172315   172340      +25     
+ Misses      82226    82169      -57     

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[mattlord]

Thanks, @frouioui !

[rohit-nayak-ps]

👍🏽

[rohit-nayak-ps]

❤️