Add protection against cache poisoning. - #3045
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mhsmith
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Sep 9, 2026
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Adds a hash verification to already-downloaded assets.
My original motivation for this came from verifying CI results - in particular, verifying that hashes that have been added to templates are correct. Previously, when a download was cached, no hash verification is performed, which means there's no visibility if the hash encoded in a template is correct.
However, in the process of implementing the fix, it occurred to me that this also serves as protection against cache poisoning - if an attacker gains access to a build machine that has a warm download cache, they could insert malicious content into a stub binary or support package, and it would go undetected.
A hash is quick to compute; so adding a hash check on cached files solves both problems.
PR Checklist:
Assisted-by: Claude Sonnet 5