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Strip sec-ch-* client-hint headers by prefix for CORS classification - #48
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The client-hint header family is open-ended and grows with every Chrome release (sec-ch-ua-wow64, sec-ch-ua-form-factors, ...). Enumerating them in ALWAYS_CLEAN_HEADERS rots: any unlisted client-hint fails the CORS-simple check and returns a 500 for that subresource request. Match the whole sec-ch- family by prefix instead.
m4dni5
marked this pull request as ready for review
September 9, 2026 23:40
mandatoryprogrammer
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mandatoryprogrammer
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Looks like unrelated concurrency cap code was in the PR, I removed it and reduced it to just the header strip logic. Thanks for the contribution! |
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Problem
Chromium sends client-hint headers like
sec-ch-ua-wow64that aren't inALWAYS_CLEAN_HEADERS. Requests carrying them return a 500 and their subresources fail to load.Root cause
To classify a request,
is_simple_cors_requestrequires every header to be on a fixed allowlist. Any header it doesn't recognize fails the check, no routing rule matches, and the request 500s.New
sec-ch-*headers appear with every Chrome release, so listing them one by one inALWAYS_CLEAN_HEADERSbreaks again each time.Fix
Strip the whole
sec-ch-*family by prefix before classification, so any current or future client hint is handled. Existing entries are left for any other consumers of the list.Verification
Requests carrying
sec-ch-ua-wow64: ?0500'd before, route correctly after.