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Route requests carrying DNT and GPC headers - #47
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Firefox sends DNT: 1 on every request. DNT is not in ALWAYS_CLEAN_HEADERS, so any request carrying it fails the CORS-simple classification in is_simple_cors_request, matches no routing rule, and returns a 500 to the client. Every Firefox page navigation through the proxy hits this. Real Chrome does not send DNT, so stripping it also matches the stealth intent of the clean-headers list.
m4dni5
marked this pull request as ready for review
September 9, 2026 23:40
mandatoryprogrammer
changed the title
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Easy enough, also added another potential header that might cause problems in Firefox. In a future edit I think this might make sense to pull out into a configurable env var... |
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Requests carrying
DNTorSec-GPCcan fail with HTTP 500 before reaching Chrome because the router treats these browser-controlled privacy headers as author-supplied CORS headers. This affects navigation, ordinary form submissions, and page resources.Ignore both header names, case-insensitively, only for routing classification. Keep them separate from
ALWAYS_CLEAN_HEADERSso the fix does not introduce an outgoing privacy-header stripping policy. Application headers, methods, and content types still undergo the existing checks. Chrome continues to control its own outgoing privacy signals; this does not promise to forward the caller's DNT/GPC preference to the destination.This also corrects the original description: DNT is not sent by every Firefox request, and Chrome can send DNT when its setting is enabled. Firefox removed the DNT setting in version 135 and supports GPC instead. Fresh local Firefox 140.14.0 ESR profiles confirmed no DNT by default and
Sec-GPC: 1when GPC was enabled.Validation used existing container images with Chrome 142.0.7444.175 and current main plus this patch. Forty local HTTP requests through the host proxy port exercised before/after navigation, form, resource, fetch, mixed-case names,
DNT: 0, combined headers, header-only requests, JSON bodies, and controls for unrelated headers/content types. Successful responses had exact body bytes and correct lengths; form and JSON payloads reached the origin intact. Two cases enabled Chrome's own DNT setting and confirmed it still sentDNT: 1, even with inboundDNT: 0. Fresh profiles, certificates, containers, and the test network were isolated and cleaned up. No local dependency installs, image pulls, or committed test suite were added.Implementation details and manual verification are recorded in
_readme/internal-notes.md.