fix(#340): Eliminate HTTPS DNS rebinding TOCTOU gap with pinned agent#341
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radaghastly merged 1 commit intoMar 9, 2026
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…ed agent Uses https.Agent with a custom lookup function that returns the pre-resolved IP address, eliminating the DNS rebinding window for HTTPS requests while preserving TLS certificate validation via SNI. - assertNotPrivateUrl() now returns a single-use https.Agent for HTTPS - custom-proxy uses fetchWithAgent() wrapper (http.request with agent) - testConnection() uses pinnedRequest() helper with the agent - Node built-in fetch does not support agent option, hence the wrappers Fixes monteslu#340
radaghastly
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LGTM! Clean implementation — https.Agent with custom lookup pins DNS at the connection level while preserving TLS cert validation via SNI. The fetchWithAgent wrapper gives a clean fetch-like interface. Both proxy and testConnection paths covered.
Nice work closing the TOCTOU gap properly. 🔒
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Summary
Eliminates the HTTPS DNS rebinding TOCTOU gap identified in #340 (from PR #283 review).
Problem
assertNotPrivateUrl()resolves DNS to validate the IP is not private, but for HTTPS URLs the subsequentfetch()re-resolves DNS independently. An attacker controlling DNS could return a public IP on first lookup and a private IP on second (DNS rebinding).Solution
Use
https.Agentwith a customlookupfunction that returns the pre-resolved IP. This pins DNS at the connection level while preserving TLS certificate validation via SNI.Changes
src/services/customServiceService.jsassertNotPrivateUrl()returns{ agent }for HTTPS — single-usehttps.Agentwith pinned DNSpinnedRequest()helper fortestConnection()src/routes/custom-proxy.jsfetchWithAgent()— wrapshttp(s).requestin a fetch-like interfaceAll tests pass, lint clean.
Fixes #340