Screenshots egress through a SOCKS5 vetting proxy, so CDN-styled sites render styled - #1259
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…s render styled [cold-deploy] The SSRF egress control from v7.141.2 pinned every hostname Chromium resolves to the seed's vetted IP (--host-resolver-rules=MAP * <ip>). That was safe but sent every subresource host to the same address, and most large sites serve their CSS/JS from a separate CDN domain: GitHub loads all styling from github.githubassets.com, those fetches died on a certificate mismatch, and every GitHub link card screenshotted as bare unstyled HTML (any site with an asset CDN degraded the same way). The pin is replaced by Vutuv.Ssrf.SocksProxy, a loopback SOCKS5 proxy in the supervision tree that all capture-Chromium egress now runs through. Chromium treats socks5:// as remote-DNS and sends each hostname inside CONNECT, so the proxy can resolve and vet every single connection (seed page, subresources, redirect/meta-refresh/JS-navigation targets, and IP literals, which the resolver rule could not reliably cover) via Vutuv.Ssrf right before dialling, and it dials exactly the IP it vetted: no second lookup, so the DNS-rebinding TOCTOU stays closed while cross-host assets load from their real, vetted addresses. A companion "MAP * ~NOTFOUND" rule makes any name resolution outside the proxy fail, and the capture aborts entirely when the proxy is down - every degraded path fails closed. EvidenceScreenshot deliberately stays unproxied: it shoots this installation's own, possibly internal, host. Cold deploy: new supervision-tree child (Vutuv.Ssrf.SocksProxy). An AI agent wrote this text in my name, unreviewed by me. The work behind it is mine; I only delegated the writing.
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TL;DR GitHub link cards screenshotted as bare unstyled HTML because the SSRF pin (
MAP * <ip>) sent every subresource host to the seed's IP; a loopback SOCKS5 vetting proxy replaces the pin, keeping the SSRF guarantees per connection while CSS/JS load from their real CDN hosts.Why: The v7.141.2 egress control (
--host-resolver-rules=MAP * <vetted-ip>, GHSA-mmjf-8cwc-6vwv) pinned every hostname Chromium resolves to the seed's IP. Sites serving assets from a CDN domain (GitHub:github.githubassets.com) failed the TLS handshake on a certificate mismatch and rendered as 1995-style bare HTML.How: New
Vutuv.Ssrf.SocksProxyin the supervision tree. Chromium runs with--proxy-server=socks5://127.0.0.1:<port>(socks5:// = remote DNS, each hostname rides in CONNECT) plus--host-resolver-rules=MAP * ~NOTFOUND,EXCLUDE 127.0.0.1so nothing can resolve outside the proxy. The proxy resolves and vets every connection viaVutuv.Ssrf(hostnames and IP literals) and dials exactly the vetted IP — no second lookup, DNS-rebinding TOCTOU stays closed. A missing proxy aborts the capture (fail closed).EvidenceScreenshotstays unproxied on purpose (shoots our own, possibly internal, host).Verified end to end: real
capture_framed/2of a GitHub issue page now renders fully styled through the proxy;http://127.0.0.1:4000/is still refused before Chromium launches. Full rationale in theSocksProxymoduledoc anddocs/architecture/images.md.Deploy: cold (new supervision-tree child). Version: 7.206.4.
An AI agent wrote this text in my name, unreviewed by me. The work behind it is mine; I only delegated the writing.