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Socket Reuse Can Cause Multiple CONNECT Requests on Same TCP Connection

Aperta
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#628 4 commenti 3 reazioni 0 assegnatari Vedi su GitHub

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Valutazione

Difficoltà
4/5
Tempo stimato
3-5 giorni
Idoneità per principianti
25/100
Tipo di issue
Bug
Chiarezza
Abbastanza chiara
Stato di attività
Ferma
Stack tecnologico
nodejs, typescript
Ambito
networking

Direzione di ricerca

Start with the socket-reuse comment near chain.js:52 and the httpAgent option that prepareRequestFunction accepts, then check how anonymizeProxy builds its upstream connection. Reproducing needs an upstream proxy and a tcpdump capture of repeated CONNECT requests on one socket. The open question is whether reuse is a bug or expected, so a maintainer decision on that comes before any change.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

bug medium priority t-unblocking

Summary

When using ProxyChain without specifying a custom httpAgent in prepareRequestFunction or using anonimyzeProxy, Node.js's default HTTP agent (which has keepAlive: true) may reuse TCP sockets for multiple CONNECT requests to the upstream proxy. This can cause intermittent connection failures when using proxy-chain to forward requests to an upstream proxy server.

Background

According to RFC 9110 Section 9.3.6:

A tunnel is closed when a tunnel intermediary detects that either side has closed its connection: the intermediary MUST attempt to send any outstanding data that came from the closed side to the other side, close both connections, and then discard any remaining data left undelivered.

After a successful CONNECT response (200), the TCP connection becomes a tunnel and should be treated as opaque to HTTP semantics. I may be misunderstanding the specification, but it seems that sending another CONNECT request through an already-established tunnel might violate this principle.

Reproducing

This issue was initially observed when using anonymizeProxy(), which creates a ProxyChain server that forwards to upstream proxies.
This appears more frequently on slower machines where there's more temporal overlap between requests.

import ProxyChain from "proxy-chain";
import puppeteer from "puppeteer";

const proxyUrl = await ProxyChain.anonymizeProxy(
    "http://user:[email protected]:8080"
);

const browser = await puppeteer.launch({
    args: [`--proxy-server=${proxyUrl}`],
});

const page = await browser.newPage();
await page.goto("https://www.github.com/");
// Intermittent failures observed here

We then used tcpdump to capture traffic and observe socket re-use.

Workaround

The issue can be resolved by providing a custom httpAgent with keepAlive: false:

import http from 'http';

const noReuseAgent = new http.Agent({
    keepAlive: false,
    maxSockets: Infinity,
    maxFreeSockets: 0,
});

const server = new ProxyChain.Server({
    prepareRequestFunction: () => ({
        upstreamProxyUrl: "http://user:[email protected]:8080",
        requestAuthentication: false,
        httpAgent: noReuseAgent,  // Prevents socket reuse
    }),
});

With this configuration, each CONNECT request gets a fresh TCP connection to the upstream proxy, eliminating the intermittent failures.

Questions

I'd appreciate clarification on a few points:

  1. Is this expected behavior? The comment in chain.js:52 mentions "Socket can be re-used by multiple requests" which suggests awareness of socket reuse, but I'm unsure if this refers to regular HTTP requests or CONNECT tunnels.

  2. Is my interpretation of the HTTP spec correct? I may be misunderstanding how CONNECT tunnels should work in the context of HTTP connection pooling.

  3. Is socket reuse for CONNECT requests a common practice? Perhaps this behavior works fine with some upstream proxies and only certain implementations reject it.

Lingua principale
TypeScript
Stelle
1k
Fork
167
Merge medio
16h 22m
PR unite (30g)
16

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