fix(socks5-proxy-agent): use per-origin pools to prevent cross-origin routing (#5041)

The Socks5ProxyAgent stored a single Pool keyed implicitly to the first
origin it saw and reused it for every subsequent request. When a second
request targeted a different origin, it was dispatched through the
existing pool whose connect callback tunnelled to the original origin,
causing the request to reach the wrong host (and potentially leaking
headers/credentials intended for origin B to origin A).

Track pools in a Map keyed by origin so each origin gets its own pool
and SOCKS5 tunnel.

Signed-off-by: Nikita Skovoroda <chalkerx@gmail.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Nikita Skovoroda <chalkerx@gmail.com>

Author: 3 people

lib/dispatcher/socks5-proxy-agent.js

@@ -17,7 +17,7 @@ const debug = debuglog('undici:socks5-proxy')
 const kProxyUrl = Symbol('proxy url')
 const kProxyHeaders = Symbol('proxy headers')
 const kProxyAuth = Symbol('proxy auth')
-const kPool = Symbol('pool')
+const kPools = Symbol('pools')
 const kConnector = Symbol('connector')
 
 // Static flag to ensure warning is only emitted once per process
@@ -65,8 +65,8 @@ class Socks5ProxyAgent extends DispatcherBase {
       servername: options.proxyTls?.servername || url.hostname
     })
 
-    // Pool for the actual HTTP connections (with SOCKS5 tunnel connect function)
-    this[kPool] = null
+    // Pools for the actual HTTP connections (with SOCKS5 tunnel connect function), keyed by origin
+    this[kPools] = new Map()
   }
 
   /**
@@ -183,9 +183,11 @@ class Socks5ProxyAgent extends DispatcherBase {
     debug('dispatching request to', origin, 'via SOCKS5')
 
     try {
-      // Create Pool with custom connect function if we don't have one yet
-      if (!this[kPool] || this[kPool].destroyed || this[kPool].closed) {
-        this[kPool] = new Pool(origin, {
+      const originKey = String(origin)
+      let pool = this[kPools].get(originKey)
+      // Create a Pool per origin so requests are not routed to the wrong host
+      if (!pool || pool.destroyed || pool.closed) {
+        pool = new Pool(origin, {
           pipelining: opts.pipelining,
           connections: opts.connections,
           connect: async (connectOpts, callback) => {
@@ -225,10 +227,11 @@ class Socks5ProxyAgent extends DispatcherBase {
             }
           }
         })
+        this[kPools].set(originKey, pool)
       }
 
-      // Dispatch the request through the pool
-      return this[kPool][kDispatch](opts, handler)
+      // Dispatch the request through the per-origin pool
+      return pool[kDispatch](opts, handler)
     } catch (err) {
       debug('dispatch error:', err)
       if (typeof handler.onError === 'function') {
@@ -240,15 +243,21 @@ class Socks5ProxyAgent extends DispatcherBase {
   }
 
   async [kClose] () {
-    if (this[kPool]) {
-      await this[kPool].close()
+    const closePromises = []
+    for (const pool of this[kPools].values()) {
+      closePromises.push(pool.close())
     }
+    this[kPools].clear()
+    await Promise.all(closePromises)
   }
 
   async [kDestroy] (err) {
-    if (this[kPool]) {
-      await this[kPool].destroy(err)
+    const destroyPromises = []
+    for (const pool of this[kPools].values()) {
+      destroyPromises.push(pool.destroy(err))
     }
+    this[kPools].clear()
+    await Promise.all(destroyPromises)
   }
 }
 

test/socks5-proxy-agent.js

@@ -225,6 +225,48 @@ test('Socks5ProxyAgent - multiple requests through same proxy', async (t) => {
   await p.completed
 })
 
+test('Socks5ProxyAgent - requests to different origins are routed correctly', async (t) => {
+  const p = tspl(t, { plan: 4 })
+
+  // Create two distinct target servers
+  const serverA = createServer((req, res) => {
+    res.writeHead(200, { 'content-type': 'application/json' })
+    res.end(JSON.stringify({ server: 'A', path: req.url }))
+  })
+  const serverB = createServer((req, res) => {
+    res.writeHead(200, { 'content-type': 'application/json' })
+    res.end(JSON.stringify({ server: 'B', path: req.url }))
+  })
+
+  await new Promise((resolve) => serverA.listen(0, '127.0.0.1', resolve))
+  await new Promise((resolve) => serverB.listen(0, '127.0.0.1', resolve))
+  const portA = serverA.address().port
+  const portB = serverB.address().port
+
+  const socksServer = new TestSocks5Server()
+  const socksAddress = await socksServer.listen()
+
+  try {
+    const proxyWrapper = new Socks5ProxyAgent(`socks5://127.0.0.1:${socksAddress.port}`)
+
+    // First request goes to server A — establishes a pool
+    const respA = await request(`http://127.0.0.1:${portA}/a`, { dispatcher: proxyWrapper })
+    p.equal(respA.statusCode, 200)
+    p.deepEqual(await respA.body.json(), { server: 'A', path: '/a' })
+
+    // Second request goes to server B — must NOT reuse the pool from origin A
+    const respB = await request(`http://127.0.0.1:${portB}/b`, { dispatcher: proxyWrapper })
+    p.equal(respB.statusCode, 200)
+    p.deepEqual(await respB.body.json(), { server: 'B', path: '/b' }, 'request to origin B must reach server B, not server A')
+  } finally {
+    await socksServer.close()
+    serverA.close()
+    serverB.close()
+  }
+
+  await p.completed
+})
+
 test('Socks5ProxyAgent - connection failure', async (t) => {
   const p = tspl(t, { plan: 1 })