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fix(image): pin DNS-resolved IP to prevent SSRF via DNS rebinding (GHSA-cmhj-wh2f-9cgx)

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Co-authored-by: Cursor <cursoragent@cursor.com>
This commit is contained in:
decolua
2026-06-17 11:02:04 +07:00
parent 7ae9fff663
commit c7d07448c5
1 changed files with 18 additions and 8 deletions
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26
open-sse/translator/concerns/image.js
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@@ -13,6 +13,7 @@ export function parseDataUri(url) {
} }
import { lookup } from "node:dns/promises"; import { lookup } from "node:dns/promises";
import { Agent } from "undici";
import { MAX_IMAGE_BYTES, FETCH_TIMEOUT_MS, IMAGE_SIGNATURES, BLOCKED_HOSTS } from "../../config/mediaConfig.js"; import { MAX_IMAGE_BYTES, FETCH_TIMEOUT_MS, IMAGE_SIGNATURES, BLOCKED_HOSTS } from "../../config/mediaConfig.js";
// True if an IPv4/IPv6 address is private/reserved (SSRF target). // True if an IPv4/IPv6 address is private/reserved (SSRF target).
@@ -33,14 +34,16 @@ function isPrivateIp(ip) {
return false; return false;
} }
// Resolve host and reject if it points at a private/blocked address (SSRF guard). // Resolve host once and return only public IPs (SSRF guard).
async function assertPublicHost(hostname) { // Rejects if any resolved record is private/reserved (defeats multi-A tricks).
if (!hostname || BLOCKED_HOSTS.has(hostname.toLowerCase())) return false; async function resolvePinnedIps(hostname) {
if (!hostname || BLOCKED_HOSTS.has(hostname.toLowerCase())) return null;
try { try {
const { address } = await lookup(hostname); const records = await lookup(hostname, { all: true });
return !isPrivateIp(address); if (!records.length || records.some((r) => isPrivateIp(r.address))) return null;
return records;
} catch { } catch {
return false; return null;
} }
} }
@@ -78,15 +81,21 @@ export async function fetchImageAsBase64(imageUrl, options = {}) {
let url; let url;
try { url = new URL(imageUrl); } catch { return null; } try { url = new URL(imageUrl); } catch { return null; }
if (!(await assertPublicHost(url.hostname))) return null; const pinnedIps = await resolvePinnedIps(url.hostname);
if (!pinnedIps) return null;
const controller = new AbortController(); const controller = new AbortController();
const timeout = signal ? null : setTimeout(() => controller.abort(), timeoutMs); const timeout = signal ? null : setTimeout(() => controller.abort(), timeoutMs);
const fetchSignal = signal || controller.signal; const fetchSignal = signal || controller.signal;
// Pin connect to the validated IP so no second DNS resolution can rebind (TOCTOU fix).
const dispatcher = new Agent({
connect: { lookup: (_h, _o, cb) => cb(null, [{ address: pinnedIps[0].address, family: pinnedIps[0].family }]) },
});
try { try {
// redirect:"manual" prevents a public URL redirecting to a private one (SSRF bypass). // redirect:"manual" prevents a public URL redirecting to a private one (SSRF bypass).
const response = await fetch(imageUrl, { signal: fetchSignal, redirect: "manual" }); const response = await fetch(imageUrl, { signal: fetchSignal, redirect: "manual", dispatcher });
if (!response.ok || !response.body) return null; if (!response.ok || !response.body) return null;
// Stream-read with a hard byte cap to avoid loading huge payloads into memory. // Stream-read with a hard byte cap to avoid loading huge payloads into memory.
@@ -110,5 +119,6 @@ export async function fetchImageAsBase64(imageUrl, options = {}) {
return null; return null;
} finally { } finally {
if (timeout) clearTimeout(timeout); if (timeout) clearTimeout(timeout);
dispatcher.close().catch(() => {});
} }
} }