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fix: SSRF in /api/parse-url via DNS bypass and redirects (#878)

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* fix: resolve DNS before SSRF check and block redirects in parse-url

isPrivateUrl() did string-only hostname matching and never resolved DNS,
so a public-looking name that maps to an internal IP (e.g.
127-0-0-1.sslip.io -> 127.0.0.1) passed the check while fetch/extract
later resolved it and reached internal services (GHSA-wqcv-5qvx-vx75).

- isPrivateUrl is now async: it keeps the fast string/literal-IP path,
  then resolves the hostname via DNS and rejects if any address is private.
- parse-url now fetches the page itself with redirect: "error" and parses
  via extractFromHtml(), since article-extractor follows redirects
  internally and drops a redirect option, which allowed a public URL to
  302 to an internal host.
- Update validate-model call site to await; add regression tests.

* fix: preserve charset detection and block CGNAT range in parse-url SSRF fix

Follow-up to the multi-reviewer review of the SSRF fix:

- Restore charset handling lost when switching from extract() to
  response.text(): non-UTF-8 pages (Shift_JIS/GBK/EUC/Big5, common on CJK
  sites this project targets) decoded as mojibake. Now read the body as
  bytes, detect charset from Content-Type / <meta charset>, and decode
  with TextDecoder before extractFromHtml.
- Wrap extractFromHtml in try/catch: it throws (not returns null) on
  empty/non-HTML bodies, which previously surfaced as a 500 instead of the
  intended 400.
- Add 100.64.0.0/10 (RFC 6598 CGNAT) to isPrivateIp; it is routable inside
  some cloud internal networks and was a residual SSRF target.
- Add tests for CGNAT, its boundaries, 0.0.0.0, and DNS-resolved IPv6.
This commit is contained in:
Dayuan Jiang
2026-06-28 12:41:29 +09:00
committed by GitHub
parent 80baf43827
commit 5bfd7b2468
4 changed files with 234 additions and 109 deletions
Download Patch File Download Diff File Expand all files Collapse all files
app/api/parse-url/route.ts
+67 -28
View File
@@ -1,4 +1,4 @@
import { extract } from "@extractus/article-extractor"
import { extractFromHtml } from "@extractus/article-extractor"
import { NextResponse } from "next/server"
import TurndownService from "turndown"
import { isPrivateUrl } from "@/lib/ssrf-protection"
@@ -7,6 +7,31 @@ const MAX_CONTENT_LENGTH = 150000 // Match PDF limit
const EXTRACT_TIMEOUT_MS = 15000
const USER_AGENT = "Mozilla/5.0 (compatible; NextAIDrawio/1.0)"
// Detect the page's charset so non-UTF-8 pages (Shift_JIS/GBK/EUC/Big5, common
// on CJK sites) are decoded correctly. Response.text() always assumes UTF-8 and
// would produce mojibake; the article-extractor library does the same detection
// when it fetches the page itself, which we no longer rely on.
function detectCharset(
contentType: string | null,
buffer: ArrayBuffer,
): string {
// 1. HTTP Content-Type header charset (most authoritative).
const headerCharset = contentType?.match(/charset=([^;]+)/i)?.[1]?.trim()
// 2. <meta charset> / <meta http-equiv> in the first bytes of the document.
const head = new TextDecoder("utf-8").decode(buffer.slice(0, 4096))
const metaCharset =
head.match(/<meta[^>]+charset=["']?\s*([\w-]+)/i)?.[1] ||
head.match(/<meta[^>]+content=["'][^"']*charset=([\w-]+)/i)?.[1]
const charset = (headerCharset || metaCharset || "utf-8").toLowerCase()
// TextDecoder throws on unknown encoding labels; fall back to UTF-8.
try {
new TextDecoder(charset)
return charset
} catch {
return "utf-8"
}
}
export async function POST(req: Request) {
try {
const { url } = await req.json()
@@ -31,21 +56,31 @@ export async function POST(req: Request) {
// SSRF protection: parse-url has no use case for fetching internal
// hosts, so private URLs are always rejected. ALLOW_PRIVATE_URLS only
// governs LLM provider baseUrl overrides (validate-model, chat).
if (isPrivateUrl(url)) {
if (await isPrivateUrl(url)) {
return NextResponse.json(
{ error: "Cannot access private/internal URLs" },
{ status: 400 },
)
}
const headController = new AbortController()
const headTimeout = setTimeout(() => headController.abort(), 3000)
// Fetch the page ourselves so we control redirect handling. The
// article-extractor library follows redirects internally and ignores a
// `redirect` option, which would let a public URL 302 to an internal
// host and bypass the SSRF check above. `redirect: "error"` rejects any
// redirect outright.
const controller = new AbortController()
const timeoutId = setTimeout(() => {
controller.abort()
}, EXTRACT_TIMEOUT_MS)
let html: string
try {
const headResponse = await fetch(url, {
method: "HEAD",
const response = await fetch(url, {
headers: { "User-Agent": USER_AGENT },
signal: headController.signal,
redirect: "error",
signal: controller.signal,
})
const contentType = headResponse.headers.get("content-type")
const contentType = response.headers.get("content-type")
if (contentType?.includes("application/pdf")) {
return NextResponse.json(
{
@@ -54,27 +89,17 @@ export async function POST(req: Request) {
{ status: 422 },
)
}
} catch (err) {
console.warn(
"HEAD pre-check failed, proceeding with extraction:",
err,
)
} finally {
clearTimeout(headTimeout)
}
// Extract article content with timeout to avoid tying up server resources
const controller = new AbortController()
const timeoutId = setTimeout(() => {
controller.abort()
}, EXTRACT_TIMEOUT_MS)
if (!response.ok) {
return NextResponse.json(
{ error: "Could not fetch URL content" },
{ status: 400 },
)
}
let article
try {
article = await extract(url, undefined, {
headers: { "User-Agent": USER_AGENT },
signal: controller.signal,
})
const buffer = await response.arrayBuffer()
const charset = detectCharset(contentType, buffer)
html = new TextDecoder(charset).decode(buffer)
} catch (err: any) {
if (err?.name === "AbortError") {
return NextResponse.json(
@@ -82,11 +107,25 @@ export async function POST(req: Request) {
{ status: 504 },
)
}
throw err
// Redirects are rejected with a TypeError ("failed to fetch" /
// "unexpected redirect") when redirect: "error" is set.
return NextResponse.json(
{ error: "Could not fetch URL content" },
{ status: 400 },
)
} finally {
clearTimeout(timeoutId)
}
// extractFromHtml throws (not returns null) on empty/non-HTML bodies,
// so map any parse error to the same 400 as the no-content case.
let article: Awaited<ReturnType<typeof extractFromHtml>>
try {
article = await extractFromHtml(html, url)
} catch {
article = null
}
if (!article || !article.content) {
return NextResponse.json(
{ error: "Could not extract content from URL" },
app/api/validate-model/route.ts
+1 -1
View File
@@ -56,7 +56,7 @@ export async function POST(req: Request) {
}
// SECURITY: Block SSRF attacks via custom baseUrl
if (baseUrl && !allowPrivateUrls() && isPrivateUrl(baseUrl)) {
if (baseUrl && !allowPrivateUrls() && (await isPrivateUrl(baseUrl))) {
return NextResponse.json(
{ valid: false, error: "Invalid base URL" },
{ status: 400 },
lib/ssrf-protection.ts
+94 -66
View File
@@ -2,80 +2,108 @@
* SSRF (Server-Side Request Forgery) protection utilities
*/
import { lookup } from "node:dns/promises"
/**
* Check if URL points to private/internal network
* Blocks: localhost, private IPs, link-local, AWS metadata service
* Check if an IP address (IPv4 or IPv6) belongs to a private/internal range.
* Works for both user-supplied literal IPs and DNS-resolved addresses.
*/
export function isPrivateUrl(urlString: string): boolean {
function isPrivateIp(ip: string): boolean {
const addr = ip.toLowerCase().replace(/^\[|\]$/g, "")
// IPv6
if (addr.includes(":")) {
if (addr === "::1" || addr === "::") return true
// unique-local (fc00::/7) and IPv4-mapped (::ffff:0:0/96)
if (
addr.startsWith("fc") ||
addr.startsWith("fd") ||
addr.startsWith("::ffff:")
) {
return true
}
// link-local (fe80::/10)
const linkLocal = addr.match(/^fe([0-9a-f]{2}):/)
if (linkLocal) {
const high = parseInt(linkLocal[1], 16)
if (high >= 0x80 && high <= 0xbf) return true
}
return false
}
// IPv4
const ipv4Match = addr.match(/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/)
if (ipv4Match) {
const [, a, b] = ipv4Match.map(Number)
if (a === 10) return true // 10.0.0.0/8
if (a === 172 && b >= 16 && b <= 31) return true // 172.16.0.0/12
if (a === 192 && b === 168) return true // 192.168.0.0/16
if (a === 169 && b === 254) return true // 169.254.0.0/16 (link-local)
if (a === 127) return true // 127.0.0.0/8 (loopback)
if (a === 0) return true // 0.0.0.0/8
if (a === 100 && b >= 64 && b <= 127) return true // 100.64.0.0/10 (CGNAT, used by some cloud internal networks)
}
return false
}
/**
* String-only check against well-known private hostnames and literal IPs.
* Fast path that avoids a DNS lookup for obvious cases.
*/
function isPrivateHostname(hostname: string): boolean {
const host = hostname
.toLowerCase()
.replace(/^\[|\]$/g, "")
.replace(/\.$/, "")
if (
host === "localhost" ||
host === "127.0.0.1" ||
host === "::1" ||
host === "::"
) {
return true
}
if (host === "169.254.169.254" || host === "metadata.google.internal") {
return true
}
if (
host.endsWith(".local") ||
host.endsWith(".internal") ||
host.endsWith(".localhost")
) {
return true
}
// Literal IP supplied directly in the URL
return isPrivateIp(host)
}
/**
* Check if URL points to private/internal network.
* Blocks: localhost, private IPs, link-local, AWS metadata service.
*
* Resolves the hostname via DNS and validates every returned address, so
* public-looking names that map to internal IPs (e.g. "127-0-0-1.sslip.io")
* are caught even though they pass the string-only check.
*/
export async function isPrivateUrl(urlString: string): Promise<boolean> {
try {
const url = new URL(urlString)
// Strip a trailing dot so FQDN forms like "localhost." (which still
// resolve to 127.0.0.1) cannot bypass the equality checks below.
const hostname = url.hostname
.toLowerCase()
.replace(/^\[|\]$/g, "")
.replace(/\.$/, "")
// Block localhost
if (
hostname === "localhost" ||
hostname === "127.0.0.1" ||
hostname === "::1" ||
hostname === "::"
) {
return true
}
// Fast path: obvious string matches and literal IPs.
if (isPrivateHostname(hostname)) return true
// Block IPv6 unique-local (fc00::/7), link-local (fe80::/10),
// and IPv4-mapped (::ffff:0:0/96) hosts.
if (hostname.includes(":")) {
if (
hostname.startsWith("fc") ||
hostname.startsWith("fd") ||
hostname.startsWith("::ffff:")
) {
return true
}
const linkLocal = hostname.match(/^fe([0-9a-f]{2}):/)
if (linkLocal) {
const high = parseInt(linkLocal[1], 16)
if (high >= 0x80 && high <= 0xbf) return true
}
}
// Block AWS/cloud metadata endpoints
if (
hostname === "169.254.169.254" ||
hostname === "metadata.google.internal"
) {
return true
}
// Check for private IPv4 ranges
const ipv4Match = hostname.match(
/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/,
)
if (ipv4Match) {
const [, a, b] = ipv4Match.map(Number)
if (a === 10) return true // 10.0.0.0/8
if (a === 172 && b >= 16 && b <= 31) return true // 172.16.0.0/12
if (a === 192 && b === 168) return true // 192.168.0.0/16
if (a === 169 && b === 254) return true // 169.254.0.0/16 (link-local)
if (a === 127) return true // 127.0.0.0/8 (loopback)
}
// Block common internal hostnames
if (
hostname.endsWith(".local") ||
hostname.endsWith(".internal") ||
hostname.endsWith(".localhost")
) {
return true
}
return false
// Resolve DNS and reject if any address is private.
const stripped = hostname.replace(/^\[|\]$/g, "").replace(/\.$/, "")
const addresses = await lookup(stripped, { all: true })
return addresses.some(({ address }) => isPrivateIp(address))
} catch {
return true // Invalid URL - block it
return true // Invalid URL or DNS failure - block it
}
}
tests/unit/ssrf-protection.test.ts
+72 -14
View File
@@ -1,21 +1,79 @@
import { describe, expect, it } from "vitest"
import { beforeEach, describe, expect, it, vi } from "vitest"
import { isPrivateUrl } from "@/lib/ssrf-protection"
// Mock DNS so tests are deterministic and never hit the network.
const lookupMock = vi.hoisted(() => vi.fn())
vi.mock("node:dns/promises", () => ({
default: { lookup: lookupMock },
lookup: lookupMock,
}))
describe("isPrivateUrl", () => {
it("blocks private IPv6 URLs", () => {
expect(isPrivateUrl("http://[::1]/")).toBe(true)
expect(isPrivateUrl("http://[0:0:0:0:0:0:0:1]/")).toBe(true)
expect(isPrivateUrl("http://[::]/")).toBe(true)
expect(isPrivateUrl("http://[::ffff:127.0.0.1]/")).toBe(true)
expect(isPrivateUrl("http://[fc00::1]/")).toBe(true)
expect(isPrivateUrl("http://[fd12:3456:789a::1]/")).toBe(true)
expect(isPrivateUrl("http://[fe80::1]/")).toBe(true)
expect(isPrivateUrl("http://[fe9f::1]/")).toBe(true)
expect(isPrivateUrl("http://[febf::1]/")).toBe(true)
beforeEach(() => {
lookupMock.mockReset()
})
it("allows public URLs", () => {
expect(isPrivateUrl("https://example.com/article")).toBe(false)
expect(isPrivateUrl("https://fc00.example.com/article")).toBe(false)
it("blocks private IPv6 URLs (string-only fast path, no DNS)", async () => {
expect(await isPrivateUrl("http://[::1]/")).toBe(true)
expect(await isPrivateUrl("http://[0:0:0:0:0:0:0:1]/")).toBe(true)
expect(await isPrivateUrl("http://[::]/")).toBe(true)
expect(await isPrivateUrl("http://[::ffff:127.0.0.1]/")).toBe(true)
expect(await isPrivateUrl("http://[fc00::1]/")).toBe(true)
expect(await isPrivateUrl("http://[fd12:3456:789a::1]/")).toBe(true)
expect(await isPrivateUrl("http://[fe80::1]/")).toBe(true)
expect(await isPrivateUrl("http://[fe9f::1]/")).toBe(true)
expect(await isPrivateUrl("http://[febf::1]/")).toBe(true)
expect(lookupMock).not.toHaveBeenCalled()
})
it("blocks literal private IPv4 without DNS", async () => {
expect(await isPrivateUrl("http://127.0.0.1/")).toBe(true)
expect(await isPrivateUrl("http://10.0.0.5/")).toBe(true)
expect(await isPrivateUrl("http://192.168.1.1/")).toBe(true)
expect(await isPrivateUrl("http://169.254.169.254/")).toBe(true)
expect(await isPrivateUrl("http://0.0.0.0/")).toBe(true)
// 100.64.0.0/10 CGNAT (RFC 6598), routable in some cloud internal nets
expect(await isPrivateUrl("http://100.64.0.1/")).toBe(true)
expect(await isPrivateUrl("http://100.127.255.255/")).toBe(true)
expect(lookupMock).not.toHaveBeenCalled()
})
it("treats CGNAT boundaries correctly", async () => {
// 100.63.x and 100.128.x are outside 100.64.0.0/10 → public
lookupMock.mockResolvedValue([{ address: "100.63.255.255", family: 4 }])
expect(await isPrivateUrl("http://just-below.example/")).toBe(false)
lookupMock.mockResolvedValue([{ address: "100.128.0.1", family: 4 }])
expect(await isPrivateUrl("http://just-above.example/")).toBe(false)
})
it("blocks a hostname that resolves to a private IPv6 address", async () => {
lookupMock.mockResolvedValue([{ address: "fd00::1", family: 6 }])
expect(await isPrivateUrl("http://v6.example.com/")).toBe(true)
})
it("allows public URLs that resolve to public IPs", async () => {
lookupMock.mockResolvedValue([{ address: "93.184.216.34", family: 4 }])
expect(await isPrivateUrl("https://example.com/article")).toBe(false)
})
it("blocks public-looking hostnames that resolve to a private IP (DNS-rebinding-style bypass)", async () => {
// e.g. 127-0-0-1.sslip.io resolves to 127.0.0.1
lookupMock.mockResolvedValue([{ address: "127.0.0.1", family: 4 }])
expect(await isPrivateUrl("http://127-0-0-1.sslip.io/")).toBe(true)
})
it("blocks when any resolved address is private", async () => {
lookupMock.mockResolvedValue([
{ address: "93.184.216.34", family: 4 },
{ address: "10.1.2.3", family: 4 },
])
expect(await isPrivateUrl("http://mixed.example.com/")).toBe(true)
})
it("blocks when DNS resolution fails", async () => {
lookupMock.mockRejectedValue(new Error("ENOTFOUND"))
expect(await isPrivateUrl("http://does-not-resolve.example/")).toBe(
true,
)
})
})