Reject next image urls in image optimizer

packages/next/src/lib/url.ts

@@ -6,6 +6,14 @@ export function isFullStringUrl(url: string) {
   return /https?:\/\//.test(url)
 }
 
+export function parseUrl(url: string): URL | undefined {
+  let parsed = undefined
+  try {
+    parsed = new URL(url, DUMMY_ORIGIN)
+  } catch {}
+  return parsed
+}
+
 export function stripNextRscUnionQuery(relativeUrl: string): string {
   const urlInstance = new URL(relativeUrl, DUMMY_ORIGIN)
   urlInstance.searchParams.delete(NEXT_RSC_UNION_QUERY)

packages/next/src/server/image-optimizer.ts

@@ -22,6 +22,7 @@ import { sendEtagResponse } from './send-payload'
 import { getContentType, getExtension } from './serve-static'
 import * as Log from '../build/output/log'
 import isError from '../lib/is-error'
+import { parseUrl } from '../lib/url'
 
 type XCacheHeader = 'MISS' | 'HIT' | 'STALE'
 
@@ -213,9 +214,13 @@ export class ImageOptimizerCache {
       }
     }
 
-    if (url.startsWith('/_next/image')) {
-      return {
-        errorMessage: '"url" parameter cannot be recursive',
+    const parsedUrl = parseUrl(url)
+    if (parsedUrl) {
+      const decodedPathname = decodeURIComponent(parsedUrl.pathname)
+      if (/\/_next\/image($|\/)/.test(decodedPathname)) {
+        return {
+          errorMessage: '"url" parameter cannot be recursive',
+        }
       }
     }
 

test/integration/image-optimizer/test/util.ts

@@ -8,6 +8,7 @@ import {
   fetchViaHTTP,
   File,
   findPort,
+  getFetchUrl,
   killApp,
   launchApp,
   nextBuild,
@@ -1021,11 +1022,46 @@ export function runTests(ctx: RunTestsCtx) {
     )
   })
 
-  it('should fail when url is recursive', async () => {
-    const query = { url: `/_next/image?url=test.pngw=1&q=1`, w: ctx.w, q: 1 }
-    const res = await fetchViaHTTP(ctx.appPort, '/_next/image', query, {})
-    expect(res.status).toBe(400)
-    expect(await res.text()).toBe(`"url" parameter cannot be recursive`)
+  describe('recursive url is not allowed', () => {
+    it('should fail with relative next image url', async () => {
+      const query = { url: `/_next/image?url=test.pngw=1&q=1`, w: ctx.w, q: 1 }
+      const res = await fetchViaHTTP(ctx.appPort, '/_next/image', query, {})
+      expect(res.status).toBe(400)
+      expect(await res.text()).toBe(`"url" parameter cannot be recursive`)
+    })
+
+    it('should fail with encoded relative image url', async () => {
+      const query = {
+        url: '%2F_next%2Fimage%3Furl%3Dtest.pngw%3D1%26q%3D1',
+        w: ctx.w,
+        q: 1,
+      }
+      const res = await fetchViaHTTP(ctx.appPort, '/_next/image', query, {})
+      expect(res.status).toBe(400)
+      expect(await res.text()).toBe(`"url" parameter is invalid`)
+    })
+
+    it('should fail with absolute next image url', async () => {
+      const fullUrl = getFetchUrl(
+        ctx.appPort,
+        '/_next/image?url=test.pngw=1&q=1'
+      )
+      const query = { url: fullUrl, w: ctx.w, q: 1 }
+      const res = await fetchViaHTTP(ctx.appPort, '/_next/image', query, {})
+      expect(res.status).toBe(400)
+      expect(await res.text()).toBe(`"url" parameter cannot be recursive`)
+    })
+
+    it('should fail with relative image url with assetPrefix', async () => {
+      const fullUrl = getFetchUrl(
+        ctx.appPort,
+        `/assets/_next/image?url=test.pngw=1&q=1`
+      )
+      const query = { url: fullUrl, w: ctx.w, q: 1 }
+      const res = await fetchViaHTTP(ctx.appPort, '/_next/image', query, {})
+      expect(res.status).toBe(400)
+      expect(await res.text()).toBe(`"url" parameter cannot be recursive`)
+    })
   })
 
   it('should fail when internal url is not an image', async () => {

test/lib/next-test-utils.ts

@@ -158,6 +158,15 @@ export function withQuery(
   return `${pathname}?${querystring}`
 }
 
+export function getFetchUrl(
+  appPort: string | number,
+  pathname: string,
+  query?: Record<string, any> | string | null | undefined
+) {
+  const url = query ? withQuery(pathname, query) : pathname
+  return getFullUrl(appPort, url)
+}
+
 export function fetchViaHTTP(
   appPort: string | number,
   pathname: string,