�����������add support for images CSP, disposition, and allow SVG� (#776)

Co-authored-by: Magnus Dahl Eide <magnus@dahleide.com>

Author: vicb

.changeset/mean-sloths-sit.md

@@ -0,0 +1,5 @@
+---
+"@opennextjs/cloudflare": patch
+---
+
+Add support for images CSP, disposition, and allow SVG

packages/cloudflare/src/cli/build/open-next/compile-images.ts

@@ -18,6 +18,16 @@ export async function compileImages(options: BuildOptions) {
 		? JSON.parse(fs.readFileSync(imagesManifestPath, { encoding: "utf-8" }))
 		: {};
 
+	const __IMAGES_REMOTE_PATTERNS__ = JSON.stringify(imagesManifest?.images?.remotePatterns ?? []);
+	const __IMAGES_LOCAL_PATTERNS__ = JSON.stringify(imagesManifest?.images?.localPatterns ?? []);
+	const __IMAGES_ALLOW_SVG__ = JSON.stringify(Boolean(imagesManifest?.images?.dangerouslyAllowSVG));
+	const __IMAGES_CONTENT_SECURITY_POLICY__ = JSON.stringify(
+		imagesManifest?.images?.contentSecurityPolicy ?? "script-src 'none'; frame-src 'none'; sandbox;"
+	);
+	const __IMAGES_CONTENT_DISPOSITION__ = JSON.stringify(
+		imagesManifest?.images?.contentDispositionType ?? "attachment"
+	);
+
 	await build({
 		entryPoints: [imagesPath],
 		outdir: path.join(options.outputDir, "cloudflare"),
@@ -27,8 +37,11 @@ export async function compileImages(options: BuildOptions) {
 		target: "esnext",
 		platform: "node",
 		define: {
-			__IMAGES_REMOTE_PATTERNS__: JSON.stringify(imagesManifest?.images?.remotePatterns ?? []),
-			__IMAGES_LOCAL_PATTERNS__: JSON.stringify(imagesManifest?.images?.localPatterns ?? []),
+			__IMAGES_REMOTE_PATTERNS__,
+			__IMAGES_LOCAL_PATTERNS__,
+			__IMAGES_ALLOW_SVG__,
+			__IMAGES_CONTENT_SECURITY_POLICY__,
+			__IMAGES_CONTENT_DISPOSITION__,
 		},
 	});
 }

packages/cloudflare/src/cli/templates/images.ts

@@ -19,7 +19,7 @@ export type LocalPattern = {
  * Local images (starting with a '/' as fetched using the passed fetcher).
  * Remote images should match the configured remote patterns or a 404 response is returned.
  */
-export function fetchImage(fetcher: Fetcher | undefined, imageUrl: string) {
+export async function fetchImage(fetcher: Fetcher | undefined, imageUrl: string, ctx: ExecutionContext) {
 	// https://github.com/vercel/next.js/blob/d76f0b1/packages/next/src/server/image-optimizer.ts#L208
 	if (!imageUrl || imageUrl.length > 3072 || imageUrl.startsWith("//")) {
 		return getUrlErrorResponse();
@@ -69,7 +69,45 @@ export function fetchImage(fetcher: Fetcher | undefined, imageUrl: string) {
 		return getUrlErrorResponse();
 	}
 
-	return fetch(imageUrl, { cf: { cacheEverything: true } });
+	const imgResponse = await fetch(imageUrl, { cf: { cacheEverything: true } });
+
+	if (!imgResponse.body) {
+		return imgResponse;
+	}
+
+	const buffer = new ArrayBuffer(32);
+
+	try {
+		let contentType: string | undefined;
+		// body1 is eventually used for the response
+		// body2 is used to detect the content type
+		const [body1, body2] = imgResponse.body.tee();
+		const reader = body2.getReader({ mode: "byob" });
+		const { value } = await reader.read(new Uint8Array(buffer));
+		// Release resources by calling `reader.cancel()`
+		// `ctx.waitUntil` keeps the runtime running until the promise settles without having to wait here.
+		ctx.waitUntil(reader.cancel());
+
+		if (value) {
+			contentType = detectContentType(value);
+		}
+
+		if (contentType && !(contentType === SVG && !__IMAGES_ALLOW_SVG__)) {
+			const headers = new Headers(imgResponse.headers);
+			headers.set("content-type", contentType);
+			headers.set("content-disposition", __IMAGES_CONTENT_DISPOSITION__);
+			headers.set("content-security-policy", __IMAGES_CONTENT_SECURITY_POLICY__);
+			return new Response(body1, { ...imgResponse, headers });
+		}
+
+		return new Response('"url" parameter is valid but image type is not allowed', {
+			status: 400,
+		});
+	} catch {
+		return new Response('"url" parameter is valid but upstream response is invalid', {
+			status: 400,
+		});
+	}
 }
 
 export function matchRemotePattern(pattern: RemotePattern, url: URL): boolean {
@@ -113,9 +151,67 @@ function getUrlErrorResponse() {
 	return new Response(`"url" parameter is not allowed`, { status: 400 });
 }
 
+const AVIF = "image/avif";
+const WEBP = "image/webp";
+const PNG = "image/png";
+const JPEG = "image/jpeg";
+const GIF = "image/gif";
+const SVG = "image/svg+xml";
+const ICO = "image/x-icon";
+const ICNS = "image/x-icns";
+const TIFF = "image/tiff";
+const BMP = "image/bmp";
+
+/**
+ * Detects the content type by looking at the first few bytes of a file
+ *
+ * Based on https://github.com/vercel/next.js/blob/72c9635/packages/next/src/server/image-optimizer.ts#L155
+ *
+ * @param buffer The image bytes
+ * @returns a content type of undefined for unsupported content
+ */
+export function detectContentType(buffer: Uint8Array) {
+	if ([0xff, 0xd8, 0xff].every((b, i) => buffer[i] === b)) {
+		return JPEG;
+	}
+	if ([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a].every((b, i) => buffer[i] === b)) {
+		return PNG;
+	}
+	if ([0x47, 0x49, 0x46, 0x38].every((b, i) => buffer[i] === b)) {
+		return GIF;
+	}
+	if ([0x52, 0x49, 0x46, 0x46, 0, 0, 0, 0, 0x57, 0x45, 0x42, 0x50].every((b, i) => !b || buffer[i] === b)) {
+		return WEBP;
+	}
+	if ([0x3c, 0x3f, 0x78, 0x6d, 0x6c].every((b, i) => buffer[i] === b)) {
+		return SVG;
+	}
+	if ([0x3c, 0x73, 0x76, 0x67].every((b, i) => buffer[i] === b)) {
+		return SVG;
+	}
+	if ([0, 0, 0, 0, 0x66, 0x74, 0x79, 0x70, 0x61, 0x76, 0x69, 0x66].every((b, i) => !b || buffer[i] === b)) {
+		return AVIF;
+	}
+	if ([0x00, 0x00, 0x01, 0x00].every((b, i) => buffer[i] === b)) {
+		return ICO;
+	}
+	if ([0x69, 0x63, 0x6e, 0x73].every((b, i) => buffer[i] === b)) {
+		return ICNS;
+	}
+	if ([0x49, 0x49, 0x2a, 0x00].every((b, i) => buffer[i] === b)) {
+		return TIFF;
+	}
+	if ([0x42, 0x4d].every((b, i) => buffer[i] === b)) {
+		return BMP;
+	}
+}
+
 /* eslint-disable no-var */
 declare global {
 	var __IMAGES_REMOTE_PATTERNS__: RemotePattern[];
 	var __IMAGES_LOCAL_PATTERNS__: LocalPattern[];
+	var __IMAGES_ALLOW_SVG__: boolean;
+	var __IMAGES_CONTENT_SECURITY_POLICY__: string;
+	var __IMAGES_CONTENT_DISPOSITION__: string;
 }
 /* eslint-enable no-var */

packages/cloudflare/src/cli/templates/worker.ts

@@ -41,7 +41,7 @@ export default {
 			// Fallback for the Next default image loader.
 			if (url.pathname === `${globalThis.__NEXT_BASE_PATH__}/_next/image`) {
 				const imageUrl = url.searchParams.get("url") ?? "";
-				return fetchImage(env.ASSETS, imageUrl);
+				return await fetchImage(env.ASSETS, imageUrl, ctx);
 			}
 
 			// - `Request`s are handled by the Next server