security: don't send referrer paths for images and bookmarks (#3881)

We're currently sending `referrer` with path for image/bookmark
requests. We shouldn't do that as it exposes the rooms to other servers.

## `<img>`
- `<img>` tags have the right referrerpolicy to be
`strict-origin-when-cross-origin`:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/img#referrerpolicy
- _however_, because we use React, it looks like react creates a raw DOM
node and adds properties one by one and it loses the default
referrerpolicy it would otherwise get! So, in `BookmarkShapeUtil` we
explicitly state the `referrerpolicy`
- `background-image` does the right thing 👍 
- _also_, I added this to places we do programmatic `new Image()`

## `fetch`
- _however_, fetch does not! wtf.
https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch

it's almost a footnote in this section of the docs
(https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch#supplying_request_options)
that `no-referrer-when-downgrade` is the default.

## `new Image()`
ugh, but _also_ doing a programmatic `new Image()` doesn't do the right
thing and we need to set the referrerpolicy here as well

### Change Type

<!-- ❗ Please select a 'Scope' label ❗️ -->

- [x] `sdk` — Changes the tldraw SDK
- [x] `dotcom` — Changes the tldraw.com web app
- [ ] `docs` — Changes to the documentation, examples, or templates.
- [ ] `vs code` — Changes to the vscode plugin
- [ ] `internal` — Does not affect user-facing stuff

<!-- ❗ Please select a 'Type' label ❗️ -->

- [x] `bugfix` — Bug fix
- [ ] `feature` — New feature
- [ ] `improvement` — Improving existing features
- [ ] `chore` — Updating dependencies, other boring stuff
- [ ] `galaxy brain` — Architectural changes
- [ ] `tests` — Changes to any test code
- [ ] `tools` — Changes to infrastructure, CI, internal scripts,
debugging tools, etc.
- [ ] `dunno` — I don't know


### Test Plan

1. Test on staging that referrer with path isn't being sent anymore.

### Release Notes

- Security: fix referrer being sent for bookmarks and images.

apps/dotcom/index.html

@@ -5,6 +5,7 @@
 
 		<link rel="manifest" href="/manifest.webmanifest" />
 
+		<meta name="referrer" content="strict-origin-when-cross-origin" />
 		<meta name="theme-color" content="#FFFFFF" data-rh="true" />
 		<meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover" />
 		<link rel="icon" type="image/svg+xml" href="/favicon.svg" />

apps/dotcom/src/utils/assetUrls.ts

@@ -17,6 +17,7 @@ function preloadIcon(url: string) {
 		;(image as any).fetchPriority = 'low'
 		image.onload = resolve
 		image.onerror = reject
+		image.referrerPolicy = 'strict-origin-when-cross-origin'
 		image.src = url
 	})
 }

apps/dotcom/src/utils/createAssetFromFile.ts

@@ -18,6 +18,7 @@ export async function createAssetFromFile({ file }: { type: 'file'; file: File }
 	await fetch(url, {
 		method: 'POST',
 		body: file,
+		referrerPolicy: 'strict-origin-when-cross-origin',
 	})
 
 	const assetId: TLAssetId = AssetRecordType.createId(getHashForString(url))

apps/dotcom/src/utils/createAssetFromUrl.ts

@@ -40,7 +40,11 @@ export async function createAssetFromUrl({ url }: { type: 'url'; url: string }):
 		let meta: { image: string; title: string; description: string }
 
 		try {
-			const resp = await fetch(url, { method: 'GET', mode: 'no-cors' })
+			const resp = await fetch(url, {
+				method: 'GET',
+				mode: 'no-cors',
+				referrerPolicy: 'strict-origin-when-cross-origin',
+			})
 			const html = await resp.text()
 			const doc = new DOMParser().parseFromString(html, 'text/html')
 			meta = {

apps/vscode/editor/src/utils/bookmarks.ts

@@ -30,7 +30,11 @@ export async function onCreateAssetFromUrl({
 		let meta: { image: string; title: string; description: string }
 
 		try {
-			const resp = await fetch(url, { method: 'GET', mode: 'no-cors' })
+			const resp = await fetch(url, {
+				method: 'GET',
+				mode: 'no-cors',
+				referrerPolicy: 'strict-origin-when-cross-origin',
+			})
 			const html = await resp.text()
 			const doc = new DOMParser().parseFromString(html, 'text/html')
 			meta = {

packages/tldraw/src/lib/defaultExternalContentHandlers.ts

@@ -113,7 +113,11 @@ export function registerDefaultExternalContentHandlers(
 		let meta: { image: string; title: string; description: string }
 
 		try {
-			const resp = await fetch(url, { method: 'GET', mode: 'no-cors' })
+			const resp = await fetch(url, {
+				method: 'GET',
+				mode: 'no-cors',
+				referrerPolicy: 'strict-origin-when-cross-origin',
+			})
 			const html = await resp.text()
 			const doc = new DOMParser().parseFromString(html, 'text/html')
 			meta = {

packages/tldraw/src/lib/shapes/bookmark/BookmarkShapeUtil.tsx

@@ -61,6 +61,7 @@ export class BookmarkShapeUtil extends BaseBoxShapeUtil<TLBookmarkShape> {
 							<img
 								className="tl-bookmark__image"
 								draggable={false}
+								referrerPolicy="strict-origin-when-cross-origin"
 								src={asset?.props.image}
 								alt={asset?.props.title || ''}
 							/>

packages/tldraw/src/lib/shapes/image/ImageShapeUtil.tsx

@@ -19,7 +19,7 @@ import { HyperlinkButton } from '../shared/HyperlinkButton'
 import { usePrefersReducedMotion } from '../shared/usePrefersReducedMotion'
 
 async function getDataURIFromURL(url: string): Promise<string> {
-	const response = await fetch(url)
+	const response = await fetch(url, { referrerPolicy: 'strict-origin-when-cross-origin' })
 	const blob = await response.blob()
 	return FileHelpers.blobToDataUrl(blob)
 }
@@ -85,6 +85,7 @@ export class ImageShapeUtil extends BaseBoxShapeUtil<TLImageShape> {
 					setStaticFrameSrc(canvas.toDataURL())
 				}
 				image.crossOrigin = 'anonymous'
+				image.referrerPolicy = 'strict-origin-when-cross-origin'
 				image.src = url
 
 				return () => {

packages/tldraw/src/lib/shapes/shared/defaultStyleDefs.tsx

@@ -28,7 +28,9 @@ export function getFontDefForExport(fontStyle: TLDefaultFontStyle): SvgExportDef
 			const fontFaceRule: string = (font as any).$$_fontface
 			if (!url || !fontFaceRule) return null
 
-			const fontFile = await (await fetch(url)).blob()
+			const fontFile = await (
+				await fetch(url, { referrerPolicy: 'strict-origin-when-cross-origin' })
+			).blob()
 			const base64FontFile = await FileHelpers.blobToDataUrl(fontFile)
 
 			const newFontFaceRule = fontFaceRule.replace(url, base64FontFile)

packages/tldraw/src/lib/ui/context/asset-urls.tsx

@@ -17,11 +17,13 @@ export function AssetUrlsProvider({
 	useEffect(() => {
 		for (const src of Object.values(assetUrls.icons)) {
 			const image = new Image()
+			image.referrerPolicy = 'strict-origin-when-cross-origin'
 			image.src = src
 			image.decode()
 		}
 		for (const src of Object.values(assetUrls.embedIcons)) {
 			const image = new Image()
+			image.referrerPolicy = 'strict-origin-when-cross-origin'
 			image.src = src
 			image.decode()
 		}

packages/tldraw/src/lib/ui/hooks/clipboard/pasteFiles.ts

@@ -14,7 +14,12 @@ export async function pasteFiles(
 	point?: VecLike,
 	sources?: TLExternalContentSource[]
 ) {
-	const blobs = await Promise.all(urls.map(async (url) => await (await fetch(url)).blob()))
+	const blobs = await Promise.all(
+		urls.map(
+			async (url) =>
+				await (await fetch(url, { referrerPolicy: 'strict-origin-when-cross-origin' })).blob()
+		)
+	)
 	const files = blobs.map((blob) => new File([blob], 'tldrawFile', { type: blob.type }))
 
 	editor.mark('paste')

packages/tldraw/src/lib/ui/hooks/clipboard/pasteUrl.ts

@@ -20,7 +20,10 @@ export async function pasteUrl(
 	try {
 		// skip this step if the url doesn't contain an image extension, treat it as a regular bookmark
 		if (new URL(url).pathname.match(/\.(png|jpe?g|gif|svg|webp)$/i)) {
-			const resp = await fetch(url, { method: 'HEAD' })
+			const resp = await fetch(url, {
+				method: 'HEAD',
+				referrerPolicy: 'strict-origin-when-cross-origin',
+			})
 			if (resp.headers.get('content-type')?.match(/^image\//)) {
 				editor.mark('paste')
 				pasteFiles(editor, [url])

packages/tldraw/src/lib/utils/export/export.ts

@@ -65,6 +65,7 @@ export async function getSvgAsImage(
 			resolve(null)
 		}
 
+		image.referrerPolicy = 'strict-origin-when-cross-origin'
 		image.src = svgUrl
 	})
 

packages/tldraw/src/lib/utils/tldr/file.ts

@@ -188,7 +188,9 @@ export async function serializeTldrawJson(store: TLStore): Promise<string> {
 					try {
 						// try to save the asset as a base64 string
 						assetSrcToSave = await FileHelpers.blobToDataUrl(
-							await (await fetch(record.props.src)).blob()
+							await (
+								await fetch(record.props.src, { referrerPolicy: 'strict-origin-when-cross-origin' })
+							).blob()
 						)
 					} catch {
 						// if that fails, just save the original src

packages/utils/src/lib/file.ts

@@ -10,9 +10,11 @@ export class FileHelpers {
 	 * from https://stackoverflow.com/a/53817185
 	 */
 	static async dataUrlToArrayBuffer(dataURL: string) {
-		return fetch(dataURL).then(function (result) {
+		return fetch(dataURL, { referrerPolicy: 'strict-origin-when-cross-origin' }).then(
-			return result.arrayBuffer()
+			function (result) {
-		})
+				return result.arrayBuffer()
+			}
+		)
 	}
 
 	/**

packages/utils/src/lib/media/media.ts

@@ -72,6 +72,7 @@ export class MediaHelpers {
 				reject(new Error('Could not load image'))
 			}
 			img.crossOrigin = 'anonymous'
+			img.referrerPolicy = 'strict-origin-when-cross-origin'
 			img.src = src
 		})
 	}