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Fix broken HTML inlining of non UTF-8 decodable binary data from Flig…
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…ht payload (vercel#65664)

This PR ensures that any arbitrary binary data can be passed across the
RSC boundary, especially when inlined in HTML. While the Flight payloads
in RSC requests (`text/x-component`) already work, it's a different case
when we inline them directly in HTML as that's required to be a valid
string in UTF-8.

So instead of always inlining the UTF-8 decoded chunk (`new
TextDecoder('utf-8')`), we fallback non-decodable chunks to base64 and
send as a special item in `__next_f` so we can safely change it back to
a binary typed array.

---------

Co-authored-by: JJ Kasper <jj@jjsweb.site>
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@shuding @ijjk @panteliselef
2 people authored and panteliselef committed May 20, 2024
1 parent 6ec1fc1 commit 054988f
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Showing 15 changed files with 344 additions and 76 deletions.
21 changes: 19 additions & 2 deletions packages/next/src/client/app-index.tsx
View file
Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ const appElement: HTMLElement | Document | null = document

const encoder = new TextEncoder()

let initialServerDataBuffer: string[] | undefined = undefined
let initialServerDataBuffer: (string | Uint8Array)[] | undefined = undefined
let initialServerDataWriter: ReadableStreamDefaultController | undefined =
undefined
let initialServerDataLoaded = false
Expand All @@ -56,6 +56,7 @@ function nextServerDataCallback(
| [isBootStrap: 0]
| [isNotBootstrap: 1, responsePartial: string]
| [isFormState: 2, formState: any]
| [isBinary: 3, responseBase64Partial: string]
): void {
if (seg[0] === 0) {
initialServerDataBuffer = []
Expand All @@ -70,6 +71,22 @@ function nextServerDataCallback(
}
} else if (seg[0] === 2) {
initialFormStateData = seg[1]
} else if (seg[0] === 3) {
if (!initialServerDataBuffer)
throw new Error('Unexpected server data: missing bootstrap script.')

// Decode the base64 string back to binary data.
const binaryString = atob(seg[1])
const decodedChunk = new Uint8Array(binaryString.length)
for (var i = 0; i < binaryString.length; i++) {
decodedChunk[i] = binaryString.charCodeAt(i)
}

if (initialServerDataWriter) {
initialServerDataWriter.enqueue(decodedChunk)
} else {
initialServerDataBuffer.push(decodedChunk)
}
}
}

Expand All @@ -84,7 +101,7 @@ function nextServerDataCallback(
function nextServerDataRegisterWriter(ctr: ReadableStreamDefaultController) {
if (initialServerDataBuffer) {
initialServerDataBuffer.forEach((val) => {
ctr.enqueue(encoder.encode(val))
ctr.enqueue(typeof val === 'string' ? encoder.encode(val) : val)
})
if (initialServerDataLoaded && !initialServerDataFlushed) {
ctr.close()
Expand Down
2 changes: 1 addition & 1 deletion packages/next/src/server/app-render/app-render.tsx
View file
Original file line number Diff line number Diff line change
Expand Up @@ -398,7 +398,7 @@ function createFlightDataResolver(ctx: AppRenderContext) {
// Generate the flight data and as soon as it can, convert it into a string.
const promise = generateFlight(ctx)
.then(async (result) => ({
flightData: await result.toUnchunkedString(true),
flightData: await result.toUnchunkedBuffer(true),
}))
// Otherwise if it errored, return the error.
.catch((err) => ({ err }))
Expand Down
53 changes: 39 additions & 14 deletions packages/next/src/server/app-render/use-flight-response.tsx
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ const isEdgeRuntime = process.env.NEXT_RUNTIME === 'edge'
const INLINE_FLIGHT_PAYLOAD_BOOTSTRAP = 0
const INLINE_FLIGHT_PAYLOAD_DATA = 1
const INLINE_FLIGHT_PAYLOAD_FORM_STATE = 2
const INLINE_FLIGHT_PAYLOAD_BINARY = 3

const flightResponses = new WeakMap<BinaryStreamOf<any>, Promise<any>>()
const encoder = new TextEncoder()
Expand Down Expand Up @@ -96,10 +97,8 @@ export function createInlinedDataReadableStream(
? `<script nonce=${JSON.stringify(nonce)}>`
: '<script>'

const decoder = new TextDecoder('utf-8', { fatal: true })
const decoderOptions = { stream: true }

const flightReader = flightStream.getReader()
const decoder = new TextDecoder('utf-8', { fatal: true })

const readable = new ReadableStream({
type: 'bytes',
Expand All @@ -114,15 +113,26 @@ export function createInlinedDataReadableStream(
async pull(controller) {
try {
const { done, value } = await flightReader.read()
if (done) {
const tail = decoder.decode(value, { stream: false })
if (tail.length) {
writeFlightDataInstruction(controller, startScriptTag, tail)

if (value) {
try {
const decodedString = decoder.decode(value, { stream: !done })

// The chunk cannot be decoded as valid UTF-8 string as it might
// have arbitrary binary data.
writeFlightDataInstruction(
controller,
startScriptTag,
decodedString
)
} catch {
// The chunk cannot be decoded as valid UTF-8 string.
writeFlightDataInstruction(controller, startScriptTag, value)
}
}

if (done) {
controller.close()
} else {
const chunkAsString = decoder.decode(value, decoderOptions)
writeFlightDataInstruction(controller, startScriptTag, chunkAsString)
}
} catch (error) {
// There was a problem in the upstream reader or during decoding or enqueuing
Expand Down Expand Up @@ -154,13 +164,28 @@ function writeInitialInstructions(
function writeFlightDataInstruction(
controller: ReadableStreamDefaultController,
scriptStart: string,
chunkAsString: string
chunk: string | Uint8Array
) {
let htmlInlinedData: string

if (typeof chunk === 'string') {
htmlInlinedData = htmlEscapeJsonString(
JSON.stringify([INLINE_FLIGHT_PAYLOAD_DATA, chunk])
)
} else {
// The chunk cannot be embedded as a UTF-8 string in the script tag.
// Instead let's inline it in base64.
// Credits to Devon Govett (devongovett) for the technique.
// https://github.com/devongovett/rsc-html-stream
const base64 = btoa(String.fromCodePoint(...chunk))
htmlInlinedData = htmlEscapeJsonString(
JSON.stringify([INLINE_FLIGHT_PAYLOAD_BINARY, base64])
)
}

controller.enqueue(
encoder.encode(
`${scriptStart}self.__next_f.push(${htmlEscapeJsonString(
JSON.stringify([INLINE_FLIGHT_PAYLOAD_DATA, chunkAsString])
)})</script>`
`${scriptStart}self.__next_f.push(${htmlInlinedData})</script>`
)
)
}
73 changes: 58 additions & 15 deletions packages/next/src/server/base-server.ts
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,8 @@ import type { ParsedUrlQuery } from 'querystring'
import type { RenderOptsPartial as PagesRenderOptsPartial } from './render'
import type { RenderOptsPartial as AppRenderOptsPartial } from './app-render/types'
import type {
CachedAppPageValue,
CachedPageValue,
ResponseCacheBase,
ResponseCacheEntry,
ResponseGenerator,
Expand Down Expand Up @@ -2543,16 +2545,29 @@ export default abstract class Server<
return null
}

if (isAppPath) {
return {
value: {
kind: 'APP_PAGE',
html: result,
headers,
rscData: metadata.flightData,
postponed: metadata.postponed,
status: res.statusCode,
} satisfies CachedAppPageValue,
revalidate: metadata.revalidate,
}
}

// We now have a valid HTML result that we can return to the user.
return {
value: {
kind: 'PAGE',
html: result,
pageData: metadata.pageData ?? metadata.flightData,
postponed: metadata.postponed,
pageData: metadata.pageData,
headers,
status: isAppPath ? res.statusCode : undefined,
},
status: res.statusCode,
} satisfies CachedPageValue,
revalidate: metadata.revalidate,
}
}
Expand Down Expand Up @@ -2665,7 +2680,6 @@ export default abstract class Server<
value: {
kind: 'PAGE',
html: RenderResult.fromStatic(html),
postponed: undefined,
status: undefined,
headers: undefined,
pageData: {},
Expand Down Expand Up @@ -2734,7 +2748,7 @@ export default abstract class Server<
}

const didPostpone =
cacheEntry.value?.kind === 'PAGE' &&
cacheEntry.value?.kind === 'APP_PAGE' &&
typeof cacheEntry.value.postponed === 'string'

if (
Expand Down Expand Up @@ -2901,7 +2915,11 @@ export default abstract class Server<
} else if (isAppPath) {
// If the request has a postponed state and it's a resume request we
// should error.
if (cachedData.postponed && minimalPostponed) {
if (
cachedData.kind === 'APP_PAGE' &&
cachedData.postponed &&
minimalPostponed
) {
throw new Error(
'Invariant: postponed state should not be present on a resume request'
)
Expand Down Expand Up @@ -2949,7 +2967,11 @@ export default abstract class Server<
}

// Mark that the request did postpone if this is a data request.
if (cachedData.postponed && isRSCRequest) {
if (
cachedData.kind === 'APP_PAGE' &&
cachedData.postponed &&
isRSCRequest
) {
res.setHeader(NEXT_DID_POSTPONE_HEADER, '1')
}

Expand All @@ -2960,8 +2982,15 @@ export default abstract class Server<
if (isDataReq && !isPreviewMode) {
// If this is a dynamic RSC request, then stream the response.
if (isDynamicRSCRequest) {
if (cachedData.pageData) {
throw new Error('Invariant: Expected pageData to be undefined')
if (cachedData.kind !== 'APP_PAGE') {
console.error({ url: req.url, pathname }, cachedData)
throw new Error(
`Invariant: expected cache data kind of APP_PAGE got ${cachedData.kind}`
)
}

if (cachedData.rscData) {
throw new Error('Invariant: Expected rscData to be undefined')
}

if (cachedData.postponed) {
Expand All @@ -2980,17 +3009,23 @@ export default abstract class Server<
}
}

if (typeof cachedData.pageData !== 'string') {
if (cachedData.kind !== 'APP_PAGE') {
throw new Error(
`Invariant: expected cached data to be APP_PAGE got ${cachedData.kind}`
)
}

if (!Buffer.isBuffer(cachedData.rscData)) {
throw new Error(
`Invariant: expected pageData to be a string, got ${typeof cachedData.pageData}`
`Invariant: expected rscData to be a Buffer, got ${typeof cachedData.rscData}`
)
}

// As this isn't a prefetch request, we should serve the static flight
// data.
return {
type: 'rsc',
body: RenderResult.fromStatic(cachedData.pageData),
body: RenderResult.fromStatic(cachedData.rscData),
revalidate: cacheEntry.revalidate,
}
}
Expand All @@ -3001,7 +3036,10 @@ export default abstract class Server<
// If there's no postponed state, we should just serve the HTML. This
// should also be the case for a resume request because it's completed
// as a server render (rather than a static render).
if (!cachedData.postponed || this.minimalMode) {
if (
!(cachedData.kind === 'APP_PAGE' && cachedData.postponed) ||
this.minimalMode
) {
return {
type: 'html',
body,
Expand Down Expand Up @@ -3030,7 +3068,7 @@ export default abstract class Server<
throw new Error('Invariant: expected a result to be returned')
}

if (result.value?.kind !== 'PAGE') {
if (result.value?.kind !== 'APP_PAGE') {
throw new Error(
`Invariant: expected a page response, got ${result.value?.kind}`
)
Expand All @@ -3056,6 +3094,11 @@ export default abstract class Server<
revalidate: 0,
}
} else if (isDataReq) {
if (cachedData.kind !== 'PAGE') {
throw new Error(
`Invariant: expected cached data to be PAGE got ${cachedData.kind}`
)
}
return {
type: 'json',
body: RenderResult.fromStatic(JSON.stringify(cachedData.pageData)),
Expand Down
5 changes: 4 additions & 1 deletion packages/next/src/server/lib/incremental-cache/fetch-cache.ts
View file
Original file line number Diff line number Diff line change
Expand Up @@ -109,7 +109,10 @@ export default class FetchCache implements CacheHandler {
}
// rough estimate of size of cache value
return (
value.html.length + (JSON.stringify(value.pageData)?.length || 0)
value.html.length +
(JSON.stringify(
value.kind === 'APP_PAGE' ? value.rscData : value.pageData
)?.length || 0)
)
},
})
Expand Down
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