fix(oauth): support response_mode=form_post (#1669)

* chore: alias dev script to next

* feat(core): fallback to body when reading state

* refactor: set csrfToken on req.options implicitly

Ensures we do this similarly than
in other handlers like pkce, state, extendRes, callbackUrlHandler etc.

* chore: add code comment for debugging

CONTRIBUTING.md

@@ -42,7 +42,7 @@ npm i
 > NOTE: You can add any environment variables to .env.local that you would like to use in your dev app.
 > You can find the next-auth config under`pages/api/auth/[...nextauth].js`.
 
-1. Start the dev application/server and CSS watching:
+1. Start the dev application/server:
 ```sh
 npm run dev
 ```

package.json

@@ -10,7 +10,8 @@
     "build": "npm run build:js && npm run build:css",
     "build:js": "babel --config-file ./config/babel.config.json src --out-dir dist",
     "build:css": "postcss --config config/postcss.config.js src/**/*.css --base src --dir dist && node config/wrap-css.js",
-    "dev": "next | npm run watch:css",
+    "dev:with-css": "next | npm run watch:css",
+    "dev": "next",
     "watch": "npm run watch:js | npm run watch:css",
     "watch:js": "babel --config-file ./config/babel.config.json --watch src --out-dir dist",
     "watch:css": "postcss --config config/postcss.config.js --watch src/**/*.css --base src --dir dist",

pages/api/auth/[...nextauth].js

@@ -6,6 +6,27 @@ import Providers from 'next-auth/providers'
 // const prisma = new PrismaClient()
 
 export default NextAuth({
+  // Used to debug https://github.com/nextauthjs/next-auth/issues/1664
+  // cookies: {
+  //   csrfToken: {
+  //     name: 'next-auth.csrf-token',
+  //     options: {
+  //       httpOnly: true,
+  //       sameSite: 'none',
+  //       path: '/',
+  //       secure: true
+  //     }
+  //   },
+  //   pkceCodeVerifier: {
+  //     name: 'next-auth.pkce.code_verifier',
+  //     options: {
+  //       httpOnly: true,
+  //       sameSite: 'none',
+  //       path: '/',
+  //       secure: true
+  //     }
+  //   }
+  // },
   providers: [
     Providers.Email({
       server: process.env.EMAIL_SERVER,
@@ -19,6 +40,11 @@ export default NextAuth({
       clientId: process.env.AUTH0_ID,
       clientSecret: process.env.AUTH0_SECRET,
       domain: process.env.AUTH0_DOMAIN,
+      // Used to debug https://github.com/nextauthjs/next-auth/issues/1664
+      // protection: ["pkce", "state"],
+      // authorizationParams: {
+      //   response_mode: 'form_post'
+      // }
       protection: 'pkce'
     }),
     Providers.Twitter({

src/server/index.d.ts

@@ -82,6 +82,7 @@ export interface NextAuthInternalOptions extends Pick<NextAuthOptions, NextAuthS
   basePath?: string
   action?: string
   csrfToken?: string
+  csrfTokenVerified?: boolean
 }
 
 export interface NextAuthRequest extends NextApiRequest {

src/server/index.js

@@ -6,12 +6,12 @@ import * as cookie from './lib/cookie'
 import * as defaultEvents from './lib/default-events'
 import * as defaultCallbacks from './lib/default-callbacks'
 import parseProviders from './lib/providers'
-import callbackUrlHandler from './lib/callback-url-handler'
-import extendRes from './lib/extend-res'
 import * as routes from './routes'
 import renderPage from './pages'
-import csrfTokenHandler from './lib/csrf-token-handler'
 import createSecret from './lib/create-secret'
+import callbackUrlHandler from './lib/callback-url-handler'
+import extendRes from './lib/extend-res'
+import csrfTokenHandler from './lib/csrf-token-handler'
 import * as pkce from './lib/oauth/pkce-handler'
 import * as state from './lib/oauth/state-handler'
 
@@ -67,8 +67,6 @@ async function NextAuthHandler (req, res, userOptions) {
 
     const secret = createSecret({ userOptions, basePath, baseUrl })
 
-    const { csrfToken, csrfTokenVerified } = csrfTokenHandler(req, res, cookies, secret)
-
     const providers = parseProviders({ providers: userOptions.providers, baseUrl, basePath })
     const provider = providers.find(({ id }) => id === providerId)
 
@@ -107,7 +105,6 @@ async function NextAuthHandler (req, res, userOptions) {
       provider,
       cookies,
       secret,
-      csrfToken,
       providers,
       // Session options
       session: {
@@ -138,6 +135,7 @@ async function NextAuthHandler (req, res, userOptions) {
       logger
     }
 
+    csrfTokenHandler(req, res)
     await callbackUrlHandler(req, res)
 
     const render = renderPage(req, res)
@@ -150,7 +148,7 @@ async function NextAuthHandler (req, res, userOptions) {
         case 'session':
           return routes.session(req, res)
         case 'csrf':
-          return res.json({ csrfToken })
+          return res.json({ csrfToken: req.options.csrfToken })
         case 'signin':
           if (pages.signIn) {
             let signinUrl = `${pages.signIn}${pages.signIn.includes('?') ? '&' : '?'}callbackUrl=${req.options.callbackUrl}`
@@ -203,7 +201,7 @@ async function NextAuthHandler (req, res, userOptions) {
       switch (action) {
         case 'signin':
           // Verified CSRF Token required for all sign in routes
-          if (csrfTokenVerified && provider) {
+          if (req.options.csrfTokenVerified && provider) {
             if (await pkce.handleSignin(req, res)) return
             if (await state.handleSignin(req, res)) return
             return routes.signin(req, res)
@@ -212,14 +210,14 @@ async function NextAuthHandler (req, res, userOptions) {
           return res.redirect(`${baseUrl}${basePath}/signin?csrf=true`)
         case 'signout':
           // Verified CSRF Token required for signout
-          if (csrfTokenVerified) {
+          if (req.options.csrfTokenVerified) {
             return routes.signout(req, res)
           }
           return res.redirect(`${baseUrl}${basePath}/signout?csrf=true`)
         case 'callback':
           if (provider) {
             // Verified CSRF Token required for credentials providers only
-            if (provider.type === 'credentials' && !csrfTokenVerified) {
+            if (provider.type === 'credentials' && !req.options.csrfTokenVerified) {
               return res.redirect(`${baseUrl}${basePath}/signin?csrf=true`)
             }
 

src/server/lib/csrf-token-handler.js

@@ -14,29 +14,30 @@ import * as cookie from './cookie'
  * For more details, see the following OWASP links:
  * https://cheatsheetseries.owasp.org/cheatsheets/Cross-Site_Request_Forgery_Prevention_Cheat_Sheet.html#double-submit-cookie
  * https://owasp.org/www-chapter-london/assets/slides/David_Johansson-Double_Defeat_of_Double-Submit_Cookie.pdf
+ * @param {import("..").NextAuthRequest} req
+ * @param {import("..").NextAuthResponse} res
  */
-export default function csrfTokenHandler (req, res, cookies, secret) {
-  const { csrfToken: csrfTokenFromRequest } = req.body
-
-  let csrfTokenFromCookie
-  let csrfTokenVerified = false
-  if (req.cookies[cookies.csrfToken.name]) {
-    const [csrfTokenValue, csrfTokenHash] = req.cookies[cookies.csrfToken.name].split('|')
-    if (csrfTokenHash === createHash('sha256').update(`${csrfTokenValue}${secret}`).digest('hex')) {
+export default function csrfTokenHandler (req, res) {
+  const { cookies, secret } = req.options
+  if (cookies.csrfToken.name in req.cookies) {
+    const [csrfToken, csrfTokenHash] = req.cookies[cookies.csrfToken.name].split('|')
+    const expectedCsrfTokenHash = createHash('sha256').update(`${csrfToken}${secret}`).digest('hex')
+    if (csrfTokenHash === expectedCsrfTokenHash) {
       // If hash matches then we trust the CSRF token value
-      csrfTokenFromCookie = csrfTokenValue
-
-      // If this is a POST request and the CSRF Token in the Post request matches
-      // the cookie we have already verified is one we have set, then token is verified!
-      if (req.method === 'POST' && csrfTokenFromCookie === csrfTokenFromRequest) { csrfTokenVerified = true }
+      // If this is a POST request and the CSRF Token in the POST request matches
+      // the cookie we have already verified is the one we have set, then the token is verified!
+      const csrfTokenVerified = req.method === 'POST' && csrfToken === req.body.csrfToken
+      req.options.csrfToken = csrfToken
+      req.options.csrfTokenVerified = csrfTokenVerified
+      return
     }
   }
-  if (!csrfTokenFromCookie) {
-    // If no csrfToken - because it's not been set yet, or because the hash doesn't match
-    // (e.g. because it's been modifed or because the secret has changed) create a new token.
-    csrfTokenFromCookie = randomBytes(32).toString('hex')
-    const newCsrfTokenCookie = `${csrfTokenFromCookie}|${createHash('sha256').update(`${csrfTokenFromCookie}${secret}`).digest('hex')}`
-    cookie.set(res, cookies.csrfToken.name, newCsrfTokenCookie, cookies.csrfToken.options)
-  }
-  return { csrfToken: csrfTokenFromCookie, csrfTokenVerified }
+  // If no csrfToken from cookie - because it's not been set yet,
+  // or because the hash doesn't match (e.g. because it's been modifed or because the secret has changed)
+  // create a new token.
+  const csrfToken = randomBytes(32).toString('hex')
+  const csrfTokenHash = createHash('sha256').update(`${csrfToken}${secret}`).digest('hex')
+  const csrfTokenCookie = `${csrfToken}|${csrfTokenHash}`
+  cookie.set(res, cookies.csrfToken.name, csrfTokenCookie, cookies.csrfToken.options)
+  req.options.csrfToken = csrfToken
 }

src/server/lib/oauth/state-handler.js

@@ -17,7 +17,7 @@ export async function handleCallback (req, res) {
       return
     }
 
-    const { state } = req.query
+    const state = req.query.state || req.body.state
     const expectedState = createHash('sha256').update(csrfToken).digest('hex')
 
     logger.debug(