Unexpected token in JSON (oauth_callback_handler_error)

[gfungx]

I'm using next-auth's OAuth functions. Here is my config:

import { NextApiRequest, NextApiResponse } from 'next';
import NextAuth from 'next-auth';
import Providers from 'next-auth/providers';

const options = {
  providers: [
    Providers.Google({
      clientId: process.env.GOOGLE_CLIENT_ID!,
      clientSecret: process.env.GOOGLE_CLIENT_SECRET!,
      authorizationUrl:
        'https://accounts.google.com/o/oauth2/v2/auth?prompt=consent&access_type=offline&response_type=code'
    }),
    Providers.GitHub({
      clientId: process.env.GITHUB_CLIENT_ID!,
      clientSecret: process.env.GITHUB_CLIENT_SECRET!,
      scope: 'user:email'
    })
  ],
  secret: process.env.NEXTAUTH_SECRET,
  session: { jwt: true },
  jwt: {
    secret: process.env.NEXTAUTH_JWT_SECRET,
    encryption: true,
    signingKey: process.env.NEXTAUTH_JWT_SIGNING_KEY,
    encryptionKey: process.env.NEXTAUTH_JWT_ENCRYPTION_KEY
  },
  callbacks: {
    jwt: async (token: { auth_time: number }, user: any) => {
      if (user) {
        token.auth_time = Math.floor(Date.now() / 1000);
      }
      return Promise.resolve(token);
    }
  }
};

export default (req: NextApiRequest, res: NextApiResponse) => NextAuth(req, res, options);

Everything works fine in dev and in the local build, however, when deploying to Vercel, I get the error when trying to sign in:

2021-01-23T08:33:48.697Z	484a5864-871e-489d-80ab-44566b0822a3	ERROR	[next-auth][error][oauth_callback_handler_error] SyntaxError: Unexpected token k in JSON at position 3
    at JSON.parse (<anonymous>)
    at Object.<anonymous> (/var/task/node_modules/next-auth/dist/lib/jwt.js:50:65)
    at Generator.next (<anonymous>)
    at asyncGeneratorStep (/var/task/node_modules/next-auth/dist/lib/jwt.js:22:103)
    at _next (/var/task/node_modules/next-auth/dist/lib/jwt.js:24:194)
    at /var/task/node_modules/next-auth/dist/lib/jwt.js:24:364
    at new Promise (<anonymous>)
    at Object.<anonymous> (/var/task/node_modules/next-auth/dist/lib/jwt.js:24:97)
    at Object.encode (/var/task/node_modules/next-auth/dist/lib/jwt.js:64:17)
    at /var/task/node_modules/next-auth/dist/server/routes/callback.js:117:47 
https://next-auth.js.org/errors#oauth_callback_handler_error

FWIW, a request is made [GET] /api/auth/signin?error=Callback, followed shortly after [GET] /api/auth/error?error=Callback and then the error above.

I do not know why this is and I've never seen this error before. My repo for all my code can be found here.

[aivar]

This suggests that jwt token generation fails in the Vercel environment and the error (token k and whatnot) further points to JWT_*_KEY env variables not correctly set up in the Vercel project. Not using Vercel myself for hosting, so cannot say where to go and look exactly, but it looks like your key json is in wrong format or escaped differently or something in there.

[gfungx]

Ah I've fixed it! I wasn't escaping the signing and encryption key properly, I had added an extra ". After removing this and redeploying, it works!