Service account object must contain a string "private_key" property.

[sinjs]

When logging in (/auth), I can log in normally, but when accessing / again, there's the following error:

Error: Received 500 response from login API endpoint: {"error":"Unexpected error."}

The logs of the server:

FirebaseAppError: Service account object must contain a string "private_key" property.
    at FirebaseAppError.FirebaseError [as constructor] (/mnt/src/next-auth-test/node_modules/firebase-admin/lib/utils/error.js:44:28)
    at FirebaseAppError.PrefixedFirebaseError [as constructor] (/mnt/src/next-auth-test/node_modules/firebase-admin/lib/utils/error.js:90:28)
    at new FirebaseAppError (/mnt/src/next-auth-test/node_modules/firebase-admin/lib/utils/error.js:125:28)
    at new ServiceAccount (/mnt/src/next-auth-test/node_modules/firebase-admin/lib/credential/credential-internal.js:134:19)
    at new ServiceAccountCredential (/mnt/src/next-auth-test/node_modules/firebase-admin/lib/credential/credential-internal.js:68:15)
    at Object.exports.cert (/mnt/src/next-auth-test/node_modules/firebase-admin/lib/credential/credential.js:34:54)
    at z (/mnt/src/next-auth-test/node_modules/next-firebase-auth/build/index.node.js:2:16085)
    at /mnt/src/next-auth-test/node_modules/next-firebase-auth/build/index.node.js:2:16932
    at Generator.next (<anonymous>)
    at asyncGeneratorStep (/mnt/src/next-auth-test/node_modules/@babel/runtime/helpers/asyncToGenerator.js:3:24) {
  errorInfo: {
    code: 'app/invalid-credential',
    message: 'Service account object must contain a string "private_key" property.'
  },
  codePrefix: 'app'
}

But the AuthUser object (useAuthUser()) is filled with the following information:

{"id":"64NspDbEiYaEdNeBJ3glfFG0agK2","email":"hello@example.org","emailVerified":false,"phoneNumber":null,"displayName":null,"photoURL":null,"claims":{},"clientInitialized":true,"firebaseUser":{"uid":"64NspDbEiYaEdNeBJ3glfFG0agK2","displayName":null,"photoURL":null,"email":"hello@example.org","emailVerified":false,"phoneNumber":null,"isAnonymous":false,"tenantId":null,"providerData":[{"uid":"hello@example.org","displayName":null,"photoURL":null,"email":"hello@example.org","phoneNumber":null,"providerId":"password"}],"apiKey":"...","appName":"[DEFAULT]","authDomain":null,"stsTokenManager":{"apiKey":"...","refreshToken":"...","accessToken":"...","expirationTime":1627293786104},"redirectEventId":null,"lastLoginAt":"1627290185934","createdAt":"1627290185934","multiFactor":{"enrolledFactors":[]}}}

[kmjennison]

Can you double-check that the config value firebaseAdminInitConfig.credential.privateKey is set on the server side as you'd expect?

Similar: #239, #232

[sinjs]

I've already checked that, it's the private key

[kmjennison]

Are you using the demo app in this repo? If not, would it be possible for you to try it with your own env variables? It's hard to debug these private key configurations, so that will at least remove any differences in app code.