Sign in with Apple returns FIRAuthErrorDomain Code=17999

[stormphlegyas]

Description

I'm experiencing an issue with "Sign in with Apple" in the Firebase iOS SDK. The authentication process returns a 400 HTTP error (Bad Request) when trying to sign in using Apple.

All Firebase and Apple configurations (redirect URIs, API keys, and private key) appear to be correctly set up, and the issue is persistent across multiple test attempts.
I'm using a private key (.p8 file) for the Apple authentication, which is correctly configured in Firebase with the Apple team ID and service ID. The Firebase console shows the correct private key and the associated team and service IDs.

Reproducing the issue

1. Set up Firebase iOS SDK (version 11.2) and enable "Sign in with Apple" in both Firebase and Apple Developer Console.
2. Ensure the redirect URL is correctly configured in both Firebase and Apple Developer.
3. Use a private key for Apple authentication in Firebase (.p8 file) with the correct Apple Team ID and Service ID.
4. Test the "Sign in with Apple" flow in debug mode on an iOS device.
5. The request returns a FIRAuthErrorDomain Code=17999 error, preventing successful sign-in.

Firebase SDK Version

11.2

Xcode Version

16.0

Installation Method

Swift Package Manager

Firebase Product(s)

Authentication

Targeted Platforms

iOS

Relevant Log Output

Error Domain=FIRAuthErrorDomain Code=17999 "An internal error has occurred, print and inspect the error details for more information." UserInfo={FIRAuthErrorUserInfoNameKey=ERROR_INTERNAL_ERROR, NSLocalizedDescription=An internal error has occurred, print and inspect the error details for more information., NSUnderlyingError=0x303783540 {Error Domain=FIRAuthInternalErrorDomain Code=2 "(null)" UserInfo={NSUnderlyingError=0x3037838d0 {Error Domain=NSCocoaErrorDomain Code=3840 "JSON text did not start with array or object and option to allow fragments not set. around line 1, column 0." UserInfo={NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set. around line 1, column 0., NSJSONSerializationErrorIndex=0}}}}} details: ["FIRAuthErrorUserInfoNameKey": "ERROR_INTERNAL_ERROR", "NSLocalizedDescription": "An internal error has occurred, print and inspect the error details for more information.", "NSUnderlyingError": Error Domain=FIRAuthInternalErrorDomain Code=2 "(null)" UserInfo={NSUnderlyingError=0x3037838d0 {Error Domain=NSCocoaErrorDomain Code=3840 "JSON text did not start with array or object and option to allow fragments not set. around line 1, column 0." UserInfo={NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set. around line 1, column 0., NSJSONSerializationErrorIndex=0}}}]

If using Swift Package Manager, the project's Package.resolved

Expand Package.resolved snippet

{
      "identity" : "firebase-ios-sdk",
      "kind" : "remoteSourceControl",
      "location" : "https://github.com/firebase/firebase-ios-sdk.git",
      "state" : {
        "revision" : "1fc52ab0e172e7c5a961f975a76c2611f4f22852",
        "version" : "11.2.0"
      }
}

If using CocoaPods, the project's Podfile.lock

Expand Podfile.lock snippet

Replace this line with the contents of your Podfile.lock!

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