Try to be more clear about OAuth errors

app/Exceptions/Handler.php

@@ -58,6 +58,7 @@ use function Safe\parse_url;
  */
 class Handler extends ExceptionHandler
 {
+    public static ?Throwable $lastError = null;
     /**
      * @var array<int, class-string<Throwable>>
      */
@@ -123,7 +124,7 @@ class Handler extends ExceptionHandler
             // somehow Laravel handler does not catch this:
             app('log')->debug('Return JSON unauthenticated error.');
 
-            return response()->json(['message' => 'Unauthenticated', 'exception' => 'AuthenticationException'], 401);
+            return response()->json(['message' => $e->getMessage(), 'exception' => 'AuthenticationException'], 401);
         }
 
         if ($e instanceof OAuthServerException && $expectsJson) {
@@ -215,6 +216,7 @@ class Handler extends ExceptionHandler
     #[Override]
     public function report(Throwable $e): void
     {
+        self::$lastError = $e;
         $doMailError = (bool) config('firefly.send_error_message');
         if ($this->shouldntReportLocal($e) || !$doMailError) {
             parent::report($e);

app/Http/Kernel.php

@@ -178,7 +178,7 @@ class Kernel extends HttpKernel
             'api'                   => [
                 AcceptHeaders::class,
                 EnsureFrontendRequestsAreStateful::class,
-                'auth:api,sanctum',
+                'auth:api',
                 'bindings',
             ],
             // do only bindings, no auth

app/Http/Middleware/Authenticate.php

@@ -26,10 +26,12 @@ namespace FireflyIII\Http\Middleware;
 
 use Closure;
 use FireflyIII\Exceptions\FireflyException;
+use FireflyIII\Exceptions\Handler;
 use FireflyIII\User;
 use Illuminate\Auth\AuthenticationException;
 use Illuminate\Contracts\Auth\Factory as Auth;
 use Illuminate\Http\Request;
+use League\OAuth2\Server\Exception\OAuthServerException;
 
 /**
  * Class Authenticate
@@ -84,6 +86,7 @@ class Authenticate
             if ($this->auth->check()) {
                 // do an extra check on user object.
                 /** @noinspection PhpUndefinedMethodInspection */
+
                 /** @var User $user */
                 $user = $this->auth->authenticate();
                 $this->validateBlockedUser($user, $guards);
@@ -94,20 +97,23 @@ class Authenticate
         }
 
         foreach ($guards as $guard) {
-            if ('api' !== $guard) {
-                $this->auth->guard($guard)->authenticate();
-            }
             $result = $this->auth->guard($guard)->check();
             if ($result) {
                 $user = $this->auth->guard($guard)->user();
                 $this->validateBlockedUser($user, $guards);
-
                 // According to PHPstan the method returns void, but we'll see.
                 return $this->auth->shouldUse($guard); // @phpstan-ignore-line
             }
         }
 
-        throw new AuthenticationException('Unauthenticated.', $guards);
+        // this is a massive hack, but if the hander has the oauth exception
+        // at this point we can report its error instead of a generic one.
+        $message = 'Unauthenticated.';
+        if(Handler::$lastError instanceof OAuthServerException) {
+            $message = Handler::$lastError->getHint();
+        }
+
+        throw new AuthenticationException($message, $guards);
     }
 
     /**