I’m trying to implement a custom OAuth2 grant type in Laravel Passport for mobile authentication, but I’m encountering the following error

{
    "error": "unsupported_grant_type",
    "error_description": "The authorization grant type is not supported by the authorization server."
}

Here is the custom MobileGrant class I’m using:

namespace App\Grants;

use App\Enums\UserType;
use Laravel\Passport\Bridge\UserRepository;
use Laravel\Passport\Bridge\RefreshTokenRepository;
use Laravel\Passport\Bridge\AccessToken;
use League\OAuth2\Server\Grant\AbstractGrant;
use League\OAuth2\Server\RequestTypes\AuthorizationRequest;
use League\OAuth2\Server\ResponseTypes\ResponseTypeInterface;
use Psr\Http\Message\ServerRequestInterface;
use DateInterval;
use App\Models\User;
use Carbon\Carbon;
use Illuminate\Support\Facades\Auth;

class MobileGrant extends AbstractGrant
{
    public function __construct(UserRepository $userRepository, RefreshTokenRepository $refreshTokenRepository)
    {
        $this->setUserRepository($userRepository);
        $this->setRefreshTokenRepository($refreshTokenRepository);
    }

    public function respondToAccessTokenRequest(
        ServerRequestInterface $request,
        ResponseTypeInterface $responseType,
        DateInterval $accessTokenTTL
    ) {
        $mobile = $this->getRequestParameter('mobile', $request);
        $confirmCode = $this->getRequestParameter('mobile_confirm_code', $request);

        if (!$mobile || !$confirmCode) {
            return response()->json(['message' => 'Mobile number and confirmation code are required.'], 400);
        }

        $user = User::where('mobile', $mobile)->first();

        if (User::where(['mobile' => $mobile, 'mobile_confirm_code' => $confirmCode])->exists() || $confirmCode == "1234") {
            if (!self::isExpiredConfirmCode($user)) {
                if (User::where(['mobile' => $mobile])->whereNull('mobile_verified_at')->exists()) {
                    User::where('mobile', $mobile)->update([
                        'mobile_verified_at' => Carbon::now()->format('Y-m-d H:i:s')
                    ]);
                }

                Auth::login($user);
                $role = UserType::hasValue($user->role) ? $user->role : null;

                $accessToken = $this->issueAccessToken($accessTokenTTL, $user->id, $role);
                $refreshToken = $this->issueRefreshToken($accessToken);

                return [
                    'token_type' => 'Bearer',
                    'expires_in' => $accessTokenTTL->s,
                    'access_token' => (string) $accessToken,
                    'refresh_token' => (string) $refreshToken,
                ];
            } else {
                return response()->json(['message' => 'Confirmation code expired.'], 400);
            }
        } else {
            return response()->json(['message' => 'Invalid confirmation code.'], 400);
        }
    }

    public function getIdentifier()
    {
        return 'mobile';
    }

    public function isExpiredConfirmCode($user)
    {
        return Carbon::parse($user->expire_mobile_confirm_code)->lt(Carbon::now());
    }
}

In my AppServiceProvider, I enable the custom grant type:

public function boot(): void
{
    app(AuthorizationServer::class)->enableGrantType(
        new MobileGrant(
            app()->make(\Laravel\Passport\Bridge\UserRepository::class),
            app()->make(\Laravel\Passport\Bridge\RefreshTokenRepository::class)
        ),
        new \DateInterval('P1Y') // Access token expiration time
    );
}

However, when I try to request the token with the following data:

{
    "grant_type": "mobile",
    "client_id": "client-id-here",
    "client_secret": "client-secret-here",
    "mobile": "mobileNumber",
    "mobile_confirm_code": "1234",
    "scope": ""
}

I get the unsupported_grant_type error.

Could anyone help me figure out why this error occurs and how to resolve it? I have enabled the custom grant type in AppServiceProvider, but it’s still not working.

Thanks in advance!

Getting ‘unsupported_grant_type’ error when implementing a custom OAuth2 grant in Laravel Passport