Laravel Passport Password Grant - Client authentication failed

This might help point you in the right direction because we're implementing the password grant ourselves.

1 - On your step 4 instead of running this:

php artisan passport:install

run the following to create your password grant Client:

php artisan passport:client --password

The above command will give a followup question to set the name of your Password Grant Client. Be sure to get the id and secret of this new record in your database.

2 - Your POSTMAN Post request object should be wrapped inside an object similar to the following:

'form_params' => [
    'grant_type' => 'password',
    'client_id' => 'my_client-id',
    'client_secret' => 'my_client-secret',
    'username' => 'username or email', <-pass through variables or something
    'password' => 'my-user-password', <- pass through variables or something
    'scope' => '',
],

Update 1 10/12/2016:

On further investigation of this issue I ran into the exact same spot you're at and was forced to dive into the rabbit hole of passport.

Currently from what I'm seeing the system has set the client identifier as 'authorization_code' when it needs to be 'password'. I'm researching how to resolve this issue you're having as I've ran into it too. I will post code to help people follow along where I've been and what I've been doing but it's 2:40 am right now so I need some sleep.

Update 2 10/12/2016

Been debugging the issue for 7 hours now. There is a method within passport that validates the client. This method takes the inputs you've added in the object (mentioned above) and attempts to get the Client Entity through a client repository class based on what you've passed in. If a Client is found it will then be checked to see if an instance of the Client Entity truly exists within the Client Entity Interface which LOOKS like it pulls in the Client's credentials from the database. However, there is a block of code which returns NULL From what I'm getting in my testing. ALL fields are being introduced properly so far but there seems to be a mix-up between the repository and the interface. Which is causing the error to be thrown.

In the end I feel I'm getting close to solving this issue. Your patience is greatly appreciated. =)

Update 3 10/12/2016

After a long period of debugging I've found the initial problem. There were fields that weren't matching up. In short, it's a setup issue.

SO

The solution in this case is:

DOUBLE CHECK ALL FIELDS In the database with ALL credentials being passed in. Right down to periods, dashes, spaces passwords, client id, client secret, VALID redirect URIs/URLs, grant_types, and scopes (if you're using them):

Make sure the client in the database has an ENUM of 1 under the "password_client" column, if not you need to create one using the mentioned php artisan command above, which I'll reference here:

php artisan passport:client --password

Make sure the secret you're passing in matches what is listed for that client in your database character for character

Make sure the id you're passing matches and is of an integer data type.

Make sure there is a name of some sort for the client

Do not worry about the user_id column when using password grants

make sure the route is correct

Make sure the email your entering in (username) is an actual user inside of your users table within your database (or whatever table you customized the laravel 5.3 system to accept as your users table, I will add a link on how to customize laravel 5.3 system to accept a different users table as default if any need it).

Make sure the grant_type is spelled correctly

Make sure you're set up to accept the response bearer token (meaning the access_token and refresh_token).

Other than that, the initial steps I've outlined in the above part of this Answer should put you back on the right track. There are others here who did mention some similar steps that are helpful but address the same error that is related to a seperate issue as well (which I'm sure is a result of a setup issue related to their specific system setup).

I hope this helps though.

Check your credentials first if they are correct, Secondly check your model table which uses \Laravel\Passport\HasApiTokens trait that whether it contains email column, because by default it is used to identify user when validating credentials. if your table has username column or any other column which is used in validating credentials you must define a function findForPassport in that model. like this,

public function findForPassport($username) {
       return self::where('username', $username)->first(); // change column name whatever you use in credentials
    }

I use username and password column to validate a user, in {project_directory}\vendor\laravel\passport\src\Bridge\UserRepository.php

this function validates your credentials,

public function getUserEntityByUserCredentials($username, $password, $grantType, ClientEntityInterface $clientEntity)
    {
        if (is_null($model = config('auth.providers.users.model'))) {
            throw new RuntimeException('Unable to determine user model from configuration.');
        }

        if (method_exists($model, 'findForPassport')) { // if you define the method in that model it will grab it from there other wise use email as key 
            $user = (new $model)->findForPassport($username);
        } else {
            $user = (new $model)->where('email', $username)->first();
        }

        if (! $user || ! $this->hasher->check($password, $user->password)) {
            return;
        }

        return new User($user->getAuthIdentifier());
    }

notice the second if statement and you will get to know what is happening there.

hope this help :)