API authentication with Sanctum in Laravel - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Sanctum token creation code?

Consider this Laravel controller method using Sanctum to create a token for a user. What will be the output JSON response?

Laravel

public function login(Request $request) {
    $user = User::where('email', $request->email)->first();
    if (! $user || ! Hash::check($request->password, $user->password)) {
        return response()->json(['message' => 'Invalid credentials'], 401);
    }
    $token = $user->createToken('api-token')->plainTextToken;
    return response()->json(['token' => $token]);
}

A 500 Internal Server Error

B {"token": null}

C {"message": "Invalid credentials"}

D {"token": "<a long string token>"}

💡 Hint

The createToken method returns a token object with a plainTextToken property.

If the user exists and password matches, createToken generates a new token string. The response returns this token in JSON under 'token'.

❓ lifecycle

intermediate

Which middleware is required to protect Sanctum API routes?

You want to protect your API routes so only authenticated users with valid Sanctum tokens can access them. Which middleware should you apply to these routes?

A auth:sanctum

B auth:api

C guest

D web

💡 Hint

Sanctum uses a specific guard for API token authentication.

The 'auth:sanctum' middleware ensures the request has a valid Sanctum token and authenticates the user accordingly.

🔧 Debug

advanced

Why does this Sanctum token authentication fail with 401 Unauthorized?

This API route uses 'auth:sanctum' middleware but always returns 401 Unauthorized even with a valid token sent in the Authorization header. What is the most likely cause?

Laravel

Route::middleware('auth:sanctum')->get('/user', function (Request $request) {
    return $request->user();
});

// Client sends header: Authorization: Bearer <valid_token>

A The Authorization header is misspelled or missing the 'Bearer' prefix.

B The token was created with 'createToken' but not saved to the database.

C The user model does not use the 'HasApiTokens' trait.

D The 'EnsureFrontendRequestsAreStateful' middleware is missing from the middleware group.

💡 Hint

Check if the user model supports Sanctum tokens.

If the user model lacks the 'HasApiTokens' trait, Sanctum cannot authenticate tokens for that user, causing 401 errors.

📝 Syntax

advanced

Which code snippet correctly revokes all Sanctum tokens for the authenticated user?

You want to log out a user by deleting all their API tokens. Which code snippet correctly does this?

A $request->user()->tokens()->delete();

B $request->user()->token()->delete();

C Auth::user()->revokeTokens();

D $request->user()->deleteTokens();

💡 Hint

The tokens() method returns a relationship to all tokens.

The tokens() method returns a collection of all tokens for the user. Calling delete() on it removes all tokens.

🧠 Conceptual

expert

What is the main difference between Sanctum's SPA authentication and API token authentication?

Sanctum supports two main authentication methods: SPA authentication using cookies and API token authentication using tokens. What is the key difference in how they authenticate users?

A SPA authentication requires OAuth2, while API token authentication uses simple API keys.

B SPA authentication uses session cookies and CSRF protection, while API token authentication uses bearer tokens in headers without sessions.

C SPA authentication only works with mobile apps, API token authentication only with web browsers.

D SPA authentication stores tokens in localStorage, API token authentication stores tokens in cookies.

💡 Hint

Think about how browsers handle cookies and headers differently.

Sanctum's SPA authentication uses Laravel's session cookies and CSRF tokens to authenticate requests, while API token authentication uses bearer tokens sent in headers without sessions.