Role-based authorization in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is role-based authorization in NestJS?

Role-based authorization in NestJS controls access to resources by assigning roles to users and allowing or denying actions based on those roles.

beginner

Which NestJS feature helps implement role-based authorization easily?

Guards, especially custom guards like RolesGuard, help implement role-based authorization by checking user roles before allowing access.

intermediate

How do you define roles on a route in NestJS?

You use a custom decorator like @Roles('admin') on a controller method to specify which roles can access that route.

intermediate

What is the purpose of the RolesGuard in NestJS?

RolesGuard reads the roles required by a route and compares them with the user's roles to decide if access should be granted.

beginner

Why is role-based authorization important in web applications?

It ensures users only access what they are allowed to, protecting sensitive data and actions, improving security and user experience.

In NestJS, which decorator is commonly used to specify roles on a route?

A @Roles()

B @Auth()

C @Guard()

D @Access()

The @Roles() decorator is used to define which roles can access a route.

What does a RolesGuard do in NestJS?

A Manages database connections

B Encrypts user passwords

C Handles HTTP requests

D Checks if a user has the required roles to access a route

RolesGuard checks user roles against required roles for route access.

Which NestJS feature is best suited to block unauthorized access based on roles?

A Interceptors

B Middleware

C Guards

D Pipes

Guards are designed to control access and can check roles before route handlers run.

If a user does not have the required role, what should the RolesGuard do?

A Allow access anyway

B Throw an UnauthorizedException

C Log the user out

D Redirect to homepage

RolesGuard should throw an UnauthorizedException to block access.

Where do you usually store user roles for authorization checks?

A In the user object attached to the request

B In the request headers

C In the database only

D In the URL query parameters

User roles are typically attached to the user object in the request after authentication.

Explain how role-based authorization works in NestJS using guards and decorators.

Think about how you tell NestJS which roles can access a route and how it checks the user's roles.

Describe why role-based authorization is important for web app security and user experience.

Consider what happens if anyone could access everything without restrictions.

Practice

1. What is the main purpose of role-based authorization in a NestJS application?

easy

A. To handle HTTP request parsing

B. To manage database connections

C. To control access to routes based on user roles

D. To format response data

Solution

1. Step 1: Understand role-based authorization concept

   Role-based authorization restricts access to parts of an app depending on the user's role.

2. Step 2: Identify the purpose in NestJS context

   In NestJS, it controls which users can access certain routes or features based on their roles.

3. Final Answer:

   To control access to routes based on user roles -> Option C

4. Quick Check:

   Role-based authorization = Access control by roles [OK]

Hint: Remember: roles decide who can access what [OK]

Common Mistakes:

• Confusing authorization with authentication
• Thinking it manages database or HTTP parsing
• Mixing up roles with user data formatting

2. Which decorator is commonly used in NestJS to specify roles allowed on a route?

easy

A. @Roles()

B. @UseGuards()

C. @Controller()

D. @Get()

Solution

1. Step 1: Identify role-specifying decorators

   In NestJS, @Roles() decorator marks which roles can access a route.

2. Step 2: Differentiate from other decorators

   @UseGuards() applies guards, @Controller() defines controllers, @Get() defines HTTP GET routes.

3. Final Answer:

   @Roles() -> Option A

4. Quick Check:

   @Roles() sets allowed roles [OK]

Hint: Look for decorator naming roles directly [OK]

Common Mistakes:

• Using @UseGuards() to specify roles directly
• Confusing route decorators with role decorators
• Missing that @Roles() is custom, not built-in

3. Given this code snippet, what will happen when a user with role 'user' accesses the route?

@Roles('admin')
@Get('admin-data')
getAdminData() {
  return 'Secret admin data';
}

medium

A. The user will receive 'Secret admin data'

B. The user will get a 403 Forbidden error

C. The route will return undefined

D. The server will crash with an error

Solution

1. Step 1: Check the role required by the route

   The route requires 'admin' role via @Roles('admin').

2. Step 2: Compare with user's role

   User has role 'user', which does not match 'admin'.

3. Final Answer:

   The user will get a 403 Forbidden error -> Option B

4. Quick Check:

   Role mismatch causes 403 Forbidden [OK]

Hint: If user role ≠ required role, access denied [OK]

Common Mistakes:

• Assuming any role can access
• Thinking route returns undefined on denial
• Expecting server crash on role mismatch

4. Identify the error in this NestJS guard code for role checking:

canActivate(context: ExecutionContext): boolean {
  const request = context.switchToHttp().getRequest();
  const user = request.user;
  const roles = this.reflector.get('roles', context.getHandler());
  if (!roles) {
    return true;
  }
  return roles.includes(user.role);
}

medium

A. Missing async keyword on canActivate

B. Returning true when roles are not defined

C. Using getHandler() instead of getClass() for roles

D. Not checking if user exists before accessing user.role

Solution

1. Step 1: Review user role access

   The code accesses user.role without verifying if user is defined.

2. Step 2: Identify potential runtime error

   If user is undefined, accessing user.role causes an error.

3. Final Answer:

   Not checking if user exists before accessing user.role -> Option D

4. Quick Check:

   Always check user before role access [OK]

Hint: Check user object exists before role check [OK]

Common Mistakes:

• Assuming user is always present
• Confusing getHandler() and getClass() usage
• Thinking async is required for synchronous guard

5. How can you combine role-based authorization with route-level guards to allow access only if the user has either 'admin' or 'manager' role in NestJS?

hard

A. Use @Roles('admin', 'manager') decorator and a RolesGuard that checks for any matching role

B. Use two separate @Roles decorators, one for 'admin' and one for 'manager', on the same route

C. Use @UseGuards(AdminGuard, ManagerGuard) without @Roles decorator

D. Check roles manually inside the controller method without decorators or guards

Solution

1. Step 1: Understand role decorator usage

   @Roles() accepts multiple roles to allow any of them access.

2. Step 2: Use a guard that checks if user role matches any allowed role

   The RolesGuard reads roles from metadata and checks if user role is included.

3. Final Answer:

   Use @Roles('admin', 'manager') decorator and a RolesGuard that checks for any matching role -> Option A

4. Quick Check:

   Multiple roles in @Roles() + guard = flexible access [OK]

Hint: Pass multiple roles in one @Roles() decorator [OK]

Common Mistakes:

• Using multiple @Roles decorators on one route
• Applying multiple guards instead of one flexible guard
• Skipping decorators and guards for manual checks