JWT Claims & Scopes in AWS Serverless

1. Introduction

JSON Web Tokens (JWT) are a compact and self-contained way to represent information between two parties securely. In a serverless environment like AWS, JWT is commonly used for authentication and authorization, making it crucial to understand its claims and scopes.

2. JWT Claims

Claims are statements about an entity (typically, the user) and additional data. There are three types of claims:

• Registered Claims: These are predefined claims such as iss (issuer), exp (expiration), and sub (subject).
• Public Claims: These are defined by those using JWTs and should be collision-resistant.
• Private Claims: These are custom claims created to share information between parties that agree on using them.

2.1 Example of JWT Claims

{
  "iss": "https://yourdomain.com",
  "exp": 1300819380,
  "sub": "1234567890",
  "name": "John Doe",
  "admin": true
}

3. JWT Scopes

Scopes are a way to limit what access a user has within the application. They are often used in OAuth 2.0 to define the permissions granted to the application on behalf of the user.

3.1 Example of JWT Scopes

{
  "scope": "read:messages write:messages"
}

4. Implementing JWT in AWS

To implement JWT in a serverless architecture using AWS, follow these steps:

1. Set up an API Gateway to handle incoming requests.
2. Create a Lambda function for authentication.
3. Generate a JWT token upon user login.
4. Return the token to the client and use it for subsequent requests.
5. Validate the token in the API Gateway using Lambda Authorizers.

4.1 Flowchart for JWT Implementation

graph TD;
            A[Start] --> B[User Login];
            B --> C[Generate JWT Token];
            C --> D[Return Token to Client];
            D --> E[Client Makes Request];
            E --> F[Validate Token];
            F --> G{Token Valid?};
            G -->|Yes| H[Proceed with Request];
            G -->|No| I[Return Unauthorized];
        

5. Best Practices

• Always use HTTPS to protect the token during transmission.
• Keep the token expiration short and implement refresh tokens.
• Use strong signing algorithms (e.g., RS256) for tokens.
• Limit the scope of the JWT to only what is necessary.
• Validate the token on every request to ensure its integrity.

6. FAQ