OAuth for Single Page Applications

1. Introduction

OAuth is an open standard for access delegation, commonly used as a way to grant websites or applications limited access to a user's information without exposing passwords. This lesson focuses on implementing OAuth in Single Page Applications (SPAs) for enhanced security.

2. Key Concepts

3. OAuth Flow

flowchart TD
    A[User] -->|1. Request| B[Client Application]
    B -->|2. Redirect| C[Authorization Server]
    C -->|3. Authorize| A
    A -->|4. Redirect with Code| C
    C -->|5. Send Code| B
    B -->|6. Exchange Code for Token| D[Authorization Server]
    D -->|7. Send Tokens| B
    B -->|8. Access Resource| E[Resource Server]
    E -->|9. Provide Resource| B
        

4. Implementation

To implement OAuth in a Single Page Application, follow these steps:

1. Register your application with the OAuth provider to obtain client credentials.
2. Implement the authorization code flow.
3. Store the tokens securely (preferably in memory or secure storage).
4. Make API calls using the access token.
5. Handle token expiration and refresh using the refresh token.

const CLIENT_ID = 'your_client_id';
const REDIRECT_URI = 'your_redirect_uri';
const AUTH_URL = 'https://provider.com/oauth/authorize';
const TOKEN_URL = 'https://provider.com/oauth/token';

// Step 1: Redirect to authorization server
function redirectToAuth() {
    const url = `${AUTH_URL}?response_type=code&client_id=${CLIENT_ID}&redirect_uri=${REDIRECT_URI}`;
    window.location.href = url;
}

// Step 2: Handle redirect and exchange code for tokens
async function handleRedirect() {
    const code = new URL(window.location.href).searchParams.get('code');
    if (code) {
        const response = await fetch(TOKEN_URL, {
            method: 'POST',
            headers: {'Content-Type': 'application/json'},
            body: JSON.stringify({
                grant_type: 'authorization_code',
                code: code,
                redirect_uri: REDIRECT_URI,
                client_id: CLIENT_ID,
            }),
        });
        const data = await response.json();
        // Store tokens securely
    }
}
                

5. Best Practices

• Use short-lived access tokens and implement refresh tokens.
• Store sensitive information (like tokens) securely.
• Regularly review and update your OAuth implementation.
• Limit the scope of access tokens to only what is necessary.

6. FAQ