AuthN vs AuthZ Essentials in API Security Testing Quiz

Explore the key differences and practical considerations between authentication (AuthN) and authorization (AuthZ) in API security testing. This quiz helps clarify common concepts, test scenarios, and typical vulnerabilities encountered when assessing API protection mechanisms.

1. Identifying Authentication in API Contexts

   During API testing, what action primarily verifies the identity of a user before granting access to the system?

   1. Authentication
   2. Authorization
   3. Access Control List
   4. Token Revocation

   Explanation: Authentication is the process of confirming the identity of a user, typically by requiring valid credentials such as a password or token, before allowing access. Authorization, on the other hand, comes after authentication and determines what the authenticated user is permitted to do. An Access Control List specifies permissions, but does not perform identity verification. Token revocation is used to invalidate access, not to verify identity.

2. Understanding Authorization in an API Scenario

   If an API user is able to access administrative endpoints after logging in as a regular user, which security mechanism has likely failed?

   1. Authorization
   2. Authentication
   3. Auditing
   4. Encryption

   Explanation: Authorization determines what resources or actions a user is permitted to access after they have authenticated. If a regular user gains access to admin features, this is an authorization failure. Authentication verifies identity but doesn't control permissions. Auditing involves logging activity, not access control. Encryption protects data transmission, not access levels.

3. Typical Test Technique for Authorization Checks

   Which of the following best demonstrates a test for insufficient authorization in API endpoints?

   1. Accessing another user's resource with your valid token
   2. Logging in with invalid credentials repeatedly
   3. Monitoring response times for endpoints
   4. Inspecting API documentation for parameter lists

   Explanation: Testing for insufficient authorization involves manipulating requests to access data or actions that belong to others using valid credentials, thereby verifying if access controls are enforced. Logging in with invalid credentials tests authentication, not authorization. Monitoring response times is for performance, not access control testing. Reviewing documentation does not actively test access permissions.

4. Differentiating AuthN and AuthZ Failures

   Which message likely results from a failed authentication attempt rather than a failed authorization?

   1. Invalid username or password
   2. Permission denied
   3. Forbidden: insufficient scope
   4. Access to the API endpoint is not allowed

   Explanation: An 'Invalid username or password' message indicates that the submitted credentials do not match an existing user, signaling an authentication failure. 'Permission denied' and 'Forbidden: insufficient scope' both refer to authorization failures where authenticated users lack proper permissions. 'Access to the API endpoint is not allowed' usually refers to authorization as well.

5. Core API Security Principles

   When designing API security tests, which best practice ensures proper distinction between authentication (AuthN) and authorization (AuthZ) mechanisms?

   1. Testing identity verification and access permissions separately
   2. Using flexible endpoint naming conventions
   3. Relying solely on strong password policies
   4. Encrypting all API responses

   Explanation: Separating tests for authentication (identity verification) and authorization (access rights) ensures both areas are covered and vulnerabilities are not overlooked. Naming conventions do not impact security controls directly. Strong password policies help authentication but do not address authorization. Encryption protects data but does not distinguish between AuthN and AuthZ checks.