Pre-Authentication Authorization

TL;DR

You generally shouldn’t implement authorization *before* authentication. Authentication verifies who the user is, while authorization determines what they can do. Trying to authorize before knowing who a user is creates security risks and complexity. Focus on authenticating first, then applying authorization rules.

Why It’s Usually Wrong

Authorization relies on identity. Without knowing the user’s identity (established through authentication), you have no basis for deciding what access they should be granted. Here’s why pre-authentication authorization is problematic:

• Security Risks: You might grant access to someone pretending to be a different user, or allow anonymous users privileges they shouldn’t have.
• Complexity: You need workarounds (like temporary tokens) that add significant overhead and potential vulnerabilities.
• Broken Principles: It violates the fundamental security principle of least privilege – you’re giving access before verifying identity.

The Correct Order: Authentication First

Here’s the standard, secure approach:

1. Authentication: Verify the user’s identity (e.g., username/password, multi-factor authentication).
2. Authorization: Once authenticated, determine what resources and actions the user is allowed to access based on their role or permissions.

Common Scenarios & Solutions

Let’s look at some situations where people might *think* they need pre-authentication authorization and how to handle them correctly.

1. Rate Limiting

You want to limit the number of requests from a single source (IP address) to prevent abuse. This isn’t authorization; it’s a security measure applied before authentication, based on network characteristics, not user identity.

• Solution: Implement rate limiting at the load balancer or web server level.

# Example Nginx rate limiting configuration

limit_req_zone $binary_remote_addr zone=mylimit:10m rate=5r/s;

server {

  location /api/ {

    limit_req zone=mylimit burst=10 nodelay;

    ...