Yamcs has No Rate Limiting on Authentication Endpoint

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:

// 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

# 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:

// 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)
}