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Introduction:
A recent bug bounty discovery on HackerOne has exposed a critical flaw in role-based access control (RBAC) implementation. A security researcher identified that seemingly low-privilege roles, such as BillingObserver and LogsViewer, were granted unauthorized access to a sensitive database containing connection details. This case study underscores the pervasive threat of authorization bypass and the critical importance of rigorous server-side access control testing.
Learning Objectives:
- Understand the mechanics of Role-Based Access Control (RBAC) misconfigurations and privilege escalation.
- Learn how to test and verify access controls for all user roles within an application.
- Master essential command-line and API testing techniques to identify authorization flaws.
You Should Know:
1. Enumerating Application Roles and Permissions
Before testing, you must map all available roles and their intended permissions. This is often done by analyzing authentication responses or application configuration files.
Linux: Using curl and jq to analyze a JWT token for role claims after login
curl -s http://target.com/login -d '{"user":"test","pass":"test"}' -H "Content-Type: application/json" | jq '.token' | cut -d '.' -f 2 | base64 -d | jq
Step-by-step guide: This command chain authenticates to a target, extracts the JWT token from the JSON response, decodes its payload (the second part), and pretty-prints the JSON to reveal embedded claims like `roles` or privileges. Look for over-assigned permissions.
2. Testing for Horizontal Privilege Escalation
Horizontal escalation occurs when a user can access data of another user at the same privilege level. Test this by swapping user IDs in API requests.
Windows: Using PowerShell to manipulate session cookies and test API endpoints
$session = Invoke-WebRequest -Uri "http://target.com/login" -SessionVariable sv -Method Post -Body @{username='user1';password='pass1'}
$user2Data = Invoke-WebRequest -Uri "http://target.com/api/user/2/profile" -WebSession $sv -Headers @{"Authorization"="Bearer $($session.Content | ConvertFrom-Json).token"}
Step-by-step guide: This script logs in as user1, stores the session, and then attempts to access user2‘s profile endpoint using the same authenticated session. A successful response indicates a broken access control flaw.
3. Testing for Vertical Privilege Escalation
Vertical escalation is the core of this finding—where a lower-privileged user performs actions reserved for admins. Test every endpoint assigned to a low-privilege role.
Using Burp Suite's "Authz" extension or custom Intruder payloads to test all API paths with different role tokens. Alternatively, use a bash loop with curl: for endpoint in $(cat api_endpoints.txt); do curl -H "Authorization: Bearer $LOW_PRIVILEGE_TOKEN" -X GET "http://target.com$endpoint" -I | grep "HTTP/1.1 200" done
Step-by-step guide: This loop iterates through a list of API endpoints (api_endpoints.txt) and sends a request to each using a low-privilege user’s token. If any endpoint returns a 200 OK, it may indicate improper authorization.
4. Bypassing Front-End Controls via Direct API Access
Applications often enforce controls in the UI but not the backend. Always test direct API access.
Directly accessing an admin API endpoint with a non-admin token using curl
curl -X POST http://target.com/admin/createUser \
-H "Authorization: Bearer $SUPPORT_ANALYST_TOKEN" \
-H "Content-Type: application/json" \
-d '{"username":"attacker","password":"pwned","role":"admin"}'
Step-by-step guide: This command attempts to hit a critical admin functionality—creating a new user—using a token for a `SupportAnalyst` role. A success response indicates a severe server-side authorization failure.
5. Automating Role-Based Access Control Testing
Manual testing is inefficient. Automate with scripts to test all roles against all endpoints.
Python script snippet using requests library to test endpoints
import requests
s = requests.Session()
s.post("http://target.com/login", json={"user":"logs_viewer", "pass":"pass"})
endpoints = ["/api/db/connections", "/api/admin/users", "/api/billing/records"]
for ep in endpoints:
resp = s.get(f"http://target.com{ep}")
if resp.status_code == 200:
print(f"[!] UNAUTHORIZED ACCESS TO {ep}")
Step-by-step guide: This Python script automates the process. It logs in as a low-privilege role (logs_viewer) and then tests access to a list of sensitive endpoints. Any 200 response should be investigated immediately.
6. Hardening Database and API Access Controls
Mitigation requires strong server-side checks. Implement mandatory access control checks in every API handler.
// Node.js/Express middleware example for enforcing roles
function requireRole(role) {
return (req, res, next) => {
if (!req.user.roles.includes(role)) {
return res.status(403).send('Insufficient permissions');
}
next();
};
}
// Usage on an endpoint
app.get('/api/db/connections', requireRole('DatabaseAdmin'), (req, res) => {
// Handler logic
});
Step-by-step guide: This code defines middleware that checks if the authenticated user possesses the required role before proceeding. This check must be performed server-side on every request.
7. Auditing Cloud IAM and Database Permissions
Misconfigurations often originate in cloud Identity and Access Management (IAM) policies or database permissions.
AWS CLI command to list IAM policies attached to a specific role aws iam list-attached-role-policies --role-name LogsViewerRole Check the specific permissions granted by a policy aws iam get-policy-version --policy-arn arn:aws:iam::123456789012:policy/LogsViewerPolicy --version-id v1
Step-by-step guide: These commands audit what AWS IAM policies are attached to the `LogsViewerRole` and then retrieve the details of one policy to see the exact permissions granted. Overly permissive policies like `rds-db:` are a common culprit.
What Undercode Say:
- Key Takeaway 1: Never trust the UI. Authorization checks must be enforced rigorously on the server-side for every single request, regardless of the user interface’s limitations.
- Key Takeaway 2: The principle of least privilege is non-negotiable. Every role, especially seemingly harmless ones like `BillingObserver` or
LogsViewer, must be audited and granted only the absolute minimum permissions required to function.
This case is a classic example of a vulnerability that automated scanners often miss. It requires a manual, thorough understanding of the application’s business logic and intended user permissions. The financial reward reflects the high impact of such a find—exposure of database connection strings could lead to a full organizational breach. This underscores a systemic issue in development: prioritizing functionality over security in access control implementation.
Prediction:
The frequency and impact of authorization bypass vulnerabilities will continue to escalate as applications grow more complex, integrating numerous microservices and third-party APIs. We predict a shift-left movement where RBAC testing will become a mandatory part of CI/CD pipelines, driven by automated security tools that can simulate complex user interactions. Furthermore, expect regulatory frameworks like GDPR and CCPA to levy heavier fines for such data exposure incidents, making proactive access control testing a critical financial imperative, not just a security best practice.
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IT/Security Reporter URL:
Reported By: 0xammaryasser Bugbounty – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
