CSRF

Jan 1, 0001

Definition

Cross-Site Request Forgery (CSRF) is a web security vulnerability that allows an attacker to induce users to perform actions they do not intend to perform. This is achieved by exploiting the trust that a web application has in the user’s browser, allowing unauthorized commands to be transmitted from a user that the web application trusts. CSRF attacks are typically executed by tricking the user into submitting a malicious request, often via a link or a form embedded in a webpage controlled by the attacker.

Secure Settings Example

<form action="/transfer" method="POST">
  <input type="hidden" name="csrf_token" value="{{ csrf_token }}">
  <!-- Other form fields -->
  <button type="submit">Submit</button>
</form>

# Example in a Flask application
from flask import Flask, request, session, abort
import secrets

app = Flask(__name__)
app.secret_key = 'your_secret_key'

@app.before_request
def csrf_protect():
    if request.method == "POST":
        token = session.pop('_csrf_token', None)
        if not token or token != request.form.get('csrf_token'):
            abort(403)

def generate_csrf_token():
    if '_csrf_token' not in session:
        session['_csrf_token'] = secrets.token_hex(16)
    return session['_csrf_token']

app.jinja_env.globals['csrf_token'] = generate_csrf_token

Insecure Settings Example

<form action="/transfer" method="POST">
  <!-- No CSRF token included -->
  <!-- Other form fields -->
  <button type="submit">Submit</button>
</form>

# Example in a Flask application without CSRF protection
from flask import Flask, request

app = Flask(__name__)

@app.route('/transfer', methods=['POST'])
def transfer():
    # No CSRF token validation
    # Process the transfer
    return "Transfer completed"