A cross-site request forgery (CSRF) attack occurs when a trusted user of a web application can be forced, by an attacker, to perform sensitive
actions that he didn’t intend, such as updating his profile or sending a message, more generally anything that can change the state of the
application.
The attacker can trick the user/victim to click on a link, corresponding to the privileged action, or to visit a malicious web site that embeds a
hidden web request and as web browsers automatically include cookies, the actions can be authenticated and sensitive.
Ask Yourself Whether
- The web application uses cookies to authenticate users.
- There exist sensitive operations in the web application that can be performed when the user is authenticated.
- The state / resources of the web application can be modified by doing HTTP POST or HTTP DELETE requests for example.
There is a risk if you answered yes to any of those questions.
Recommended Secure Coding Practices
- Protection against CSRF attacks is strongly recommended:
- to be activated by default for all unsafe HTTP
methods.
- implemented, for example, with an unguessable CSRF token
- Of course all sensitive operations should not be performed with safe HTTP methods like
GET which are designed to be
used only for information retrieval.
Sensitive Code Example
Express.js CSURF middleware protection is not found on an unsafe HTTP method like POST
method:
let csrf = require('csurf');
let express = require('express');
let csrfProtection = csrf({ cookie: true });
let app = express();
// Sensitive: this operation doesn't look like protected by CSURF middleware (csrfProtection is not used)
app.post('/money_transfer', parseForm, function (req, res) {
res.send('Money transferred');
});
Protection provided by Express.js CSURF middleware is globally disabled on unsafe methods:
let csrf = require('csurf');
let express = require('express');
app.use(csrf({ cookie: true, ignoreMethods: ["POST", "GET"] })); // Sensitive as POST is unsafe method
Compliant Solution
Express.js CSURF middleware protection is used on unsafe methods:
let csrf = require('csurf');
let express = require('express');
let csrfProtection = csrf({ cookie: true });
let app = express();
app.post('/money_transfer', parseForm, csrfProtection, function (req, res) { // Compliant
res.send('Money transferred')
});
Protection provided by Express.js CSURF middleware is enabled on unsafe methods:
let csrf = require('csurf');
let express = require('express');
app.use(csrf({ cookie: true, ignoreMethods: ["GET"] })); // Compliant
See
