Enhanced data authenticity validation for profile images
import 'package:shelf/shelf.dart' as shelf;
shelf.Response handleRequest(shelf.Request request) {
var imageUrl = request.headers['imageUrl'];
var response = shelf.Response.ok('Image URL: $imageUrl');
return response;
}
In the above code, the
handleRequest
function is responsible for handling incoming requests. This function fetches the
imageUrl
from the request headers and sends it back in the response without any validation.
This is problematic as it does not validate whether the
imageUrl
is a valid image URL. An attacker could potentially use partial paths or URLs to craft complex attack vectors such as controlled redirects or CSRF (Cross-Site Request Forgery).
For example, an attacker could send a request with a malicious URL in the
imageUrl
header. Since the system does not validate the
imageUrl
, it would accept the malicious URL and potentially expose the system to a security risk.
In essence, the vulnerability lies in the lack of authenticity validation for the
imageUrl
data.
import 'dart:io';
import 'package:shelf/shelf.dart' as shelf;
import 'package:shelf_router/shelf_router.dart';
import 'package:shelf_csrf/shelf_csrf.dart';
import 'package:valid_url/valid_url.dart';
final _whitelist = ['trusteddomain1.com', 'trusteddomain2.com'];
shelf.Response handleRequest(shelf.Request request) {
var imageUrl = request.headers['imageUrl'];
// Validate the imageUrl
if (!isURL(imageUrl)) {
return shelf.Response(400, body: 'Invalid image URL');
}
// Check that the URL points to an actual image
var httpClient = HttpClient();
httpClient.headUrl(Uri.parse(imageUrl)).then((request) {
return request.close();
}).then((response) {
if (!response.headers.value('content-type').startsWith('image/')) {
return shelf.Response(400, body: 'URL does not point to an image');
}
});
// Check the domain against a whitelist
var uri = Uri.parse(imageUrl);
if (!_whitelist.contains(uri.host)) {
return shelf.Response(403, body: 'Image URL not from a trusted domain');
}
// Implement CSRF protection
var csrfMiddleware = createCsrfMiddleware(
randomString: generateRandomString,
allowOrigin: (origin) => _whitelist.contains(Uri.parse(origin).host),
);
var router = Router();
router.all('/', csrfMiddleware);
var response = shelf.Response.ok('Image URL: $imageUrl');
return response;
}
The updated code now includes several security measures to validate the image URL and prevent CSRF attacks.
Firstly, the
isURL
function from the
valid_url
package is used to validate that the
imageUrl
is a valid URL. If it's not, a 400 response is returned with a message indicating that the URL is invalid.
Next, a HEAD request is sent to the
imageUrl
using Dart's
HttpClient
. The 'Content-Type' header in the response is checked to ensure it starts with 'image/'. If it doesn't, a 400 response is returned with a message indicating that the URL does not point to an image.
The domain of the
imageUrl
is then checked against a whitelist of trusted domains. If the domain is not in the whitelist, a 403 response is returned with a message indicating that the image URL is not from a trusted domain.
Finally, CSRF protection is implemented using the
shelf_csrf
package. A CSRF middleware is created and added to the router. The
allowOrigin
function is used to restrict the origins that are allowed to send requests to the server to those in the whitelist.
The response is then returned as before, but now with the added security measures.