A possible host header injection attack have been identified in Invenio-App. For an attack to be possible, all conditions below must be met:
An example of a view which does not evalute request.host is a simple view using just url_for to generate an external URL (similar is possible when rendering just a Jinja template):
return url_for('index_url', _external=True)
This happens, because Werkzeug's trusted host feature, which APP_ALLOWED_HOSTS rely on, does not check the the list of trusted hosts in it's routing system that url_for is relying on.
Invenio-App v1.0.6 and v1.1.1 fully fix the issue.
Note, we strongly recommend (see Securing your instance) that you never route requests to your application with a wrong host header. The APP_ALLOWED_HOSTS configuration variable exists as an extra protective measure because it is easy to misconfigure your web server to allow requests with any host header.
You should ensure that you never route requests with a wrong host header to your application. The workaround depends on which web server you are using to proxy requests to your application. In general it involves ensuring that the web server has two virtual hosts defined:
Note, for instance in Nginx if you only configure the application virtual host, by default, it will also act as the default virtual host despite you having configured a whitelist of host headers.
Below is an example for Nginx. Note for clarity we have only included the virtual host for port 443, but this also extends to virtual hosts running on any other port.
Default virtual host
Notice, the server_name is _ and the listen directive has it marked as default_server.
listen 443 default_server;
listen [::]:443 default_server;
return 301 https://www.example.com;
Application virtual host
Notice, the server_name is set to the host header whitelist.
We strongly recommend that you use the method described in Workaround 1.
If you are not able to upgrade to the patched versions of Invenio-App, you can include the following code snippet in your application to force evaluation of request.hosts.
If you have any questions or comments about this advisory: