Prevention of uncontrolled external site redirects
class ApplicationController < ActionController::Base
def redirect
redirect_to params[:url]
end
end
In the above code snippet, the
redirect
method in
ApplicationController
is vulnerable to Host Header Injection. This is because it uses the
params[:url]
directly from the request to redirect the user. This parameter can be manipulated by an attacker to redirect users to malicious websites.
This vulnerability is known as Uncontrolled External Site Redirect or Open Redirect. It allows an attacker to craft a URL with a different
Host
header that points to a malicious website. When the user clicks on this link, they are redirected to the attacker's website instead of the expected location.
In the context of a Ruby on Rails application, this can lead to serious security issues as the attacker can use this vulnerability to steal sensitive information such as session cookies or perform phishing attacks.
class ApplicationController < ActionController::Base
def redirect
url = params[:url]
if url.present? && valid_url?(url)
redirect_to url
else
redirect_to root_path
end
end
private
def valid_url?(url)
allowed_domains = ['www.trusteddomain1.com', 'www.trusteddomain2.com']
uri = URI.parse(url)
allowed_domains.include?(uri.host)
rescue URI::InvalidURIError
false
end
end
The updated code includes a new method
valid_url?
that checks if the URL is part of a whitelist of allowed domains. This method is used in the
redirect
action to validate the
url
parameter before redirecting to it. If the URL is not valid or not present, the user is redirected to the root path of the application.
The
valid_url?
method uses the
URI.parse
method to parse the URL and extract the host. It then checks if this host is included in the
allowed_domains
array. If the URL is not valid or its host is not in the allowed domains, the method returns
false
.
This approach ensures that the application only redirects to trusted domains, preventing Host Header Injection attacks. It also provides a fallback redirect to the root path of the application in case the
url
parameter is not present or not valid. This improves the robustness of the application and enhances its security.