Add cloudflare? method to determine if request passed through CF #149
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The `request.cloudflare?` method can be used in a Rack::Attack blocklist rule
to block traffic that hasn't passed through CloudFlare.
For instance:
```ruby
Rack::Attack.blocklist('CloudFlare WAF bypass') do |req|
!req.cloudflare?
end
```
Note that the request may optionally pass through additional trusted
proxies, so it will return true for any of these scenarios:
* `REMOTE_ADDR` = CloudFlare
* `REMOTE_ADDR` = *trusted_proxy*, `X_HTTP_FORWARDED_FOR` = CloudFlare,...
* `REMOTE_ADDR` = *trusted_proxy*, `X_HTTP_FORWARDED_FOR` = *trusted_proxy2*,CloudFlare,...
but it will return false if CloudFlare comes after the trusted prefix of
`X-Forwarded-For`.
modosc
requested changes
Aug 31, 2024
* Break up tests to only have one expectation per spec * Reduce line lengths
|
Thanks for the quick reply! Rubocop warnings are fixed. |
geoffharcourt
added a commit
to geoffharcourt/cloudflare-rails
that referenced
this pull request
Oct 4, 2024
In modosc#149 we got the extremely helpful `Request#cloudflare?` method which can assist with checking if a request has been proxied through Cloudflare. The method checks that there's an unbroken chain of trust from the `REMOTE_ADDR` (if it exists) through forwarded IPs that only includes trusted internal proxies and Cloudflare IP addresses. Each proxy in the chain is supposed to append the IP of the traffic it received to the *right side* of `X-Forwarded-For`. This means that after evaluating `REMOTE_ADDR` we should be looking at addresses in `X-Forwarded-For` starting on the right side, not on the left. https://github.com/modosc/cloudflare-rails/blob/311875eef57862ecf050fb87415c56ea4823486a/lib/cloudflare_rails/check_trusted_proxies.rb#L23-L25 This ordering means that if a request has the original client as the first address in `X-Forwarded-For` that we'll incorrectly reject it. It also means that an attacker could craft a forged `X-Forwarded-For` that starts with a Cloudflare IP and smuggle in a request that appears to be valid to the method's logic. The fix here is to continue to look at `REMOTE_ADDR` first but then to look at `X-Forwarded-For` in right-to-left order until we run out of trusted IP addresses (whether internal proxies or Cloudflare IPs). Fix modosc#161
modosc
pushed a commit
that referenced
this pull request
Oct 7, 2024
In #149 we got the extremely helpful `Request#cloudflare?` method which can assist with checking if a request has been proxied through Cloudflare. The method checks that there's an unbroken chain of trust from the `REMOTE_ADDR` (if it exists) through forwarded IPs that only includes trusted internal proxies and Cloudflare IP addresses. Each proxy in the chain is supposed to append the IP of the traffic it received to the *right side* of `X-Forwarded-For`. This means that after evaluating `REMOTE_ADDR` we should be looking at addresses in `X-Forwarded-For` starting on the right side, not on the left. https://github.com/modosc/cloudflare-rails/blob/311875eef57862ecf050fb87415c56ea4823486a/lib/cloudflare_rails/check_trusted_proxies.rb#L23-L25 This ordering means that if a request has the original client as the first address in `X-Forwarded-For` that we'll incorrectly reject it. It also means that an attacker could craft a forged `X-Forwarded-For` that starts with a Cloudflare IP and smuggle in a request that appears to be valid to the method's logic. The fix here is to continue to look at `REMOTE_ADDR` first but then to look at `X-Forwarded-For` in right-to-left order until we run out of trusted IP addresses (whether internal proxies or Cloudflare IPs). Fix #161
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The
request.cloudflare?method can be used in a Rack::Attack blocklist rule to block traffic that hasn't passed through CloudFlare.For instance:
Note that the request may optionally pass through additional trusted proxies, so it will return true for any of these scenarios:
REMOTE_ADDR= CloudFlareREMOTE_ADDR= trusted_proxy,X_HTTP_FORWARDED_FOR= CloudFlare,...REMOTE_ADDR= trusted_proxy,X_HTTP_FORWARDED_FOR= trusted_proxy2,CloudFlare,...but it will return false if CloudFlare comes after the trusted prefix of
X-Forwarded-For.