mastodon-glitch/lib/action_dispatch/remote_ip_extensions.rb

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# frozen_string_literal: true
# Mastodon is not made to be directly accessed without a reverse proxy.
# This monkey-patch prevents remote IP address spoofing when being accessed
# directly.
#
# See PR: https://github.com/rails/rails/pull/51610
# In addition to the PR above, it also raises an error if a request with
# `X-Forwarded-For` or `Client-Ip` comes directly from a client without
# going through a trusted proxy.
# rubocop:disable all -- This is a mostly vendored file
module ActionDispatch
class RemoteIp
module GetIpExtensions
def calculate_ip
# Set by the Rack web server, this is a single value.
remote_addr = ips_from(@req.remote_addr).last
# Could be a CSV list and/or repeated headers that were concatenated.
client_ips = ips_from(@req.client_ip).reverse!
forwarded_ips = ips_from(@req.x_forwarded_for).reverse!
# `Client-Ip` and `X-Forwarded-For` should not, generally, both be set. If they
# are both set, it means that either:
#
# 1) This request passed through two proxies with incompatible IP header
# conventions.
#
# 2) The client passed one of `Client-Ip` or `X-Forwarded-For`
# (whichever the proxy servers weren't using) themselves.
#
# Either way, there is no way for us to determine which header is the right one
# after the fact. Since we have no idea, if we are concerned about IP spoofing
# we need to give up and explode. (If you're not concerned about IP spoofing you
# can turn the `ip_spoofing_check` option off.)
should_check_ip = @check_ip && client_ips.last && forwarded_ips.last
if should_check_ip && !forwarded_ips.include?(client_ips.last)
# We don't know which came from the proxy, and which from the user
raise IpSpoofAttackError, "IP spoofing attack?! " \
"HTTP_CLIENT_IP=#{@req.client_ip.inspect} " \
"HTTP_X_FORWARDED_FOR=#{@req.x_forwarded_for.inspect}"
end
# NOTE: Mastodon addition to make sure we don't get requests from a non-trusted client
if @check_ip && (forwarded_ips.last || client_ips.last) && !@proxies.any? { |proxy| proxy === remote_addr }
raise IpSpoofAttackError, "IP spoofing attack?! client #{remote_addr} is not a trusted proxy " \
"HTTP_CLIENT_IP=#{@req.client_ip.inspect} " \
"HTTP_X_FORWARDED_FOR=#{@req.x_forwarded_for.inspect}"
end
# We assume these things about the IP headers:
#
# - X-Forwarded-For will be a list of IPs, one per proxy, or blank
# - Client-Ip is propagated from the outermost proxy, or is blank
# - REMOTE_ADDR will be the IP that made the request to Rack
ips = forwarded_ips + client_ips
ips.compact!
# If every single IP option is in the trusted list, return the IP that's
# furthest away
filter_proxies([remote_addr] + ips).first || ips.last || remote_addr
end
end
end
end
ActionDispatch::RemoteIp::GetIp.prepend(ActionDispatch::RemoteIp::GetIpExtensions)
# rubocop:enable all