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