Add SSRF filter for HTTPX

Filtering in front of HTTPX calls is less secure, because it's vulnerable to
DNS rebinding. In addition to that it's also duplicate work, because all affected
callsites would have to make sure to "remember" SSRF filtering.

This SSRF filter is inspired by the original HTTPX SSRF Filter, but using our custom
IP address matcher that allows to configure safe IP addresses or ranges.

lib/open_project.rb

@@ -34,6 +34,7 @@ require "open_project/patches"
 require "open_project/mime_type"
 require "open_project/custom_styles/design"
 require "open_project/httpx_appsignal"
+require "open_project/httpx_ssrf_filter"
 require "redmine/plugin"
 
 require "csv"
@@ -62,6 +63,7 @@ module OpenProject
                 .with(headers: { "User-Agent" => "OpenProject #{OpenProject::VERSION.to_semver} HTTPX Client" })
                 .plugin(:auth)
                 .plugin(:webdav)
+                .plugin(HttpxSsrfFilter)
                 .with(
                   timeout: {
                     connect_timeout: OpenProject::Configuration.httpx_connect_timeout,

lib/open_project/httpx_ssrf_filter.rb

@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+#-- copyright
+# OpenProject is an open source project management software.
+# Copyright (C) the OpenProject GmbH
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License version 3.
+#
+# OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
+# Copyright (C) 2006-2013 Jean-Philippe Lang
+# Copyright (C) 2010-2013 the ChiliProject Team
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# See COPYRIGHT and LICENSE files for more details.
+#++
+
+module OpenProject
+  # An SSRF filter for HTTPX based on the original plugin.
+  # See https://gitlab.com/os85/httpx/-/blob/master/lib/httpx/plugins/ssrf_filter.rb
+  #
+  # The main difference is that we use our own subclass of `SsrfFilter` to perform the matching of unsafe IP addresses.
+  # We are thus consulting our own allow list of IP addresses before blocking an IP address.
+  module HttpxSsrfFilter
+    class ServerSideRequestForgeryError < HTTPX::Error; end
+
+    module ConnectionMethods
+      def initialize(*)
+        super
+      rescue ServerSideRequestForgeryError => e
+        # may raise when IPs are passed as options via :addresses
+        throw(:resolve_error, e)
+      end
+
+      def addresses=(addrs)
+        addrs.reject!(&SsrfProtection.method(:unsafe_ip_address?)) # rubocop:disable Performance/MethodObjectAsBlock
+
+        raise ServerSideRequestForgeryError, "#{@origin.host} has no public IP addresses" if addrs.empty?
+
+        super
+      end
+    end
+  end
+end