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.

docker-compose.yml

@@ -36,17 +36,18 @@ x-op-backend: &backend
     target: develop
   <<: [*image, *restart_policy]
   environment:
+    DATABASE_URL: postgresql://${DB_USERNAME:-postgres}:${DB_PASSWORD:-postgres}@${DB_HOST:-db}:${DB_PORT:-5432}/${DB_DATABASE:-openproject}?pool=100
     LOCAL_DEV_CHECK: "${LOCAL_DEV_CHECK:?The docker-compose file for OpenProject has moved to https://github.com/opf/openproject-docker-compose}"
-    RAILS_ENV: development
     OPENPROJECT_CACHE__MEMCACHE__SERVER: cache:11211
+    OPENPROJECT_EDITION: ${OPENPROJECT_EDITION:-standard}
     OPENPROJECT_RAILS__CACHE__STORE: file_store
     OPENPROJECT_RAILS__RELATIVE__URL__ROOT: "${OPENPROJECT_RAILS__RELATIVE__URL__ROOT:-}"
-    DATABASE_URL: postgresql://${DB_USERNAME:-postgres}:${DB_PASSWORD:-postgres}@${DB_HOST:-db}:${DB_PORT:-5432}/${DB_DATABASE:-openproject}?pool=100
-    OPENPROJECT_EDITION: ${OPENPROJECT_EDITION:-standard}
+    OPENPROJECT_SSRF_PROTECTION_IP_ALLOWLIST: 0.0.0.0/0,::0/0 # disabling SSRF in dev to not interfere with local integrations (Nextcloud etc.)
     OPENPROJECT_WEB_MAX__THREADS: 1
     OPENPROJECT_WEB_MIN__THREADS: 1
     OPENPROJECT_WEB_WORKERS: 0
     PIDFILE: /home/dev/openproject/tmpfs/pids/server.pid
+    RAILS_ENV: development
   volumes:
     - ".:/home/dev/openproject"
     - "opdata:/var/openproject/assets"

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

spec/lib/open_project_spec.rb

@@ -0,0 +1,74 @@
+# 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.
+#++
+
+require "spec_helper"
+
+RSpec.describe OpenProject do
+  describe ".httpx" do
+    subject(:httpx) { described_class.httpx }
+
+    let(:public_endpoint) { "https://openproject.org/rspec-test" }
+    let(:private_endpoint) { "https://localhost/rspec-test" }
+
+    it "sets a proper User-Agent header", :webmock do
+      stub_request(:get, public_endpoint).to_return(status: 204)
+
+      httpx.get(public_endpoint)
+      expect(WebMock).to have_requested(:get, public_endpoint)
+        .with(headers: { "User-Agent": /OpenProject \d+\.\d+\.\d+ HTTPX Client/ })
+    end
+
+    # We can't use webmock for these tests, as it would interfere too early and thus we couldn't test
+    # whether corresponding requests would've been made
+    describe "SSRF filtering" do
+      it "includes SSRF filtering for private IP addresses" do
+        result = httpx.get(private_endpoint)
+        expect(result.error).to be_a(OpenProject::HttpxSsrfFilter::ServerSideRequestForgeryError)
+      end
+
+      it "does not filter requests to public IP addresses" do
+        result = httpx.get(public_endpoint)
+        expect(result.error).to be_nil
+      end
+
+      context "when local IP addresses are allowed" do
+        before do
+          allow(OpenProject::Configuration).to receive(:ssrf_protection_ip_allowlist)
+            .and_return([IPAddr.new("127.0.0.1"), IPAddr.new("::1")])
+        end
+
+        it "does not filter local requests" do
+          result = httpx.get(private_endpoint)
+          expect(result.error).not_to be_a(OpenProject::HttpxSsrfFilter::ServerSideRequestForgeryError)
+        end
+      end
+    end
+  end
+end