Add DNS rebinding protection settings

app/helpers/application_settings_helper.rb

@@ -127,6 +127,7 @@ module ApplicationSettingsHelper
       :akismet_api_key,
       :akismet_enabled,
       :allow_local_requests_from_hooks_and_services,
+      :dns_rebinding_protection_enabled,
       :archive_builds_in_human_readable,
       :authorized_keys_enabled,
       :auto_devops_enabled,

app/views/admin/application_settings/_outbound.html.haml

@@ -8,4 +8,12 @@
         = f.label :allow_local_requests_from_hooks_and_services, class: 'form-check-label' do
           Allow requests to the local network from hooks and services
+    .form-group
+      .form-check
+        = f.check_box :dns_rebinding_protection_enabled, class: 'form-check-input'
+        = f.label :dns_rebinding_protection_enabled, class: 'form-check-label' do
+          = _('Enforce DNS rebinding attack protection')
+        %span.form-text.text-muted
+          = _('Resolves IP addresses once and uses them to submit requests')
+
   = f.submit 'Save changes', class: "btn btn-success"

db/migrate/20190529142545_add_dns_rebinding_protection_enabled_to_application_settings.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddDnsRebindingProtectionEnabledToApplicationSettings < ActiveRecord::Migration[5.1]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_column_with_default(:application_settings, :dns_rebinding_protection_enabled,
+                            :boolean,
+                            default: true,
+                            allow_null: false)
+  end
+
+  def down
+    remove_column(:application_settings, :dns_rebinding_protection_enabled)
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
-ActiveRecord::Schema.define(version: 20190312071108) do
+ActiveRecord::Schema.define(version: 20190529142545) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -177,6 +177,7 @@ ActiveRecord::Schema.define(version: 20190312071108) do
     t.string "runners_registration_token_encrypted"
     t.integer "local_markdown_version", default: 0, null: false
     t.integer "first_day_of_week", default: 0, null: false
+    t.boolean "dns_rebinding_protection_enabled", default: true, null: false
     t.index ["usage_stats_set_by_user_id"], name: "index_application_settings_on_usage_stats_set_by_user_id", using: :btree
   end

lib/gitlab.rb

@@ -40,6 +40,7 @@ module Gitlab
   SUBDOMAIN_REGEX = %r{\Ahttps://[a-z0-9]+\.gitlab\.com\z}
   VERSION = File.read(root.join("VERSION")).strip.freeze
   INSTALLATION_TYPE = File.read(root.join("INSTALLATION_TYPE")).strip.freeze
+  HTTP_PROXY_ENV_VARS = %w(http_proxy https_proxy HTTP_PROXY HTTPS_PROXY).freeze
   def self.com?
     # Check `gl_subdomain?` as well to keep parity with gitlab.com
@@ -62,6 +63,10 @@ module Gitlab
     Object.const_defined?(:License)
   end
+  def self.http_proxy_env?
+    HTTP_PROXY_ENV_VARS.any? { |name| ENV[name] }
+  end
+
   def self.process_name
     return 'sidekiq' if Sidekiq.server?
     return 'console' if defined?(Rails::Console)

lib/gitlab/http_connection_adapter.rb

@@ -14,7 +14,8 @@ module Gitlab
     def connection
       begin
         @uri, hostname = Gitlab::UrlBlocker.validate!(uri, allow_local_network: allow_local_requests?,
-                                                           allow_localhost: allow_local_requests?)
+                                                           allow_localhost: allow_local_requests?,
+                                                           dns_rebind_protection: dns_rebind_protection?)
       rescue Gitlab::UrlBlocker::BlockedUrlError => e
         raise Gitlab::HTTP::BlockedUrlError, "URL '#{uri}' is blocked: #{e.message}"
       end
@@ -30,6 +31,12 @@ module Gitlab
       options.fetch(:allow_local_requests, allow_settings_local_requests?)
     end
+    def dns_rebind_protection?
+      return false if Gitlab.http_proxy_env?
+
+      Gitlab::CurrentSettings.dns_rebinding_protection_enabled?
+    end
+
     def allow_settings_local_requests?
       Gitlab::CurrentSettings.allow_local_requests_from_hooks_and_services?
     end

lib/gitlab/url_blocker.rb

@@ -18,7 +18,21 @@ module Gitlab
       # enforce_sanitization - Raises error if URL includes any HTML/CSS/JS tags and argument is true.
       #
       # Returns an array with [<uri>, <original-hostname>].
-      def validate!(url, ports: [], protocols: [], allow_localhost: false, allow_local_network: true, ascii_only: false, enforce_user: false, enforce_sanitization: false) # rubocop:disable Metrics/CyclomaticComplexity
+      # rubocop:disable Metrics/CyclomaticComplexity
+      # rubocop:disable Metrics/ParameterLists
+      def validate!(
+        url,
+        ports: [],
+        schemes: [],
+        allow_localhost: false,
+        allow_local_network: true,
+        ascii_only: false,
+        enforce_user: false,
+        enforce_sanitization: false,
+        dns_rebind_protection: true)
+        # rubocop:enable Metrics/CyclomaticComplexity
+        # rubocop:enable Metrics/ParameterLists
+
         return [nil, nil] if url.nil?
         # Param url can be a string, URI or Addressable::URI
@@ -45,15 +59,17 @@ module Gitlab
           return [uri, nil]
         end
+        protected_uri_with_hostname = enforce_uri_hostname(addrs_info, uri, hostname, dns_rebind_protection)
+
         # Allow url from the GitLab instance itself but only for the configured hostname and ports
-        return enforce_uri_hostname(addrs_info, uri, hostname) if internal?(uri)
+        return protected_uri_with_hostname if internal?(uri)
         validate_localhost!(addrs_info) unless allow_localhost
         validate_loopback!(addrs_info) unless allow_localhost
         validate_local_network!(addrs_info) unless allow_local_network
         validate_link_local!(addrs_info) unless allow_local_network
-        enforce_uri_hostname(addrs_info, uri, hostname)
+        protected_uri_with_hostname
       end
       def blocked_url?(*args)
@@ -74,17 +90,15 @@ module Gitlab
       #
       # The original hostname is used to validate the SSL, given in that scenario
       # we'll be making the request to the IP address, instead of using the hostname.
-      def enforce_uri_hostname(addrs_info, uri, hostname)
+      def enforce_uri_hostname(addrs_info, uri, hostname, dns_rebind_protection)
         address = addrs_info.first
         ip_address = address&.ip_address
-        if ip_address && ip_address != hostname
-          uri = uri.dup
-          uri.hostname = ip_address
-          return [uri, hostname]
-        end
-        [uri, nil]
+        return [uri, nil] unless dns_rebind_protection && ip_address && ip_address != hostname
+        uri = uri.dup
+        uri.hostname = ip_address
+        [uri, hostname]
       end
       def get_port(uri)

locale/gitlab.pot

@@ -3034,6 +3034,9 @@ msgstr ""
 msgid "Ends at (UTC)"
 msgstr ""
+msgid "Enforce DNS rebinding attack protection"
+msgstr ""
+
 msgid "Enter in your Bitbucket Server URL and personal access token below"
 msgstr ""
@@ -6438,6 +6441,9 @@ msgstr ""
 msgid "Resolved"
 msgstr ""
+msgid "Resolves IP addresses once and uses them to submit requests"
+msgstr ""
+
 msgid "Response metrics (AWS ELB)"
 msgstr ""

spec/features/admin/admin_settings_spec.rb

@@ -325,16 +325,19 @@ describe 'Admin updates settings' do
   end
   context 'Network page' do
-    it 'Enable outbound requests' do
+    it 'Changes Outbound requests settings' do
       visit network_admin_application_settings_path
       page.within('.as-outbound') do
         check 'Allow requests to the local network from hooks and services'
+        # Enabled by default
+        uncheck 'Enforce DNS rebinding attack protection'
         click_button 'Save changes'
       end
       expect(page).to have_content "Application settings saved successfully"
       expect(Gitlab::CurrentSettings.allow_local_requests_from_hooks_and_services).to be true
+      expect(Gitlab::CurrentSettings.dns_rebinding_protection_enabled).to be false
     end
   end

spec/lib/gitlab/http_connection_adapter_spec.rb

@@ -47,6 +47,38 @@ describe Gitlab::HTTPConnectionAdapter do
       end
     end
+    context 'when DNS rebinding protection is disabled' do
+      it 'sets up the connection' do
+        stub_application_setting(dns_rebinding_protection_enabled: false)
+
+        uri = URI('https://example.org')
+
+        connection = described_class.new(uri).connection
+
+        expect(connection).to be_a(Net::HTTP)
+        expect(connection.address).to eq('example.org')
+        expect(connection.hostname_override).to eq(nil)
+        expect(connection.addr_port).to eq('example.org')
+        expect(connection.port).to eq(443)
+      end
+    end
+
+    context 'when http(s) environment variable is set' do
+      it 'sets up the connection' do
+        stub_env('https_proxy' => 'https://my.proxy')
+
+        uri = URI('https://example.org')
+
+        connection = described_class.new(uri).connection
+
+        expect(connection).to be_a(Net::HTTP)
+        expect(connection.address).to eq('example.org')
+        expect(connection.hostname_override).to eq(nil)
+        expect(connection.addr_port).to eq('example.org')
+        expect(connection.port).to eq(443)
+      end
+    end
+
     context 'when local requests are allowed' do
       it 'sets up the connection' do
         uri = URI('https://example.org')

spec/lib/gitlab/url_blocker_spec.rb

@@ -46,6 +46,41 @@ describe Gitlab::UrlBlocker do
         expect(hostname).to be(nil)
       end
     end
+
+    context 'disabled DNS rebinding protection' do
+      context 'when URI is internal' do
+        let(:import_url) { 'http://localhost' }
+
+        it 'returns URI and no hostname' do
+          uri, hostname = described_class.validate!(import_url, dns_rebind_protection: false)
+
+          expect(uri).to eq(Addressable::URI.parse('http://localhost'))
+          expect(hostname).to be(nil)
+        end
+      end
+
+      context 'when the URL hostname is a domain' do
+        let(:import_url) { 'https://example.org' }
+
+        it 'returns URI and no hostname' do
+          uri, hostname = described_class.validate!(import_url, dns_rebind_protection: false)
+
+          expect(uri).to eq(Addressable::URI.parse('https://example.org'))
+          expect(hostname).to eq(nil)
+        end
+      end
+
+      context 'when the URL hostname is an IP address' do
+        let(:import_url) { 'https://93.184.216.34' }
+
+        it 'returns URI and no hostname' do
+          uri, hostname = described_class.validate!(import_url, dns_rebind_protection: false)
+
+          expect(uri).to eq(Addressable::URI.parse('https://93.184.216.34'))
+          expect(hostname).to be(nil)
+        end
+      end
+    end
   end
   describe '#blocked_url?' do

spec/lib/gitlab_spec.rb

@@ -109,4 +109,34 @@ describe Gitlab do
       expect(described_class.ee?).to eq(false)
     end
   end
+
+  describe '.http_proxy_env?' do
+    it 'returns true when lower case https' do
+      stub_env('https_proxy', 'https://my.proxy')
+
+      expect(described_class.http_proxy_env?).to eq(true)
+    end
+
+    it 'returns true when upper case https' do
+      stub_env('HTTPS_PROXY', 'https://my.proxy')
+
+      expect(described_class.http_proxy_env?).to eq(true)
+    end
+
+    it 'returns true when lower case http' do
+      stub_env('http_proxy', 'http://my.proxy')
+
+      expect(described_class.http_proxy_env?).to eq(true)
+    end
+
+    it 'returns true when upper case http' do
+      stub_env('HTTP_PROXY', 'http://my.proxy')
+
+      expect(described_class.http_proxy_env?).to eq(true)
+    end
+
+    it 'returns false when not set' do
+      expect(described_class.http_proxy_env?).to eq(false)
+    end
+  end
 end