Merge branch 'security-dns-ssrf-bypass' into 'master'

Server Side Request Forgery mitigation bypass

Closes #2872

See merge request gitlab/gitlabhq!3205

changelogs/unreleased/security-dns-ssrf-bypass.yml

+---
+title: Fix Server Side Request Forgery mitigation bypass
+merge_request:
+author:
+type: security

lib/gitlab/url_blocker.rb

@@ -85,9 +85,9 @@ module Gitlab
       # we'll be making the request to the IP address, instead of using the hostname.
       def enforce_uri_hostname(addrs_info, uri, hostname, dns_rebind_protection)
         address = addrs_info.first
-        ip_address = address&.ip_address
-        return [uri, nil] unless dns_rebind_protection && ip_address && ip_address != hostname
+        ip_address = address.ip_address
+        return [uri, nil] unless dns_rebind_protection && ip_address != hostname
         uri = uri.dup
         uri.hostname = ip_address
@@ -111,6 +111,15 @@ module Gitlab
           addr.ipv6_v4mapped? ? addr.ipv6_to_ipv4 : addr
         end
       rescue SocketError
+        # In the test suite we use a lot of mocked urls that are either invalid or
+        # don't exist. In order to avoid modifying a ton of tests and factories
+        # we allow invalid urls unless the environment variable RSPEC_ALLOW_INVALID_URLS
+        # is not true
+        return if Rails.env.test? && ENV['RSPEC_ALLOW_INVALID_URLS'] == 'true'
+
+        # If the addr can't be resolved or the url is invalid (i.e http://1.1.1.1.1)
+        # we block the url
+        raise BlockedUrlError, "Host cannot be resolved or invalid"
       end
       def validate_local_request(address_info:, allow_localhost:, allow_local_network:)

spec/lib/gitlab/url_blocker_spec.rb

@@ -68,6 +68,16 @@ describe Gitlab::UrlBlocker do
           expect(uri).to eq(Addressable::URI.parse('https://example.org'))
           expect(hostname).to eq(nil)
         end
+
+        context 'when it cannot be resolved' do
+          let(:import_url) { 'http://foobar.x' }
+
+          it 'raises error' do
+            stub_env('RSPEC_ALLOW_INVALID_URLS', 'false')
+
+            expect { described_class.validate!(import_url) }.to raise_error(described_class::BlockedUrlError)
+          end
+        end
       end
       context 'when the URL hostname is an IP address' do
@@ -79,6 +89,16 @@ describe Gitlab::UrlBlocker do
           expect(uri).to eq(Addressable::URI.parse('https://93.184.216.34'))
           expect(hostname).to be(nil)
         end
+
+        context 'when it is invalid' do
+          let(:import_url) { 'http://1.1.1.1.1' }
+
+          it 'raises an error' do
+            stub_env('RSPEC_ALLOW_INVALID_URLS', 'false')
+
+            expect { described_class.validate!(import_url) }.to raise_error(described_class::BlockedUrlError)
+          end
+        end
       end
     end
   end
@@ -180,8 +200,6 @@ describe Gitlab::UrlBlocker do
     end
     it 'returns true for a non-alphanumeric hostname' do
-      stub_resolv
-
       aggregate_failures do
         expect(described_class).to be_blocked_url('ssh://-oProxyCommand=whoami/a')
@@ -300,10 +318,6 @@ describe Gitlab::UrlBlocker do
     end
     context 'when enforce_user is' do
-      before do
-        stub_resolv
-      end
-
       context 'false (default)' do
         it 'does not block urls with a non-alphanumeric username' do
           expect(described_class).not_to be_blocked_url('ssh://-oProxyCommand=whoami@example.com/a')
@@ -351,6 +365,18 @@ describe Gitlab::UrlBlocker do
         expect(described_class.blocked_url?('https://git‌lab.com/foo/foo.bar', ascii_only: true)).to be true
       end
     end
+
+    it 'blocks urls with invalid ip address' do
+      stub_env('RSPEC_ALLOW_INVALID_URLS', 'false')
+
+      expect(described_class).to be_blocked_url('http://8.8.8.8.8')
+    end
+
+    it 'blocks urls whose hostname cannot be resolved' do
+      stub_env('RSPEC_ALLOW_INVALID_URLS', 'false')
+
+      expect(described_class).to be_blocked_url('http://foobar.x')
+    end
   end
   describe '#validate_hostname' do
@@ -382,10 +408,4 @@ describe Gitlab::UrlBlocker do
       end
     end
   end
-
-  # Resolv does not support resolving UTF-8 domain names
-  # See https://bugs.ruby-lang.org/issues/4270
-  def stub_resolv
-    allow(Resolv).to receive(:getaddresses).and_return([])
-  end
 end

spec/spec_helper.rb

@@ -3,6 +3,7 @@ SimpleCovEnv.start!
 ENV["RAILS_ENV"] = 'test'
 ENV["IN_MEMORY_APPLICATION_SETTINGS"] = 'true'
+ENV["RSPEC_ALLOW_INVALID_URLS"] = 'true'
 require File.expand_path('../config/environment', __dir__)
 require 'rspec/rails'