Fix health checks not working behind load balancers

The change in
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24199 caused
requests coming from a load balancer to arrive as 127.0.0.1 instead of
the actual IP.

`Rack::Request#ip` behaves slightly differently different than
`ActionDispatch::Request#remote_ip`: the former will return the first
X-Forwarded-For IP if all of the IPs are trusted proxies, while the
second one filters out all proxies and falls back to REMOTE_ADDR, which
is 127.0.0.1.

For now, we can revert back to using `Rack::Request` because these
middlewares don't manipulate parameters. The actual fix problem involves
fixing Rails: https://github.com/rails/rails/issues/28436.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/58573

1 files changed, 29 insertions, 0 deletions

diff --git a/spec/lib/gitlab/middleware/basic_health_check_spec.rb b/spec/lib/gitlab/middleware/basic_health_check_spec.rb
index 187d903a5e1..86bdc479b66 100644
--- a/spec/lib/gitlab/middleware/basic_health_check_spec.rb
+++ b/spec/lib/gitlab/middleware/basic_health_check_spec.rb
@@ -28,6 +28,35 @@ describe Gitlab::Middleware::BasicHealthCheck do
       end
     end
 
+    context 'with X-Forwarded-For headers' do
+      let(:load_balancer_ip) { '1.2.3.4' }
+
+      before do
+        env['HTTP_X_FORWARDED_FOR'] = "#{load_balancer_ip}, 127.0.0.1"
+        env['REMOTE_ADDR'] = '127.0.0.1'
+        env['PATH_INFO'] = described_class::HEALTH_PATH
+      end
+
+      it 'returns 200 response when endpoint is allowed' do
+        allow(Settings.monitoring).to receive(:ip_whitelist).and_return([load_balancer_ip])
+        expect(app).not_to receive(:call)
+
+        response = middleware.call(env)
+
+        expect(response[0]).to eq(200)
+        expect(response[1]).to eq({ 'Content-Type' => 'text/plain' })
+        expect(response[2]).to eq(['GitLab OK'])
+      end
+
+      it 'returns 404 when whitelist is not configured' do
+        allow(Settings.monitoring).to receive(:ip_whitelist).and_return([])
+
+        response = middleware.call(env)
+
+        expect(response[0]).to eq(404)
+      end
+    end
+
     context 'whitelisted IP' do
       before do
         env['REMOTE_ADDR'] = '127.0.0.1'