Add Workhorse support for HTTPS backend

workhorse/internal/upstream/roundtripper/roundtripper.go

@@ -2,6 +2,7 @@ package roundtripper
 
 import (
 	"context"
+	"crypto/tls"
 	"fmt"
 	"net"
 	"net/http"
@@ -15,10 +16,6 @@ import (
 )
 
 func mustParseAddress(address, scheme string) string {
-	if scheme == "https" {
-		panic("TLS is not supported for backend connections")
-	}
-
 	for _, suffix := range []string{"", ":" + scheme} {
 		address += suffix
 		if host, port, err := net.SplitHostPort(address); err == nil && host != "" && port != "" {
@@ -31,9 +28,14 @@ func mustParseAddress(address, scheme string) string {
 
 // NewBackendRoundTripper returns a new RoundTripper instance using the provided values
 func NewBackendRoundTripper(backend *url.URL, socket string, proxyHeadersTimeout time.Duration, developmentMode bool) http.RoundTripper {
+	return newBackendRoundTripper(backend, socket, proxyHeadersTimeout, developmentMode, nil)
+}
+
+func newBackendRoundTripper(backend *url.URL, socket string, proxyHeadersTimeout time.Duration, developmentMode bool, tlsConf *tls.Config) http.RoundTripper {
 	// Copied from the definition of http.DefaultTransport. We can't literally copy http.DefaultTransport because of its hidden internal state.
 	transport, dialer := newBackendTransport()
 	transport.ResponseHeaderTimeout = proxyHeadersTimeout
+	transport.TLSClientConfig = tlsConf
 
 	if backend != nil && socket == "" {
 		address := mustParseAddress(backend.Host, backend.Scheme)

workhorse/internal/upstream/roundtripper/roundtripper_test.go

 package roundtripper
 
 import (
+	"crypto/tls"
+	"crypto/x509"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
 	"strconv"
 	"testing"
 
@@ -12,6 +19,7 @@ func TestMustParseAddress(t *testing.T) {
 		{"1.2.3.4:56", "http", "1.2.3.4:56"},
 		{"[::1]:23", "http", "::1:23"},
 		{"4.5.6.7", "http", "4.5.6.7:http"},
+		{"4.5.6.7", "https", "4.5.6.7:https"},
 	}
 	for i, example := range successExamples {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
@@ -23,7 +31,6 @@ func TestMustParseAddress(t *testing.T) {
 func TestMustParseAddressPanic(t *testing.T) {
 	panicExamples := []struct{ address, scheme string }{
 		{"1.2.3.4", ""},
-		{"1.2.3.4", "https"},
 	}
 
 	for i, panicExample := range panicExamples {
@@ -37,3 +44,50 @@ func TestMustParseAddressPanic(t *testing.T) {
 		})
 	}
 }
+
+func TestSupportsHTTPBackend(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(200)
+		fmt.Fprint(w, "successful response")
+	}))
+	defer ts.Close()
+
+	testNewBackendRoundTripper(t, ts, nil, "successful response")
+}
+
+func TestSupportsHTTPSBackend(t *testing.T) {
+	ts := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(200)
+		fmt.Fprint(w, "successful response")
+	}))
+	defer ts.Close()
+
+	certpool := x509.NewCertPool()
+	certpool.AddCert(ts.Certificate())
+	tlsClientConfig := &tls.Config{
+		RootCAs: certpool,
+	}
+
+	testNewBackendRoundTripper(t, ts, tlsClientConfig, "successful response")
+}
+
+func testNewBackendRoundTripper(t *testing.T, ts *httptest.Server, tlsClientConfig *tls.Config, expectedResponseBody string) {
+	t.Helper()
+
+	backend, err := url.Parse(ts.URL)
+	require.NoError(t, err, "parse url")
+
+	rt := newBackendRoundTripper(backend, "", 0, true, tlsClientConfig)
+
+	req, err := http.NewRequest("GET", ts.URL+"/", nil)
+	require.NoError(t, err, "build request")
+
+	response, err := rt.RoundTrip(req)
+	require.NoError(t, err, "perform roundtrip")
+	defer response.Body.Close()
+
+	body, err := ioutil.ReadAll(response.Body)
+	require.NoError(t, err)
+
+	require.Equal(t, expectedResponseBody, string(body))
+}