added parsing for extended X-Forwarded-For headers to allow proxy API…

… registration in ipv4 (#80)

registration-api/api_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/golang/protobuf/proto"
 	zmq "github.com/pebbe/zmq4"
 	pb "github.com/refraction-networking/gotapdance/protobuf"
+	"github.com/stretchr/testify/require"
 )
 
 var (
@@ -333,3 +334,21 @@ func BenchmarkRegistration(b *testing.B) {
 		s.register(w, r)
 	}
 }
+
+func TestAPIGetClientAddr(t *testing.T) {
+
+	req, err := http.NewRequest("GET", "http://example.com", nil)
+	require.Nil(t, err)
+
+	req.RemoteAddr = "10.0.0.0"
+	require.Equal(t, "10.0.0.0", getRemoteAddr(req))
+
+	req.Header.Add("X-Forwarded-For", "192.168.1.1")
+	require.Equal(t, "192.168.1.1", getRemoteAddr(req))
+
+	req.Header.Set("X-Forwarded-For", "127.0.0.1, 192.168.0.0")
+	require.Equal(t, "127.0.0.1", getRemoteAddr(req))
+
+	req.Header.Set("X-Forwarded-For", "127.0.0.1,192.168.0.0")
+	require.Equal(t, "127.0.0.1", getRemoteAddr(req))
+}

registration-api/main.go

@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"os"
 	"strconv"
+	"strings"
 	"sync"
 
 	"github.com/BurntSushi/toml"
@@ -48,11 +49,23 @@ type server struct {
 	sock   *zmq.Socket
 }
 
-func (s *server) register(w http.ResponseWriter, r *http.Request) {
-	requestIP := r.RemoteAddr
+// Get the first element of the X-Forwarded-For header if it is available, this
+// will be the clients address if intermediate proxies follow X-Forwarded-For
+// specification (as seen here: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-For).
+// Otherwise return the remote address specified in the request.
+//
+// In the future this may need to handle True-Client-IP headers.
+func getRemoteAddr(r *http.Request) string {
 	if r.Header.Get("X-Forwarded-For") != "" {
-		requestIP = r.Header.Get("X-Forwarded-For")
+		addrList := r.Header.Get("X-Forwarded-For")
+		return strings.Trim(strings.Split(addrList, ",")[0], " \t")
 	}
+	return r.RemoteAddr
+}
+
+func (s *server) register(w http.ResponseWriter, r *http.Request) {
+	requestIP := getRemoteAddr(r)
+
 	if s.logClientIP {
 		s.logger.Printf("received %s request from IP %v with content-length %d\n", r.Method, requestIP, r.ContentLength)
 	} else {