From c6fdfc9cd5c54751b28e82199d87e82fab9adaf2 Mon Sep 17 00:00:00 2001
From: Richard <richard.scothern@gmail.com>
Date: Tue, 24 Mar 2015 16:46:08 -0700
Subject: [PATCH] Attempt to identify remote IP addresses for requests which
 come through proxies.

Add a function to examine X-Forward-For and X-Real-Ip headers for
originating IP addresses.  Use RemoteAddr for notification request
record and HTTP request context.
---
 context/http.go         | 25 +++++++++++++++++++++-
 context/http_test.go    | 47 +++++++++++++++++++++++++++++++++++++++++
 notifications/bridge.go |  4 +++-
 3 files changed, 74 insertions(+), 2 deletions(-)

diff --git a/context/http.go b/context/http.go
index 357f0dc3..01600c35 100644
--- a/context/http.go
+++ b/context/http.go
@@ -17,11 +17,34 @@ var (
 	ErrNoRequestContext = errors.New("no http request in context")
 )
 
+// http.Request.RemoteAddr is not the originating IP if the request
+// came through a reverse proxy.
+// X-Forwarded-For and X-Real-IP provide this information with decreased
+// support, so check in that order.  There may be multiple 'X-Forwarded-For'
+// headers, but go maps don't retain order so just pick one.
+func RemoteAddr(r *http.Request) string {
+	remoteAddr := r.RemoteAddr
+
+	if prior, ok := r.Header["X-Forwarded-For"]; ok {
+		proxies := strings.Split(prior[0], ",")
+		if len(proxies) > 0 {
+			remoteAddr = strings.Trim(proxies[0], " ")
+		}
+	} else if realip, ok := r.Header["X-Real-Ip"]; ok {
+		if len(realip) > 0 {
+			remoteAddr = realip[0]
+		}
+	}
+
+	return remoteAddr
+}
+
 // WithRequest places the request on the context. The context of the request
 // is assigned a unique id, available at "http.request.id". The request itself
 // is available at "http.request". Other common attributes are available under
 // the prefix "http.request.". If a request is already present on the context,
 // this method will panic.
+
 func WithRequest(ctx context.Context, r *http.Request) context.Context {
 	if ctx.Value("http.request") != nil {
 		// NOTE(stevvooe): This needs to be considered a programming error. It
@@ -147,7 +170,7 @@ func (ctx *httpRequestContext) Value(key interface{}) interface{} {
 		case "uri":
 			return ctx.r.RequestURI
 		case "remoteaddr":
-			return ctx.r.RemoteAddr
+			return RemoteAddr(ctx.r)
 		case "method":
 			return ctx.r.Method
 		case "host":
diff --git a/context/http_test.go b/context/http_test.go
index df3734e8..1fee1761 100644
--- a/context/http_test.go
+++ b/context/http_test.go
@@ -2,6 +2,9 @@ package context
 
 import (
 	"net/http"
+	"net/http/httptest"
+	"net/http/httputil"
+	"net/url"
 	"reflect"
 	"testing"
 	"time"
@@ -205,3 +208,47 @@ func TestWithVars(t *testing.T) {
 		}
 	}
 }
+
+// SingleHostReverseProxy will insert an X-Forwarded-For header, and can be used to test
+// RemoteAddr().  A fake RemoteAddr cannot be set on the HTTP request - it is overwritten
+// at the transport layer to 127.0.0.1:<port> .  However, as the X-Forwarded-For header
+// just contains the IP address, it is different enough for testing.
+func TestRemoteAddr(t *testing.T) {
+	expectedRemote := "127.0.0.1"
+	var actualRemote string
+	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		defer r.Body.Close()
+
+		if r.RemoteAddr == expectedRemote {
+			t.Errorf("Unexpected matching remote addresses")
+		}
+		actualRemote = RemoteAddr(r)
+
+		if expectedRemote != actualRemote {
+			t.Errorf("Mismatching remote hosts: %v != %v", expectedRemote, actualRemote)
+		}
+
+		w.WriteHeader(200)
+	}))
+
+	defer backend.Close()
+	backendURL, err := url.Parse(backend.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	proxy := httputil.NewSingleHostReverseProxy(backendURL)
+	frontend := httptest.NewServer(proxy)
+	defer frontend.Close()
+
+	getReq, err := http.NewRequest("GET", frontend.URL, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = http.DefaultClient.Do(getReq)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+}
diff --git a/notifications/bridge.go b/notifications/bridge.go
index 21d2105d..48a2bd5b 100644
--- a/notifications/bridge.go
+++ b/notifications/bridge.go
@@ -6,6 +6,7 @@ import (
 
 	"code.google.com/p/go-uuid/uuid"
 	"github.com/docker/distribution"
+	"github.com/docker/distribution/context"
 	"github.com/docker/distribution/digest"
 	"github.com/docker/distribution/manifest"
 )
@@ -42,10 +43,11 @@ func NewBridge(ub URLBuilder, source SourceRecord, actor ActorRecord, request Re
 
 // NewRequestRecord builds a RequestRecord for use in NewBridge from an
 // http.Request, associating it with a request id.
+
 func NewRequestRecord(id string, r *http.Request) RequestRecord {
 	return RequestRecord{
 		ID:        id,
-		Addr:      r.RemoteAddr,
+		Addr:      context.RemoteAddr(r),
 		Host:      r.Host,
 		Method:    r.Method,
 		UserAgent: r.UserAgent(),