Merge pull request #137 from dirtbags/extract_xforwardedfor_headers

Extract and use X-Forwarded-For headers in mothd logging

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Include basic metadata in mothballs
 - add_script_stream convenience function allows easy script addition to puzzle
 - Autobuild Docker images to test buildability
+- Extract and use X-Forwarded-For headers in mothd logging
 ### Fixed
 - Handle cases where non-legacy puzzles don't have an `author` attribute
 - Handle YAML-formatted file and script lists as expected

src/handlers.go

@@ -339,10 +339,22 @@ func (ctx *Instance) ServeHTTP(wOrig http.ResponseWriter, r *http.Request) {
 		w:          wOrig,
 		statusCode: new(int),
 	}
+
+	clientIP := r.RemoteAddr
+
+	if (ctx.UseXForwarded) {
+		forwardedIP := r.Header.Get("X-Forwarded-For")
+		forwardedIP = strings.Split(forwardedIP, ", ")[0]
+
+		if forwardedIP != "" {
+			clientIP = forwardedIP
+		}
+	}
+
 	ctx.mux.ServeHTTP(w, r)
 	log.Printf(
 		"%s %s %s %d\n",
-		r.RemoteAddr,
+		clientIP,
 		r.Method,
 		r.URL,
 		*w.statusCode,

src/instance.go

@@ -25,6 +25,7 @@ type Instance struct {
 	StateDir        string
 	ThemeDir        string
 	AttemptInterval time.Duration
+	UseXForwarded	bool
 
 	Runtime RuntimeConfig
 

src/mothd.go

@@ -52,6 +52,12 @@ func main() {
 		20*time.Second,
 		"Time between maintenance tasks",
 	)
+	flag.BoolVar(
+		&ctx.UseXForwarded,
+		"x-forwarded-for",
+		false,
+		"Emit IPs from the X-Forwarded-For header in logs, when available, instead of the source IP. Use this when running behind a load-balancer or proxy",
+	)
 	listen := flag.String(
 		"listen",
 		":8080",