From 8b463fbc2b8acb500408b62b536dc4aab69cc491 Mon Sep 17 00:00:00 2001
From: eugene <elzeigel@gmail.com>
Date: Tue, 2 Mar 2021 17:08:31 -0500
Subject: [PATCH] lnd: optionally listen on localhost for better security

The --profile flag now accepts both a port and a host:port string.
If profile is set to a port, then pprof debugging information will
be served over localhost. Otherwise, we will attempt to serve pprof
information on the specified host:port (if we are allowed to listen
on it.)

We default to the safe option as if the port is connectable, anybody
can connect and see debugging information.

See: https://mmcloughlin.com/posts/your-pprof-is-showing
---
 config.go | 37 ++++++++++++++++++++++++++++---------
 lnd.go    |  4 ++--
 2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/config.go b/config.go
index 80d81ee6..801d0f8f 100644
--- a/config.go
+++ b/config.go
@@ -239,7 +239,7 @@ type Config struct {
 
 	CPUProfile string `long:"cpuprofile" description:"Write CPU profile to the specified file"`
 
-	Profile string `long:"profile" description:"Enable HTTP profiling on given port -- NOTE port must be between 1024 and 65535"`
+	Profile string `long:"profile" description:"Enable HTTP profiling on either a port or host:port"`
 
 	UnsafeDisconnect   bool   `long:"unsafe-disconnect" description:"DEPRECATED: Allows the rpcserver to intentionally disconnect from peers with open channels. THIS FLAG WILL BE REMOVED IN 0.10.0"`
 	UnsafeReplay       bool   `long:"unsafe-replay" description:"Causes a link to replay the adds on its commitment txn after starting up, this enables testing of the sphinx replay logic."`
@@ -1086,15 +1086,34 @@ func ValidateConfig(cfg Config, usageMessage string,
 		cfg.Autopilot.MaxChannelSize = int64(MaxFundingAmount)
 	}
 
-	// Validate profile port number.
+	// Validate profile port or host:port.
 	if cfg.Profile != "" {
-		profilePort, err := strconv.Atoi(cfg.Profile)
-		if err != nil || profilePort < 1024 || profilePort > 65535 {
-			str := "%s: The profile port must be between 1024 and 65535"
-			err := fmt.Errorf(str, funcName)
-			_, _ = fmt.Fprintln(os.Stderr, err)
-			_, _ = fmt.Fprintln(os.Stderr, usageMessage)
-			return nil, err
+		str := "%s: The profile port must be between 1024 and 65535"
+
+		// Try to parse Profile as a host:port.
+		_, hostPort, err := net.SplitHostPort(cfg.Profile)
+		if err == nil {
+			// Determine if the port is valid.
+			profilePort, err := strconv.Atoi(hostPort)
+			if err != nil || profilePort < 1024 || profilePort > 65535 {
+				err = fmt.Errorf(str, funcName)
+				_, _ = fmt.Fprintln(os.Stderr, err)
+				_, _ = fmt.Fprintln(os.Stderr, usageMessage)
+				return nil, err
+			}
+		} else {
+			// Try to parse Profile as a port.
+			profilePort, err := strconv.Atoi(cfg.Profile)
+			if err != nil || profilePort < 1024 || profilePort > 65535 {
+				err = fmt.Errorf(str, funcName)
+				_, _ = fmt.Fprintln(os.Stderr, err)
+				_, _ = fmt.Fprintln(os.Stderr, usageMessage)
+				return nil, err
+			}
+
+			// Since the user just set a port, we will serve debugging
+			// information over localhost.
+			cfg.Profile = net.JoinHostPort("127.0.0.1", cfg.Profile)
 		}
 	}
 
diff --git a/lnd.go b/lnd.go
index e340a2fd..2b614d8d 100644
--- a/lnd.go
+++ b/lnd.go
@@ -227,11 +227,11 @@ func Main(cfg *Config, lisCfg ListenerCfg, interceptor signal.Interceptor) error
 	// Enable http profiling server if requested.
 	if cfg.Profile != "" {
 		go func() {
-			listenAddr := net.JoinHostPort("", cfg.Profile)
 			profileRedirect := http.RedirectHandler("/debug/pprof",
 				http.StatusSeeOther)
 			http.Handle("/", profileRedirect)
-			fmt.Println(http.ListenAndServe(listenAddr, nil))
+			ltndLog.Infof("Pprof listening on %v", cfg.Profile)
+			fmt.Println(http.ListenAndServe(cfg.Profile, nil))
 		}()
 	}