Pull request: home: add a patch against the global pprof handlers

Merge in DNS/adguard-home from 2336-pprof to master

Closes #2336.

Squashed commit of the following:

commit 855e133b17da4274bef7dec5c3b7db73486d97db
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu Nov 19 14:49:22 2020 +0300

    home: add a patch against the global pprof handlers

internal/home/web.go

@@ -7,6 +7,7 @@ import (
 	"net"
 	"net/http"
 	"strconv"
+	"strings"
 	"sync"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/util"
@@ -141,6 +142,7 @@ func (web *Web) Start() {
 		web.httpServer = &http.Server{
 			ErrorLog: web.errLogger,
 			Addr:     address,
+			Handler:  filterPPROF(http.DefaultServeMux),
 		}
 		err := web.httpServer.ListenAndServe()
 		if err != http.ErrServerClosed {
@@ -151,6 +153,22 @@ func (web *Web) Start() {
 	}
 }
 
+// TODO(a.garipov): We currently have to use this, because everything registers
+// its HTTP handlers in http.DefaultServeMux.  In the future, refactor our HTTP
+// API initialization process and stop using the gosh darn http.DefaultServeMux
+// for anything at all.  Gosh darn global variables.
+func filterPPROF(h http.Handler) (filtered http.Handler) {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if strings.HasPrefix(r.URL.Path, "/debug/pprof") {
+			http.NotFound(w, r)
+
+			return
+		}
+
+		h.ServeHTTP(w, r)
+	})
+}
+
 // Close - stop HTTP server, possibly waiting for all active connections to be closed
 func (web *Web) Close() {
 	log.Info("Stopping HTTP server...")