refactor: simplify browser dialer UUID path validation

Agent-Logs-Url: https://github.com/XTLS/Xray-core/sessions/9288cc3c-d788-49d9-8bdc-f03281c238bf

Co-authored-by: RPRX <63339210+RPRX@users.noreply.github.com>

transport/internet/browser_dialer/dialer.go

@@ -11,6 +11,7 @@ import (
 	"net/http"
 	"net/url"
 	pathlib "path"
+	"regexp"
 	"strings"
 	"sync"
 	"time"
@@ -35,7 +36,8 @@ var dialerServers map[string]*dialerServer
 var mu sync.RWMutex
 
 const browserDialerSubprotocol = "browser-dialer"
-const uuidPathLength = 37
+
+var uuidPathPattern = regexp.MustCompile(`^/[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$`)
 
 var upgrader = &websocket.Upgrader{
 	ReadBufferSize:   0,
@@ -97,7 +99,7 @@ func parseBrowserDialerAddress(addr string) (*browserDialerAddress, bool) {
 	if cleanPath == "." || cleanPath == "/" || cleanPath != path {
 		return nil, false
 	}
-	if !isUUIDPath(cleanPath) {
+	if !uuidPathPattern.MatchString(cleanPath) {
 		return nil, false
 	}
 
@@ -107,30 +109,6 @@ func parseBrowserDialerAddress(addr string) (*browserDialerAddress, bool) {
 	}, true
 }
 
-func isUUIDPath(path string) bool {
-	if len(path) != uuidPathLength || path[0] != '/' || strings.Count(path, "/") != 1 {
-		return false
-	}
-
-	u := path[1:]
-	for i := 0; i < len(u); i++ {
-		c := u[i]
-		switch i {
-		case 8, 13, 18, 23:
-			if c != '-' {
-				return false
-			}
-		default:
-			isHex := (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F')
-			if !isHex {
-				return false
-			}
-		}
-	}
-
-	return true
-}
-
 func newDialerInstance(path string) *dialerInstance {
 	page := bytes.ReplaceAll(webpage, []byte("dialerPath"), []byte(strings.TrimPrefix(path, "/")))
 	dialer := &dialerInstance{