try to fix ss parser

parser/shadowsocks.go

@@ -15,7 +15,6 @@ func ParseShadowsocks(proxy string) (model.Outbound, error) {
 	if !strings.HasPrefix(proxy, constant.ShadowsocksPrefix) {
 		return model.Outbound{}, &ParseError{Type: ErrInvalidPrefix, Raw: proxy}
 	}
-	needDecode := true
 	if !strings.Contains(proxy, "@") {
 		s := strings.SplitN(proxy, "#", 2)
 		d, err := util.DecodeBase64(strings.TrimPrefix(s[0], "ss://"))
@@ -31,7 +30,6 @@ func ParseShadowsocks(proxy string) (model.Outbound, error) {
 		} else {
 			proxy = "ss://" + d
 		}
-		needDecode = false
 	}
 	link, err := url.Parse(proxy)
 	if err != nil {
@@ -67,37 +65,28 @@ func ParseShadowsocks(proxy string) (model.Outbound, error) {
 		}
 	}
 
-	method := ""
-	password := ""
-	if needDecode {
-		user, err := util.DecodeBase64(link.User.Username())
+	method := link.User.Username()
+	password, _ := link.User.Password()
+
+	if password == "" {
+		user, err := util.DecodeBase64(method)
+		if err == nil {
+			methodAndPass := strings.SplitN(user, ":", 2)
+			if len(methodAndPass) == 2 {
+				method = methodAndPass[0]
+				password = methodAndPass[1]
+			}
+		}
+	}
+	if isLikelyBase64(password) {
+		password, err = util.DecodeBase64(password)
 		if err != nil {
 			return model.Outbound{}, &ParseError{
 				Type:    ErrInvalidStruct,
-				Message: "missing method and password",
+				Message: "password decode error",
 				Raw:     proxy,
 			}
 		}
-		if user == "" {
-			return model.Outbound{}, &ParseError{
-				Type:    ErrInvalidStruct,
-				Message: "missing method and password",
-				Raw:     proxy,
-			}
-		}
-		methodAndPass := strings.SplitN(user, ":", 2)
-		if len(methodAndPass) != 2 {
-			return model.Outbound{}, &ParseError{
-				Type:    ErrInvalidStruct,
-				Message: "missing method and password",
-				Raw:     proxy,
-			}
-		}
-		method = methodAndPass[0]
-		password = methodAndPass[1]
-	} else {
-		method = link.User.Username()
-		password, _ = link.User.Password()
 	}
 
 	query := link.Query()
@@ -136,3 +125,17 @@ func ParseShadowsocks(proxy string) (model.Outbound, error) {
 	}
 	return result, nil
 }
+
+func isLikelyBase64(s string) bool {
+	if len(s)%4 == 0 && strings.HasSuffix(s, "=") && !strings.Contains(strings.TrimSuffix(s, "="), "=") {
+		s = strings.TrimSuffix(s, "=")
+		chars := "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+		for _, c := range s {
+			if !strings.ContainsRune(chars, c) {
+				return false
+			}
+		}
+		return true
+	}
+	return false
+}