Config: Support env XRAY_JSON_STRICT=true (#6053)

https://github.com/XTLS/Xray-core/pull/6053#issuecomment-4363840170

---------

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

infra/conf/serial/loader.go

@@ -42,6 +42,9 @@ func findOffset(b []byte, o int) *offset {
 
 // DecodeJSONConfig reads from reader and decode the config into *conf.Config
 // syntax error could be detected.
+//
+// Permissive: accepts JSON with Java/Python-style comments via json_reader.Reader.
+// Used for local files and stdin where the config is human-edited.
 func DecodeJSONConfig(reader io.Reader) (*conf.Config, error) {
 	jsonConfig := &conf.Config{}
 
@@ -69,6 +72,24 @@ func DecodeJSONConfig(reader io.Reader) (*conf.Config, error) {
 	return jsonConfig, nil
 }
 
+// DecodeJSONConfigStrict reads standard RFC 8259 JSON without comment-stripping.
+// Used for remote sources (http/https/http+unix) where the payload is produced by
+// automated systems and cannot contain JSON5/JSONC extensions. Avoids the
+// byte-by-byte comment stripper and TeeReader, which are significant overhead on
+// large configs.
+func DecodeJSONConfigStrict(reader io.Reader) (*conf.Config, error) {
+    data, err := io.ReadAll(reader)
+    if err != nil {
+        return nil, errors.New("failed to read config file").Base(err)
+    }
+    jsonConfig := &conf.Config{}
+    if err := json.Unmarshal(data, jsonConfig); err != nil {
+        return nil, errors.New("failed to parse remote JSON config").Base(err)
+    }
+    return jsonConfig, nil
+}
+
+
 func LoadJSONConfig(reader io.Reader) (*core.Config, error) {
 	jsonConfig, err := DecodeJSONConfig(reader)
 	if err != nil {