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>

common/platform/platform.go

@@ -17,6 +17,7 @@ const (
 	UseFreedomSplice = "xray.buf.splice"
 	UseVmessPadding  = "xray.vmess.padding"
 	UseCone          = "xray.cone.disabled"
+	UseStrictJSON    = "xray.json.strict"
 
 	BufferSize           = "xray.ray.buffer.size"
 	BrowserDialerAddress = "xray.browser.dialer"

infra/conf/serial/builder.go

@@ -5,12 +5,22 @@ import (
 	"io"
 
 	"github.com/xtls/xray-core/common/errors"
+	"github.com/xtls/xray-core/common/platform"
 	creflect "github.com/xtls/xray-core/common/reflect"
 	"github.com/xtls/xray-core/core"
 	"github.com/xtls/xray-core/infra/conf"
 	"github.com/xtls/xray-core/main/confloader"
 )
 
+// UseStrictJSON, when true, makes JSON config decoders skip the custom
+// comment-stripping reader and parse input as strict RFC 8259 JSON.
+//
+// Enabled by setting the env variable xray.json.strict=true (or its normalized
+// form XRAY_JSON_STRICT=true). Default false preserves backward-compatible
+// behavior for human-edited configs that may contain comments or other
+// JSON5/JSONC syntax.
+var UseStrictJSON = platform.NewEnvFlag(platform.UseStrictJSON).GetValue(func() string { return "" }) == "true"
+
 func MergeConfigFromFiles(files []*core.ConfigSource) (string, error) {
 	c, err := mergeConfigs(files)
 	if err != nil {
@@ -31,7 +41,11 @@ func mergeConfigs(files []*core.ConfigSource) (*conf.Config, error) {
 		if err != nil {
 			return nil, errors.New("failed to read config: ", file).Base(err)
 		}
-		c, err := ReaderDecoderByFormat[file.Format](r)
+		decoder := ReaderDecoderByFormat[file.Format]
+		if file.Format == "json" && UseStrictJSON {
+			decoder = DecodeJSONConfigStrict
+		}
+		c, err := decoder(r)
 		if err != nil {
 			return nil, errors.New("failed to decode config: ", file).Base(err)
 		}

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 {

main/json/json.go

@@ -41,6 +41,13 @@ func init() {
 				}
 				return cf.Build()
 			case io.Reader:
+				if serial.UseStrictJSON {
+					cfg, err := serial.DecodeJSONConfigStrict(v)
+					if err != nil {
+						return nil, err
+					}
+					return cfg.Build()
+				}
 				return serial.LoadJSONConfig(v)
 			default:
 				return nil, errors.New("unknown type")