Deprecate legacy VMess header with a planned decommission (#712)

* Deprecate legacy VMess header with a planned decommission
* show legacy warning only once

Co-authored-by: Xiaokang Wang <xiaokangwang@outlook.com>
Co-authored-by: hmol233 <82594500+hmol233@users.noreply.github.com>

proxy/vmess/encoding/server.go

@@ -191,11 +191,17 @@ func (s *ServerSession) DecodeRequestHeader(reader io.Reader, isDrain bool) (*pr
 		decryptor = bytes.NewReader(aeadData)
 		s.isAEADRequest = true
 
-	case !s.isAEADForced && errorAEAD == vmessaead.ErrNotFound:
+	case errorAEAD == vmessaead.ErrNotFound:
 		userLegacy, timestamp, valid, userValidationError := s.userValidator.Get(buffer.Bytes())
 		if !valid || userValidationError != nil {
 			return nil, drainConnection(newError("invalid user").Base(userValidationError))
 		}
+		if s.isAEADForced {
+			return nil, drainConnection(newError("invalid user: VMessAEAD is enforced and a non VMessAEAD connection is received. You can still disable this security feature with environment variable xray.vmess.aead.forced = false . You will not be able to enable legacy header workaround in the future."))
+		}
+		if s.userValidator.ShouldShowLegacyWarn() {
+			newError("Critical Warning: potentially invalid user: a non VMessAEAD connection is received. From 2022 Jan 1st, this kind of connection will be rejected by default. You should update or replace your client software now. This message will not be shown for further violation on this inbound.").AtWarning().WriteToLog()
+		}
 		user = userLegacy
 		iv := hashTimestamp(md5.New(), timestamp)
 		vmessAccount = userLegacy.Account.(*vmess.MemoryAccount)

proxy/vmess/inbound/inbound.go

@@ -31,6 +31,7 @@ import (
 
 var (
 	aeadForced = false
+	aeadForced2022 = false
 )
 
 type userByEmail struct {
@@ -368,8 +369,17 @@ func init() {
 		return New(ctx, config.(*Config))
 	}))
 
-	const defaultFlagValue = "NOT_DEFINED_AT_ALL"
+	var defaultFlagValue = "NOT_DEFINED_AT_ALL"
+
+	if time.Now().Year() >= 2022 {
+		defaultFlagValue = "true_by_default_2022"
+	}
 
 	isAeadForced := platform.NewEnvFlag("xray.vmess.aead.forced").GetValue(func() string { return defaultFlagValue })
 	aeadForced = (isAeadForced == "true")
+
+	if isAeadForced == "true_by_default_2022" {
+		aeadForced = true
+		aeadForced2022 = true
+	}
 }

proxy/vmess/validator.go

@@ -40,6 +40,8 @@ type TimedUserValidator struct {
 	behaviorFused bool
 
 	aeadDecoderHolder *aead.AuthIDDecoderHolder
+
+	legacyWarnShown bool
 }
 
 type indexTimePair struct {
@@ -245,6 +247,17 @@ func (v *TimedUserValidator) BurnTaintFuse(userHash []byte) error {
 	return ErrNotFound
 }
 
+/* ShouldShowLegacyWarn will return whether a Legacy Warning should be shown
+Not guaranteed to only return true once for every inbound, but it is okay.
+*/
+func (v *TimedUserValidator) ShouldShowLegacyWarn() bool {
+	if v.legacyWarnShown {
+		return false
+	}
+	v.legacyWarnShown = true
+	return true
+}
+
 var ErrNotFound = newError("Not Found")
 
 var ErrTainted = newError("ErrTainted")