XMC finalmask: Add default directional padding/keep-alive packets, matching Minecraft 26.1.2 login/join/etc traffic shapes (#6487)

https://github.com/XTLS/Xray-core/pull/6487#issuecomment-5092235757

---------

Co-authored-by: 风扇滑翔翼 <Fangliding.fshxy@outlook.com>

infra/conf/transport_finalmask.go

@@ -11,6 +11,7 @@ import (
 	"regexp"
 	"strings"
 
+	googleuuid "github.com/google/uuid"
 	"github.com/xtls/xray-core/common/errors"
 	"github.com/xtls/xray-core/common/net"
 	"github.com/xtls/xray-core/transport/internet/finalmask/fragment"
@@ -720,14 +721,46 @@ func (c *Xdns) Build() (proto.Message, error) {
 }
 
 type XMC struct {
-	Hostname  string   `json:"hostname"`
-	Usernames []string `json:"usernames"`
-	Password  string   `json:"password"`
+	Hostname string       `json:"hostname"`
+	Profiles []XMCProfile `json:"profiles"`
+	Password string       `json:"password"`
+}
+
+type XMCProfile struct {
+	// Resolve the UUID by username, then request the session profile with
+	// unsigned=false. Client and server must use the same signed profile.
+	Username          string `json:"username"`
+	UUID              string `json:"uuid"`
+	TexturesValue     string `json:"texturesValue"`
+	TexturesSignature string `json:"texturesSignature"`
+}
+
+var xmcUsernamePattern = regexp.MustCompile(`^[A-Za-z0-9_]{3,16}$`)
+
+func (c *XMCProfile) Build() (*xmc.Profile, error) {
+	if !xmcUsernamePattern.MatchString(c.Username) {
+		return nil, fmt.Errorf("invalid minecraft profile username: %q", c.Username)
+	}
+
+	profileUUID, err := googleuuid.Parse(c.UUID)
+	if err != nil {
+		return nil, fmt.Errorf("invalid minecraft profile UUID: %w", err)
+	}
+	if c.TexturesValue == "" || c.TexturesSignature == "" {
+		return nil, fmt.Errorf("incomplete minecraft profile textures")
+	}
+
+	return &xmc.Profile{
+		Username:          c.Username,
+		Uuid:              append([]byte(nil), profileUUID[:]...),
+		TexturesValue:     c.TexturesValue,
+		TexturesSignature: c.TexturesSignature,
+	}, nil
 }
 
 func (c *XMC) Build() (proto.Message, error) {
-	if len(c.Usernames) == 0 {
-		c.Usernames = []string{"Dream"}
+	if len(c.Profiles) == 0 {
+		return nil, fmt.Errorf("minecraft profiles are required")
 	}
 
 	if c.Password == "" {
@@ -744,12 +777,21 @@ func (c *XMC) Build() (proto.Message, error) {
 		return nil, fmt.Errorf("marshal minecraft rsa public key: %w", err)
 	}
 
+	profiles := make([]*xmc.Profile, 0, len(c.Profiles))
+	for i := range c.Profiles {
+		profile, err := c.Profiles[i].Build()
+		if err != nil {
+			return nil, fmt.Errorf("build minecraft profile %d: %w", i, err)
+		}
+		profiles = append(profiles, profile)
+	}
+
 	return &xmc.Config{
 		Password:      c.Password,
-		Usernames:     c.Usernames,
 		Hostname:      c.Hostname,
 		RsaPrivateKey: x509.MarshalPKCS1PrivateKey(rsaPrivateKey),
 		RsaPublicKey:  rsaPublicKey,
+		Profiles:      profiles,
 	}, nil
 }
 

infra/conf/transport_finalmask_xmc_test.go

@@ -0,0 +1,36 @@
+package conf
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/xtls/xray-core/transport/internet/finalmask/xmc"
+)
+
+func TestXMCBuildProfile(t *testing.T) {
+	built, err := (&XMC{
+		Password: "test-password",
+		Profiles: []XMCProfile{
+			{
+				Username:          "TestUser",
+				UUID:              "00112233-4455-6677-8899-aabbccddeeff",
+				TexturesValue:     "textures-value",
+				TexturesSignature: "textures-signature",
+			},
+		},
+	}).Build()
+	if err != nil {
+		t.Fatalf("build XMC config: %v", err)
+	}
+	config := built.(*xmc.Config)
+	if len(config.Profiles) != 1 || len(config.Profiles[0].Uuid) != 16 {
+		t.Fatalf("unexpected profiles: %+v", config.Profiles)
+	}
+}
+
+func TestXMCBuildRequiresProfile(t *testing.T) {
+	_, err := (&XMC{Password: "test-password"}).Build()
+	if err == nil || !strings.Contains(err.Error(), "profiles are required") {
+		t.Fatalf("expected required profiles error, got %v", err)
+	}
+}