Xray-core v26.7.28

Sponsor & Donation & NFTs: https://github.com/XTLS/Xray-core/issues/3668
Project X Channel: https://t.me/projectXtls

Announcement of NFTs by Project X: https://github.com/XTLS/Xray-core/discussions/3633
Project X NFT: https://opensea.io/assets/ethereum/0x5ee362866001613093361eb8569d59c4141b76d1/1

VLESS Post-Quantum Encryption: https://github.com/XTLS/Xray-core/pull/5067
VLESS NFT: https://opensea.io/collection/vless

XHTTP: Beyond REALITY: https://github.com/XTLS/Xray-core/discussions/4113
REALITY NFT: https://opensea.io/assets/ethereum/0x5ee362866001613093361eb8569d59c4141b76d1/2

common/net/find_process_darwin.go

@@ -1,4 +1,4 @@
-//go:build darwin
+//go:build darwin && !ios
 
 package net
 

common/net/find_process_darwin.s

@@ -1,4 +1,4 @@
-//go:build darwin
+//go:build darwin && !ios
 
 #include "textflag.h"
 

common/net/find_process_darwin_test.go

@@ -1,4 +1,4 @@
-//go:build darwin
+//go:build darwin && !ios
 
 package net
 

common/net/find_process_ios.go

@@ -0,0 +1,11 @@
+//go:build ios
+
+package net
+
+import (
+	"github.com/xtls/xray-core/common/errors"
+)
+
+func FindProcess(network, srcIP string, srcPort uint16, destIP string, destPort uint16) (int, string, string, error) {
+	return 0, "", "", errors.New("process lookup is not supported on this platform")
+}

core/core.go

@@ -20,7 +20,7 @@ import (
 var (
 	Version_x byte = 26
 	Version_y byte = 7
-	Version_z byte = 11
+	Version_z byte = 28
 )
 
 var (

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)
+	}
+}

infra/conf/transport_method.go

@@ -450,8 +450,8 @@ func (c *SplitHTTPConfig) Build() (proto.Message, error) {
 		return nil, errors.New("maxConnections cannot be specified together with maxConcurrency")
 	}
 	if c.Xmux == (XmuxConfig{}) {
-		c.Xmux.MaxConnections.From = 6
-		c.Xmux.MaxConnections.To = 6
+		c.Xmux.MaxConnections.From = 3
+		c.Xmux.MaxConnections.To = 3
 		c.Xmux.HMaxRequestTimes.From = 600
 		c.Xmux.HMaxRequestTimes.To = 900
 		c.Xmux.HMaxReusableSecs.From = 1800

transport/internet/finalmask/xmc/client.go

@@ -5,7 +5,6 @@ import (
 	"bytes"
 	"crypto/rand"
 	"crypto/rsa"
-	"crypto/sha256"
 	"crypto/x509"
 	"fmt"
 	"io"
@@ -23,11 +22,16 @@ type clientConn struct {
 
 	state clientState
 
-	handshakeLock sync.Mutex
-	usernames     []string
-	password      string
-	rsaPublicKey  []byte
-	hostname      string
+	handshakeLock   sync.Mutex
+	lifecycleMu     sync.Mutex
+	closed          bool
+	profiles        []loginProfile
+	password        string
+	rsaPublicKey    []byte
+	hostname        string
+	paddingSchedule []paddingTurn
+	packet          *packetStream
+	deadlines       *connectionDeadlines
 }
 
 type clientState int
@@ -37,21 +41,29 @@ var (
 	clientStateProxy     clientState = 2
 )
 
-func newClientConn(c net.Conn, usernames []string, password string, rsaPublicKey []byte, hostname string) (*clientConn, error) {
+func newClientConn(c net.Conn, profiles []loginProfile, password string, rsaPublicKey []byte, hostname string) (*clientConn, error) {
 	if len(rsaPublicKey) == 0 {
 		return nil, fmt.Errorf("empty rsa public key")
 	}
-
+	if len(profiles) == 0 {
+		return nil, fmt.Errorf("empty profiles")
+	}
+	paddingSchedule, err := newClientPaddingSchedule2612()
+	if err != nil {
+		return nil, fmt.Errorf("select padding profile: %w", err)
+	}
 	return &clientConn{
-		reader:        bufio.NewReader(c),
-		writer:        c,
-		c:             c,
-		state:         clientStateHandshake,
-		handshakeLock: sync.Mutex{},
-		usernames:     usernames,
-		password:      password,
-		rsaPublicKey:  rsaPublicKey,
-		hostname:      hostname,
+		reader:          bufio.NewReader(c),
+		writer:          c,
+		c:               c,
+		state:           clientStateHandshake,
+		handshakeLock:   sync.Mutex{},
+		profiles:        profiles,
+		password:        password,
+		rsaPublicKey:    rsaPublicKey,
+		hostname:        hostname,
+		paddingSchedule: paddingSchedule,
+		deadlines:       newConnectionDeadlines(c),
 	}, nil
 }
 
@@ -63,12 +75,10 @@ func (c *clientConn) handshake() error {
 		return nil
 	}
 
-	// Handshake timeout
-	err := c.c.SetDeadline(time.Now().Add(time.Second * 30))
-	if err != nil {
+	if err := c.deadlines.beginHandshake(); err != nil {
 		return fmt.Errorf("set deadline: %w", err)
 	}
-	defer c.c.SetDeadline(time.Time{})
+	defer func() { _ = c.deadlines.endHandshake() }()
 
 	var (
 		protocolVersion Varint        = Varint(775)
@@ -95,16 +105,14 @@ func (c *clientConn) handshake() error {
 	}
 
 	// Login Start
-	var (
-		username    string
-		offlineUUID UUID
-	)
+	randomProfile, err := rand.Int(rand.Reader, big.NewInt(int64(len(c.profiles))))
+	if err != nil {
+		return fmt.Errorf("select profile: %w", err)
+	}
+	selectedProfile := c.profiles[randomProfile.Int64()]
+	username := String(selectedProfile.Username)
 
-	randomUsername, _ := rand.Int(rand.Reader, big.NewInt(int64(len(c.usernames))))
-	username = c.usernames[randomUsername.Int64()]
-	generateOfflineUUID(&offlineUUID, string(username))
-
-	err = writePacket(c.writer, 0x00, new(String(username)), &offlineUUID)
+	err = writePacket(c.writer, 0x00, &username, &selectedProfile.UUID)
 	if err != nil {
 		return fmt.Errorf("write login start: %w", err)
 	}
@@ -145,7 +153,9 @@ func (c *clientConn) handshake() error {
 	}
 
 	sharedSecret := make([]byte, 16)
-	rand.Read(sharedSecret)
+	if _, err = rand.Read(sharedSecret); err != nil {
+		return fmt.Errorf("generate shared secret: %w", err)
+	}
 
 	encryptedSharedSecret, err := rsa.EncryptPKCS1v15(rand.Reader, rsaPublicKey, sharedSecret)
 	if err != nil {
@@ -181,7 +191,48 @@ func (c *clientConn) handshake() error {
 		return fmt.Errorf("new crypto writer: %w", err)
 	}
 
+	pkt, err = readPacket(c.reader)
+	if err != nil {
+		return fmt.Errorf("read login finished: %w", err)
+	}
+	if pkt.packetID == 0x00 {
+		var reason String
+		if readErr := pkt.readFields(&reason); readErr != nil {
+			return fmt.Errorf("authentication rejected")
+		}
+		return fmt.Errorf("authentication rejected: %s", reason)
+	}
+	if pkt.packetID != 0x02 {
+		return fmt.Errorf("bad login finished packet id: %d", pkt.packetID)
+	}
+
+	receivedProfile, err := readLoginSuccess(pkt)
+	if err != nil {
+		return fmt.Errorf("read login finished fields: %w", err)
+	}
+	if receivedProfile != selectedProfile {
+		return fmt.Errorf("login profile mismatch")
+	}
+	loginAcknowledgedLength, err := writePacketWithLength(c.writer, 0x03)
+	if err != nil {
+		return fmt.Errorf("write login acknowledged: %w", err)
+	}
+	if err = runPaddingSchedule(c.reader, c.writer, true, loginAcknowledgedLength, c.paddingSchedule); err != nil {
+		return fmt.Errorf("run startup padding: %w", err)
+	}
+
+	packet := newPacketStream(c.reader, c.writer, true)
+	c.lifecycleMu.Lock()
+	if c.closed {
+		c.lifecycleMu.Unlock()
+		packet.Stop()
+		return net.ErrClosed
+	}
+	c.packet = packet
+	c.reader = packet
+	c.writer = packet
 	c.state = clientStateProxy
+	c.lifecycleMu.Unlock()
 
 	return nil
 }
@@ -205,6 +256,13 @@ func (c *clientConn) Write(b []byte) (int, error) {
 }
 
 func (c *clientConn) Close() error {
+	c.lifecycleMu.Lock()
+	c.closed = true
+	packet := c.packet
+	c.lifecycleMu.Unlock()
+	if packet != nil {
+		packet.Stop()
+	}
 	return c.c.Close()
 }
 
@@ -217,20 +275,13 @@ func (c *clientConn) RemoteAddr() net.Addr {
 }
 
 func (c *clientConn) SetDeadline(t time.Time) error {
-	return c.c.SetDeadline(t)
+	return c.deadlines.setDeadline(t)
 }
 
 func (c *clientConn) SetReadDeadline(t time.Time) error {
-	return c.c.SetReadDeadline(t)
+	return c.deadlines.setReadDeadline(t)
 }
 
 func (c *clientConn) SetWriteDeadline(t time.Time) error {
-	return c.c.SetWriteDeadline(t)
-}
-
-func generateOfflineUUID(uuid *UUID, username string) {
-	h := sha256.Sum256([]byte("OfflinePlayer:" + username))
-	copy(uuid[:], h[:16])
-	uuid[6] = (uuid[6] & 0x0f) | 0x30 // UUID version 3
-	uuid[8] = (uuid[8] & 0x3f) | 0x80 // UUID variant
+	return c.deadlines.setWriteDeadline(t)
 }

transport/internet/finalmask/xmc/config.go

@@ -9,7 +9,11 @@ func (c *Config) TCP() {
 }
 
 func (c *Config) WrapConnClient(conn net.Conn) (net.Conn, error) {
-	cc, err := newClientConn(conn, c.Usernames, c.Password, c.RsaPublicKey, c.Hostname)
+	profiles, err := profilesFromConfig(c.Profiles)
+	if err != nil {
+		return nil, fmt.Errorf("minecraft finalmask: %w", err)
+	}
+	cc, err := newClientConn(conn, profiles, c.Password, c.RsaPublicKey, c.Hostname)
 	if err != nil {
 		return nil, fmt.Errorf("minecraft finalmask: %w", err)
 	}
@@ -18,7 +22,11 @@ func (c *Config) WrapConnClient(conn net.Conn) (net.Conn, error) {
 }
 
 func (c *Config) WrapConnServer(conn net.Conn) (net.Conn, error) {
-	cc, err := wrapConnServer(conn, c.Password, c.RsaPrivateKey, c.RsaPublicKey)
+	profiles, err := profilesFromConfig(c.Profiles)
+	if err != nil {
+		return nil, fmt.Errorf("minecraft finalmask: %w", err)
+	}
+	cc, err := wrapConnServer(conn, profiles, c.Password, c.RsaPrivateKey, c.RsaPublicKey)
 	if err != nil {
 		return nil, fmt.Errorf("minecraft finalmask: %w", err)
 	}

transport/internet/finalmask/xmc/config.pb.go

@@ -21,20 +21,91 @@ const (
 	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
 )
 
+type Profile struct {
+	state protoimpl.MessageState `protogen:"open.v1"`
+	// Resolve the UUID from https://api.mojang.com/users/profiles/minecraft/{username}.
+	Username string `protobuf:"bytes,1,opt,name=username,proto3" json:"username,omitempty"`
+	Uuid     []byte `protobuf:"bytes,2,opt,name=uuid,proto3" json:"uuid,omitempty"`
+	// Copy the signed textures property returned by
+	// https://sessionserver.mojang.com/session/minecraft/profile/{uuid}?unsigned=false.
+	TexturesValue     string `protobuf:"bytes,3,opt,name=textures_value,json=texturesValue,proto3" json:"textures_value,omitempty"`
+	TexturesSignature string `protobuf:"bytes,4,opt,name=textures_signature,json=texturesSignature,proto3" json:"textures_signature,omitempty"`
+	unknownFields     protoimpl.UnknownFields
+	sizeCache         protoimpl.SizeCache
+}
+
+func (x *Profile) Reset() {
+	*x = Profile{}
+	mi := &file_transport_internet_finalmask_xmc_config_proto_msgTypes[0]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *Profile) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*Profile) ProtoMessage() {}
+
+func (x *Profile) ProtoReflect() protoreflect.Message {
+	mi := &file_transport_internet_finalmask_xmc_config_proto_msgTypes[0]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use Profile.ProtoReflect.Descriptor instead.
+func (*Profile) Descriptor() ([]byte, []int) {
+	return file_transport_internet_finalmask_xmc_config_proto_rawDescGZIP(), []int{0}
+}
+
+func (x *Profile) GetUsername() string {
+	if x != nil {
+		return x.Username
+	}
+	return ""
+}
+
+func (x *Profile) GetUuid() []byte {
+	if x != nil {
+		return x.Uuid
+	}
+	return nil
+}
+
+func (x *Profile) GetTexturesValue() string {
+	if x != nil {
+		return x.TexturesValue
+	}
+	return ""
+}
+
+func (x *Profile) GetTexturesSignature() string {
+	if x != nil {
+		return x.TexturesSignature
+	}
+	return ""
+}
+
 type Config struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
 	Password      string                 `protobuf:"bytes,1,opt,name=password,proto3" json:"password,omitempty"`
-	Usernames     []string               `protobuf:"bytes,2,rep,name=usernames,proto3" json:"usernames,omitempty"`
 	RsaPrivateKey []byte                 `protobuf:"bytes,8,opt,name=rsa_private_key,json=rsaPrivateKey,proto3" json:"rsa_private_key,omitempty"`
 	RsaPublicKey  []byte                 `protobuf:"bytes,9,opt,name=rsa_public_key,json=rsaPublicKey,proto3" json:"rsa_public_key,omitempty"`
 	Hostname      string                 `protobuf:"bytes,10,opt,name=hostname,proto3" json:"hostname,omitempty"`
+	Profiles      []*Profile             `protobuf:"bytes,11,rep,name=profiles,proto3" json:"profiles,omitempty"`
 	unknownFields protoimpl.UnknownFields
 	sizeCache     protoimpl.SizeCache
 }
 
 func (x *Config) Reset() {
 	*x = Config{}
-	mi := &file_transport_internet_finalmask_xmc_config_proto_msgTypes[0]
+	mi := &file_transport_internet_finalmask_xmc_config_proto_msgTypes[1]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -46,7 +117,7 @@ func (x *Config) String() string {
 func (*Config) ProtoMessage() {}
 
 func (x *Config) ProtoReflect() protoreflect.Message {
-	mi := &file_transport_internet_finalmask_xmc_config_proto_msgTypes[0]
+	mi := &file_transport_internet_finalmask_xmc_config_proto_msgTypes[1]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -59,7 +130,7 @@ func (x *Config) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use Config.ProtoReflect.Descriptor instead.
 func (*Config) Descriptor() ([]byte, []int) {
-	return file_transport_internet_finalmask_xmc_config_proto_rawDescGZIP(), []int{0}
+	return file_transport_internet_finalmask_xmc_config_proto_rawDescGZIP(), []int{1}
 }
 
 func (x *Config) GetPassword() string {
@@ -69,13 +140,6 @@ func (x *Config) GetPassword() string {
 	return ""
 }
 
-func (x *Config) GetUsernames() []string {
-	if x != nil {
-		return x.Usernames
-	}
-	return nil
-}
-
 func (x *Config) GetRsaPrivateKey() []byte {
 	if x != nil {
 		return x.RsaPrivateKey
@@ -97,18 +161,30 @@ func (x *Config) GetHostname() string {
 	return ""
 }
 
+func (x *Config) GetProfiles() []*Profile {
+	if x != nil {
+		return x.Profiles
+	}
+	return nil
+}
+
 var File_transport_internet_finalmask_xmc_config_proto protoreflect.FileDescriptor
 
 const file_transport_internet_finalmask_xmc_config_proto_rawDesc = "" +
 	"\n" +
-	"-transport/internet/finalmask/xmc/config.proto\x12%xray.transport.internet.finalmask.xmc\"\xac\x01\n" +
+	"-transport/internet/finalmask/xmc/config.proto\x12%xray.transport.internet.finalmask.xmc\"\x8f\x01\n" +
+	"\aProfile\x12\x1a\n" +
+	"\busername\x18\x01 \x01(\tR\busername\x12\x12\n" +
+	"\x04uuid\x18\x02 \x01(\fR\x04uuid\x12%\n" +
+	"\x0etextures_value\x18\x03 \x01(\tR\rtexturesValue\x12-\n" +
+	"\x12textures_signature\x18\x04 \x01(\tR\x11texturesSignature\"\xe0\x01\n" +
 	"\x06Config\x12\x1a\n" +
-	"\bpassword\x18\x01 \x01(\tR\bpassword\x12\x1c\n" +
-	"\tusernames\x18\x02 \x03(\tR\tusernames\x12&\n" +
+	"\bpassword\x18\x01 \x01(\tR\bpassword\x12&\n" +
 	"\x0frsa_private_key\x18\b \x01(\fR\rrsaPrivateKey\x12$\n" +
 	"\x0ersa_public_key\x18\t \x01(\fR\frsaPublicKey\x12\x1a\n" +
 	"\bhostname\x18\n" +
-	" \x01(\tR\bhostnameB\x91\x01\n" +
+	" \x01(\tR\bhostname\x12J\n" +
+	"\bprofiles\x18\v \x03(\v2..xray.transport.internet.finalmask.xmc.ProfileR\bprofilesJ\x04\b\x02\x10\x03B\x91\x01\n" +
 	")com.xray.transport.internet.finalmask.xmcP\x01Z:github.com/xtls/xray-core/transport/internet/finalmask/xmc\xaa\x02%Xray.Transport.Internet.Finalmask.XMCb\x06proto3"
 
 var (
@@ -123,16 +199,18 @@ func file_transport_internet_finalmask_xmc_config_proto_rawDescGZIP() []byte {
 	return file_transport_internet_finalmask_xmc_config_proto_rawDescData
 }
 
-var file_transport_internet_finalmask_xmc_config_proto_msgTypes = make([]protoimpl.MessageInfo, 1)
+var file_transport_internet_finalmask_xmc_config_proto_msgTypes = make([]protoimpl.MessageInfo, 2)
 var file_transport_internet_finalmask_xmc_config_proto_goTypes = []any{
-	(*Config)(nil), // 0: xray.transport.internet.finalmask.xmc.Config
+	(*Profile)(nil), // 0: xray.transport.internet.finalmask.xmc.Profile
+	(*Config)(nil),  // 1: xray.transport.internet.finalmask.xmc.Config
 }
 var file_transport_internet_finalmask_xmc_config_proto_depIdxs = []int32{
-	0, // [0:0] is the sub-list for method output_type
-	0, // [0:0] is the sub-list for method input_type
-	0, // [0:0] is the sub-list for extension type_name
-	0, // [0:0] is the sub-list for extension extendee
-	0, // [0:0] is the sub-list for field type_name
+	0, // 0: xray.transport.internet.finalmask.xmc.Config.profiles:type_name -> xray.transport.internet.finalmask.xmc.Profile
+	1, // [1:1] is the sub-list for method output_type
+	1, // [1:1] is the sub-list for method input_type
+	1, // [1:1] is the sub-list for extension type_name
+	1, // [1:1] is the sub-list for extension extendee
+	0, // [0:1] is the sub-list for field type_name
 }
 
 func init() { file_transport_internet_finalmask_xmc_config_proto_init() }
@@ -146,7 +224,7 @@ func file_transport_internet_finalmask_xmc_config_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: unsafe.Slice(unsafe.StringData(file_transport_internet_finalmask_xmc_config_proto_rawDesc), len(file_transport_internet_finalmask_xmc_config_proto_rawDesc)),
 			NumEnums:      0,
-			NumMessages:   1,
+			NumMessages:   2,
 			NumExtensions: 0,
 			NumServices:   0,
 		},

transport/internet/finalmask/xmc/config.proto

@@ -6,11 +6,21 @@ option go_package = "github.com/xtls/xray-core/transport/internet/finalmask/xmc"
 option java_package = "com.xray.transport.internet.finalmask.xmc";
 option java_multiple_files = true;
 
+message Profile {
+    // Resolve the UUID from https://api.mojang.com/users/profiles/minecraft/{username}.
+    string username = 1;
+    bytes uuid = 2;
+    // Copy the signed textures property returned by
+    // https://sessionserver.mojang.com/session/minecraft/profile/{uuid}?unsigned=false.
+    string textures_value = 3;
+    string textures_signature = 4;
+}
 
 message Config {
     string password = 1;
-    repeated string usernames = 2;
+    reserved 2;
     bytes rsa_private_key = 8;
     bytes rsa_public_key = 9;
     string hostname = 10;
+    repeated Profile profiles = 11;
 }

transport/internet/finalmask/xmc/deadline.go

@@ -0,0 +1,85 @@
+package xmc
+
+import (
+	"net"
+	"sync"
+	"time"
+)
+
+const handshakeTimeout = 2 * time.Minute
+
+type connectionDeadlines struct {
+	mu sync.Mutex
+	c  net.Conn
+
+	read      time.Time
+	write     time.Time
+	handshake time.Time
+}
+
+func newConnectionDeadlines(c net.Conn) *connectionDeadlines {
+	return &connectionDeadlines{c: c}
+}
+
+func (d *connectionDeadlines) beginHandshake() error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	d.handshake = time.Now().Add(handshakeTimeout)
+	if err := d.applyLocked(); err != nil {
+		d.handshake = time.Time{}
+		_ = d.applyLocked()
+		return err
+	}
+	return nil
+}
+
+func (d *connectionDeadlines) endHandshake() error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	d.handshake = time.Time{}
+	return d.applyLocked()
+}
+
+func (d *connectionDeadlines) setDeadline(t time.Time) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	d.read = t
+	d.write = t
+	return d.applyLocked()
+}
+
+func (d *connectionDeadlines) setReadDeadline(t time.Time) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	d.read = t
+	return d.c.SetReadDeadline(earlierDeadline(d.read, d.handshake))
+}
+
+func (d *connectionDeadlines) setWriteDeadline(t time.Time) error {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	d.write = t
+	return d.c.SetWriteDeadline(earlierDeadline(d.write, d.handshake))
+}
+
+func (d *connectionDeadlines) applyLocked() error {
+	if err := d.c.SetReadDeadline(earlierDeadline(d.read, d.handshake)); err != nil {
+		return err
+	}
+	return d.c.SetWriteDeadline(earlierDeadline(d.write, d.handshake))
+}
+
+func earlierDeadline(user, internal time.Time) time.Time {
+	if internal.IsZero() {
+		return user
+	}
+	if user.IsZero() || internal.Before(user) {
+		return internal
+	}
+	return user
+}

transport/internet/finalmask/xmc/deadline_test.go

@@ -0,0 +1,81 @@
+package xmc
+
+import (
+	"net"
+	"sync"
+	"testing"
+	"time"
+)
+
+func TestConnectionDeadlinesRestoreCallerValues(t *testing.T) {
+	client, server := net.Pipe()
+	defer client.Close()
+	defer server.Close()
+
+	recording := &deadlineRecordingConn{Conn: client}
+	deadlines := newConnectionDeadlines(recording)
+	callerDeadline := time.Now().Add(10 * time.Minute)
+	if err := deadlines.setDeadline(callerDeadline); err != nil {
+		t.Fatal(err)
+	}
+	if err := deadlines.beginHandshake(); err != nil {
+		t.Fatal(err)
+	}
+
+	read, write := recording.currentDeadlines()
+	if !read.Before(callerDeadline) || !write.Before(callerDeadline) {
+		t.Fatalf("handshake deadlines = %s/%s, caller = %s", read, write, callerDeadline)
+	}
+
+	shortReadDeadline := time.Now().Add(time.Second)
+	if err := deadlines.setReadDeadline(shortReadDeadline); err != nil {
+		t.Fatal(err)
+	}
+	read, _ = recording.currentDeadlines()
+	if !read.Equal(shortReadDeadline) {
+		t.Fatalf("read deadline = %s, want %s", read, shortReadDeadline)
+	}
+
+	if err := deadlines.endHandshake(); err != nil {
+		t.Fatal(err)
+	}
+	read, write = recording.currentDeadlines()
+	if !read.Equal(shortReadDeadline) || !write.Equal(callerDeadline) {
+		t.Fatalf("restored deadlines = %s/%s, want %s/%s", read, write, shortReadDeadline, callerDeadline)
+	}
+}
+
+type deadlineRecordingConn struct {
+	net.Conn
+	mu    sync.Mutex
+	read  time.Time
+	write time.Time
+}
+
+func (c *deadlineRecordingConn) SetDeadline(t time.Time) error {
+	c.mu.Lock()
+	c.read = t
+	c.write = t
+	c.mu.Unlock()
+	return c.Conn.SetDeadline(t)
+}
+
+func (c *deadlineRecordingConn) SetReadDeadline(t time.Time) error {
+	c.mu.Lock()
+	c.read = t
+	c.mu.Unlock()
+	return c.Conn.SetReadDeadline(t)
+}
+
+func (c *deadlineRecordingConn) SetWriteDeadline(t time.Time) error {
+	c.mu.Lock()
+	c.write = t
+	c.mu.Unlock()
+	return c.Conn.SetWriteDeadline(t)
+}
+
+func (c *deadlineRecordingConn) currentDeadlines() (time.Time, time.Time) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.read, c.write
+}

transport/internet/finalmask/xmc/handshake_test.go

@@ -2,10 +2,16 @@ package xmc
 
 import (
 	"bytes"
+	"crypto/sha256"
 	"crypto/x509"
+	"errors"
+	"fmt"
+	"io"
 	"net"
+	"strings"
 	"sync"
 	"testing"
+	"time"
 )
 
 func deriveTestRSAKey(t *testing.T, password string) ([]byte, []byte) {
@@ -24,6 +30,19 @@ func deriveTestRSAKey(t *testing.T, password string) ([]byte, []byte) {
 	return x509.MarshalPKCS1PrivateKey(key), publicKey
 }
 
+func testLoginProfile(username string) loginProfile {
+	profile := loginProfile{
+		Username:          username,
+		TexturesValue:     strings.Repeat("texture-value-", 40),
+		TexturesSignature: strings.Repeat("texture-signature-", 24),
+	}
+	digest := sha256.Sum256([]byte(username))
+	copy(profile.UUID[:], digest[:16])
+	profile.UUID[6] = (profile.UUID[6] & 0x0f) | 0x40
+	profile.UUID[8] = (profile.UUID[8] & 0x3f) | 0x80
+	return profile
+}
+
 func TestHandshakeSuccess(t *testing.T) {
 	ln, err := net.Listen("tcp", "127.0.0.1:0")
 	if err != nil {
@@ -32,7 +51,7 @@ func TestHandshakeSuccess(t *testing.T) {
 	defer ln.Close()
 
 	password := "super-secure-shared-key-12345"
-	usernames := []string{"test_user"}
+	profiles := []loginProfile{testLoginProfile("test_user")}
 	privateKey, publicKey := deriveTestRSAKey(t, password)
 
 	go func() {
@@ -42,7 +61,7 @@ func TestHandshakeSuccess(t *testing.T) {
 		}
 		defer rawConn.Close()
 
-		server, err := wrapConnServer(rawConn, password, privateKey, publicKey)
+		server, err := wrapConnServer(rawConn, profiles, password, privateKey, publicKey)
 		if err != nil {
 			t.Errorf("failed to wrap server: %v", err)
 			return
@@ -73,7 +92,7 @@ func TestHandshakeSuccess(t *testing.T) {
 	}
 	defer clientRaw.Close()
 
-	client, err := newClientConn(clientRaw, usernames, password, publicKey, "localhost")
+	client, err := newClientConn(clientRaw, profiles, password, publicKey, "localhost")
 	if err != nil {
 		t.Fatalf("failed to create client: %v", err)
 	}
@@ -103,7 +122,7 @@ func TestHandshakePasswordMismatch(t *testing.T) {
 
 	clientPassword := "client-secret-123"
 	serverPassword := "server-secret-456"
-	usernames := []string{"test_user"}
+	profiles := []loginProfile{testLoginProfile("test_user")}
 	serverPrivateKey, serverPublicKey := deriveTestRSAKey(t, serverPassword)
 
 	var wg sync.WaitGroup
@@ -117,7 +136,7 @@ func TestHandshakePasswordMismatch(t *testing.T) {
 		}
 		defer rawConn.Close()
 
-		server, err := wrapConnServer(rawConn, serverPassword, serverPrivateKey, serverPublicKey)
+		server, err := wrapConnServer(rawConn, profiles, serverPassword, serverPrivateKey, serverPublicKey)
 		if err != nil {
 			// Wrapping is synchronous and shouldn't fail initially simply because key derivation works with any string
 			t.Logf("wrapped server: %v", err)
@@ -139,20 +158,233 @@ func TestHandshakePasswordMismatch(t *testing.T) {
 	}
 	defer clientRaw.Close()
 
-	client, err := newClientConn(clientRaw, usernames, clientPassword, serverPublicKey, "localhost")
+	client, err := newClientConn(clientRaw, profiles, clientPassword, serverPublicKey, "localhost")
 	if err != nil {
 		t.Fatalf("failed to create client: %v", err)
 	}
 
 	err = client.handshake()
-	if err != nil {
-		t.Fatalf("client handshake err: %v", err)
+	if err == nil {
+		t.Fatal("expected client handshake to fail due to password mismatch")
 	}
 
-	_, _ = client.Write([]byte{0x1, 0x2, 0x3, 0x4})
-
 	wg.Wait()
 
 	// Check if we lost connection or received error
 	t.Log("Handshake mismatch tested")
 }
+
+func TestHandshakeNetPipeWithKeepAlive(t *testing.T) {
+	clientRaw, serverRaw := net.Pipe()
+	defer clientRaw.Close()
+	defer serverRaw.Close()
+
+	const password = "net-pipe-shared-key"
+	profiles := []loginProfile{testLoginProfile("pipe_user")}
+	privateKey, publicKey := deriveTestRSAKey(t, password)
+	serverDone := make(chan error, 1)
+
+	go func() {
+		server, err := wrapConnServer(serverRaw, profiles, password, privateKey, publicKey)
+		if err != nil {
+			serverDone <- err
+			return
+		}
+
+		request := make([]byte, len("hello server"))
+		if _, err = io.ReadFull(server, request); err != nil {
+			serverDone <- fmt.Errorf("read request: %w", err)
+			return
+		}
+		if string(request) != "hello server" {
+			serverDone <- fmt.Errorf("unexpected request: %q", request)
+			return
+		}
+
+		followupDone := make(chan error, 1)
+		go func() {
+			followup := make([]byte, len("after keepalive"))
+			_, readErr := io.ReadFull(server, followup)
+			if readErr == nil && string(followup) != "after keepalive" {
+				readErr = fmt.Errorf("unexpected followup: %q", followup)
+			}
+			followupDone <- readErr
+		}()
+
+		if err = server.packet.writeKeepAlive(Long(42)); err != nil {
+			serverDone <- fmt.Errorf("write keep-alive: %w", err)
+			return
+		}
+		if _, err = server.Write([]byte("hello client")); err != nil {
+			serverDone <- fmt.Errorf("write response: %w", err)
+			return
+		}
+		serverDone <- <-followupDone
+	}()
+
+	client, err := newClientConn(clientRaw, profiles, password, publicKey, "localhost")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err = client.Write([]byte("hello server")); err != nil {
+		t.Fatalf("write request: %v", err)
+	}
+	response := make([]byte, len("hello client"))
+	if _, err = io.ReadFull(client, response); err != nil {
+		t.Fatalf("read response: %v", err)
+	}
+	if string(response) != "hello client" {
+		t.Fatalf("unexpected response: %q", response)
+	}
+	if _, err = client.Write([]byte("after keepalive")); err != nil {
+		t.Fatalf("write followup: %v", err)
+	}
+
+	select {
+	case err = <-serverDone:
+		if err != nil {
+			t.Fatal(err)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("net.Pipe handshake timed out")
+	}
+}
+
+func TestStatusQueryUnaffected(t *testing.T) {
+	clientRaw, serverRaw := net.Pipe()
+	defer clientRaw.Close()
+	defer serverRaw.Close()
+
+	const password = "status-shared-key"
+	profiles := []loginProfile{testLoginProfile("status_user")}
+	privateKey, publicKey := deriveTestRSAKey(t, password)
+	serverDone := make(chan error, 1)
+	go func() {
+		server, err := wrapConnServer(serverRaw, profiles, password, privateKey, publicKey)
+		if err == nil {
+			err = server.handshake()
+		}
+		serverDone <- err
+	}()
+
+	protocolVersion := Varint(775)
+	serverAddress := String("localhost")
+	serverPort := UnsignedShort(25565)
+	nextState := Varint(1)
+	if err := writePacket(clientRaw, 0x00, &protocolVersion, &serverAddress, &serverPort, &nextState); err != nil {
+		t.Fatal(err)
+	}
+	if err := writePacket(clientRaw, 0x00); err != nil {
+		t.Fatal(err)
+	}
+	response, err := readPacket(clientRaw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if response.packetID != 0x00 {
+		t.Fatalf("status packet id = %d", response.packetID)
+	}
+	var responseJSON String
+	if err = response.readFields(&responseJSON); err != nil {
+		t.Fatal(err)
+	}
+	if string(responseJSON) != statusResponse {
+		t.Fatalf("status response = %q", responseJSON)
+	}
+
+	payload := Long(0x0102030405060708)
+	if err = writePacket(clientRaw, 0x01, &payload); err != nil {
+		t.Fatal(err)
+	}
+	pong, err := readPacket(clientRaw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var receivedPayload Long
+	if pong.packetID != 0x01 {
+		t.Fatalf("pong packet id = %d", pong.packetID)
+	}
+	if err = pong.readFields(&receivedPayload); err != nil {
+		t.Fatal(err)
+	}
+	if receivedPayload != payload {
+		t.Fatalf("pong payload = %x", receivedPayload)
+	}
+
+	select {
+	case err = <-serverDone:
+		if err == nil || !strings.Contains(err.Error(), "ping") {
+			t.Fatalf("server error = %v", err)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("status handshake timed out")
+	}
+}
+
+func TestClientHandshakeHonorsCallerDeadline(t *testing.T) {
+	clientRaw, serverRaw := net.Pipe()
+	defer clientRaw.Close()
+	defer serverRaw.Close()
+
+	const password = "deadline-shared-key"
+	profiles := []loginProfile{testLoginProfile("deadline_user")}
+	_, publicKey := deriveTestRSAKey(t, password)
+	client, err := newClientConn(clientRaw, profiles, password, publicKey, "localhost")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = client.SetDeadline(time.Now().Add(30 * time.Millisecond)); err != nil {
+		t.Fatal(err)
+	}
+
+	started := time.Now()
+	_, err = client.Write([]byte("blocked"))
+	var netErr net.Error
+	if !errors.As(err, &netErr) || !netErr.Timeout() {
+		t.Fatalf("error = %v, want network timeout", err)
+	}
+	if elapsed := time.Since(started); elapsed > 500*time.Millisecond {
+		t.Fatalf("caller deadline took %s", elapsed)
+	}
+}
+
+func TestClientCloseInterruptsHandshake(t *testing.T) {
+	clientRaw, serverRaw := net.Pipe()
+	defer serverRaw.Close()
+
+	const password = "close-shared-key"
+	profiles := []loginProfile{testLoginProfile("close_user")}
+	_, publicKey := deriveTestRSAKey(t, password)
+	client, err := newClientConn(clientRaw, profiles, password, publicKey, "localhost")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	done := make(chan error, 1)
+	go func() {
+		_, writeErr := client.Write([]byte("blocked"))
+		done <- writeErr
+	}()
+	time.Sleep(20 * time.Millisecond)
+	if err = client.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	select {
+	case err = <-done:
+		if err == nil {
+			t.Fatal("handshake unexpectedly succeeded after close")
+		}
+	case <-time.After(time.Second):
+		t.Fatal("close did not interrupt handshake")
+	}
+}
+
+func TestValidateLoginAcknowledgedPacketRejectsData(t *testing.T) {
+	if err := validateLoginAcknowledgedPacket(&mcPacket{packetID: 0x03}); err != nil {
+		t.Fatalf("valid login acknowledged packet: %v", err)
+	}
+	if err := validateLoginAcknowledgedPacket(&mcPacket{packetID: 0x03, data: []byte{0x00}}); err == nil {
+		t.Fatal("login acknowledged packet with trailing data was accepted")
+	}
+}

transport/internet/finalmask/xmc/packet_stream.go

@@ -0,0 +1,184 @@
+package xmc
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+const (
+	configurationClientboundCustomPayload = 0x01
+	configurationServerboundCustomPayload = 0x02
+	configurationKeepAlive                = 0x04
+
+	packetChannel   = "xmc:data"
+	maxPacketData   = 24 * 1024
+	keepAlivePeriod = 15 * time.Second
+)
+
+// packetStream carries the raw proxy byte stream in Minecraft configuration
+// custom payload packets. The configuration state provides bidirectional
+// payload packets and keep-alives without requiring version-specific world data.
+type packetStream struct {
+	reader   io.Reader
+	writer   io.Writer
+	isClient bool
+
+	readMu  sync.Mutex
+	writeMu sync.Mutex
+	pending []byte
+
+	keepAliveID atomic.Int64
+	done        chan struct{}
+	stopOnce    sync.Once
+}
+
+func newPacketStream(reader io.Reader, writer io.Writer, isClient bool) *packetStream {
+	s := &packetStream{
+		reader:   reader,
+		writer:   writer,
+		isClient: isClient,
+		done:     make(chan struct{}),
+	}
+	if !isClient {
+		go s.keepAliveLoop()
+	}
+	return s
+}
+
+func (s *packetStream) Read(p []byte) (int, error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+
+	s.readMu.Lock()
+	defer s.readMu.Unlock()
+
+	if len(s.pending) > 0 {
+		n := copy(p, s.pending)
+		s.pending = s.pending[n:]
+		return n, nil
+	}
+
+	for {
+		packet, err := readPacket(s.reader)
+		if err != nil {
+			return 0, fmt.Errorf("read minecraft packet stream: %w", err)
+		}
+
+		if packet.packetID == s.remoteCustomPayloadID() {
+			payload, ok, err := parseCustomPayload(packet)
+			if err != nil {
+				return 0, err
+			}
+			if !ok || len(payload) == 0 {
+				continue
+			}
+
+			n := copy(p, payload)
+			if n < len(payload) {
+				s.pending = append(s.pending[:0], payload[n:]...)
+			}
+			return n, nil
+		}
+
+		if packet.packetID == configurationKeepAlive {
+			var id Long
+			if err := packet.readFields(&id); err != nil {
+				return 0, fmt.Errorf("read minecraft keep-alive: %w", err)
+			}
+			if s.isClient {
+				if err := s.writeKeepAlive(id); err != nil {
+					return 0, err
+				}
+			}
+		}
+	}
+}
+
+func (s *packetStream) Write(p []byte) (int, error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
+
+	s.writeMu.Lock()
+	defer s.writeMu.Unlock()
+
+	written := 0
+	for written < len(p) {
+		end := written + maxPacketData
+		if end > len(p) {
+			end = len(p)
+		}
+		channel := String(packetChannel)
+		payload := RestBytes(p[written:end])
+		if err := writePacket(s.writer, s.localCustomPayloadID(), &channel, &payload); err != nil {
+			return written, fmt.Errorf("write minecraft custom payload: %w", err)
+		}
+		written = end
+	}
+
+	return written, nil
+}
+
+func (s *packetStream) Stop() {
+	s.stopOnce.Do(func() { close(s.done) })
+}
+
+func (s *packetStream) localCustomPayloadID() int {
+	if s.isClient {
+		return configurationServerboundCustomPayload
+	}
+	return configurationClientboundCustomPayload
+}
+
+func (s *packetStream) remoteCustomPayloadID() int {
+	if s.isClient {
+		return configurationClientboundCustomPayload
+	}
+	return configurationServerboundCustomPayload
+}
+
+func parseCustomPayload(packet *mcPacket) ([]byte, bool, error) {
+	r := bytes.NewReader(packet.data)
+	var channel String
+	if err := channel.readFrom(r); err != nil {
+		return nil, false, fmt.Errorf("read minecraft custom payload channel: %w", err)
+	}
+	if string(channel) != packetChannel {
+		return nil, false, nil
+	}
+	payload := make([]byte, r.Len())
+	if _, err := io.ReadFull(r, payload); err != nil {
+		return nil, false, fmt.Errorf("read minecraft custom payload data: %w", err)
+	}
+	return payload, true, nil
+}
+
+func (s *packetStream) writeKeepAlive(id Long) error {
+	s.writeMu.Lock()
+	defer s.writeMu.Unlock()
+	if err := writePacket(s.writer, configurationKeepAlive, &id); err != nil {
+		return fmt.Errorf("write minecraft keep-alive: %w", err)
+	}
+	return nil
+}
+
+func (s *packetStream) keepAliveLoop() {
+	ticker := time.NewTicker(keepAlivePeriod)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ticker.C:
+			id := Long(s.keepAliveID.Add(1))
+			if err := s.writeKeepAlive(id); err != nil {
+				return
+			}
+		case <-s.done:
+			return
+		}
+	}
+}

transport/internet/finalmask/xmc/packet_stream_test.go

@@ -0,0 +1,102 @@
+package xmc
+
+import (
+	"bytes"
+	"io"
+	"net"
+	"testing"
+)
+
+func TestPacketStreamUsesPlainFraming(t *testing.T) {
+	payload := []byte("hello")
+	var wire bytes.Buffer
+	stream := newPacketStream(bytes.NewReader(nil), &wire, true)
+
+	written, err := stream.Write(payload)
+	if err != nil {
+		t.Fatalf("write payload: %v", err)
+	}
+	if written != len(payload) {
+		t.Fatalf("written = %d, want %d", written, len(payload))
+	}
+	wantOutbound := []byte{0x0f, 0x02, 0x08, 'x', 'm', 'c', ':', 'd', 'a', 't', 'a', 'h', 'e', 'l', 'l', 'o'}
+	if !bytes.Equal(wire.Bytes(), wantOutbound) {
+		t.Fatalf("wire frame = %x, want %x", wire.Bytes(), wantOutbound)
+	}
+
+	wantInbound := append([]byte(nil), wantOutbound...)
+	wantInbound[1] = configurationClientboundCustomPayload
+	reader := newPacketStream(bytes.NewReader(wantInbound), io.Discard, true)
+	got := make([]byte, len(payload))
+	if _, err = io.ReadFull(reader, got); err != nil {
+		t.Fatalf("read payload: %v", err)
+	}
+	if !bytes.Equal(got, payload) {
+		t.Fatalf("payload = %q, want %q", got, payload)
+	}
+}
+
+func TestPacketStreamRoundTrip(t *testing.T) {
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+
+	const password = "packet-stream-shared-key"
+	privateKey, publicKey := deriveTestRSAKey(t, password)
+	profiles := []loginProfile{testLoginProfile("packet_user")}
+	clientPayload := bytes.Repeat([]byte("client-payload-"), 5000)
+	serverPayload := bytes.Repeat([]byte("server-payload-"), 5000)
+	serverDone := make(chan error, 1)
+
+	go func() {
+		rawConn, acceptErr := ln.Accept()
+		if acceptErr != nil {
+			serverDone <- acceptErr
+			return
+		}
+		defer rawConn.Close()
+
+		server, wrapErr := wrapConnServer(rawConn, profiles, password, privateKey, publicKey)
+		if wrapErr != nil {
+			serverDone <- wrapErr
+			return
+		}
+		got := make([]byte, len(clientPayload))
+		if _, readErr := io.ReadFull(server, got); readErr != nil {
+			serverDone <- readErr
+			return
+		}
+		if !bytes.Equal(got, clientPayload) {
+			serverDone <- io.ErrUnexpectedEOF
+			return
+		}
+		_, writeErr := server.Write(serverPayload)
+		serverDone <- writeErr
+	}()
+
+	rawClient, err := net.Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer rawClient.Close()
+
+	client, err := newClientConn(rawClient, profiles, password, publicKey, "localhost")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err = client.Write(clientPayload); err != nil {
+		t.Fatalf("write payload: %v", err)
+	}
+	got := make([]byte, len(serverPayload))
+	if _, err = io.ReadFull(client, got); err != nil {
+		t.Fatalf("read payload: %v", err)
+	}
+	if !bytes.Equal(got, serverPayload) {
+		t.Fatal("server payload mismatch")
+	}
+	if err = <-serverDone; err != nil {
+		t.Fatalf("server: %v", err)
+	}
+}

transport/internet/finalmask/xmc/padding.go

@@ -0,0 +1,432 @@
+package xmc
+
+import (
+	"bytes"
+	"crypto/rand"
+	"fmt"
+	"io"
+	"math/big"
+	"time"
+)
+
+type paddingDirection uint8
+
+const (
+	paddingClientToServer paddingDirection = iota + 1
+	paddingServerToClient
+
+	paddingBufferLength   = 16 * 1024
+	maxPaddingChunkLength = 48 * 1024
+	maxPaddingTurnLength  = 8 * 1024 * 1024
+)
+
+type paddingVariant struct {
+	chunks []int
+	delays []paddingDelayRange
+}
+
+type paddingDelayRange struct {
+	min time.Duration
+	max time.Duration
+}
+
+type paddingTurn struct {
+	direction           paddingDirection
+	minLength           int
+	maxLength           int
+	variants            []paddingVariant
+	startDelay          paddingDelayRange
+	chunkDelay          paddingDelayRange
+	writeChunkMinLength int
+	writeChunkLength    int
+	sendMinLength       int
+	sendMaxLength       int
+	sendVariants        []int
+}
+
+func runPaddingSchedule(reader io.Reader, writer io.Writer, isClient bool, firstTurnPrefixLength int, schedule []paddingTurn) error {
+	if err := validatePaddingSchedule(schedule, firstTurnPrefixLength); err != nil {
+		return err
+	}
+
+	var writeBuffer []byte
+	for i, turn := range schedule {
+		prefixLength := 0
+		if i == 0 {
+			prefixLength = firstTurnPrefixLength
+		}
+
+		localSends := isClient == (turn.direction == paddingClientToServer)
+		if localSends {
+			if err := writePaddingTurnWithBuffer(writer, turn, prefixLength, time.Sleep, &writeBuffer); err != nil {
+				return fmt.Errorf("write padding turn %d: %w", i, err)
+			}
+			continue
+		}
+		if err := readPaddingTurn(reader, turn, prefixLength); err != nil {
+			return fmt.Errorf("read padding turn %d: %w", i, err)
+		}
+	}
+	return nil
+}
+
+func validatePaddingSchedule(schedule []paddingTurn, firstTurnPrefixLength int) error {
+	if len(schedule) == 0 {
+		return fmt.Errorf("empty padding schedule")
+	}
+	if firstTurnPrefixLength < 0 {
+		return fmt.Errorf("negative first turn prefix length: %d", firstTurnPrefixLength)
+	}
+	if firstTurnPrefixLength > 0 && schedule[0].direction != paddingClientToServer {
+		return fmt.Errorf("first prefixed padding turn is not client-to-server")
+	}
+
+	for i, turn := range schedule {
+		if turn.direction != paddingClientToServer && turn.direction != paddingServerToClient {
+			return fmt.Errorf("padding turn %d has invalid direction: %d", i, turn.direction)
+		}
+		if err := validatePaddingDelayRange(turn.startDelay); err != nil {
+			return fmt.Errorf("padding turn %d has an invalid start delay: %w", i, err)
+		}
+		if err := validatePaddingDelayRange(turn.chunkDelay); err != nil {
+			return fmt.Errorf("padding turn %d has an invalid chunk delay: %w", i, err)
+		}
+		if turn.writeChunkMinLength < 0 || turn.writeChunkLength < turn.writeChunkMinLength || turn.writeChunkLength > maxPaddingChunkLength {
+			return fmt.Errorf("padding turn %d has an invalid write chunk range: %d-%d", i, turn.writeChunkMinLength, turn.writeChunkLength)
+		}
+		if len(turn.variants) > 0 && turn.writeChunkLength != 0 {
+			return fmt.Errorf("padding turn %d combines variants with generated write chunks", i)
+		}
+
+		minLength, maxLength, err := paddingTurnBounds(turn)
+		if err != nil {
+			return fmt.Errorf("padding turn %d: %w", i, err)
+		}
+		hasSendRange := turn.sendMinLength != 0 || turn.sendMaxLength != 0
+		if hasSendRange {
+			if len(turn.variants) > 0 {
+				return fmt.Errorf("padding turn %d combines variants with a send range", i)
+			}
+			if turn.sendMinLength < minLength || turn.sendMaxLength < turn.sendMinLength || turn.sendMaxLength > maxLength {
+				return fmt.Errorf("padding turn %d has an invalid send range: %d-%d", i, turn.sendMinLength, turn.sendMaxLength)
+			}
+		}
+		if i == 0 && minLength-firstTurnPrefixLength < 1 {
+			return fmt.Errorf("padding turn 0 is too short for %d prefix bytes", firstTurnPrefixLength)
+		}
+		if i == 0 && len(turn.variants) > 0 {
+			for j, variant := range turn.variants {
+				if _, _, err = trimPaddingPrefix(variant, firstTurnPrefixLength); err != nil {
+					return fmt.Errorf("padding turn 0 variant %d: %w", j, err)
+				}
+			}
+		}
+		if i > 0 && turn.direction == schedule[i-1].direction {
+			return fmt.Errorf("padding turns %d and %d have the same direction", i-1, i)
+		}
+	}
+	return nil
+}
+
+func writePaddingTurn(w io.Writer, turn paddingTurn, prefixLength int) error {
+	return writePaddingTurnWithSleep(w, turn, prefixLength, time.Sleep)
+}
+
+func writePaddingTurnWithSleep(w io.Writer, turn paddingTurn, prefixLength int, sleep func(time.Duration)) error {
+	return writePaddingTurnWithBuffer(w, turn, prefixLength, sleep, nil)
+}
+
+func writePaddingTurnWithBuffer(w io.Writer, turn paddingTurn, prefixLength int, sleep func(time.Duration), reusableBuffer *[]byte) error {
+	startDelay, err := randomPaddingDelay(turn.startDelay)
+	if err != nil {
+		return fmt.Errorf("select padding start delay: %w", err)
+	}
+	if startDelay > 0 {
+		sleep(startDelay)
+	}
+
+	targetLength, chunks, delays, err := selectPaddingVariant(turn, prefixLength)
+	if err != nil {
+		return err
+	}
+	recordLength := targetLength - prefixLength
+	if recordLength < 1 {
+		return fmt.Errorf("target length %d leaves an invalid record length %d", targetLength, recordLength)
+	}
+
+	encodedLength := Varint(recordLength)
+	var header bytes.Buffer
+	if err = encodedLength.writeTo(&header); err != nil {
+		return fmt.Errorf("write padding header: %w", err)
+	}
+	if len(chunks) == 0 {
+		writeChunkLength := turn.writeChunkLength
+		if writeChunkLength == 0 {
+			writeChunkLength = paddingBufferLength
+		} else if turn.writeChunkMinLength > 0 {
+			writeChunkLength, err = randomPaddingTarget(turn.writeChunkMinLength, writeChunkLength)
+			if err != nil {
+				return fmt.Errorf("select padding write chunk length: %w", err)
+			}
+		}
+		chunks = defaultPaddingChunks(recordLength, writeChunkLength)
+		delays = make([]paddingDelayRange, len(chunks))
+		for i := 1; i < len(delays); i++ {
+			delays[i] = turn.chunkDelay
+		}
+	}
+	if chunks[0] < header.Len() {
+		return fmt.Errorf("first padding chunk %d is shorter than header %d", chunks[0], header.Len())
+	}
+
+	maxChunkLength := 0
+	for _, chunkLength := range chunks {
+		if chunkLength < 1 || chunkLength > maxPaddingChunkLength {
+			return fmt.Errorf("invalid padding chunk length: %d", chunkLength)
+		}
+		maxChunkLength = max(maxChunkLength, chunkLength)
+	}
+	var buffer []byte
+	if reusableBuffer == nil {
+		buffer = make([]byte, maxChunkLength)
+	} else {
+		if cap(*reusableBuffer) < maxChunkLength {
+			*reusableBuffer = make([]byte, maxChunkLength)
+		}
+		buffer = (*reusableBuffer)[:maxChunkLength]
+		clear(buffer)
+	}
+	copy(buffer, header.Bytes())
+	written := 0
+	for i, chunkLength := range chunks {
+		if i < len(delays) {
+			delay, delayErr := randomPaddingDelay(delays[i])
+			if delayErr != nil {
+				return fmt.Errorf("select padding chunk %d delay: %w", i, delayErr)
+			}
+			if delay > 0 {
+				sleep(delay)
+			}
+		}
+		if err = writeFull(w, buffer[:chunkLength]); err != nil {
+			return fmt.Errorf("write padding chunk %d: %w", i, err)
+		}
+		written += chunkLength
+		if i == 0 {
+			clear(buffer[:header.Len()])
+		}
+	}
+	if written != recordLength {
+		return fmt.Errorf("padding chunks total %d, want %d", written, recordLength)
+	}
+	return nil
+}
+
+func readPaddingTurn(r io.Reader, turn paddingTurn, prefixLength int) error {
+	encodedLength, headerLength, err := readVarintWithLength(r)
+	if err != nil {
+		return fmt.Errorf("read padding header: %w", err)
+	}
+	recordLength := int(encodedLength)
+	if recordLength < headerLength || recordLength > maxPaddingTurnLength {
+		return fmt.Errorf("invalid padding record length: %d", recordLength)
+	}
+	totalLength := prefixLength + recordLength
+	if !paddingTurnAcceptsLength(turn, totalLength) {
+		if len(turn.variants) > 0 {
+			return fmt.Errorf("padding turn length %d is not an allowed variant", totalLength)
+		}
+		return fmt.Errorf("padding turn length %d is outside %d-%d", totalLength, turn.minLength, turn.maxLength)
+	}
+
+	var buffer [paddingBufferLength]byte
+	remaining := recordLength - headerLength
+	for remaining > 0 {
+		chunkLength := min(remaining, len(buffer))
+		if _, err := io.ReadFull(r, buffer[:chunkLength]); err != nil {
+			return fmt.Errorf("read padding body: %w", err)
+		}
+		remaining -= chunkLength
+	}
+	return nil
+}
+
+func selectPaddingVariant(turn paddingTurn, prefixLength int) (int, []int, []paddingDelayRange, error) {
+	if len(turn.variants) == 0 {
+		minimum, maximum := turn.minLength, turn.maxLength
+		if turn.sendMinLength != 0 || turn.sendMaxLength != 0 {
+			minimum, maximum = turn.sendMinLength, turn.sendMaxLength
+		}
+		targetLength, err := randomPaddingTarget(minimum, maximum)
+		return targetLength, nil, nil, err
+	}
+
+	indices := turn.sendVariants
+	if len(indices) == 0 {
+		indices = make([]int, len(turn.variants))
+		for i := range indices {
+			indices[i] = i
+		}
+	}
+	selected, err := randomPaddingIndex(len(indices))
+	if err != nil {
+		return 0, nil, nil, err
+	}
+	variantIndex := indices[selected]
+	if variantIndex < 0 || variantIndex >= len(turn.variants) {
+		return 0, nil, nil, fmt.Errorf("invalid send variant index: %d", variantIndex)
+	}
+	variant := turn.variants[variantIndex]
+	targetLength := paddingVariantLength(variant)
+	chunks, delays, err := trimPaddingPrefix(variant, prefixLength)
+	if err != nil {
+		return 0, nil, nil, err
+	}
+	return targetLength, chunks, delays, nil
+}
+
+func trimPaddingPrefix(variant paddingVariant, prefixLength int) ([]int, []paddingDelayRange, error) {
+	remainingPrefix := prefixLength
+	firstChunk := 0
+	for firstChunk < len(variant.chunks) && remainingPrefix > 0 {
+		chunkLength := variant.chunks[firstChunk]
+		if remainingPrefix < chunkLength {
+			return nil, nil, fmt.Errorf("prefix length %d splits chunk %d", prefixLength, firstChunk)
+		}
+		remainingPrefix -= chunkLength
+		firstChunk++
+	}
+	if remainingPrefix != 0 || firstChunk == len(variant.chunks) {
+		return nil, nil, fmt.Errorf("prefix length %d leaves no padding record", prefixLength)
+	}
+
+	chunks := append([]int(nil), variant.chunks[firstChunk:]...)
+	delays := make([]paddingDelayRange, len(chunks))
+	if len(variant.delays) > 0 {
+		copy(delays, variant.delays[firstChunk:])
+	}
+	return chunks, delays, nil
+}
+
+func defaultPaddingChunks(recordLength, writeChunkLength int) []int {
+	chunks := make([]int, 0, (recordLength+writeChunkLength-1)/writeChunkLength)
+	for remaining := recordLength; remaining > 0; {
+		chunkLength := min(remaining, writeChunkLength)
+		chunks = append(chunks, chunkLength)
+		remaining -= chunkLength
+	}
+	return chunks
+}
+
+func paddingTurnBounds(turn paddingTurn) (int, int, error) {
+	if len(turn.variants) == 0 {
+		if turn.minLength < 1 || turn.maxLength < turn.minLength || turn.maxLength > maxPaddingTurnLength {
+			return 0, 0, fmt.Errorf("invalid range: %d-%d", turn.minLength, turn.maxLength)
+		}
+		return turn.minLength, turn.maxLength, nil
+	}
+	if turn.minLength != 0 || turn.maxLength != 0 {
+		return 0, 0, fmt.Errorf("variants cannot be combined with a length range")
+	}
+
+	minLength := maxPaddingTurnLength + 1
+	maxLength := 0
+	for i, variant := range turn.variants {
+		if len(variant.chunks) == 0 {
+			return 0, 0, fmt.Errorf("variant %d has no chunks", i)
+		}
+		if len(variant.delays) != 0 && len(variant.delays) != len(variant.chunks) {
+			return 0, 0, fmt.Errorf("variant %d has %d chunks and %d delays", i, len(variant.chunks), len(variant.delays))
+		}
+		for j, chunkLength := range variant.chunks {
+			if chunkLength < 1 || chunkLength > maxPaddingChunkLength {
+				return 0, 0, fmt.Errorf("variant %d chunk %d has invalid length: %d", i, j, chunkLength)
+			}
+			if len(variant.delays) > 0 {
+				if err := validatePaddingDelayRange(variant.delays[j]); err != nil {
+					return 0, 0, fmt.Errorf("variant %d chunk %d has an invalid delay: %w", i, j, err)
+				}
+			}
+		}
+		length := paddingVariantLength(variant)
+		if length > maxPaddingTurnLength {
+			return 0, 0, fmt.Errorf("variant %d is too long: %d", i, length)
+		}
+		minLength = min(minLength, length)
+		maxLength = max(maxLength, length)
+	}
+	for _, index := range turn.sendVariants {
+		if index < 0 || index >= len(turn.variants) {
+			return 0, 0, fmt.Errorf("invalid send variant index: %d", index)
+		}
+	}
+	return minLength, maxLength, nil
+}
+
+func paddingTurnAcceptsLength(turn paddingTurn, length int) bool {
+	if len(turn.variants) == 0 {
+		return length >= turn.minLength && length <= turn.maxLength
+	}
+	for _, variant := range turn.variants {
+		if paddingVariantLength(variant) == length {
+			return true
+		}
+	}
+	return false
+}
+
+func paddingVariantLength(variant paddingVariant) int {
+	total := 0
+	for _, chunkLength := range variant.chunks {
+		total += chunkLength
+	}
+	return total
+}
+
+func validatePaddingDelayRange(delay paddingDelayRange) error {
+	if delay.min < 0 || delay.max < delay.min {
+		return fmt.Errorf("invalid range: %s-%s", delay.min, delay.max)
+	}
+	return nil
+}
+
+func randomPaddingDelay(delay paddingDelayRange) (time.Duration, error) {
+	if err := validatePaddingDelayRange(delay); err != nil {
+		return 0, err
+	}
+	if delay.min == delay.max {
+		return delay.min, nil
+	}
+	span := int64(delay.max-delay.min) + 1
+	offset, err := rand.Int(rand.Reader, big.NewInt(span))
+	if err != nil {
+		return 0, fmt.Errorf("select padding delay: %w", err)
+	}
+	return delay.min + time.Duration(offset.Int64()), nil
+}
+
+func randomPaddingIndex(length int) (int, error) {
+	if length < 1 {
+		return 0, fmt.Errorf("select from empty padding choices")
+	}
+	if length == 1 {
+		return 0, nil
+	}
+	index, err := rand.Int(rand.Reader, big.NewInt(int64(length)))
+	if err != nil {
+		return 0, fmt.Errorf("select padding choice: %w", err)
+	}
+	return int(index.Int64()), nil
+}
+
+func randomPaddingTarget(minLength, maxLength int) (int, error) {
+	if minLength == maxLength {
+		return minLength, nil
+	}
+	span := int64(maxLength-minLength) + 1
+	offset, err := rand.Int(rand.Reader, big.NewInt(span))
+	if err != nil {
+		return 0, fmt.Errorf("select padding length: %w", err)
+	}
+	return minLength + int(offset.Int64()), nil
+}

transport/internet/finalmask/xmc/padding_preset.go

@@ -0,0 +1,282 @@
+package xmc
+
+import (
+	"time"
+)
+
+// Length and write-boundary templates come from controlled Minecraft 26.1.2
+// logins. Timing deliberately uses broad random bands that preserve only the
+// rough ordering of short and long phases; it does not replay captured delays.
+var startupPaddingSchedule2612 = []paddingTurn{
+	{
+		direction: paddingClientToServer,
+		variants: []paddingVariant{
+			paddingVariantFromChunks(2, 26, 16),
+		},
+	},
+	{
+		direction: paddingServerToClient,
+		variants: []paddingVariant{
+			paddingVariantFromChunks(26, 21, 25),
+		},
+		startDelay: millisecondRange(0, 20),
+	},
+	{
+		direction: paddingClientToServer,
+		variants: []paddingVariant{
+			paddingVariantFromChunks(25),
+		},
+		startDelay: millisecondRange(2, 22),
+	},
+	{
+		direction: paddingServerToClient,
+		variants: []paddingVariant{
+			registryPaddingVariant(),
+		},
+		startDelay: millisecondRange(20, 50),
+	},
+	{
+		direction: paddingClientToServer,
+		variants: []paddingVariant{
+			paddingVariantFromChunks(2),
+		},
+		startDelay: millisecondRange(10, 35),
+	},
+	{
+		direction: paddingServerToClient,
+		variants: []paddingVariant{
+			playStartPaddingVariant(4941, 252, 259, 267, 268, 251, 303, 259, 264, 54, 346),
+			playStartPaddingVariant(4941, 262, 284, 272, 260, 260, 313, 264, 151, 224, 207, 215, 224, 390),
+			playStartPaddingVariant(4941, 257, 272, 275, 260, 260, 313, 283, 274, 226, 207, 230, 215, 204, 221, 352),
+			playStartPaddingVariant(4941, 259, 272, 288, 260, 260, 311, 270, 70, 236, 223, 201, 210, 352),
+			playStartPaddingVariant(4941, 255, 269, 277, 263, 260, 136, 207, 210, 232, 325),
+			playStartPaddingVariant(4941, 259, 270, 274, 263, 258, 327, 170, 210, 375),
+			playStartPaddingVariant(4941, 257, 275, 291, 260, 260, 325, 269, 70, 230, 226, 207, 221, 352),
+			playStartPaddingVariant(4941, 252, 273, 262, 252, 254, 306, 93),
+			playStartPaddingVariant(4941, 273, 270, 269, 258, 256, 322, 221, 207, 215, 438),
+			playStartPaddingVariant(4941, 259, 275, 274, 250, 258, 308, 267, 154, 233, 209, 207, 213, 393),
+			playStartPaddingVariant(4941, 254, 267, 272, 260, 253, 311, 167, 204, 232, 207, 481, 8),
+			playStartPaddingVariant(4941, 259, 269, 272, 261, 313, 207, 213, 500, 19),
+			playStartPaddingVariant(4941, 262, 269, 274, 263, 274, 311, 270, 242, 210, 229, 221, 210, 431),
+			playStartPaddingVariant(4941, 259, 265, 277, 263, 277, 316, 269, 156, 204, 210, 226, 207, 413),
+			playStartPaddingVariant(4941, 215, 251, 249, 317, 260, 270, 249, 52),
+			playStartPaddingVariant(4941, 224, 263, 277, 316, 267, 272, 260, 138, 230, 226, 207, 204, 352),
+			playStartPaddingVariant(4941, 221, 258, 263, 319, 269, 288, 263, 136, 204, 210, 220, 207, 378),
+			playStartPaddingVariant(4941, 221, 258, 260, 316, 273, 291, 226, 204, 229, 213, 489, 8),
+			playStartPaddingVariant(4941, 238, 260, 261, 306, 272, 277, 260, 224, 241, 212, 207, 204, 393),
+			playStartPaddingVariant(4941, 224, 260, 260, 309, 272, 277, 277, 138, 207, 207, 212, 241, 352),
+		},
+		startDelay: millisecondRange(35, 50),
+	},
+}
+
+// These turns cover the finite Play-state tail through the client's
+// player_loaded packet. Bounds are the observed per-turn minima and maxima
+// across 20 controlled 26.1.2 logins; payload bytes remain opaque padding.
+var playJoinPaddingSchedule2612 = []paddingTurn{
+	clientPlayPaddingTurn(6, 883),
+	serverPlayPaddingTurn(346, 58638),
+	clientPlayPaddingTurn(6, 887),
+	serverPlayPaddingTurn(388, 61077),
+	clientPlayPaddingTurn(2, 50),
+	serverPlayPaddingTurn(575, 65584),
+	clientPlayPaddingTurn(6, 45),
+	serverPlayPaddingTurn(86, 63563),
+	clientPlayPaddingTurn(2, 44),
+	serverPlayPaddingTurn(42, 51983),
+	clientPlayPaddingTurn(2, 851),
+	serverPlayPaddingTurn(309, 25083),
+	clientPlayPaddingTurn(2, 19),
+	serverPlayPaddingTurn(74, 63885),
+	clientPlayPaddingTurn(8, 24),
+	serverPlayPaddingTurn(30, 66128),
+	clientPlayPaddingTurn(2, 19),
+	serverPlayPaddingTurn(26, 35818),
+	clientPlayPaddingTurn(6, 19),
+	serverPlayPaddingTurn(35, 59407),
+	clientPlayPaddingTurn(6, 19),
+	serverPlayPaddingTurn(37, 65328),
+	clientPlayPaddingTurn(2, 19),
+	serverPlayPaddingTurn(26, 60622),
+	clientPlayPaddingTurn(6, 19),
+	serverPlayPaddingTurn(11, 60808),
+	clientPlayPaddingTurn(8, 43),
+	serverPlayPaddingTurn(55, 62027),
+	clientPlayPaddingTurn(2, 19),
+	serverPlayPaddingTurn(427, 65622),
+	clientPlayPaddingTurn(5, 19),
+	serverPlayPaddingTurn(35, 59401),
+	clientPlayPaddingTurn(6, 19),
+}
+
+type paddingLengthRange2612 struct {
+	minimum int
+	maximum int
+}
+
+type serverPlayLengthBranches2612 struct {
+	small paddingLengthRange2612
+	large paddingLengthRange2612
+}
+
+var serverPlayBranches2612 = []serverPlayLengthBranches2612{
+	{small: paddingLengthRange2612{346, 18812}, large: paddingLengthRange2612{51702, 58638}},
+	{small: paddingLengthRange2612{388, 20689}, large: paddingLengthRange2612{51445, 61077}},
+	{small: paddingLengthRange2612{575, 20915}, large: paddingLengthRange2612{41428, 65584}},
+	{small: paddingLengthRange2612{86, 2772}, large: paddingLengthRange2612{41428, 63563}},
+	{small: paddingLengthRange2612{42, 26813}, large: paddingLengthRange2612{51983, 51983}},
+	{small: paddingLengthRange2612{309, 19484}, large: paddingLengthRange2612{24837, 25083}},
+	{small: paddingLengthRange2612{74, 40686}, large: paddingLengthRange2612{63885, 63885}},
+	{small: paddingLengthRange2612{30, 44114}, large: paddingLengthRange2612{66128, 66128}},
+	{small: paddingLengthRange2612{26, 1464}, large: paddingLengthRange2612{9941, 35818}},
+	{small: paddingLengthRange2612{35, 42885}, large: paddingLengthRange2612{52194, 59407}},
+	{small: paddingLengthRange2612{37, 47553}, large: paddingLengthRange2612{61765, 65328}},
+	{small: paddingLengthRange2612{26, 1121}, large: paddingLengthRange2612{16162, 60622}},
+	{small: paddingLengthRange2612{11, 45629}, large: paddingLengthRange2612{60808, 60808}},
+	{small: paddingLengthRange2612{55, 10035}, large: paddingLengthRange2612{30237, 62027}},
+	{small: paddingLengthRange2612{427, 52536}, large: paddingLengthRange2612{64014, 65622}},
+	{small: paddingLengthRange2612{35, 22708}, large: paddingLengthRange2612{38987, 59401}},
+}
+
+// Each mask preserves only the small/large branch order from one baseline
+// login. Actual lengths and timing are selected randomly inside each branch.
+var serverPlayBranchMasks2612 = []uint32{
+	0x011c, 0x090a, 0x0821, 0xe921, 0x2102,
+	0x0844, 0xa101, 0x1106, 0x2e00, 0xab01,
+	0xe900, 0xac01, 0xab01, 0x8b80, 0x0808,
+	0x2001, 0x0901, 0x000a, 0x2c01, 0x0801,
+}
+
+type clientPlayBurst2612 struct {
+	playIndex int
+	regular   paddingLengthRange2612
+	burst     paddingLengthRange2612
+}
+
+var clientPlayBursts2612 = []clientPlayBurst2612{
+	{playIndex: 0, regular: paddingLengthRange2612{6, 44}, burst: paddingLengthRange2612{877, 883}},
+	{playIndex: 2, regular: paddingLengthRange2612{6, 45}, burst: paddingLengthRange2612{884, 887}},
+	{playIndex: 10, regular: paddingLengthRange2612{2, 19}, burst: paddingLengthRange2612{851, 851}},
+}
+
+// The 20 samples placed the one client initialization burst in these slots.
+var clientPlayBurstChoices2612 = []int{
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	1, 1,
+	2,
+}
+
+var paddingSchedule2612 = buildPaddingSchedule2612()
+
+func buildPaddingSchedule2612() []paddingTurn {
+	schedule := make([]paddingTurn, 0, len(startupPaddingSchedule2612)+len(playJoinPaddingSchedule2612))
+	schedule = append(schedule, startupPaddingSchedule2612...)
+	schedule = append(schedule, playJoinPaddingSchedule2612...)
+	return schedule
+}
+
+func clientPlayPaddingTurn(minimum, maximum int) paddingTurn {
+	return paddingTurn{
+		direction:        paddingClientToServer,
+		minLength:        minimum,
+		maxLength:        maximum,
+		startDelay:       millisecondRange(1, 30),
+		writeChunkLength: 1024,
+	}
+}
+
+func serverPlayPaddingTurn(minimum, maximum int) paddingTurn {
+	return paddingTurn{
+		direction:           paddingServerToClient,
+		minLength:           minimum,
+		maxLength:           maximum,
+		startDelay:          millisecondRange(1, 45),
+		chunkDelay:          millisecondRange(1, 4),
+		writeChunkMinLength: 32 * 1024,
+		writeChunkLength:    maxPaddingChunkLength,
+	}
+}
+
+func newClientPaddingSchedule2612() ([]paddingTurn, error) {
+	choice, err := randomPaddingIndex(len(clientPlayBurstChoices2612))
+	if err != nil {
+		return nil, err
+	}
+	selectedBurst := clientPlayBurstChoices2612[choice]
+	schedule := append([]paddingTurn(nil), paddingSchedule2612...)
+	for i, burst := range clientPlayBursts2612 {
+		lengthRange := burst.regular
+		if i == selectedBurst {
+			lengthRange = burst.burst
+		}
+		turn := &schedule[len(startupPaddingSchedule2612)+burst.playIndex]
+		turn.sendMinLength = lengthRange.minimum
+		turn.sendMaxLength = lengthRange.maximum
+	}
+	return schedule, nil
+}
+
+type paddingPause struct {
+	chunk int
+	delay paddingDelayRange
+}
+
+func paddingVariantFromChunks(chunks ...int) paddingVariant {
+	return paddingVariant{chunks: chunks}
+}
+
+func pacedPaddingVariant(chunks []int, pauses ...paddingPause) paddingVariant {
+	delays := make([]paddingDelayRange, len(chunks))
+	for _, pause := range pauses {
+		if pause.chunk < 0 || pause.chunk >= len(delays) {
+			panic("xmc: padding pause index is outside its chunk template")
+		}
+		delays[pause.chunk] = pause.delay
+	}
+	return paddingVariant{chunks: chunks, delays: delays}
+}
+
+func registryPaddingVariant() paddingVariant {
+	return pacedPaddingVariant(
+		[]int{1590, 226, 329, 229, 186, 151, 78, 81, 79, 235, 67, 67, 78, 71, 82, 74, 982, 117, 1118, 1038, 970, 400, 239, 49, 50, 95, 65, 104, 32320, 2},
+		paddingPause{28, millisecondRange(1, 4)},
+		paddingPause{29, millisecondRange(44, 61)},
+	)
+}
+
+func playStartPaddingVariant(chunks ...int) paddingVariant {
+	if len(chunks) < 2 {
+		panic("xmc: play start padding variant needs at least two chunks")
+	}
+	return pacedPaddingVariant(
+		chunks,
+		paddingPause{len(chunks) / 2, millisecondRange(1, 5)},
+		paddingPause{len(chunks) - 1, millisecondRange(9, 20)},
+	)
+}
+
+func millisecondRange(minimum, maximum int) paddingDelayRange {
+	return paddingDelayRange{
+		min: time.Duration(minimum) * time.Millisecond,
+		max: time.Duration(maximum) * time.Millisecond,
+	}
+}
+
+func newServerPaddingSchedule2612() ([]paddingTurn, error) {
+	schedule := append([]paddingTurn(nil), paddingSchedule2612...)
+	profileIndex, err := randomPaddingIndex(len(serverPlayBranchMasks2612))
+	if err != nil {
+		return nil, err
+	}
+	profile := serverPlayBranchMasks2612[profileIndex]
+	for i, branches := range serverPlayBranches2612 {
+		lengthRange := branches.small
+		if profile&(1<<i) != 0 {
+			lengthRange = branches.large
+		}
+		turn := &schedule[len(startupPaddingSchedule2612)+1+i*2]
+		turn.sendMinLength = lengthRange.minimum
+		turn.sendMaxLength = lengthRange.maximum
+	}
+	return schedule, nil
+}

transport/internet/finalmask/xmc/padding_test.go

@@ -0,0 +1,618 @@
+package xmc
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"net"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestPaddingTurnReachesFinalTargetLength(t *testing.T) {
+	turn := paddingTurn{direction: paddingClientToServer, minLength: 128, maxLength: 128}
+	const prefixLength = 3
+	var encoded bytes.Buffer
+	if err := writePaddingTurn(&encoded, turn, prefixLength); err != nil {
+		t.Fatal(err)
+	}
+	if got := prefixLength + encoded.Len(); got != turn.minLength {
+		t.Fatalf("total turn length = %d, want %d", got, turn.minLength)
+	}
+	encodedReader := bytes.NewReader(encoded.Bytes())
+	var recordLength Varint
+	if err := recordLength.readFrom(encodedReader); err != nil {
+		t.Fatal(err)
+	}
+	if got := int(recordLength); got != encoded.Len() {
+		t.Fatalf("record length = %d, encoded = %d", got, encoded.Len())
+	}
+	if err := readPaddingTurn(bytes.NewReader(encoded.Bytes()), turn, prefixLength); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestPaddingTurnSupportsThreeByteTarget(t *testing.T) {
+	turn := paddingTurn{direction: paddingClientToServer, minLength: 3, maxLength: 3}
+	var encoded bytes.Buffer
+	if err := writePaddingTurn(&encoded, turn, 0); err != nil {
+		t.Fatal(err)
+	}
+	if got := encoded.Len(); got != 3 {
+		t.Fatalf("padding length = %d, want 3", got)
+	}
+	if err := readPaddingTurn(bytes.NewReader(encoded.Bytes()), turn, 0); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestPaddingTurnVarintBoundaries(t *testing.T) {
+	for _, targetLength := range []int{127, 128, 16383, 16384} {
+		t.Run(strconv.Itoa(targetLength), func(t *testing.T) {
+			turn := paddingTurn{direction: paddingClientToServer, minLength: targetLength, maxLength: targetLength}
+			var encoded bytes.Buffer
+			if err := writePaddingTurn(&encoded, turn, 0); err != nil {
+				t.Fatal(err)
+			}
+			if encoded.Len() != targetLength {
+				t.Fatalf("padding length = %d, want %d", encoded.Len(), targetLength)
+			}
+			if err := readPaddingTurn(bytes.NewReader(encoded.Bytes()), turn, 0); err != nil {
+				t.Fatal(err)
+			}
+		})
+	}
+}
+
+func TestPaddingTurnRandomRange(t *testing.T) {
+	turn := paddingTurn{direction: paddingServerToClient, minLength: 127, maxLength: 129}
+	seen := make(map[int]bool)
+	for range 100 {
+		var encoded bytes.Buffer
+		if err := writePaddingTurn(&encoded, turn, 0); err != nil {
+			t.Fatal(err)
+		}
+		if encoded.Len() < turn.minLength || encoded.Len() > turn.maxLength {
+			t.Fatalf("padding length = %d", encoded.Len())
+		}
+		seen[encoded.Len()] = true
+	}
+	if len(seen) < 2 {
+		t.Fatalf("padding range did not vary: %v", seen)
+	}
+}
+
+func TestPaddingTurnUsesRestrictedSendRange(t *testing.T) {
+	turn := paddingTurn{
+		direction:     paddingServerToClient,
+		minLength:     3,
+		maxLength:     100,
+		sendMinLength: 90,
+		sendMaxLength: 100,
+	}
+	seen := make(map[int]bool)
+	for range 100 {
+		var encoded bytes.Buffer
+		if err := writePaddingTurn(&encoded, turn, 0); err != nil {
+			t.Fatal(err)
+		}
+		if encoded.Len() < turn.sendMinLength || encoded.Len() > turn.sendMaxLength {
+			t.Fatalf("padding length = %d", encoded.Len())
+		}
+		seen[encoded.Len()] = true
+		if err := readPaddingTurn(bytes.NewReader(encoded.Bytes()), turn, 0); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if len(seen) < 2 {
+		t.Fatalf("restricted send range did not vary: %v", seen)
+	}
+}
+
+func TestPaddingScheduleSynchronizesDirections(t *testing.T) {
+	client, server := net.Pipe()
+	defer client.Close()
+	defer server.Close()
+
+	schedule := []paddingTurn{
+		{direction: paddingClientToServer, minLength: 33, maxLength: 33},
+		{direction: paddingServerToClient, minLength: 4097, maxLength: 4097},
+		{direction: paddingClientToServer, minLength: 16385, maxLength: 16385},
+	}
+	serverDone := make(chan error, 1)
+	go func() {
+		serverDone <- runPaddingSchedule(server, server, false, 3, schedule)
+	}()
+	if err := runPaddingSchedule(client, client, true, 3, schedule); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case err := <-serverDone:
+		if err != nil {
+			t.Fatal(err)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("server padding schedule did not complete")
+	}
+}
+
+func TestReadPaddingTurnHandlesFragmentedInput(t *testing.T) {
+	turn := paddingTurn{direction: paddingClientToServer, minLength: 1024, maxLength: 1024}
+	var encoded bytes.Buffer
+	if err := writePaddingTurn(&encoded, turn, 0); err != nil {
+		t.Fatal(err)
+	}
+	if err := readPaddingTurn(&oneByteReader{reader: bytes.NewReader(encoded.Bytes())}, turn, 0); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestReadPaddingTurnRejectsInvalidLength(t *testing.T) {
+	turn := paddingTurn{direction: paddingClientToServer, minLength: 64, maxLength: 96}
+	data := encodePaddingLength(t, 63)
+	if err := readPaddingTurn(bytes.NewReader(data), turn, 0); err == nil || !strings.Contains(err.Error(), "outside") {
+		t.Fatalf("error = %v", err)
+	}
+}
+
+func TestReadPaddingTurnRejectsNonCanonicalHeader(t *testing.T) {
+	turn := paddingTurn{direction: paddingClientToServer, minLength: 3, maxLength: 3}
+	err := readPaddingTurn(bytes.NewReader([]byte{0x83, 0x00, 0x00}), turn, 0)
+	if err == nil || !strings.Contains(err.Error(), "non-canonical") {
+		t.Fatalf("error = %v", err)
+	}
+}
+
+func TestReadPaddingTurnRejectsTruncatedBody(t *testing.T) {
+	turn := paddingTurn{direction: paddingClientToServer, minLength: 64, maxLength: 64}
+	data := encodePaddingLength(t, 64)
+	if err := readPaddingTurn(bytes.NewReader(data), turn, 0); err == nil || !strings.Contains(err.Error(), "body") {
+		t.Fatalf("error = %v", err)
+	}
+}
+
+func TestReadPaddingTurnHonorsConnectionTimeout(t *testing.T) {
+	client, server := net.Pipe()
+	defer client.Close()
+	defer server.Close()
+
+	if err := server.SetReadDeadline(time.Now().Add(20 * time.Millisecond)); err != nil {
+		t.Fatal(err)
+	}
+	turn := paddingTurn{direction: paddingClientToServer, minLength: 64, maxLength: 64}
+	err := readPaddingTurn(server, turn, 0)
+	var netErr net.Error
+	if !errors.As(err, &netErr) || !netErr.Timeout() {
+		t.Fatalf("error = %v, want network timeout", err)
+	}
+}
+
+func TestValidatePaddingSchedule(t *testing.T) {
+	tests := []struct {
+		name     string
+		schedule []paddingTurn
+		prefix   int
+	}{
+		{name: "empty"},
+		{name: "bad direction", schedule: []paddingTurn{{direction: 99, minLength: 4, maxLength: 4}}},
+		{name: "too small", schedule: []paddingTurn{{direction: paddingClientToServer, minLength: 0, maxLength: 4}}},
+		{name: "reversed range", schedule: []paddingTurn{{direction: paddingClientToServer, minLength: 8, maxLength: 7}}},
+		{name: "wrong first direction", prefix: 3, schedule: []paddingTurn{{direction: paddingServerToClient, minLength: 8, maxLength: 8}}},
+		{name: "prefix leaves no header", prefix: 8, schedule: []paddingTurn{{direction: paddingClientToServer, minLength: 8, maxLength: 8}}},
+		{name: "same direction", schedule: []paddingTurn{{direction: paddingClientToServer, minLength: 8, maxLength: 8}, {direction: paddingClientToServer, minLength: 8, maxLength: 8}}},
+		{name: "range with variants", schedule: []paddingTurn{{direction: paddingClientToServer, minLength: 8, maxLength: 8, variants: []paddingVariant{paddingVariantFromChunks(8)}}}},
+		{name: "empty variant", schedule: []paddingTurn{{direction: paddingClientToServer, variants: []paddingVariant{{}}}}},
+		{name: "bad chunk", schedule: []paddingTurn{{direction: paddingClientToServer, variants: []paddingVariant{paddingVariantFromChunks(maxPaddingChunkLength + 1)}}}},
+		{
+			name: "delay mismatch",
+			schedule: []paddingTurn{{
+				direction: paddingClientToServer,
+				variants: []paddingVariant{{
+					chunks: []int{4, 4},
+					delays: []paddingDelayRange{{min: time.Millisecond, max: time.Millisecond}},
+				}},
+			}},
+		},
+		{name: "reversed start delay", schedule: []paddingTurn{{direction: paddingClientToServer, minLength: 8, maxLength: 8, startDelay: paddingDelayRange{min: 2 * time.Millisecond, max: time.Millisecond}}}},
+		{name: "reversed generated chunk delay", schedule: []paddingTurn{{direction: paddingClientToServer, minLength: 8, maxLength: 8, chunkDelay: paddingDelayRange{min: 2 * time.Millisecond, max: time.Millisecond}}}},
+		{name: "oversized generated chunk", schedule: []paddingTurn{{direction: paddingClientToServer, minLength: 8, maxLength: 8, writeChunkLength: maxPaddingChunkLength + 1}}},
+		{name: "reversed generated chunk range", schedule: []paddingTurn{{direction: paddingClientToServer, minLength: 8, maxLength: 8, writeChunkMinLength: 9, writeChunkLength: 8}}},
+		{name: "variant with generated chunks", schedule: []paddingTurn{{direction: paddingClientToServer, variants: []paddingVariant{paddingVariantFromChunks(8)}, writeChunkLength: 8}}},
+		{name: "send range outside accepted range", schedule: []paddingTurn{{direction: paddingClientToServer, minLength: 8, maxLength: 16, sendMinLength: 7, sendMaxLength: 12}}},
+		{name: "variant with send range", schedule: []paddingTurn{{direction: paddingClientToServer, variants: []paddingVariant{paddingVariantFromChunks(8)}, sendMinLength: 8, sendMaxLength: 8}}},
+		{name: "negative chunk delay", schedule: []paddingTurn{{direction: paddingClientToServer, variants: []paddingVariant{{chunks: []int{8}, delays: []paddingDelayRange{{min: -time.Millisecond}}}}}}},
+		{name: "bad send variant", schedule: []paddingTurn{{direction: paddingClientToServer, variants: []paddingVariant{paddingVariantFromChunks(8)}, sendVariants: []int{1}}}},
+		{name: "prefix splits chunk", prefix: 3, schedule: []paddingTurn{{direction: paddingClientToServer, variants: []paddingVariant{paddingVariantFromChunks(8, 4)}}}},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if err := validatePaddingSchedule(test.schedule, test.prefix); err == nil {
+				t.Fatal("expected invalid padding schedule")
+			}
+		})
+	}
+}
+
+func TestPaddingSchedule2612MatchesCapturedTemplates(t *testing.T) {
+	wantDirections := []paddingDirection{
+		paddingClientToServer,
+		paddingServerToClient,
+		paddingClientToServer,
+		paddingServerToClient,
+		paddingClientToServer,
+		paddingServerToClient,
+	}
+	wantLengths := [][]int{
+		{44},
+		{72},
+		{25},
+		{41172},
+		{2},
+		{7464, 8267, 8790, 8153, 7375, 7347, 8184, 6633, 7670, 8241, 7857, 7254, 8407, 8283, 6804, 8177, 8177, 7929, 8296, 8177},
+	}
+	if len(paddingSchedule2612) != len(wantDirections)+33 {
+		t.Fatalf("padding schedule has %d turns, want %d", len(paddingSchedule2612), len(wantDirections)+33)
+	}
+	for i, turn := range paddingSchedule2612[:len(wantDirections)] {
+		if turn.direction != wantDirections[i] {
+			t.Fatalf("padding turn %d direction = %d, want %d", i, turn.direction, wantDirections[i])
+		}
+		if len(turn.variants) != len(wantLengths[i]) {
+			t.Fatalf("padding turn %d has %d variants, want %d", i, len(turn.variants), len(wantLengths[i]))
+		}
+		for j, variant := range turn.variants {
+			if got := paddingVariantLength(variant); got != wantLengths[i][j] {
+				t.Fatalf("padding turn %d variant %d length = %d, want %d", i, j, got, wantLengths[i][j])
+			}
+		}
+	}
+	wantPlayBounds := [][2]int{
+		{6, 883},
+		{346, 58638},
+		{6, 887},
+		{388, 61077},
+		{2, 50},
+		{575, 65584},
+		{6, 45},
+		{86, 63563},
+		{2, 44},
+		{42, 51983},
+		{2, 851},
+		{309, 25083},
+		{2, 19},
+		{74, 63885},
+		{8, 24},
+		{30, 66128},
+		{2, 19},
+		{26, 35818},
+		{6, 19},
+		{35, 59407},
+		{6, 19},
+		{37, 65328},
+		{2, 19},
+		{26, 60622},
+		{6, 19},
+		{11, 60808},
+		{8, 43},
+		{55, 62027},
+		{2, 19},
+		{427, 65622},
+		{5, 19},
+		{35, 59401},
+		{6, 19},
+	}
+	for i, want := range wantPlayBounds {
+		turn := paddingSchedule2612[len(wantDirections)+i]
+		wantDirection := paddingClientToServer
+		if i%2 == 1 {
+			wantDirection = paddingServerToClient
+		}
+		if turn.direction != wantDirection {
+			t.Fatalf("play turn %d direction = %d, want %d", i, turn.direction, wantDirection)
+		}
+		if turn.minLength != want[0] || turn.maxLength != want[1] {
+			t.Fatalf("play turn %d bounds = %d-%d, want %d-%d", i, turn.minLength, turn.maxLength, want[0], want[1])
+		}
+		if len(turn.variants) != 0 {
+			t.Fatalf("play turn %d unexpectedly has captured variants", i)
+		}
+	}
+	if got := len(paddingSchedule2612[3].variants[0].chunks); got != 30 {
+		t.Fatalf("registry turn chunks = %d, want 30", got)
+	}
+	minimumPlayStart := maxPaddingTurnLength
+	maximumPlayStart := 0
+	for _, variant := range paddingSchedule2612[5].variants {
+		length := paddingVariantLength(variant)
+		minimumPlayStart = min(minimumPlayStart, length)
+		maximumPlayStart = max(maximumPlayStart, length)
+		if variant.chunks[0] != 4941 {
+			t.Fatalf("play start first chunk = %d, want 4941", variant.chunks[0])
+		}
+	}
+	if minimumPlayStart != 6633 || maximumPlayStart != 8790 {
+		t.Fatalf("play start bounds = %d-%d, want 6633-8790", minimumPlayStart, maximumPlayStart)
+	}
+	if err := validatePaddingSchedule(paddingSchedule2612, 2); err != nil {
+		t.Fatalf("captured schedule is invalid: %v", err)
+	}
+
+	serverSchedule, err := newServerPaddingSchedule2612()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err = validatePaddingSchedule(serverSchedule, 2); err != nil {
+		t.Fatalf("server schedule is invalid: %v", err)
+	}
+	for i, branches := range serverPlayBranches2612 {
+		turn := serverSchedule[len(startupPaddingSchedule2612)+1+i*2]
+		got := paddingLengthRange2612{turn.sendMinLength, turn.sendMaxLength}
+		if got != branches.small && got != branches.large {
+			t.Fatalf("server play turn %d send range = %v, want %v or %v", i, got, branches.small, branches.large)
+		}
+	}
+
+	for range 20 {
+		clientSchedule, clientErr := newClientPaddingSchedule2612()
+		if clientErr != nil {
+			t.Fatal(clientErr)
+		}
+		if clientErr = validatePaddingSchedule(clientSchedule, 2); clientErr != nil {
+			t.Fatalf("client schedule is invalid: %v", clientErr)
+		}
+		burstCount := 0
+		for _, burst := range clientPlayBursts2612 {
+			turn := clientSchedule[len(startupPaddingSchedule2612)+burst.playIndex]
+			got := paddingLengthRange2612{turn.sendMinLength, turn.sendMaxLength}
+			switch got {
+			case burst.regular:
+			case burst.burst:
+				burstCount++
+			default:
+				t.Fatalf("client play turn %d send range = %v", burst.playIndex, got)
+			}
+		}
+		if burstCount != 1 {
+			t.Fatalf("client schedule has %d initialization bursts, want 1", burstCount)
+		}
+	}
+
+	for variantIndex := range paddingSchedule2612[3].variants {
+		turn := paddingSchedule2612[3]
+		turn.sendVariants = []int{variantIndex}
+		var encoded bytes.Buffer
+		if err = writePaddingTurnWithSleep(&encoded, turn, 0, func(time.Duration) {}); err != nil {
+			t.Fatal(err)
+		}
+		if err = readPaddingTurn(bytes.NewReader(encoded.Bytes()), paddingSchedule2612[3], 0); err != nil {
+			t.Fatalf("registry variant %d was rejected: %v", variantIndex, err)
+		}
+	}
+}
+
+func TestPaddingVariantPreservesWriteBoundaries(t *testing.T) {
+	tests := []struct {
+		name   string
+		turn   paddingTurn
+		prefix int
+		want   []int
+	}{
+		{name: "login acknowledged turn", turn: paddingSchedule2612[0], prefix: 2, want: []int{26, 16}},
+		{name: "server response turn", turn: paddingSchedule2612[1], want: []int{26, 21, 25}},
+		{name: "single packet turn", turn: paddingSchedule2612[2], want: []int{25}},
+		{name: "fixed registry profile", turn: paddingSchedule2612[3], want: paddingSchedule2612[3].variants[0].chunks},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			var writer recordingWriter
+			if err := writePaddingTurnWithSleep(&writer, test.turn, test.prefix, func(time.Duration) {}); err != nil {
+				t.Fatal(err)
+			}
+			if len(writer.writes) != len(test.want) {
+				t.Fatalf("writes = %v, want %v", writer.writes, test.want)
+			}
+			for i := range test.want {
+				if writer.writes[i] != test.want[i] {
+					t.Fatalf("writes = %v, want %v", writer.writes, test.want)
+				}
+			}
+			if err := readPaddingTurn(bytes.NewReader(writer.Bytes()), test.turn, test.prefix); err != nil {
+				t.Fatal(err)
+			}
+		})
+	}
+}
+
+func TestPaddingVariantAppliesPacing(t *testing.T) {
+	turn := paddingTurn{
+		direction:  paddingClientToServer,
+		startDelay: paddingDelayRange{min: 3 * time.Millisecond, max: 3 * time.Millisecond},
+		variants: []paddingVariant{{
+			chunks: []int{3, 5, 7},
+			delays: []paddingDelayRange{
+				{},
+				{min: 2 * time.Millisecond, max: 2 * time.Millisecond},
+				{min: 4 * time.Millisecond, max: 4 * time.Millisecond},
+			},
+		}},
+	}
+	var slept []time.Duration
+	var writer recordingWriter
+	if err := writePaddingTurnWithSleep(&writer, turn, 3, func(delay time.Duration) {
+		slept = append(slept, delay)
+	}); err != nil {
+		t.Fatal(err)
+	}
+	want := []time.Duration{3 * time.Millisecond, 2 * time.Millisecond, 4 * time.Millisecond}
+	if len(slept) != len(want) {
+		t.Fatalf("delays = %v, want %v", slept, want)
+	}
+	for i := range want {
+		if slept[i] != want[i] {
+			t.Fatalf("delays = %v, want %v", slept, want)
+		}
+	}
+}
+
+func TestGeneratedPaddingChunksApplyPacing(t *testing.T) {
+	turn := paddingTurn{
+		direction:        paddingServerToClient,
+		minLength:        100,
+		maxLength:        100,
+		writeChunkLength: 32,
+		chunkDelay:       paddingDelayRange{min: 2 * time.Millisecond, max: 2 * time.Millisecond},
+	}
+	var slept []time.Duration
+	var writer recordingWriter
+	if err := writePaddingTurnWithSleep(&writer, turn, 0, func(delay time.Duration) {
+		slept = append(slept, delay)
+	}); err != nil {
+		t.Fatal(err)
+	}
+	wantWrites := []int{32, 32, 32, 4}
+	if !slicesEqual(writer.writes, wantWrites) {
+		t.Fatalf("writes = %v, want %v", writer.writes, wantWrites)
+	}
+	wantSleeps := []time.Duration{2 * time.Millisecond, 2 * time.Millisecond, 2 * time.Millisecond}
+	if !slicesEqual(slept, wantSleeps) {
+		t.Fatalf("delays = %v, want %v", slept, wantSleeps)
+	}
+	if err := readPaddingTurn(bytes.NewReader(writer.Bytes()), turn, 0); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestGeneratedPaddingChunkLengthIsRandomized(t *testing.T) {
+	turn := paddingTurn{
+		direction:           paddingServerToClient,
+		minLength:           100,
+		maxLength:           100,
+		writeChunkMinLength: 16,
+		writeChunkLength:    32,
+	}
+	seen := make(map[int]bool)
+	for range 100 {
+		var writer recordingWriter
+		if err := writePaddingTurnWithSleep(&writer, turn, 0, func(time.Duration) {}); err != nil {
+			t.Fatal(err)
+		}
+		firstWrite := writer.writes[0]
+		if firstWrite < turn.writeChunkMinLength || firstWrite > turn.writeChunkLength {
+			t.Fatalf("first write = %d", firstWrite)
+		}
+		seen[firstWrite] = true
+	}
+	if len(seen) < 2 {
+		t.Fatalf("generated write chunk length did not vary: %v", seen)
+	}
+}
+
+func TestPaddingDelayRangeIsRandomized(t *testing.T) {
+	delayRange := millisecondRange(25, 40)
+	seen := make(map[time.Duration]bool)
+	for range 100 {
+		delay, err := randomPaddingDelay(delayRange)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if delay < delayRange.min || delay > delayRange.max {
+			t.Fatalf("delay = %s, want %s-%s", delay, delayRange.min, delayRange.max)
+		}
+		seen[delay] = true
+	}
+	if len(seen) < 2 {
+		t.Fatalf("padding delay did not vary: %v", seen)
+	}
+}
+
+func TestPaddingSchedule2612UsesCoarseTimingBands(t *testing.T) {
+	assertDelayRange(t, "turn 3 to 4", paddingSchedule2612[3].startDelay, 20*time.Millisecond, 50*time.Millisecond)
+	assertDelayRange(t, "turn 5 to 6", paddingSchedule2612[5].startDelay, 35*time.Millisecond, 50*time.Millisecond)
+	assertDelayRange(t, "first play client turn", paddingSchedule2612[6].startDelay, time.Millisecond, 30*time.Millisecond)
+	assertDelayRange(t, "first play server turn", paddingSchedule2612[7].startDelay, time.Millisecond, 45*time.Millisecond)
+	assertDelayRange(t, "play server chunk pacing", paddingSchedule2612[7].chunkDelay, time.Millisecond, 4*time.Millisecond)
+	if paddingSchedule2612[6].writeChunkLength != 1024 {
+		t.Fatalf("play client write chunk = %d, want 1024", paddingSchedule2612[6].writeChunkLength)
+	}
+	if paddingSchedule2612[7].writeChunkLength != maxPaddingChunkLength {
+		t.Fatalf("play server write chunk = %d, want %d", paddingSchedule2612[7].writeChunkLength, maxPaddingChunkLength)
+	}
+	if paddingSchedule2612[7].writeChunkMinLength != 32*1024 {
+		t.Fatalf("play server minimum write chunk = %d, want %d", paddingSchedule2612[7].writeChunkMinLength, 32*1024)
+	}
+
+	for i, variant := range paddingSchedule2612[3].variants {
+		minimum, maximum := paddingVariantDelayBounds(variant)
+		if minimum != 45*time.Millisecond || maximum != 65*time.Millisecond {
+			t.Fatalf("turn 4 variant %d duration = %s-%s, want 45ms-65ms", i, minimum, maximum)
+		}
+	}
+	for i, variant := range paddingSchedule2612[5].variants {
+		minimum, maximum := paddingVariantDelayBounds(variant)
+		if minimum != 10*time.Millisecond || maximum != 25*time.Millisecond {
+			t.Fatalf("turn 6 variant %d duration = %s-%s, want 10ms-25ms", i, minimum, maximum)
+		}
+	}
+}
+
+func assertDelayRange(t *testing.T, name string, got paddingDelayRange, minimum, maximum time.Duration) {
+	t.Helper()
+	if got.min != minimum || got.max != maximum {
+		t.Fatalf("%s delay = %s-%s, want %s-%s", name, got.min, got.max, minimum, maximum)
+	}
+}
+
+func paddingVariantDelayBounds(variant paddingVariant) (time.Duration, time.Duration) {
+	var minimum time.Duration
+	var maximum time.Duration
+	for _, delay := range variant.delays {
+		minimum += delay.min
+		maximum += delay.max
+	}
+	return minimum, maximum
+}
+
+func slicesEqual[T comparable](left, right []T) bool {
+	if len(left) != len(right) {
+		return false
+	}
+	for i := range left {
+		if left[i] != right[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func encodePaddingLength(t *testing.T, length int) []byte {
+	t.Helper()
+	var encoded bytes.Buffer
+	value := Varint(length)
+	if err := value.writeTo(&encoded); err != nil {
+		t.Fatal(err)
+	}
+	return encoded.Bytes()
+}
+
+type oneByteReader struct {
+	reader io.Reader
+}
+
+func (r *oneByteReader) Read(p []byte) (int, error) {
+	if len(p) > 1 {
+		p = p[:1]
+	}
+	return r.reader.Read(p)
+}
+
+type recordingWriter struct {
+	bytes.Buffer
+	writes []int
+}
+
+func (w *recordingWriter) Write(p []byte) (int, error) {
+	w.writes = append(w.writes, len(p))
+	return w.Buffer.Write(p)
+}

transport/internet/finalmask/xmc/profile.go

@@ -0,0 +1,69 @@
+package xmc
+
+import "fmt"
+
+type loginProfile struct {
+	Username          string
+	UUID              UUID
+	TexturesValue     string
+	TexturesSignature string
+}
+
+func profilesFromConfig(configured []*Profile) ([]loginProfile, error) {
+	if len(configured) == 0 {
+		return nil, fmt.Errorf("empty profiles")
+	}
+
+	profiles := make([]loginProfile, 0, len(configured))
+	for _, configuredProfile := range configured {
+		if configuredProfile == nil || configuredProfile.Username == "" {
+			return nil, fmt.Errorf("invalid profile")
+		}
+		if len(configuredProfile.Uuid) != len(UUID{}) {
+			return nil, fmt.Errorf("bad profile UUID length: %d", len(configuredProfile.Uuid))
+		}
+		if configuredProfile.TexturesValue == "" || configuredProfile.TexturesSignature == "" {
+			return nil, fmt.Errorf("incomplete profile textures")
+		}
+
+		profile := loginProfile{
+			Username:          configuredProfile.Username,
+			TexturesValue:     configuredProfile.TexturesValue,
+			TexturesSignature: configuredProfile.TexturesSignature,
+		}
+		copy(profile.UUID[:], configuredProfile.Uuid)
+		profiles = append(profiles, profile)
+	}
+	return profiles, nil
+}
+
+func findProfile(profiles []loginProfile, username string, uuid UUID) (loginProfile, bool) {
+	for _, profile := range profiles {
+		if profile.Username == username && profile.UUID == uuid {
+			return profile, true
+		}
+	}
+	return loginProfile{}, false
+}
+
+func readLoginSuccess(packet *mcPacket) (loginProfile, error) {
+	var (
+		profile       loginProfile
+		username      String
+		propertyCount Varint
+		propertyName  String
+		value         String
+		signed        Boolean
+		signature     String
+	)
+	if err := packet.readFields(&profile.UUID, &username, &propertyCount, &propertyName, &value, &signed, &signature); err != nil {
+		return loginProfile{}, err
+	}
+	if propertyCount != 1 || propertyName != "textures" || !signed {
+		return loginProfile{}, fmt.Errorf("invalid login profile properties")
+	}
+	profile.Username = string(username)
+	profile.TexturesValue = string(value)
+	profile.TexturesSignature = string(signature)
+	return profile, nil
+}

transport/internet/finalmask/xmc/profile_test.go

@@ -0,0 +1,33 @@
+package xmc
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestProfilesFromConfigRejectsEmpty(t *testing.T) {
+	if _, err := profilesFromConfig(nil); err == nil {
+		t.Fatal("expected empty profiles error")
+	}
+}
+
+func TestProfilesFromConfig(t *testing.T) {
+	uuid := bytes.Repeat([]byte{0x2a}, 16)
+	profiles, err := profilesFromConfig([]*Profile{
+		{
+			Username:          "SignedUser",
+			Uuid:              uuid,
+			TexturesValue:     "textures-value",
+			TexturesSignature: "textures-signature",
+		},
+	})
+	if err != nil {
+		t.Fatalf("build explicit profile: %v", err)
+	}
+	if len(profiles) != 1 || profiles[0].Username != "SignedUser" {
+		t.Fatalf("unexpected profile: %+v", profiles)
+	}
+	if profiles[0].TexturesValue != "textures-value" || profiles[0].TexturesSignature != "textures-signature" {
+		t.Fatalf("textures were not preserved: %+v", profiles[0])
+	}
+}

transport/internet/finalmask/xmc/protocol.go

@@ -7,6 +7,11 @@ import (
 	"io"
 )
 
+const (
+	maxPacketDataLength = 32 * 1024
+	maxPacketBodyLength = maxPacketDataLength + 5
+)
+
 type field interface {
 	readFrom(r io.Reader) error
 	writeTo(w io.Writer) error
@@ -18,25 +23,38 @@ type mcPacket struct {
 }
 
 func readPacket(b io.Reader) (*mcPacket, error) {
-	var packetLength Varint
-	err := packetLength.readFrom(b)
+	packet, _, err := readPacketWithLength(b)
+	return packet, err
+}
+
+func readPacketWithLength(b io.Reader) (*mcPacket, int, error) {
+	packetData, wireLength, err := readFrame(b, maxPacketBodyLength)
 	if err != nil {
-		return nil, fmt.Errorf("read packet length: %w", err)
+		return nil, 0, err
+	}
+	packet, err := decodePacketBody(packetData)
+	return packet, wireLength, err
+}
+
+func decodePacketBody(packetData []byte) (*mcPacket, error) {
+	if len(packetData) < 1 || len(packetData) > maxPacketBodyLength {
+		return nil, fmt.Errorf("read packet: bad length: %d", len(packetData))
 	}
 
+	body := bytes.NewReader(packetData)
 	var packetID Varint
-	err = packetID.readFrom(b)
+	err := packetID.readFrom(body)
 	if err != nil {
 		return nil, fmt.Errorf("read packet ID: %w", err)
 	}
 
-	dataLength := int(packetLength) - varintSize(packetID)
-	if dataLength < 0 || dataLength > 1024*32 {
+	dataLength := body.Len()
+	if dataLength > maxPacketDataLength {
 		return nil, fmt.Errorf("read packet: bad length: %d", dataLength)
 	}
 
 	data := make([]byte, dataLength)
-	_, err = io.ReadFull(b, data)
+	_, err = io.ReadFull(body, data)
 	if err != nil {
 		return nil, fmt.Errorf("read packet data: %w", err)
 	}
@@ -47,9 +65,24 @@ func readPacket(b io.Reader) (*mcPacket, error) {
 	}, nil
 }
 
+func readFrame(r io.Reader, maxLength int) ([]byte, int, error) {
+	frameLength, prefixLength, err := readVarintWithLength(r)
+	if err != nil {
+		return nil, 0, fmt.Errorf("read packet length: %w", err)
+	}
+	if frameLength < 1 || int(frameLength) > maxLength {
+		return nil, 0, fmt.Errorf("read packet: bad length: %d", frameLength)
+	}
+
+	frame := make([]byte, int(frameLength))
+	if _, err := io.ReadFull(r, frame); err != nil {
+		return nil, 0, fmt.Errorf("read packet data: %w", err)
+	}
+	return frame, prefixLength + len(frame), nil
+}
+
 func (p *mcPacket) readFields(fields ...field) error {
 	r := bytes.NewReader(p.data)
-
 	for _, field := range fields {
 		err := field.readFrom(r)
 		if err != nil {
@@ -62,47 +95,49 @@ func (p *mcPacket) readFields(fields ...field) error {
 
 type Varint int32
 
+const (
+	SEGMENT_BITS = 0x7F
+	CONTINUE_BIT = 0x80
+)
+
 func (v *Varint) readFrom(r io.Reader) error {
-	SEGMENT_BITS := byte(0x7F)
-	CONTINUE_BIT := byte(0x80)
-
-	var err error
-
-	var value int32 = 0
-	var position int32 = 0
-	var currentByte byte
-
-	for true {
-		currentByte, err = readByte(r)
-		if err != nil {
-			return fmt.Errorf("read varint: %w", err)
-		}
-		value |= int32(currentByte&SEGMENT_BITS) << position
-
-		if (currentByte & CONTINUE_BIT) == 0 {
-			break
-		}
-
-		position += 7
-
-		if position >= 32 {
-			return fmt.Errorf("read varint: too large")
-		}
+	value, _, err := readVarintWithLength(r)
+	if err != nil {
+		return err
 	}
-
-	*v = Varint(value)
-
+	*v = value
 	return nil
 }
 
-func (v *Varint) writeTo(w io.Writer) error {
-	SEGMENT_BITS := byte(0x7F)
-	CONTINUE_BIT := byte(0x80)
+func readVarintWithLength(r io.Reader) (Varint, int, error) {
+	var value int32
+	for index := 0; index < 5; index++ {
+		currentByte, err := readByte(r)
+		if err != nil {
+			return 0, 0, fmt.Errorf("read varint: %w", err)
+		}
+		if index == 4 && currentByte&0xf0 != 0 {
+			return 0, 0, fmt.Errorf("read varint: too large")
+		}
+		value |= int32(currentByte&SEGMENT_BITS) << (7 * index)
 
-	value := int32(*v)
+		if currentByte&CONTINUE_BIT == 0 {
+			parsed := Varint(value)
+			length := index + 1
+			if length != varintSize(parsed) {
+				return 0, 0, fmt.Errorf("read varint: non-canonical encoding")
+			}
+			return parsed, length, nil
+		}
+	}
+	return 0, 0, fmt.Errorf("read varint: too large")
+}
+
+func (v *Varint) writeTo(w io.Writer) error {
+	value := uint32(*v)
 
 	for {
-		currentByte := byte(value & int32(SEGMENT_BITS))
+		currentByte := byte(value & SEGMENT_BITS)
 		value >>= 7
 		if value != 0 {
 			currentByte |= CONTINUE_BIT
@@ -122,11 +157,12 @@ func (v *Varint) writeTo(w io.Writer) error {
 }
 
 func varintSize(value Varint) int {
+	uintValue := uint32(value)
 	size := 0
-	for {
+	for range 5 {
 		size++
-		value >>= 7
-		if value == 0 {
+		uintValue >>= 7
+		if uintValue == 0 {
 			break
 		}
 	}
@@ -238,6 +274,31 @@ func (v *UUID) readFrom(r io.Reader) error {
 	return nil
 }
 
+type Boolean bool
+
+func (v *Boolean) readFrom(r io.Reader) error {
+	b, err := readByte(r)
+	if err != nil {
+		return fmt.Errorf("read boolean: %w", err)
+	}
+	if b > 1 {
+		return fmt.Errorf("read boolean: invalid value: %d", b)
+	}
+	*v = b == 1
+	return nil
+}
+
+func (v *Boolean) writeTo(w io.Writer) error {
+	value := byte(0)
+	if *v {
+		value = 1
+	}
+	if _, err := w.Write([]byte{value}); err != nil {
+		return fmt.Errorf("write boolean: %w", err)
+	}
+	return nil
+}
+
 func (v *UUID) writeTo(w io.Writer) error {
 	_, err := w.Write(v[:])
 	if err != nil {
@@ -256,7 +317,7 @@ func (v *Bytes) readFrom(r io.Reader) error {
 	}
 
 	if length < 0 || length >= 1024 {
-		return fmt.Errorf("read bytes: invalid size: %d", err)
+		return fmt.Errorf("read bytes: invalid size: %d", length)
 	}
 
 	buf := make([]byte, length)
@@ -271,6 +332,24 @@ func (v *Bytes) readFrom(r io.Reader) error {
 	return nil
 }
 
+type RestBytes []byte
+
+func (v *RestBytes) readFrom(r io.Reader) error {
+	buf, err := io.ReadAll(r)
+	if err != nil {
+		return fmt.Errorf("read remaining bytes: %w", err)
+	}
+	*v = append((*v)[:0], buf...)
+	return nil
+}
+
+func (v *RestBytes) writeTo(w io.Writer) error {
+	if _, err := w.Write(*v); err != nil {
+		return fmt.Errorf("write remaining bytes: %w", err)
+	}
+	return nil
+}
+
 func (v *Bytes) writeTo(w io.Writer) error {
 	length := Varint(len(*v))
 	err := length.writeTo(w)
@@ -297,36 +376,66 @@ func readByte(r io.Reader) (byte, error) {
 }
 
 func writePacket(w io.Writer, packetID int, fields ...field) error {
+	_, err := writePacketWithLength(w, packetID, fields...)
+	return err
+}
+
+func writePacketWithLength(w io.Writer, packetID int, fields ...field) (int, error) {
+	frame, err := encodePacket(packetID, fields...)
+	if err != nil {
+		return 0, err
+	}
+	if err = writeFull(w, frame); err != nil {
+		return 0, fmt.Errorf("write packet data: %w", err)
+	}
+	return len(frame), nil
+}
+
+func encodePacket(packetID int, fields ...field) ([]byte, error) {
 	var dataBuf bytes.Buffer
 
 	for _, field := range fields {
 		err := field.writeTo(&dataBuf)
 		if err != nil {
-			return fmt.Errorf("write packet field: %w", err)
+			return nil, fmt.Errorf("write packet field: %w", err)
 		}
 	}
-
-	var buf bytes.Buffer
-
-	var packetLength Varint = Varint(varintSize(Varint(packetID)) + dataBuf.Len())
-	err := packetLength.writeTo(&buf)
-	if err != nil {
-		return fmt.Errorf("write packet length: %w", err)
+	if dataBuf.Len() > maxPacketDataLength {
+		return nil, fmt.Errorf("write packet: bad length: %d", dataBuf.Len())
 	}
 
-	var packetIDVarint Varint = Varint(packetID)
-	err = packetIDVarint.writeTo(&buf)
-	if err != nil {
-		return fmt.Errorf("write packet ID: %w", err)
+	packetIDVarint := Varint(packetID)
+	bodyLength := varintSize(packetIDVarint) + dataBuf.Len()
+	if bodyLength > maxPacketBodyLength {
+		return nil, fmt.Errorf("write packet: bad length: %d", bodyLength)
 	}
 
-	buf.Write(dataBuf.Bytes())
-
-	_, err = w.Write(buf.Bytes())
-	if err != nil {
-		return fmt.Errorf("write packet data: %w", err)
+	var frame bytes.Buffer
+	frame.Grow(varintSize(Varint(bodyLength)) + bodyLength)
+	frameLength := Varint(bodyLength)
+	if err := frameLength.writeTo(&frame); err != nil {
+		return nil, fmt.Errorf("write packet length: %w", err)
 	}
+	if err := packetIDVarint.writeTo(&frame); err != nil {
+		return nil, fmt.Errorf("write packet ID: %w", err)
+	}
+	frame.Write(dataBuf.Bytes())
+	return frame.Bytes(), nil
+}
 
+func writeFull(w io.Writer, p []byte) error {
+	for len(p) > 0 {
+		n, err := w.Write(p)
+		if n > 0 {
+			p = p[n:]
+		}
+		if err != nil {
+			return err
+		}
+		if n == 0 {
+			return io.ErrShortWrite
+		}
+	}
 	return nil
 }
 

transport/internet/finalmask/xmc/protocol_test.go

@@ -0,0 +1,56 @@
+package xmc
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestReadPacketDoesNotConsumeFollowingPacket(t *testing.T) {
+	data := []byte{0x01, 0x80, 0x01, 0x00}
+	r := bytes.NewReader(data)
+	if _, err := readPacket(r); err == nil {
+		t.Fatal("expected truncated packet ID to fail")
+	}
+	pkt, err := readPacket(r)
+	if err != nil {
+		t.Fatalf("read following packet: %v", err)
+	}
+	if pkt.packetID != 0 {
+		t.Fatalf("packet ID = %d", pkt.packetID)
+	}
+}
+
+func TestPacketWithLengthReportsWireBytes(t *testing.T) {
+	var wire bytes.Buffer
+	written, err := writePacketWithLength(&wire, 0x03)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if written != 2 || !bytes.Equal(wire.Bytes(), []byte{0x01, 0x03}) {
+		t.Fatalf("wire = %x, length = %d", wire.Bytes(), written)
+	}
+
+	packet, read, err := readPacketWithLength(bytes.NewReader(wire.Bytes()))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if packet.packetID != 0x03 || read != written {
+		t.Fatalf("packet ID = %d, read = %d, written = %d", packet.packetID, read, written)
+	}
+}
+
+func TestReadPacketRejectsNonCanonicalLengthVarint(t *testing.T) {
+	_, _, err := readPacketWithLength(bytes.NewReader([]byte{0x81, 0x00, 0x03}))
+	if err == nil || !strings.Contains(err.Error(), "non-canonical") {
+		t.Fatalf("error = %v", err)
+	}
+}
+
+func TestVarintRejectsOversizedFifthByte(t *testing.T) {
+	var value Varint
+	err := value.readFrom(bytes.NewReader([]byte{0xff, 0xff, 0xff, 0xff, 0x1f}))
+	if err == nil || !strings.Contains(err.Error(), "too large") {
+		t.Fatalf("error = %v", err)
+	}
+}

transport/internet/finalmask/xmc/server.go

@@ -31,10 +31,16 @@ type serverConn struct {
 
 	state serverState
 
-	handshakeLock sync.Mutex
-	password      string
-	rsaPrivateKey *rsa.PrivateKey
-	rsaPublicKey  []byte
+	handshakeLock   sync.Mutex
+	lifecycleMu     sync.Mutex
+	closed          bool
+	profiles        []loginProfile
+	password        string
+	rsaPrivateKey   *rsa.PrivateKey
+	rsaPublicKey    []byte
+	paddingSchedule []paddingTurn
+	packet          *packetStream
+	deadlines       *connectionDeadlines
 }
 
 func (c *serverConn) handshake() error {
@@ -45,12 +51,10 @@ func (c *serverConn) handshake() error {
 		return nil
 	}
 
-	// handshake timeout
-	err := c.c.SetDeadline(time.Now().Add(time.Second * 30))
-	if err != nil {
+	if err := c.deadlines.beginHandshake(); err != nil {
 		return fmt.Errorf("set deadline: %w", err)
 	}
-	defer c.c.SetDeadline(time.Time{})
+	defer func() { _ = c.deadlines.endHandshake() }()
 
 	var (
 		protocolVersion Varint
@@ -138,17 +142,20 @@ func (c *serverConn) handshake() error {
 		if err != nil {
 			return fmt.Errorf("read login start packet: %w", err)
 		}
+		profile, found := findProfile(c.profiles, string(username), uuid)
 
 		// encrypt request
 
 		var (
-			serverId           String = String("")
-			publicKey          Bytes  = Bytes(c.rsaPublicKey)
-			verifyToken        Bytes  = Bytes(make([]byte, 4))
-			shouldAuthenticate Varint = Varint(1)
+			serverId           String  = String("")
+			publicKey          Bytes   = Bytes(c.rsaPublicKey)
+			verifyToken        Bytes   = Bytes(make([]byte, 4))
+			shouldAuthenticate Boolean = true
 		)
 
-		rand.Read(verifyToken)
+		if _, err = rand.Read(verifyToken); err != nil {
+			return fmt.Errorf("generate verify token: %w", err)
+		}
 
 		err = writePacket(c.writer, 0x01, &serverId, &publicKey, &verifyToken, &shouldAuthenticate)
 		if err != nil {
@@ -183,6 +190,9 @@ func (c *serverConn) handshake() error {
 		if err != nil {
 			return fmt.Errorf("decrypt shared secret: %w", err)
 		}
+		if len(sharedSecret) != 16 {
+			return fmt.Errorf("bad shared secret length: %d", len(sharedSecret))
+		}
 
 		decryptedVerifyToken, err = rsa.DecryptPKCS1v15(rand.Reader, c.rsaPrivateKey, encryptedVerifyToken)
 		if err != nil {
@@ -210,8 +220,47 @@ func (c *serverConn) handshake() error {
 			writeDisconnectPacket(c.writer, `{"type":"translatable","translate":"multiplayer.disconnect.authservers_down"}`)
 			return fmt.Errorf("bad password")
 		}
+		if !found {
+			if err = writeDisconnectPacket(c.writer, `{"text":"You are not white-listed on this server!"}`); err != nil {
+				return fmt.Errorf("write unknown login profile disconnect: %w", err)
+			}
+			return fmt.Errorf("unknown login profile")
+		}
 
+		loginName := String(profile.Username)
+		propertyCount := Varint(1)
+		propertyName := String("textures")
+		texturesValue := String(profile.TexturesValue)
+		signed := Boolean(true)
+		texturesSignature := String(profile.TexturesSignature)
+		if err = writePacket(c.writer, 0x02, &profile.UUID, &loginName, &propertyCount, &propertyName, &texturesValue, &signed, &texturesSignature); err != nil {
+			return fmt.Errorf("write login finished: %w", err)
+		}
+
+		var loginAcknowledgedLength int
+		pkt, loginAcknowledgedLength, err = readPacketWithLength(c.reader)
+		if err != nil {
+			return fmt.Errorf("read login acknowledged: %w", err)
+		}
+		if err = validateLoginAcknowledgedPacket(pkt); err != nil {
+			return err
+		}
+		if err = runPaddingSchedule(c.reader, c.writer, false, loginAcknowledgedLength, c.paddingSchedule); err != nil {
+			return fmt.Errorf("run startup padding: %w", err)
+		}
+
+		packet := newPacketStream(c.reader, c.writer, false)
+		c.lifecycleMu.Lock()
+		if c.closed {
+			c.lifecycleMu.Unlock()
+			packet.Stop()
+			return net.ErrClosed
+		}
+		c.packet = packet
+		c.reader = packet
+		c.writer = packet
 		c.state = serverStateProxy
+		c.lifecycleMu.Unlock()
 
 		return nil
 
@@ -220,6 +269,16 @@ func (c *serverConn) handshake() error {
 	}
 }
 
+func validateLoginAcknowledgedPacket(pkt *mcPacket) error {
+	if pkt.packetID != 0x03 {
+		return fmt.Errorf("bad login acknowledged packet id: %d", pkt.packetID)
+	}
+	if len(pkt.data) != 0 {
+		return fmt.Errorf("bad login acknowledged packet data length: %d", len(pkt.data))
+	}
+	return nil
+}
+
 func (c *serverConn) Read(b []byte) (int, error) {
 	err := c.handshake()
 	if err != nil {
@@ -239,6 +298,13 @@ func (c *serverConn) Write(b []byte) (int, error) {
 }
 
 func (c *serverConn) Close() error {
+	c.lifecycleMu.Lock()
+	c.closed = true
+	packet := c.packet
+	c.lifecycleMu.Unlock()
+	if packet != nil {
+		packet.Stop()
+	}
 	return c.c.Close()
 }
 
@@ -251,38 +317,47 @@ func (c *serverConn) RemoteAddr() net.Addr {
 }
 
 func (c *serverConn) SetDeadline(t time.Time) error {
-	return c.c.SetDeadline(t)
+	return c.deadlines.setDeadline(t)
 }
 
 func (c *serverConn) SetReadDeadline(t time.Time) error {
-	return c.c.SetReadDeadline(t)
+	return c.deadlines.setReadDeadline(t)
 }
 
 func (c *serverConn) SetWriteDeadline(t time.Time) error {
-	return c.c.SetWriteDeadline(t)
+	return c.deadlines.setWriteDeadline(t)
 }
 
-func wrapConnServer(c net.Conn, password string, rsaPrivateKeyDER []byte, rsaPublicKey []byte) (*serverConn, error) {
+func wrapConnServer(c net.Conn, profiles []loginProfile, password string, rsaPrivateKeyDER []byte, rsaPublicKey []byte) (*serverConn, error) {
+	if len(profiles) == 0 {
+		return nil, fmt.Errorf("empty profiles")
+	}
 	if len(rsaPrivateKeyDER) == 0 {
 		return nil, fmt.Errorf("empty rsa private key")
 	}
 	if len(rsaPublicKey) == 0 {
 		return nil, fmt.Errorf("empty rsa public key")
 	}
-
 	rsaPrivateKey, err := x509.ParsePKCS1PrivateKey(rsaPrivateKeyDER)
 	if err != nil {
 		return nil, fmt.Errorf("parse rsa private key: %w", err)
 	}
+	paddingSchedule, err := newServerPaddingSchedule2612()
+	if err != nil {
+		return nil, fmt.Errorf("select padding profile: %w", err)
+	}
 
 	s := &serverConn{
-		reader:        bufio.NewReader(c),
-		writer:        c,
-		c:             c,
-		state:         serverStateHandshake,
-		password:      password,
-		rsaPrivateKey: rsaPrivateKey,
-		rsaPublicKey:  rsaPublicKey,
+		reader:          bufio.NewReader(c),
+		writer:          c,
+		c:               c,
+		state:           serverStateHandshake,
+		profiles:        profiles,
+		password:        password,
+		rsaPrivateKey:   rsaPrivateKey,
+		rsaPublicKey:    rsaPublicKey,
+		paddingSchedule: paddingSchedule,
+		deadlines:       newConnectionDeadlines(c),
 	}
 
 	return s, nil

transport/internet/finalmask/xmc/stream.go

@@ -6,12 +6,14 @@ import (
 	"crypto/cipher"
 	"fmt"
 	"io"
+	"sync"
 )
 
 type cryptoStream struct {
 	stream cipher.Stream
 	r      io.Reader
 	w      io.Writer
+	mu     sync.Mutex
 }
 
 func newCryptoReader(r io.Reader, sharedSecret []byte) (*cryptoStream, error) {
@@ -30,12 +32,19 @@ func (c *cryptoStream) Read(b []byte) (int, error) {
 		panic("read on a write-only crypto stream")
 	}
 
-	n, err := c.r.Read(b)
-	if err != nil {
-		return 0, fmt.Errorf("crypto reader: read: %w", err)
-	}
+	c.mu.Lock()
+	defer c.mu.Unlock()
 
-	c.stream.XORKeyStream(b[:n], b[:n])
+	n, err := c.r.Read(b)
+	if n > 0 {
+		c.stream.XORKeyStream(b[:n], b[:n])
+	}
+	if err != nil {
+		if err == io.EOF {
+			return n, io.EOF
+		}
+		return n, fmt.Errorf("crypto reader: read: %w", err)
+	}
 
 	return n, nil
 }
@@ -56,13 +65,15 @@ func (c *cryptoStream) Write(b []byte) (int, error) {
 		panic("write on a read-only crypto stream")
 	}
 
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
 	encrypted := make([]byte, len(b))
 	c.stream.XORKeyStream(encrypted, b)
 
-	n, err := c.w.Write(encrypted)
-	if err != nil {
+	if err := writeFull(c.w, encrypted); err != nil {
 		return 0, fmt.Errorf("crypto writer: write: %w", err)
 	}
 
-	return n, nil
+	return len(b), nil
 }

transport/internet/finalmask/xmc/stream_test.go

@@ -0,0 +1,81 @@
+package xmc
+
+import (
+	"bytes"
+	"io"
+	"testing"
+)
+
+type dataAndEOFReader struct {
+	data []byte
+}
+
+func (r *dataAndEOFReader) Read(p []byte) (int, error) {
+	if len(r.data) == 0 {
+		return 0, io.EOF
+	}
+	n := copy(p, r.data)
+	r.data = r.data[n:]
+	return n, io.EOF
+}
+
+type shortWriter struct {
+	bytes.Buffer
+}
+
+func (w *shortWriter) Write(p []byte) (int, error) {
+	if len(p) > 1 {
+		p = p[:len(p)/2]
+	}
+	return w.Buffer.Write(p)
+}
+
+func TestCryptoReaderPreservesDataReturnedWithEOF(t *testing.T) {
+	secret := []byte("0123456789abcdef")
+	plaintext := []byte("payload returned with EOF")
+	var encrypted bytes.Buffer
+	writer, err := newCryptoWriter(&encrypted, secret)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err = writer.Write(plaintext); err != nil {
+		t.Fatal(err)
+	}
+
+	reader, err := newCryptoReader(&dataAndEOFReader{data: encrypted.Bytes()}, secret)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := make([]byte, len(plaintext))
+	n, err := reader.Read(got)
+	if err == nil || n != len(plaintext) {
+		t.Fatalf("Read = %d, %v", n, err)
+	}
+	if !bytes.Equal(got[:n], plaintext) {
+		t.Fatalf("plaintext = %q", got[:n])
+	}
+}
+
+func TestCryptoWriterHandlesShortWrites(t *testing.T) {
+	secret := []byte("0123456789abcdef")
+	plaintext := bytes.Repeat([]byte("short-write"), 100)
+	var dst shortWriter
+	writer, err := newCryptoWriter(&dst, secret)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n, err := writer.Write(plaintext); err != nil || n != len(plaintext) {
+		t.Fatalf("Write = %d, %v", n, err)
+	}
+	reader, err := newCryptoReader(bytes.NewReader(dst.Bytes()), secret)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err := io.ReadAll(reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(got, plaintext) {
+		t.Fatal("decrypted payload mismatch")
+	}
+}

transport/internet/grpc/encoding/hunkconn.go

@@ -38,12 +38,14 @@ func NewHunkReadWriter(hc HunkConn, cancel context.CancelFunc) *HunkReaderWriter
 
 func NewHunkConn(hc HunkConn, cancel context.CancelFunc, trustedXForwardedFor []string) net.Conn {
 	rAddr := remoteAddrFromContext(hc.Context(), trustedXForwardedFor)
+	lAddr := localAddrFromContext(hc.Context())
 	wrc := NewHunkReadWriter(hc, cancel)
 	return cnc.NewConnection(
 		cnc.ConnectionInput(wrc),
 		cnc.ConnectionOutput(wrc),
 		cnc.ConnectionOnClose(wrc),
 		cnc.ConnectionRemoteAddr(rAddr),
+		cnc.ConnectionLocalAddr(lAddr),
 	)
 }
 

transport/internet/grpc/encoding/multiconn.go

@@ -33,12 +33,14 @@ func NewMultiHunkReadWriter(hc MultiHunkConn, cancel context.CancelFunc) *MultiH
 
 func NewMultiHunkConn(hc MultiHunkConn, cancel context.CancelFunc, trustedXForwardedFor []string) net.Conn {
 	rAddr := remoteAddrFromContext(hc.Context(), trustedXForwardedFor)
+	lAddr := localAddrFromContext(hc.Context())
 	wrc := NewMultiHunkReadWriter(hc, cancel)
 	return cnc.NewConnection(
 		cnc.ConnectionInputMulti(wrc),
 		cnc.ConnectionOutputMulti(wrc),
 		cnc.ConnectionOnClose(wrc),
 		cnc.ConnectionRemoteAddr(rAddr),
+		cnc.ConnectionLocalAddr(lAddr),
 	)
 }
 

transport/internet/grpc/encoding/remoteaddr.go

@@ -56,3 +56,17 @@ func parseTrustedXForwardedFor(md metadata.MD, trusted []string, remoteAddr net.
 	}
 	return nil
 }
+
+func localAddrFromContext(ctx context.Context) net.Addr {
+	var localAddr net.Addr
+	if pr, ok := peer.FromContext(ctx); ok {
+		localAddr = pr.LocalAddr
+	}
+	if localAddr == nil {
+		localAddr = &net.TCPAddr{
+			IP:   []byte{0, 0, 0, 0},
+			Port: 0,
+		}
+	}
+	return localAddr
+}

transport/internet/splithttp/hub.go

@@ -373,11 +373,15 @@ func (h *requestHandler) ServeHTTP(writer http.ResponseWriter, request *http.Req
 			Reader:         request.Body,
 			ResponseWriter: writer,
 		}
+		localAddr := h.localAddr
+		if la, ok := request.Context().Value(http.LocalAddrContextKey).(net.Addr); ok && la != nil {
+			localAddr = la
+		}
 		conn := splitConn{
 			writer:     httpSC,
 			reader:     httpSC,
 			remoteAddr: remoteAddr,
-			localAddr:  h.localAddr,
+			localAddr:  localAddr,
 		}
 		if sessionId != "" { // if not stream-one
 			conn.reader = currentSession.uploadQueue