Merge b167850cef into 345c76f9a8

infra/conf/transport_internet.go

@@ -2,9 +2,11 @@ package conf
 
 import (
 	"context"
+	"crypto/x509"
 	"encoding/base64"
 	"encoding/hex"
 	"encoding/json"
+	"fmt"
 	"math"
 	"math/big"
 	"net/netip"
@@ -24,6 +26,7 @@ import (
 	"github.com/xtls/xray-core/transport/internet"
 	"github.com/xtls/xray-core/transport/internet/finalmask/fragment"
 	"github.com/xtls/xray-core/transport/internet/finalmask/header/custom"
+	"github.com/xtls/xray-core/transport/internet/finalmask/minecraft"
 	"github.com/xtls/xray-core/transport/internet/finalmask/mkcp/aes128gcm"
 	"github.com/xtls/xray-core/transport/internet/finalmask/mkcp/header"
 	"github.com/xtls/xray-core/transport/internet/finalmask/mkcp/original"
@@ -1248,6 +1251,7 @@ var (
 		"header-custom": func() interface{} { return new(HeaderCustomTCP) },
 		"fragment":      func() interface{} { return new(FragmentMask) },
 		"sudoku":        func() interface{} { return new(Sudoku) },
+		"minecraft":     func() interface{} { return new(Minecraft) },
 	}, "type", "settings")
 
 	udpmaskLoader = NewJSONConfigLoader(ConfigCreatorCache{
@@ -1468,6 +1472,40 @@ func (c *FragmentMask) Build() (proto.Message, error) {
 	return config, nil
 }
 
+type Minecraft struct {
+	Hostname  string   `json:"hostname"`
+	Usernames []string `json:"usernames"`
+	Password  string   `json:"password"`
+}
+
+func (c *Minecraft) Build() (proto.Message, error) {
+	if len(c.Usernames) == 0 {
+		c.Usernames = []string{"Dream"}
+	}
+
+	if c.Password == "" {
+		return nil, fmt.Errorf("empty password")
+	}
+
+	rsaPrivateKey, err := minecraft.DeriveRSAKey(c.Password)
+	if err != nil {
+		return nil, fmt.Errorf("derive minecraft rsa key: %w", err)
+	}
+
+	rsaPublicKey, err := x509.MarshalPKIXPublicKey(&rsaPrivateKey.PublicKey)
+	if err != nil {
+		return nil, fmt.Errorf("marshal minecraft rsa public key: %w", err)
+	}
+
+	return &minecraft.Config{
+		Password:      c.Password,
+		Usernames:     c.Usernames,
+		Hostname:      c.Hostname,
+		RsaPrivateKey: x509.MarshalPKCS1PrivateKey(rsaPrivateKey),
+		RsaPublicKey:  rsaPublicKey,
+	}, nil
+}
+
 type NoiseItem struct {
 	Rand      Int32Range      `json:"rand"`
 	RandRange *Int32Range     `json:"randRange"`

transport/internet/finalmask/minecraft/cfb8.go

@@ -0,0 +1,138 @@
+package minecraft
+
+// Copied from https://github.com/Tnze/go-mc/blob/539b4a3a7f030332eb58b8a946116ae7907630d2/net/CFB8/cfb8.go
+
+import (
+	"crypto/cipher"
+	"crypto/subtle"
+	"unsafe"
+)
+
+type cfb8 struct {
+	c         cipher.Block
+	blockSize int
+	ivPos     int
+	iv        []byte
+	de        bool
+}
+
+func newCFB8Decrypt(c cipher.Block, iv []byte) *cfb8 {
+	return newCFB8(c, iv, true)
+}
+
+func newCFB8Encrypt(c cipher.Block, iv []byte) *cfb8 {
+	return newCFB8(c, iv, false)
+}
+
+func newCFB8(c cipher.Block, iv []byte, de bool) *cfb8 {
+	cp := make([]byte, len(iv)*3)
+	copy(cp, iv)
+	return &cfb8{
+		c:         c,
+		blockSize: c.BlockSize(),
+		iv:        cp,
+		de:        de,
+	}
+}
+
+func (cf *cfb8) XORKeyStream(dst, src []byte) {
+	if len(src) == 0 {
+		return
+	}
+	if len(dst) < len(src) {
+		panic("cfb8: output smaller than input")
+	}
+
+	// If dst and src does not overlap in first block size,
+	// and the length of src is greater than 2*blockSize,
+	// we can use an optimized implementation.
+	if len(src) > cf.blockSize<<1 &&
+		(uintptr(unsafe.Pointer(&dst[0]))+uintptr(cf.blockSize) <= uintptr(unsafe.Pointer(&src[0])) ||
+			uintptr(unsafe.Pointer(&src[0]))+uintptr(len(src)) <= uintptr(unsafe.Pointer(&dst[0]))) {
+		// encrypt/decrypt first blockSize bytes
+		// After this, the IV will come to the same as
+		// the last blockSize of ciphertext, so
+		// we can reuse them without copy.
+		cf.xorKeyStream(dst, src[:cf.blockSize])
+		var ciphertext []byte
+		if cf.de {
+			ciphertext = src
+		} else {
+			ciphertext = dst
+		}
+		dst = dst[cf.blockSize:]
+		src = src[cf.blockSize:]
+		iv := cf.iv
+		_ = iv[0] // bounds check hint to compiler; see golang.org/issue/14808
+		var (
+			i   int
+			val byte
+		)
+		dst = dst[:len(src)]
+		if cf.de && // and requires to be non-overlapping at all
+			uintptr(unsafe.Pointer(&dst[0])) <= uintptr(unsafe.Pointer(&src[len(src)-1])) &&
+			uintptr(unsafe.Pointer(&src[0])) <= uintptr(unsafe.Pointer(&dst[len(dst)-1])) {
+			for i = 0; i < len(src)-cf.blockSize; i += 1 {
+				cf.c.Encrypt(dst[i:], ciphertext[i:])
+			}
+			subtle.XORBytes(dst, src[:i], dst)
+			for ; i < len(src); i += 1 {
+				cf.c.Encrypt(iv, ciphertext[i:])
+				dst[i] = src[i] ^ iv[0]
+			}
+		} else {
+			_ = ciphertext[len(src)]
+			for i, val = range src {
+				cf.c.Encrypt(iv, ciphertext[i:])
+				dst[i] = val ^ iv[0]
+			}
+			// for-range does not increase i in the last loop,
+			// compared to the classic for clause
+			i += 1
+		}
+		// copy the current IV for next operation
+		copy(iv, ciphertext[i:i+cf.blockSize])
+		cf.ivPos = 0
+		return
+	}
+
+	cf.xorKeyStream(dst, src)
+}
+
+func (cf *cfb8) xorKeyStream(dst, src []byte) {
+	dst = dst[:len(src)] // remove bounds check in loop
+	for i, val := range src {
+		posPlusBlockSize := cf.ivPos + cf.blockSize
+		// fast mod; 2*blockSize must be a non-negative integer power of 2
+		tempPos := posPlusBlockSize & (cf.blockSize<<1 - 1)
+		// reuse space to store encrypted block
+		cf.c.Encrypt(cf.iv[tempPos:], cf.iv[cf.ivPos:])
+		// Only the first byte of the encrypted block is used
+		// for encryption/decryption, other bytes are ignored.
+		val ^= cf.iv[tempPos]
+
+		if cf.ivPos == cf.blockSize<<1 {
+			// bound reached; move to next round for next operation
+			// copy next block to the start of the ring buffer
+			copy(cf.iv, cf.iv[cf.ivPos+1:])
+			// insert the encrypted byte to the end of IV
+			if cf.de {
+				cf.iv[cf.blockSize-1] = src[i]
+			} else {
+				cf.iv[cf.blockSize-1] = val
+			}
+			cf.ivPos = 0
+		} else {
+			// insert the encrypted byte to the end of IV
+			if cf.de {
+				cf.iv[posPlusBlockSize] = src[i]
+			} else {
+				cf.iv[posPlusBlockSize] = val
+			}
+			// move to next block
+			cf.ivPos += 1
+		}
+
+		dst[i] = val
+	}
+}

transport/internet/finalmask/minecraft/client.go

@@ -0,0 +1,236 @@
+package minecraft
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	"crypto/x509"
+	"fmt"
+	"io"
+	"math/big"
+	"net"
+	"strconv"
+	"sync"
+	"time"
+)
+
+type clientConn struct {
+	reader io.Reader
+	writer io.Writer
+	c      net.Conn
+
+	state clientState
+
+	handshakeLock sync.Mutex
+	usernames     []string
+	password      string
+	rsaPublicKey  []byte
+	hostname      string
+}
+
+type clientState int
+
+var (
+	clientStateHandshake clientState = 1
+	clientStateProxy     clientState = 2
+)
+
+func newClientConn(c net.Conn, usernames []string, password string, rsaPublicKey []byte, hostname string) (*clientConn, error) {
+	if len(rsaPublicKey) == 0 {
+		return nil, fmt.Errorf("empty rsa public key")
+	}
+
+	return &clientConn{
+		reader:        bufio.NewReader(c),
+		writer:        c,
+		c:             c,
+		state:         clientStateHandshake,
+		handshakeLock: sync.Mutex{},
+		usernames:     usernames,
+		password:      password,
+		rsaPublicKey:  rsaPublicKey,
+		hostname:      hostname,
+	}, nil
+}
+
+func (c *clientConn) handshake() error {
+	c.handshakeLock.Lock()
+	defer c.handshakeLock.Unlock()
+
+	if c.state != clientStateHandshake {
+		return nil
+	}
+
+	// Handshake timeout
+	err := c.c.SetDeadline(time.Now().Add(time.Second * 30))
+	if err != nil {
+		return fmt.Errorf("set deadline: %w", err)
+	}
+	defer c.c.SetDeadline(time.Time{})
+
+	var (
+		protocolVersion Varint        = Varint(775)
+		serverAddress   String        = String(c.hostname)
+		serverPort      UnsignedShort = UnsignedShort(25565)
+		nextState       Varint        = Varint(2)
+	)
+
+	host, portString, err := net.SplitHostPort(c.c.RemoteAddr().String())
+	if err == nil {
+		port, err := strconv.Atoi(portString)
+		if err == nil {
+			serverPort = UnsignedShort(port)
+		}
+
+		if serverAddress == "" {
+			serverAddress = String(host)
+		}
+	}
+
+	err = writePacket(c.writer, 0x00, &protocolVersion, &serverAddress, &serverPort, &nextState)
+	if err != nil {
+		return fmt.Errorf("write handshake packet: %w", err)
+	}
+
+	// Login Start
+	var (
+		username    string
+		offlineUUID UUID
+	)
+
+	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)
+	if err != nil {
+		return fmt.Errorf("write login start: %w", err)
+	}
+
+	// Encryption Request
+	pkt, err := readPacket(c.reader)
+	if err != nil {
+		return fmt.Errorf("read encryption request: %w", err)
+	}
+
+	if pkt.packetID != 0x01 {
+		return fmt.Errorf("bad encrypt request packet id")
+	}
+
+	var (
+		serverId    String
+		publicKey   Bytes
+		verifyToken Bytes
+	)
+
+	err = pkt.readFields(&serverId, &publicKey, &verifyToken)
+	if err != nil {
+		return fmt.Errorf("read encryption request fields: %w", err)
+	}
+
+	if !bytes.Equal(publicKey, c.rsaPublicKey) {
+		return fmt.Errorf("server public key mismatch")
+	}
+
+	k, err := x509.ParsePKIXPublicKey(publicKey)
+	if err != nil {
+		return fmt.Errorf("parse server public key: %w", err)
+	}
+
+	rsaPublicKey, ok := k.(*rsa.PublicKey)
+	if !ok {
+		return fmt.Errorf("parse server public key: not rsa")
+	}
+
+	sharedSecret := make([]byte, 16)
+	rand.Read(sharedSecret)
+
+	encryptedSharedSecret, err := rsa.EncryptPKCS1v15(rand.Reader, rsaPublicKey, sharedSecret)
+	if err != nil {
+		return fmt.Errorf("encrypt shared secret: %w", err)
+	}
+
+	verifyToken = append(verifyToken, []byte(c.password)...) // append pre-shared password
+
+	encryptedVerifyToken, err := rsa.EncryptPKCS1v15(rand.Reader, rsaPublicKey, verifyToken)
+	if err != nil {
+		return fmt.Errorf("encrypt verify token: %w", err)
+	}
+
+	// Send Encryption Response
+	err = writePacket(
+		c.writer,
+		0x01,
+		(*Bytes)(&encryptedSharedSecret),
+		(*Bytes)(&encryptedVerifyToken),
+	)
+	if err != nil {
+		return fmt.Errorf("write encryption response: %w", err)
+	}
+
+	// Enable encryption
+	c.reader, err = newCryptoReader(c.reader, sharedSecret)
+	if err != nil {
+		return fmt.Errorf("new crypto reader: %w", err)
+	}
+
+	c.writer, err = newCryptoWriter(c.writer, sharedSecret)
+	if err != nil {
+		return fmt.Errorf("new crypto writer: %w", err)
+	}
+
+	c.state = clientStateProxy
+
+	return nil
+}
+
+func (c *clientConn) Read(b []byte) (int, error) {
+	err := c.handshake()
+	if err != nil {
+		return 0, fmt.Errorf("handshake: %w", err)
+	}
+
+	return c.reader.Read(b)
+}
+
+func (c *clientConn) Write(b []byte) (int, error) {
+	err := c.handshake()
+	if err != nil {
+		return 0, fmt.Errorf("handshake: %w", err)
+	}
+
+	return c.writer.Write(b)
+}
+
+func (c *clientConn) Close() error {
+	return c.c.Close()
+}
+
+func (c *clientConn) LocalAddr() net.Addr {
+	return c.c.LocalAddr()
+}
+
+func (c *clientConn) RemoteAddr() net.Addr {
+	return c.c.RemoteAddr()
+}
+
+func (c *clientConn) SetDeadline(t time.Time) error {
+	return c.c.SetDeadline(t)
+}
+
+func (c *clientConn) SetReadDeadline(t time.Time) error {
+	return c.c.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
+}

transport/internet/finalmask/minecraft/config.go

@@ -0,0 +1,27 @@
+package minecraft
+
+import (
+	"fmt"
+	"net"
+)
+
+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)
+	if err != nil {
+		return nil, fmt.Errorf("minecraft finalmask: %w", err)
+	}
+
+	return cc, nil
+}
+
+func (c *Config) WrapConnServer(conn net.Conn) (net.Conn, error) {
+	cc, err := wrapConnServer(conn, c.Password, c.RsaPrivateKey, c.RsaPublicKey)
+	if err != nil {
+		return nil, fmt.Errorf("minecraft finalmask: %w", err)
+	}
+
+	return cc, nil
+}

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

@@ -0,0 +1,160 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// versions:
+// 	protoc-gen-go v1.36.11
+// 	protoc        v6.33.5
+// source: config.proto
+
+package minecraft
+
+import (
+	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
+	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
+	reflect "reflect"
+	sync "sync"
+	unsafe "unsafe"
+)
+
+const (
+	// Verify that this generated code is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
+	// Verify that runtime/protoimpl is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
+)
+
+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"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *Config) Reset() {
+	*x = Config{}
+	mi := &file_config_proto_msgTypes[0]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *Config) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*Config) ProtoMessage() {}
+
+func (x *Config) ProtoReflect() protoreflect.Message {
+	mi := &file_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 Config.ProtoReflect.Descriptor instead.
+func (*Config) Descriptor() ([]byte, []int) {
+	return file_config_proto_rawDescGZIP(), []int{0}
+}
+
+func (x *Config) GetPassword() string {
+	if x != nil {
+		return x.Password
+	}
+	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
+	}
+	return nil
+}
+
+func (x *Config) GetRsaPublicKey() []byte {
+	if x != nil {
+		return x.RsaPublicKey
+	}
+	return nil
+}
+
+func (x *Config) GetHostname() string {
+	if x != nil {
+		return x.Hostname
+	}
+	return ""
+}
+
+var File_config_proto protoreflect.FileDescriptor
+
+const file_config_proto_rawDesc = "" +
+	"\n" +
+	"\fconfig.proto\x12+xray.transport.internet.finalmask.minecraft\"\xac\x01\n" +
+	"\x06Config\x12\x1a\n" +
+	"\bpassword\x18\x01 \x01(\tR\bpassword\x12\x1c\n" +
+	"\tusernames\x18\x02 \x03(\tR\tusernames\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\xa3\x01\n" +
+	"/com.xray.transport.internet.finalmask.minecraftP\x01Z@github.com/xtls/xray-core/transport/internet/finalmask/minecraft\xaa\x02+Xray.Transport.Internet.Finalmask.Minecraftb\x06proto3"
+
+var (
+	file_config_proto_rawDescOnce sync.Once
+	file_config_proto_rawDescData []byte
+)
+
+func file_config_proto_rawDescGZIP() []byte {
+	file_config_proto_rawDescOnce.Do(func() {
+		file_config_proto_rawDescData = protoimpl.X.CompressGZIP(unsafe.Slice(unsafe.StringData(file_config_proto_rawDesc), len(file_config_proto_rawDesc)))
+	})
+	return file_config_proto_rawDescData
+}
+
+var file_config_proto_msgTypes = make([]protoimpl.MessageInfo, 1)
+var file_config_proto_goTypes = []any{
+	(*Config)(nil), // 0: xray.transport.internet.finalmask.minecraft.Config
+}
+var file_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
+}
+
+func init() { file_config_proto_init() }
+func file_config_proto_init() {
+	if File_config_proto != nil {
+		return
+	}
+	type x struct{}
+	out := protoimpl.TypeBuilder{
+		File: protoimpl.DescBuilder{
+			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
+			RawDescriptor: unsafe.Slice(unsafe.StringData(file_config_proto_rawDesc), len(file_config_proto_rawDesc)),
+			NumEnums:      0,
+			NumMessages:   1,
+			NumExtensions: 0,
+			NumServices:   0,
+		},
+		GoTypes:           file_config_proto_goTypes,
+		DependencyIndexes: file_config_proto_depIdxs,
+		MessageInfos:      file_config_proto_msgTypes,
+	}.Build()
+	File_config_proto = out.File
+	file_config_proto_goTypes = nil
+	file_config_proto_depIdxs = nil
+}

transport/internet/finalmask/minecraft/config.proto

@@ -0,0 +1,16 @@
+syntax = "proto3";
+
+package xray.transport.internet.finalmask.minecraft;
+option csharp_namespace = "Xray.Transport.Internet.Finalmask.Minecraft";
+option go_package = "github.com/xtls/xray-core/transport/internet/finalmask/minecraft";
+option java_package = "com.xray.transport.internet.finalmask.minecraft";
+option java_multiple_files = true;
+
+
+message Config {
+    string password = 1;
+    repeated string usernames = 2;
+    bytes rsa_private_key = 8;
+    bytes rsa_public_key = 9;
+    string hostname = 10;
+}

transport/internet/finalmask/minecraft/derivation.go

@@ -0,0 +1,103 @@
+package minecraft
+
+import (
+	"crypto/rsa"
+	"crypto/sha256"
+	"fmt"
+	"math/big"
+)
+
+type sha256Stream struct {
+	seed    []byte
+	counter uint64
+	buf     []byte
+}
+
+func newSHA256Stream(seed []byte) *sha256Stream {
+	return &sha256Stream{
+		seed: seed,
+	}
+}
+
+func (s *sha256Stream) Read(p []byte) (n int, err error) {
+	for len(p) > len(s.buf) {
+		h := sha256.New()
+		h.Write(s.seed)
+		h.Write([]byte(fmt.Sprintf("-%d", s.counter)))
+		s.counter++
+		s.buf = append(s.buf, h.Sum(nil)...)
+	}
+	n = copy(p, s.buf)
+	s.buf = s.buf[n:]
+	return n, nil
+}
+
+func derivePrime(stream *sha256Stream) *big.Int {
+	pBytes := make([]byte, 64) // 512 bits
+	_, _ = stream.Read(pBytes)
+	pBytes[0] |= 0xc0  // ensure it is big enough so p*q is 1024 bits
+	pBytes[63] |= 0x01 // ensure odd
+
+	p := new(big.Int).SetBytes(pBytes)
+	for {
+		if p.ProbablyPrime(20) {
+			pMinus1 := new(big.Int).Sub(p, big.NewInt(1))
+			e := big.NewInt(65537)
+			gcd := new(big.Int).GCD(nil, nil, pMinus1, e)
+			if gcd.Cmp(big.NewInt(1)) == 0 {
+				return p
+			}
+		}
+		p.Add(p, big.NewInt(2))
+	}
+}
+
+// DeriveRSAKey derives a 1024-bit RSA private key from a password.
+func DeriveRSAKey(password string) (*rsa.PrivateKey, error) {
+	seed := []byte(password)
+
+	pStream := newSHA256Stream(append(seed, []byte("-p-prime")...))
+	qStream := newSHA256Stream(append(seed, []byte("-q-prime")...))
+
+	p := derivePrime(pStream)
+	q := derivePrime(qStream)
+
+	// ensure p != q (if they are, let's search q further)
+	for p.Cmp(q) == 0 {
+		q.Add(q, big.NewInt(2))
+		for {
+			if q.ProbablyPrime(20) {
+				qMinus1 := new(big.Int).Sub(q, big.NewInt(1))
+				e := big.NewInt(65537)
+				gcd := new(big.Int).GCD(nil, nil, qMinus1, e)
+				if gcd.Cmp(big.NewInt(1)) == 0 {
+					break
+				}
+			}
+			q.Add(q, big.NewInt(2))
+		}
+	}
+
+	n := new(big.Int).Mul(p, q)
+	pMinus1 := new(big.Int).Sub(p, big.NewInt(1))
+	qMinus1 := new(big.Int).Sub(q, big.NewInt(1))
+	totient := new(big.Int).Mul(pMinus1, qMinus1)
+
+	e := big.NewInt(65537)
+	d := new(big.Int).ModInverse(e, totient)
+	if d == nil {
+		return nil, fmt.Errorf("failed to compute mod inverse")
+	}
+
+	priv := &rsa.PrivateKey{
+		PublicKey: rsa.PublicKey{
+			N: n,
+			E: 65537,
+		},
+		D:      d,
+		Primes: []*big.Int{p, q},
+	}
+	priv.Precompute()
+
+	return priv, nil
+}

transport/internet/finalmask/minecraft/derivation_test.go

@@ -0,0 +1,58 @@
+package minecraft
+
+import (
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/hex"
+	"testing"
+)
+
+func TestDeriveRSAKey(t *testing.T) {
+	password := "my-very-secret-password-12345"
+
+	key1, err := DeriveRSAKey(password)
+	if err != nil {
+		t.Fatalf("failed to derive key: %v", err)
+	}
+
+	err = key1.Validate()
+	if err != nil {
+		t.Fatalf("key is not valid RSA key: %v", err)
+	}
+
+	key2, err := DeriveRSAKey(password)
+	if err != nil {
+		t.Fatalf("failed to derive key second time: %v", err)
+	}
+
+	// Verify determinism
+	if key1.D.Cmp(key2.D) != 0 || key1.N.Cmp(key2.N) != 0 {
+		t.Errorf("derived keys are not identical for the same password")
+	}
+
+	// Verify different passwords yield different keys
+	keyDifferent, err := DeriveRSAKey(password + "-different")
+	if err != nil {
+		t.Fatalf("failed to derive different key: %v", err)
+	}
+
+	if key1.D.Cmp(keyDifferent.D) == 0 || key1.N.Cmp(keyDifferent.N) == 0 {
+		t.Errorf("derived keys are identical for different passwords")
+	}
+}
+
+func TestDeriveRSAKeyGoldenPrivateKey(t *testing.T) {
+	const password = "deterministic-rsa-key-golden"
+	const wantPKCS1DERHash = "3a8c4ad56a6fb42dab73c4d5fc3af754460a2db1441edc0970cbc7f4e0798d2f"
+
+	key, err := DeriveRSAKey(password)
+	if err != nil {
+		t.Fatalf("failed to derive key: %v", err)
+	}
+
+	gotHash := sha256.Sum256(x509.MarshalPKCS1PrivateKey(key))
+	got := hex.EncodeToString(gotHash[:])
+	if got != wantPKCS1DERHash {
+		t.Fatalf("derived private key changed\nwant sha256: %s\n got sha256: %s", wantPKCS1DERHash, got)
+	}
+}

transport/internet/finalmask/minecraft/handshake_test.go

@@ -0,0 +1,156 @@
+package minecraft
+
+import (
+	"bytes"
+	"crypto/x509"
+	"net"
+	"testing"
+	"time"
+)
+
+func deriveTestRSAKey(t *testing.T, password string) ([]byte, []byte) {
+	t.Helper()
+
+	key, err := DeriveRSAKey(password)
+	if err != nil {
+		t.Fatalf("failed to derive rsa key: %v", err)
+	}
+
+	publicKey, err := x509.MarshalPKIXPublicKey(&key.PublicKey)
+	if err != nil {
+		t.Fatalf("failed to marshal public key: %v", err)
+	}
+
+	return x509.MarshalPKCS1PrivateKey(key), publicKey
+}
+
+func TestHandshakeSuccess(t *testing.T) {
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("failed to listen: %v", err)
+	}
+	defer ln.Close()
+
+	password := "super-secure-shared-key-12345"
+	usernames := []string{"test_user"}
+	privateKey, publicKey := deriveTestRSAKey(t, password)
+
+	go func() {
+		rawConn, err := ln.Accept()
+		if err != nil {
+			return
+		}
+		defer rawConn.Close()
+
+		server, err := wrapConnServer(rawConn, password, privateKey, publicKey)
+		if err != nil {
+			t.Errorf("failed to wrap server: %v", err)
+			return
+		}
+
+		buf := make([]byte, 1024)
+		n, err := server.Read(buf)
+		if err != nil {
+			t.Errorf("server read error: %v", err)
+			return
+		}
+
+		if !bytes.Equal(buf[:n], []byte("hello server")) {
+			t.Errorf("unexpected payload from client: %s", string(buf[:n]))
+			return
+		}
+
+		_, err = server.Write([]byte("hello client"))
+		if err != nil {
+			t.Errorf("server write error: %v", err)
+			return
+		}
+	}()
+
+	clientRaw, err := net.Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("failed to dial: %v", err)
+	}
+	defer clientRaw.Close()
+
+	client, err := newClientConn(clientRaw, usernames, password, publicKey, "localhost")
+	if err != nil {
+		t.Fatalf("failed to create client: %v", err)
+	}
+
+	_, err = client.Write([]byte("hello server"))
+	if err != nil {
+		t.Fatalf("client write error: %v", err)
+	}
+
+	buf := make([]byte, 1024)
+	n, err := client.Read(buf)
+	if err != nil {
+		t.Fatalf("client read error: %v", err)
+	}
+
+	if !bytes.Equal(buf[:n], []byte("hello client")) {
+		t.Errorf("unexpected payload from server: %s", string(buf[:n]))
+	}
+}
+
+func TestHandshakePasswordMismatch(t *testing.T) {
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("failed to listen: %v", err)
+	}
+	defer ln.Close()
+
+	clientPassword := "client-secret-123"
+	serverPassword := "server-secret-456"
+	usernames := []string{"test_user"}
+	serverPrivateKey, serverPublicKey := deriveTestRSAKey(t, serverPassword)
+	_, clientPublicKey := deriveTestRSAKey(t, clientPassword)
+
+	go func() {
+		rawConn, err := ln.Accept()
+		if err != nil {
+			return
+		}
+		defer rawConn.Close()
+
+		server, err := wrapConnServer(rawConn, 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)
+		}
+
+		// When client sends data, handshake happens and should fail
+		buf := make([]byte, 1024)
+		_, err = server.Read(buf)
+		if err == nil {
+			t.Errorf("expected handshake to fail due to password mismatch, but it succeeded")
+		} else {
+			t.Logf("server read failed as expected: %v", err)
+		}
+	}()
+
+	clientRaw, err := net.Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("failed to dial: %v", err)
+	}
+	defer clientRaw.Close()
+
+	client, err := newClientConn(clientRaw, usernames, clientPassword, clientPublicKey, "localhost")
+	if err != nil {
+		t.Fatalf("failed to create client: %v", err)
+	}
+
+	// Wait briefly or just perform write/read
+	_ = clientRaw.SetDeadline(time.Now().Add(100 * time.Millisecond))
+
+	_, err = client.Write([]byte("hello server"))
+	if err == nil {
+		// Try to read too
+		buf := make([]byte, 1024)
+		_, _ = client.Read(buf)
+	}
+
+	// Check if we lost connection or received error
+	t.Log("Handshake mismatch tested")
+}

transport/internet/finalmask/minecraft/protocol.go

@@ -0,0 +1,335 @@
+// Minecraft protocol
+package minecraft
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+)
+
+type field interface {
+	readFrom(r io.Reader) error
+	writeTo(w io.Writer) error
+}
+
+type mcPacket struct {
+	packetID int
+	data     []byte
+}
+
+func readPacket(b io.Reader) (*mcPacket, error) {
+	var packetLength Varint
+	err := packetLength.readFrom(b)
+	if err != nil {
+		return nil, fmt.Errorf("read packet length: %w", err)
+	}
+
+	var packetID Varint
+	err = packetID.readFrom(b)
+	if err != nil {
+		return nil, fmt.Errorf("read packet ID: %w", err)
+	}
+
+	dataLength := int(packetLength) - varintSize(packetID)
+	if dataLength < 0 || dataLength > 1024*32 {
+		return nil, fmt.Errorf("read packet: bad length: %d", dataLength)
+	}
+
+	data := make([]byte, dataLength)
+	_, err = io.ReadFull(b, data)
+	if err != nil {
+		return nil, fmt.Errorf("read packet data: %w", err)
+	}
+
+	return &mcPacket{
+		packetID: int(packetID),
+		data:     data,
+	}, nil
+}
+
+func (p *mcPacket) readFields(fields ...field) error {
+	r := bytes.NewReader(p.data)
+
+	for _, field := range fields {
+		err := field.readFrom(r)
+		if err != nil {
+			return fmt.Errorf("read packet field: %w", err)
+		}
+	}
+
+	return nil
+}
+
+type Varint int32
+
+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")
+		}
+	}
+
+	*v = Varint(value)
+
+	return nil
+}
+
+func (v *Varint) writeTo(w io.Writer) error {
+	SEGMENT_BITS := byte(0x7F)
+	CONTINUE_BIT := byte(0x80)
+
+	value := int32(*v)
+
+	for {
+		currentByte := byte(value & int32(SEGMENT_BITS))
+		value >>= 7
+		if value != 0 {
+			currentByte |= CONTINUE_BIT
+		}
+
+		_, err := w.Write([]byte{currentByte})
+		if err != nil {
+			return fmt.Errorf("write varint: %w", err)
+		}
+
+		if value == 0 {
+			break
+		}
+	}
+
+	return nil
+}
+
+func varintSize(value Varint) int {
+	size := 0
+	for {
+		size++
+		value >>= 7
+		if value == 0 {
+			break
+		}
+	}
+	return size
+}
+
+type String string
+
+func (v *String) readFrom(r io.Reader) error {
+	var length Varint = 0
+
+	err := length.readFrom(r)
+	if err != nil {
+		return fmt.Errorf("read string: %w", err)
+	}
+
+	if length < 0 || length > 4096 {
+		return fmt.Errorf("read string: bad length: %d", length)
+	}
+
+	buf := make([]byte, length)
+	_, err = io.ReadFull(r, buf)
+	if err != nil {
+		return fmt.Errorf("read string: %w", err)
+	}
+
+	*v = String(string(buf))
+
+	return nil
+}
+
+func (v *String) writeTo(w io.Writer) error {
+	strBytes := []byte(*v)
+	length := Varint(len(strBytes))
+
+	err := length.writeTo(w)
+	if err != nil {
+		return fmt.Errorf("write string: %w", err)
+	}
+
+	_, err = w.Write(strBytes)
+	if err != nil {
+		return fmt.Errorf("write string: %w", err)
+	}
+
+	return nil
+}
+
+type UnsignedShort uint16
+
+func (v *UnsignedShort) readFrom(r io.Reader) error {
+	var buf [2]byte
+	_, err := io.ReadFull(r, buf[:])
+	if err != nil {
+		return fmt.Errorf("read unsigned short: %w", err)
+	}
+
+	*v = UnsignedShort(buf[0])<<8 | UnsignedShort(buf[1])
+
+	return nil
+}
+
+func (v *UnsignedShort) writeTo(w io.Writer) error {
+	buf := []byte{byte(*v >> 8), byte(*v & 0xFF)}
+	_, err := w.Write(buf)
+	if err != nil {
+		return fmt.Errorf("write unsigned short: %w", err)
+	}
+	return nil
+}
+
+type Long int64
+
+func (v *Long) readFrom(r io.Reader) error {
+	var buf [8]byte
+	_, err := io.ReadFull(r, buf[:])
+	if err != nil {
+		return fmt.Errorf("read long: %w", err)
+	}
+
+	*v = Long(buf[0])<<56 | Long(buf[1])<<48 | Long(buf[2])<<40 | Long(buf[3])<<32 |
+		Long(buf[4])<<24 | Long(buf[5])<<16 | Long(buf[6])<<8 | Long(buf[7])
+
+	return nil
+}
+
+func (v *Long) writeTo(w io.Writer) error {
+	buf := []byte{
+		byte(*v >> 56), byte((*v >> 48) & 0xFF), byte((*v >> 40) & 0xFF), byte((*v >> 32) & 0xFF),
+		byte((*v >> 24) & 0xFF), byte((*v >> 16) & 0xFF), byte((*v >> 8) & 0xFF), byte(*v & 0xFF),
+	}
+
+	_, err := w.Write(buf)
+	if err != nil {
+		return fmt.Errorf("write long: %w", err)
+	}
+
+	return nil
+}
+
+type UUID [16]byte
+
+func (v *UUID) readFrom(r io.Reader) error {
+	_, err := io.ReadFull(r, v[:])
+	if err != nil {
+		return fmt.Errorf("read UUID: %w", err)
+	}
+
+	return nil
+}
+
+func (v *UUID) writeTo(w io.Writer) error {
+	_, err := w.Write(v[:])
+	if err != nil {
+		return fmt.Errorf("write UUID: %w", err)
+	}
+	return nil
+}
+
+type Bytes []byte
+
+func (v *Bytes) readFrom(r io.Reader) error {
+	var length Varint
+	err := length.readFrom(r)
+	if err != nil {
+		return fmt.Errorf("read bytes: %w", err)
+	}
+
+	if length < 0 || length >= 1024 {
+		return fmt.Errorf("read bytes: invalid size: %d", err)
+	}
+
+	buf := make([]byte, length)
+
+	_, err = io.ReadFull(r, buf)
+	if err != nil {
+		return fmt.Errorf("read bytes: %w", err)
+	}
+
+	*v = append([]byte(*v), buf...)
+
+	return nil
+}
+
+func (v *Bytes) writeTo(w io.Writer) error {
+	length := Varint(len(*v))
+	err := length.writeTo(w)
+	if err != nil {
+		return fmt.Errorf("write bytes length: %w", err)
+	}
+
+	_, err = w.Write(*v)
+	if err != nil {
+		return fmt.Errorf("write bytes: %w", err)
+	}
+
+	return nil
+}
+
+func readByte(r io.Reader) (byte, error) {
+	var buf [1]byte
+	_, err := io.ReadFull(r, buf[:])
+	if err != nil {
+		return 0, fmt.Errorf("read byte: %w", err)
+	}
+
+	return buf[0], nil
+}
+
+func writePacket(w io.Writer, packetID int, fields ...field) error {
+	var dataBuf bytes.Buffer
+
+	for _, field := range fields {
+		err := field.writeTo(&dataBuf)
+		if err != nil {
+			return 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)
+	}
+
+	var packetIDVarint Varint = Varint(packetID)
+	err = packetIDVarint.writeTo(&buf)
+	if err != nil {
+		return fmt.Errorf("write packet ID: %w", err)
+	}
+
+	buf.Write(dataBuf.Bytes())
+
+	_, err = w.Write(buf.Bytes())
+	if err != nil {
+		return fmt.Errorf("write packet data: %w", err)
+	}
+
+	return nil
+}
+
+func writeDisconnectPacket(w io.Writer, reason string) error {
+	return writePacket(w, 0x00, new(String(reason)))
+}

transport/internet/finalmask/minecraft/server.go

@@ -0,0 +1,289 @@
+package minecraft
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/subtle"
+	"crypto/x509"
+	"fmt"
+	"io"
+	"net"
+	"sync"
+	"time"
+)
+
+// Response by vanilla 26.1.2 server.
+var statusResponse = `{"description":"A Minecraft Server","players":{"max":20,"online":0},"version":{"name":"26.1.2","protocol":775},"enforcesSecureChat":true}`
+
+type serverState int
+
+var (
+	serverStateHandshake serverState = 1
+	serverStateProxy     serverState = 3
+)
+
+type serverConn struct {
+	reader io.Reader
+	writer io.Writer
+	c      net.Conn
+
+	state serverState
+
+	handshakeLock sync.Mutex
+	password      string
+	rsaPrivateKey *rsa.PrivateKey
+	rsaPublicKey  []byte
+}
+
+func (c *serverConn) handshake() error {
+	c.handshakeLock.Lock()
+	defer c.handshakeLock.Unlock()
+
+	if c.state != serverStateHandshake {
+		return nil
+	}
+
+	// handshake timeout
+	err := c.c.SetDeadline(time.Now().Add(time.Second * 30))
+	if err != nil {
+		return fmt.Errorf("set deadline: %w", err)
+	}
+	defer c.c.SetDeadline(time.Time{})
+
+	var (
+		protocolVersion Varint
+		serverAddress   String
+		serverPort      UnsignedShort
+		nextState       Varint
+	)
+
+	// handshake packet
+
+	pkt, err := readPacket(c.reader)
+	if err != nil {
+		return fmt.Errorf("read handshake packet: %w", err)
+	}
+
+	if pkt.packetID != 0 {
+		return fmt.Errorf("bad handshake packet id")
+	}
+
+	err = pkt.readFields(&protocolVersion, &serverAddress, &serverPort, &nextState)
+	if err != nil {
+		return fmt.Errorf("read handshake packet: %w", err)
+	}
+
+	switch nextState {
+	case 1:
+
+		// Ping
+
+		for range 2 {
+
+			pkt, err := readPacket(c.reader)
+			if err != nil {
+				return fmt.Errorf("read packet: %w", err)
+			}
+
+			switch pkt.packetID {
+			case 0: // Status Request
+
+				err = writePacket(c.writer, 0, new(String(statusResponse)))
+				if err != nil {
+					return fmt.Errorf("write status response: %w", err)
+				}
+
+			case 1: // Ping
+
+				var payload Long
+				err = pkt.readFields(&payload)
+				if err != nil {
+					return fmt.Errorf("read ping packet: %w", err)
+				}
+
+				err = writePacket(c.writer, 1, &payload)
+				if err != nil {
+					return fmt.Errorf("write ping response: %w", err)
+				}
+
+			}
+
+		}
+
+		return fmt.Errorf("ping")
+
+	case 2:
+
+		// Login
+
+		// login start
+
+		pkt, err := readPacket(c.reader)
+		if err != nil {
+			return fmt.Errorf("read login start packet: %w", err)
+		}
+
+		if pkt.packetID != 0 {
+			return fmt.Errorf("bad login start packet id")
+		}
+
+		var (
+			username String
+			uuid     UUID
+		)
+
+		err = pkt.readFields(&username, &uuid)
+		if err != nil {
+			return fmt.Errorf("read login start packet: %w", err)
+		}
+
+		// encrypt request
+
+		var (
+			serverId           String = String("")
+			publicKey          Bytes  = Bytes(c.rsaPublicKey)
+			verifyToken        Bytes  = Bytes(make([]byte, 4))
+			shouldAuthenticate Varint = Varint(1)
+		)
+
+		rand.Read(verifyToken)
+
+		err = writePacket(c.writer, 0x01, &serverId, &publicKey, &verifyToken, &shouldAuthenticate)
+		if err != nil {
+			return fmt.Errorf("write encryption request: %w", err)
+		}
+
+		// encrypt response
+
+		var (
+			encryptedSharedSecret Bytes
+			encryptedVerifyToken  Bytes
+
+			sharedSecret         []byte
+			decryptedVerifyToken []byte
+		)
+
+		pkt, err = readPacket(c.reader)
+		if err != nil {
+			return fmt.Errorf("read encrypt response: %w", err)
+		}
+
+		if pkt.packetID != 0x01 {
+			return fmt.Errorf("bad encrypt response packet id")
+		}
+
+		err = pkt.readFields(&encryptedSharedSecret, &encryptedVerifyToken)
+		if err != nil {
+			return fmt.Errorf("read encrypt response: %w", err)
+		}
+
+		sharedSecret, err = rsa.DecryptPKCS1v15(rand.Reader, c.rsaPrivateKey, encryptedSharedSecret)
+		if err != nil {
+			return fmt.Errorf("decrypt shared secret: %w", err)
+		}
+
+		decryptedVerifyToken, err = rsa.DecryptPKCS1v15(rand.Reader, c.rsaPrivateKey, encryptedVerifyToken)
+		if err != nil {
+			return fmt.Errorf("decrypt verify token: %w", err)
+		}
+
+		if len(decryptedVerifyToken) < 4 || !bytes.Equal(verifyToken, decryptedVerifyToken[:4]) {
+			return fmt.Errorf("verify token mismatch")
+		}
+
+		c.reader, err = newCryptoReader(c.reader, sharedSecret)
+		if err != nil {
+			return fmt.Errorf("new crypto reader: %w", err)
+		}
+
+		c.writer, err = newCryptoWriter(c.writer, sharedSecret)
+		if err != nil {
+			return fmt.Errorf("new crypto writer: %w", err)
+		}
+
+		// verify password
+		receivedPassword := decryptedVerifyToken[4:]
+
+		if subtle.ConstantTimeCompare(receivedPassword, []byte(c.password)) != 1 {
+			writeDisconnectPacket(c.writer, `{"type":"translatable","translate":"multiplayer.disconnect.authservers_down"}`)
+			return fmt.Errorf("bad password")
+		}
+
+		c.state = serverStateProxy
+
+		return nil
+
+	default:
+		return fmt.Errorf("bad handshake packet: bad next state: %d", nextState)
+	}
+}
+
+func (c *serverConn) Read(b []byte) (int, error) {
+	err := c.handshake()
+	if err != nil {
+		return 0, fmt.Errorf("handshake: %w", err)
+	}
+
+	return c.reader.Read(b)
+}
+
+func (c *serverConn) Write(b []byte) (int, error) {
+	err := c.handshake()
+	if err != nil {
+		return 0, fmt.Errorf("handshake: %w", err)
+	}
+
+	return c.writer.Write(b)
+}
+
+func (c *serverConn) Close() error {
+	return c.c.Close()
+}
+
+func (c *serverConn) LocalAddr() net.Addr {
+	return c.c.LocalAddr()
+}
+
+func (c *serverConn) RemoteAddr() net.Addr {
+	return c.c.RemoteAddr()
+}
+
+func (c *serverConn) SetDeadline(t time.Time) error {
+	return c.c.SetDeadline(t)
+}
+
+func (c *serverConn) SetReadDeadline(t time.Time) error {
+	return c.c.SetReadDeadline(t)
+}
+
+func (c *serverConn) SetWriteDeadline(t time.Time) error {
+	return c.c.SetWriteDeadline(t)
+}
+
+func wrapConnServer(c net.Conn, password string, rsaPrivateKeyDER []byte, rsaPublicKey []byte) (*serverConn, error) {
+	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)
+	}
+
+	s := &serverConn{
+		reader:        bufio.NewReader(c),
+		writer:        c,
+		c:             c,
+		state:         serverStateHandshake,
+		password:      password,
+		rsaPrivateKey: rsaPrivateKey,
+		rsaPublicKey:  rsaPublicKey,
+	}
+
+	return s, nil
+}

transport/internet/finalmask/minecraft/stream.go

@@ -0,0 +1,68 @@
+// Minecraft stream cipher
+package minecraft
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"fmt"
+	"io"
+)
+
+type cryptoStream struct {
+	stream cipher.Stream
+	r      io.Reader
+	w      io.Writer
+}
+
+func newCryptoReader(r io.Reader, sharedSecret []byte) (*cryptoStream, error) {
+	blockCipher, err := aes.NewCipher(sharedSecret)
+	if err != nil {
+		return nil, fmt.Errorf("new aes cipher: %w", err)
+	}
+
+	stream := newCFB8Decrypt(blockCipher, sharedSecret)
+
+	return &cryptoStream{stream: stream, r: r}, nil
+}
+
+func (c *cryptoStream) Read(b []byte) (int, error) {
+	if c.r == nil {
+		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.stream.XORKeyStream(b[:n], b[:n])
+
+	return n, nil
+}
+
+func newCryptoWriter(w io.Writer, sharedSecret []byte) (*cryptoStream, error) {
+	blockCipher, err := aes.NewCipher(sharedSecret)
+	if err != nil {
+		return nil, fmt.Errorf("new aes cipher: %w", err)
+	}
+
+	stream := newCFB8Encrypt(blockCipher, sharedSecret)
+
+	return &cryptoStream{stream: stream, w: w}, nil
+}
+
+func (c *cryptoStream) Write(b []byte) (int, error) {
+	if c.w == nil {
+		panic("write on a read-only crypto stream")
+	}
+
+	encrypted := make([]byte, len(b))
+	c.stream.XORKeyStream(encrypted, b)
+
+	n, err := c.w.Write(encrypted)
+	if err != nil {
+		return 0, fmt.Errorf("crypto writer: write: %w", err)
+	}
+
+	return n, nil
+}