yes222

mc/bot/chat/mod.go

@@ -0,0 +1,207 @@
+package chat
+
+import (
+	"crypto"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/binary"
+	"encoding/pem"
+	"fmt"
+	"time"
+
+	"github.com/admin-else/strom/mc/api"
+	"github.com/admin-else/strom/mc/proto"
+	"github.com/admin-else/strom/mc/proto_generated/v1_21_11"
+	"github.com/google/uuid"
+)
+
+type Module struct {
+	*proto.Conn
+
+	Account *api.Account
+
+	// Chat signing state
+	canSign     bool
+	privKey     *rsa.PrivateKey
+	sessionUUID uuid.UUID
+	msgIndex    int32
+}
+
+// Start creates a chat module for the connection. If acc is an online account,
+// it fetches the profile key pair from Mojang and enables signed chat.
+func Start(c *proto.Conn, acc *api.Account) (*Module, error) {
+	m := &Module{Conn: c, Account: acc}
+	if acc != nil && acc.Ygg != "" {
+		if err := m.initSigning(acc); err != nil {
+			return nil, err
+		}
+	}
+	return m, nil
+}
+
+func (m *Module) initSigning(acc *api.Account) (err error) {
+	keys, err := acc.FetchKeys()
+	if err != nil {
+		return fmt.Errorf("fetch profile keys: %w", err)
+	}
+
+	priv, err := parsePrivateKey(keys.KeyPair.PrivateKey)
+	if err != nil {
+		return fmt.Errorf("parse private key: %w", err)
+	}
+
+	m.privKey = priv
+	m.sessionUUID = uuid.New()
+
+	pubDer, err := x509.MarshalPKIXPublicKey(&priv.PublicKey)
+	if err != nil {
+		return fmt.Errorf("marshal public key: %w", err)
+	}
+
+	sigBytes, err := base64.StdEncoding.DecodeString(keys.PublicKeySignatureV2)
+	if err != nil {
+		return fmt.Errorf("decode key signature: %w", err)
+	}
+
+	if err = m.Conn.Send(&v1_21_11.PlayToServerPacketChatSessionUpdate{
+		SessionUUID: m.sessionUUID,
+		ExpireTime:  keys.ExpiresAt.UnixMilli(),
+		PublicKey:   v1_21_11.ByteArray{Val: pubDer},
+		Signature:   v1_21_11.ByteArray{Val: sigBytes},
+	}); err != nil {
+		return fmt.Errorf("send chat session update: %w", err)
+	}
+
+	m.canSign = true
+	return nil
+}
+
+// SendMessage sends a chat message. If signing is enabled, the message is signed;
+// otherwise it is sent unsigned.
+func (m *Module) SendMessage(message string) (err error) {
+	if m.canSign {
+		return m.sendSigned(message)
+	}
+	return m.Conn.Send(&v1_21_11.PlayToServerPacketChatMessage{Message: message})
+}
+
+func (m *Module) sendSigned(message string) (err error) {
+	now := time.Now()
+
+	saltBytes := make([]byte, 8)
+	if _, err = rand.Read(saltBytes); err != nil {
+		return
+	}
+	salt := int64(binary.BigEndian.Uint64(saltBytes))
+
+	timestamp := now.UnixMilli()
+
+	payload, err := m.buildSignaturePayload(message, salt, timestamp)
+	if err != nil {
+		return
+	}
+
+	hashed := sha256.Sum256(payload)
+	sigBytes, err := rsa.SignPKCS1v15(rand.Reader, m.privKey, crypto.SHA256, hashed[:])
+	if err != nil {
+		return
+	}
+	if len(sigBytes) != 256 {
+		return fmt.Errorf("unexpected signature length: %d", len(sigBytes))
+	}
+	var signature [256]byte
+	copy(signature[:], sigBytes)
+
+	m.msgIndex++
+
+	return m.Conn.Send(&v1_21_11.PlayToServerPacketChatMessage{
+		Message:      message,
+		Timestamp:    timestamp,
+		Salt:         salt,
+		Signature:    &signature,
+		Offset:       0,
+		Acknowledged: [3]byte{},
+		Checksum:     0,
+	})
+}
+
+func (m *Module) buildSignaturePayload(content string, salt, timestampMillis int64) ([]byte, error) {
+	buf := make([]byte, 0, 64+len(content))
+	w := func(b []byte) { buf = append(buf, b...) }
+
+	// Header
+	w(int32Bytes(1))
+
+	// SignedMessageLink: sender UUID, session UUID, index
+	w(uuidBytes(m.Account.Uuid))
+	w(uuidBytes(m.sessionUUID))
+	w(int32Bytes(m.msgIndex))
+
+	// SignedMessageBody: salt, timestamp seconds, content
+	w(int64Bytes(uint64(salt)))
+	w(int64Bytes(uint64(timestampMillis / 1000)))
+	contentBytes := []byte(content)
+	w(int32Bytes(int32(len(contentBytes))))
+	w(contentBytes)
+
+	// LastSeenMessages: empty
+	w(int32Bytes(0))
+
+	return buf, nil
+}
+
+func parsePrivateKey(s string) (*rsa.PrivateKey, error) {
+	block, _ := pem.Decode([]byte(s))
+	if block != nil {
+		k, err := x509.ParsePKCS8PrivateKey(block.Bytes)
+		if err != nil {
+			k, err = x509.ParsePKCS1PrivateKey(block.Bytes)
+		}
+		if err != nil {
+			return nil, err
+		}
+		if key, ok := k.(*rsa.PrivateKey); ok {
+			return key, nil
+		}
+		return nil, fmt.Errorf("not an RSA private key")
+	}
+
+	// Some implementations return raw base64 DER instead of PEM
+	raw, err := base64.StdEncoding.DecodeString(s)
+	if err != nil {
+		return nil, err
+	}
+	k, err := x509.ParsePKCS8PrivateKey(raw)
+	if err != nil {
+		k, err = x509.ParsePKCS1PrivateKey(raw)
+	}
+	if err != nil {
+		return nil, err
+	}
+	key, ok := k.(*rsa.PrivateKey)
+	if !ok {
+		return nil, fmt.Errorf("not an RSA private key")
+	}
+	return key, nil
+}
+
+func int32Bytes(v int32) []byte {
+	b := make([]byte, 4)
+	binary.BigEndian.PutUint32(b, uint32(v))
+	return b
+}
+
+func int64Bytes(v uint64) []byte {
+	b := make([]byte, 8)
+	binary.BigEndian.PutUint64(b, v)
+	return b
+}
+
+func uuidBytes(u uuid.UUID) []byte {
+	b := make([]byte, 16)
+	copy(b, u[:])
+	return b
+}

mc/bot/keepalive/mod.go

@@ -0,0 +1,19 @@
+package keepalive
+
+import (
+	"github.com/admin-else/strom/mc/proto"
+	"github.com/admin-else/strom/mc/proto_generated/v1_21_8"
+)
+
+type mod struct {
+	*proto.Conn
+}
+
+func (m *mod) onKeepAlive(p *v1_21_8.PlayToClientPacketKeepAlive) (err error) {
+	return m.Send(&v1_21_8.PlayToServerPacketKeepAlive{KeepAliveId: p.KeepAliveId})
+}
+
+func Start(c *proto.Conn) {
+	m := &mod{Conn: c}
+	m.RegisterUntilLatest(m.onKeepAlive)
+}