Add support for kTLS

Reference: https://gitlab.com/go-extension/tls

common/ktls/ktls_key_update.go

@@ -0,0 +1,173 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux && go1.25 && !without_badtls
+
+package ktls
+
+import (
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+)
+
+// handlePostHandshakeMessage processes a handshake message arrived after the
+// handshake is complete. Up to TLS 1.2, it indicates the start of a renegotiation.
+func (c *Conn) handlePostHandshakeMessage() error {
+	if *c.rawConn.Vers != tls.VersionTLS13 {
+		return errors.New("ktls: kernel does not support TLS 1.2 renegotiation")
+	}
+
+	msg, err := c.readHandshake(nil)
+	if err != nil {
+		return err
+	}
+	//c.retryCount++
+	//if c.retryCount > maxUselessRecords {
+	//	c.sendAlert(alertUnexpectedMessage)
+	//	return c.in.setErrorLocked(errors.New("tls: too many non-advancing records"))
+	//}
+
+	switch msg := msg.(type) {
+	case *newSessionTicketMsgTLS13:
+		// return errors.New("ktls: received new session ticket")
+		return nil
+	case *keyUpdateMsg:
+		return c.handleKeyUpdate(msg)
+	}
+	// The QUIC layer is supposed to treat an unexpected post-handshake CertificateRequest
+	// as a QUIC-level PROTOCOL_VIOLATION error (RFC 9001, Section 4.4). Returning an
+	// unexpected_message alert here doesn't provide it with enough information to distinguish
+	// this condition from other unexpected messages. This is probably fine.
+	c.sendAlert(alertUnexpectedMessage)
+	return fmt.Errorf("tls: received unexpected handshake message of type %T", msg)
+}
+
+func (c *Conn) handleKeyUpdate(keyUpdate *keyUpdateMsg) error {
+	//if c.quic != nil {
+	//	c.sendAlert(alertUnexpectedMessage)
+	//	return c.in.setErrorLocked(errors.New("tls: received unexpected key update message"))
+	//}
+
+	cipherSuite := cipherSuiteTLS13ByID(*c.rawConn.CipherSuite)
+	if cipherSuite == nil {
+		return c.rawConn.In.SetErrorLocked(c.sendAlert(alertInternalError))
+	}
+
+	newSecret := nextTrafficSecret(cipherSuite, *c.rawConn.In.TrafficSecret)
+	c.rawConn.In.SetTrafficSecret(cipherSuite, 0 /*tls.QUICEncryptionLevelInitial*/, newSecret)
+
+	err := c.resetupRX()
+	if err != nil {
+		c.sendAlert(alertInternalError)
+		return c.rawConn.In.SetErrorLocked(fmt.Errorf("ktls: resetupRX failed: %w", err))
+	}
+
+	if keyUpdate.updateRequested {
+		c.rawConn.Out.Lock()
+		defer c.rawConn.Out.Unlock()
+
+		resetup, err := c.resetupTX()
+		if err != nil {
+			c.sendAlertLocked(alertInternalError)
+			return c.rawConn.Out.SetErrorLocked(fmt.Errorf("ktls: resetupTX failed: %w", err))
+		}
+
+		msg := &keyUpdateMsg{}
+		msgBytes, err := msg.marshal()
+		if err != nil {
+			return err
+		}
+		_, err = c.writeRecordLocked(recordTypeHandshake, msgBytes)
+		if err != nil {
+			// Surface the error at the next write.
+			c.rawConn.Out.SetErrorLocked(err)
+			return nil
+		}
+
+		newSecret := nextTrafficSecret(cipherSuite, *c.rawConn.Out.TrafficSecret)
+		c.rawConn.Out.SetTrafficSecret(cipherSuite, 0 /*QUICEncryptionLevelInitial*/, newSecret)
+
+		err = resetup()
+		if err != nil {
+			return c.rawConn.Out.SetErrorLocked(fmt.Errorf("ktls: resetupTX failed: %w", err))
+		}
+	}
+
+	return nil
+}
+
+func (c *Conn) readHandshakeBytes(n int) error {
+	//if c.quic != nil {
+	//	return c.quicReadHandshakeBytes(n)
+	//}
+	for c.rawConn.Hand.Len() < n {
+		if err := c.readRecord(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (c *Conn) readHandshake(transcript io.Writer) (any, error) {
+	if err := c.readHandshakeBytes(4); err != nil {
+		return nil, err
+	}
+	data := c.rawConn.Hand.Bytes()
+
+	maxHandshakeSize := maxHandshake
+	// hasVers indicates we're past the first message, forcing someone trying to
+	// make us just allocate a large buffer to at least do the initial part of
+	// the handshake first.
+	//if c.haveVers && data[0] == typeCertificate {
+	// Since certificate messages are likely to be the only messages that
+	// can be larger than maxHandshake, we use a special limit for just
+	// those messages.
+	//maxHandshakeSize = maxHandshakeCertificateMsg
+	//}
+
+	n := int(data[1])<<16 | int(data[2])<<8 | int(data[3])
+	if n > maxHandshakeSize {
+		c.sendAlertLocked(alertInternalError)
+		return nil, c.rawConn.In.SetErrorLocked(fmt.Errorf("tls: handshake message of length %d bytes exceeds maximum of %d bytes", n, maxHandshakeSize))
+	}
+	if err := c.readHandshakeBytes(4 + n); err != nil {
+		return nil, err
+	}
+	data = c.rawConn.Hand.Next(4 + n)
+	return c.unmarshalHandshakeMessage(data, transcript)
+}
+
+func (c *Conn) unmarshalHandshakeMessage(data []byte, transcript io.Writer) (any, error) {
+	var m handshakeMessage
+	switch data[0] {
+	case typeNewSessionTicket:
+		if *c.rawConn.Vers == tls.VersionTLS13 {
+			m = new(newSessionTicketMsgTLS13)
+		} else {
+			return nil, os.ErrInvalid
+		}
+	case typeKeyUpdate:
+		m = new(keyUpdateMsg)
+	default:
+		return nil, c.rawConn.In.SetErrorLocked(c.sendAlert(alertUnexpectedMessage))
+	}
+
+	// The handshake message unmarshalers
+	// expect to be able to keep references to data,
+	// so pass in a fresh copy that won't be overwritten.
+	data = append([]byte(nil), data...)
+
+	if !m.unmarshal(data) {
+		return nil, c.rawConn.In.SetErrorLocked(c.sendAlert(alertDecodeError))
+	}
+
+	if transcript != nil {
+		transcript.Write(data)
+	}
+
+	return m, nil
+}