Total rework HAP pkg and HomeKit source

pkg/hap/secure/secure.go

@@ -0,0 +1,156 @@
+package secure
+
+import (
+	"encoding/binary"
+	"io"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/AlexxIT/go2rtc/pkg/hap/chacha20poly1305"
+	"github.com/AlexxIT/go2rtc/pkg/hap/hkdf"
+)
+
+type Conn struct {
+	conn net.Conn
+
+	encryptKey []byte
+	decryptKey []byte
+	encryptCnt uint64
+	decryptCnt uint64
+
+	mx sync.Mutex
+}
+
+func Client(conn net.Conn, sharedKey []byte, isClient bool) (net.Conn, error) {
+	key1, err := hkdf.Sha512(sharedKey, "Control-Salt", "Control-Read-Encryption-Key")
+	if err != nil {
+		return nil, err
+	}
+
+	key2, err := hkdf.Sha512(sharedKey, "Control-Salt", "Control-Write-Encryption-Key")
+	if err != nil {
+		return nil, err
+	}
+
+	if isClient {
+		return &Conn{conn: conn, encryptKey: key2, decryptKey: key1}, nil
+	} else {
+		return &Conn{conn: conn, encryptKey: key1, decryptKey: key2}, nil
+	}
+}
+
+const (
+	// PacketSizeMax is the max length of encrypted packets
+	PacketSizeMax = 0x400
+
+	VerifySize = 2
+	NonceSize  = 8
+	Overhead   = 16 // chacha20poly1305.Overhead
+)
+
+func (c *Conn) Read(b []byte) (n int, err error) {
+	verify := make([]byte, VerifySize) // = packet length
+	buf := make([]byte, PacketSizeMax+Overhead)
+	nonce := make([]byte, NonceSize)
+
+	for {
+		if len(b) < PacketSizeMax {
+			return
+		}
+
+		if _, err = io.ReadFull(c.conn, verify); err != nil {
+			return
+		}
+
+		size := binary.LittleEndian.Uint16(verify)
+		ciphertext := buf[:size+Overhead]
+
+		if _, err = io.ReadFull(c.conn, ciphertext); err != nil {
+			return
+		}
+
+		binary.LittleEndian.PutUint64(nonce, c.decryptCnt)
+		c.decryptCnt++
+
+		// put decrypted text to b's end
+		_, err = chacha20poly1305.DecryptAndVerify(c.decryptKey, b[:0], nonce, ciphertext, verify)
+		if err != nil {
+			return
+		}
+
+		n += int(size) // plaintext size
+
+		// Finish when all bytes fit in b
+		if size < PacketSizeMax {
+			return
+		}
+
+		b = b[size:]
+	}
+}
+
+func (c *Conn) Write(b []byte) (n int, err error) {
+	c.mx.Lock()
+	defer c.mx.Unlock()
+
+	nonce := make([]byte, NonceSize)
+	buf := make([]byte, NonceSize+PacketSizeMax+Overhead)
+	verify := buf[:VerifySize] // part of write buffer
+
+	for {
+		size := len(b)
+		if size > PacketSizeMax {
+			size = PacketSizeMax
+		}
+
+		binary.LittleEndian.PutUint16(verify, uint16(size))
+
+		binary.LittleEndian.PutUint64(nonce, c.encryptCnt)
+		c.encryptCnt++
+
+		// put encrypted text to writing buffer just after size (2 bytes)
+		_, err = chacha20poly1305.EncryptAndSeal(c.encryptKey, buf[2:2], nonce, b[:size], verify)
+		if err != nil {
+			return
+		}
+
+		if _, err = c.conn.Write(buf[:VerifySize+size+Overhead]); err != nil {
+			return
+		}
+
+		n += size // plaintext size
+
+		if size < PacketSizeMax {
+			break
+		}
+
+		b = b[PacketSizeMax:]
+	}
+
+	return
+}
+
+func (c *Conn) Close() error {
+	return c.conn.Close()
+}
+
+func (c *Conn) LocalAddr() net.Addr {
+	return c.conn.LocalAddr()
+}
+
+func (c *Conn) RemoteAddr() net.Addr {
+	return c.conn.RemoteAddr()
+}
+
+func (c *Conn) SetDeadline(t time.Time) error {
+	return c.conn.SetDeadline(t)
+}
+
+func (c *Conn) SetReadDeadline(t time.Time) error {
+	return c.conn.SetReadDeadline(t)
+}
+
+func (c *Conn) SetWriteDeadline(t time.Time) error {
+	return c.conn.SetWriteDeadline(t)
+}