forked from mycontroller-org/esphome_api
/
conn_encryption.go
275 lines (229 loc) · 6.83 KB
/
conn_encryption.go
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package connection
import (
"bufio"
"encoding/base64"
"encoding/binary"
"errors"
"fmt"
"io"
"net"
"sync"
"time"
"github.com/flynn/noise"
"github.com/rockavoldy/esphome_api/api"
"google.golang.org/protobuf/proto"
)
var (
ErrHandshakeFailed = errors.New("esphome_api: handshake failed")
ErrHandshakeNotDone = errors.New("esphome_api: handshake not done")
ErrInvalidEncryptionPreamble = errors.New("esphome_api: invalid preamble. encrypted message should starts with 0x01")
)
// encryption is based on noise protocol
// reference: https://noiseprotocol.org
type EncryptedConnection struct {
conn net.Conn
CommunicationTimeout time.Duration
encryptionKey []byte
handshakeState *noise.HandshakeState
isHandshakeSucceed bool
handshakeResponse []byte
encryption *noise.CipherState
decryption *noise.CipherState
writeMutex sync.Mutex
readMutex sync.Mutex
}
func NewEncryptedConnection(conn net.Conn, communicationTimeout time.Duration, encryptionKey string) (ApiConnection, error) {
// decode base64 key
_psk, err := base64.StdEncoding.DecodeString(encryptionKey)
if err != nil {
return nil, err
}
if len(_psk) != 32 {
return nil, fmt.Errorf("esphome_api: encryption key size should be 32 bytes. received:%d", len(_psk))
}
ec := &EncryptedConnection{
conn: conn,
CommunicationTimeout: communicationTimeout,
encryptionKey: _psk,
isHandshakeSucceed: false,
}
return ec, nil
}
// handshake implemented based on python implementation
// reference: https://github.com/esphome/aioesphomeapi/blob/main/aioesphomeapi/_frame_helper.py#L250
func (ec *EncryptedConnection) Handshake() error {
// send empty message
err := ec.writeToTransport(nil)
if err != nil {
return err
}
// wait for a response
err = ec.waitForResponse()
if err != nil {
return err
}
// create handshake state
_hs, err := noise.NewHandshakeState(
noise.Config{
Pattern: noise.HandshakeNN,
CipherSuite: noise.NewCipherSuite(noise.DH25519, noise.CipherChaChaPoly, noise.HashSHA256),
Initiator: true,
Prologue: []byte("NoiseAPIInit" + "\x00\x00"),
PresharedKey: ec.encryptionKey,
PresharedKeyPlacement: 0,
},
)
if err != nil {
return err
}
ec.handshakeState = _hs
// create handshake message
handshakeMessage, _, _, err := ec.handshakeState.WriteMessage(nil, nil)
if err != nil {
return err
}
// append 0x00 in front of handshake message
handshakeMessage = append([]byte{0x00}, handshakeMessage...)
// send handshake message to the transport
err = ec.writeToTransport(handshakeMessage)
if err != nil {
return err
}
// wait for handshake response
// handshake response will be added in ec.handshakeResponse
err = ec.waitForResponse()
if err != nil {
return err
}
// if handshake response available, process it and update encrypt and decrypt cipherState
if len(ec.handshakeResponse) > 0 {
// discard first byte of handshake response
_, _encryptCipherState, _decryptCipherState, err := ec.handshakeState.ReadMessage(nil, ec.handshakeResponse[1:])
if err == nil {
ec.encryption = _encryptCipherState
ec.decryption = _decryptCipherState
ec.isHandshakeSucceed = true
} else {
return err
}
}
// return error if handshake not succeed
if !ec.isHandshakeSucceed {
return ErrHandshakeFailed
}
return nil
}
func (ec *EncryptedConnection) waitForResponse() error {
_reader := bufio.NewReader(ec.conn)
_, err := ec.Read(_reader)
// ignore handshake not done error
if err != nil && !errors.Is(err, ErrHandshakeNotDone) {
return err
}
return nil
}
func (ec *EncryptedConnection) writeToTransport(data []byte) error {
if data == nil {
data = []byte{}
}
// preamble + data length (2 bytes fixed)
header := make([]byte, 3)
// preamble
header[0] = 0x01
// message length
header[1] = byte(len(data) >> 8 & 0xff)
header[2] = byte(len(data) & 0xff)
// append header + data
packed := append(header, data...)
// set write lock
ec.writeMutex.Lock()
defer ec.writeMutex.Unlock()
err := ec.conn.SetWriteDeadline(time.Now().Add(ec.CommunicationTimeout))
if err != nil {
return err
}
_, err = ec.conn.Write(packed)
return err
}
func (ec *EncryptedConnection) Write(message proto.Message) error {
messageBytes, err := proto.Marshal(message)
if err != nil {
return err
}
// type id (2 bytes) + message length (2 bytes)
header := make([]byte, 4)
typeID := api.TypeID(message)
header[0] = byte(typeID >> 8 & 0xff)
header[1] = byte(typeID & 0xff)
header[2] = byte(len(messageBytes) >> 8 & 0xff)
header[3] = byte(len(messageBytes) & 0xff)
packed := append(header, messageBytes...)
// encrypt the data
encryptedData, err := ec.encrypt(packed)
if err != nil {
return err
}
return ec.writeToTransport(encryptedData)
}
func (ec *EncryptedConnection) Read(reader *bufio.Reader) (proto.Message, error) {
// set read lock
ec.readMutex.Lock()
defer ec.readMutex.Unlock()
header := make([]byte, 3) // limit to 3 bytes of header
_, err := io.ReadFull(reader, header)
if err != nil {
return nil, err
}
preamble := header[0]
if preamble != 0x01 {
return nil, ErrInvalidEncryptionPreamble
}
encryptedMessageSize := binary.BigEndian.Uint16(header[1:3])
// get encrypted message bytes
encryptedMessageBytes := make([]byte, encryptedMessageSize)
_, err = io.ReadFull(reader, encryptedMessageBytes)
if err != nil {
return nil, err
}
// if handshake is not done, these bytes may be a handshake response
if !ec.isHandshakeSucceed {
ec.handshakeResponse = encryptedMessageBytes
}
// if there is no bytes to decrypt, return from here
if len(encryptedMessageBytes) == 0 {
return nil, nil
}
// decrypt the message
decryptedMessageBytes, err := ec.decrypt(encryptedMessageBytes)
if err != nil {
return nil, err
}
// get type id and message size
messageTypeID := uint64(binary.BigEndian.Uint16(decryptedMessageBytes[0:2]))
messageSize := int(binary.BigEndian.Uint16(decryptedMessageBytes[2:4]))
messageBytes := decryptedMessageBytes[4:]
if len(messageBytes) != messageSize {
return nil, fmt.Errorf("esphome_api: message length mismatched. expected:%d, actual:%d", messageSize, len(messageBytes))
}
message := api.NewMessageByTypeID(messageTypeID)
if message == nil {
return nil, fmt.Errorf("esphome_api: protocol error: unknown message type %#x", messageTypeID)
}
err = proto.Unmarshal(messageBytes, message)
if err != nil {
return nil, err
}
return message, nil
}
func (ec *EncryptedConnection) encrypt(data []byte) ([]byte, error) {
if ec.isHandshakeSucceed {
return ec.encryption.Encrypt(nil, nil, data)
}
return nil, ErrHandshakeNotDone
}
func (ec *EncryptedConnection) decrypt(data []byte) ([]byte, error) {
if ec.isHandshakeSucceed {
return ec.decryption.Decrypt(nil, nil, data)
}
return nil, ErrHandshakeNotDone
}