// CONTRACT: data smaller than dataMaxSize is read atomically.
func (sc *SecretConnection) Read(data []byte) (n int, err error) {
if 0 < len(sc.recvBuffer) {
n_ := copy(data, sc.recvBuffer)
sc.recvBuffer = sc.recvBuffer[n_:]
return
}
sealedFrame := make([]byte, sealedFrameSize)
_, err = io.ReadFull(sc.conn, sealedFrame)
if err != nil {
return
}
// decrypt the frame
var frame = make([]byte, totalFrameSize)
// fmt.Printf("secretbox.Open(sealed:%X,recvNonce:%X,shrSecret:%X\n", sealedFrame, sc.recvNonce, sc.shrSecret)
_, ok := secretbox.Open(frame[:0], sealedFrame, sc.recvNonce, sc.shrSecret)
if !ok {
return n, errors.New("Failed to decrypt SecretConnection")
}
incr2Nonce(sc.recvNonce)
// end decryption
var chunkLength = binary.BigEndian.Uint16(frame) // read the first two bytes
if chunkLength > dataMaxSize {
return 0, errors.New("chunkLength is greater than dataMaxSize")
}
var chunk = frame[dataLenSize : dataLenSize+chunkLength]
n = copy(data, chunk)
sc.recvBuffer = chunk[n:]
return
}
// OpenAfterPrecomputation performs the same actions as Open, but takes a
// shared key as generated by Precompute.
func OpenAfterPrecomputation(out, box []byte, nonce *[24]byte, sharedKey *[32]byte) ([]byte, bool) {
return secretbox.Open(out, box, nonce, sharedKey)
}
// Open authenticates and decrypts a box produced by Seal and appends the
// message to out, which must not overlap box. The output will be Overhead
// bytes smaller than box.
func Open(out, box []byte, nonce *[24]byte, peersPublicKey, privateKey *[32]byte) ([]byte, bool) {
var sharedKey [32]byte
Precompute(&sharedKey, peersPublicKey, privateKey)
return secretbox.Open(out, box, nonce, &sharedKey)
}