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conn.go
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conn.go
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package libdisco
import (
"bytes"
"encoding/binary"
"encoding/hex"
"errors"
"io"
"net"
"sync"
"time"
"github.com/mimoo/StrobeGo/strobe"
)
// A Conn represents a secured connection.
// It implements the net.Conn interface.
type Conn struct {
conn net.Conn
isClient bool
// handshake
config *Config // configuration passed to constructor
handshakeComplete bool
handshakeMutex sync.Mutex
// Authentication thingies
isRemoteAuthenticated bool
remotePublicKey string
// input/output
in, out *strobe.Strobe
inLock, outLock sync.Mutex
inputBuffer []byte
// half duplex
isHalfDuplex bool
halfDuplexLock sync.Mutex
}
// Access to net.Conn methods.
// Cannot just embed net.Conn because that would
// export the struct field too.
// LocalAddr returns the local network address.
func (c *Conn) LocalAddr() net.Addr {
return c.conn.LocalAddr()
}
// Addr represents a newtork address.
type Addr struct {
network string
address string
}
// Network returns the network.
func (a Addr) Network() string {
return a.network
}
// String implements stringer interface
func (a Addr) String() string {
return a.address
}
// RemoteAddr returns the remote network address.
func (c *Conn) RemoteAddr() net.Addr {
if c.config.RemoteAddrContainsRemotePubkey && c.handshakeComplete {
return &Addr{
network: "tcp",
address: c.conn.RemoteAddr().String() + ":" + c.remotePublicKey,
}
}
return c.conn.RemoteAddr()
}
// SetDeadline sets the read and write deadlines associated with the connection.
// A zero value for t means Read and Write will not time out.
// After a Write has timed out, the Disco state is corrupt and all future writes will return the same error.
func (c *Conn) SetDeadline(t time.Time) error {
return c.conn.SetDeadline(t)
}
// SetReadDeadline sets the read deadline on the underlying connection.
// A zero value for t means Read will not time out.
func (c *Conn) SetReadDeadline(t time.Time) error {
return c.conn.SetReadDeadline(t)
}
// SetWriteDeadline sets the write deadline on the underlying connection.
// A zero value for t means Write will not time out.
// After a Write has timed out, the Disco state is corrupt and all future writes will return the same error.
func (c *Conn) SetWriteDeadline(t time.Time) error {
return c.conn.SetWriteDeadline(t)
}
// Write writes data to the connection.
func (c *Conn) Write(b []byte) (int, error) {
//
if hp := c.config.HandshakePattern; !c.isClient && (hp == NoiseN || hp == NoiseK || hp == NoiseX) {
panic("disco: a server should not write on one-way patterns")
}
// Make sure to go through the handshake first
if err := c.Handshake(); err != nil {
return 0, err
}
// Lock the write socket
if c.isHalfDuplex {
c.halfDuplexLock.Lock()
defer c.halfDuplexLock.Unlock()
} else {
c.outLock.Lock()
defer c.outLock.Unlock()
}
// process the data in a loop
var n int
data := b
buf := bytes.NewBuffer(data)
for buf.Len() > 0 {
// fragment the data
fragment := buf.Next(NoiseMaxPlaintextSize)
// Encrypt
ciphertext := c.out.Send_ENC_unauthenticated(false, fragment)
ciphertext = append(ciphertext, c.out.Send_MAC(false, 16)...)
// header (length)
length := make([]byte, 2)
binary.BigEndian.PutUint16(length, uint16(len(ciphertext)))
// Send data
_, err := c.conn.Write(append(length, ciphertext...))
if err != nil {
return n, err
}
n += len(fragment)
/*
// TODO: should we test if we sent the correct number of bytes?
if _ != len(ciphertext) {
return errors.New("disco: cannot send the whole data")
}
*/
}
return n, nil
}
// Read can be made to time out and return a net.Error with Timeout() == true
// after a fixed time limit; see SetDeadline and SetReadDeadline.
func (c *Conn) Read(b []byte) (n int, err error) {
// Make sure to go through the handshake first
if err = c.Handshake(); err != nil {
return
}
// Put this after Handshake, in case people were calling
// Read(nil) for the side effect of the Handshake.
if len(b) == 0 {
return
}
// If this is a one-way pattern, do some checks
if hp := c.config.HandshakePattern; c.isClient && (hp == NoiseN || hp == NoiseK || hp == NoiseX) {
panic("disco: a client should not read on one-way patterns")
}
// Lock the read socket
if c.isHalfDuplex {
c.halfDuplexLock.Lock()
defer c.halfDuplexLock.Unlock()
} else {
c.inLock.Lock()
defer c.inLock.Unlock()
}
// read whatever there is to read in the buffer
readSoFar := 0
if len(c.inputBuffer) > 0 {
copy(b, c.inputBuffer)
if len(c.inputBuffer) >= len(b) {
c.inputBuffer = c.inputBuffer[len(b):]
return len(b), nil
}
readSoFar += len(c.inputBuffer)
c.inputBuffer = c.inputBuffer[:0]
}
// read header from socket
bufHeader := make([]byte, 2)
if _, err := io.ReadFull(c.conn, bufHeader); err != nil {
return readSoFar, err
}
length := binary.BigEndian.Uint16(bufHeader)
if length > NoiseMessageLength {
return readSoFar, errors.New("disco: Disco message received exceeds DiscoMessageLength")
}
// read noise message from socket
noiseMessage := make([]byte, length)
if _, err := io.ReadFull(c.conn, noiseMessage); err != nil {
return readSoFar, err
}
// decrypt
if length < 16 {
return readSoFar, errors.New("disco: the received payload is shorter 16 bytes")
}
plaintext := c.in.Recv_ENC_unauthenticated(false, noiseMessage[:len(noiseMessage)-16])
ok := c.in.Recv_MAC(false, noiseMessage[len(noiseMessage)-16:])
if !ok {
return readSoFar, errors.New("disco: cannot decrypt the payload")
}
// append to the input buffer
c.inputBuffer = append(c.inputBuffer, plaintext...)
// read whatever we can read
rest := len(b) - readSoFar
copy(b[readSoFar:], c.inputBuffer)
if len(c.inputBuffer) >= rest {
c.inputBuffer = c.inputBuffer[rest:]
return len(b), nil
}
// we haven't filled the buffer
readSoFar += len(c.inputBuffer)
c.inputBuffer = c.inputBuffer[:0]
return readSoFar, nil
// TODO: should we continue to try and read other messages?
}
// Close closes the connection.
func (c *Conn) Close() error {
return c.conn.Close()
}
//
// Disco-related functions
//
// Handshake runs the client or server handshake protocol if
// it has not yet been run.
// Most uses of this package need not call Handshake explicitly:
// the first Read or Write will call it automatically.
func (c *Conn) Handshake() error {
// Locking the handshakeMutex
c.handshakeMutex.Lock()
defer c.handshakeMutex.Unlock()
// did we already go through the handshake?
if c.handshakeComplete {
return nil
}
// Disco.initialize(handshakePattern string, initiator bool, prologue []byte, s, e, rs, re *KeyPair) (h handshakeState)
var remoteKeyPair *KeyPair
if c.config.RemoteKey != nil {
if len(c.config.RemoteKey) != 32 {
return errors.New("disco: the provided remote key is not 32-byte")
}
remoteKeyPair = &KeyPair{}
copy(remoteKeyPair.PublicKey[:], c.config.RemoteKey)
}
hs := Initialize(c.config.HandshakePattern, c.isClient, c.config.Prologue, c.config.KeyPair, nil, remoteKeyPair, nil)
// pre-shared key
hs.psk = c.config.PreSharedKey
// start handshake
var c1, c2 *strobe.Strobe
var err error
var receivedPayload []byte
ContinueHandshake:
if hs.shouldWrite {
// we're writing the next message pattern
// if it's the message pattern and we're sending a static key, we also send a proof
// TODO: is this the best way of sending a proof :/ ?
var bufToWrite []byte
var proof []byte
if len(hs.messagePatterns) <= 2 {
proof = c.config.StaticPublicKeyProof
}
c1, c2, err = hs.WriteMessage(proof, &bufToWrite)
if err != nil {
return err
}
// header (length)
length := make([]byte, 2)
binary.BigEndian.PutUint16(length, uint16(len(bufToWrite)))
// write
_, err = c.conn.Write(append(length, bufToWrite...))
if err != nil {
return err
}
} else {
// we're reading the next message pattern, as well as reacting to any received data
bufHeader := make([]byte, 2) // length header
if _, err := io.ReadFull(c.conn, bufHeader); err != nil {
return err
}
length := binary.BigEndian.Uint16(bufHeader)
if length > NoiseMessageLength {
return errors.New("disco: Disco message received exceeds DiscoMessageLength")
}
noiseMessage := make([]byte, length) // noise message
if _, err := io.ReadFull(c.conn, noiseMessage); err != nil {
return err
}
c1, c2, err = hs.ReadMessage(noiseMessage, &receivedPayload)
if err != nil {
return err
}
}
// handshake not finished
if c1 == nil {
goto ContinueHandshake
}
// setup the Write and Read secure channels
if c1 == nil {
return errors.New("noise: the handshake did not return a secure channel to Write and Read from")
}
// Has the other peer been authenticated so far?
if !c.isRemoteAuthenticated && c.config.PublicKeyVerifier != nil {
// test if remote static key is empty
isRemoteStaticKeySet := byte(0)
for _, val := range hs.rs.PublicKey {
isRemoteStaticKeySet |= val
}
if isRemoteStaticKeySet != 0 {
// a remote static key has been received. Verify it
if !c.config.PublicKeyVerifier(hs.rs.PublicKey[:], receivedPayload) {
return errors.New("disco: the received public key could not be authenticated")
}
// authenticated!
c.isRemoteAuthenticated = true
c.remotePublicKey = hex.EncodeToString(hs.rs.PublicKey[:]) // so that it can be accessed later
}
}
// Processing the final handshake message returns two CipherState objects
// the first for encrypting transport messages from initiator to responder
// and the second for messages in the other direction.
if c2 != nil {
if c.isClient {
c.out, c.in = c1, c2
} else {
c.out, c.in = c2, c1
}
} else {
c.isHalfDuplex = true
c.in = c1
c.out = c1
}
// TODO: preserve c.hs.symmetricState.h
// At that point the HandshakeState should be deleted except for the hash value h, which may be used for post-handshake channel binding (see Section 11.2).
hs.clear()
// no errors :)
c.handshakeComplete = true
return nil
}
// IsRemoteAuthenticated can be used to check if the remote peer has been properly authenticated. It serves no real purpose for the moment as the handshake will not go through if a peer is not properly authenticated in patterns where the peer needs to be authenticated.
func (c *Conn) IsRemoteAuthenticated() bool {
return c.isRemoteAuthenticated
}
// RemotePublicKey returns the static key of the remote peer. It is useful in case the
// static key is only transmitted during the handshake.
func (c *Conn) RemotePublicKey() (string, error) {
if !c.handshakeComplete {
return "", errors.New("disco: handshake not completed")
}
return c.remotePublicKey, nil
}
/*
TODO: Do we need such a function? (this comes from go.TLS)
// ConnectionState returns basic Disco details about the connection.
func (c *Conn) ConnectionState() ConnectionState {
}
*/