func (sf *obfs4ServerFactory) WrapConn(conn net.Conn) (net.Conn, error) {
// Not much point in having a separate newObfs4ServerConn routine when
// wrapping requires using values from the factory instance.
// Generate the session keypair *before* consuming data from the peer, to
// attempt to mask the rejection sampling due to use of Elligator2. This
// might be futile, but the timing differential isn't very large on modern
// hardware, and there are far easier statistical attacks that can be
// mounted as a distinguisher.
sessionKey, err := ntor.NewKeypair(true)
if err != nil {
return nil, err
}
lenDist := probdist.New(sf.lenSeed, 0, framing.MaximumSegmentLength, biasedDist)
var iatDist *probdist.WeightedDist
if sf.iatSeed != nil {
iatDist = probdist.New(sf.iatSeed, 0, maxIATDelay, biasedDist)
}
c := &obfs4Conn{conn, true, lenDist, iatDist, sf.iatMode, bytes.NewBuffer(nil), bytes.NewBuffer(nil), nil, nil}
startTime := time.Now()
if err = c.serverHandshake(sf, sessionKey); err != nil {
c.closeAfterDelay(sf, startTime)
return nil, err
}
return c, nil
}
func newScrambleSuitClientConn(conn net.Conn, tStore *ssTicketStore, ca *ssClientArgs) (net.Conn, error) {
// At this point we have kB and our session key, so we can directly
// start handshaking and seeing what happens.
// Seed the initial polymorphism distribution.
seed, err := drbg.NewSeed()
if err != nil {
return nil, err
}
dist := probdist.New(seed, minLenDistLength, maxLenDistLength, true)
// Allocate the client structure.
c := &ssConn{conn, false, dist, bytes.NewBuffer(nil), bytes.NewBuffer(nil), ssRxState{}, nil, nil, tStore}
// Start the handshake timeout.
deadline := time.Now().Add(clientHandshakeTimeout)
if err := conn.SetDeadline(deadline); err != nil {
return nil, err
}
// Attempt to handshake.
if err := c.clientHandshake(ca.kB, ca.sessionKey); err != nil {
return nil, err
}
// Stop the handshake timeout.
if err := conn.SetDeadline(time.Time{}); err != nil {
return nil, err
}
return c, nil
}
func newObfs4ClientConn(conn net.Conn, args *obfs4ClientArgs) (c *obfs4Conn, err error) {
// Generate the initial protocol polymorphism distribution(s).
var seed *drbg.Seed
if seed, err = drbg.NewSeed(); err != nil {
return
}
lenDist := probdist.New(seed, 0, framing.MaximumSegmentLength, biasedDist)
var iatDist *probdist.WeightedDist
if args.iatMode != iatNone {
var iatSeed *drbg.Seed
iatSeedSrc := sha256.Sum256(seed.Bytes()[:])
if iatSeed, err = drbg.SeedFromBytes(iatSeedSrc[:]); err != nil {
return
}
iatDist = probdist.New(iatSeed, 0, maxIATDelay, biasedDist)
}
// Allocate the client structure.
c = &obfs4Conn{conn, false, lenDist, iatDist, args.iatMode, bytes.NewBuffer(nil), bytes.NewBuffer(nil), nil, nil}
// Start the handshake timeout.
deadline := time.Now().Add(clientHandshakeTimeout)
if err = conn.SetDeadline(deadline); err != nil {
return nil, err
}
if err = c.clientHandshake(args.nodeID, args.publicKey, args.sessionKey); err != nil {
return nil, err
}
// Stop the handshake timeout.
if err = conn.SetDeadline(time.Time{}); err != nil {
return nil, err
}
return
}