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 TestWeightedDist(t *testing.T) {
seed, err := drbg.NewSeed()
if err != nil {
t.Fatal("failed to generate a DRBG seed:", err)
}
const nrTrials = 1000000
hist := make([]int, 1000)
w := New(seed, 0, 999, true)
if debug {
// Dump a string representation of the probability table.
fmt.Println("Table:")
var sum float64
for _, weight := range w.weights {
sum += weight
}
for i, weight := range w.weights {
p := weight / sum
if p > 0.000001 { // Filter out tiny values.
fmt.Printf(" [%d]: %f\n", w.minValue+w.values[i], p)
}
}
fmt.Println()
}
for i := 0; i < nrTrials; i++ {
value := w.Sample()
hist[value]++
}
if debug {
fmt.Println("Generated:")
for value, count := range hist {
if count != 0 {
p := float64(count) / float64(nrTrials)
fmt.Printf(" [%d]: %f (%d)\n", value, p, count)
}
}
}
}
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
}
func newJSONServerState(stateDir string, js *jsonServerState) (err error) {
// Generate everything a server needs, using the cryptographic PRNG.
var st obfs4ServerState
rawID := make([]byte, ntor.NodeIDLength)
if err = csrand.Bytes(rawID); err != nil {
return
}
if st.nodeID, err = ntor.NewNodeID(rawID); err != nil {
return
}
if st.identityKey, err = ntor.NewKeypair(false); err != nil {
return
}
if st.drbgSeed, err = drbg.NewSeed(); err != nil {
return
}
st.iatMode = iatNone
// Encode it into JSON format and write the state file.
js.NodeID = st.nodeID.Hex()
js.PrivateKey = st.identityKey.Private().Hex()
js.PublicKey = st.identityKey.Public().Hex()
js.DrbgSeed = st.drbgSeed.Hex()
js.IATMode = st.iatMode
var encoded []byte
if encoded, err = json.Marshal(js); err != nil {
return
}
if err = ioutil.WriteFile(path.Join(stateDir, stateFile), encoded, 0600); err != nil {
return err
}
return nil
}