diff options
| -rw-r--r-- | csrand/csrand.go | 7 | ||||
| -rw-r--r-- | framing/framing.go | 2 | ||||
| -rw-r--r-- | obfs4.go | 20 | ||||
| -rw-r--r-- | packet.go | 8 | ||||
| -rw-r--r-- | weighted_dist.go | 41 |
5 files changed, 58 insertions, 20 deletions
diff --git a/csrand/csrand.go b/csrand/csrand.go index 721fb1e..a3299aa 100644 --- a/csrand/csrand.go +++ b/csrand/csrand.go @@ -68,7 +68,12 @@ func (r csRandSource) Seed(seed int64) { // No-op. } -// Float64 returns, as a float 64, a pesudo random number in [0.0,1.0). +// Int63n returns, as a int64, a pseudo random number in [0, n). +func Int63n(n int64) int64 { + return CsRand.Int63n(n) +} + +// Float64 returns, as a float64, a pesudo random number in [0.0,1.0). func Float64() float64 { return CsRand.Float64() } diff --git a/framing/framing.go b/framing/framing.go index 66eeff5..48d12c3 100644 --- a/framing/framing.go +++ b/framing/framing.go @@ -287,7 +287,7 @@ func (decoder *Decoder) Decode(data []byte, frames *bytes.Buffer) (int, error) { } out, ok := secretbox.Open(data[:0], box[:n], &decoder.nextNonce, &decoder.key) if !ok || decoder.nextLengthInvalid { - // When a random lenght is used (on length error) the tag should always + // When a random length is used (on length error) the tag should always // mismatch, but be paranoid. return 0, ErrTagMismatch } @@ -33,6 +33,7 @@ package obfs4 import ( "bytes" + "crypto/sha256" "fmt" "io" "math/rand" @@ -568,7 +569,12 @@ func DialObfs4DialFn(dialFn DialFn, network, address, nodeID, publicKey string, c := new(Obfs4Conn) c.lenProbDist = newWDist(seed, 0, framing.MaximumSegmentLength) if iatObfuscation { - c.iatProbDist = newWDist(seed, 0, maxIatDelay) + iatSeedSrc := sha256.Sum256(seed.Bytes()[:]) + iatSeed, err := DrbgSeedFromBytes(iatSeedSrc[:]) + if err != nil { + return nil, err + } + c.iatProbDist = newWDist(iatSeed, 0, maxIatDelay) } c.conn, err = dialFn(network, address) if err != nil { @@ -596,6 +602,7 @@ type Obfs4Listener struct { nodeID *ntor.NodeID seed *DrbgSeed + iatSeed *DrbgSeed iatObfuscation bool closeDelayBytes int @@ -631,7 +638,7 @@ func (l *Obfs4Listener) AcceptObfs4() (*Obfs4Conn, error) { cObfs.listener = l cObfs.lenProbDist = newWDist(l.seed, 0, framing.MaximumSegmentLength) if l.iatObfuscation { - cObfs.iatProbDist = newWDist(l.seed, 0, maxIatDelay) + cObfs.iatProbDist = newWDist(l.iatSeed, 0, maxIatDelay) } if err != nil { c.Close() @@ -692,6 +699,14 @@ func ListenObfs4(network, laddr, nodeID, privateKey, seed string, iatObfuscation if err != nil { return nil, err } + l.iatObfuscation = iatObfuscation + if l.iatObfuscation { + iatSeedSrc := sha256.Sum256(l.seed.Bytes()[:]) + l.iatSeed, err = DrbgSeedFromBytes(iatSeedSrc[:]) + if err != nil { + return nil, err + } + } l.filter, err = newReplayFilter() if err != nil { @@ -701,7 +716,6 @@ func ListenObfs4(network, laddr, nodeID, privateKey, seed string, iatObfuscation rng := rand.New(newHashDrbg(l.seed)) l.closeDelayBytes = rng.Intn(maxCloseDelayBytes) l.closeDelay = rng.Intn(maxCloseDelay) - l.iatObfuscation = iatObfuscation // Start up the listener. l.listener, err = net.Listen(network, laddr) @@ -28,6 +28,7 @@ package obfs4 import ( + "crypto/sha256" "encoding/binary" "fmt" "io" @@ -182,7 +183,12 @@ func (c *Obfs4Conn) consumeFramedPackets(w io.Writer) (n int, err error) { } c.lenProbDist.reset(seed) if c.iatProbDist != nil { - c.iatProbDist.reset(seed) + iatSeedSrc := sha256.Sum256(seed.Bytes()[:]) + iatSeed, err := DrbgSeedFromBytes(iatSeedSrc[:]) + if err != nil { + break + } + c.iatProbDist.reset(iatSeed) } } default: diff --git a/weighted_dist.go b/weighted_dist.go index 04b0d2d..55432b2 100644 --- a/weighted_dist.go +++ b/weighted_dist.go @@ -39,6 +39,11 @@ import ( "github.com/yawning/obfs4/csrand" ) +const ( + minBuckets = 1 + maxBuckets = 100 +) + // DrbgSeedLength is the length of the hashDrbg seed. const DrbgSeedLength = 32 @@ -133,10 +138,11 @@ func (drbg *hashDrbg) Seed(seed int64) { // wDist is a weighted distribution. type wDist struct { - minValue int - maxValue int - values []int - buckets []float64 + minValue int + maxValue int + values []int + buckets []int64 + totalWeight int64 rng *rand.Rand } @@ -160,11 +166,11 @@ func newWDist(seed *DrbgSeed, min, max int) (w *wDist) { // sample generates a random value according to the distribution. func (w *wDist) sample() int { retIdx := 0 - totalProb := 0.0 - prob := csrand.Float64() - for i, bucketProb := range w.buckets { - totalProb += bucketProb - if prob <= totalProb { + var totalWeight int64 + weight := csrand.Int63n(w.totalWeight) + for i, bucketWeight := range w.buckets { + totalWeight += bucketWeight + if weight <= totalWeight { retIdx = i break } @@ -181,15 +187,22 @@ func (w *wDist) reset(seed *DrbgSeed) { nBuckets := (w.maxValue + 1) - w.minValue w.values = w.rng.Perm(nBuckets) + if nBuckets < minBuckets { + nBuckets = minBuckets + } + if nBuckets > maxBuckets { + nBuckets = maxBuckets + } + nBuckets = w.rng.Intn(nBuckets) + 1 - w.buckets = make([]float64, nBuckets) - var totalProb float64 + w.totalWeight = 0 + w.buckets = make([]int64, nBuckets) for i, _ := range w.buckets { - prob := w.rng.Float64() * (1.0 - totalProb) + prob := w.rng.Int63n(1000) w.buckets[i] = prob - totalProb += prob + w.totalWeight += prob } - w.buckets[len(w.buckets)-1] = 1.0 + w.buckets[len(w.buckets)-1] = w.totalWeight } /* vim :set ts=4 sw=4 sts=4 noet : */ |