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Move the SipHash DRBG off into it's own package.

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This commit is contained in:
Yawning Angel 2014-06-02 16:47:30 +00:00
parent 36228437c4
commit 5cb3369e20
5 changed files with 165 additions and 113 deletions
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145
drbg/hash_drbg.go Normal file
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@ -0,0 +1,145 @@
/*
* Copyright (c) 2014, Yawning Angel <yawning at torproject dot org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
// Package drbg implements a minimalistic DRBG based off SipHash-2-4 in OFB
// mode.
package drbg
import (
"encoding/base64"
"encoding/binary"
"fmt"
"hash"
"github.com/dchest/siphash"
"github.com/yawning/obfs4/csrand"
)
// Size is the length of the HashDrbg output.
const Size = siphash.Size
// SeedLength is the length of the HashDrbg seed.
const SeedLength = 32
// Seed is the initial state for a HashDrbg. It consists of a SipHash-2-4
// key, and 16 bytes of initial data.
type Seed [SeedLength]byte
// Bytes returns a pointer to the raw HashDrbg seed.
func (seed *Seed) Bytes() *[SeedLength]byte {
return (*[SeedLength]byte)(seed)
}
// Base64 returns the Base64 representation of the seed.
func (seed *Seed) Base64() string {
return base64.StdEncoding.EncodeToString(seed.Bytes()[:])
}
// NewSeed returns a Seed initialized with the runtime CSPRNG.
func NewSeed() (seed *Seed, err error) {
seed = new(Seed)
err = csrand.Bytes(seed.Bytes()[:])
if err != nil {
return nil, err
}
return
}
// SeedFromBytes creates a Seed from the raw bytes.
func SeedFromBytes(src []byte) (seed *Seed, err error) {
if len(src) != SeedLength {
return nil, InvalidSeedLengthError(len(src))
}
seed = new(Seed)
copy(seed.Bytes()[:], src)
return
}
// SeedFromBase64 creates a Seed from the Base64 representation.
func SeedFromBase64(encoded string) (seed *Seed, err error) {
var raw []byte
raw, err = base64.StdEncoding.DecodeString(encoded)
if err != nil {
return nil, err
}
return SeedFromBytes(raw)
}
// InvalidSeedLengthError is the error returned when the seed provided to the
// DRBG is an invalid length.
type InvalidSeedLengthError int
func (e InvalidSeedLengthError) Error() string {
return fmt.Sprintf("invalid seed length: %d", int(e))
}
// HashDrbg is a CSDRBG based off of SipHash-2-4 in OFB mode.
type HashDrbg struct {
sip hash.Hash64
ofb [Size]byte
}
// NewHashDrbg makes a HashDrbg instance based off an optional seed. The seed
// is truncated to SeedLength.
func NewHashDrbg(seed *Seed) *HashDrbg {
drbg := new(HashDrbg)
drbg.sip = siphash.New(seed.Bytes()[:16])
copy(drbg.ofb[:], seed.Bytes()[16:])
return drbg
}
// Int63 returns a uniformly distributed random integer [0, 1 << 63).
func (drbg *HashDrbg) Int63() int64 {
block := drbg.NextBlock()
ret := binary.BigEndian.Uint64(block)
ret &= (1<<63 - 1)
return int64(ret)
}
// Seed does nothing, call NewHashDrbg if you want to reseed.
func (drbg *HashDrbg) Seed(seed int64) {
// No-op.
}
// NextBlock returns the next 8 byte DRBG block.
func (drbg *HashDrbg) NextBlock() []byte {
drbg.sip.Write(drbg.ofb[:])
copy(drbg.ofb[:], drbg.sip.Sum(nil))
ret := make([]byte, Size)
copy(ret, drbg.ofb[:])
return ret
}
/* vim :set ts=4 sw=4 sts=4 noet : */

15
obfs4.go
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@ -41,6 +41,7 @@ import (
"syscall"
"time"
"github.com/yawning/obfs4/drbg"
"github.com/yawning/obfs4/framing"
"github.com/yawning/obfs4/ntor"
)
@ -561,7 +562,7 @@ func DialObfs4DialFn(dialFn DialFn, network, address, nodeID, publicKey string,
}
// Generate the initial length obfuscation distribution.
seed, err := NewDrbgSeed()
seed, err := drbg.NewSeed()
if err != nil {
return nil, err
}
@ -571,7 +572,7 @@ func DialObfs4DialFn(dialFn DialFn, network, address, nodeID, publicKey string,
c.lenProbDist = newWDist(seed, 0, framing.MaximumSegmentLength)
if iatObfuscation {
iatSeedSrc := sha256.Sum256(seed.Bytes()[:])
iatSeed, err := DrbgSeedFromBytes(iatSeedSrc[:])
iatSeed, err := drbg.SeedFromBytes(iatSeedSrc[:])
if err != nil {
return nil, err
}
@ -610,8 +611,8 @@ type Obfs4Listener struct {
keyPair *ntor.Keypair
nodeID *ntor.NodeID
seed *DrbgSeed
iatSeed *DrbgSeed
seed *drbg.Seed
iatSeed *drbg.Seed
iatObfuscation bool
closeDelayBytes int
@ -715,14 +716,14 @@ func ListenObfs4(network, laddr, nodeID, privateKey, seed string, iatObfuscation
if err != nil {
return nil, err
}
l.seed, err = DrbgSeedFromBase64(seed)
l.seed, err = drbg.SeedFromBase64(seed)
if err != nil {
return nil, err
}
l.iatObfuscation = iatObfuscation
if l.iatObfuscation {
iatSeedSrc := sha256.Sum256(l.seed.Bytes()[:])
l.iatSeed, err = DrbgSeedFromBytes(iatSeedSrc[:])
l.iatSeed, err = drbg.SeedFromBytes(iatSeedSrc[:])
if err != nil {
return nil, err
}
@ -733,7 +734,7 @@ func ListenObfs4(network, laddr, nodeID, privateKey, seed string, iatObfuscation
return nil, err
}
rng := rand.New(newHashDrbg(l.seed))
rng := rand.New(drbg.NewHashDrbg(l.seed))
l.closeDelayBytes = rng.Intn(maxCloseDelayBytes)
l.closeDelay = rng.Intn(maxCloseDelay)

3
obfs4proxy/obfs4proxy.go
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@ -62,6 +62,7 @@ import (
"git.torproject.org/pluggable-transports/goptlib.git"
"github.com/yawning/obfs4"
"github.com/yawning/obfs4/drbg"
"github.com/yawning/obfs4/ntor"
)
@ -389,7 +390,7 @@ func generateServerParams(id string) {
return
}
seed, err := obfs4.NewDrbgSeed()
seed, err := drbg.NewSeed()
if err != nil {
fmt.Println("Failed to generate DRBG seed:", err)
return

9
packet.go
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@ -34,6 +34,7 @@ import (
"io"
"syscall"
"github.com/yawning/obfs4/drbg"
"github.com/yawning/obfs4/framing"
)
@ -41,7 +42,7 @@ const (
packetOverhead = 2 + 1
maxPacketPayloadLength = framing.MaximumFramePayloadLength - packetOverhead
maxPacketPaddingLength = maxPacketPayloadLength
seedPacketPayloadLength = DrbgSeedLength
seedPacketPayloadLength = drbg.SeedLength
consumeReadSize = framing.MaximumSegmentLength * 16
)
@ -176,15 +177,15 @@ func (c *Obfs4Conn) consumeFramedPackets(w io.Writer) (n int, err error) {
case packetTypePrngSeed:
// Only regenerate the distribution if we are the client.
if len(payload) == seedPacketPayloadLength && !c.isServer {
var seed *DrbgSeed
seed, err = DrbgSeedFromBytes(payload)
var seed *drbg.Seed
seed, err = drbg.SeedFromBytes(payload)
if err != nil {
break
}
c.lenProbDist.reset(seed)
if c.iatProbDist != nil {
iatSeedSrc := sha256.Sum256(seed.Bytes()[:])
iatSeed, err := DrbgSeedFromBytes(iatSeedSrc[:])
iatSeed, err := drbg.SeedFromBytes(iatSeedSrc[:])
if err != nil {
break
}

106
weighted_dist.go
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@ -28,15 +28,11 @@
package obfs4
import (
"encoding/base64"
"encoding/binary"
"fmt"
"hash"
"math/rand"
"github.com/dchest/siphash"
"github.com/yawning/obfs4/csrand"
"github.com/yawning/obfs4/drbg"
)
const (
@ -44,98 +40,6 @@ const (
maxBuckets = 100
)
// DrbgSeedLength is the length of the hashDrbg seed.
const DrbgSeedLength = 32
// DrbgSeed is the initial state for a hashDrbg. It consists of a SipHash-2-4
// key, and 16 bytes of initial data.
type DrbgSeed [DrbgSeedLength]byte
// Bytes returns a pointer to the raw hashDrbg seed.
func (seed *DrbgSeed) Bytes() *[DrbgSeedLength]byte {
return (*[DrbgSeedLength]byte)(seed)
}
// Base64 returns the Base64 representation of the seed.
func (seed *DrbgSeed) Base64() string {
return base64.StdEncoding.EncodeToString(seed.Bytes()[:])
}
// NewDrbgSeed returns a DrbgSeed initialized with the runtime CSPRNG.
func NewDrbgSeed() (seed *DrbgSeed, err error) {
seed = new(DrbgSeed)
err = csrand.Bytes(seed.Bytes()[:])
if err != nil {
return nil, err
}
return
}
// DrbgSeedFromBytes creates a DrbgSeed from the raw bytes.
func DrbgSeedFromBytes(src []byte) (seed *DrbgSeed, err error) {
if len(src) != DrbgSeedLength {
return nil, InvalidSeedLengthError(len(src))
}
seed = new(DrbgSeed)
copy(seed.Bytes()[:], src)
return
}
// DrbgSeedFromBase64 creates a DrbgSeed from the Base64 representation.
func DrbgSeedFromBase64(encoded string) (seed *DrbgSeed, err error) {
var raw []byte
raw, err = base64.StdEncoding.DecodeString(encoded)
if err != nil {
return nil, err
}
return DrbgSeedFromBytes(raw)
}
// InvalidSeedLengthError is the error returned when the seed provided to the
// DRBG is an invalid length.
type InvalidSeedLengthError int
func (e InvalidSeedLengthError) Error() string {
return fmt.Sprintf("hashDrbg: Invalid seed length: %d", int(e))
}
// hashDrbg is a CSDRBG based off of SipHash-2-4 in OFB mode.
type hashDrbg struct {
sip hash.Hash64
ofb [siphash.Size]byte
}
// newHashDrbg makes a hashDrbg instance based off an optional seed. The seed
// is truncated to DrbgSeedLength.
func newHashDrbg(seed *DrbgSeed) *hashDrbg {
drbg := new(hashDrbg)
drbg.sip = siphash.New(seed.Bytes()[:16])
copy(drbg.ofb[:], seed.Bytes()[16:])
return drbg
}
// Int63 returns a uniformly distributed random integer [0, 1 << 63).
func (drbg *hashDrbg) Int63() int64 {
// Use SipHash-2-4 in OFB mode to generate random numbers.
drbg.sip.Write(drbg.ofb[:])
copy(drbg.ofb[:], drbg.sip.Sum(nil))
ret := binary.BigEndian.Uint64(drbg.ofb[:])
ret &= (1<<63 - 1)
return int64(ret)
}
// Seed does nothing, call newHashDrbg if you want to reseed.
func (drbg *hashDrbg) Seed(seed int64) {
// No-op.
}
// wDist is a weighted distribution.
type wDist struct {
minValue int
@ -148,8 +52,8 @@ type wDist struct {
}
// newWDist creates a weighted distribution of values ranging from min to max
// based on a hashDrbg initialized with seed.
func newWDist(seed *DrbgSeed, min, max int) (w *wDist) {
// based on a HashDrbg initialized with seed.
func newWDist(seed *drbg.Seed, min, max int) (w *wDist) {
w = new(wDist)
w.minValue = min
w.maxValue = max
@ -180,9 +84,9 @@ func (w *wDist) sample() int {
}
// reset generates a new distribution with the same min/max based on a new seed.
func (w *wDist) reset(seed *DrbgSeed) {
func (w *wDist) reset(seed *drbg.Seed) {
// Initialize the deterministic random number generator.
drbg := newHashDrbg(seed)
drbg := drbg.NewHashDrbg(seed)
w.rng = rand.New(drbg)
nBuckets := (w.maxValue + 1) - w.minValue