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Removed moving avg chaff in favour of random-padding

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This commit is contained in:
Russ Magee 2018-10-01 20:35:50 -07:00
parent 06ee94da03
commit 1485e8392e
1 changed files with 49 additions and 36 deletions
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85
hkexnet/hkexnet.go
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@ -49,6 +49,7 @@ import (
)
/*---------------------------------------------------------------------*/
const PAD_SZ = 32
type (
WinSize struct {
@ -80,9 +81,7 @@ type (
Rows uint16
Cols uint16
chaff ChaffConfig
totBytes *uint64 // total bytes xmitted so far
totPackets *uint64 // total packets xmitted so far
chaff ChaffConfig
closeStat *CSOType // close status (CSOExitStatus)
r cipher.Stream //read cipherStream
@ -266,7 +265,7 @@ func Dial(protocol string, ipport string, extensions ...string) (hc Conn, err er
// NOTE: kex default of KEX_HERRADURA may be overridden by
// future extension args to applyConnExtensions(), which is
// called prior to Dial()
hc = Conn{m: &sync.Mutex{}, c: c, closeStat: new(CSOType), h: hkex.New(0, 0), dBuf: new(bytes.Buffer), totBytes: new(uint64), totPackets: new(uint64)}
hc = Conn{m: &sync.Mutex{}, c: c, closeStat: new(CSOType), h: hkex.New(0, 0), dBuf: new(bytes.Buffer)}
hc.applyConnExtensions(extensions...)
// TODO: Factor out ALL params following this to helpers for
@ -399,13 +398,13 @@ func (hl *HKExListener) Accept() (hc Conn, err error) {
c, err := hl.l.Accept()
if err != nil {
hc := Conn{m: &sync.Mutex{}, c: nil, h: nil, closeStat: new(CSOType), cipheropts: 0, opts: 0,
r: nil, w: nil, totBytes: new(uint64), totPackets: new(uint64)}
r: nil, w: nil}
return hc, err
}
log.Println("[Accepted]")
hc = Conn{ /*kex: from client,*/ m: &sync.Mutex{}, c: c, h: hkex.New(0, 0), closeStat: new(CSOType), WinCh: make(chan WinSize, 1),
dBuf: new(bytes.Buffer), totBytes: new(uint64), totPackets: new(uint64)}
dBuf: new(bytes.Buffer)}
// TODO: Factor out ALL params following this to helpers for
// specific KEx algs
@ -503,13 +502,27 @@ func (hc Conn) Read(b []byte) (n int, err error) {
// to the parameter of Read() as a normal io.Reader
rs := &cipher.StreamReader{S: hc.r, R: db}
// The caller isn't necessarily reading the full payload so we need
// to decrypt ot an intermediate buffer, draining it on demand of caller
// to decrypt to an intermediate buffer, draining it on demand of caller
decryptN, err := rs.Read(payloadBytes)
log.Printf(" <-ptext:\r\n%s\r\n", hex.Dump(payloadBytes[:n]))
if err != nil {
log.Println("hkexnet.Read():", err)
//panic(err)
} else {
hc.rm.Write(payloadBytes) // Calc hmac on received data
// Padding: Read padSide, padLen, (padding | d) or (d | padding)
padSide := payloadBytes[0]
padLen := payloadBytes[1]
payloadBytes = payloadBytes[2:]
if padSide == 0 {
payloadBytes = payloadBytes[padLen:]
} else {
payloadBytes = payloadBytes[0 : len(payloadBytes)-int(padLen)]
}
//fmt.Printf("padSide:%d padLen:%d payloadBytes:%s\n",
// padSide, padLen, hex.Dump(payloadBytes))
// Throw away pkt if it's chaff (ie., caller to Read() won't see this data)
if ctrlStatOp == CSOChaff {
@ -531,8 +544,6 @@ func (hc Conn) Read(b []byte) (n int, err error) {
//log.Printf("hc.dBuf: %s\n", hex.Dump(hc.dBuf.Bytes()))
}
// Re-calculate hmac, compare with received value
hc.rm.Write(payloadBytes)
hTmp := hc.rm.Sum(nil)[0:4]
log.Printf("<%04x) HMAC:(i)%s (c)%02x\r\n", decryptN, hex.EncodeToString([]byte(hmacIn[0:])), hTmp)
@ -562,7 +573,9 @@ func (hc Conn) Read(b []byte) (n int, err error) {
//
// See go doc io.Writer
func (hc Conn) Write(b []byte) (n int, err error) {
//fmt.Printf("WRITE(%d)\n", len(b))
n, err = hc.WritePacket(b, CSONone)
//fmt.Printf("WROTE(%d)\n", n)
return n, err
}
@ -576,6 +589,28 @@ func (hc *Conn) WritePacket(b []byte, op byte) (n int, err error) {
return 0, errors.New("Secure chan not ready for writing")
}
//Padding
padLen := PAD_SZ - ((uint32(len(b)) + PAD_SZ) % PAD_SZ)
if padLen == PAD_SZ {
// No padding required
padLen = 0
}
padBytes := make([]byte, padLen)
rand.Read(padBytes)
// For a little more confusion let's support padding either before
// or after the payload.
padSide := rand.Intn(2)
//fmt.Printf("--\n")
//fmt.Printf("PRE_PADDING:%s\r\n", hex.Dump(b))
//fmt.Printf("padSide:%d padLen:%d\r\n", padSide, padLen)
if padSide == 0 {
b = append([]byte{byte(padSide)}, append([]byte{byte(padLen)}, append(padBytes, b...)...)...)
} else {
b = append([]byte{byte(padSide)}, append([]byte{byte(padLen)}, append(b, padBytes...)...)...)
}
//fmt.Printf("POST_PADDING:%s\r\n", hex.Dump(b))
//fmt.Printf("--\r\n")
// N.B. Originally this Lock() surrounded only the
// calls to binary.Write(hc.c ..) however there appears
// to be some other unshareable state in the Conn
@ -614,18 +649,6 @@ func (hc *Conn) WritePacket(b []byte, op byte) (n int, err error) {
err = binary.Write(hc.c, binary.BigEndian, payloadLen)
if err == nil {
n, err = hc.c.Write(wb.Bytes())
// If regular traffic, update running avg stats
if op != CSOChaff {
if *hc.totBytes+uint64(n) > *hc.totBytes {
*hc.totBytes = *hc.totBytes + uint64(n)
*hc.totPackets = *hc.totPackets + 1
log.Printf("totPackets:%d totBytes:%d\n",
*hc.totPackets, *hc.totBytes)
} else {
//overflow, don't add to totBytes
}
}
} else {
//fmt.Println("[c]WriteError!")
}
@ -640,7 +663,10 @@ func (hc *Conn) WritePacket(b []byte, op byte) (n int, err error) {
if err != nil {
log.Println(err)
}
return
// We must 'lie' to caller indicating the length of THEIR
// data written (ie., not including the padding and padding headers)
return n - 2 - int(padLen), err
}
func (hc *Conn) EnableChaff() {
@ -673,20 +699,7 @@ func (hc *Conn) chaffHelper() {
var nextDuration int
if hc.chaff.enabled {
var bufTmp []byte
if false {
bufTmp = make([]byte, rand.Intn(int(hc.chaff.szMax)))
} else {
// size chaff with running avg of actual traffic
denom := *hc.totPackets
numer := *hc.totBytes
if numer == 0 {
numer = uint64(rand.Intn(63) + 1)
}
if denom == 0 {
denom = 1
}
bufTmp = make([]byte, (numer / denom))
}
bufTmp = make([]byte, rand.Intn(int(hc.chaff.szMax)))
min := int(hc.chaff.msecsMin)
nextDuration = rand.Intn(int(hc.chaff.msecsMax)-min) + min
_, _ = rand.Read(bufTmp)