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xs
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**BREAKING** Switch to EtA per Krawczyk2001 

Signed-off-by: Russ Magee <rmagee@gmail.com>
This commit is contained in:
Russ Magee 2020-12-15 22:09:18 -08:00
parent 640e59be4f
commit 3193ede825
2 changed files with 23 additions and 28 deletions
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2
Makefile
View File

@ -1,4 +1,4 @@
VERSION := 0.8.26
VERSION := 0.9.0pre
.PHONY: lint vis clean common client server passwd subpkgs install uninstall reinstall
## Tag version of binaries with build info wrt.

49
xsnet/net.go
View File

@ -1288,6 +1288,16 @@ func (hc Conn) Read(b []byte) (n int, err error) {
log.Printf(" <:ctext:\r\n%s\r\n", hex.Dump(payloadBytes[:n]))
}
hc.rm.Write(payloadBytes) // Calc hmac on received data
hTmp := hc.rm.Sum(nil)[0:HMAC_CHK_SZ]
//log.Printf("<%04x) HMAC:(i)%s (c)%02x\r\n", decryptN, hex.EncodeToString([]byte(hmacIn[0:])), hTmp)
// Log alert if hmac didn't match, corrupted channel
if !bytes.Equal(hTmp, []byte(hmacIn[0:])) /*|| hmacIn[0] > 0xf8*/ {
logger.LogDebug(fmt.Sprintln("** ALERT - detected HMAC mismatch, possible channel tampering **"))
_, _ = (*hc.c).Write([]byte{CSOHmacInvalid})
}
db := bytes.NewBuffer(payloadBytes[:n]) //copying payloadBytes to db
// The StreamReader acts like a pipe, decrypting
// whatever is available and forwarding the result
@ -1303,7 +1313,6 @@ func (hc Conn) Read(b []byte) (n int, err error) {
log.Println("xsnet.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]
@ -1417,19 +1426,6 @@ func (hc Conn) Read(b []byte) (n int, err error) {
} else {
logger.LogDebug(fmt.Sprintf("[Unknown CSOType:%d]", ctrlStatOp))
}
hTmp := hc.rm.Sum(nil)[0:HMAC_CHK_SZ]
//log.Printf("<%04x) HMAC:(i)%s (c)%02x\r\n", decryptN, hex.EncodeToString([]byte(hmacIn[0:])), hTmp)
if *hc.closeStat == CSETruncCSO {
logger.LogDebug(fmt.Sprintln("[cannot verify HMAC]"))
} else {
// Log alert if hmac didn't match, corrupted channel
if !bytes.Equal(hTmp, []byte(hmacIn[0:])) /*|| hmacIn[0] > 0xf8*/ {
logger.LogDebug(fmt.Sprintln("** ALERT - detected HMAC mismatch, possible channel tampering **"))
_, _ = (*hc.c).Write([]byte{CSOHmacInvalid})
}
}
}
}
@ -1501,25 +1497,19 @@ func (hc *Conn) WritePacket(b []byte, ctrlStatOp byte) (n int, err error) {
log.Printf(" :>ptext:\r\n%s\r\n", hex.Dump(b[0:payloadLen]))
}
// NOTE the code currently uses Authenticate-then-Encrypt, which in block modes
// is insecure; however
// 1) we are using exclusively XOR-stream modes with random padding,
// NOTE releases prior to v0.9 used Authenticate-then-Encrypt,
// which in block modes is insecure; however
// 1) we use exclusively XOR-stream modes with random padding,
// 2) are padding randomly either before or after the real payload, and
// 3) the padding side indicator value itself is part of the ciphertext
// ... thus are not subject to oracle attacks of the type used on SSL
// (see https://link.springer.com/content/pdf/10.1007%2F3-540-44647-8_19.pdf)
// (described in (Krawczyk 2001/2014,
// https://link.springer.com/content/pdf/10.1007%2F3-540-44647-8_19.pdf)
//
// Nevertheless, to address any future concerns this code may switch to
// Encrypt-then-Auth and offer the current scheme as a legacy mode
// (or just issue a breaking release since this is very pre-1.0.)
// Nevertheless, to address any future concerns v0.9 onwards switches to
// Encrypt-then-Auth and breaks interop with earlier versions.
// -rlm 2020-12-15
// Calculate hmac on payload
hc.wm.Write(b[0:payloadLen])
hmacOut = hc.wm.Sum(nil)[0:HMAC_CHK_SZ]
//log.Printf(" (%08x> HMAC(o):%s\r\n", payloadLen, hex.EncodeToString(hmacOut))
var wb bytes.Buffer
// The StreamWriter acts like a pipe, forwarding whatever is
// written to it through the cipher, encrypting as it goes
@ -1532,6 +1522,11 @@ func (hc *Conn) WritePacket(b []byte, ctrlStatOp byte) (n int, err error) {
log.Printf(" ->ctext:\r\n%s\r\n", hex.Dump(wb.Bytes()))
}
// Calculate hmac on cipher payload
hc.wm.Write(wb.Bytes())
hmacOut = hc.wm.Sum(nil)[0:HMAC_CHK_SZ] //finalize
//log.Printf(" (%08x> HMAC(o):%s\r\n", payloadLen, hex.EncodeToString(hmacOut))
err = binary.Write(*hc.c, binary.BigEndian, &ctrlStatOp)
if err == nil {
// Write hmac LSB, payloadLen followed by payload