xs/hkexchan.go

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/* Herradura - a Key exchange scheme in the style of Diffie-Hellman Key Exchange.
Copyright (C) 2017 Omar Alejandro Herrera Reyna
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
golang implementation by Russ Magee (rmagee_at_gmail.com) */
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package herradurakex
/* Support functions to set up encryption once an HKEx Conn has been
established with FA exchange */
import (
"crypto/aes"
"crypto/cipher"
"fmt"
"math/big"
"os"
"golang.org/x/crypto/twofish"
)
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// Available ciphers for hkex.Conn
const (
C_AES_256 = iota
C_TWOFISH_128 // golang.org/x/crypto/twofish
C_NONE_DISALLOWED
)
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// Available HMACs for hkex.Conn (TODO: not currently used)
const (
H_BOGUS = iota
H_SHA256
H_NONE_DISALLOWED
)
/*TODO: HMAC derived from HKEx FA.*/
/* Support functionality to set up encryption after a channel has
been negotiated via hkexnet.go
*/
func (hc Conn) getStream(keymat *big.Int) (ret cipher.Stream) {
var key []byte
var block cipher.Block
var err error
copts := hc.cipheropts & 0xFF
switch copts {
case C_AES_256:
key = keymat.Bytes()[0:aes.BlockSize]
block, err = aes.NewCipher(key)
iv := make([]byte, aes.BlockSize)
//if _, err = io.ReadFull(crand.Reader, iv); err != nil {
// panic(err)
//}
iv = keymat.Bytes()[aes.BlockSize:]
ret = cipher.NewOFB(block, iv)
fmt.Printf("[cipher AES_256 (%d)]\n", copts)
break
case C_TWOFISH_128:
key = keymat.Bytes()[0:twofish.BlockSize]
block, err = twofish.NewCipher(key)
iv := make([]byte, twofish.BlockSize)
//if _, err = io.ReadFull(crand.Reader, iv); err != nil {
// panic(err)
//}
iv = keymat.Bytes()[twofish.BlockSize:]
ret = cipher.NewOFB(block, iv)
fmt.Printf("[cipher TWOFISH_256 (%d)]\n", copts)
break
default:
fmt.Printf("DOOFUS SET A VALID CIPHER ALG (%d)\n", copts)
block, err = nil, nil
os.Exit(1)
}
hopts := (hc.cipheropts >> 8) & 0xFF
switch hopts {
case H_BOGUS:
fmt.Printf("[nop H_BOGUS (%d)]\n", hopts)
break
case H_SHA256:
fmt.Printf("[nop H_SHA256 (%d)]\n", hopts)
break
default:
fmt.Printf("DOOFUS SET A VALID HMAC ALG (%d)\n", hopts)
os.Exit(1)
}
if err != nil {
panic(err)
}
return
}