mirror of https://gogs.blitter.com/RLabs/xs
114 lines
3.4 KiB
Go
114 lines
3.4 KiB
Go
package hkexnet
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// Copyright (c) 2017-2018 Russell Magee
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// Licensed under the terms of the MIT license (see LICENSE.mit in this
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// distribution)
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//
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// golang implementation by Russ Magee (rmagee_at_gmail.com)
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/* Support functions to set up encryption once an HKEx Conn has been
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established with FA exchange and support channel operations
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(echo, file-copy, remote-cmd, ...) */
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import (
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"crypto"
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"crypto/aes"
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"crypto/cipher"
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"encoding/hex"
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"errors"
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"fmt"
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"hash"
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"log"
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"math/big"
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"golang.org/x/crypto/blowfish"
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"golang.org/x/crypto/twofish"
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// hash algos must be manually imported thusly:
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// (Would be nice if the golang pkg docs were more clear
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// on this...)
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_ "crypto/sha256"
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)
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/* Support functionality to set up encryption after a channel has
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been negotiated via hkexnet.go
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*/
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func (hc Conn) getStream(keymat *big.Int) (rc cipher.Stream, mc hash.Hash, err error) {
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var key []byte
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var block cipher.Block
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var iv []byte
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var ivlen int
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copts := hc.cipheropts & 0xFF
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// TODO: each cipher alg case should ensure len(keymat.Bytes())
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// is >= 2*cipher.BlockSize (enough for both key and iv)
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switch copts {
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case CAlgAES256:
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key = keymat.Bytes()[0:aes.BlockSize]
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block, err = aes.NewCipher(key)
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ivlen = aes.BlockSize
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iv = keymat.Bytes()[aes.BlockSize : aes.BlockSize+ivlen]
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rc = cipher.NewOFB(block, iv)
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log.Printf("[cipher AES_256 (%d)]\n", copts)
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break
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case CAlgTwofish128:
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key = keymat.Bytes()[0:twofish.BlockSize]
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block, err = twofish.NewCipher(key)
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ivlen = twofish.BlockSize
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iv = keymat.Bytes()[twofish.BlockSize : twofish.BlockSize+ivlen]
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rc = cipher.NewOFB(block, iv)
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log.Printf("[cipher TWOFISH_128 (%d)]\n", copts)
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break
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case CAlgBlowfish64:
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key = keymat.Bytes()[0:blowfish.BlockSize]
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block, err = blowfish.NewCipher(key)
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ivlen = blowfish.BlockSize
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// N.b. Bounds enforcement of differing cipher algorithms
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// ------------------------------------------------------
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// cipher/aes and x/cipher/twofish appear to allow one to
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// pass an iv larger than the blockSize harmlessly to
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// cipher.NewOFB(); x/cipher/blowfish implementation will
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// segfault here if len(iv) is not exactly blowfish.BlockSize.
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//
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// I assume the other two check bounds and only
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// copy what's needed whereas blowfish does no such check.
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iv = keymat.Bytes()[blowfish.BlockSize : blowfish.BlockSize+ivlen]
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rc = cipher.NewOFB(block, iv)
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log.Printf("[cipher BLOWFISH_64 (%d)]\n", copts)
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break
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default:
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log.Printf("[invalid cipher (%d)]\n", copts)
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fmt.Printf("DOOFUS SET A VALID CIPHER ALG (%d)\n", copts)
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err = errors.New("hkexchan: INVALID CIPHER ALG")
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//os.Exit(1)
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}
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hopts := (hc.cipheropts >> 8) & 0xFF
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switch hopts {
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case HmacSHA256:
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log.Printf("[hash HmacSHA256 (%d)]\n", hopts)
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halg := crypto.SHA256
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mc = halg.New()
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if !halg.Available() {
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log.Fatal("hash not available!")
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}
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break
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default:
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log.Printf("[invalid hmac (%d)]\n", hopts)
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fmt.Printf("DOOFUS SET A VALID HMAC ALG (%d)\n", hopts)
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err = errors.New("hkexchan: INVALID HMAC ALG")
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return
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//os.Exit(1)
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}
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if err != nil {
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// Feed the IV into the hmac: all traffic in the connection must
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// feed its data into the hmac afterwards, so both ends can xor
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// that with the stream to detect corruption.
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_, _ = mc.Write(iv)
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var currentHash []byte
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currentHash = mc.Sum(currentHash)
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log.Printf("Channel init hmac(iv):%s\n", hex.EncodeToString(currentHash))
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}
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return
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}
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