103 lines
2.2 KiB
Go
103 lines
2.2 KiB
Go
/* SPDX-License-Identifier: GPL-2.0
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*
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* Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
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*/
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package main
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import (
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"crypto/hmac"
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"crypto/rand"
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"crypto/subtle"
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"golang.org/x/crypto/blake2s"
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"golang.org/x/crypto/curve25519"
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"hash"
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)
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/* KDF related functions.
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* HMAC-based Key Derivation Function (HKDF)
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* https://tools.ietf.org/html/rfc5869
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*/
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func HMAC1(sum *[blake2s.Size]byte, key, in0 []byte) {
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mac := hmac.New(func() hash.Hash {
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h, _ := blake2s.New256(nil)
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return h
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}, key)
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mac.Write(in0)
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mac.Sum(sum[:0])
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}
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func HMAC2(sum *[blake2s.Size]byte, key, in0, in1 []byte) {
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mac := hmac.New(func() hash.Hash {
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h, _ := blake2s.New256(nil)
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return h
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}, key)
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mac.Write(in0)
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mac.Write(in1)
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mac.Sum(sum[:0])
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}
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func KDF1(t0 *[blake2s.Size]byte, key, input []byte) {
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HMAC1(t0, key, input)
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HMAC1(t0, t0[:], []byte{0x1})
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return
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}
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func KDF2(t0, t1 *[blake2s.Size]byte, key, input []byte) {
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var prk [blake2s.Size]byte
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HMAC1(&prk, key, input)
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HMAC1(t0, prk[:], []byte{0x1})
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HMAC2(t1, prk[:], t0[:], []byte{0x2})
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setZero(prk[:])
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return
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}
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func KDF3(t0, t1, t2 *[blake2s.Size]byte, key, input []byte) {
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var prk [blake2s.Size]byte
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HMAC1(&prk, key, input)
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HMAC1(t0, prk[:], []byte{0x1})
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HMAC2(t1, prk[:], t0[:], []byte{0x2})
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HMAC2(t2, prk[:], t1[:], []byte{0x3})
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setZero(prk[:])
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return
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}
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func isZero(val []byte) bool {
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acc := 1
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for _, b := range val {
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acc &= subtle.ConstantTimeByteEq(b, 0)
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}
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return acc == 1
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}
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/* This function is not used as pervasively as it should because this is mostly impossible in Go at the moment */
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func setZero(arr []byte) {
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for i := range arr {
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arr[i] = 0
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}
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}
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func newPrivateKey() (sk NoisePrivateKey, err error) {
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// clamping: https://cr.yp.to/ecdh.html
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_, err = rand.Read(sk[:])
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sk[0] &= 248
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sk[31] &= 127
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sk[31] |= 64
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return
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}
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func (sk *NoisePrivateKey) publicKey() (pk NoisePublicKey) {
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apk := (*[NoisePublicKeySize]byte)(&pk)
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ask := (*[NoisePrivateKeySize]byte)(sk)
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curve25519.ScalarBaseMult(apk, ask)
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return
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}
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func (sk *NoisePrivateKey) sharedSecret(pk NoisePublicKey) (ss [NoisePublicKeySize]byte) {
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apk := (*[NoisePublicKeySize]byte)(&pk)
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ask := (*[NoisePrivateKeySize]byte)(sk)
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curve25519.ScalarMult(&ss, ask, apk)
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return ss
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}
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