72 lines
1.6 KiB
Go
72 lines
1.6 KiB
Go
package main
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import (
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"crypto/hmac"
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"crypto/rand"
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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 HMAC(sum *[blake2s.Size]byte, key []byte, input []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(input)
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mac.Sum(sum[:0])
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}
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func KDF1(key []byte, input []byte) (t0 [blake2s.Size]byte) {
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HMAC(&t0, key, input)
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HMAC(&t0, t0[:], []byte{0x1})
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return
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}
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func KDF2(key []byte, input []byte) (t0 [blake2s.Size]byte, t1 [blake2s.Size]byte) {
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var prk [blake2s.Size]byte
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HMAC(&prk, key, input)
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HMAC(&t0, prk[:], []byte{0x1})
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HMAC(&t1, prk[:], append(t0[:], 0x2))
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return
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}
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func KDF3(key []byte, input []byte) (t0 [blake2s.Size]byte, t1 [blake2s.Size]byte, t2 [blake2s.Size]byte) {
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var prk [blake2s.Size]byte
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HMAC(&prk, key, input)
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HMAC(&t0, prk[:], []byte{0x1})
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HMAC(&t1, prk[:], append(t0[:], 0x2))
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HMAC(&t2, prk[:], append(t1[:], 0x3))
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return
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}
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/* curve25519 wrappers */
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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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