forked from quic-go/quic-go
/
hkdf.go
56 lines (49 loc) · 1.25 KB
/
hkdf.go
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package crypto
import (
"crypto"
"crypto/hmac"
"encoding/binary"
)
// copied from https://github.com/cloudflare/tls-tris/blob/master/hkdf.go
func hkdfExtract(hash crypto.Hash, secret, salt []byte) []byte {
if salt == nil {
salt = make([]byte, hash.Size())
}
if secret == nil {
secret = make([]byte, hash.Size())
}
extractor := hmac.New(hash.New, salt)
extractor.Write(secret)
return extractor.Sum(nil)
}
// copied from https://github.com/cloudflare/tls-tris/blob/master/hkdf.go
func hkdfExpand(hash crypto.Hash, prk, info []byte, l int) []byte {
var (
expander = hmac.New(hash.New, prk)
res = make([]byte, l)
counter = byte(1)
prev []byte
)
if l > 255*expander.Size() {
panic("hkdf: requested too much output")
}
p := res
for len(p) > 0 {
expander.Reset()
expander.Write(prev)
expander.Write(info)
expander.Write([]byte{counter})
prev = expander.Sum(prev[:0])
counter++
n := copy(p, prev)
p = p[n:]
}
return res
}
func qhkdfExpand(secret []byte, label string, length int) []byte {
qlabel := make([]byte, 2+1+5+len(label))
binary.BigEndian.PutUint16(qlabel[0:2], uint16(length))
qlabel[2] = uint8(5 + len(label))
copy(qlabel[3:], []byte("QUIC "+label))
return hkdfExpand(crypto.SHA256, secret, qlabel, length)
}