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// HMAC: Keyed-Hashing for Message Authentication implemented in v
// implementation based on https://tools.ietf.org/html/rfc2104
module hmac
import crypto.internal.subtle
const (
ipad = []byte{len: 256, init: 0x36} // TODO is 256 enough??
opad = []byte{len: 256, init: 0x5C}
npad = []byte{len: 256, init: 0}
)
// new returns a HMAC byte array, depending on the hash algorithm used.
pub fn new(key []byte, data []byte, hash_func fn ([]byte) []byte, blocksize int) []byte {
mut b_key := []byte{}
if key.len <= blocksize {
b_key = key.clone() // TODO: remove .clone() once https://github.com/vlang/v/issues/6604 gets fixed
} else {
b_key = hash_func(key)
}
if b_key.len < blocksize {
b_key << hmac.npad[..blocksize - b_key.len]
}
mut inner := []byte{}
for i, b in hmac.ipad[..blocksize] {
inner << b_key[i] ^ b
}
inner << data
inner_hash := hash_func(inner)
mut outer := []byte{cap: b_key.len}
for i, b in hmac.opad[..blocksize] {
outer << b_key[i] ^ b
}
outer << inner_hash
digest := hash_func(outer)
return digest
}
// equal compares 2 MACs for equality, without leaking timing info.
// NB: if the lengths of the 2 MACs are different, probably a completely different
// hash function was used to generate them => no useful timing information.
pub fn equal(mac1 []byte, mac2 []byte) bool {
return subtle.constant_time_compare(mac1, mac2) == 1
}
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