1 files changed, 44 insertions, 0 deletions
diff --git a/v_windows/v/vlib/crypto/hmac/hmac.v b/v_windows/v/vlib/crypto/hmac/hmac.v
new file mode 100644
index 0000000..3f45467
--- /dev/null
+++ b/v_windows/v/vlib/crypto/hmac/hmac.v
@@ -0,0 +1,44 @@
+// 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
+}