Add another ExpandedKey derivation for Offers

[rust-lightning] / lightning / src / util / crypto.rs

diff --git a/lightning/src/util/crypto.rs b/lightning/src/util/crypto.rs
index 2f2d33b29f7ea53c0a2dda084ac7a139583c6345..39dfd39b785b048535163756ddc417ff80009ed4 100644 (file)
--- a/lightning/src/util/crypto.rs
+++ b/lightning/src/util/crypto.rs
@@ -20,13 +20,18 @@ macro_rules! hkdf_extract_expand {
                let (k1, k2, _) = hkdf_extract_expand!($salt, $ikm);
                (k1, k2)
        }};
-       ($salt: expr, $ikm: expr, 3) => {{
+       ($salt: expr, $ikm: expr, 4) => {{
                let (k1, k2, prk) = hkdf_extract_expand!($salt, $ikm);
 
                let mut hmac = HmacEngine::<Sha256>::new(&prk[..]);
                hmac.input(&k2);
                hmac.input(&[3; 1]);
-               (k1, k2, Hmac::from_engine(hmac).into_inner())
+               let k3 = Hmac::from_engine(hmac).into_inner();
+
+               let mut hmac = HmacEngine::<Sha256>::new(&prk[..]);
+               hmac.input(&k3);
+               hmac.input(&[4; 1]);
+               (k1, k2, k3, Hmac::from_engine(hmac).into_inner())
        }}
 }
 
@@ -34,8 +39,8 @@ pub fn hkdf_extract_expand_twice(salt: &[u8], ikm: &[u8]) -> ([u8; 32], [u8; 32]
        hkdf_extract_expand!(salt, ikm, 2)
 }
 
-pub fn hkdf_extract_expand_thrice(salt: &[u8], ikm: &[u8]) -> ([u8; 32], [u8; 32], [u8; 32]) {
-       hkdf_extract_expand!(salt, ikm, 3)
+pub fn hkdf_extract_expand_4x(salt: &[u8], ikm: &[u8]) -> ([u8; 32], [u8; 32], [u8; 32], [u8; 32]) {
+       hkdf_extract_expand!(salt, ikm, 4)
 }
 
 #[inline]