From 77c221d941a8180a3c67fc6147ad6d6dddc47097 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=AF=A7=E9=9D=9C?= <luozijun.assistant@protonmail.com>
Date: Tue, 8 Dec 2020 13:37:08 +0800
Subject: [PATCH] fix HKDF-Extract with empty salt #45 (#46)

---
 hkdf/src/hkdf.rs    |  8 +++-----
 hkdf/tests/tests.rs | 14 ++++++++++++--
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/hkdf/src/hkdf.rs b/hkdf/src/hkdf.rs
index e61d658..1a6cfd4 100644
--- a/hkdf/src/hkdf.rs
+++ b/hkdf/src/hkdf.rs
@@ -69,11 +69,9 @@ where
 {
     /// Initiates the HKDF-Extract context with the given optional salt
     pub fn new(salt: Option<&[u8]>) -> HkdfExtract<D> {
-        let hmac = match salt {
-            Some(s) => Hmac::<D>::new_varkey(s).expect("HMAC can take a key of any size"),
-            None => Hmac::<D>::new(&Default::default()),
-        };
-
+        let default_salt = GenericArray::<u8, D::OutputSize>::default();
+        let salt = salt.unwrap_or(&default_salt);
+        let hmac = Hmac::<D>::new_varkey(salt).expect("HMAC can take a key of any size");
         HkdfExtract { hmac }
     }
 
diff --git a/hkdf/tests/tests.rs b/hkdf/tests/tests.rs
index 7257923..6b18e0d 100644
--- a/hkdf/tests/tests.rs
+++ b/hkdf/tests/tests.rs
@@ -65,7 +65,12 @@ fn test_derive_sha256() {
         let ikm = hex::decode(&t.ikm).unwrap();
         let salt = hex::decode(&t.salt).unwrap();
         let info = hex::decode(&t.info).unwrap();
-        let (prk, hkdf) = Hkdf::<Sha256>::extract(Option::from(&salt[..]), &ikm[..]);
+        let salt = if salt.is_empty() {
+            None
+        } else {
+            Some(&salt[..])
+        };
+        let (prk, hkdf) = Hkdf::<Sha256>::extract(salt, &ikm[..]);
         let mut okm = vec![0u8; t.length];
         assert!(hkdf.expand(&info[..], &mut okm).is_ok());
 
@@ -204,7 +209,12 @@ fn test_derive_sha1() {
         let ikm = hex::decode(&t.ikm).unwrap();
         let salt = hex::decode(&t.salt).unwrap();
         let info = hex::decode(&t.info).unwrap();
-        let (prk, hkdf) = Hkdf::<Sha1>::extract(Some(&salt[..]), &ikm[..]);
+        let salt = if salt.is_empty() {
+            None
+        } else {
+            Some(&salt[..])
+        };
+        let (prk, hkdf) = Hkdf::<Sha1>::extract(salt, &ikm[..]);
         let mut okm = vec![0u8; t.length];
         assert!(hkdf.expand(&info[..], &mut okm).is_ok());