check the HMAC output bytes

1 files changed, 47 insertions, 2 deletions

diff --git a/src/traits.rs b/src/traits.rs
index 14b0f55..70b1c06 100644
--- a/src/traits.rs
+++ b/src/traits.rs
@@ -171,12 +171,57 @@ mod test {
         assert_eq!(out1.as_bytes(), out2.into_bytes().as_slice());
     }
 
+    fn expected_hmac_blake3(key: &[u8], input: &[u8]) -> [u8; 32] {
+        // See https://en.wikipedia.org/wiki/HMAC.
+        let key_hash;
+        let key_prime = if key.len() <= 64 {
+            key
+        } else {
+            key_hash = *crate::hash(key).as_bytes();
+            &key_hash
+        };
+        let mut ipad = [0x36; 64];
+        let mut opad = [0x5c; 64];
+        for i in 0..key_prime.len() {
+            ipad[i] ^= key_prime[i];
+            opad[i] ^= key_prime[i];
+        }
+        let mut inner_state = crate::Hasher::new();
+        inner_state.update(&ipad);
+        inner_state.update(input);
+        let mut outer_state = crate::Hasher::new();
+        outer_state.update(&opad);
+        outer_state.update(inner_state.finalize().as_bytes());
+        outer_state.finalize().into()
+    }
+
     #[test]
     fn test_hmac_compatibility() {
-        use hmac::{SimpleHmac, Mac};
+        use hmac::{Mac, SimpleHmac};
 
+        // Test a short key.
         let mut x = SimpleHmac::<Hasher>::new_from_slice(b"key").unwrap();
         hmac::digest::Update::update(&mut x, b"data");
-        assert_ne!(x.finalize().into_bytes().len(), 0);
+        let output = x.finalize().into_bytes();
+        assert_ne!(output.len(), 0);
+        let expected = expected_hmac_blake3(b"key", b"data");
+        assert_eq!(expected, output.as_ref());
+
+        // Test a range of key and data lengths, particularly to exercise the long-key logic.
+        let mut input_bytes = [0; crate::test::TEST_CASES_MAX];
+        crate::test::paint_test_input(&mut input_bytes);
+        for &input_len in crate::test::TEST_CASES {
+            #[cfg(feature = "std")]
+            dbg!(input_len);
+            let input = &input_bytes[..input_len];
+
+            let mut x = SimpleHmac::<Hasher>::new_from_slice(input).unwrap();
+            hmac::digest::Update::update(&mut x, input);
+            let output = x.finalize().into_bytes();
+            assert_ne!(output.len(), 0);
+
+            let expected = expected_hmac_blake3(input, input);
+            assert_eq!(expected, output.as_ref());
+        }
     }
 }