Add SlowHash configuration (#234)

* Add `SlowHash` configuration

* Use a reference

* Changing generic argument to be CipherSuite instead of SlowHash

Co-authored-by: Kevin Lewi <[email protected]>

src/slow_hash.rs

@@ -13,33 +13,35 @@ use generic_array::typenum::Unsigned;
 use generic_array::GenericArray;
 
 /// Used for the slow hashing function in OPAQUE
-pub trait SlowHash<D: Hash> {
+pub trait SlowHash<D: Hash>: Default {
     /// Computes the slow hashing function
-    fn hash(input: GenericArray<u8, <D as Digest>::OutputSize>) -> Result<Vec<u8>, InternalError>;
+    fn hash(
+        &self,
+        input: GenericArray<u8, <D as Digest>::OutputSize>,
+    ) -> Result<Vec<u8>, InternalError>;
 }
 
 /// A no-op hash which simply returns its input
+#[derive(Default)]
 pub struct NoOpHash;
 
 impl<D: Hash> SlowHash<D> for NoOpHash {
-    fn hash(input: GenericArray<u8, <D as Digest>::OutputSize>) -> Result<Vec<u8>, InternalError> {
+    fn hash(
+        &self,
+        input: GenericArray<u8, <D as Digest>::OutputSize>,
+    ) -> Result<Vec<u8>, InternalError> {
         Ok(input.to_vec())
     }
 }
 
 #[cfg(feature = "slow-hash")]
 impl<D: Hash> SlowHash<D> for argon2::Argon2<'_> {
-    fn hash(input: GenericArray<u8, <D as Digest>::OutputSize>) -> Result<Vec<u8>, InternalError> {
-        let params = argon2::Argon2::default();
+    fn hash(
+        &self,
+        input: GenericArray<u8, <D as Digest>::OutputSize>,
+    ) -> Result<Vec<u8>, InternalError> {
         let mut output = alloc::vec![0u8; <D as Digest>::OutputSize::USIZE];
-        params
-            .hash_password_into(
-                argon2::Algorithm::Argon2id,
-                &input,
-                &[0; argon2::MIN_SALT_LENGTH],
-                &[],
-                &mut output,
-            )
+        self.hash_password_into(&input, &[0; argon2::MIN_SALT_LEN], &mut output)
             .map_err(|_| InternalError::SlowHashError)?;
         Ok(output)
     }