Reorganize the ciphers crate

ciphers/src/subtle/rust_crypto/blake2b.rs

@@ -0,0 +1,66 @@
+use zeroize::Zeroizing;
+
+use blake2::digest::crypto_common::generic_array::GenericArray;
+use blake2::digest::crypto_common::typenum::U32;
+use blake2::digest::crypto_common::KeySizeUser;
+use blake2::digest::{FixedOutput, Mac, OutputSizeUser};
+use blake2::Blake2bMac;
+
+use rosenpass_to::{ops::copy_slice, with_destination, To};
+use rosenpass_util::typenum2const;
+
+/// Specify that the used implementation of BLAKE2b is the MAC version of BLAKE2b
+/// with output and key length of 32 bytes (see [Blake2bMac]).
+type Impl = Blake2bMac<U32>;
+
+type KeyLen = <Impl as KeySizeUser>::KeySize;
+type OutLen = <Impl as OutputSizeUser>::OutputSize;
+
+/// The key length for BLAKE2b supported by this API. Currently 32 Bytes.
+const KEY_LEN: usize = typenum2const! { KeyLen };
+/// The output length for BLAKE2b supported by this API. Currently 32 Bytes.
+const OUT_LEN: usize = typenum2const! { OutLen };
+
+/// Minimal key length supported by this API.
+pub const KEY_MIN: usize = KEY_LEN;
+/// maximal key length supported by this API.
+pub const KEY_MAX: usize = KEY_LEN;
+/// minimal output length supported by this API.
+pub const OUT_MIN: usize = OUT_LEN;
+/// maximal output length supported by this API.
+pub const OUT_MAX: usize = OUT_LEN;
+
+/// Hashes the given `data` with the [Blake2bMac] hash function under the given `key`.
+/// The both the length of the output the length of the key 32 bytes (or 256 bits).  
+///
+/// TODO: Adapt example
+/// # Examples
+///
+///```rust
+/// # use rosenpass_ciphers::subtle::blake2b::hash;
+/// use rosenpass_to::To;
+/// let zero_key: [u8; 32] = [0; 32];
+/// let data: [u8; 32] = [255; 32];
+/// // buffer for the hash output
+/// let mut hash_data: [u8; 32] = [0u8; 32];  
+///
+/// assert!(hash(&zero_key, &data).to(&mut hash_data).is_ok(), "Hashing has to return OK result");
+///```
+///
+#[inline]
+pub fn hash<'a>(key: &'a [u8], data: &'a [u8]) -> impl To<[u8], anyhow::Result<()>> + 'a {
+    with_destination(|out: &mut [u8]| {
+        let mut h = Impl::new_from_slice(key)?;
+        h.update(data);
+
+        // Jesus christ, blake2 crate, your usage of GenericArray might be nice and fancy,
+        // but it introduces a ton of complexity. This cost me half an hour just to figure
+        // out the right way to use the imports while allowing for zeroization.
+        // An API based on slices might actually be simpler.
+        let mut tmp = Zeroizing::new([0u8; OUT_LEN]);
+        let tmp = GenericArray::from_mut_slice(tmp.as_mut());
+        h.finalize_into(tmp);
+        copy_slice(tmp.as_ref()).to(out);
+        Ok(())
+    })
+}