Store key instead of byte array of the key in filename decoder

rustcryptfs-lib/src/filename.rs

@@ -1,12 +1,14 @@
 use aes::Aes256;
-use cipher::{block_padding::Pkcs7, KeyIvInit};
-use eme_mode::DynamicEme;
+use cipher::{block_padding::Pkcs7, Iv, Key, KeyIvInit};
+use eme_mode::{DynamicEme};
 use hkdf::Hkdf;
 
 use crate::error::FilenameDecryptError;
 
+type EmeCipher = DynamicEme<Aes256>;
+
 pub struct FilenameDecoder {
-    filename_key: [u8; 32],
+    filename_key: Key<Aes256>,
 }
 
 impl FilenameDecoder {
@@ -15,10 +17,13 @@ impl FilenameDecoder {
         let hdkf = Hkdf::<sha2::Sha256>::new(None, &master_key);
         hdkf.expand(b"EME filename encryption", &mut key)?;
 
-        Ok(Self { filename_key: key })
+        Ok(Self {
+            filename_key: Key::<EmeCipher>::from(key),
+        })
     }
 
     pub fn get_decoder_for_dir<'a, 'b>(&'a self, iv: &'b [u8]) -> DirFilenameDecoder<'a, 'b> {
+        let iv = Iv::<EmeCipher>::from_slice(iv);
         DirFilenameDecoder {
             filename_key: &self.filename_key,
             iv,
@@ -27,14 +32,13 @@ impl FilenameDecoder {
 }
 
 pub struct DirFilenameDecoder<'a, 'b> {
-    filename_key: &'a [u8],
-    iv: &'b [u8],
+    filename_key: &'a Key<EmeCipher>,
+    iv: &'b Iv<EmeCipher>,
 }
 
 impl<'a, 'b> DirFilenameDecoder<'a, 'b> {
     pub fn decode_filename(&self, name: &str) -> Result<String, FilenameDecryptError> {
-        let cipher = DynamicEme::<Aes256>::new_from_slices(self.filename_key, self.iv)
-            .expect("failed to get filename cipher");
+        let cipher = EmeCipher::new(self.filename_key, self.iv);
 
         let mut filename = base64::decode_config(name, base64::URL_SAFE)?;
         let filename_decoded = cipher