Improve bls::SecretKey privacy (#1164)

* Improve bls::SecretKey privacy

* Add missed file

* Remove more methods from bls::SecretKey

* Add as_bytes() to SecretKey, remove as_raw

* Remove as_raw

* Add back as_raw

* Address review comments

crypto/eth2_keystore/src/keystore.rs

@@ -6,7 +6,7 @@ use crate::json_keystore::{
     Aes128Ctr, ChecksumModule, Cipher, CipherModule, Crypto, EmptyMap, EmptyString, JsonKeystore,
     Kdf, KdfModule, Scrypt, Sha256Checksum, Version,
 };
-use crate::plain_text::PlainText;
+use crate::PlainText;
 use crate::Uuid;
 use bls::{Keypair, PublicKey, SecretKey};
 use crypto::{digest::Digest, sha2::Sha256};
@@ -130,7 +130,7 @@ impl Keystore {
         uuid: Uuid,
         path: String,
     ) -> Result<Self, Error> {
-        let secret = PlainText::from(keypair.sk.as_raw().as_bytes());
+        let secret: PlainText = keypair.sk.as_bytes();
 
         let (cipher_text, checksum) = encrypt(secret.as_bytes(), password, &kdf, &cipher)?;
 

crypto/eth2_keystore/src/lib.rs

@@ -3,13 +3,12 @@
 
 mod derived_key;
 mod keystore;
-mod plain_text;
 
 pub mod json_keystore;
 
+pub use bls::PlainText;
 pub use keystore::{
     decrypt, default_kdf, encrypt, keypair_from_secret, Error, Keystore, KeystoreBuilder, DKLEN,
     HASH_SIZE, IV_SIZE, SALT_SIZE,
 };
-pub use plain_text::PlainText;
 pub use uuid::Uuid;

crypto/eth2_keystore/src/plain_text.rs

@@ -1,34 +0,0 @@
-use zeroize::Zeroize;
-
-/// Provides wrapper around `Vec<u8>` that implements `Zeroize`.
-#[derive(Zeroize, Clone, PartialEq)]
-#[zeroize(drop)]
-pub struct PlainText(Vec<u8>);
-
-impl PlainText {
-    /// Instantiate self with `len` zeros.
-    pub fn zero(len: usize) -> Self {
-        Self(vec![0; len])
-    }
-
-    /// The byte-length of `self`
-    pub fn len(&self) -> usize {
-        self.0.len()
-    }
-
-    /// Returns a reference to the underlying bytes.
-    pub fn as_bytes(&self) -> &[u8] {
-        &self.0
-    }
-
-    /// Returns a mutable reference to the underlying bytes.
-    pub fn as_mut_bytes(&mut self) -> &mut [u8] {
-        &mut self.0
-    }
-}
-
-impl From<Vec<u8>> for PlainText {
-    fn from(vec: Vec<u8>) -> Self {
-        Self(vec)
-    }
-}