Support multiple BLS implementations (#1335)

## Issue Addressed

NA

## Proposed Changes

- Refactor the `bls` crate to support multiple BLS "backends" (e.g., milagro, blst, etc).
- Removes some duplicate, unused code in `common/rest_types/src/validator.rs`.
- Removes the old "upgrade legacy keypairs" functionality (these were unencrypted keys that haven't been supported for a few testnets, no one should be using them anymore).

## Additional Info

Most of the files changed are just inconsequential changes to function names.

## TODO

- [x] Optimization levels
- [x] Infinity point: https://github.com/supranational/blst/issues/11
- [x] Ensure milagro *and* blst are tested via CI
- [x] What to do with unsafe code?
- [x] Test infinity point in signature sets

common/validator_dir/src/builder.rs

@@ -170,7 +170,7 @@ impl<'a> Builder<'a> {
                     pubkey: voting_keypair.pk.clone().into(),
                     withdrawal_credentials,
                     amount,
-                    signature: Signature::empty_signature().into(),
+                    signature: Signature::empty().into(),
                 };
 
                 deposit_data.signature = deposit_data.create_signature(&voting_keypair.sk, &spec);
@@ -220,7 +220,7 @@ impl<'a> Builder<'a> {
                 // Write the withdrawal password to file.
                 write_password_to_file(
                     self.password_dir
-                        .join(withdrawal_keypair.pk.as_hex_string()),
+                        .join(withdrawal_keypair.pk.to_hex_string()),
                     withdrawal_password.as_bytes(),
                 )?;
 

common/validator_dir/src/lib.rs

@@ -10,7 +10,6 @@
 mod builder;
 pub mod insecure_keys;
 mod manager;
-pub mod unencrypted_keys;
 mod validator_dir;
 
 pub use crate::validator_dir::{Error, Eth1DepositData, ValidatorDir, ETH1_DEPOSIT_TX_HASH_FILE};

common/validator_dir/src/manager.rs

@@ -107,14 +107,14 @@ impl Manager {
                             info!(
                                 log,
                                 "Decrypted validator keystore";
-                                "voting_pubkey" => kp.pk.as_hex_string()
+                                "voting_pubkey" => kp.pk.to_hex_string()
                             );
                             if lockfile_existed {
                                 warn!(
                                     log,
                                     "Lockfile already existed";
                                     "msg" => "ensure no other validator client is running on this host",
-                                    "voting_pubkey" => kp.pk.as_hex_string()
+                                    "voting_pubkey" => kp.pk.to_hex_string()
                                 );
                             }
                         }
@@ -147,7 +147,7 @@ impl Manager {
                             info!(
                                 log,
                                 "Decrypted validator keystore";
-                                "voting_pubkey" => kp.pk.as_hex_string()
+                                "voting_pubkey" => kp.pk.to_hex_string()
                             )
                         }
                         (kp, v)

common/validator_dir/src/unencrypted_keys.rs

@@ -1,48 +0,0 @@
-//! The functionality in this module is only required for backward compatibility with the old
-//! method of key generation (unencrypted, SSZ-encoded keypairs). It should be removed as soon as
-//! we're confident that no-one is using these keypairs anymore (hopefully mid-June 2020).
-#![cfg(feature = "unencrypted_keys")]
-
-use bls::{BLS_PUBLIC_KEY_BYTE_SIZE as PK_LEN, BLS_SECRET_KEY_BYTE_SIZE as SK_LEN};
-use eth2_keystore::PlainText;
-use std::fs::File;
-use std::io::Read;
-use std::path::Path;
-use types::{Keypair, PublicKey, SecretKey};
-
-/// Read a keypair from disk, using the old format where keys were stored as unencrypted
-/// SSZ-encoded keypairs.
-///
-/// This only exists as compatibility with the old scheme and should not be implemented on any new
-/// features.
-pub fn load_unencrypted_keypair<P: AsRef<Path>>(path: P) -> Result<Keypair, String> {
-    let path = path.as_ref();
-
-    if !path.exists() {
-        return Err(format!("Keypair file does not exist: {:?}", path));
-    }
-
-    let mut bytes = vec![];
-
-    File::open(&path)
-        .map_err(|e| format!("Unable to open keypair file: {}", e))?
-        .read_to_end(&mut bytes)
-        .map_err(|e| format!("Unable to read keypair file: {}", e))?;
-
-    let bytes: PlainText = bytes.into();
-
-    if bytes.len() != PK_LEN + SK_LEN {
-        return Err(format!("Invalid keypair byte length: {}", bytes.len()));
-    }
-
-    let pk_bytes = &bytes.as_bytes()[..PK_LEN];
-    let sk_bytes = &bytes.as_bytes()[PK_LEN..];
-
-    let pk = PublicKey::from_bytes(pk_bytes)
-        .map_err(|e| format!("Unable to decode public key: {:?}", e))?;
-
-    let sk = SecretKey::from_bytes(sk_bytes)
-        .map_err(|e| format!("Unable to decode secret key: {:?}", e))?;
-
-    Ok(Keypair { pk, sk })
-}