[whisper] Move needed aes_gcm crypto in-crate (#10647)

In the latest `parity-crypto` release (upcoming 0.4), the aes GCM features were removed (done to remove the dependency on `ring`).
This PR adds the bare minimum crypto needed for Whisper directly to the crate itself and as those were the only features needed from `parity-crypto`, removes the dependency on that crate altogether.

whisper/src/aes_gcm/mod.rs

@@ -0,0 +1,113 @@
+// Copyright 2015-2019 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use ring;
+
+/// AES GCM encryptor.
+pub struct Encryptor<'a> {
+    key: ring::aead::SealingKey,
+    ad: &'a [u8],
+    offset: usize,
+}
+
+impl<'a> Encryptor<'a> {
+    pub fn aes_256_gcm(key: &[u8; 32]) -> Result<Encryptor<'a>, ring::error::Unspecified> {
+        let sk = ring::aead::SealingKey::new(&ring::aead::AES_256_GCM, key)?;
+        Ok(Encryptor {
+            key: sk,
+            ad: &[],
+            offset: 0,
+        })
+    }
+
+    /// Optional offset value. Only the slice `[offset..]` will be encrypted.
+    pub fn offset(&mut self, off: usize) -> &mut Self {
+        self.offset = off;
+        self
+    }
+
+    /// Please note that the pair (key, nonce) must never be reused. Using random nonces
+    /// limits the number of messages encrypted with the same key to 2^32 (cf. [[1]])
+    ///
+    /// [1]: https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf
+    pub fn encrypt(&self, nonce: &[u8; 12], mut data: Vec<u8>) -> Result<Vec<u8>, ring::error::Unspecified> {
+        if self.offset > data.len() {
+            return Err(ring::error::Unspecified)
+        }
+        let tag_len = ring::aead::AES_256_GCM.tag_len();
+        data.extend(::std::iter::repeat(0).take(tag_len));
+        let nonce = ring::aead::Nonce::assume_unique_for_key(*nonce);
+        let aad = ring::aead::Aad::from(self.ad);
+        let len = ring::aead::seal_in_place(&self.key, nonce, aad, &mut data[self.offset ..], tag_len)?;
+        data.truncate(self.offset + len);
+        Ok(data)
+    }
+}
+
+/// AES GCM decryptor.
+pub struct Decryptor<'a> {
+    key: ring::aead::OpeningKey,
+    ad: &'a [u8],
+    offset: usize,
+}
+
+impl<'a> Decryptor<'a> {
+    pub fn aes_256_gcm(key: &[u8; 32]) -> Result<Decryptor<'a>, ring::error::Unspecified> {
+        let ok = ring::aead::OpeningKey::new(&ring::aead::AES_256_GCM, key)?;
+        Ok(Decryptor {
+            key: ok,
+            ad: &[],
+            offset: 0,
+        })
+    }
+
+    pub fn decrypt(&self, nonce: &[u8; 12], mut data: Vec<u8>) -> Result<Vec<u8>, ring::error::Unspecified> {
+        if self.offset > data.len() {
+            return Err(ring::error::Unspecified)
+        }
+        let nonce = ring::aead::Nonce::assume_unique_for_key(*nonce);
+        let aad = ring::aead::Aad::from(self.ad);
+        let len = ring::aead::open_in_place(&self.key, nonce, aad, 0, &mut data[self.offset ..])?.len();
+        data.truncate(self.offset + len);
+        Ok(data)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{Encryptor, Decryptor};
+
+    #[test]
+    fn aes_gcm_256() {
+        let secret = b"12345678901234567890123456789012";
+        let nonce = b"123456789012";
+        let message = b"So many books, so little time";
+
+        let ciphertext = Encryptor::aes_256_gcm(secret)
+            .unwrap()
+            .encrypt(nonce, message.to_vec())
+            .unwrap();
+
+        assert!(ciphertext != message);
+
+        let plaintext = Decryptor::aes_256_gcm(secret)
+            .unwrap()
+            .decrypt(nonce, ciphertext)
+            .unwrap();
+
+        assert_eq!(plaintext, message)
+    }
+}

whisper/src/lib.rs

@@ -20,7 +20,6 @@
 #![cfg_attr(feature = "time_checked_add", feature(time_checked_add))]
 
 extern crate byteorder;
-extern crate parity_crypto as crypto;
 extern crate ethcore_network as network;
 extern crate ethereum_types;
 extern crate ethkey;
@@ -29,6 +28,7 @@ extern crate memzero;
 extern crate ordered_float;
 extern crate parking_lot;
 extern crate rand;
+extern crate ring;
 extern crate rlp;
 extern crate serde;
 extern crate slab;
@@ -60,3 +60,5 @@ pub use self::net::{Network, MessageHandler};
 pub mod message;
 pub mod net;
 pub mod rpc;
+
+mod aes_gcm;

whisper/src/rpc/crypto.rs

@@ -16,7 +16,7 @@
 
 //! Encryption schemes supported by RPC layer.
 
-use crypto::aes_gcm::{Encryptor, Decryptor};
+use aes_gcm::{Encryptor, Decryptor};
 use ethkey::crypto::ecies;
 use ethereum_types::H256;
 use ethkey::{self, Public, Secret};
@@ -77,7 +77,7 @@ impl EncryptionInstance {
 			EncryptionInner::AES(key, nonce, encode) => {
 				match encode {
 					AesEncode::AppendedNonce => {
-						let mut enc = Encryptor::aes_256_gcm(&*key).ok()?;
+						let enc = Encryptor::aes_256_gcm(&*key).ok()?;
 						let mut buf = enc.encrypt(&nonce, plain.to_vec()).ok()?;
 						buf.extend(&nonce[..]);
 						Some(buf)