Consolidate keypairs in core. (#972)

* Consolidate keypairs in core.

Introduce the concept of a node's identity keypair in libp2p-core,
instead of only the public key:

  * New module: libp2p_core::identity with submodules for the currently
    supported key types. An identity::Keypair and identity::PublicKey
    support the creation and verification of signatures. The public key
    supports encoding/decoding according to the libp2p specs.

  * The secio protocol is simplified as a result of moving code to libp2p-core.

  * The noise protocol is slightly simplified by consolidating ed25519
    keypairs in libp2p-core and using x25519-dalek for DH. Furthermore,
    Ed25519 to X25519 keypair conversion is now complete and tested.

Generalise over the DH keys in the noise protocol.

Generalise over the DH keys and thus DH parameter in handshake patterns
of the Noise protocol, such that it is easy to support other DH schemes
in the future, e.g. X448.

* Address new review comments.

core/src/identity.rs

@@ -0,0 +1,216 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+//! A node's network identity keys.
+
+pub mod ed25519;
+#[cfg(not(any(target_os = "emscripten", target_os = "unknown")))]
+pub mod rsa;
+#[cfg(feature = "secp256k1")]
+pub mod secp256k1;
+
+pub mod error;
+
+use self::error::*;
+use crate::{PeerId, keys_proto};
+
+/// Identity keypair of a node.
+///
+/// # Example: Generating RSA keys with OpenSSL
+///
+/// ```text
+/// openssl genrsa -out private.pem 2048
+/// openssl pkcs8 -in private.pem -inform PEM -topk8 -out private.pk8 -outform DER -nocrypt
+/// rm private.pem      # optional
+/// ```
+///
+/// Loading the keys:
+///
+/// ```text
+/// let mut bytes = std::fs::read("private.pem").unwrap();
+/// let keypair = Keypair::rsa_from_pkcs8(&mut bytes);
+/// ```
+///
+#[derive(Clone)]
+pub enum Keypair {
+    /// An Ed25519 keypair.
+    Ed25519(ed25519::Keypair),
+    #[cfg(not(any(target_os = "emscripten", target_os = "unknown")))]
+    /// An RSA keypair.
+    Rsa(rsa::Keypair),
+    /// A Secp256k1 keypair.
+    #[cfg(feature = "secp256k1")]
+    Secp256k1(secp256k1::Keypair)
+}
+
+impl Keypair {
+    /// Generate a new Ed25519 keypair.
+    pub fn generate_ed25519() -> Keypair {
+        Keypair::Ed25519(ed25519::Keypair::generate())
+    }
+
+    /// Generate a new Secp256k1 keypair.
+    #[cfg(feature = "secp256k1")]
+    pub fn generate_secp256k1() -> Keypair {
+        Keypair::Secp256k1(secp256k1::Keypair::generate())
+    }
+
+    /// Decode an keypair from a DER-encoded secret key in PKCS#8 PrivateKeyInfo
+    /// format (i.e. unencrypted) as defined in [RFC5208].
+    ///
+    /// [RFC5208]: https://tools.ietf.org/html/rfc5208#section-5
+    #[cfg(not(any(target_os = "emscripten", target_os = "unknown")))]
+    pub fn rsa_from_pkcs8(pkcs8_der: &mut [u8]) -> Result<Keypair, DecodingError> {
+        rsa::Keypair::from_pkcs8(pkcs8_der).map(Keypair::Rsa)
+    }
+
+    /// Decode a keypair from a DER-encoded Secp256k1 secret key in an ECPrivateKey
+    /// structure as defined in [RFC5915].
+    ///
+    /// [RFC5915]: https://tools.ietf.org/html/rfc5915
+    #[cfg(feature = "secp256k1")]
+    pub fn secp256k1_from_der(der: &mut [u8]) -> Result<Keypair, DecodingError> {
+        secp256k1::SecretKey::from_der(der)
+            .map(|sk| Keypair::Secp256k1(secp256k1::Keypair::from(sk)))
+    }
+
+    /// Sign a message using the private key of this keypair, producing
+    /// a signature that can be verified using the corresponding public key.
+    pub fn sign(&self, msg: &[u8]) -> Result<Vec<u8>, SigningError> {
+        use Keypair::*;
+        match self {
+            Ed25519(ref pair) => Ok(pair.sign(msg)),
+            #[cfg(not(any(target_os = "emscripten", target_os = "unknown")))]
+            Rsa(ref pair) => pair.sign(msg),
+            #[cfg(feature = "secp256k1")]
+            Secp256k1(ref pair) => Ok(pair.secret().sign(msg)),
+        }
+    }
+
+    /// Get the public key of this keypair.
+    pub fn public(&self) -> PublicKey {
+        use Keypair::*;
+        match self {
+            Ed25519(pair) => PublicKey::Ed25519(pair.public()),
+            #[cfg(not(any(target_os = "emscripten", target_os = "unknown")))]
+            Rsa(pair) => PublicKey::Rsa(pair.public()),
+            #[cfg(feature = "secp256k1")]
+            Secp256k1(pair) => PublicKey::Secp256k1(pair.public().clone()),
+        }
+    }
+}
+
+/// The public key of a node's identity keypair.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum PublicKey {
+    /// A public Ed25519 key.
+    Ed25519(ed25519::PublicKey),
+    #[cfg(not(any(target_os = "emscripten", target_os = "unknown")))]
+    /// A public RSA key.
+    Rsa(rsa::PublicKey),
+    #[cfg(feature = "secp256k1")]
+    /// A public Secp256k1 key.
+    Secp256k1(secp256k1::PublicKey)
+}
+
+impl PublicKey {
+    /// Verify a signature for a message using this public key, i.e. check
+    /// that the signature has been produced by the corresponding
+    /// private key (authenticity), and that the message has not been
+    /// tampered with (integrity).
+    pub fn verify(&self, msg: &[u8], sig: &[u8]) -> bool {
+        use PublicKey::*;
+        match self {
+            Ed25519(pk) => pk.verify(msg, sig),
+            #[cfg(not(any(target_os = "emscripten", target_os = "unknown")))]
+            Rsa(pk) => pk.verify(msg, sig),
+            #[cfg(feature = "secp256k1")]
+            Secp256k1(pk) => pk.verify(msg, sig)
+        }
+    }
+
+    /// Encode the public key into a protobuf structure for storage or
+    /// exchange with other nodes.
+    pub fn into_protobuf_encoding(self) -> Vec<u8> {
+        use protobuf::Message;
+        let mut public_key = keys_proto::PublicKey::new();
+        match self {
+            PublicKey::Ed25519(key) => {
+                public_key.set_Type(keys_proto::KeyType::Ed25519);
+                public_key.set_Data(key.encode().to_vec());
+            },
+            #[cfg(not(any(target_os = "emscripten", target_os = "unknown")))]
+            PublicKey::Rsa(key) => {
+                public_key.set_Type(keys_proto::KeyType::RSA);
+                public_key.set_Data(key.encode_x509());
+            },
+            #[cfg(feature = "secp256k1")]
+            PublicKey::Secp256k1(key) => {
+                public_key.set_Type(keys_proto::KeyType::Secp256k1);
+                public_key.set_Data(key.encode().to_vec());
+            },
+        };
+
+        public_key
+            .write_to_bytes()
+            .expect("Encoding public key into protobuf failed.")
+    }
+
+    /// Decode a public key from a protobuf structure, e.g. read from storage
+    /// or received from another node.
+    pub fn from_protobuf_encoding(bytes: &[u8]) -> Result<PublicKey, DecodingError> {
+        #[allow(unused_mut)] // Due to conditional compilation.
+        let mut pubkey = protobuf::parse_from_bytes::<keys_proto::PublicKey>(bytes)
+            .map_err(|e| DecodingError::new("Protobuf", e))?;
+
+        match pubkey.get_Type() {
+            keys_proto::KeyType::Ed25519 => {
+                ed25519::PublicKey::decode(pubkey.get_Data())
+                    .map(PublicKey::Ed25519)
+            },
+            #[cfg(not(any(target_os = "emscripten", target_os = "unknown")))]
+            keys_proto::KeyType::RSA => {
+                rsa::PublicKey::decode_x509(&pubkey.take_Data())
+                    .map(PublicKey::Rsa)
+            }
+            #[cfg(any(target_os = "emscripten", target_os = "unknown"))]
+            keys_proto::KeyType::RSA => {
+                log::debug!("support for RSA was disabled at compile-time");
+                Err("Unsupported".to_string().into())
+            },
+            #[cfg(feature = "secp256k1")]
+            keys_proto::KeyType::Secp256k1 => {
+                secp256k1::PublicKey::decode(pubkey.get_Data())
+                    .map(PublicKey::Secp256k1)
+            }
+            #[cfg(not(feature = "secp256k1"))]
+            keys_proto::KeyType::Secp256k1 => {
+                log::debug!("support for secp256k1 was disabled at compile-time");
+                Err("Unsupported".to_string().into())
+            },
+        }
+    }
+
+    /// Convert the `PublicKey` into the corresponding `PeerId`.
+    pub fn into_peer_id(self) -> PeerId {
+        self.into()
+    }
+}
+