Babe VRF Signing in keystore (#6225)

* Introduce trait

* Implement VRFSigner in keystore

* Use vrf_sign from keystore

* Convert output to VRFInOut

* Simplify conversion

* vrf_sign secondary slot using keystore

* Fix RPC call to claim_slot

* Use Public instead of Pair

* Check primary threshold in signer

* Fix interface to return error

* Move vrf_sign to BareCryptoStore

* Fix authorship_works test

* Fix BABE logic leaks

* Acquire a read lock once

* Also fix RPC acquiring the read lock once

* Implement a generic way to construct VRF Transcript

* Use make_transcript_data to call sr25519_vrf_sign

* Make sure VRFTranscriptData is serializable

* Cleanup

* Move VRF to it's own module

* Implement & test VRF signing in testing module

* Remove leftover

* Fix feature requirements

* Revert removing vec macro

* Drop keystore pointer to prevent deadlock

* Nitpicks

* Add test to make sure make_transcript works

* Fix mismatch in VRF transcript

* Add a test to verify transcripts match in babe

* Return VRFOutput and VRFProof from keystore

substrate/primitives/core/src/lib.rs

@@ -73,6 +73,8 @@ pub mod traits;
 pub mod testing;
 #[cfg(feature = "std")]
 pub mod tasks;
+#[cfg(feature = "std")]
+pub mod vrf;
 
 pub use self::hash::{H160, H256, H512, convert_hash};
 pub use self::uint::{U256, U512};

substrate/primitives/core/src/testing.rs

@@ -22,10 +22,12 @@ use crate::crypto::KeyTypeId;
 use crate::{
 	crypto::{Pair, Public, CryptoTypePublicPair},
 	ed25519, sr25519, ecdsa,
-	traits::BareCryptoStoreError
+	traits::Error,
+	vrf::{VRFTranscriptData, VRFSignature, make_transcript},
 };
 #[cfg(feature = "std")]
 use std::collections::HashSet;
+
 /// Key type for generic Ed25519 key.
 pub const ED25519: KeyTypeId = KeyTypeId(*b"ed25");
 /// Key type for generic Sr 25519 key.
@@ -76,7 +78,7 @@ impl KeyStore {
 
 #[cfg(feature = "std")]
 impl crate::traits::BareCryptoStore for KeyStore {
-	fn keys(&self, id: KeyTypeId) -> Result<Vec<CryptoTypePublicPair>, BareCryptoStoreError> {
+	fn keys(&self, id: KeyTypeId) -> Result<Vec<CryptoTypePublicPair>, Error> {
 		self.keys
 			.get(&id)
 			.map(|map| {
@@ -106,11 +108,11 @@ impl crate::traits::BareCryptoStore for KeyStore {
 		&mut self,
 		id: KeyTypeId,
 		seed: Option<&str>,
-	) -> Result<sr25519::Public, BareCryptoStoreError> {
+	) -> Result<sr25519::Public, Error> {
 		match seed {
 			Some(seed) => {
 				let pair = sr25519::Pair::from_string(seed, None)
-					.map_err(|_| BareCryptoStoreError::ValidationError("Generates an `sr25519` pair.".to_owned()))?;
+					.map_err(|_| Error::ValidationError("Generates an `sr25519` pair.".to_owned()))?;
 				self.keys.entry(id).or_default().insert(pair.public().to_raw_vec(), seed.into());
 				Ok(pair.public())
 			},
@@ -137,11 +139,11 @@ impl crate::traits::BareCryptoStore for KeyStore {
 		&mut self,
 		id: KeyTypeId,
 		seed: Option<&str>,
-	) -> Result<ed25519::Public, BareCryptoStoreError> {
+	) -> Result<ed25519::Public, Error> {
 		match seed {
 			Some(seed) => {
 				let pair = ed25519::Pair::from_string(seed, None)
-					.map_err(|_| BareCryptoStoreError::ValidationError("Generates an `ed25519` pair.".to_owned()))?;
+					.map_err(|_| Error::ValidationError("Generates an `ed25519` pair.".to_owned()))?;
 				self.keys.entry(id).or_default().insert(pair.public().to_raw_vec(), seed.into());
 				Ok(pair.public())
 			},
@@ -168,11 +170,11 @@ impl crate::traits::BareCryptoStore for KeyStore {
 		&mut self,
 		id: KeyTypeId,
 		seed: Option<&str>,
-	) -> Result<ecdsa::Public, BareCryptoStoreError> {
+	) -> Result<ecdsa::Public, Error> {
 		match seed {
 			Some(seed) => {
 				let pair = ecdsa::Pair::from_string(seed, None)
-					.map_err(|_| BareCryptoStoreError::ValidationError("Generates an `ecdsa` pair.".to_owned()))?;
+					.map_err(|_| Error::ValidationError("Generates an `ecdsa` pair.".to_owned()))?;
 				self.keys.entry(id).or_default().insert(pair.public().to_raw_vec(), seed.into());
 				Ok(pair.public())
 			},
@@ -201,7 +203,7 @@ impl crate::traits::BareCryptoStore for KeyStore {
 		&self,
 		id: KeyTypeId,
 		keys: Vec<CryptoTypePublicPair>,
-	) -> std::result::Result<Vec<CryptoTypePublicPair>, BareCryptoStoreError> {
+	) -> std::result::Result<Vec<CryptoTypePublicPair>, Error> {
 		let provided_keys = keys.into_iter().collect::<HashSet<_>>();
 		let all_keys = self.keys(id)?.into_iter().collect::<HashSet<_>>();
 
@@ -213,31 +215,48 @@ impl crate::traits::BareCryptoStore for KeyStore {
 		id: KeyTypeId,
 		key: &CryptoTypePublicPair,
 		msg: &[u8],
-	) -> Result<Vec<u8>, BareCryptoStoreError> {
+	) -> Result<Vec<u8>, Error> {
 		use codec::Encode;
 
 		match key.0 {
 			ed25519::CRYPTO_ID => {
 				let key_pair: ed25519::Pair = self
 					.ed25519_key_pair(id, &ed25519::Public::from_slice(key.1.as_slice()))
-					.ok_or(BareCryptoStoreError::PairNotFound("ed25519".to_owned()))?;
+					.ok_or(Error::PairNotFound("ed25519".to_owned()))?;
 				return Ok(key_pair.sign(msg).encode());
 			}
 			sr25519::CRYPTO_ID => {
 				let key_pair: sr25519::Pair = self
 					.sr25519_key_pair(id, &sr25519::Public::from_slice(key.1.as_slice()))
-					.ok_or(BareCryptoStoreError::PairNotFound("sr25519".to_owned()))?;
+					.ok_or(Error::PairNotFound("sr25519".to_owned()))?;
 				return Ok(key_pair.sign(msg).encode());
 			}
 			ecdsa::CRYPTO_ID => {
 				let key_pair: ecdsa::Pair = self
 					.ecdsa_key_pair(id, &ecdsa::Public::from_slice(key.1.as_slice()))
-					.ok_or(BareCryptoStoreError::PairNotFound("ecdsa".to_owned()))?;
+					.ok_or(Error::PairNotFound("ecdsa".to_owned()))?;
 				return Ok(key_pair.sign(msg).encode());
 			}
-			_ => Err(BareCryptoStoreError::KeyNotSupported(id))
+			_ => Err(Error::KeyNotSupported(id))
 		}
 	}
+
+	fn sr25519_vrf_sign(
+		&self,
+		key_type: KeyTypeId,
+		public: &sr25519::Public,
+		transcript_data: VRFTranscriptData,
+	) -> Result<VRFSignature, Error> {
+		let transcript = make_transcript(transcript_data);
+		let pair = self.sr25519_key_pair(key_type, public)
+			.ok_or(Error::PairNotFound("Not found".to_owned()))?;
+
+		let (inout, proof, _) = pair.as_ref().vrf_sign(transcript);
+		Ok(VRFSignature {
+			output: inout.to_output(),
+			proof,
+		})
+	}
 }
 
 /// Macro for exporting functions from wasm in with the expected signature for using it with the
@@ -372,6 +391,7 @@ mod tests {
 	use super::*;
 	use crate::sr25519;
 	use crate::testing::{ED25519, SR25519};
+	use crate::vrf::VRFTranscriptValue;
 
 	#[test]
 	fn store_key_and_extract() {
@@ -403,4 +423,42 @@ mod tests {
 
 		assert!(public_keys.contains(&key_pair.public().into()));
 	}
+
+	#[test]
+	fn vrf_sign() {
+		let store = KeyStore::new();
+
+		let secret_uri = "//Alice";
+		let key_pair = sr25519::Pair::from_string(secret_uri, None).expect("Generates key pair");
+
+		let transcript_data = VRFTranscriptData {
+			label: b"Test",
+			items: vec![
+				("one", VRFTranscriptValue::U64(1)),
+				("two", VRFTranscriptValue::U64(2)),
+				("three", VRFTranscriptValue::Bytes("test".as_bytes())),
+			]
+		};
+
+		let result = store.read().sr25519_vrf_sign(
+			SR25519,
+			&key_pair.public(),
+			transcript_data.clone(),
+		);
+		assert!(result.is_err());
+
+		store.write().insert_unknown(
+			SR25519,
+			secret_uri,
+			key_pair.public().as_ref(),
+		).expect("Inserts unknown key");
+
+		let result = store.read().sr25519_vrf_sign(
+			SR25519,
+			&key_pair.public(),
+			transcript_data,
+		);
+
+		assert!(result.is_ok());
+	}
 }

substrate/primitives/core/src/traits.rs

@@ -19,9 +19,9 @@
 
 use crate::{
 	crypto::{KeyTypeId, CryptoTypePublicPair},
+	vrf::{VRFTranscriptData, VRFSignature},
 	ed25519, sr25519, ecdsa,
 };
-
 use std::{
 	borrow::Cow,
 	fmt::{Debug, Display},
@@ -33,7 +33,7 @@ pub use sp_externalities::{Externalities, ExternalitiesExt};
 
 /// BareCryptoStore error
 #[derive(Debug, derive_more::Display)]
-pub enum BareCryptoStoreError {
+pub enum Error {
 	/// Public key type is not supported
 	#[display(fmt="Key not supported: {:?}", _0)]
 	KeyNotSupported(KeyTypeId),
@@ -64,7 +64,7 @@ pub trait BareCryptoStore: Send + Sync {
 		&mut self,
 		id: KeyTypeId,
 		seed: Option<&str>,
-	) -> Result<sr25519::Public, BareCryptoStoreError>;
+	) -> Result<sr25519::Public, Error>;
 	/// Returns all ed25519 public keys for the given key type.
 	fn ed25519_public_keys(&self, id: KeyTypeId) -> Vec<ed25519::Public>;
 	/// Generate a new ed25519 key pair for the given key type and an optional seed.
@@ -76,7 +76,7 @@ pub trait BareCryptoStore: Send + Sync {
 		&mut self,
 		id: KeyTypeId,
 		seed: Option<&str>,
-	) -> Result<ed25519::Public, BareCryptoStoreError>;
+	) -> Result<ed25519::Public, Error>;
 	/// Returns all ecdsa public keys for the given key type.
 	fn ecdsa_public_keys(&self, id: KeyTypeId) -> Vec<ecdsa::Public>;
 	/// Generate a new ecdsa key pair for the given key type and an optional seed.
@@ -88,7 +88,7 @@ pub trait BareCryptoStore: Send + Sync {
 		&mut self,
 		id: KeyTypeId,
 		seed: Option<&str>,
-	) -> Result<ecdsa::Public, BareCryptoStoreError>;
+	) -> Result<ecdsa::Public, Error>;
 
 	/// Insert a new key. This doesn't require any known of the crypto; but a public key must be
 	/// manually provided.
@@ -108,11 +108,11 @@ pub trait BareCryptoStore: Send + Sync {
 		&self,
 		id: KeyTypeId,
 		keys: Vec<CryptoTypePublicPair>
-	) -> Result<Vec<CryptoTypePublicPair>, BareCryptoStoreError>;
+	) -> Result<Vec<CryptoTypePublicPair>, Error>;
 	/// List all supported keys
 	///
 	/// Returns a set of public keys the signer supports.
-	fn keys(&self, id: KeyTypeId) -> Result<Vec<CryptoTypePublicPair>, BareCryptoStoreError>;
+	fn keys(&self, id: KeyTypeId) -> Result<Vec<CryptoTypePublicPair>, Error>;
 
 	/// Checks if the private keys for the given public key and key type combinations exist.
 	///
@@ -131,7 +131,7 @@ pub trait BareCryptoStore: Send + Sync {
 		id: KeyTypeId,
 		key: &CryptoTypePublicPair,
 		msg: &[u8],
-	) -> Result<Vec<u8>, BareCryptoStoreError>;
+	) -> Result<Vec<u8>, Error>;
 
 	/// Sign with any key
 	///
@@ -144,7 +144,7 @@ pub trait BareCryptoStore: Send + Sync {
 		id: KeyTypeId,
 		keys: Vec<CryptoTypePublicPair>,
 		msg: &[u8]
-	) -> Result<(CryptoTypePublicPair, Vec<u8>), BareCryptoStoreError> {
+	) -> Result<(CryptoTypePublicPair, Vec<u8>), Error> {
 		if keys.len() == 1 {
 			return self.sign_with(id, &keys[0], msg).map(|s| (keys[0].clone(), s));
 		} else {
@@ -154,7 +154,7 @@ pub trait BareCryptoStore: Send + Sync {
 				}
 			}
 		}
-		Err(BareCryptoStoreError::KeyNotSupported(id))
+		Err(Error::KeyNotSupported(id))
 	}
 
 	/// Sign with all keys
@@ -163,15 +163,36 @@ pub trait BareCryptoStore: Send + Sync {
 	/// each key given that the key is supported.
 	///
 	/// Returns a list of `Result`s each representing the SCALE encoded
-	/// signature of each key or a BareCryptoStoreError for non-supported keys.
+	/// signature of each key or a Error for non-supported keys.
 	fn sign_with_all(
 		&self,
 		id: KeyTypeId,
 		keys: Vec<CryptoTypePublicPair>,
 		msg: &[u8],
-	) -> Result<Vec<Result<Vec<u8>, BareCryptoStoreError>>, ()>{
+	) -> Result<Vec<Result<Vec<u8>, Error>>, ()>{
 		Ok(keys.iter().map(|k| self.sign_with(id, k, msg)).collect())
 	}
+
+	/// Generate VRF signature for given transcript data.
+	///
+	/// Receives KeyTypeId and Public key to be able to map
+	/// them to a private key that exists in the keystore which
+	/// is, in turn, used for signing the provided transcript.
+	///
+	/// Returns a result containing the signature data.
+	/// Namely, VRFOutput and VRFProof which are returned
+	/// inside the `VRFSignature` container struct.
+	///
+	/// This function will return an error in the cases where
+	/// the public key and key type provided do not match a private
+	/// key in the keystore. Or, in the context of remote signing
+	/// an error could be a network one.
+	fn sr25519_vrf_sign(
+		&self,
+		key_type: KeyTypeId,
+		public: &sr25519::Public,
+		transcript_data: VRFTranscriptData,
+	) -> Result<VRFSignature, Error>;
 }
 
 /// A pointer to the key store.

substrate/primitives/core/src/vrf.rs

@@ -0,0 +1,99 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2019-2020 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! VRF-specifc data types and helpers
+
+use codec::Encode;
+use merlin::Transcript;
+use schnorrkel::vrf::{VRFOutput, VRFProof};
+/// An enum whose variants represent possible
+/// accepted values to construct the VRF transcript
+#[derive(Clone, Encode)]
+pub enum VRFTranscriptValue<'a> {
+	/// Value is an array of bytes
+	Bytes(&'a [u8]),
+	/// Value is a u64 integer
+	U64(u64),
+}
+/// VRF Transcript data
+#[derive(Clone, Encode)]
+pub struct VRFTranscriptData<'a> {
+	/// The transcript's label
+	pub label: &'static [u8],
+	/// Additional data to be registered into the transcript
+	pub items: Vec<(&'static str, VRFTranscriptValue<'a>)>,
+}
+/// VRF signature data
+pub struct VRFSignature {
+	/// The VRFOutput serialized
+	pub output: VRFOutput,
+	/// The calculated VRFProof
+	pub proof: VRFProof,
+}
+
+/// Construct a `Transcript` object from data.
+///
+/// Returns `merlin::Transcript`
+pub fn make_transcript(data: VRFTranscriptData) -> Transcript {
+	let mut transcript = Transcript::new(data.label);
+	for (label, value) in data.items.into_iter() {
+		match value {
+			VRFTranscriptValue::Bytes(bytes) => {
+				transcript.append_message(label.as_bytes(), &bytes);
+			},
+			VRFTranscriptValue::U64(val) => {
+				transcript.append_u64(label.as_bytes(), val);
+			}
+		}
+	}
+	transcript
+}
+
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use crate::vrf::VRFTranscriptValue;
+	use rand::RngCore;
+	use rand_chacha::{
+		rand_core::SeedableRng,
+		ChaChaRng,
+	};
+
+	#[test]
+	fn transcript_creation_matches() {
+		let mut orig_transcript = Transcript::new(b"My label");
+		orig_transcript.append_u64(b"one", 1);
+		orig_transcript.append_message(b"two", "test".as_bytes());
+
+		let new_transcript = make_transcript(VRFTranscriptData {
+			label: b"My label",
+			items: vec![
+				("one", VRFTranscriptValue::U64(1)),
+				("two", VRFTranscriptValue::Bytes("test".as_bytes())),
+			],
+		});
+		let test = |t: Transcript| -> [u8; 16] {
+			let mut b = [0u8; 16];
+			t.build_rng()
+				.finalize(&mut ChaChaRng::from_seed([0u8;32]))
+				.fill_bytes(&mut b);
+			b
+		};
+		debug_assert!(test(orig_transcript) == test(new_transcript));
+	}
+}