Sassafras primitives

Cargo.toml

@@ -29,6 +29,21 @@ frame-support = { path = "frame/support" }
 
 node-cli = { path = "bin/node/cli" }
 
+# This list of dependencies is necessary to build sassafras primitives.
+# `bandersnatch-experimental` is transitively passed between:
+# sp-consensus-sassafras → sp-application-crypto → sp-io → sp-keystore
+# Thus we end up having the bandersnatch functions "unlocked" in the `Keystore` trait.
+# Follow that we require bandersnatch implementations in the client keystore as well.
+sp-consensus-sassafras = { path = "primitives/consensus/sassafras", optional = true }
+sc-keystore = { path = "client/keystore" }
+
+# Feature to unlock "Sassafras" experimental crates
+[features]
+sassafras-experimental = [ 
+	"sp-consensus-sassafras",
+	"sc-keystore/bandersnatch-experimental",
+]
+
 # Exists here to be backwards compatible and to support `cargo run` in the workspace.
 #
 # Just uses the `node-cli` main binary. `node-cli` itself also again exposes the node as

primitives/consensus/sassafras/Cargo.toml

@@ -0,0 +1,50 @@
+[package]
+name = "sp-consensus-sassafras"
+version = "0.3.4-dev"
+authors = ["Parity Technologies <[email protected]>"]
+description = "Primitives for Sassafras consensus"
+edition = "2021"
+license = "Apache-2.0"
+homepage = "https://substrate.io"
+repository = "https://github.com/paritytech/substrate/"
+documentation = "https://docs.rs/sp-consensus-sassafras"
+readme = "README.md"
+publish = false
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies]
+scale-codec = { package = "parity-scale-codec", version = "3.2.2", default-features = false }
+scale-info = { version = "2.5.0", default-features = false, features = ["derive"] }
+serde = { version = "1.0.163", default-features = false, features = ["derive"], optional = true }
+sp-api = { version = "4.0.0-dev", default-features = false, path = "../../api" }
+sp-application-crypto = { version = "23.0.0", default-features = false, path = "../../application-crypto", features = ["bandersnatch-experimental"] }
+sp-consensus-slots = { version = "0.10.0-dev", default-features = false, path = "../slots" }
+sp-core = { version = "21.0.0", default-features = false, path = "../../core", features = ["bandersnatch-experimental"] }
+sp-runtime = { version = "24.0.0", default-features = false, path = "../../runtime" }
+sp-std = { version = "8.0.0", default-features = false, path = "../../std" }
+
+[features]
+default = ["std"]
+std = [
+ 	"scale-codec/std",
+ 	"scale-info/std",
+ 	"serde/std",
+ 	"sp-api/std",
+ 	"sp-application-crypto/std",
+	"sp-consensus-slots/std",
+ 	"sp-core/std",
+ 	"sp-runtime/std",
+ 	"sp-std/std",
+]
+
+# Serde support without relying on std features.
+serde = [
+	"dep:serde",
+	"scale-info/serde",
+	"sp-application-crypto/serde",
+	"sp-consensus-slots/serde",
+	"sp-core/serde",
+	"sp-runtime/serde",
+]

primitives/consensus/sassafras/README.md

@@ -0,0 +1,12 @@
+Primitives for SASSAFRAS.
+
+# ⚠️ WARNING ⚠️
+
+The crate interfaces and structures are highly experimental and may be subject
+to significant changes.
+
+Depends on upstream experimental feature: `bandersnatch-experimental`.
+
+These structs were mostly extracted from the main SASSAFRAS protocol PR: https://github.com/paritytech/substrate/pull/11879.
+
+Tracking issue: https://github.com/paritytech/substrate/issues/11515.

primitives/consensus/sassafras/src/digests.rs

@@ -0,0 +1,99 @@
+// This file is part of Substrate.
+
+// Copyright (C) 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.
+
+//! Sassafras digests structures and helpers.
+
+use crate::{
+	ticket::TicketClaim, AuthorityId, AuthorityIndex, AuthoritySignature, EpochConfiguration,
+	Randomness, Slot, VrfSignature, SASSAFRAS_ENGINE_ID,
+};
+
+use scale_codec::{Decode, Encode, MaxEncodedLen};
+use scale_info::TypeInfo;
+
+use sp_runtime::{DigestItem, RuntimeDebug};
+use sp_std::vec::Vec;
+
+/// Sassafras slot assignment pre-digest.
+#[derive(Clone, RuntimeDebug, Encode, Decode, MaxEncodedLen, TypeInfo)]
+pub struct PreDigest {
+	/// Authority index that claimed the slot.
+	pub authority_idx: AuthorityIndex,
+	/// Corresponding slot number.
+	pub slot: Slot,
+	/// Slot claim VRF signature.
+	pub vrf_signature: VrfSignature,
+	/// Ticket auxiliary information for claim check.
+	pub ticket_claim: Option<TicketClaim>,
+}
+
+/// Information about the next epoch.
+///
+/// This is broadcast in the first block of each epoch.
+#[derive(Clone, PartialEq, Eq, Encode, Decode, RuntimeDebug)]
+pub struct NextEpochDescriptor {
+	/// Authorities list.
+	pub authorities: Vec<AuthorityId>,
+	/// Epoch randomness.
+	pub randomness: Randomness,
+	/// Configurable parameters. If not present previous epoch parameters are used.
+	pub config: Option<EpochConfiguration>,
+}
+
+/// Consensus log item.
+#[derive(Decode, Encode, Clone, PartialEq, Eq)]
+pub enum ConsensusLog {
+	/// Provides information about the next epoch parameters.
+	#[codec(index = 1)]
+	NextEpochData(NextEpochDescriptor),
+	/// Disable the authority with given index.
+	#[codec(index = 2)]
+	OnDisabled(AuthorityIndex),
+}
+
+/// A digest item which is usable by Sassafras.
+pub trait CompatibleDigestItem {
+	/// Construct a digest item which contains a `PreDigest`.
+	fn sassafras_pre_digest(seal: PreDigest) -> Self;
+
+	/// If this item is a `PreDigest`, return it.
+	fn as_sassafras_pre_digest(&self) -> Option<PreDigest>;
+
+	/// Construct a digest item which contains an `AuthoritySignature`.
+	fn sassafras_seal(signature: AuthoritySignature) -> Self;
+
+	/// If this item is an `AuthoritySignature`, return it.
+	fn as_sassafras_seal(&self) -> Option<AuthoritySignature>;
+}
+
+impl CompatibleDigestItem for DigestItem {
+	fn sassafras_pre_digest(digest: PreDigest) -> Self {
+		DigestItem::PreRuntime(SASSAFRAS_ENGINE_ID, digest.encode())
+	}
+
+	fn as_sassafras_pre_digest(&self) -> Option<PreDigest> {
+		self.pre_runtime_try_to(&SASSAFRAS_ENGINE_ID)
+	}
+
+	fn sassafras_seal(signature: AuthoritySignature) -> Self {
+		DigestItem::Seal(SASSAFRAS_ENGINE_ID, signature.encode())
+	}
+
+	fn as_sassafras_seal(&self) -> Option<AuthoritySignature> {
+		self.seal_try_to(&SASSAFRAS_ENGINE_ID)
+	}
+}

primitives/consensus/sassafras/src/lib.rs

@@ -0,0 +1,179 @@
+// This file is part of Substrate.
+
+// Copyright (C) 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.
+
+//! Primitives for Sassafras consensus.
+
+#![deny(warnings)]
+#![forbid(unsafe_code, missing_docs, unused_variables, unused_imports)]
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use scale_codec::{Decode, Encode, MaxEncodedLen};
+use scale_info::TypeInfo;
+use sp_core::crypto::KeyTypeId;
+use sp_runtime::{ConsensusEngineId, RuntimeDebug};
+use sp_std::vec::Vec;
+
+pub use sp_consensus_slots::{Slot, SlotDuration};
+pub use sp_core::bandersnatch::{
+	ring_vrf::{RingContext, RingProver, RingVerifier, RingVrfSignature},
+	vrf::{VrfInput, VrfOutput, VrfSignData, VrfSignature},
+};
+
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
+pub mod digests;
+pub mod ticket;
+pub mod vrf;
+
+pub use ticket::{
+	ticket_id_threshold, EphemeralPublic, EphemeralSignature, TicketBody, TicketClaim,
+	TicketEnvelope, TicketId,
+};
+
+mod app {
+	use sp_application_crypto::{app_crypto, bandersnatch, key_types::SASSAFRAS};
+	app_crypto!(bandersnatch, SASSAFRAS);
+}
+
+/// Key type identifier.
+pub const KEY_TYPE: KeyTypeId = sp_application_crypto::key_types::SASSAFRAS;
+
+/// Consensus engine identifier.
+pub const SASSAFRAS_ENGINE_ID: ConsensusEngineId = *b"SASS";
+
+/// VRF output length for per-slot randomness.
+pub const RANDOMNESS_LENGTH: usize = 32;
+
+/// Index of an authority.
+pub type AuthorityIndex = u32;
+
+/// Sassafras authority keypair. Necessarily equivalent to the schnorrkel public key used in
+/// the main Sassafras module. If that ever changes, then this must, too.
+#[cfg(feature = "std")]
+pub type AuthorityPair = app::Pair;
+
+/// Sassafras authority signature.
+pub type AuthoritySignature = app::Signature;
+
+/// Sassafras authority identifier. Necessarily equivalent to the schnorrkel public key used in
+/// the main Sassafras module. If that ever changes, then this must, too.
+pub type AuthorityId = app::Public;
+
+/// Weight of a Sassafras block.
+/// Primary blocks have a weight of 1 whereas secondary blocks have a weight of 0.
+pub type SassafrasBlockWeight = u32;
+
+/// An equivocation proof for multiple block authorships on the same slot (i.e. double vote).
+pub type EquivocationProof<H> = sp_consensus_slots::EquivocationProof<H, AuthorityId>;
+
+/// Randomness required by some protocol's operations.
+pub type Randomness = [u8; RANDOMNESS_LENGTH];
+
+/// Configuration data that can be modified on epoch change.
+#[derive(
+	Copy, Clone, PartialEq, Eq, Encode, Decode, RuntimeDebug, MaxEncodedLen, TypeInfo, Default,
+)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct EpochConfiguration {
+	/// Tickets threshold redundancy factor.
+	pub redundancy_factor: u32,
+	/// Tickets attempts for each validator.
+	pub attempts_number: u32,
+}
+
+/// Sassafras epoch information
+#[derive(Debug, Clone, PartialEq, Eq, Encode, Decode, TypeInfo)]
+pub struct Epoch {
+	/// The epoch index.
+	pub epoch_idx: u64,
+	/// The starting slot of the epoch.
+	pub start_slot: Slot,
+	/// Slot duration in milliseconds.
+	pub slot_duration: SlotDuration,
+	/// Duration of epoch in slots.
+	pub epoch_duration: u64,
+	/// Authorities for the epoch.
+	pub authorities: Vec<AuthorityId>,
+	/// Randomness for the epoch.
+	pub randomness: Randomness,
+	/// Epoch configuration.
+	pub config: EpochConfiguration,
+}
+
+/// An opaque type used to represent the key ownership proof at the runtime API boundary.
+///
+/// The inner value is an encoded representation of the actual key ownership proof which will be
+/// parameterized when defining the runtime. At the runtime API boundary this type is unknown and
+/// as such we keep this opaque representation, implementors of the runtime API will have to make
+/// sure that all usages of `OpaqueKeyOwnershipProof` refer to the same type.
+#[derive(Decode, Encode, PartialEq, TypeInfo)]
+pub struct OpaqueKeyOwnershipProof(Vec<u8>);
+
+// Runtime API.
+sp_api::decl_runtime_apis! {
+	/// API necessary for block authorship with Sassafras.
+	pub trait SassafrasApi {
+		/// Get ring context to be used for ticket construction and verification.
+		fn ring_context() -> Option<RingContext>;
+
+		/// Submit next epoch validator tickets via an unsigned extrinsic.
+		/// This method returns `false` when creation of the extrinsics fails.
+		fn submit_tickets_unsigned_extrinsic(tickets: Vec<TicketEnvelope>) -> bool;
+
+		/// Get ticket id associated to the given slot.
+		fn slot_ticket_id(slot: Slot) -> Option<TicketId>;
+
+		/// Get ticket id and data associated to the given slot.
+		fn slot_ticket(slot: Slot) -> Option<(TicketId, TicketBody)>;
+
+		/// Current epoch information.
+		fn current_epoch() -> Epoch;
+
+		/// Next epoch information.
+		fn next_epoch() -> Epoch;
+
+		/// Generates a proof of key ownership for the given authority in the current epoch.
+		///
+		/// An example usage of this module is coupled with the session historical module to prove
+		/// that a given authority key is tied to a given staking identity during a specific
+		/// session. Proofs of key ownership are necessary for submitting equivocation reports.
+		///
+		/// NOTE: even though the API takes a `slot` as parameter the current implementations
+		/// ignores this parameter and instead relies on this method being called at the correct
+		/// block height, i.e. any point at which the epoch for the given slot is live on-chain.
+		/// Future implementations will instead use indexed data through an offchain worker, not
+		/// requiring older states to be available.
+		fn generate_key_ownership_proof(
+			slot: Slot,
+			authority_id: AuthorityId,
+		) -> Option<OpaqueKeyOwnershipProof>;
+
+		/// Submits an unsigned extrinsic to report an equivocation.
+		///
+		/// The caller must provide the equivocation proof and a key ownership proof (should be
+		/// obtained using `generate_key_ownership_proof`). The extrinsic will be unsigned and
+		/// should only be accepted for local authorship (not to be broadcast to the network). This
+		/// method returns `None` when creation of the extrinsic fails, e.g. if equivocation
+		/// reporting is disabled for the given runtime (i.e. this method is hardcoded to return
+		/// `None`). Only useful in an offchain context.
+		fn submit_report_equivocation_unsigned_extrinsic(
+			equivocation_proof: EquivocationProof<Block::Header>,
+			key_owner_proof: OpaqueKeyOwnershipProof,
+		) -> bool;
+	}
+}