grandpa: Use storage proofs for Grandpa authorities (#3734)

* grandpa: Write Grandpa authorities to well known key.

Instead of requiring execution proofs for Grandpa authorities, this
enables much simpler storage proofs.

* grandpa: Introduce named AuthorityList type.

* grandpa: Storage migration for srml-grandpa module.

* Remove no-longer-used GrandpaApi runtime API.

* grandpa: Write AuthorityList to storage with encoding version.

We expect the AuthorityList type may change (eg. key changes). To make
upgrades smoother, include a version in the stored value.

* Bump node runtime spec version.

* Update srml/grandpa/src/lib.rs

Co-Authored-By: André Silva <andre.beat@gmail.com>

core/finality-grandpa/primitives/Cargo.toml

@@ -5,7 +5,6 @@ authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-client = { package = "substrate-client", path = "../../client", default-features = false }
 app-crypto = { package = "substrate-application-crypto", path = "../../application-crypto", default-features = false }
 codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
 sr-primitives = { path = "../../sr-primitives", default-features = false }
@@ -15,7 +14,6 @@ serde = { version = "1.0.101", optional = true, features = ["derive"] }
 [features]
 default = ["std"]
 std = [
-	"client/std",
 	"codec/std",
 	"sr-primitives/std",
 	"rstd/std",

core/finality-grandpa/primitives/src/lib.rs

@@ -23,9 +23,9 @@ extern crate alloc;
 
 #[cfg(feature = "std")]
 use serde::Serialize;
-use codec::{Encode, Decode, Codec};
+use codec::{Encode, Decode, Input, Codec};
 use sr_primitives::{ConsensusEngineId, RuntimeDebug};
-use client::decl_runtime_apis;
+use rstd::borrow::Cow;
 use rstd::vec::Vec;
 
 mod app {
@@ -46,6 +46,10 @@ pub type AuthoritySignature = app::Signature;
 /// The `ConsensusEngineId` of GRANDPA.
 pub const GRANDPA_ENGINE_ID: ConsensusEngineId = *b"FRNK";
 
+/// The storage key for the current set of weighted Grandpa authorities.
+/// The value stored is an encoded VersionedAuthorityList.
+pub const GRANDPA_AUTHORITIES_KEY: &'static [u8] = b":grandpa_authorities";
+
 /// The weight of an authority.
 pub type AuthorityWeight = u64;
 
@@ -58,12 +62,15 @@ pub type SetId = u64;
 /// The round indicator.
 pub type RoundNumber = u64;
 
+/// A list of Grandpa authorities with associated weights.
+pub type AuthorityList = Vec<(AuthorityId, AuthorityWeight)>;
+
 /// A scheduled change of authority set.
 #[cfg_attr(feature = "std", derive(Serialize))]
 #[derive(Clone, Eq, PartialEq, Encode, Decode, RuntimeDebug)]
 pub struct ScheduledChange<N> {
 	/// The new authorities after the change, along with their respective weights.
-	pub next_authorities: Vec<(AuthorityId, AuthorityWeight)>,
+	pub next_authorities: AuthorityList,
 	/// The number of blocks to delay.
 	pub delay: N,
 }
@@ -154,24 +161,51 @@ pub const PENDING_CHANGE_CALL: &str = "grandpa_pending_change";
 /// WASM function call to get current GRANDPA authorities.
 pub const AUTHORITIES_CALL: &str = "grandpa_authorities";
 
-decl_runtime_apis! {
-	/// APIs for integrating the GRANDPA finality gadget into runtimes.
-	/// This should be implemented on the runtime side.
-	///
-	/// This is primarily used for negotiating authority-set changes for the
-	/// gadget. GRANDPA uses a signaling model of changing authority sets:
-	/// changes should be signaled with a delay of N blocks, and then automatically
-	/// applied in the runtime after those N blocks have passed.
-	///
-	/// The consensus protocol will coordinate the handoff externally.
-	#[api_version(2)]
-	pub trait GrandpaApi {
-		/// Get the current GRANDPA authorities and weights. This should not change except
-		/// for when changes are scheduled and the corresponding delay has passed.
-		///
-		/// When called at block B, it will return the set of authorities that should be
-		/// used to finalize descendants of this block (B+1, B+2, ...). The block B itself
-		/// is finalized by the authorities from block B-1.
-		fn grandpa_authorities() -> Vec<(AuthorityId, AuthorityWeight)>;
+/// The current version of the stored AuthorityList type. The encoding version MUST be updated any
+/// time the AuthorityList type changes.
+const AUTHORITIES_VERISON: u8 = 1;
+
+/// An AuthorityList that is encoded with a version specifier. The encoding version is updated any
+/// time the AuthorityList type changes. This ensures that encodings of different versions of an
+/// AuthorityList are differentiable. Attempting to decode an authority list with an unknown
+/// version will fail.
+#[derive(Default)]
+pub struct VersionedAuthorityList<'a>(Cow<'a, AuthorityList>);
+
+impl<'a> From<AuthorityList> for VersionedAuthorityList<'a> {
+	fn from(authorities: AuthorityList) -> Self {
+		VersionedAuthorityList(Cow::Owned(authorities))
+	}
+}
+
+impl<'a> From<&'a AuthorityList> for VersionedAuthorityList<'a> {
+	fn from(authorities: &'a AuthorityList) -> Self {
+		VersionedAuthorityList(Cow::Borrowed(authorities))
+	}
+}
+
+impl<'a> Into<AuthorityList> for VersionedAuthorityList<'a> {
+	fn into(self) -> AuthorityList {
+		self.0.into_owned()
+	}
+}
+
+impl<'a> Encode for VersionedAuthorityList<'a> {
+	fn size_hint(&self) -> usize {
+		(AUTHORITIES_VERISON, self.0.as_ref()).size_hint()
+	}
+
+	fn using_encoded<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
+		(AUTHORITIES_VERISON, self.0.as_ref()).using_encoded(f)
+	}
+}
+
+impl<'a> Decode for VersionedAuthorityList<'a> {
+	fn decode<I: Input>(value: &mut I) -> Result<Self, codec::Error> {
+		let (version, authorities): (u8, AuthorityList) = Decode::decode(value)?;
+		if version != AUTHORITIES_VERISON {
+			return Err("unknown Grandpa authorities version".into());
+		}
+		Ok(authorities.into())
 	}
 }

core/finality-grandpa/src/authorities.rs

@@ -22,7 +22,7 @@ use grandpa::voter_set::VoterSet;
 use codec::{Encode, Decode};
 use log::{debug, info};
 use substrate_telemetry::{telemetry, CONSENSUS_INFO};
-use fg_primitives::AuthorityId;
+use fg_primitives::{AuthorityId, AuthorityList};
 
 use std::cmp::Ord;
 use std::fmt::Debug;
@@ -86,7 +86,7 @@ pub(crate) struct Status<H, N> {
 /// A set of authorities.
 #[derive(Debug, Clone, Encode, Decode, PartialEq)]
 pub(crate) struct AuthoritySet<H, N> {
-	pub(crate) current_authorities: Vec<(AuthorityId, u64)>,
+	pub(crate) current_authorities: AuthorityList,
 	pub(crate) set_id: u64,
 	// Tree of pending standard changes across forks. Standard changes are
 	// enacted on finality and must be enacted (i.e. finalized) in-order across
@@ -103,7 +103,7 @@ where H: PartialEq,
 	  N: Ord,
 {
 	/// Get a genesis set with given authorities.
-	pub(crate) fn genesis(initial: Vec<(AuthorityId, u64)>) -> Self {
+	pub(crate) fn genesis(initial: AuthorityList) -> Self {
 		AuthoritySet {
 			current_authorities: initial,
 			set_id: 0,
@@ -390,7 +390,7 @@ pub(crate) enum DelayKind<N> {
 #[derive(Debug, Clone, Encode, PartialEq)]
 pub(crate) struct PendingChange<H, N> {
 	/// The new authorities and weights to apply.
-	pub(crate) next_authorities: Vec<(AuthorityId, u64)>,
+	pub(crate) next_authorities: AuthorityList,
 	/// How deep in the chain the announcing block must be
 	/// before the change is applied.
 	pub(crate) delay: N,

core/finality-grandpa/src/aux_schema.rs

@@ -25,7 +25,7 @@ use fork_tree::ForkTree;
 use grandpa::round::State as RoundState;
 use sr_primitives::traits::{Block as BlockT, NumberFor};
 use log::{info, warn};
-use fg_primitives::{AuthorityId, AuthorityWeight, SetId, RoundNumber};
+use fg_primitives::{AuthorityList, SetId, RoundNumber};
 
 use crate::authorities::{AuthoritySet, SharedAuthoritySet, PendingChange, DelayKind};
 use crate::consensus_changes::{SharedConsensusChanges, ConsensusChanges};
@@ -55,15 +55,15 @@ type V0VoterSetState<H, N> = (RoundNumber, RoundState<H, N>);
 
 #[derive(Debug, Clone, Encode, Decode, PartialEq)]
 struct V0PendingChange<H, N> {
-	next_authorities: Vec<(AuthorityId, AuthorityWeight)>,
+	next_authorities: AuthorityList,
 	delay: N,
 	canon_height: N,
 	canon_hash: H,
 }
 
 #[derive(Debug, Clone, Encode, Decode, PartialEq)]
 struct V0AuthoritySet<H, N> {
-	current_authorities: Vec<(AuthorityId, AuthorityWeight)>,
+	current_authorities: AuthorityList,
 	set_id: SetId,
 	pending_changes: Vec<V0PendingChange<H, N>>,
 }
@@ -266,7 +266,7 @@ pub(crate) fn load_persistent<Block: BlockT, B, G>(
 	-> ClientResult<PersistentData<Block>>
 	where
 		B: AuxStore,
-		G: FnOnce() -> ClientResult<Vec<(AuthorityId, AuthorityWeight)>>,
+		G: FnOnce() -> ClientResult<AuthorityList>,
 {
 	let version: Option<u32> = load_decode(backend, VERSION_KEY)?;
 	let consensus_changes = load_decode(backend, CONSENSUS_CHANGES_KEY)?
@@ -426,6 +426,7 @@ pub(crate) fn load_authorities<B: AuxStore, H: Decode, N: Decode>(backend: &B)
 
 #[cfg(test)]
 mod test {
+	use fg_primitives::AuthorityId;
 	use primitives::H256;
 	use test_client;
 	use super::*;

core/finality-grandpa/src/communication/tests.rs

@@ -28,6 +28,7 @@ use codec::Encode;
 use sr_primitives::traits::NumberFor;
 
 use crate::environment::SharedVoterSetState;
+use fg_primitives::AuthorityList;
 use super::gossip::{self, GossipValidator};
 use super::{AuthorityId, VoterSet, Round, SetId};
 
@@ -200,7 +201,7 @@ fn make_test_network() -> (
 	)
 }
 
-fn make_ids(keys: &[Ed25519Keyring]) -> Vec<(AuthorityId, u64)> {
+fn make_ids(keys: &[Ed25519Keyring]) -> AuthorityList {
 	keys.iter()
 		.map(|key| key.clone().public().into())
 		.map(|id| (id, 1))