Slash bad validators (#468)

* implement general design

* add slashing

* bug fixes

* fix pr comments

* misc fixes

* fix grandpa abi call type

* Correct rebase artifacts I introduced

* Cleanups and corrections

1) Uses vec![] for the OpaqueKeyProof as there's no value to passing it around
2) Remove usage of Babe/Grandpa Offences for tracking if an offence is known
   for checking if can slash. If can slash, no prior offence must have been
   known.
3) Rename DisabledIndices to SeraiDisabledIndices, drop historical data for
   current session only.
4) Doesn't remove from the pre-declared upcoming Serai set upon slash due to
   breaking light clients.
5) Into/From instead of AsRef for KeyOwnerProofSystem's generic to ensure
   safety of the conversion.

* Correct deduction from TotalAllocatedStake on slash

It should only be done if in set and only with allocations contributing to
TotalAllocatedStake (Allocation + latest session's PendingDeallocation).

* Changes meant for prior commit

---------

Co-authored-by: Luke Parker <lukeparker5132@gmail.com>

substrate/runtime/Cargo.toml

@@ -46,6 +46,7 @@ frame-benchmarking = { git = "https://github.com/serai-dex/substrate", default-f
 serai-primitives = { path = "../primitives", default-features = false }
 
 pallet-timestamp = { git = "https://github.com/serai-dex/substrate", default-features = false }
+pallet-authorship = { git = "https://github.com/serai-dex/substrate", default-features = false }
 
 pallet-transaction-payment = { git = "https://github.com/serai-dex/substrate", default-features = false }
 
@@ -98,6 +99,7 @@ std = [
   "serai-primitives/std",
 
   "pallet-timestamp/std",
+  "pallet-authorship/std",
 
   "pallet-transaction-payment/std",
 

substrate/runtime/src/lib.rs

@@ -6,6 +6,8 @@
 #[cfg(feature = "std")]
 include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
 
+use core::marker::PhantomData;
+
 // Re-export all components
 pub use serai_primitives as primitives;
 pub use primitives::{BlockNumber, Header};
@@ -55,9 +57,11 @@ use support::{
   parameter_types, construct_runtime,
 };
 
+use validator_sets::MembershipProof;
+
+use sp_authority_discovery::AuthorityId as AuthorityDiscoveryId;
 use babe::AuthorityId as BabeId;
 use grandpa::AuthorityId as GrandpaId;
-use sp_authority_discovery::AuthorityId as AuthorityDiscoveryId;
 
 /// Nonce of a transaction in the chain, for a given account.
 pub type Nonce = u32;
@@ -141,8 +145,6 @@ parameter_types! {
       Weight::from_parts(2u64 * WEIGHT_REF_TIME_PER_SECOND, u64::MAX),
       NORMAL_DISPATCH_RATIO,
     );
-
-  pub const MaxAuthorities: u32 = validator_sets::primitives::MAX_KEY_SHARES_PER_SET;
 }
 
 pub struct CallFilter;
@@ -275,20 +277,43 @@ impl in_instructions::Config for Runtime {
   type RuntimeEvent = RuntimeEvent;
 }
 
+// for publishing equivocation evidences.
+impl<C> frame_system::offchain::SendTransactionTypes<C> for Runtime
+where
+  RuntimeCall: From<C>,
+{
+  type Extrinsic = Transaction;
+  type OverarchingCall = RuntimeCall;
+}
+
+// for validating equivocation evidences.
+// The following runtime construction doesn't actually implement the pallet as doing so is
+// unnecessary
+// TODO: Replace the requirement on Config for a requirement on FindAuthor directly
+impl pallet_authorship::Config for Runtime {
+  type FindAuthor = ValidatorSets;
+  type EventHandler = ();
+}
+
+// Maximum number of authorities per session.
+pub type MaxAuthorities = ConstU32<{ validator_sets::primitives::MAX_KEY_SHARES_PER_SET }>;
+
+/// Longevity of an offence report.
+pub type ReportLongevity = <Runtime as pallet_babe::Config>::EpochDuration;
+
 impl babe::Config for Runtime {
   #[allow(clippy::identity_op)]
   type EpochDuration = ConstU64<{ 1 * DAYS }>;
   type ExpectedBlockTime = ConstU64<{ TARGET_BLOCK_TIME * 1000 }>;
-  type EpochChangeTrigger = pallet_babe::ExternalTrigger;
+  type EpochChangeTrigger = babe::ExternalTrigger;
   type DisabledValidators = ValidatorSets;
 
   type WeightInfo = ();
-
   type MaxAuthorities = MaxAuthorities;
 
-  // TODO: Handle equivocation reports
-  type KeyOwnerProof = sp_core::Void;
-  type EquivocationReportSystem = ();
+  type KeyOwnerProof = MembershipProof<Self>;
+  type EquivocationReportSystem =
+    babe::EquivocationReportSystem<Self, ValidatorSets, ValidatorSets, ReportLongevity>;
 }
 
 impl grandpa::Config for Runtime {
@@ -297,10 +322,10 @@ impl grandpa::Config for Runtime {
   type WeightInfo = ();
   type MaxAuthorities = MaxAuthorities;
 
-  // TODO: Handle equivocation reports
   type MaxSetIdSessionEntries = ConstU64<0>;
-  type KeyOwnerProof = sp_core::Void;
-  type EquivocationReportSystem = ();
+  type KeyOwnerProof = MembershipProof<Self>;
+  type EquivocationReportSystem =
+    grandpa::EquivocationReportSystem<Self, ValidatorSets, ValidatorSets, ReportLongevity>;
 }
 
 pub type Executive = frame_executive::Executive<
@@ -459,18 +484,22 @@ sp_api::impl_runtime_apis! {
       Babe::next_epoch()
     }
 
+    // This refers to a key being 'owned' by an authority in a system with multiple keys per
+    // validator
+    // Since we do not have such an infrastructure, we do not need this
     fn generate_key_ownership_proof(
-      _: sp_consensus_babe::Slot,
-      _: BabeId,
+      _slot: sp_consensus_babe::Slot,
+      _authority_id: BabeId,
     ) -> Option<sp_consensus_babe::OpaqueKeyOwnershipProof> {
-      None
+      Some(sp_consensus_babe::OpaqueKeyOwnershipProof::new(vec![]))
     }
 
     fn submit_report_equivocation_unsigned_extrinsic(
-      _: sp_consensus_babe::EquivocationProof<Header>,
+      equivocation_proof: sp_consensus_babe::EquivocationProof<Header>,
       _: sp_consensus_babe::OpaqueKeyOwnershipProof,
     ) -> Option<()> {
-      None
+      let proof = MembershipProof(equivocation_proof.offender.clone().into(), PhantomData);
+      Babe::submit_unsigned_equivocation_report(equivocation_proof, proof)
     }
   }
 
@@ -483,18 +512,19 @@ sp_api::impl_runtime_apis! {
       Grandpa::current_set_id()
     }
 
-    fn submit_report_equivocation_unsigned_extrinsic(
-      _: sp_consensus_grandpa::EquivocationProof<<Block as BlockT>::Hash, u64>,
-      _: sp_consensus_grandpa::OpaqueKeyOwnershipProof,
-    ) -> Option<()> {
-      None
-    }
-
     fn generate_key_ownership_proof(
       _set_id: sp_consensus_grandpa::SetId,
       _authority_id: GrandpaId,
     ) -> Option<sp_consensus_grandpa::OpaqueKeyOwnershipProof> {
-      None
+      Some(sp_consensus_grandpa::OpaqueKeyOwnershipProof::new(vec![]))
+    }
+
+    fn submit_report_equivocation_unsigned_extrinsic(
+      equivocation_proof: sp_consensus_grandpa::EquivocationProof<<Block as BlockT>::Hash, u64>,
+      _: sp_consensus_grandpa::OpaqueKeyOwnershipProof,
+    ) -> Option<()> {
+      let proof = MembershipProof(equivocation_proof.offender().clone().into(), PhantomData);
+      Grandpa::submit_unsigned_equivocation_report(equivocation_proof, proof)
     }
   }