From 6155d12160a485fe628fb63faefdf817cf4501ba Mon Sep 17 00:00:00 2001
From: Luke Parker <lukeparker5132@gmail.com>
Date: Mon, 17 Oct 2022 03:15:13 -0400
Subject: [PATCH] Dedicated Commit object

Restores sig aggregation API.
---
 substrate/tendermint/src/ext.rs   | 37 ++++++++++++++++++++++++++-----
 substrate/tendermint/src/lib.rs   | 26 +++++++++++++---------
 substrate/tendermint/tests/ext.rs | 20 +++++++++++++----
 3 files changed, 63 insertions(+), 20 deletions(-)

diff --git a/substrate/tendermint/src/ext.rs b/substrate/tendermint/src/ext.rs
index 56d4a20d..748150d7 100644
--- a/substrate/tendermint/src/ext.rs
+++ b/substrate/tendermint/src/ext.rs
@@ -31,6 +31,21 @@ pub trait SignatureScheme: Send + Sync {
   fn sign(&self, msg: &[u8]) -> Self::Signature;
   #[must_use]
   fn verify(&self, validator: Self::ValidatorId, msg: &[u8], sig: Self::Signature) -> bool;
+
+  fn aggregate(sigs: &[Self::Signature]) -> Self::AggregateSignature;
+  #[must_use]
+  fn verify_aggregate(
+    &self,
+    msg: &[u8],
+    signers: &[Self::ValidatorId],
+    sig: Self::AggregateSignature,
+  ) -> bool;
+}
+
+#[derive(Clone, PartialEq, Debug, Encode, Decode)]
+pub struct Commit<S: SignatureScheme> {
+  pub validators: Vec<S::ValidatorId>,
+  pub signature: S::AggregateSignature,
 }
 
 pub trait Weights: Send + Sync {
@@ -76,6 +91,21 @@ pub trait Network: Send + Sync {
   fn signature_scheme(&self) -> Arc<Self::SignatureScheme>;
   fn weights(&self) -> Arc<Self::Weights>;
 
+  #[must_use]
+  fn verify_commit(
+    &self,
+    id: <Self::Block as Block>::Id,
+    commit: Commit<Self::SignatureScheme>,
+  ) -> bool {
+    if !self.signature_scheme().verify_aggregate(&id.encode(), &commit.validators, commit.signature)
+    {
+      return false;
+    }
+
+    let weights = self.weights();
+    commit.validators.iter().map(|v| weights.weight(*v)).sum::<u64>() >= weights.threshold()
+  }
+
   async fn broadcast(
     &mut self,
     msg: SignedMessage<
@@ -90,9 +120,6 @@ pub trait Network: Send + Sync {
 
   fn validate(&mut self, block: &Self::Block) -> Result<(), BlockError>;
   // Add a block and return the proposal for the next one
-  fn add_block(
-    &mut self,
-    block: Self::Block,
-    sigs: Vec<(Self::ValidatorId, <Self::SignatureScheme as SignatureScheme>::Signature)>,
-  ) -> Self::Block;
+  fn add_block(&mut self, block: Self::Block, commit: Commit<Self::SignatureScheme>)
+    -> Self::Block;
 }
diff --git a/substrate/tendermint/src/lib.rs b/substrate/tendermint/src/lib.rs
index a1b4d387..7b398bfc 100644
--- a/substrate/tendermint/src/lib.rs
+++ b/substrate/tendermint/src/lib.rs
@@ -253,15 +253,19 @@ impl<N: Network + 'static> TendermintMachine<N> {
               match machine.message(msg.msg).await {
                 Ok(None) => (),
                 Ok(Some(block)) => {
-                  let sigs = machine
-                    .log
-                    .precommitted
-                    .iter()
-                    .filter_map(|(k, (id, sig))| {
-                      Some((*k, sig.clone())).filter(|_| id == &block.id())
-                    })
-                    .collect();
-                  let proposal = machine.network.write().await.add_block(block, sigs);
+                  let mut validators = vec![];
+                  let mut sigs = vec![];
+                  for (v, sig) in machine.log.precommitted.iter().filter_map(|(k, (id, sig))| {
+                    Some((*k, sig.clone())).filter(|_| id == &block.id())
+                  }) {
+                    validators.push(v);
+                    sigs.push(sig);
+                  }
+
+                  let proposal = machine.network.write().await.add_block(
+                    block,
+                    Commit { validators, signature: N::SignatureScheme::aggregate(&sigs) },
+                  );
                   machine.reset(proposal).await
                 }
                 Err(TendermintError::Malicious(validator)) => {
@@ -400,13 +404,13 @@ impl<N: Network + 'static> TendermintMachine<N> {
     if self.step == Step::Prevote {
       let (participation, weight) = self.log.message_instances(self.round, Data::Prevote(None));
       // 34-35
-      if participation > self.weights.threshold() {
+      if participation >= self.weights.threshold() {
         let timeout = self.timeout(Step::Prevote);
         self.timeouts.entry(Step::Prevote).or_insert(timeout);
       }
 
       // 44-46
-      if weight > self.weights.threshold() {
+      if weight >= self.weights.threshold() {
         debug_assert!(self.broadcast(Data::Precommit(None)).await.is_none());
       }
     }
diff --git a/substrate/tendermint/tests/ext.rs b/substrate/tendermint/tests/ext.rs
index 31dfca0c..478e213e 100644
--- a/substrate/tendermint/tests/ext.rs
+++ b/substrate/tendermint/tests/ext.rs
@@ -22,9 +22,23 @@ impl SignatureScheme for TestSignatureScheme {
     sig
   }
 
+  #[must_use]
   fn verify(&self, validator: u16, msg: &[u8], sig: [u8; 32]) -> bool {
     (sig[.. 2] == validator.to_le_bytes()) && (&sig[2 ..] == &[msg, &[0; 30]].concat()[.. 30])
   }
+
+  fn aggregate(sigs: &[[u8; 32]]) -> Vec<[u8; 32]> {
+    sigs.to_vec()
+  }
+
+  #[must_use]
+  fn verify_aggregate(&self, msg: &[u8], signers: &[TestValidatorId], sigs: Vec<[u8; 32]>) -> bool {
+    assert_eq!(signers.len(), sigs.len());
+    for sig in signers.iter().zip(sigs.iter()) {
+      assert!(self.verify(*sig.0, msg, *sig.1));
+    }
+    true
+  }
 }
 
 struct TestWeights;
@@ -91,12 +105,10 @@ impl Network for TestNetwork {
     block.valid
   }
 
-  fn add_block(&mut self, block: TestBlock, sigs: Vec<(u16, [u8; 32])>) -> TestBlock {
+  fn add_block(&mut self, block: TestBlock, commit: Commit<TestSignatureScheme>) -> TestBlock {
     dbg!("Adding ", &block);
     assert!(block.valid.is_ok());
-    for sig in sigs {
-      assert!(TestSignatureScheme(u16::MAX).verify(sig.0, &block.id().encode(), sig.1));
-    }
+    assert!(self.verify_commit(block.id(), commit));
     TestBlock { id: block.id + 1, valid: Ok(()) }
   }
 }