Fix u256 conversion in BABE (#5994)

#5886 (comment) --------- Co-authored-by: Bastian Köcher <[email protected]> Co-authored-by: Bastian Köcher <[email protected]>
paritytech · Oct 9, 2024 · 292bfac · 292bfac
1 parent 48b56aa
commit 292bfac
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Showing 2 changed files with 21 additions and 2 deletions.
diff --git a/prdoc/pr_5994.prdoc b/prdoc/pr_5994.prdoc
@@ -0,0 +1,3 @@
+crates:
+  - name: sc-consensus-babe
+    bump: none
diff --git a/substrate/client/consensus/babe/src/authorship.rs b/substrate/client/consensus/babe/src/authorship.rs
@@ -109,7 +109,7 @@ pub(super) fn secondary_slot_author(
 	}
 
 	let rand =
-		U256::from_little_endian(&(randomness, slot).using_encoded(sp_crypto_hashing::blake2_256));
+		U256::from_big_endian(&(randomness, slot).using_encoded(sp_crypto_hashing::blake2_256));
 
 	let authorities_len = U256::from(authorities.len());
 	let idx = rand % authorities_len;
@@ -272,7 +272,9 @@ fn claim_primary_slot(
 #[cfg(test)]
 mod tests {
 	use super::*;
-	use sp_consensus_babe::{AllowedSlots, AuthorityId, BabeEpochConfiguration, Epoch};
+	use sp_consensus_babe::{
+		AllowedSlots, AuthorityId, BabeEpochConfiguration, Epoch, RANDOMNESS_LENGTH,
+	};
 	use sp_core::{crypto::Pair as _, sr25519::Pair};
 	use sp_keystore::testing::MemoryKeystore;
 
@@ -306,4 +308,18 @@ mod tests {
 		epoch.authorities.push((valid_public_key.into(), 10));
 		assert_eq!(claim_slot(10.into(), &epoch, &keystore).unwrap().1, valid_public_key.into());
 	}
+
+	#[test]
+	fn secondary_slot_author_selection_works() {
+		let authorities = (0..1000)
+			.map(|i| (AuthorityId::from(Pair::generate().0.public()), i))
+			.collect::<Vec<_>>();
+
+		let randomness = [3; RANDOMNESS_LENGTH];
+
+		assert_eq!(
+			*secondary_slot_author(100.into(), &authorities, randomness).unwrap(),
+			authorities[167].0
+		);
+	}
 }