Ignore checkpoint if it contains less than 2 epochs instead

lib/src/chain_spec.rs

@@ -420,9 +420,15 @@ fn convert_epoch(epoch: &light_sync_state::BabeEpoch) -> BabeEpochInformation {
 }
 
 impl LightSyncState {
-    pub fn to_chain_information(&self) -> Result<ValidChainInformation, InvalidCheckpointError> {
+    pub fn to_chain_information(
+        &self,
+    ) -> Result<ValidChainInformation, CheckpointToChainInformationError> {
         // TODO: this code is a bit of a shitshow when it comes to corner cases and should be cleaned up after https://github.com/paritytech/substrate/issues/11184
 
+        if self.inner.finalized_block_header.number == 0 {
+            return Err(CheckpointToChainInformationError::GenesisBlockCheckpoint);
+        }
+
         // Create a sorted list of all regular epochs that haven't been pruned from the sync state.
         let mut epochs: Vec<_> = self
             .inner
@@ -444,22 +450,18 @@ impl LightSyncState {
         epochs.dedup_by_key(|(_, epoch)| epoch.epoch_index);
 
         // Get the latest two epochs.
-        let finalized_block_epoch_information = if epochs.len() >= 2 {
-            Some(convert_epoch(epochs[epochs.len() - 2].1))
-        } else {
-            None
-        };
-        if epochs.is_empty() {
-            return Err(InvalidCheckpointError::EmptyBabeEpochsList);
+        if epochs.len() < 2 {
+            return Err(CheckpointToChainInformationError::GenesisBlockCheckpoint);
         }
+        let current_epoch = epochs[epochs.len() - 2].1;
         let next_epoch = epochs[epochs.len() - 1].1;
 
         ChainInformation {
             finalized_block_header: self.inner.finalized_block_header.clone(),
             consensus: ChainInformationConsensus::Babe {
                 slots_per_epoch: NonZeroU64::new(next_epoch.duration)
-                    .ok_or(InvalidCheckpointError::InvalidBabeSlotsPerEpoch)?,
-                finalized_block_epoch_information,
+                    .ok_or(CheckpointToChainInformationError::InvalidBabeSlotsPerEpoch)?,
+                finalized_block_epoch_information: Some(convert_epoch(current_epoch)),
                 finalized_next_epoch_transition: convert_epoch(next_epoch),
             },
             finality: ChainInformationFinality::Grandpa {
@@ -473,7 +475,7 @@ impl LightSyncState {
                             Ok(crate::header::GrandpaAuthority {
                                 public_key: authority.public_key,
                                 weight: NonZeroU64::new(authority.weight)
-                                    .ok_or(InvalidCheckpointError::InvalidGrandpaAuthorityWeight)?,
+                                    .ok_or(CheckpointToChainInformationError::InvalidGrandpaAuthorityWeight)?,
                             })
                         })
                         .collect::<Result<_, _>>()?
@@ -482,7 +484,7 @@ impl LightSyncState {
             },
         }
         .try_into()
-        .map_err(InvalidCheckpointError::InvalidData)
+        .map_err(CheckpointToChainInformationError::InvalidData)
     }
 }
 
@@ -515,11 +517,11 @@ pub enum FromGenesisStorageError {
     UnknownStorageItems,
 }
 
-/// Error when building the chain information from the genesis storage.
+/// Error when building the chain information corresponding to a checkpoint.
 #[derive(Debug, derive_more::Display)]
-pub enum InvalidCheckpointError {
-    /// The list of Babe epochs is empty.
-    EmptyBabeEpochsList,
+pub enum CheckpointToChainInformationError {
+    /// The checkpoint corresponds to the genesis block.
+    GenesisBlockCheckpoint,
     /// Found a value of 0 for the number of Babe slots per epoch.
     InvalidBabeSlotsPerEpoch,
     /// Found a Grandpa authority with a weight of 0.

light-base/src/lib.rs

@@ -464,20 +464,27 @@ impl<TPlat: platform::PlatformRef, TChain> Client<TPlat, TChain> {
 
                 (Err(err), _, _) => return Err(AddChainError::InvalidGenesisStorage(err)),
 
-                (_, Some(Err(err)), _) => {
-                    return Err(AddChainError::InvalidCheckpoint(err));
-                }
-
                 (Ok(genesis_ci), Some(Ok(checkpoint)), _) => {
                     let genesis_header = genesis_ci.as_ref().finalized_block_header.clone();
                     (checkpoint, genesis_header.into(), Default::default())
                 }
 
-                (Ok(genesis_ci), None, _) => {
+                (
+                    Ok(genesis_ci),
+                    None
+                    | Some(Err(
+                        chain_spec::CheckpointToChainInformationError::GenesisBlockCheckpoint,
+                    )),
+                    _,
+                ) => {
                     let genesis_header =
                         header::Header::from(genesis_ci.as_ref().finalized_block_header.clone());
                     (genesis_ci, genesis_header, Default::default())
                 }
+
+                (_, Some(Err(err)), _) => {
+                    return Err(AddChainError::InvalidCheckpoint(err));
+                }
             }
         };
 
@@ -1009,7 +1016,7 @@ pub enum AddChainError {
     ChainSpecNeitherGenesisStorageNorCheckpoint,
     /// Checkpoint provided in the chain specification is invalid.
     #[display(fmt = "Invalid checkpoint in chain specification: {_0}")]
-    InvalidCheckpoint(chain_spec::InvalidCheckpointError),
+    InvalidCheckpoint(chain_spec::CheckpointToChainInformationError),
     /// Failed to build the information about the chain from the genesis storage. This indicates
     /// invalid data in the genesis storage.
     #[display(fmt = "Failed to build genesis chain information: {_0}")]

wasm-node/CHANGELOG.md

@@ -4,8 +4,8 @@
 
 ### Fixed
 
-- Fix panic when the checkpoint in the chain specification contains an empty list of Babe epochs, which can normally only happen if the checkpoint was modified manually. ([#603](https://github.com/smol-dot/smoldot/pull/603))
-- Fix panic when the checkpoint in the chain specification contains only one Babe epoch, which can happen if the checkpoint was generated before any block was authored. ([#603](https://github.com/smol-dot/smoldot/pull/603))
+- Fix panic when the checkpoint in the chain specification is invalid, which can normally only happen if the checkpoint was modified manually. ([#603](https://github.com/smol-dot/smoldot/pull/603))
+- Fix panic when the checkpoint in the chain specification contains zero or one Babe epochs, which can happen if the checkpoint was generated before any block was authored. ([#603](https://github.com/smol-dot/smoldot/pull/603))
 
 ## 1.0.6 - 2023-05-09