[lc/cosmos] consensus state at latest height is overwritten

[rnbguy]

ibc-starknet/cairo-contracts/packages/clients/src/cometbft/component.cairo

Lines 334 to 356 in c1608b6

	fn update_state(
	ref self: ComponentState<TContractState>,
	client_sequence: u64,
	client_message: Array<felt252>
	) -> UpdateResponse {
	let header: CometHeader = CometHeaderImpl::deserialize(client_message);
	let header_height = header.clone().signed_header.height;
	// TODO: Implement consensus state pruning mechanism.
	if !self.consensus_state_exists(client_sequence, header_height.clone()) {
	let mut client_state = self.read_client_state(client_sequence);
	client_state.update(header_height.clone());
	let new_consensus_state: CometConsensusState = header.into();
	self._update_state(client_sequence, client_state, new_consensus_state);
	}
	array![header_height].into()
	}

The above code tries to update a consensus state if not present. This tries to conditionally update the client_state's latest height here

ibc-starknet/cairo-contracts/packages/clients/src/cometbft/component.cairo

Line 348 in c1608b6

client_state.update(header_height.clone());

This may not actually update the latest height, if the update came from an old height.

But in the _update_state, it tries to use client_state's latest_height to store the new consensus state -- which may not really correspond to the client latest height. So for an old update height, this overwrites the latest consensus state.

ibc-starknet/cairo-contracts/packages/clients/src/cometbft/component.cairo

Lines 439 to 454 in b97e860

	fn _update_state(
	ref self: ComponentState<TContractState>,
	client_sequence: u64,
	client_state: CometClientState,
	consensus_state: CometConsensusState,
	) {
	self.write_client_state(client_sequence, client_state.clone());
	let latest_height = client_state.latest_height;
	self.write_update_height(client_sequence, latest_height.clone());
	self
	.write_consensus_state(
	client_sequence, latest_height.clone(), consensus_state.clone()
	);

You may be able to reproduce this in your cairo unit tests -- by trying updating the client state at a lower height and then checking if the new consensus state at the update height exists and the latest consensus state hasn't changed.