Missing Timestamp Validation

[apopiak]

The validation logic no longer includes the timestamp check inherents:

polkadot-sdk/templates/parachain/runtime/src/lib.rs

Lines 312 to 316 in dae4b9c

	#[docify::export(register_validate_block)]
	cumulus_pallet_parachain_system::register_validate_block! {
	Runtime = Runtime,
	BlockExecutor = cumulus_pallet_aura_ext::BlockExecutor::<Runtime, Executive>,
	}

But it still includes pallet timestamp:

polkadot-sdk/templates/parachain/runtime/src/lib.rs

Line 269 in dae4b9c

pub type Timestamp = pallet_timestamp;

We should either remove pallet timestamp or make use of the new consensus hook to check it, otherwise builders might rely on unvalidated timestamps.

[apopiak]

See discussion here:
#2841

[bkchr]

The timestamp is verified implicit by OnTimeStampSet:

polkadot-sdk/cumulus/parachains/runtimes/assets/asset-hub-westend/src/lib.rs

Line 214 in 0a36fce

type OnTimestampSet = Aura;

We are verifying the slot against the relay chain state in the ConsensusHook and then the slot is checked against the timestamp inside the timestamp pallet. So, it is validated.

But yeah, this is ultra complicated and not really clear in any way. We could probably introduce some more obvious CheckTimestamp thingy that could do the check.

[RomarQ]

For custom consensus engines this is an important step:

polkadot-sdk/cumulus/client/consensus/aura/src/collator.rs

Lines 161 to 163 in e68836d

	if let Some(timestamp) = timestamp.into() {
	other_inherent_data.replace_data(sp_timestamp::INHERENT_IDENTIFIER, &timestamp);
	}

polkadot-sdk/substrate/docs/Upgrading-2.0-to-3.0.md

Line 1076 in e68836d

+ inherent_data.replace_data(sp_timestamp::INHERENT_IDENTIFIER, &(slot * SLOT_DURATION));

Currently adapting it for nimbus.