fix: do not perform future timestamp checks post-merge (#3884)

Co-authored-by: Matthias Seitz <matthias.seitz@outlook.de>

crates/consensus/beacon/src/beacon_consensus.rs

@@ -2,10 +2,10 @@
 use reth_consensus_common::validation;
 use reth_interfaces::consensus::{Consensus, ConsensusError};
 use reth_primitives::{
-    constants::MAXIMUM_EXTRA_DATA_SIZE, Chain, ChainSpec, Hardfork, Header, SealedBlock,
-    SealedHeader, EMPTY_OMMER_ROOT, U256,
+    constants::{ALLOWED_FUTURE_BLOCK_TIME_SECONDS, MAXIMUM_EXTRA_DATA_SIZE},
+    Chain, ChainSpec, Hardfork, Header, SealedBlock, SealedHeader, EMPTY_OMMER_ROOT, U256,
 };
-use std::sync::Arc;
+use std::{sync::Arc, time::SystemTime};
 
 /// Ethereum beacon consensus
 ///
@@ -59,6 +59,14 @@ impl Consensus for BeaconConsensus {
                 return Err(ConsensusError::TheMergeOmmerRootIsNotEmpty)
             }
 
+            // Post-merge, the consensus layer is expected to perform checks such that the block
+            // timestamp is a function of the slot. This is different from pre-merge, where blocks
+            // are only allowed to be in the future (compared to the system's clock) by a certain
+            // threshold.
+            //
+            // Block validation with respect to the parent should ensure that the block timestamp
+            // is greater than its parent timestamp.
+
             // validate header extradata for all networks post merge
             validate_header_extradata(header)?;
 
@@ -69,6 +77,17 @@ impl Consensus for BeaconConsensus {
             //  * difficulty, mix_hash & nonce aka PoW stuff
             // low priority as syncing is done in reverse order
 
+            // Check if timestamp is in future. Clock can drift but this can be consensus issue.
+            let present_timestamp =
+                SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap().as_secs();
+
+            if header.timestamp > present_timestamp + ALLOWED_FUTURE_BLOCK_TIME_SECONDS {
+                return Err(ConsensusError::TimestampIsInFuture {
+                    timestamp: header.timestamp,
+                    present_timestamp,
+                })
+            }
+
             // Goerli exception:
             //  * If the network is goerli pre-merge, ignore the extradata check, since we do not
             //  support clique.

crates/consensus/common/src/validation.rs

@@ -5,10 +5,7 @@ use reth_primitives::{
     SealedHeader, Transaction, TransactionSignedEcRecovered, TxEip1559, TxEip2930, TxLegacy,
 };
 use reth_provider::{AccountReader, HeaderProvider, WithdrawalsProvider};
-use std::{
-    collections::{hash_map::Entry, HashMap},
-    time::SystemTime,
-};
+use std::collections::{hash_map::Entry, HashMap};
 
 /// Validate header standalone
 pub fn validate_header_standalone(
@@ -23,16 +20,6 @@ pub fn validate_header_standalone(
         })
     }
 
-    // Check if timestamp is in future. Clock can drift but this can be consensus issue.
-    let present_timestamp =
-        SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap().as_secs();
-    if header.timestamp > present_timestamp {
-        return Err(ConsensusError::TimestampIsInFuture {
-            timestamp: header.timestamp,
-            present_timestamp,
-        })
-    }
-
     // Check if base fee is set.
     if chain_spec.fork(Hardfork::London).active_at_block(header.number) &&
         header.base_fee_per_gas.is_none()

crates/primitives/src/constants.rs

@@ -108,6 +108,15 @@ pub const EMPTY_WITHDRAWALS: H256 = EMPTY_SET_HASH;
 /// the database.
 pub const BEACON_CONSENSUS_REORG_UNWIND_DEPTH: u64 = 3;
 
+/// Max seconds from current time allowed for blocks, before they're considered future blocks.
+///
+/// This is only used when checking whether or not the timestamp for pre-merge blocks is in the
+/// future.
+///
+/// See:
+/// <https://github.com/ethereum/go-ethereum/blob/a196f3e8a22b6ad22ced5c2e3baf32bc3ebd4ec9/consensus/ethash/consensus.go#L227-L229>
+pub const ALLOWED_FUTURE_BLOCK_TIME_SECONDS: u64 = 15;
+
 #[cfg(test)]
 mod tests {
     use super::*;