Add block reward contract config to ethash and allow off-chain contracts (#9312)

This adds block reward contract config to ethash. A new config `blockRewardContractCode` is also added to both Aura and ethash. When specified, it will execute the code directly and overrides any `blockRewardContractAddress` config. Having this `blockRewardContractCode` config allows chains to deploy hard fork by simply replacing the current config value, without the need from us to support any `multi` block reward scheme.

ethcore/src/engines/authority_round/mod.rs

@@ -100,7 +100,11 @@ impl From<ethjson::spec::AuthorityRoundParams> for AuthorityRoundParams {
 			immediate_transitions: p.immediate_transitions.unwrap_or(false),
 			block_reward: p.block_reward.map_or_else(Default::default, Into::into),
 			block_reward_contract_transition: p.block_reward_contract_transition.map_or(0, Into::into),
-			block_reward_contract: p.block_reward_contract_address.map(BlockRewardContract::new),
+			block_reward_contract: match (p.block_reward_contract_code, p.block_reward_contract_address) {
+				(Some(code), _) => Some(BlockRewardContract::new_from_code(Arc::new(code.into()))),
+				(_, Some(address)) => Some(BlockRewardContract::new_from_address(address.into())),
+				(None, None) => None,
+			},
 			maximum_uncle_count_transition: p.maximum_uncle_count_transition.map_or(0, Into::into),
 			maximum_uncle_count: p.maximum_uncle_count.map_or(0, Into::into),
 			empty_steps_transition: p.empty_steps_transition.map_or(u64::max_value(), |n| ::std::cmp::max(n.into(), 1)),
@@ -1043,7 +1047,7 @@ impl Engine<EthereumMachine> for AuthorityRound {
 
 	/// Apply the block reward on finalisation of the block.
 	fn on_close_block(&self, block: &mut ExecutedBlock) -> Result<(), Error> {
-		let mut benefactors = Vec::new();
+		let mut beneficiaries = Vec::new();
 		if block.header().number() >= self.empty_steps_transition {
 			let empty_steps = if block.header().seal().is_empty() {
 				// this is a new block, calculate rewards based on the empty steps messages we have accumulated
@@ -1069,32 +1073,22 @@ impl Engine<EthereumMachine> for AuthorityRound {
 
 			for empty_step in empty_steps {
 				let author = empty_step.author()?;
-				benefactors.push((author, RewardKind::EmptyStep));
+				beneficiaries.push((author, RewardKind::EmptyStep));
 			}
 		}
 
 		let author = *block.header().author();
-		benefactors.push((author, RewardKind::Author));
+		beneficiaries.push((author, RewardKind::Author));
 
 		let rewards: Vec<_> = match self.block_reward_contract {
 			Some(ref c) if block.header().number() >= self.block_reward_contract_transition => {
-				// NOTE: this logic should be moved to a function when another
+				let mut call = super::default_system_or_code_call(&self.machine, block);
-				//       engine needs support for block reward contract.
-				let mut call = |to, data| {
-					let result = self.machine.execute_as_system(
-						block,
-						to,
-						U256::max_value(), // unbounded gas? maybe make configurable.
-						Some(data),
-					);
-					result.map_err(|e| format!("{}", e))
-				};
 
-				let rewards = c.reward(&benefactors, &mut call)?;
+				let rewards = c.reward(&beneficiaries, &mut call)?;
 				rewards.into_iter().map(|(author, amount)| (author, RewardKind::External, amount)).collect()
 			},
 			_ => {
-				benefactors.into_iter().map(|(author, reward_kind)| (author, reward_kind, self.block_reward)).collect()
+				beneficiaries.into_iter().map(|(author, reward_kind)| (author, reward_kind, self.block_reward)).collect()
 			},
 		};
 

ethcore/src/engines/block_reward.rs

@@ -21,33 +21,48 @@ use ethabi;
 use ethabi::ParamType;
 use ethereum_types::{H160, Address, U256};
 
+use std::sync::Arc;
+use hash::keccak;
 use error::Error;
 use machine::WithRewards;
 use parity_machine::{Machine, WithBalances};
 use trace;
-use super::SystemCall;
+use types::BlockNumber;
+use super::{SystemOrCodeCall, SystemOrCodeCallKind};
 
 use_contract!(block_reward_contract, "BlockReward", "res/contracts/block_reward.json");
 
 /// The kind of block reward.
 /// Depending on the consensus engine the allocated block reward might have
 /// different semantics which could lead e.g. to different reward values.
-#[repr(u8)]
 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
 pub enum RewardKind {
 	/// Reward attributed to the block author.
-	Author = 0,
+	Author,
-	/// Reward attributed to the block uncle(s).
-	Uncle = 1,
 	/// Reward attributed to the author(s) of empty step(s) included in the block (AuthorityRound engine).
-	EmptyStep = 2,
+	EmptyStep,
 	/// Reward attributed by an external protocol (e.g. block reward contract).
-	External = 3,
+	External,
+	/// Reward attributed to the block uncle(s) with given difference.
+	Uncle(u8),
+}
+
+impl RewardKind {
+	/// Create `RewardKind::Uncle` from given current block number and uncle block number.
+	pub fn uncle(number: BlockNumber, uncle: BlockNumber) -> Self {
+		RewardKind::Uncle(if number > uncle && number - uncle <= u8::max_value().into() { (number - uncle) as u8 } else { 0 })
+	}
 }
 
 impl From<RewardKind> for u16 {
 	fn from(reward_kind: RewardKind) -> Self {
-		reward_kind as u16
+		match reward_kind {
+			RewardKind::Author => 0,
+			RewardKind::EmptyStep => 2,
+			RewardKind::External => 3,
+
+			RewardKind::Uncle(depth) => 100 + depth as u16,
+		}
 	}
 }
 
@@ -55,7 +70,7 @@ impl Into<trace::RewardType> for RewardKind {
 	fn into(self) -> trace::RewardType {
 		match self {
 			RewardKind::Author => trace::RewardType::Block,
-			RewardKind::Uncle => trace::RewardType::Uncle,
+			RewardKind::Uncle(_) => trace::RewardType::Uncle,
 			RewardKind::EmptyStep => trace::RewardType::EmptyStep,
 			RewardKind::External => trace::RewardType::External,
 		}
@@ -63,38 +78,50 @@ impl Into<trace::RewardType> for RewardKind {
 }
 
 /// A client for the block reward contract.
+#[derive(PartialEq, Debug)]
 pub struct BlockRewardContract {
-	/// Address of the contract.
+	kind: SystemOrCodeCallKind,
-	address: Address,
 	block_reward_contract: block_reward_contract::BlockReward,
 }
 
 impl BlockRewardContract {
-	/// Create a new block reward contract client targeting the given address.
+	/// Create a new block reward contract client targeting the system call kind.
-	pub fn new(address: Address) -> BlockRewardContract {
+	pub fn new(kind: SystemOrCodeCallKind) -> BlockRewardContract {
 		BlockRewardContract {
-			address,
+			kind,
 			block_reward_contract: block_reward_contract::BlockReward::default(),
 		}
 	}
 
-	/// Calls the block reward contract with the given benefactors list (and associated reward kind)
+	/// Create a new block reward contract client targeting the contract address.
+	pub fn new_from_address(address: Address) -> BlockRewardContract {
+		Self::new(SystemOrCodeCallKind::Address(address))
+	}
+
+	/// Create a new block reward contract client targeting the given code.
+	pub fn new_from_code(code: Arc<Vec<u8>>) -> BlockRewardContract {
+		let code_hash = keccak(&code[..]);
+
+		Self::new(SystemOrCodeCallKind::Code(code, code_hash))
+	}
+
+	/// Calls the block reward contract with the given beneficiaries list (and associated reward kind)
 	/// and returns the reward allocation (address - value). The block reward contract *must* be
 	/// called by the system address so the `caller` must ensure that (e.g. using
 	/// `machine.execute_as_system`).
 	pub fn reward(
 		&self,
-		benefactors: &[(Address, RewardKind)],
+		beneficiaries: &[(Address, RewardKind)],
-		caller: &mut SystemCall,
+		caller: &mut SystemOrCodeCall,
 	) -> Result<Vec<(Address, U256)>, Error> {
 		let reward = self.block_reward_contract.functions().reward();
 
 		let input = reward.input(
-			benefactors.iter().map(|&(address, _)| H160::from(address)),
+			beneficiaries.iter().map(|&(address, _)| H160::from(address)),
-			benefactors.iter().map(|&(_, ref reward_kind)| u16::from(*reward_kind)),
+			beneficiaries.iter().map(|&(_, ref reward_kind)| u16::from(*reward_kind)),
 		);
 
-		let output = caller(self.address, input)
+		let output = caller(self.kind.clone(), input)
 			.map_err(Into::into)
 			.map_err(::engines::EngineError::FailedSystemCall)?;
 
@@ -127,7 +154,7 @@ impl BlockRewardContract {
 	}
 }
 
-/// Applies the given block rewards, i.e. adds the given balance to each benefactors' address.
+/// Applies the given block rewards, i.e. adds the given balance to each beneficiary' address.
 /// If tracing is enabled the operations are recorded.
 pub fn apply_block_rewards<M: Machine + WithBalances + WithRewards>(
 	rewards: &[(Address, RewardKind, U256)],
@@ -149,6 +176,7 @@ mod test {
 	use spec::Spec;
 	use test_helpers::generate_dummy_client_with_spec_and_accounts;
 
+	use engines::SystemOrCodeCallKind;
 	use super::{BlockRewardContract, RewardKind};
 
 	#[test]
@@ -161,7 +189,7 @@ mod test {
 		let machine = Spec::new_test_machine();
 
 		// the spec has a block reward contract defined at the given address
-		let block_reward_contract = BlockRewardContract::new(
+		let block_reward_contract = BlockRewardContract::new_from_address(
 			"0000000000000000000000000000000000000042".into(),
 		);
 
@@ -172,30 +200,35 @@ mod test {
 				vec![],
 			).unwrap();
 
-			let result = machine.execute_as_system(
+			let result = match to {
+				SystemOrCodeCallKind::Address(to) => {
+					machine.execute_as_system(
 						block.block_mut(),
 						to,
 						U256::max_value(),
 						Some(data),
-			);
+					)
+				},
+				_ => panic!("Test reward contract is created by an address, we never reach this branch."),
+			};
 
 			result.map_err(|e| format!("{}", e))
 		};
 
-		// if no benefactors are given no rewards are attributed
+		// if no beneficiaries are given no rewards are attributed
 		assert!(block_reward_contract.reward(&vec![], &mut call).unwrap().is_empty());
 
 		// the contract rewards (1000 + kind) for each benefactor
-		let benefactors = vec![
+		let beneficiaries = vec![
 			("0000000000000000000000000000000000000033".into(), RewardKind::Author),
-			("0000000000000000000000000000000000000034".into(), RewardKind::Uncle),
+			("0000000000000000000000000000000000000034".into(), RewardKind::Uncle(1)),
 			("0000000000000000000000000000000000000035".into(), RewardKind::EmptyStep),
 		];
 
-		let rewards = block_reward_contract.reward(&benefactors, &mut call).unwrap();
+		let rewards = block_reward_contract.reward(&beneficiaries, &mut call).unwrap();
 		let expected = vec![
 			("0000000000000000000000000000000000000033".into(), U256::from(1000)),
-			("0000000000000000000000000000000000000034".into(), U256::from(1000 + 1)),
+			("0000000000000000000000000000000000000034".into(), U256::from(1000 + 101)),
 			("0000000000000000000000000000000000000035".into(), U256::from(1000 + 2)),
 		];
 

ethcore/src/engines/mod.rs

@@ -133,6 +133,46 @@ pub enum Seal {
 /// A system-calling closure. Enacts calls on a block's state from the system address.
 pub type SystemCall<'a> = FnMut(Address, Vec<u8>) -> Result<Vec<u8>, String> + 'a;
 
+/// A system-calling closure. Enacts calls on a block's state with code either from an on-chain contract, or hard-coded EVM or WASM (if enabled on-chain) codes.
+pub type SystemOrCodeCall<'a> = FnMut(SystemOrCodeCallKind, Vec<u8>) -> Result<Vec<u8>, String> + 'a;
+
+/// Kind of SystemOrCodeCall, this is either an on-chain address, or code.
+#[derive(PartialEq, Debug, Clone)]
+pub enum SystemOrCodeCallKind {
+	/// On-chain address.
+	Address(Address),
+	/// Hard-coded code.
+	Code(Arc<Vec<u8>>, H256),
+}
+
+/// Default SystemOrCodeCall implementation.
+pub fn default_system_or_code_call<'a>(machine: &'a ::machine::EthereumMachine, block: &'a mut ::block::ExecutedBlock) -> impl FnMut(SystemOrCodeCallKind, Vec<u8>) -> Result<Vec<u8>, String> + 'a {
+	move |to, data| {
+		let result = match to {
+			SystemOrCodeCallKind::Address(address) => {
+				machine.execute_as_system(
+					block,
+					address,
+					U256::max_value(),
+					Some(data),
+				)
+			},
+			SystemOrCodeCallKind::Code(code, code_hash) => {
+				machine.execute_code_as_system(
+					block,
+					None,
+					Some(code),
+					Some(code_hash),
+					U256::max_value(),
+					Some(data),
+				)
+			},
+		};
+
+		result.map_err(|e| format!("{}", e))
+	}
+}
+
 /// Type alias for a function we can get headers by hash through.
 pub type Headers<'a, H> = Fn(H256) -> Option<H> + 'a;
 

ethcore/src/engines/null_engine.rs

@@ -89,7 +89,7 @@ impl<M: WithBalances + WithRewards> Engine<M> for NullEngine<M>
 		for u in LiveBlock::uncles(&*block) {
 			let uncle_author = u.author();
 			let result_uncle_reward = (reward * U256::from(8 + u.number() - number)).shr(3);
-			rewards.push((*uncle_author, RewardKind::Uncle, result_uncle_reward));
+			rewards.push((*uncle_author, RewardKind::uncle(number, u.number()), result_uncle_reward));
 		}
 
 		block_reward::apply_block_rewards(&rewards, block, &self.machine)

ethcore/src/ethereum/ethash.rs

@@ -19,7 +19,7 @@ use std::cmp;
 use std::collections::BTreeMap;
 use std::sync::Arc;
 use hash::{KECCAK_EMPTY_LIST_RLP};
-use engines::block_reward::{self, RewardKind};
+use engines::block_reward::{self, BlockRewardContract, RewardKind};
 use ethash::{self, quick_get_difficulty, slow_hash_block_number, EthashManager, OptimizeFor};
 use ethereum_types::{H256, H64, U256, Address};
 use unexpected::{OutOfBounds, Mismatch};
@@ -124,6 +124,10 @@ pub struct EthashParams {
 	pub expip2_transition: u64,
 	/// EXPIP-2 duration limit
 	pub expip2_duration_limit: u64,
+	/// Block reward contract transition block.
+	pub block_reward_contract_transition: u64,
+	/// Block reward contract.
+	pub block_reward_contract: Option<BlockRewardContract>,
 }
 
 impl From<ethjson::spec::EthashParams> for EthashParams {
@@ -154,6 +158,12 @@ impl From<ethjson::spec::EthashParams> for EthashParams {
 			eip649_reward: p.eip649_reward.map(Into::into),
 			expip2_transition: p.expip2_transition.map_or(u64::max_value(), Into::into),
 			expip2_duration_limit: p.expip2_duration_limit.map_or(30, Into::into),
+			block_reward_contract_transition: p.block_reward_contract_transition.map_or(0, Into::into),
+			block_reward_contract: match (p.block_reward_contract_code, p.block_reward_contract_address) {
+				(Some(code), _) => Some(BlockRewardContract::new_from_code(Arc::new(code.into()))),
+				(_, Some(address)) => Some(BlockRewardContract::new_from_address(address.into())),
+				(None, None) => None,
+			},
 		}
 	}
 }
@@ -231,6 +241,22 @@ impl Engine<EthereumMachine> for Arc<Ethash> {
 		let author = *LiveBlock::header(&*block).author();
 		let number = LiveBlock::header(&*block).number();
 
+		let rewards = match self.ethash_params.block_reward_contract {
+			Some(ref c) if number >= self.ethash_params.block_reward_contract_transition => {
+				let mut beneficiaries = Vec::new();
+
+				beneficiaries.push((author, RewardKind::Author));
+				for u in LiveBlock::uncles(&*block) {
+					let uncle_author = u.author();
+					beneficiaries.push((*uncle_author, RewardKind::uncle(number, u.number())));
+				}
+
+				let mut call = engines::default_system_or_code_call(&self.machine, block);
+
+				let rewards = c.reward(&beneficiaries, &mut call)?;
+				rewards.into_iter().map(|(author, amount)| (author, RewardKind::External, amount)).collect()
+			},
+			_ => {
 				let mut rewards = Vec::new();
 
 				// Applies EIP-649 reward.
@@ -274,9 +300,13 @@ impl Engine<EthereumMachine> for Arc<Ethash> {
 						reward.shr(5)
 					};
 
-			rewards.push((*uncle_author, RewardKind::Uncle, result_uncle_reward));
+					rewards.push((*uncle_author, RewardKind::uncle(number, u.number()), result_uncle_reward));
 				}
 
+				rewards
+			},
+		};
+
 		block_reward::apply_block_rewards(&rewards, block, &self.machine)
 	}
 
@@ -512,6 +542,8 @@ mod tests {
 			eip649_reward: None,
 			expip2_transition: u64::max_value(),
 			expip2_duration_limit: 30,
+			block_reward_contract: None,
+			block_reward_contract_transition: 0,
 		}
 	}
 

ethcore/src/machine.rs

@@ -29,10 +29,10 @@ use header::{BlockNumber, Header, ExtendedHeader};
 use spec::CommonParams;
 use state::{CleanupMode, Substate};
 use trace::{NoopTracer, NoopVMTracer, Tracer, ExecutiveTracer, RewardType, Tracing};
-use transaction::{self, SYSTEM_ADDRESS, UnverifiedTransaction, SignedTransaction};
+use transaction::{self, SYSTEM_ADDRESS, UNSIGNED_SENDER, UnverifiedTransaction, SignedTransaction};
 use tx_filter::TransactionFilter;
 
-use ethereum_types::{U256, Address};
+use ethereum_types::{U256, H256, Address};
 use rlp::Rlp;
 use vm::{CallType, ActionParams, ActionValue, ParamsType};
 use vm::{EnvInfo, Schedule, CreateContractAddress};
@@ -122,6 +122,35 @@ impl EthereumMachine {
 		contract_address: Address,
 		gas: U256,
 		data: Option<Vec<u8>>,
+	) -> Result<Vec<u8>, Error> {
+		let (code, code_hash) = {
+			let state = block.state();
+
+			(state.code(&contract_address)?,
+			 state.code_hash(&contract_address)?)
+		};
+
+		self.execute_code_as_system(
+			block,
+			Some(contract_address),
+			code,
+			code_hash,
+			gas,
+			data
+		)
+	}
+
+	/// Same as execute_as_system, but execute code directly. If contract address is None, use the null sender
+	/// address. If code is None, then this function has no effect. The call is executed without finalization, and does
+	/// not form a transaction.
+	pub fn execute_code_as_system(
+		&self,
+		block: &mut ExecutedBlock,
+		contract_address: Option<Address>,
+		code: Option<Arc<Vec<u8>>>,
+		code_hash: Option<H256>,
+		gas: U256,
+		data: Option<Vec<u8>>
 	) -> Result<Vec<u8>, Error> {
 		let env_info = {
 			let mut env_info = block.env_info();
@@ -130,31 +159,27 @@ impl EthereumMachine {
 		};
 
 		let mut state = block.state_mut();
+
 		let params = ActionParams {
-			code_address: contract_address.clone(),
+			code_address: contract_address.unwrap_or(UNSIGNED_SENDER),
-			address: contract_address.clone(),
+			address: contract_address.unwrap_or(UNSIGNED_SENDER),
-			sender: SYSTEM_ADDRESS.clone(),
+			sender: SYSTEM_ADDRESS,
-			origin: SYSTEM_ADDRESS.clone(),
+			origin: SYSTEM_ADDRESS,
-			gas: gas,
+			gas,
 			gas_price: 0.into(),
 			value: ActionValue::Transfer(0.into()),
-			code: state.code(&contract_address)?,
+			code,
-			code_hash: state.code_hash(&contract_address)?,
+			code_hash,
-			data: data,
+			data,
 			call_type: CallType::Call,
 			params_type: ParamsType::Separate,
 		};
 		let schedule = self.schedule(env_info.number);
 		let mut ex = Executive::new(&mut state, &env_info, self, &schedule);
 		let mut substate = Substate::new();
-		let res = ex.call(params, &mut substate, &mut NoopTracer, &mut NoopVMTracer);
+
-		let output = match res {
+		let res = ex.call(params, &mut substate, &mut NoopTracer, &mut NoopVMTracer).map_err(|e| ::engines::EngineError::FailedSystemCall(format!("{}", e)))?;
-			Ok(res) => res.return_data.to_vec(),
+		let output = res.return_data.to_vec();
-			Err(e) => {
-				warn!("Encountered error on making system call: {}", e);
-				Vec::new()
-			}
-		};
 
 		Ok(output)
 	}

json/src/spec/authority_round.rs

@@ -16,8 +16,9 @@
 
 //! Authority params deserialization.
 
-use ethereum_types::Address;
+use hash::Address;
 use uint::Uint;
+use bytes::Bytes;
 use super::ValidatorSet;
 
 /// Authority params deserialization.
@@ -51,6 +52,9 @@ pub struct AuthorityRoundParams {
 	/// overrides the static block reward definition).
 	#[serde(rename="blockRewardContractAddress")]
 	pub block_reward_contract_address: Option<Address>,
+	/// Block reward code. This overrides the block reward contract address.
+	#[serde(rename="blockRewardContractCode")]
+	pub block_reward_contract_code: Option<Bytes>,
 	/// Block at which maximum uncle count should be considered.
 	#[serde(rename="maximumUncleCountTransition")]
 	pub maximum_uncle_count_transition: Option<Uint>,

json/src/spec/ethash.rs

@@ -17,6 +17,7 @@
 //! Ethash params deserialization.
 
 use uint::{self, Uint};
+use bytes::Bytes;
 use hash::Address;
 
 /// Deserializable doppelganger of EthashParams.
@@ -48,6 +49,16 @@ pub struct EthashParams {
 	/// Reward per block in wei.
 	#[serde(rename="blockReward")]
 	pub block_reward: Option<Uint>,
+	/// Block at which the block reward contract should start being used.
+	#[serde(rename="blockRewardContractTransition")]
+	pub block_reward_contract_transition: Option<Uint>,
+	/// Block reward contract address (setting the block reward contract
+	/// overrides all other block reward parameters).
+	#[serde(rename="blockRewardContractAddress")]
+	pub block_reward_contract_address: Option<Address>,
+	/// Block reward code. This overrides the block reward contract address.
+	#[serde(rename="blockRewardContractCode")]
+	pub block_reward_contract_code: Option<Bytes>,
 
 	/// See main EthashParams docs.
 	#[serde(rename="daoHardforkTransition")]
@@ -191,6 +202,9 @@ mod tests {
 				duration_limit: Some(Uint(U256::from(0x0d))),
 				homestead_transition: Some(Uint(U256::from(0x42))),
 				block_reward: Some(Uint(U256::from(0x100))),
+				block_reward_contract_address: None,
+				block_reward_contract_code: None,
+				block_reward_contract_transition: None,
 				dao_hardfork_transition: Some(Uint(U256::from(0x08))),
 				dao_hardfork_beneficiary: Some(Address(H160::from("0xabcabcabcabcabcabcabcabcabcabcabcabcabca"))),
 				dao_hardfork_accounts: Some(vec![
@@ -256,6 +270,9 @@ mod tests {
 				duration_limit: None,
 				homestead_transition: None,
 				block_reward: None,
+				block_reward_contract_address: None,
+				block_reward_contract_code: None,
+				block_reward_contract_transition: None,
 				dao_hardfork_transition: None,
 				dao_hardfork_beneficiary: None,
 				dao_hardfork_accounts: None,