feat(entropy): Limit number of hashes (#1822)

* Add revert reasons to Entropy tests

* Revert if numHashes > maxNumHashes

* Add update commitment function

* Set maximum number of hashes in contract + keeper

apps/fortuna/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "fortuna"
-version = "6.4.2"
+version = "6.5.2"
 edition = "2021"
 
 [dependencies]

apps/fortuna/src/chain/ethereum.rs

@@ -28,6 +28,7 @@ use {
  abi::RawLog,
  contract::{
  abigen,
+ ContractCall,
  EthLogDecode,
  },
  core::types::Address,
@@ -72,17 +73,18 @@ abigen!(
  "../../target_chains/ethereum/entropy_sdk/solidity/abis/IEntropy.json"
 );
 
-pub type SignablePythContractInner<T> = PythRandom<
- LegacyTxMiddleware<
- GasOracleMiddleware<
- NonceManagerMiddleware<SignerMiddleware<Provider<T>, LocalWallet>>,
- EthProviderOracle<Provider<T>>,
- >,
+pub type MiddlewaresWrapper<T> = LegacyTxMiddleware<
+ GasOracleMiddleware<
+ NonceManagerMiddleware<SignerMiddleware<Provider<T>, LocalWallet>>,
+ EthProviderOracle<Provider<T>>,
  >,
 >;
+pub type SignablePythContractInner<T> = PythRandom<MiddlewaresWrapper<T>>;
 pub type SignablePythContract = SignablePythContractInner<Http>;
 pub type InstrumentedSignablePythContract = SignablePythContractInner<TracedClient>;
 
+pub type PythContractCall = ContractCall<MiddlewaresWrapper<TracedClient>, ()>;
+
 pub type PythContract = PythRandom<Provider<Http>>;
 pub type InstrumentedPythContract = PythRandom<Provider<TracedClient>>;
 

apps/fortuna/src/command/setup_provider.rs

@@ -193,6 +193,14 @@ async fn setup_chain_provider(
  .in_current_span()
  .await?;
 
+ sync_max_num_hashes(
+ &contract,
+ &provider_info,
+ chain_config.max_num_hashes.unwrap_or(0),
+ )
+ .in_current_span()
+ .await?;
+
  Ok(())
 }
 
@@ -248,3 +256,23 @@ async fn sync_fee_manager(
  }
  Ok(())
 }
+
+
+async fn sync_max_num_hashes(
+ contract: &Arc<SignablePythContract>,
+ provider_info: &ProviderInfo,
+ max_num_hashes: u32,
+) -> Result<()> {
+ if provider_info.max_num_hashes != max_num_hashes {
+ tracing::info!("Updating provider max num hashes to {:?}", max_num_hashes);
+ if let Some(receipt) = contract
+ .set_max_num_hashes(max_num_hashes)
+ .send()
+ .await?
+ .await?
+ {
+ tracing::info!("Updated provider max num hashes to : {:?}", receipt);
+ }
+ }
+ Ok(())
+}

apps/fortuna/src/config.rs

@@ -183,6 +183,10 @@ pub struct EthereumConfig {
 
  /// Historical commitments made by the provider.
  pub commitments: Option<Vec<Commitment>>,
+
+ /// Maximum number of hashes to record in a request.
+ /// This should be set according to the maximum gas limit the provider supports for callbacks.
+ pub max_num_hashes: Option<u32>,
 }
 
 

apps/fortuna/src/keeper.rs

@@ -10,6 +10,7 @@ use {
  ethereum::{
  InstrumentedPythContract,
  InstrumentedSignablePythContract,
+ PythContractCall,
  },
  reader::{
  BlockNumber,
@@ -87,6 +88,10 @@ const TRACK_INTERVAL: Duration = Duration::from_secs(10);
 const WITHDRAW_INTERVAL: Duration = Duration::from_secs(300);
 /// Check whether we need to adjust the fee at this interval.
 const ADJUST_FEE_INTERVAL: Duration = Duration::from_secs(30);
+/// Check whether we need to manually update the commitments to reduce numHashes for future
+/// requests and reduce the gas cost of the reveal.
+const UPDATE_COMMITMENTS_INTERVAL: Duration = Duration::from_secs(30);
+const UPDATE_COMMITMENTS_THRESHOLD_FACTOR: f64 = 0.95;
 /// Rety last N blocks
 const RETRY_PREVIOUS_BLOCKS: u64 = 100;
 
@@ -314,6 +319,8 @@ pub async fn run_keeper_threads(
  .in_current_span(),
  );
 
+ spawn(update_commitments_loop(contract.clone(), chain_state.clone()).in_current_span());
+
 
  // Spawn a thread to track the provider info and the balance of the keeper
  spawn(
@@ -960,28 +967,46 @@ pub async fn withdraw_fees_if_necessary(
  if keeper_balance < min_balance && U256::from(fees) > min_balance {
  tracing::info!("Claiming accrued fees...");
  let contract_call = contract.withdraw_as_fee_manager(provider_address, fees);
- let pending_tx = contract_call
- .send()
- .await
- .map_err(|e| anyhow!("Error submitting the withdrawal transaction: {:?}", e))?;
-
- let tx_result = pending_tx
- .await
- .map_err(|e| anyhow!("Error waiting for withdrawal transaction receipt: {:?}", e))?
- .ok_or_else(|| anyhow!("Can't verify the withdrawal, probably dropped from mempool"))?;
-
- tracing::info!(
- transaction_hash = &tx_result.transaction_hash.to_string(),
- "Withdrew fees to keeper address. Receipt: {:?}",
- tx_result,
- );
+ send_and_confirm(contract_call).await?;
  } else if keeper_balance < min_balance {
  tracing::warn!("Keeper balance {:?} is too low (< {:?}) but provider fees are not sufficient to top-up.", keeper_balance, min_balance)
  }
 
  Ok(())
 }
 
+pub async fn send_and_confirm(contract_call: PythContractCall) -> Result<()> {
+ let call_name = contract_call.function.name.as_str();
+ let pending_tx = contract_call
+ .send()
+ .await
+ .map_err(|e| anyhow!("Error submitting transaction({}) {:?}", call_name, e))?;
+
+ let tx_result = pending_tx
+ .await
+ .map_err(|e| {
+ anyhow!(
+ "Error waiting for transaction({}) receipt: {:?}",
+ call_name,
+ e
+ )
+ })?
+ .ok_or_else(|| {
+ anyhow!(
+ "Can't verify the transaction({}), probably dropped from mempool",
+ call_name
+ )
+ })?;
+
+ tracing::info!(
+ transaction_hash = &tx_result.transaction_hash.to_string(),
+ "Confirmed transaction({}). Receipt: {:?}",
+ call_name,
+ tx_result,
+ );
+ Ok(())
+}
+
 #[tracing::instrument(name = "adjust_fee", skip_all)]
 pub async fn adjust_fee_wrapper(
  contract: Arc<InstrumentedSignablePythContract>,
@@ -1020,6 +1045,55 @@ pub async fn adjust_fee_wrapper(
  }
 }
 
+#[tracing::instrument(name = "update_commitments", skip_all)]
+pub async fn update_commitments_loop(
+ contract: Arc<InstrumentedSignablePythContract>,
+ chain_state: BlockchainState,
+) {
+ loop {
+ if let Err(e) = update_commitments_if_necessary(contract.clone(), &chain_state)
+ .in_current_span()
+ .await
+ {
+ tracing::error!("Update commitments. error: {:?}", e);
+ }
+ time::sleep(UPDATE_COMMITMENTS_INTERVAL).await;
+ }
+}
+
+
+pub async fn update_commitments_if_necessary(
+ contract: Arc<InstrumentedSignablePythContract>,
+ chain_state: &BlockchainState,
+) -> Result<()> {
+ //TODO: we can reuse the result from the last call from the watch_blocks thread to reduce RPCs
+ let latest_safe_block = get_latest_safe_block(&chain_state).in_current_span().await;
+ let provider_address = chain_state.provider_address;
+ let provider_info = contract
+ .get_provider_info(provider_address)
+ .block(latest_safe_block) // To ensure we are not revealing sooner than we should
+ .call()
+ .await
+ .map_err(|e| anyhow!("Error while getting provider info. error: {:?}", e))?;
+ if provider_info.max_num_hashes == 0 {
+ return Ok(());
+ }
+ let threshold =
+ ((provider_info.max_num_hashes as f64) * UPDATE_COMMITMENTS_THRESHOLD_FACTOR) as u64;
+ if provider_info.sequence_number - provider_info.current_commitment_sequence_number > threshold
+ {
+ let seq_number = provider_info.sequence_number - 1;
+ let provider_revelation = chain_state
+ .state
+ .reveal(seq_number)
+ .map_err(|e| anyhow!("Error revealing: {:?}", e))?;
+ let contract_call =
+ contract.advance_provider_commitment(provider_address, seq_number, provider_revelation);
+ send_and_confirm(contract_call).await?;
+ }
+ Ok(())
+}
+
 /// Adjust the fee charged by the provider to ensure that it is profitable at the prevailing gas price.
 /// This method targets a fee as a function of the maximum cost of the callback,
 /// c = (gas_limit) * (current gas price), with min_fee_wei as a lower bound on the fee.
@@ -1105,23 +1179,7 @@ pub async fn adjust_fee_if_necessary(
  target_fee
  );
  let contract_call = contract.set_provider_fee_as_fee_manager(provider_address, target_fee);
- let pending_tx = contract_call
- .send()
- .await
- .map_err(|e| anyhow!("Error submitting the set fee transaction: {:?}", e))?;
-
- let tx_result = pending_tx
- .await
- .map_err(|e| anyhow!("Error waiting for set fee transaction receipt: {:?}", e))?
- .ok_or_else(|| {
- anyhow!("Can't verify the set fee transaction, probably dropped from mempool")
- })?;
-
- tracing::info!(
- transaction_hash = &tx_result.transaction_hash.to_string(),
- "Set provider fee. Receipt: {:?}",
- tx_result,
- );
+ send_and_confirm(contract_call).await?;
 
  *sequence_number_of_last_fee_update = Some(provider_info.sequence_number);
  } else {

target_chains/ethereum/contracts/contracts/entropy/Entropy.sol

@@ -234,6 +234,12 @@ abstract contract Entropy is IEntropy, EntropyState {
  assignedSequenceNumber -
  providerInfo.currentCommitmentSequenceNumber
  );
+ if (
+ providerInfo.maxNumHashes != 0 &&
+ req.numHashes > providerInfo.maxNumHashes
+ ) {
+ revert EntropyErrors.LastRevealedTooOld();
+ }
  req.commitment = keccak256(
  bytes.concat(userCommitment, providerInfo.currentCommitment)
  );
@@ -351,6 +357,51 @@ abstract contract Entropy is IEntropy, EntropyState {
  }
  }
 
+ // Advance the provider commitment and increase the sequence number.
+ // This is used to reduce the `numHashes` required for future requests which leads to reduced gas usage.
+ function advanceProviderCommitment(
+ address provider,
+ uint64 advancedSequenceNumber,
+ bytes32 providerRevelation
+ ) public override {
+ EntropyStructs.ProviderInfo storage providerInfo = _state.providers[
+ provider
+ ];
+ if (
+ advancedSequenceNumber <=
+ providerInfo.currentCommitmentSequenceNumber
+ ) revert EntropyErrors.UpdateTooOld();
+ if (advancedSequenceNumber >= providerInfo.endSequenceNumber)
+ revert EntropyErrors.AssertionFailure();
+
+ uint32 numHashes = SafeCast.toUint32(
+ advancedSequenceNumber -
+ providerInfo.currentCommitmentSequenceNumber
+ );
+ bytes32 providerCommitment = constructProviderCommitment(
+ numHashes,
+ providerRevelation
+ );
+
+ if (providerCommitment != providerInfo.currentCommitment)
+ revert EntropyErrors.IncorrectRevelation();
+
+ providerInfo.currentCommitmentSequenceNumber = advancedSequenceNumber;
+ providerInfo.currentCommitment = providerRevelation;
+ if (
+ providerInfo.currentCommitmentSequenceNumber >=
+ providerInfo.sequenceNumber
+ ) {
+ // This means the provider called the function with a sequence number that was not yet requested.
+ // Providers should never do this and we consider such an implementation flawed.
+ // Assuming this is landed on-chain it's better to bump the sequence number and never use that range
+ // for future requests. Otherwise, someone can use the leaked revelation to derive favorable random numbers.
+ providerInfo.sequenceNumber =
+ providerInfo.currentCommitmentSequenceNumber +
+ 1;
+ }
+ }
+
  // Fulfill a request for a random number. This method validates the provided userRandomness and provider's proof
  // against the corresponding commitments in the in-flight request. If both values are validated, this function returns
  // the corresponding random number.
@@ -555,6 +606,25 @@ abstract contract Entropy is IEntropy, EntropyState {
  emit ProviderFeeManagerUpdated(msg.sender, oldFeeManager, manager);
  }
 
+ // Set the maximum number of hashes to record in a request. This should be set according to the maximum gas limit
+ // the provider supports for callbacks.
+ function setMaxNumHashes(uint32 maxNumHashes) external override {
+ EntropyStructs.ProviderInfo storage provider = _state.providers[
+ msg.sender
+ ];
+ if (provider.sequenceNumber == 0) {
+ revert EntropyErrors.NoSuchProvider();
+ }
+
+ uint32 oldMaxNumHashes = provider.maxNumHashes;
+ provider.maxNumHashes = maxNumHashes;
+ emit ProviderMaxNumHashesAdvanced(
+ msg.sender,
+ oldMaxNumHashes,
+ maxNumHashes
+ );
+ }
+
  function constructUserCommitment(
  bytes32 userRandomness
  ) public pure override returns (bytes32 userCommitment) {

target_chains/ethereum/contracts/contracts/entropy/EntropyUpgradable.sol

@@ -105,6 +105,6 @@ contract EntropyUpgradable is
  }
 
  function version() public pure returns (string memory) {
- return "0.3.1";
+ return "0.4.0";
  }
 }