Smash out the router library

processor/ethereum/router/Cargo.toml

@@ -0,0 +1,49 @@
+[package]
+name = "serai-processor-ethereum-router"
+version = "0.1.0"
+description = "The Router used by the Serai Processor for Ethereum"
+license = "AGPL-3.0-only"
+repository = "https://github.com/serai-dex/serai/tree/develop/processor/ethereum/router"
+authors = ["Luke Parker <lukeparker5132@gmail.com>"]
+edition = "2021"
+publish = false
+rust-version = "1.79"
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+[lints]
+workspace = true
+
+[dependencies]
+group = { version = "0.13", default-features = false }
+k256 = { version = "^0.13.1", default-features = false, features = ["std", "ecdsa", "arithmetic"] }
+
+alloy-core = { version = "0.8", default-features = false }
+alloy-consensus = { version = "0.3", default-features = false }
+
+alloy-sol-types = { version = "0.8", default-features = false }
+alloy-sol-macro = { version = "0.8", default-features = false }
+
+alloy-rpc-types-eth = { version = "0.3", default-features = false }
+alloy-transport = { version = "0.3", default-features = false }
+alloy-simple-request-transport = { path = "../../../networks/ethereum/alloy-simple-request-transport", default-features = false }
+alloy-provider = { version = "0.3", default-features = false }
+
+ethereum-schnorr = { package = "ethereum-schnorr-contract", path = "../../../networks/ethereum/schnorr", default-features = false }
+
+ethereum-primitives = { package = "serai-processor-ethereum-primitives", path = "../primitives", default-features = false }
+ethereum-deployer = { package = "serai-processor-ethereum-deployer", path = "../deployer", default-features = false }
+erc20 = { package = "serai-processor-ethereum-erc20", path = "../erc20", default-features = false }
+
+serai-client = { path = "../../../substrate/client", default-features = false, features = ["ethereum"] }
+
+[build-dependencies]
+build-solidity-contracts = { path = "../../../networks/ethereum/build-contracts", default-features = false }
+
+syn = { version = "2", default-features = false, features = ["proc-macro"] }
+
+syn-solidity = { version = "0.8", default-features = false }
+alloy-sol-macro-input = { version = "0.8", default-features = false }
+alloy-sol-macro-expander = { version = "0.8", default-features = false }

processor/ethereum/router/LICENSE

@@ -0,0 +1,15 @@
+AGPL-3.0-only license
+
+Copyright (c) 2022-2024 Luke Parker
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License Version 3 as
+published by the Free Software Foundation.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.

processor/ethereum/router/README.md

@@ -0,0 +1 @@
+# Ethereum Router

processor/ethereum/router/build.rs

@@ -0,0 +1,42 @@
+use std::{env, fs};
+
+use alloy_sol_macro_input::SolInputKind;
+
+fn write(sol: syn_solidity::File, file: &str) {
+  let sol = alloy_sol_macro_expander::expand::expand(sol).unwrap();
+  fs::write(file, sol.to_string()).unwrap();
+}
+
+fn sol(sol_files: &[&str], file: &str) {
+  let mut sol = String::new();
+  for sol_file in sol_files {
+    sol += &fs::read_to_string(sol_file).unwrap();
+  }
+  let SolInputKind::Sol(sol) = syn::parse_str(&sol).unwrap() else {
+    panic!("parsed .sols file wasn't SolInputKind::Sol");
+  };
+  write(sol, file);
+}
+
+fn main() {
+  let artifacts_path =
+    env::var("OUT_DIR").unwrap().to_string() + "/serai-processor-ethereum-router";
+
+  if !fs::exists(&artifacts_path).unwrap() {
+    fs::create_dir(&artifacts_path).unwrap();
+  }
+
+  build_solidity_contracts::build(
+    &["../../../networks/ethereum/schnorr/contracts", "../erc20/contracts"],
+    "contracts",
+    &artifacts_path,
+  )
+  .unwrap();
+
+  // This cannot be handled with the sol! macro. The Solidity requires an import
+  // https://github.com/alloy-rs/core/issues/602
+  sol(
+    &["../../../networks/ethereum/schnorr/contracts/Schnorr.sol", "contracts/Router.sol"],
+    &(artifacts_path + "/router.rs"),
+  );
+}

processor/ethereum/router/contracts/Router.sol

@@ -0,0 +1,219 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+pragma solidity ^0.8.26;
+
+import "IERC20.sol";
+
+import "Schnorr.sol";
+
+// _ is used as a prefix for internal functions and smart-contract-scoped variables
+contract Router {
+  // Nonce is incremented for each command executed, preventing replays
+  uint256 private _nonce;
+
+  // The nonce which will be used for the smart contracts we deploy, enabling
+  // predicting their addresses
+  uint256 private _smartContractNonce;
+
+  // The current public key, defined as per the Schnorr library
+  bytes32 private _seraiKey;
+
+  enum DestinationType {
+    Address,
+    Code
+  }
+
+  struct AddressDestination {
+    address destination;
+  }
+
+  struct CodeDestination {
+    uint32 gas;
+    bytes code;
+  }
+
+  struct OutInstruction {
+    DestinationType destinationType;
+    bytes destination;
+    address coin;
+    uint256 value;
+  }
+
+  struct Signature {
+    bytes32 c;
+    bytes32 s;
+  }
+
+  event SeraiKeyUpdated(uint256 indexed nonce, bytes32 indexed key);
+  event InInstruction(
+    address indexed from, address indexed coin, uint256 amount, bytes instruction
+  );
+  event Executed(uint256 indexed nonce, bytes32 indexed message_hash);
+
+  error InvalidSignature();
+  error InvalidAmount();
+  error FailedTransfer();
+
+  // Update the Serai key at the end of the current function.
+  modifier _updateSeraiKeyAtEndOfFn(uint256 nonceUpdatedWith, bytes32 newSeraiKey) {
+    // Run the function itself.
+    _;
+
+    // Update the key.
+    _seraiKey = newSeraiKey;
+    emit SeraiKeyUpdated(nonceUpdatedWith, newSeraiKey);
+  }
+
+  constructor(bytes32 initialSeraiKey) _updateSeraiKeyAtEndOfFn(0, initialSeraiKey) {
+    // We consumed nonce 0 when setting the initial Serai key
+    _nonce = 1;
+    // Nonces are incremented by 1 upon account creation, prior to any code execution, per EIP-161
+    // This is incompatible with any networks which don't have their nonces start at 0
+    _smartContractNonce = 1;
+  }
+
+  // updateSeraiKey validates the given Schnorr signature against the current public key, and if
+  // successful, updates the contract's public key to the one specified.
+  function updateSeraiKey(bytes32 newSeraiKey, Signature calldata signature)
+    external
+    _updateSeraiKeyAtEndOfFn(_nonce, newSeraiKey)
+  {
+    bytes32 message = keccak256(abi.encodePacked("updateSeraiKey", block.chainid, _nonce, newSeraiKey));
+    _nonce++;
+
+    if (!Schnorr.verify(_seraiKey, message, signature.c, signature.s)) {
+      revert InvalidSignature();
+    }
+  }
+
+  function inInstruction(address coin, uint256 amount, bytes memory instruction) external payable {
+    if (coin == address(0)) {
+      if (amount != msg.value) {
+        revert InvalidAmount();
+      }
+    } else {
+      (bool success, bytes memory res) = address(coin).call(
+        abi.encodeWithSelector(IERC20.transferFrom.selector, msg.sender, address(this), amount)
+      );
+
+      // Require there was nothing returned, which is done by some non-standard tokens, or that the
+      // ERC20 contract did in fact return true
+      bool nonStandardResOrTrue = (res.length == 0) || abi.decode(res, (bool));
+      if (!(success && nonStandardResOrTrue)) {
+        revert FailedTransfer();
+      }
+    }
+
+    /*
+      Due to fee-on-transfer tokens, emitting the amount directly is frowned upon. The amount
+      instructed to be transferred may not actually be the amount transferred.
+
+      If we add nonReentrant to every single function which can effect the balance, we can check the
+      amount exactly matches. This prevents transfers of less value than expected occurring, at
+      least, not without an additional transfer to top up the difference (which isn't routed through
+      this contract and accordingly isn't trying to artificially create events from this contract).
+
+      If we don't add nonReentrant, a transfer can be started, and then a new transfer for the
+      difference can follow it up (again and again until a rounding error is reached). This contract
+      would believe all transfers were done in full, despite each only being done in part (except
+      for the last one).
+
+      Given fee-on-transfer tokens aren't intended to be supported, the only token actively planned
+      to be supported is Dai and it doesn't have any fee-on-transfer logic, and how fee-on-transfer
+      tokens aren't even able to be supported at this time by the larger Serai network, we simply
+      classify this entire class of tokens as non-standard implementations which induce undefined
+      behavior.
+
+      It is the Serai network's role not to add support for any non-standard implementations.
+    */
+    emit InInstruction(msg.sender, coin, amount, instruction);
+  }
+
+  // Perform a transfer out
+  function _transferOut(address to, address coin, uint256 value) private {
+    /*
+      We on purposely do not check if these calls succeed. A call either succeeded, and there's no
+      problem, or the call failed due to:
+        A) An insolvency
+        B) A malicious receiver
+        C) A non-standard token
+      A is an invariant, B should be dropped, C is something out of the control of this contract.
+      It is again the Serai's network role to not add support for any non-standard tokens,
+    */
+    if (coin == address(0)) {
+      // Enough gas to service the transfer and a minimal amount of logic
+      // TODO: If we're constructing a contract, we can do this at the same time as construction
+      to.call{ value: value, gas: 5_000 }("");
+    } else {
+      coin.call{ gas: 100_000 }(abi.encodeWithSelector(IERC20.transfer.selector, msg.sender, value));
+    }
+  }
+
+  /*
+    Serai supports arbitrary calls out via deploying smart contracts (with user-specified code),
+    letting them execute whatever calls they're coded for. Since we can't meter CREATE, we call
+    CREATE from this function which we call not internally, but with CALL (which we can meter).
+  */
+  function arbitaryCallOut(bytes memory code) external {
+    // Because we're creating a contract, increment our nonce
+    _smartContractNonce += 1;
+
+    address contractAddress;
+    assembly {
+      contractAddress := create(0, add(code, 0x20), mload(code))
+    }
+  }
+
+  // Execute a list of transactions if they were signed by the current key with the current nonce
+  function execute(OutInstruction[] calldata transactions, Signature calldata signature) external {
+    // Verify the signature
+    // We hash the message here as we need the message's hash for the Executed event
+    // Since we're already going to hash it, hashing it prior to verifying the signature reduces the
+    // amount of words hashed by its challenge function (reducing our gas costs)
+    bytes32 message = keccak256(abi.encode("execute", block.chainid, _nonce, transactions));
+    if (!Schnorr.verify(_seraiKey, message, signature.c, signature.s)) {
+      revert InvalidSignature();
+    }
+
+    // Since the signature was verified, perform execution
+    emit Executed(_nonce, message);
+    // While this is sufficient to prevent replays, it's still technically possible for instructions
+    // from later batches to be executed before these instructions upon re-entrancy
+    _nonce++;
+
+    for (uint256 i = 0; i < transactions.length; i++) {
+      // If the destination is an address, we perform a direct transfer
+      if (transactions[i].destinationType == DestinationType.Address) {
+        // This may cause a panic and the contract to become stuck if the destination isn't actually
+        // 20 bytes. Serai is trusted to not pass a malformed destination
+        (AddressDestination memory destination) = abi.decode(transactions[i].destination, (AddressDestination));
+        _transferOut(destination.destination, transactions[i].coin, transactions[i].value);
+      } else {
+        // The destination is a piece of initcode. We calculate the hash of the will-be contract,
+        // transfer to it, and then run the initcode
+        address nextAddress =
+          address(uint160(uint256(keccak256(abi.encode(address(this), _smartContractNonce)))));
+
+        // Perform the transfer
+        _transferOut(nextAddress, transactions[i].coin, transactions[i].value);
+
+        // Perform the calls with a set gas budget
+        (CodeDestination memory destination) = abi.decode(transactions[i].destination, (CodeDestination));
+        address(this).call{ gas: destination.gas }(
+          abi.encodeWithSelector(Router.arbitaryCallOut.selector, destination.code)
+        );
+      }
+    }
+  }
+
+  function nonce() external view returns (uint256) {
+    return _nonce;
+  }
+
+  function smartContractNonce() external view returns (uint256) {
+    return _smartContractNonce;
+  }
+
+  function seraiKey() external view returns (bytes32) {
+    return _seraiKey;
+  }
+}

processor/ethereum/router/src/lib.rs

@@ -0,0 +1,582 @@
+#![cfg_attr(docsrs, feature(doc_auto_cfg))]
+#![doc = include_str!("../README.md")]
+#![deny(missing_docs)]
+
+use std::{sync::Arc, io, collections::HashSet};
+
+use group::ff::PrimeField;
+
+/*
+use k256::{
+  elliptic_curve::{group::GroupEncoding, sec1},
+  ProjectivePoint,
+};
+*/
+
+use alloy_core::primitives::{hex::FromHex, Address, U256, Bytes, TxKind};
+use alloy_consensus::TxLegacy;
+
+use alloy_sol_types::{SolValue, SolConstructor, SolCall, SolEvent};
+
+use alloy_rpc_types_eth::Filter;
+use alloy_transport::{TransportErrorKind, RpcError};
+use alloy_simple_request_transport::SimpleRequest;
+use alloy_provider::{Provider, RootProvider};
+
+use ethereum_schnorr::{PublicKey, Signature};
+use ethereum_deployer::Deployer;
+use erc20::Transfer;
+
+use serai_client::{primitives::Amount, networks::ethereum::Address as SeraiAddress};
+
+#[rustfmt::skip]
+#[expect(warnings)]
+#[expect(needless_pass_by_value)]
+#[expect(clippy::all)]
+#[expect(clippy::ignored_unit_patterns)]
+#[expect(clippy::redundant_closure_for_method_calls)]
+mod _abi {
+  include!(concat!(env!("OUT_DIR"), "/serai-processor-ethereum-router/router.rs"));
+}
+use _abi::Router as abi;
+use abi::{
+  SeraiKeyUpdated as SeraiKeyUpdatedEvent, InInstruction as InInstructionEvent,
+  Executed as ExecutedEvent,
+};
+
+impl From<&Signature> for abi::Signature {
+  fn from(signature: &Signature) -> Self {
+    Self {
+      c: <[u8; 32]>::from(signature.c().to_repr()).into(),
+      s: <[u8; 32]>::from(signature.s().to_repr()).into(),
+    }
+  }
+}
+
+/// A coin on Ethereum.
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub enum Coin {
+  /// Ether, the native coin of Ethereum.
+  Ether,
+  /// An ERC20 token.
+  Erc20([u8; 20]),
+}
+
+impl Coin {
+  /// Read a `Coin`.
+  pub fn read<R: io::Read>(reader: &mut R) -> io::Result<Self> {
+    let mut kind = [0xff];
+    reader.read_exact(&mut kind)?;
+    Ok(match kind[0] {
+      0 => Coin::Ether,
+      1 => {
+        let mut address = [0; 20];
+        reader.read_exact(&mut address)?;
+        Coin::Erc20(address)
+      }
+      _ => Err(io::Error::other("unrecognized Coin type"))?,
+    })
+  }
+
+  /// Write the `Coin`.
+  pub fn write<W: io::Write>(&self, writer: &mut W) -> io::Result<()> {
+    match self {
+      Coin::Ether => writer.write_all(&[0]),
+      Coin::Erc20(token) => {
+        writer.write_all(&[1])?;
+        writer.write_all(token)
+      }
+    }
+  }
+}
+
+/// An InInstruction from the Router.
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct InInstruction {
+  /// The ID for this `InInstruction`.
+  pub id: ([u8; 32], u64),
+  /// The address which transferred these coins to Serai.
+  pub from: [u8; 20],
+  /// The coin transferred.
+  pub coin: Coin,
+  /// The amount transferred.
+  pub amount: U256,
+  /// The data associated with the transfer.
+  pub data: Vec<u8>,
+}
+
+impl InInstruction {
+  /// Read an `InInstruction`.
+  pub fn read<R: io::Read>(reader: &mut R) -> io::Result<Self> {
+    let id = {
+      let mut id_hash = [0; 32];
+      reader.read_exact(&mut id_hash)?;
+      let mut id_pos = [0; 8];
+      reader.read_exact(&mut id_pos)?;
+      let id_pos = u64::from_le_bytes(id_pos);
+      (id_hash, id_pos)
+    };
+
+    let mut from = [0; 20];
+    reader.read_exact(&mut from)?;
+
+    let coin = Coin::read(reader)?;
+    let mut amount = [0; 32];
+    reader.read_exact(&mut amount)?;
+    let amount = U256::from_le_slice(&amount);
+
+    let mut data_len = [0; 4];
+    reader.read_exact(&mut data_len)?;
+    let data_len = usize::try_from(u32::from_le_bytes(data_len))
+      .map_err(|_| io::Error::other("InInstruction data exceeded 2**32 in length"))?;
+    let mut data = vec![0; data_len];
+    reader.read_exact(&mut data)?;
+
+    Ok(InInstruction { id, from, coin, amount, data })
+  }
+
+  /// Write the `InInstruction`.
+  pub fn write<W: io::Write>(&self, writer: &mut W) -> io::Result<()> {
+    writer.write_all(&self.id.0)?;
+    writer.write_all(&self.id.1.to_le_bytes())?;
+
+    writer.write_all(&self.from)?;
+
+    self.coin.write(writer)?;
+    writer.write_all(&self.amount.as_le_bytes())?;
+
+    writer.write_all(
+      &u32::try_from(self.data.len())
+        .map_err(|_| {
+          io::Error::other("InInstruction being written had data exceeding 2**32 in length")
+        })?
+        .to_le_bytes(),
+    )?;
+    writer.write_all(&self.data)
+  }
+}
+
+/// Executed an command.
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub enum Executed {
+  /// Set a new key.
+  SetKey {
+    /// The nonce this was done with.
+    nonce: u64,
+    /// The key set.
+    key: [u8; 32],
+  },
+  /// Executed Batch.
+  Batch {
+    /// The nonce this was done with.
+    nonce: u64,
+    /// The hash of the signed message for the Batch executed.
+    message_hash: [u8; 32],
+  },
+}
+
+impl Executed {
+  /// The nonce consumed by this executed event.
+  pub fn nonce(&self) -> u64 {
+    match self {
+      Executed::SetKey { nonce, .. } | Executed::Batch { nonce, .. } => *nonce,
+    }
+  }
+}
+
+/// A view of the Router for Serai.
+#[derive(Clone, Debug)]
+pub struct Router(Arc<RootProvider<SimpleRequest>>, Address);
+impl Router {
+  pub(crate) fn code() -> Vec<u8> {
+    const BYTECODE: &[u8] =
+      include_bytes!(concat!(env!("OUT_DIR"), "/serai-processor-ethereum-router/Router.bin"));
+    Bytes::from_hex(BYTECODE).expect("compiled-in Router bytecode wasn't valid hex").to_vec()
+  }
+
+  pub(crate) fn init_code(key: &PublicKey) -> Vec<u8> {
+    let mut bytecode = Self::code();
+    // Append the constructor arguments
+    bytecode.extend((abi::constructorCall { initialSeraiKey: key.eth_repr().into() }).abi_encode());
+    bytecode
+  }
+
+  /// Create a new view of the Router.
+  ///
+  /// This performs an on-chain lookup for the first deployed Router constructed with this public
+  /// key. This lookup is of a constant amount of calls and does not read any logs.
+  pub async fn new(
+    provider: Arc<RootProvider<SimpleRequest>>,
+    initial_serai_key: &PublicKey,
+  ) -> Result<Option<Self>, RpcError<TransportErrorKind>> {
+    let Some(deployer) = Deployer::new(provider.clone()).await? else {
+      return Ok(None);
+    };
+    let Some(deployment) = deployer
+      .find_deployment(ethereum_primitives::keccak256(Self::init_code(initial_serai_key)))
+      .await?
+    else {
+      return Ok(None);
+    };
+    Ok(Some(Self(provider, deployment)))
+  }
+
+  /// The address of the router.
+  pub fn address(&self) -> Address {
+    self.1
+  }
+
+  /// Construct a transaction to update the key representing Serai.
+  pub fn update_serai_key(&self, public_key: &PublicKey, sig: &Signature) -> TxLegacy {
+    // TODO: Set a more accurate gas
+    TxLegacy {
+      to: TxKind::Call(self.1),
+      input: abi::updateSeraiKeyCall::new((public_key.eth_repr().into(), sig.into()))
+        .abi_encode()
+        .into(),
+      gas_limit: 100_000,
+      ..Default::default()
+    }
+  }
+
+  /// Construct a transaction to execute a batch of `OutInstruction`s.
+  pub fn execute(&self, outs: &[(SeraiAddress, (Coin, Amount))], sig: &Signature) -> TxLegacy {
+    TxLegacy {
+      to: TxKind::Call(self.1),
+      input: abi::executeCall::new((
+        outs
+          .iter()
+          .map(|(address, (coin, amount))| {
+            #[allow(non_snake_case)]
+            let (destinationType, destination) = match address {
+              SeraiAddress::Address(address) => (
+                abi::DestinationType::Address,
+                (abi::AddressDestination { destination: Address::from(address) }).abi_encode(),
+              ),
+              SeraiAddress::Contract(contract) => (
+                abi::DestinationType::Code,
+                (abi::CodeDestination {
+                  gas: contract.gas(),
+                  code: contract.code().to_vec().into(),
+                })
+                .abi_encode(),
+              ),
+            };
+            abi::OutInstruction {
+              destinationType,
+              destination: destination.into(),
+              coin: match coin {
+                Coin::Ether => [0; 20].into(),
+                Coin::Erc20(address) => address.into(),
+              },
+              value: amount.0.try_into().expect("couldn't convert u64 to u256"),
+            }
+          })
+          .collect(),
+        sig.into(),
+      ))
+      .abi_encode()
+      .into(),
+      // TODO
+      gas_limit: 100_000 + ((200_000 + 10_000) * u128::try_from(outs.len()).unwrap()),
+      ..Default::default()
+    }
+  }
+
+  /*
+  /// Get the key for Serai at the specified block.
+  #[cfg(test)]
+  pub async fn serai_key(&self, at: [u8; 32]) -> Result<PublicKey, RpcError<TransportErrorKind>> {
+    let call = TransactionRequest::default()
+      .to(self.1)
+      .input(TransactionInput::new(abi::seraiKeyCall::new(()).abi_encode().into()));
+    let bytes = self
+      .0
+      .call(&call)
+      .block(BlockId::Hash(B256::from(at).into()))
+      .await
+      ?;
+    let res =
+      abi::seraiKeyCall::abi_decode_returns(&bytes, true)?;
+    PublicKey::from_eth_repr(res._0.0).ok_or_else(|| TransportErrorKind::Custom(
+    "TODO".to_string().into()))
+  }
+  */
+
+  /*
+  /// Get the message to be signed in order to update the key for Serai.
+  pub(crate) fn update_serai_key_message(chain_id: U256, nonce: U256, key: &PublicKey) -> Vec<u8> {
+    let mut buffer = b"updateSeraiKey".to_vec();
+    buffer.extend(&chain_id.to_be_bytes::<32>());
+    buffer.extend(&nonce.to_be_bytes::<32>());
+    buffer.extend(&key.eth_repr());
+    buffer
+  }
+  */
+
+  /*
+  /// Get the current nonce for the published batches.
+  #[cfg(test)]
+  pub async fn nonce(&self, at: [u8; 32]) -> Result<U256, RpcError<TransportErrorKind>> {
+    let call = TransactionRequest::default()
+      .to(self.1)
+      .input(TransactionInput::new(abi::nonceCall::new(()).abi_encode().into()));
+    let bytes = self
+      .0
+      .call(&call)
+      .block(BlockId::Hash(B256::from(at).into()))
+      .await
+      ?;
+    let res =
+      abi::nonceCall::abi_decode_returns(&bytes, true)?;
+    Ok(res._0)
+  }
+  */
+
+  /*
+  /// Get the message to be signed in order to update the key for Serai.
+  pub(crate) fn execute_message(
+    chain_id: U256,
+    nonce: U256,
+    outs: Vec<abi::OutInstruction>,
+  ) -> Vec<u8> {
+    ("execute".to_string(), chain_id, nonce, outs).abi_encode_params()
+  }
+  */
+
+  /// Fetch the `InInstruction`s emitted by the Router from this block.
+  pub async fn in_instructions(
+    &self,
+    block: u64,
+    allowed_tokens: &HashSet<[u8; 20]>,
+  ) -> Result<Vec<InInstruction>, RpcError<TransportErrorKind>> {
+    // The InInstruction events for this block
+    let filter = Filter::new().from_block(block).to_block(block).address(self.1);
+    let filter = filter.event_signature(InInstructionEvent::SIGNATURE_HASH);
+    let logs = self.0.get_logs(&filter).await?;
+
+    /*
+      We check that for all InInstructions for ERC20s emitted, a corresponding transfer occurred.
+      In order to prevent a transfer from being used to justify multiple distinct InInstructions,
+      we insert the transfer's log index into this HashSet.
+    */
+    let mut transfer_check = HashSet::new();
+
+    let mut in_instructions = vec![];
+    for log in logs {
+      // Double check the address which emitted this log
+      if log.address() != self.1 {
+        Err(TransportErrorKind::Custom(
+          "node returned a log from a different address than requested".to_string().into(),
+        ))?;
+      }
+
+      let id = (
+        log
+          .block_hash
+          .ok_or_else(|| {
+            TransportErrorKind::Custom("log didn't have its block hash set".to_string().into())
+          })?
+          .into(),
+        log.log_index.ok_or_else(|| {
+          TransportErrorKind::Custom("log didn't have its index set".to_string().into())
+        })?,
+      );
+
+      let tx_hash = log.transaction_hash.ok_or_else(|| {
+        TransportErrorKind::Custom("log didn't have its transaction hash set".to_string().into())
+      })?;
+      let tx = self.0.get_transaction_by_hash(tx_hash).await?.ok_or_else(|| {
+        TransportErrorKind::Custom(
+          "node didn't have a transaction it had the logs of".to_string().into(),
+        )
+      })?;
+
+      let log = log
+        .log_decode::<InInstructionEvent>()
+        .map_err(|e| {
+          TransportErrorKind::Custom(
+            format!("filtered to InInstructionEvent yet couldn't decode log: {e:?}").into(),
+          )
+        })?
+        .inner
+        .data;
+
+      let coin = if log.coin.0 == [0; 20] {
+        Coin::Ether
+      } else {
+        let token = *log.coin.0;
+
+        if !allowed_tokens.contains(&token) {
+          continue;
+        }
+
+        /*
+          If this also counts as a top-level transfer of a token, drop it.
+
+          This event will only exist if there's an ERC20 which has some form of programmability
+          (`onTransferFrom`), and when a top-level transfer was made, that hook made its own call
+          into the Serai router.
+
+          If such an ERC20 exists, Serai would parse it as a top-level transfer and as a router
+          InInstruction. While no such ERC20 is planned to be integrated, this enures we don't
+          allow a double-spend on that premise.
+
+          TODO: See below note.
+        */
+        if tx.to == Some(token.into()) {
+          continue;
+        }
+
+        // Get all logs for this TX
+        let receipt = self.0.get_transaction_receipt(tx_hash).await?.ok_or_else(|| {
+          TransportErrorKind::Custom(
+            "node didn't have the receipt for a transaction it had".to_string().into(),
+          )
+        })?;
+        let tx_logs = receipt.inner.logs();
+
+        /*
+          TODO: If this is also a top-level transfer, drop the log from the top-level transfer and
+          only iterate over the rest of the logs.
+        */
+
+        // Find a matching transfer log
+        let mut found_transfer = false;
+        for tx_log in tx_logs {
+          let log_index = tx_log.log_index.ok_or_else(|| {
+            TransportErrorKind::Custom(
+              "log in transaction receipt didn't have its log index set".to_string().into(),
+            )
+          })?;
+          // Ensure we didn't already use this transfer to check a distinct InInstruction event
+          if transfer_check.contains(&log_index) {
+            continue;
+          }
+
+          // Check if this log is from the token we expected to be transferred
+          if tx_log.address().0 != token {
+            continue;
+          }
+          // Check if this is a transfer log
+          // https://github.com/alloy-rs/core/issues/589
+          if tx_log.topics()[0] != Transfer::SIGNATURE_HASH {
+            continue;
+          }
+          let Ok(transfer) = Transfer::decode_log(&tx_log.inner.clone(), true) else { continue };
+          // Check if this is a transfer to us for the expected amount
+          if (transfer.to == self.1) && (transfer.value == log.amount) {
+            transfer_check.insert(log_index);
+            found_transfer = true;
+            break;
+          }
+        }
+        if !found_transfer {
+          // This shouldn't be a simple error
+          // This is an exploit, a non-conforming ERC20, or a malicious connection
+          // This should halt the process. While this is sufficient, it's sub-optimal
+          // TODO
+          Err(TransportErrorKind::Custom(
+            "ERC20 InInstruction with no matching transfer log".to_string().into(),
+          ))?;
+        }
+
+        Coin::Erc20(token)
+      };
+
+      in_instructions.push(InInstruction {
+        id,
+        from: *log.from.0,
+        coin,
+        amount: log.amount,
+        data: log.instruction.as_ref().to_vec(),
+      });
+    }
+
+    Ok(in_instructions)
+  }
+
+  /// Fetch the executed actions from this block.
+  pub async fn executed(&self, block: u64) -> Result<Vec<Executed>, RpcError<TransportErrorKind>> {
+    let mut res = vec![];
+
+    {
+      let filter = Filter::new().from_block(block).to_block(block).address(self.1);
+      let filter = filter.event_signature(SeraiKeyUpdatedEvent::SIGNATURE_HASH);
+      let logs = self.0.get_logs(&filter).await?;
+
+      for log in logs {
+        // Double check the address which emitted this log
+        if log.address() != self.1 {
+          Err(TransportErrorKind::Custom(
+            "node returned a log from a different address than requested".to_string().into(),
+          ))?;
+        }
+
+        let log = log
+          .log_decode::<SeraiKeyUpdatedEvent>()
+          .map_err(|e| {
+            TransportErrorKind::Custom(
+              format!("filtered to SeraiKeyUpdatedEvent yet couldn't decode log: {e:?}").into(),
+            )
+          })?
+          .inner
+          .data;
+
+        res.push(Executed::SetKey {
+          nonce: log.nonce.try_into().map_err(|e| {
+            TransportErrorKind::Custom(format!("filtered to convert nonce to u64: {e:?}").into())
+          })?,
+          key: log.key.into(),
+        });
+      }
+    }
+
+    {
+      let filter = Filter::new().from_block(block).to_block(block).address(self.1);
+      let filter = filter.event_signature(ExecutedEvent::SIGNATURE_HASH);
+      let logs = self.0.get_logs(&filter).await?;
+
+      for log in logs {
+        // Double check the address which emitted this log
+        if log.address() != self.1 {
+          Err(TransportErrorKind::Custom(
+            "node returned a log from a different address than requested".to_string().into(),
+          ))?;
+        }
+
+        let log = log
+          .log_decode::<ExecutedEvent>()
+          .map_err(|e| {
+            TransportErrorKind::Custom(
+              format!("filtered to ExecutedEvent yet couldn't decode log: {e:?}").into(),
+            )
+          })?
+          .inner
+          .data;
+
+        res.push(Executed::Batch {
+          nonce: log.nonce.try_into().map_err(|e| {
+            TransportErrorKind::Custom(format!("filtered to convert nonce to u64: {e:?}").into())
+          })?,
+          message_hash: log.message_hash.into(),
+        });
+      }
+    }
+
+    res.sort_by_key(Executed::nonce);
+
+    Ok(res)
+  }
+
+  /*
+  #[cfg(feature = "tests")]
+  pub fn key_updated_filter(&self) -> Filter {
+    Filter::new().address(self.1).event_signature(SeraiKeyUpdated::SIGNATURE_HASH)
+  }
+  #[cfg(feature = "tests")]
+  pub fn executed_filter(&self) -> Filter {
+    Filter::new().address(self.1).event_signature(ExecutedEvent::SIGNATURE_HASH)
+  }
+  */
+}