atomic-swap/ethereum/check_swap_creator_contract.go

// Copyright 2023 The AthanorLabs/atomic-swap Authors
// SPDX-License-Identifier: LGPL-3.0-only

package contracts

import (
	"bytes"
	"context"
	"errors"
	"fmt"

	"github.com/athanorlabs/atomic-swap/common"

	"github.com/athanorlabs/go-relayer/impls/gsnforwarder"
	ethcommon "github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/ethclient"
)

// expectedSwapCreatorBytecodeHex is generated by deploying an instance of SwapCreator.sol
// with the trustedForwarder address set to all zeros and reading back the bytecode. See
// the unit test TestExpectedSwapCreatorBytecodeHex if you need to update this value.
const (
	expectedSwapCreatorBytecodeHex = "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18a61182b565b611d5e602083018961182b565b611d6b604083018861182b565b611d786060830187611ab0565b611d856080830186611ab0565b611d9260a0830185611652565b611d9f60c0830184611ab0565b9897505050505050505056fea264697066735822122084f522d05ed6af1060846f3e30d11805736fb4d34a12fcf1a991eced80ebd24a64736f6c63430008130033" //nolint:lll

	ethAddrByteLen = len(ethcommon.Address{}) // 20 bytes
)

// forwarderAddrIndices is a slice of the start indices where the trusted forwarder
// address is compiled into the deployed contract byte code. When verifying the bytecode
// of a deployed contract, we need special treatment for these identical 20-byte address
// blocks. See TestForwarderAddrIndexes to update the values.
var forwarderAddrIndices = []int{1490, 1528}

var (
	errInvalidSwapCreatorContract = errors.New("given contract address does not contain correct SwapCreator code")
	errInvalidForwarderContract   = errors.New("given contract address does not contain correct Forwarder code")
)

// CheckSwapCreatorContractCode checks that the bytecode at the given address matches the
// SwapCreator.sol contract. The trusted forwarder address that the contract was deployed
// with is parsed out from the byte code and returned.
func CheckSwapCreatorContractCode(
	ctx context.Context,
	ec *ethclient.Client,
	contractAddr ethcommon.Address,
) (ethcommon.Address, error) {
	code, err := ec.CodeAt(ctx, contractAddr, nil)
	if err != nil {
		return ethcommon.Address{}, err
	}

	expectedCode := ethcommon.FromHex(expectedSwapCreatorBytecodeHex)

	if len(code) != len(expectedCode) {
		return ethcommon.Address{}, fmt.Errorf("length mismatch: %w", errInvalidSwapCreatorContract)
	}

	allZeroAddr := ethcommon.Address{}

	// we fill this in with the trusted forwarder that the contract was deployed with
	var forwarderAddr ethcommon.Address

	for i, addrIndex := range forwarderAddrIndices {
		curAddr := code[addrIndex : addrIndex+ethAddrByteLen]
		if i == 0 {
			// initialise the trusted forwarder address on the first index
			copy(forwarderAddr[:], curAddr)
		} else {
			// check that any remaining forwarder addresses match the one we found at the first index
			if !bytes.Equal(curAddr, forwarderAddr[:]) {
				return ethcommon.Address{}, errInvalidSwapCreatorContract
			}
		}

		// Zero out the trusted forwarder address in the code, so that we can compare the
		// read in byte code with a copy of the contract code that was deployed using an
		// all-zero trusted forwarder address. curAddr and code have the same backing
		// array, so we are updating expectedCode as well here:
		copy(curAddr, allZeroAddr[:])
	}

	// Now that the trusted forwarder addresses have been zeroed out, the read-in contract code should
	// match the expected code.
	if !bytes.Equal(expectedCode, code) {
		return ethcommon.Address{}, errInvalidSwapCreatorContract
	}

	if (forwarderAddr == ethcommon.Address{}) {
		return forwarderAddr, nil
	}

	err = CheckForwarderContractCode(ctx, ec, forwarderAddr)
	if err != nil {
		return ethcommon.Address{}, err
	}

	// return the trusted forwarder address that was parsed from the deployed contract byte code
	return forwarderAddr, nil
}

// CheckForwarderContractCode checks that the trusted forwarder contract used by
// the given swap contract has the expected bytecode.
func CheckForwarderContractCode(
	ctx context.Context,
	ec *ethclient.Client,
	contractAddr ethcommon.Address,
) error {
	// mainnet override - since the forwarder contract deployed on mainnet is compiled
	// with solidity 0.8.7, but we're using 0.8.19 for SwapCreator.sol, we can just
	// check that the address is what's expected.
	chainID, err := ec.ChainID(ctx)
	if err != nil {
		return err
	}

	if contractAddr == common.MainnetConfig().ForwarderAddr && chainID.Uint64() == common.MainnetChainID {
		return nil
	}

	code, err := ec.CodeAt(ctx, contractAddr, nil)
	if err != nil {
		return err
	}

	expectedCode := ethcommon.FromHex(gsnforwarder.ForwarderMetaData.Bin)

	// expectedCode is the compiled code, while code is the deployed bytecode.
	// the deployed bytecode is a subset of the compiled code.
	if !bytes.Equal(expectedCode[705:9585], code) {
		return errInvalidForwarderContract
	}

	return nil
}