EVM Simulator

Abstract

EVM Simulator is a tool to simulate EVM blockchain transactions without sending them to the network. This is done by running a local "soft" fork of any EVM chain and sending the transaction locally to process its logs and the executed opcodes.

A simulated transaction can be done from any to any address without needing the source EOA keys.

Quick start

npm i -g evm-simulator

evm-simulator --help

Simulation flow

EVM Simulator is using Ganache to run a local fork of the EVM chain. It then, unlocks the source EOA and sends the transaction to the local fork. Upon receiving the transaction, Ganache will process it and return the logs and the opcodes that were executed using the debug_traceTransaction RPC method.

opcodes are then processed in order to catch internal transfers while logs emitted by smart contract events are decoded to human-readable data using their ABI (fetched from openchain.xyz using their signature).

Usage

EVM Simulator

Options:
  -V, --version               output the version number
  -c, --chain  [value]        Chain id (default: "1")
  -b, --blockheight  [value]  Block height to fork from
  --rpc  [value]              Chain rpc (default: "https://ethereum.publicnode.com")
  --from  [value]             Source EOA
  --to  [value]               Transaction target
  --value  [value]            Sent ETH value (in ETH)
  --data  [value]             Contract call data (hex string)
  -h, --help                  display help for command

Output

A successful simulation returns a SimulationResult object.

export class SimulationResult {
    from: string;
    to: string;

    gasUsed: BigNumber;
    cumulativeGasUsed: BigNumber;
    effectiveGasPrice: BigNumber;

    baseAssetTransfer?: TransferEvent;
    internalTransfers?: TransferEvent[];

    logs: object[];
}

export class TransferEvent {
    from: string;
    to: string;
    value: string;
}

Example

Here is an example from a real transaction (hash: 0xbcec995cfadc8fabf2b2c87b41ffb7ae287344da47da99fd0ff968fefd9dd989) on the Ethereum mainnet.

Input

yarn start \
--from 0x156f058c67a22f96076ce8dabe14d40a90f971ee \
--to 0x7a250d5630b4cf539739df2c5dacb4c659f2488d \
--value 0.0055 \
-c 1 \
-b 17136115 \
--data 0x7ff36ab500000000000000000000000000000000000000000000000000000d80a111d6aa0000000000000000000000000000000000000000000000000000000000000080000000000000000000000000156f058c67a22f96076ce8dabe14d40a90f971ee00000000000000000000000000000000000000000000000000000000644a2c720000000000000000000000000000000000000000000000000000000000000002000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc200000000000000000000000033cb1438e2443cdb44b18d6f2de1491d1f77a8ee \
--rpc https://mainnet.infura.io/v3/<api_key>

Output

{
  "internalTransfers": [
    {
      "from": "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D",
      "to": "000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc2",
      "value": "5500000000000000"
    }
  ],
  "baseAssetTransfer": {
    "from": "0x156f058C67A22f96076CE8DabE14d40a90f971eE",
    "to": "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D",
    "value": "5500000000000000"
  },
  "from": "0x156f058C67A22f96076CE8DabE14d40a90f971eE",
  "to": "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D",
  "gasUsed": {
    "type": "BigNumber",
    "hex": "0x021c21"
  },
  "cumulativeGasUsed": {
    "type": "BigNumber",
    "hex": "0x021c21"
  },
  "effectiveGasPrice": {
    "type": "BigNumber",
    "hex": "0x06cc0e8fd4"
  },
  "logs": [
    {
      "event": "Deposit(address,uint256)",
      "params": [
        "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D",
        "5500000000000000"
      ]
    },
    {
      "event": "Transfer(address,address,uint256)",
      "params": [
        "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D",
        "0x689d240D8C16d9fa7A678e9693c0b089458aDaAD",
        "5500000000000000"
      ]
    },
    {
      "event": "Transfer(address,address,uint256)",
      "params": [
        "0x689d240D8C16d9fa7A678e9693c0b089458aDaAD",
        "0x33cb1438E2443cDb44b18D6f2DE1491D1F77A8ee",
        "311768294792"
      ]
    },
    {
      "event": "Transfer(address,address,uint256)",
      "params": [
        "0x689d240D8C16d9fa7A678e9693c0b089458aDaAD",
        "0x156f058C67A22f96076CE8DabE14d40a90f971eE",
        "15276646444817"
      ]
    },
    {
      "event": "Sync(uint112,uint112)",
      "params": [
        "4134681071579214",
        "1459947038696920352"
      ]
    },
    {
      "event": "Swap(address,uint256,uint256,uint256,uint256,address)",
      "params": [
        "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D",
        "122364672243051157726927388588417579627688063470",
        "0",
        "5500000000000000",
        "15588414739609",
        "0x0000000000000000000000000000000000000000"
      ]
    }
  ]
}

Future plans

• Decode input contract calls data (fetch ABI from Etherscan)
• Run local server for wallets to be able to send transactions directly from dApps (maybe proxy to real net upon simulation approval?)