smart-contract-watch

A smart contract monitoring tool. It can monitor smart contracts activity and interactions based on generated transactions and events.For example, It can be used a local blockchain explorer that runs locally on your server or machine ,or as an investigation tool that scrapes the blockchain in search for a specific query. This is done by sending requests to an Ethereum node via JSON RPC calls.

NOTE: You need to connect to an already functional Ethereum node in order for this tool to run.

Modes

Currently the smart-contract-watch runs in two modes:

• Default mode: in this mode the tool scans the blockchain block by block, transaction by transaction and log by log for any activity related to the specified smart contracts. This is a slow processes and heavy on the node due to the high number of eth_getTransactionByHash and eth_getTransactionReceipt RPC requests. However, this approach gives the opportunity to add more features in the future like instrumenting the EVM or debugging transactions.

• Quick mode: in this mode the tool scans the blockchain and acquires all needed information to processes a whole block by only sending two RPC calls eth_getBlockByHash, get_logs. This proves to be more efficient and faster for quick direct transaction scanning.

Block Confirmations

Sometimes single codes are caught on side chains, uncles. these side chains have a minimal chance of carrying blocks with transactions that got discarded in the main ledger due to ethereum's consensus algorithm. In order to tackle this, a confirmations block option was added to specify the number of block confirmations before recording transactions in that block.

For example, if -b is set to 20 the smart contract watch will wait until block hight is at least 20.

Input

The smart contract watch can take parameters either as a

• Command line tool from terminal
• Environmental variables .env
• .watch.yml Config file

You can mix between any of modes together, take into account that input modes are ordered by priority. A CLI -q option for example will override the two other modes.

CLI

As a CLI tool you can run yarn run and then insert all needed parameters

Parameters:

-a or --addresses Address or array of addresses represented (Required) ex:

-a 0xf2Fbb2939981594e25d93e6226231FcC1b01718e, 0xfbb1b73c4f0bda4f67dca266ce6ef42f520fbb98

-f or --from Blocknumber Starting blocknumber Default:0.

-t or --to Blocknumber Ending blocknumber, If left blank the tool will continue scanning for new blocks endlessly Default: -.

-q or --quick Quick Mode: Activates quick mode mentioned above default: false.

-s or --save-state Save State mode: Saves the last successful scanned block in a file, Smart Contract Watch starts from this file block. In order to use this you must include a store directory ex, -s ./example-file-path or --save-state ./example-file-path.

-n or --node-url Path to node URL (Required) ex -n "http://localhost:8545"

-l or --log-level Specifies the log level indicated for reporting, you can choose one of three levels [Debug,Info,Error], Default:info

-o or --output-type Specifies output type, you can choose one of two options, [terminal, graylog]

-e or --access-token Etherscan access token, used to access etherscan for ABI importing.

-b or --block-confirmations The number of block confirmations needed before a block is checked.

ENV Variables

Environmental variables come second in priority, you can specify every parameter indicated as an ENV variable. Additionally you can mix between different settings if convenient for your application.In your .env you can specify parameters as

ADDRESSES

FROM_BLOCK

TO_BLOCK

QUICK_MODE True / False

SAVE_STATE

RPC_URL

LOG_LEVEL

OUTPUT_TYPE

BLOCK_CONFIRMATIONS

ACCESS_TOKEN

The inputs are very similar to when using CLI only QUICK_MODE is different in the sense that it can use true/false values

Config file

Smart Contract watch supports configuration files. You must insert all your configurations in a .watch.yml file. You can mix between both CLI and config file by filling only some of the needed fields, take into account that CLI and ENC override config file.

-addresses

-from

-to

-quick

-saveState

-nodeUrl

-logLevel

-outputType

-accessToken

-blockConfirmations

Smart Contract ABI

In order for the tool to successfully decode transactions. ABIs for the smart contracts must be provided this is done automatically by sending requests via Etherscan's Contracts api.

In case you want to add a smart contract that is in a private chain or not available on etherscan. you can add the ABI manually to the contracts directory ./smart contract watch/dist/contracts/ as a json file. the name of the json file must be exactly the same address as the smart contract.

ex:

./smart contract watch/dist/contracts/0xf2Fbb2939981594e25d93e6226231FcC1b01718e.json

The tool always checks the local ./contracts directory for smart contracts before it issues a request to etherscan.

Output

Smart-contract-watch reports two different activities conducted by a smart contract

• Direct transactions conducted from or to the monitored smart contracts. This is done by scanning the to, from fields in all transactions and reporting them back.

• Log events generated by the monitored smart contract. This is helpful when scanning for internal transactions/activity not directly conducted by the monitored smart-contract.

Additionally Smart Contract Watch currently supports two output modes:

• Terminal output: All marked transactions are sent directly to the terminal screen.

  [#address] function(param1,param2,...) log(event1,event2,......)

• Graylog output: All transaction are sent to Graylog after formatting the output into a JSON object. Communication with graylog is done through a Docker container.

How to use

• Clone git repository using git clone https://github.com/Neufund/smart-contract-watch
• run yarn to install dependencies
• run yarn start -f BLOCKNUMBER -t BLOCKNUMBER -a ARRAY_OF_ADDRESSES -n "http://examplepath" -l "DEBUG LEVEL"

example:

yarn start -f 4240705 -a 0x2c974b2d0ba1716e644c1fc59982a89ddd2ff724 -n "http://localhost:8545" -l "info" -q

Tests

yarn test