Ethereum smart contract scanner and analysis

This is the tool developed as a part of my master thesis Hunting Vulnerabilities in Groth16 zk-SNARK implemented by Ethereum Smart Contracts.

This tool includes:

• A scanner to download smart contracts from Etherum history blocks.
• A tool to detect whether a Groth16 contract is susceptible to Missing constraint on public inputs vulnerability.

Block scanner

The block scanner scan all visible contracts from given Ethereum blocks. To include all visiable and invisible contracts, we recommend using https://github.com/paradigmxyz/cryo .

Installation

• Install Dependence

pip install os time pandas argparse web3

• Config RPC Endpoints

Copy the url of you own RPC endpoint to scanner/get_contracts.py

END_POINTS = {
"Merkle":"https://eth.merkle.io",
"Your Endpoint Name": "Your URL"
}

Example Usage

For example, if you want to download smart contracts from block 18,000,000 to 18,000,123, you can use the following command:

cd scanner
python get_contracts.py --startId 18000000 --endId 18000123 --endpoint <your endpoint name>

The downloaded contracts will be listed in a .csv file, where the format is [block_id, contract_address, bytecode]

---

Vulnerability Analyser

This tool inspect the bytecode of a given Groth16 smart contract to see if there exist the vulnerability of missing constraint check on public inputs, specifically:

• public variables, like nullifier hash should be constrained to be smaller than SNARK scalar field.
• Groth16 proofs (A,B,C) should be constrained to be smaller than prime Q.

Installation

This tool has dependence on Heimdall, you need to install Heimdall first. https://github.com/linuxserver/Heimdall

Then install the following python libraries:

pip install pandas argparse os pyevmasm time

Example Usage

cd analysis
python main.py --bytecode <bytecode of the target smart contract>

terminal output

The contract is a Groth16 implementation.
analyzing the contract...
The report is saved to output/report.txt

in output/report.txt

======Report on this smart contract======
-Vulnerability Prediction:
|----Has SNARK scalar field constraint?: False
|----Has Prime Q constraint?: True
|
|
-Prototype Analysis:
|----Contract fingerprint: QBAQQC
|----Prototype name: snarkjs
|----Prototype info: The prototype may be vulnerable due to incorrect [public_input < snark_scalar_field] check and missing [proof < prime_Q] check. For more information, please refer to https://github.com/iden3/snarkjs/pull/480
|----Prototype address: 0xEB2952A4098e15C97E1Ce126FE479f27E2FFB40c
|
Execution completed.
=========================================