Semgrep rules for smart contracts

In this repository you can find semgrep rules that look for patterns of vulnerabilities in smart contracts based on actual DeFi exploits as well as gas optimization rules that can be used as a part of the CI pipeline.

Disclaimer

Currently semgrep supports Solidity in experimental mode. Some of the rules may not work until Solidity is in beta at least.

Scanning

semgrep + smart-contract-sanctuary = ❤️

$ semgrep --config solidity/security ~/smart-contract-sanctuary-arbitrum/contracts/mainnet

Testing

Each rule is accompanied by an actual vulnerable source code that was targeted by an exploit. Vulnerable lines are marked with // ruleid: ...

In case a rule is not yet supported by semgrep, you will find // todoruleid: ...

Run tests:

$ semgrep --test solidity

Validate rules:

$ semgrep --validate --config solidity

Using in Github Actions

Create run-semgrep.yaml in .github/workflows with the following contents:

# Name of this GitHub Actions workflow.
name: Run Semgrep

on:
  # Scan changed files in PRs (diff-aware scanning):
  pull_request: {}
  # On-demand 
  workflow_dispatch: {}

jobs:
  semgrep:
    # User-definable name of this GitHub Actions job:
    name: Scan
    # If you are self-hosting, change the following `runs-on` value: 
    runs-on: ubuntu-latest

    container:
      # A Docker image with Semgrep installed. Do not change this.
      image: returntocorp/semgrep

    # Skip any PR created by dependabot to avoid permission issues:
    if: (github.actor != 'dependabot[bot]')

    steps:
      # Fetch project source with GitHub Actions Checkout.
      - uses: actions/checkout@v3
      # Fetch semgrep rules
      - name: Fetch semgrep rules
        uses: actions/checkout@v3
        with:
          repository: decurity/semgrep-smart-contracts
          path: rules
      # Run security and gas optimization rules
      - run: semgrep ci --sarif --output=semgrep.sarif || true
        env:
           SEMGREP_RULES: rules/solidity/security rules/solidity/performance
      # Upload findings to GitHub Advanced Security Dashboard
      - name: Upload findings to GitHub Advanced Security Dashboard
        uses: github/codeql-action/upload-sarif@v2
        with:
          sarif_file: semgrep.sarif
        if: always()

Security Rules

Rule ID	Targets	Description
compound-borrowfresh-reentrancy	Compound, Ola Finance, Hundred Finance, Agave	Function borrowFresh() in Compound performs state update after doTransferOut()
compound-sweeptoken-not-restricted	TUSD, Compound	Function sweepToken is allowed to be called by anyone
erc20-public-transfer	Creat Future	Custom ERC20 implementation exposes _transfer() as public
erc20-public-burn	HospoWise	Anyone can burn tokens of other accounts
erc677-reentrancy	Ola Finance	ERC677 callAfterTransfer() reentrancy
erc777-reentrancy	Bacon Protocol	ERC777 tokensReceived() reentrancy
erc721-reentrancy	Hype Bears	ERC721 onERC721Received() reentrancy
erc721-arbitrary-transferfrom	Distortion Genesis	Custom ERC721 implementation lacks access control checks in _transfer()
gearbox-tokens-path-confusion	Gearbox	UniswapV3 adapter implemented incorrect extraction of path parameters
keeper-network-oracle-manipulation	Inverse Finance	Keep3rV2.current() call has high data freshness, but it has low security, an exploiter simply needs to manipulate 2 data points to be able to impact the feed.
basic-oracle-manipulation	Onering Finance, Deus Finance	getSharePrice() can be manipulated via flashloan
redacted-cartel-custom-approval-bug	Redacted Cartel	transferFrom() can steal allowance of other accounts
rigoblock-missing-access-control	RigoBlock	setMultipleAllowances() is missing onlyOwner modifier
oracle-price-update-not-restricted	Rikkei Finance, Aave	Oracle price data can be submitted by anyone
superfluid-ctx-injection	Superfluid	A specially crafted calldata may be used to impersonate other accounts
tecra-coin-burnfrom-bug	Tecra Coin	Parameter "from" is checked at incorrect position in "_allowances" mapping
arbitrary-low-level-call	Auctus Options, Starstream Finance, BasketDAO, Li Finance	An attacker may perform call() to an arbitrary address with controlled calldata
sense-missing-oracle-access-control	Sense Finance	Oracle update is not restricted in onSwap(), rule by Arbaz Kiraak
proxy-storage-collision	Audius	Proxy declares a state var that may override a storage slot of the implementation
uniswap-callback-not-protected	Generic	Uniswap callback is not protected
encode-packed-collision	Generic	Hash collision with variable length arguments in abi.encodePacked
openzeppelin-ecdsa-recover-malleable	OpenZeppelin	Potential signature malleability
BETA: basic-arithmetic-underflow	Umbrella Network, Remittance Token	Possible arithmetic underflow
unrestricted-transferownership	Ragnarok Online Invasion	Contract ownership can be transfered by anyone
msg-value-multicall	Sushiswap	Function with constant msg.value can be called multiple times
no-bidi-characters	Generic	The code must not contain any of Unicode Direction Control Characters
delegatecall-to-arbitrary-address	Generic	An attacker may perform delegatecall() to an arbitrary address.
incorrect-use-of-blockhash	Generic	blockhash(block.number) and blockhash(block.number + N) always returns 0.
accessible-selfdestruct	Generic	Contract can be destructed by anyone in $FUNC
no-slippage-check	Generic	No slippage check in a Uniswap v2/v3 trade
balancer-readonly-reentrancy-getrate	Balancer	getRate() call on a Balancer pool is not protected from the read-only reentrancy.
balancer-readonly-reentrancy-getpooltokens	Balancer	getPoolTokens() call on a Balancer pool is not protected from the read-only reentrancy.
curve-readonly-reentrancy	Curve	get_virtual_price() call on a Curve pool is not protected from the read-only reentrancy.

Gas Optimization Rules

Rule ID	Description
array-length-outside-loop	Caching the array length outside a loop saves reading it on each iteration, as long as the array's length is not changed during the loop.
init-variables-with-default-value	Explicitly initializing a variable with its default value costs unnecessary gas.
state-variable-read-in-a-loop	Replace state variable reads and writes within loops with local variable reads and writes.
unnecessary-checked-arithmetic-in-loop	A lot of times there is no risk that the loop counter can overflow. Using Solidity's unchecked block saves the overflow checks.
use-custom-error-not-require	Consider using custom errors as they are more gas efficient while allowing developers to describe the error in detail using NatSpec.
use-multiple-require	Using multiple require statements is cheaper than using && multiple check combinations.
use-nested-if	Using nested is cheaper than using && multiple check combinations.
use-prefix-decrement-not-postfix	The prefix decrement expression is cheaper in terms of gas.
use-prefix-increment-not-postfix	The prefix increment expression is cheaper in terms of gas.
use-short-revert-string	Shortening revert strings to fit in 32 bytes will decrease gas costs for deployment and gas costs when the revert condition has been met.
non-payable-constructor	Consider making costructor payable to save gas.
non-optimal-variables-swap	Consider swapping variables using ($VAR1, $VAR2) = ($VAR2, $VAR1) to save gas.
inefficient-state-variable-increment	+= costs more gas than = + for state variables.

Best Practices Rules

Rule ID	Description
use-abi-encodecall-instead-of-encodewithselector	To guarantee arguments type safety it is recommended to use abi.encodeCall instead of abi.encodeWithSelector.
use-ownable2step	By demanding that the receiver of the owner permissions actively accept via a contract call of its own, Ownable2Step and Ownable2StepUpgradeable prevent the contract ownership from accidentally being transferred to an address that cannot handle it.