The Swappery

Smart Contract Audit Report

Audit Summary

The Swappery Audit Report The Swappery is a new decentralized exchange.

For this audit, we reviewed the following contracts:

Audit Findings

Please ensure trust in the team prior to investing as they have some control in the ecosystem.
Date: March 21st, 2022.

Contracts Overview

SwapperyERC20 Contract:
  • This contract contains the core functionality of the Swappery LP token ($Swpr-LP) maintained by the SwapperyPair contract.
  • The contract supports ERC-712 signed messages which users can use to grant an allowances via a signed messaged, allowing for gasless approvals.
  • The contract complies with the ERC-20 standard.
SwapperyPair Contract:
  • This contract supports the core functionality of the Liquidity Pool token, which contains the logic behind LP minting, burning, and swapping between the assets in the liquidity pool.
  • Anyone can use the mint function to mint an amount of LP tokens proportional to the amount of tokens in the contract that are not accounted for in the reserves; all liquidity is automatically locked for 30 days starting from the initial liquidity add.
  • Once the 30 day waiting period has elapsed, anyone can use the burn function to burn any LP tokens in the contract and receive an amount of asset tokens proportional to the represented value of the LP tokens.
  • Anyone can use the swap function to transfer out an amount of the assets from the pool such that the new K value is at least as much as the current K value.
  • The swap function supports flash swaps which allows anyone to use a contract to borrow any amount of any asset, as long as the borrowed amount of each asset is returned within the call.
  • There is a 0.20% fee taken on all swaps; the fee remains in the liquidity pool and is proportionally allocated among all LP token holders.
  • In the event that the team's platform fee is enabled, 25% of the fee is minted as LP tokens to an address controlled by the team.
  • Anyone can use the skim function to transfer out any excess tokens that are not accounted for in the reserve amounts.
  • Alternatively, anyone can use the sync function to include any excess tokens in the reserve amounts so that they cannot be removed.
SwapperyFactory Contract:
  • This contract is used to deploy new SwapperyPair contracts specifying two underlying token assets.
  • Anyone can create any pair any any time, as long as the pair has not been created yet.
  • Only one SwapperyPair contract can exist for any combination of two token assets.
  • The "FeeTo Setter" address can set the "FeeTo" and the "FeeTo Setter" addresses to any address at any time.
SwapperyRouter Contract:
  • This contract is used to interact with any SwapperyPair liquidity pool contract created by the SwapperyFactory contract.
  • Upon adding liquidity, the user specifies the desiried minimum amount of each token in the pair to add to the liquidity pool; the user is minted SwapperyPair LP tokens representing their share of ownership of the liquidity pool.
  • Upon removing liquidity, the user specifies the desired minimum amount of each token asset to receive from the liquidity pool; the user's LP tokens are burnt in the process.
  • Liquidity removals support ERC-712 permits which allow the user to approve the Router to spend the user's LP tokens in a gasless manner.
  • Anyone can use this contract to swap one token asset for any other supported asset along a user-specified path of token assets.

Audit Results

Vulnerability CategoryNotesResult
Arbitrary Jump/Storage WriteN/APASS
Centralization of ControlN/APASS
Compiler IssuesN/APASS
Delegate Call to Untrusted ContractN/APASS
Dependence on Predictable VariablesN/APASS
Ether/Token TheftN/APASS
Flash LoansN/APASS
Front RunningN/APASS
Improper EventsN/APASS
Improper Authorization SchemeN/APASS
Integer Over/UnderflowN/APASS
Logical IssuesN/APASS
Oracle IssuesN/APASS
Outdated Compiler VersionN/APASS
Race ConditionsN/APASS
ReentrancyN/APASS
Signature IssuesN/APASS
Unbounded LoopsN/APASS
Unused CodeN/APASS
Overall Contract Safety PASS

SwapperyERC20, SwapperyPair, SwapperyFactory Contracts

Smart Contract Audit - Inheritance

Smart Contract Audit - Graph


 ($) = payable function
 # = non-constant function
 
 Int = Internal
 Ext = External
 Pub = Public
 
 + [Int] ISwapperyFactory 
    - [Ext] feeTo
    - [Ext] feeToSetter
    - [Ext] getPair
    - [Ext] allPairs
    - [Ext] allPairsLength
    - [Ext] createPair #
    - [Ext] setFeeTo #
    - [Ext] setFeeToSetter #

 + [Lib] TransferHelper 
    - [Int] safeApprove #
    - [Int] safeTransfer #
    - [Int] safeTransferFrom #
    - [Int] safeTransferETH #

 + [Int] ISwapperyRouter 
    - [Ext] factory
    - [Ext] WETH
    - [Ext] addLiquidity #
    - [Ext] addLiquidityETH ($)
    - [Ext] removeLiquidity #
    - [Ext] removeLiquidityETH #
    - [Ext] removeLiquidityWithPermit #
    - [Ext] removeLiquidityETHWithPermit #
    - [Ext] swapExactTokensForTokens #
    - [Ext] swapTokensForExactTokens #
    - [Ext] swapExactETHForTokens ($)
    - [Ext] swapTokensForExactETH #
    - [Ext] swapExactTokensForETH #
    - [Ext] swapETHForExactTokens ($)
    - [Ext] quote
    - [Ext] getAmountOut
    - [Ext] getAmountIn
    - [Ext] getAmountsOut
    - [Ext] getAmountsIn
    - [Ext] removeLiquidityETHSupportingFeeOnTransferTokens #
    - [Ext] removeLiquidityETHWithPermitSupportingFeeOnTransferTokens #
    - [Ext] swapExactTokensForTokensSupportingFeeOnTransferTokens #
    - [Ext] swapExactETHForTokensSupportingFeeOnTransferTokens ($)
    - [Ext] swapExactTokensForETHSupportingFeeOnTransferTokens #

 + [Int] ISwapperyPair 
    - [Ext] name
    - [Ext] symbol
    - [Ext] decimals
    - [Ext] totalSupply
    - [Ext] balanceOf
    - [Ext] allowance
    - [Ext] approve #
    - [Ext] transfer #
    - [Ext] transferFrom #
    - [Ext] DOMAIN_SEPARATOR
    - [Ext] PERMIT_TYPEHASH
    - [Ext] nonces
    - [Ext] permit #
    - [Ext] MINIMUM_LIQUIDITY
    - [Ext] factory
    - [Ext] token0
    - [Ext] token1
    - [Ext] getReserves
    - [Ext] price0CumulativeLast
    - [Ext] price1CumulativeLast
    - [Ext] kLast
    - [Ext] mint #
    - [Ext] burn #
    - [Ext] swap #
    - [Ext] skim #
    - [Ext] sync #
    - [Ext] initialize #
    - [Ext] setLockDays #
    - [Ext] AMM
    - [Ext] AMMM
    - [Ext] ALT

 + [Lib] SafeMath 
    - [Int] add
    - [Int] sub
    - [Int] mul

 + [Lib] SwapperyLibrary 
    - [Int] sortTokens
    - [Int] pairFor
    - [Int] getReserves
    - [Int] quote
    - [Int] getAmountOut
    - [Int] getAmountIn
    - [Int] getAmountsOut
    - [Int] getAmountsIn

 + [Int] IERC20 
    - [Ext] name
    - [Ext] symbol
    - [Ext] decimals
    - [Ext] totalSupply
    - [Ext] balanceOf
    - [Ext] allowance
    - [Ext] approve #
    - [Ext] transfer #
    - [Ext] transferFrom #

 + [Int] IWETH 
    - [Ext] deposit ($)
    - [Ext] transfer #
    - [Ext] withdraw #

 +  SwapperyRouter (ISwapperyRouter)
    - [Pub]  #
    - [Ext]  ($)
    - [Int] _addLiquidity #
    - [Ext] addLiquidity #
       - modifiers: ensure
    - [Ext] addLiquidityETH ($)
       - modifiers: ensure
    - [Pub] removeLiquidity #
       - modifiers: ensure
    - [Pub] removeLiquidityETH #
       - modifiers: ensure
    - [Ext] removeLiquidityWithPermit #
    - [Ext] removeLiquidityETHWithPermit #
    - [Pub] removeLiquidityETHSupportingFeeOnTransferTokens #
       - modifiers: ensure
    - [Ext] removeLiquidityETHWithPermitSupportingFeeOnTransferTokens #
    - [Int] _swap #
    - [Ext] swapExactTokensForTokens #
       - modifiers: ensure
    - [Ext] swapTokensForExactTokens #
       - modifiers: ensure
    - [Ext] swapExactETHForTokens ($)
       - modifiers: ensure
    - [Ext] swapTokensForExactETH #
       - modifiers: ensure
    - [Ext] swapExactTokensForETH #
       - modifiers: ensure
    - [Ext] swapETHForExactTokens ($)
       - modifiers: ensure
    - [Int] _swapSupportingFeeOnTransferTokens #
    - [Ext] swapExactTokensForTokensSupportingFeeOnTransferTokens #
       - modifiers: ensure
    - [Ext] swapExactETHForTokensSupportingFeeOnTransferTokens ($)
       - modifiers: ensure
    - [Ext] swapExactTokensForETHSupportingFeeOnTransferTokens #
       - modifiers: ensure
    - [Pub] quote
    - [Pub] getAmountOut
    - [Pub] getAmountIn
    - [Pub] getAmountsOut
    - [Pub] getAmountsIn
    - [Ext] setLockDays #

SwapperyRouter Contract

Smart Contract Audit - Inheritance

Smart Contract Audit - Graph


 ($) = payable function
 # = non-constant function
 
 Int = Internal
 Ext = External
 Pub = Public
 
 + [Lib] TransferHelper 
    - [Int] safeApprove #
    - [Int] safeTransfer #
    - [Int] safeTransferFrom #
    - [Int] safeTransferETH #

 + [Int] IXdaoRouter01 
    - [Ext] factory
    - [Ext] WETH
    - [Ext] addLiquidity #
    - [Ext] addLiquidityETH ($)
    - [Ext] removeLiquidity #
    - [Ext] removeLiquidityETH #
    - [Ext] removeLiquidityWithPermit #
    - [Ext] removeLiquidityETHWithPermit #
    - [Ext] swapExactTokensForTokens #
    - [Ext] swapTokensForExactTokens #
    - [Ext] swapExactETHForTokens ($)
    - [Ext] swapTokensForExactETH #
    - [Ext] swapExactTokensForETH #
    - [Ext] swapETHForExactTokens ($)
    - [Ext] quote
    - [Ext] getAmountOut
    - [Ext] getAmountIn
    - [Ext] getAmountsOut
    - [Ext] getAmountsIn

 + [Int] IXdaoRouter02 (IXdaoRouter01)
    - [Ext] removeLiquidityETHSupportingFeeOnTransferTokens #
    - [Ext] removeLiquidityETHWithPermitSupportingFeeOnTransferTokens #
    - [Ext] swapExactTokensForTokensSupportingFeeOnTransferTokens #
    - [Ext] swapExactETHForTokensSupportingFeeOnTransferTokens ($)
    - [Ext] swapExactTokensForETHSupportingFeeOnTransferTokens #

 + [Int] IXdaoFactory 
    - [Ext] feeTo
    - [Ext] feeToSetter
    - [Ext] getPair
    - [Ext] allPairs
    - [Ext] allPairsLength
    - [Ext] createPair #
    - [Ext] setFeeTo #
    - [Ext] setFeeToSetter #
    - [Ext] INIT_CODE_PAIR_HASH

 + [Lib] SafeMath 
    - [Int] add
    - [Int] sub
    - [Int] mul

 + [Int] ISwapperyPair 
    - [Ext] name
    - [Ext] symbol
    - [Ext] decimals
    - [Ext] totalSupply
    - [Ext] balanceOf
    - [Ext] allowance
    - [Ext] approve #
    - [Ext] transfer #
    - [Ext] transferFrom #
    - [Ext] DOMAIN_SEPARATOR
    - [Ext] PERMIT_TYPEHASH
    - [Ext] nonces
    - [Ext] permit #
    - [Ext] MINIMUM_LIQUIDITY
    - [Ext] factory
    - [Ext] token0
    - [Ext] token1
    - [Ext] getReserves
    - [Ext] price0CumulativeLast
    - [Ext] price1CumulativeLast
    - [Ext] kLast
    - [Ext] mint #
    - [Ext] burn #
    - [Ext] swap #
    - [Ext] skim #
    - [Ext] sync #
    - [Ext] initialize #

 + [Lib] XdaoLibrary 
    - [Int] sortTokens
    - [Int] pairFor
    - [Int] getReserves
    - [Int] quote
    - [Int] getAmountOut
    - [Int] getAmountIn
    - [Int] getAmountsOut
    - [Int] getAmountsIn

 + [Int] IERC20 
    - [Ext] name
    - [Ext] symbol
    - [Ext] decimals
    - [Ext] totalSupply
    - [Ext] balanceOf
    - [Ext] allowance
    - [Ext] approve #
    - [Ext] transfer #
    - [Ext] transferFrom #

 + [Int] IWETH 
    - [Ext] deposit ($)
    - [Ext] transfer #
    - [Ext] withdraw #

 +  XdaoRouter (IXdaoRouter02)
    - [Pub]  #
    - [Ext]  ($)
    - [Int] _addLiquidity #
    - [Ext] addLiquidity #
       - modifiers: ensure
    - [Ext] addLiquidityETH ($)
       - modifiers: ensure
    - [Pub] removeLiquidity #
       - modifiers: ensure
    - [Pub] removeLiquidityETH #
       - modifiers: ensure
    - [Ext] removeLiquidityWithPermit #
    - [Ext] removeLiquidityETHWithPermit #
    - [Pub] removeLiquidityETHSupportingFeeOnTransferTokens #
       - modifiers: ensure
    - [Ext] removeLiquidityETHWithPermitSupportingFeeOnTransferTokens #
    - [Int] _swap #
    - [Ext] swapExactTokensForTokens #
       - modifiers: ensure
    - [Ext] swapTokensForExactTokens #
       - modifiers: ensure
    - [Ext] swapExactETHForTokens ($)
       - modifiers: ensure
    - [Ext] swapTokensForExactETH #
       - modifiers: ensure
    - [Ext] swapExactTokensForETH #
       - modifiers: ensure
    - [Ext] swapETHForExactTokens ($)
       - modifiers: ensure
    - [Int] _swapSupportingFeeOnTransferTokens #
    - [Ext] swapExactTokensForTokensSupportingFeeOnTransferTokens #
       - modifiers: ensure
    - [Ext] swapExactETHForTokensSupportingFeeOnTransferTokens ($)
       - modifiers: ensure
    - [Ext] swapExactTokensForETHSupportingFeeOnTransferTokens #
       - modifiers: ensure
    - [Pub] quote
    - [Pub] getAmountOut
    - [Pub] getAmountIn
    - [Pub] getAmountsOut
    - [Pub] getAmountsIn


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What is a Solidity Audit?

Typically, a smart contract audit is a comprehensive review process designed to discover logical errors, security vulnerabilities, and optimization opportunities within code. A Solidity Audit takes this a step further by verifying economic logic to ensure the stability of smart contracts and highlighting privileged functionality to create a report that is easy to understand for developers and community members alike.

How Do I Interpret the Findings?

Each of our Findings will be labeled with a Severity level. We always recommend the team resolve High, Medium, and Low severity findings prior to deploying the code to the mainnet. Here is a breakdown on what each Severity level means for the project:

  • High severity indicates that the issue puts a large number of users' funds at risk and has a high probability of exploitation, or the smart contract contains serious logical issues which can prevent the code from operating as intended.
  • Medium severity issues are those which place at least some users' funds at risk and has a medium to high probability of exploitation.
  • Low severity issues have a relatively minor risk association; these issues have a low probability of occurring or may have a minimal impact.
  • Informational issues pose no immediate risk, but inform the project team of opportunities for gas optimizations and following smart contract security best practices.