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feat: update the FOT detector to check for external fees (#24)
* Add support for checking if token has external fees * use factoryV2 as sentinel test address * Add mock fot token and test cases * flat fee for external fees token and fix tests * detect external transfer failure * Rename to feeTakenOnTransfer and add mock token test * forge fmt * comment * remove debug logs * foundry.toml fix * fix foundry toml * remove rpc in foundry toml * comments * nit readability * forge fmt * custom error and comment * func name * comments - readability * var names * bubble up reason in unknown transfer error case * nit readability --------- Co-authored-by: ConjunctiveNormalForm <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,39 @@ | ||
| // SPDX-License-Identifier: GPL-2.0-or-later | ||
| pragma solidity =0.8.19; | ||
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| import {ERC20} from "solmate/tokens/ERC20.sol"; | ||
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| contract MockFotTokenWithExternalFees is ERC20 { | ||
| uint256 public taxBps; | ||
| address public pair; | ||
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| constructor(uint256 _taxBps) ERC20("MockFotToken", "MFOT", 18) { | ||
| taxBps = _taxBps; | ||
| } | ||
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| function setPair(address _pair) external { | ||
| pair = _pair; | ||
| } | ||
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| function mint(address to, uint256 amount) external { | ||
| _mint(to, amount); | ||
| } | ||
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| // this token takes fees on ALL transfers, treating transfers to other addresses as sells | ||
| function transfer(address to, uint256 amount) public override returns (bool) { | ||
| balanceOf[msg.sender] -= amount; | ||
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| // Cannot overflow because the sum of all user | ||
| // balances can't exceed the max uint256 value. | ||
| uint256 feeAmount; | ||
| unchecked { | ||
| feeAmount = amount * taxBps / 10000; | ||
| balanceOf[to] += amount - feeAmount; | ||
| balanceOf[address(this)] += feeAmount; | ||
| } | ||
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| emit Transfer(msg.sender, to, amount - feeAmount); | ||
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| return true; | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,47 @@ | ||
| // SPDX-License-Identifier: GPL-2.0-or-later | ||
| pragma solidity =0.8.19; | ||
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| import {ERC20} from "solmate/tokens/ERC20.sol"; | ||
| import "v2-core/interfaces/IUniswapV2Pair.sol"; | ||
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| contract MockReentrancyFotToken is ERC20 { | ||
| uint256 public taxBps; | ||
| address public pair; | ||
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| constructor(uint256 _taxBps) ERC20("MockReentrancyFotToken", "MFOT", 18) { | ||
| taxBps = _taxBps; | ||
| } | ||
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| function setPair(address _pair) external { | ||
| pair = _pair; | ||
| } | ||
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| function mint(address to, uint256 amount) external { | ||
| _mint(to, amount); | ||
| } | ||
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| // this token takes a fee on all transfers, and swaps the fee on the V2 pair for external transfers (not buy/sells) | ||
| function transfer(address to, uint256 amount) public override returns (bool) { | ||
| balanceOf[msg.sender] -= amount; | ||
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| // Cannot overflow because the sum of all user | ||
| // balances can't exceed the max uint256 value. | ||
| uint256 feeAmount; | ||
| unchecked { | ||
| feeAmount = amount * taxBps / 10000; | ||
| balanceOf[to] += amount - feeAmount; | ||
| balanceOf[address(this)] += feeAmount; | ||
| } | ||
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| // Only add in extra swap if is not buy/sell on the pair | ||
| if (to != pair && msg.sender != pair) { | ||
| IUniswapV2Pair(pair).token0() == address(this) | ||
| ? IUniswapV2Pair(pair).swap(0, feeAmount, address(this), new bytes(0)) | ||
| : IUniswapV2Pair(pair).swap(feeAmount, 0, address(this), new bytes(0)); | ||
| } | ||
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| emit Transfer(msg.sender, to, amount - feeAmount); | ||
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| return true; | ||
| } | ||
| } |