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Add exchange remark #120

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b395a14
add remark
paszkowskiDamian Apr 21, 2022
1cf9df4
fix typo
paszkowskiDamian Apr 21, 2022
485a748
fix typo
paszkowskiDamian Apr 25, 2022
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4 changes: 4 additions & 0 deletions README.md
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Expand Up @@ -34,3 +34,7 @@ block number the fork starts from. If it starts from an old state some tests mig
`npm run test [network] [test-file]` - run a test to the specified network by calling the script from the `/test` folder

`npm run verify [network] [contract-name]` - verify contract based on address and arguments from `/deployments` folder

## Remarks

- `Exchange.sol` in the `_swap` function we are calling low level function `call` with arbitrary address and call data, which may impose some security threats, however by design the `Exchange` contract does not hold any founds and is used only as proxy to Exchange (1inch) and collecting fees. Thus calling `call` in our case is safe and does not expose us or our users to theft of funds.
2 changes: 2 additions & 0 deletions contracts/multiply/Exchange.sol
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Expand Up @@ -85,6 +85,8 @@ contract Exchange {
bytes calldata withData
) internal returns (uint256) {
IERC20(fromAsset).safeApprove(callee, amount);
// In general we shouldn't call arbitrary address with arbitrary data. This would be a security risk,
// However in this case by design the Exchange contract does not hold any funds, so there is nothing to be stolen.
(bool success, ) = callee.call(withData);
require(success, "Exchange / Could not swap");
uint256 balance = IERC20(toAsset).balanceOf(address(this));
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