Transaction Ethereum Restore: Uniswap Router 0x02 SwapexactethFortken
As a developer of Ethereum, you are probably not foreign to the complexities of the interaction with decentralized exchanges and intelligent contracts. Recently, I encountered a frustrating problem with the Uniswap router (0x02) while I was trying to exchange ETH with an ERC20 token using the `swapexactethingen '.
The problem: the transaction restores
To understand what is going on, we break down the scenario:
- The user pre-apps an withdrawal allowance on the Uniswap router (0x02) to spend ETH on their behalf.
2
- The transaction is sent to the Ethereum network.
However, every time this transaction occurs, it is restored by the Ethereum virtual machine (EVM). This problem arises due to a common problem known as "return" or "return of callbacks".
The problem of the Uniswap router
In the case of the Uniswap router (0x02), theswapexactethroken” function “is vulnerable to the return attacks. When the contract calls this function, it triggers a callback in the Uniswap router, which can lead to an infinite cycle of calls and finally involve the restoration of the transaction.
The correction: discard the transaction
To solve the problem, I wrapped the `swapexactethforrtks calls using the unwrap 'function provided by the Uniswap library. This allows us to avoid triggering the callback and prevent the return attack.
Here is an example of how you can use theunwrap ‘function:
Solidity `
Pragma solidity ^0.8.0;
import “
Myswap contract {
Swaprouter02 Uniswaprouter public;
CONSTRUTOR () {
Uniswaputer = New Swaprouter02 ();
}
Swapexactthforrtken (Uint256 _amountin, Uint256 [] memory _Tokena, address _to) public function {
// call the waste function to avoid returning
uniswaprouter.unwrap (_amountin, _towena, _to);
}
}
`
By wrapping theswapexactethfortk” call “with theunwrap 'function, we assure that the callback is not activated and that the transaction is performed correctly.
Conclusion
While the problem of return attacks can be frustrating for the meeting, it is essential to understand what is happening and take measures to solve it. In this case, wrap theswapexactethforrtk "call using the unwrapfunction provides a solution to prevent re -entry attacks on the Uniswap router (0x02).
As developers, we should always be aware of these problems and take the necessary precautions to ensure the safety and integrity of our intelligent contracts.
Additional tips
- Always wrap the transaction calls that activate callbacks or return using theUNRAP ‘function.
- Reviews the implementation of your intelligent contract for potential vulnerability to return attacks.
- Take into consideration the implementation of further guarantees, such as retirement mechanisms or safe withdrawal allowances, to mitigate other types of problems.