中继智能合约设计

Question

Im trying to make a relay smart contract which can pass msg.value and msg.sender in a function call from another deployed smart contract.

Context: The goal is to mint/borrow with multiples DeFi protocol (deployed and not owned by me contracts) with ONE main smart contract to have only ONE wallet to handle. That implies that funds ( msg.value ?) and owner ( msg.sender ?) are transfered within the functions calling transaction to the DeFi smart contracts.

EOA = A wallet with a bit of ETH to pay fees

Relay = The relay smart contract, which must receive funds from the DeFi smart contracts (= as being the msg.sender ?)

proxyDeFi = The proxy smart contract which allow to send multiple requests to one or multiple DeFi smart contracts within one transaction

It seems to me that delegatecall allows to pass the msg.sender and the msg.value in the execution of a function of another smart contract, so what I did so far:

The proxyDeFi is working as intended when called by the EOA, but proxyDeFi is the msg.sender for the queried DeFi smart contracts, not EOA. We will need several proxy contracts which could be updated often, so I tried to make a simple relay:

contract Relay {
    address public proxyDeFi;
    address owner = msg.sender;
    
    modifier isOwner() {
        require(msg.sender == owner, "Forbidden");
        _;
    }

    function update(address newAddress) isOwner public {
        proxyDeFi = newAddress;
    }

    fallback() isOwner external payable {
        proxyDeFi.delegatecall(msg.data);
    }
}

I tried to call proxyDeFi's functions to Relay (with EOA), but the transaction is systematically reverted on the deletegateCall . I tried to add a debug on the proxyDeFi side but nothing is output, I am new to Solidity so there is certainly something that I did not understand.

Roughly, I would like proxyDeFi to only be considered as if it was a library for the relay, except that proxyDeFi would be another smart contract deployed so that we can modify it without having to redeploy the Relay. I have the feeling that what I want to achieve is actually more complex than that, or maybe my method is not the correct/best one. I would greatly appreciate your advice.

Answer 1

When your calling contract to contract interactions the msg.sender is the calling contract, you could use tx.origin if you want it to get the address of person who initialized the transaction.

Careful, using delegate call, there are some exploit vulnerabilities if its improperly used, because it calls the function and updates the data stored on the calling contract.