Set approveForAll from a contract on another contract

Question

I have two smart contracts (A, B), which are extended from ERC721 . Is it possible to create a function in B to call setApprovalForAll on A from a user Z ?

this is in contract B : testApprove(A) as user Z

    function testApprove(address _contract) public payable {
        bytes memory payload = abi.encodeWithSignature("setApprovalForAll(address,bool)", address(this), true);
        (bool success,) = address(_contract).delegatecall(payload);
        require(success);
        bool result = ERC721(_contract).isApprovedForAll(msg.sender, address(this));
        require(result, "Approve not set!");
    }

success is true, and there was no error because it ran OK. But when I check if contract B is approved, it's not!

Am I doing something wrong?

Thanks

Answer 1

bytes memory payload = abi.encodeWithSignature("setApprovalForAll(address,bool)", address(this), true);
(bool success,) = address(_contract).delegatecall(payload);

If this was invoked with regular .call , it would give approval from your contract (caller of the setApprovalForAll() function) to your contract (first param).

Since it's invoked with .delegatecall , the storage change is not performed on the target contract - but on your contract (the delegate caller). So all this snippet does, it sets a storage value of your contract in the same storage slot that the target would set the approval.

As per EIP-721 , setApprovalForAll() sets the approval from msg.sender . So the only way to receive the approval from the user is to have them send the transaction directly to the token contract - not through any other contract in between.