How to generate a signature in foundry if Private key is a string?

Question

I have been testing some contract that includes EIP712 signatures, with foundry.

As per this doc we need to pass the private key which is being accepted as a uint256.

(uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPrivateKey, digest);

And it is working fine as long as I am passing a uint256 and creating an address from the same uint using vm.addr.

The problem kicks in when I have created the address from a string using makeAddr() function, as shown in the pic below.

createActor Function:

   function createActor(string memory name) internal returns (address payable) {
        address payable actor = payable(makeAddr(name));
        // Transfer 50 eth to every actor
        vm.deal({ account: actor, newBalance: 50 ether });
        // Transfer 50K PUSH Tokens for every actor
        vm.prank(tokenDistributor);
        pushToken.transfer(actor, 50_000 ether);
        return actor;
    }

What is the work around for this? What should I pass as the private key in the vm.sign function for the addresses that have been created using makeAddr?

Do let me know if the question was clear or if I need to add more details.

Answer 1

You can get a private key when you create an address. Use the following command instead of makeAddr(name): makeAddrAndKey(name)

Like this:

(address alice, uint256 key) = makeAddrAndKey("alice_channel_owner");
bytes32 digest = keccak256("hello");
(uint8 v, bytes32 r, bytes32 s) = vm.sign(key, digest);

console2.log("actor:", actor); // 0xFF56C91F1242236a49755655EF63CE6eba9B1FB0
console2.log("key:", key);  // 63033525494174347069753265686890270152002273482463513079811354675539312780180
console2.log("v:", v);  // v: 28
console2.logBytes32(r);  // 0xd79fe615dc4d78ab9359ed0720d9aecce919d4a408856888a295951082563cf9
console2.logBytes32(s);  // 0x5f505f2b24ae507082151b184595b977b03199e7ab4d6e69737306e36488ac9a