We currently have the domain separator to be the hash of the address of "Rollup.sol". It is possible the operator deploys rollup on other networks, so the new rollup has the same address and the same domain. Then a user's fund is at risk because the old txs and the old signatures can be replayed at the other networks.
At a minimum, we should add chainID to the domain.
There's a standard EIP712, in it defines what fields we should add in a domain. We currently have verifyingContract, but don't have the rest of the fields.
string name the user readable name of signing domain, i.e. the name of the DApp or the protocol.
string version the current major version of the signing domain. Signatures from different versions are not compatible.
uint256 chainId the EIP-155 chain id. The user-agent should refuse signing if it does not match the currently active chain.
address verifyingContract the address of the contract that will verify the signature. The user-agent may do contract specific phishing prevention.
bytes32 salt an disambiguating salt for the protocol. This can be used as a domain separator of last resort.
We thank @Marik-D for finding this issue
What's wrong
We currently have the domain separator to be the hash of the address of "Rollup.sol". It is possible the operator deploys rollup on other networks, so the new rollup has the same address and the same domain. Then a user's fund is at risk because the old txs and the old signatures can be replayed at the other networks.
https://github.com/thehubbleproject/hubble-contracts/blob/f23e37c2580ea1f40c08eafcecbba826ca041db3/contracts/rollup/Rollup.sol#L91
How can we fix it
List some possible solutions
verifyingContract, but don't have the rest of the fields.Here's an example of Uniswap's domain separator
https://github.com/Uniswap/uniswap-v2-periphery/blob/dda62473e2da448bc9cb8f4514dadda4aeede5f4/contracts/test/DeflatingERC20.sol#L23-L36
and its JS implementation
https://github.com/Uniswap/uniswap-v2-periphery/blob/dda62473e2da448bc9cb8f4514dadda4aeede5f4/test/shared/utilities.ts#L15-L28