clearmatics/mobius

Add support for ERC-223 tokens

HarryR opened this issue · 2 comments

HarryR commented

It is possible to make the mixer support both ERC-223 and ERC-20 tokens as well as Ether in the Mixer contract. It's also possible to make it send Ether to smart contracts too, or send tokens then invoke a method on a smart contract.

In the ERC-223 and ERC-20 case the Mixer calls the transfer method of the token.

When the token address is 0 this is synonymous with Ether, if not zero the Mixer must validate the contract exists by calling extcodesize(addr).

ERC-223 tokens also support an optional arbitrary data field.

To make arbitrary smart contract calls the Withdraw caller must specify the msg.data field, contract address and Gas limit.

e.g. WithdrawToContract(ring_id, tx, ty, ctlist, address, gas, msg_data)

With this construct you make the Mixer call its self to Deposit again without needing a utility method for every conceivable thing the user may want to do, but it opens up a security hole for anything that relies on tx.origin rather than msg.sender

All of these parameters need to be included in the hash.

For now, I think it would be good to split the Mixer.Withdraw function into multiple variants to avoid convoluted code paths.

  • WithdrawERC20
  • WithdrawERC223
  • WithdrawEther

And maybe functions like:

  • WithdrawEtherTo (recipient address)
HarryR commented

Instead of the above approach the contract will use the tokenFallback interface from ERC-223.

The tag_x/tag_y point will be extracted from the bytes data parameter upon sending tokens to the contract.

The msg.sender will be the token address.

The denomination will be the value parameter.

AntoineRondelet commented

This issue tackled in the PR #57 which added support for ERC20 compatible tokens (ERC223 that are ERC20 compatible are thus supported).

I'll close it as I think this is done now. The withdrawal to contracts is not supported though, but this can be subject to another issue/PR if we need it in the future.