Remove SignatureType.Caller

[abandeali1]

Description

Testing instructions

Types of changes

Checklist:

• Prefix PR title with [WIP] if necessary.
• Prefix PR title with bracketed package name(s) corresponding to the changed package(s). For example: [sol-cov] Fixed bug.
• Add tests to cover changes as needed.
• Update documentation as needed.
• Add new entries to the relevant CHANGELOG.jsons.

[recmo]

How will this interact with executeTransaction? Seems like currently the exchange contract can become a valid signer for anything.

[recmo]

I think we need to add a require(msg.sender != this) here.

[recmo]

Not an issue since we are using DELEGATECALL and are not otherwise making arbitrary self-calls.

[thec00n]

Would this mean that if I call executeTransaction and then call preSign that I could presign orders for the Exchange contract?

I recommend to not allow adding pre signed signatures if signerAddress == msg.sender.

[abandeali1]

executeTransaction uses delegatecall, so the Exchange contract should never be msg.sender.

We've basically determined that usage of msg.sender here should be safe (this is a pretty common pattern). If we were using getCurrentContextAddress, there would definitely be extra protections.

[thec00n]

There is no direct vulnerability in the 0x protocol relating to this change. A scenario where an entity creates a smart contract that has a token balance and has approved the AssetProxies could still be vulnerable if they allow forward calls to the exchange contract and the function preSign is callable. It's acknowledged that this is outside of the control of 0x and for that reason the issue is considered closed.

I still recommend caution around the assumption that no signature validation needs to be performed when msg.sender == signerAddress.

[recmo]

Not an issue since we are using DELEGATECALL and are not otherwise making arbitrary self-calls.

[coveralls]

Coverage decreased (-0.006%) to 85.896% when pulling 0629a7d on feature/contracts/removeCallerSigType into 7351bf0 on development.