Fee amount computation may overflow

[tomtau]

Crate

relayer

Summary of Bug

The fee amount is estimated using u64: https://github.com/informalsystems/ibc-rs/blob/9d1f86b9e7bdb06a3fb2c5b3ed05fc8004650784/relayer/src/chain/cosmos.rs#L2286

This may not be work in certain networks and it will result in transactions not being relayed due to an insufficient fee being paid.

Version

v0.8.0

Steps to Reproduce

1. network A: start up a Cosmos SDK-based network and configure its fee token to have many decimal places (e.g. 18) and configure a non-zero gas price
2. configure Hermes to create and relay on a channel to a network B (it can be anything)
3. start sending many IBC transfers of any coin from the network B to the network A

Acceptance Criteria

Large batches of transactions being relayed successfully on networks with fee tokens that have higher decimal places, such as networks working with Ethermint where a gas token has by default 18 decimal places.

---

For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate milestone (priority) applied
• Appropriate contributors tagged
• Contributor assigned/self-assigned