ASA-2024-004: Default configuration param for Evidence may limit window of validity

Component: CometBFT Criticality: Low Affected versions: All Affected users: Validators, Chain Builders + Maintainers

Summary

A default configuration in CometBFT has been found to be small for common use cases, and may prevent the slashing mechanism from working in specific cases. The default values for EvidenceParams.MaxAgeNumBlocks and EvidenceParams.MaxAgeDuration consensus parameters may not be sufficient for common use cases to provide coverage for the entire unbonding period for a chain (Staking.UnbondingTime). If the conditions of both of these parameters are exceeded, evidence may be prematurely expired and considered no longer valid, potentially allowing for unpunished Byzantine behavior if evidence is discovered outside of that window.

Next Steps for Chains and Validators

It is recommended that chain ecosystems and their maintainers set the consensus parameters EvidenceParams.MaxAgeNumBlocks and EvidenceParams.MaxAgeDuration to values appropriate for their use case:

• EvidenceParams.MaxAgeDuration (set in nanoseconds) should exceed the duration of the chain’s unbonding period
• EvidenceParams.MaxAgeNumBlocks should exceed the number of estimated blocks that will be produced by your chain throughout the unbonding period

For more information about evidence in CometBFT, please see: https://docs.cometbft.com/v0.37/spec/consensus/evidence.

For more information about the cosmos-sdk x/staking and x/slashing modules, and UnbondingTime parameter, please see: https://docs.cosmos.network/v0.50/build/modules/staking and https://docs.cosmos.network/v0.50/build/modules/slashing.

CometBFT is designed to be configurable by chains, and implements many different configuration variables and parameters to allow chain developers, validators, node operators, and chain participants to customize it best to their use case.