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package evidence
import (
"fmt"
sm "github.com/tendermint/tendermint/state"
"github.com/tendermint/tendermint/types"
)
// VerifyEvidence verifies the evidence fully by checking:
// - it is sufficiently recent (MaxAge)
// - it is from a key who was a validator at the given height
// - it is internally consistent
// - it was properly signed by the alleged equivocator
func VerifyEvidence(evidence types.Evidence, state sm.State, stateDB StateStore, blockStore BlockStore) error {
var (
height = state.LastBlockHeight
evidenceParams = state.ConsensusParams.Evidence
ageDuration = state.LastBlockTime.Sub(evidence.Time())
ageNumBlocks = height - evidence.Height()
header *types.Header
)
// if the evidence is from the current height - this means the evidence is fresh from the consensus
// and we won't have it in the block store. We thus check that the time isn't before the previous block
if evidence.Height() == height+1 {
if evidence.Time().Before(state.LastBlockTime) {
return fmt.Errorf("evidence is from an earlier time than the previous block: %v < %v",
evidence.Time(),
state.LastBlockTime)
}
} else {
// try to retrieve header from blockstore
blockMeta := blockStore.LoadBlockMeta(evidence.Height())
header = &blockMeta.Header
if header == nil {
return fmt.Errorf("don't have header at height #%d", evidence.Height())
}
if header.Time != evidence.Time() {
return fmt.Errorf("evidence time (%v) is different to the time of the header we have for the same height (%v)",
evidence.Time(),
header.Time,
)
}
}
if ageDuration > evidenceParams.MaxAgeDuration && ageNumBlocks > evidenceParams.MaxAgeNumBlocks {
return fmt.Errorf(
"evidence from height %d (created at: %v) is too old; min height is %d and evidence can not be older than %v",
evidence.Height(),
evidence.Time(),
height-evidenceParams.MaxAgeNumBlocks,
state.LastBlockTime.Add(evidenceParams.MaxAgeDuration),
)
}
valset, err := stateDB.LoadValidators(evidence.Height())
if err != nil {
return err
}
addr := evidence.Address()
var val *types.Validator
// For all other types, expect evidence.Address to be a validator at height
// evidence.Height.
_, val = valset.GetByAddress(addr)
if val == nil {
return fmt.Errorf("address %X was not a validator at height %d", addr, evidence.Height())
}
if err := evidence.Verify(state.ChainID, val.PubKey); err != nil {
return err
}
return nil
}