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slash.go
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slash.go
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package keeper
import (
"fmt"
sdk "github.com/cosmos/cosmos-sdk/types"
types "github.com/cosmos/cosmos-sdk/x/stake/types"
"github.com/tendermint/tendermint/crypto"
)
// Slash a validator for an infraction committed at a known height
// Find the contributing stake at that height and burn the specified slashFactor
// of it, updating unbonding delegation & redelegations appropriately
//
// CONTRACT:
// slashFactor is non-negative
// CONTRACT:
// Infraction committed equal to or less than an unbonding period in the past,
// so all unbonding delegations and redelegations from that height are stored
// CONTRACT:
// Infraction committed at the current height or at a past height,
// not at a height in the future
func (k Keeper) Slash(ctx sdk.Context, pubkey crypto.PubKey, infractionHeight int64, power int64, slashFactor sdk.Rat) {
logger := ctx.Logger().With("module", "x/stake")
if slashFactor.LT(sdk.ZeroRat()) {
panic(fmt.Errorf("attempted to slash with a negative slashFactor: %v", slashFactor))
}
// Amount of slashing = slash slashFactor * power at time of infraction
slashAmount := sdk.NewRat(power).Mul(slashFactor)
// ref https://github.com/cosmos/cosmos-sdk/issues/1348
// ref https://github.com/cosmos/cosmos-sdk/issues/1471
validator, found := k.GetValidatorByPubKey(ctx, pubkey)
if !found {
// If not found, the validator must have been overslashed and removed - so we don't need to do anything
// NOTE: Correctness dependent on invariant that unbonding delegations / redelegations must also have been completely
// slashed in this case - which we don't explicitly check, but should be true.
// Log the slash attempt for future reference (maybe we should tag it too)
logger.Error(fmt.Sprintf(
"WARNING: Ignored attempt to slash a nonexistent validator with address %s, we recommend you investigate immediately",
pubkey.Address()))
return
}
ownerAddress := validator.GetOwner()
// Track remaining slash amount for the validator
// This will decrease when we slash unbondings and
// redelegations, as that stake has since unbonded
remainingSlashAmount := slashAmount
switch {
case infractionHeight > ctx.BlockHeight():
// Can't slash infractions in the future
panic(fmt.Sprintf(
"impossible attempt to slash future infraction at height %d but we are at height %d",
infractionHeight, ctx.BlockHeight()))
case infractionHeight == ctx.BlockHeight():
// Special-case slash at current height for efficiency - we don't need to look through unbonding delegations or redelegations
logger.Info(fmt.Sprintf(
"Slashing at current height %d, not scanning unbonding delegations & redelegations",
infractionHeight))
case infractionHeight < ctx.BlockHeight():
// Iterate through unbonding delegations from slashed validator
unbondingDelegations := k.GetUnbondingDelegationsFromValidator(ctx, ownerAddress)
for _, unbondingDelegation := range unbondingDelegations {
amountSlashed := k.slashUnbondingDelegation(ctx, unbondingDelegation, infractionHeight, slashFactor)
if amountSlashed.IsZero() {
continue
}
remainingSlashAmount = remainingSlashAmount.Sub(amountSlashed)
}
// Iterate through redelegations from slashed validator
redelegations := k.GetRedelegationsFromValidator(ctx, ownerAddress)
for _, redelegation := range redelegations {
amountSlashed := k.slashRedelegation(ctx, validator, redelegation, infractionHeight, slashFactor)
if amountSlashed.IsZero() {
continue
}
remainingSlashAmount = remainingSlashAmount.Sub(amountSlashed)
}
}
// Cannot decrease balance below zero
tokensToBurn := sdk.MinRat(remainingSlashAmount, validator.Tokens)
// Get the current pool
pool := k.GetPool(ctx)
// remove tokens from the validator
validator, pool = validator.RemoveTokens(pool, tokensToBurn)
// burn tokens
pool.LooseTokens = pool.LooseTokens.Sub(tokensToBurn)
// update the pool
k.SetPool(ctx, pool)
// update the validator, possibly kicking it out
validator = k.UpdateValidator(ctx, validator)
// remove validator if it has been reduced to zero shares
if validator.Tokens.IsZero() {
k.RemoveValidator(ctx, validator.Owner)
}
// Log that a slash occurred!
logger.Info(fmt.Sprintf(
"Validator %s slashed by slashFactor %v, burned %v tokens",
pubkey.Address(), slashFactor, tokensToBurn))
// TODO Return event(s), blocked on https://github.com/tendermint/tendermint/pull/1803
return
}
// revoke a validator
func (k Keeper) Revoke(ctx sdk.Context, pubkey crypto.PubKey) {
k.setRevoked(ctx, pubkey, true)
logger := ctx.Logger().With("module", "x/stake")
logger.Info(fmt.Sprintf("Validator %s revoked", pubkey.Address()))
// TODO Return event(s), blocked on https://github.com/tendermint/tendermint/pull/1803
return
}
// unrevoke a validator
func (k Keeper) Unrevoke(ctx sdk.Context, pubkey crypto.PubKey) {
k.setRevoked(ctx, pubkey, false)
logger := ctx.Logger().With("module", "x/stake")
logger.Info(fmt.Sprintf("Validator %s unrevoked", pubkey.Address()))
// TODO Return event(s), blocked on https://github.com/tendermint/tendermint/pull/1803
return
}
// set the revoked flag on a validator
func (k Keeper) setRevoked(ctx sdk.Context, pubkey crypto.PubKey, revoked bool) {
validator, found := k.GetValidatorByPubKey(ctx, pubkey)
if !found {
panic(fmt.Errorf("Validator with pubkey %s not found, cannot set revoked to %v", pubkey, revoked))
}
validator.Revoked = revoked
k.UpdateValidator(ctx, validator) // update validator, possibly unbonding or bonding it
return
}
// slash an unbonding delegation and update the pool
// return the amount that would have been slashed assuming
// the unbonding delegation had enough stake to slash
// (the amount actually slashed may be less if there's
// insufficient stake remaining)
func (k Keeper) slashUnbondingDelegation(ctx sdk.Context, unbondingDelegation types.UnbondingDelegation,
infractionHeight int64, slashFactor sdk.Rat) (slashAmount sdk.Rat) {
now := ctx.BlockHeader().Time
// If unbonding started before this height, stake didn't contribute to infraction
if unbondingDelegation.CreationHeight < infractionHeight {
return sdk.ZeroRat()
}
if unbondingDelegation.MinTime < now {
// Unbonding delegation no longer eligible for slashing, skip it
// TODO Settle and delete it automatically?
return sdk.ZeroRat()
}
// Calculate slash amount proportional to stake contributing to infraction
slashAmount = sdk.NewRatFromInt(unbondingDelegation.InitialBalance.Amount, sdk.OneInt()).Mul(slashFactor)
// Don't slash more tokens than held
// Possible since the unbonding delegation may already
// have been slashed, and slash amounts are calculated
// according to stake held at time of infraction
unbondingSlashAmount := sdk.MinInt(slashAmount.RoundInt(), unbondingDelegation.Balance.Amount)
// Update unbonding delegation if necessary
if !unbondingSlashAmount.IsZero() {
unbondingDelegation.Balance.Amount = unbondingDelegation.Balance.Amount.Sub(unbondingSlashAmount)
k.SetUnbondingDelegation(ctx, unbondingDelegation)
pool := k.GetPool(ctx)
// Burn loose tokens
// Ref https://github.com/cosmos/cosmos-sdk/pull/1278#discussion_r198657760
pool.LooseTokens = pool.LooseTokens.Sub(slashAmount)
k.SetPool(ctx, pool)
}
return
}
// slash a redelegation and update the pool
// return the amount that would have been slashed assuming
// the unbonding delegation had enough stake to slash
// (the amount actually slashed may be less if there's
// insufficient stake remaining)
func (k Keeper) slashRedelegation(ctx sdk.Context, validator types.Validator, redelegation types.Redelegation,
infractionHeight int64, slashFactor sdk.Rat) (slashAmount sdk.Rat) {
now := ctx.BlockHeader().Time
// If redelegation started before this height, stake didn't contribute to infraction
if redelegation.CreationHeight < infractionHeight {
return sdk.ZeroRat()
}
if redelegation.MinTime < now {
// Redelegation no longer eligible for slashing, skip it
// TODO Delete it automatically?
return sdk.ZeroRat()
}
// Calculate slash amount proportional to stake contributing to infraction
slashAmount = sdk.NewRatFromInt(redelegation.InitialBalance.Amount, sdk.OneInt()).Mul(slashFactor)
// Don't slash more tokens than held
// Possible since the redelegation may already
// have been slashed, and slash amounts are calculated
// according to stake held at time of infraction
redelegationSlashAmount := sdk.MinInt(slashAmount.RoundInt(), redelegation.Balance.Amount)
// Update redelegation if necessary
if !redelegationSlashAmount.IsZero() {
redelegation.Balance.Amount = redelegation.Balance.Amount.Sub(redelegationSlashAmount)
k.SetRedelegation(ctx, redelegation)
}
// Unbond from target validator
sharesToUnbond := slashFactor.Mul(redelegation.SharesDst)
if !sharesToUnbond.IsZero() {
delegation, found := k.GetDelegation(ctx, redelegation.DelegatorAddr, redelegation.ValidatorDstAddr)
if !found {
// If deleted, delegation has zero shares, and we can't unbond any more
return slashAmount
}
if sharesToUnbond.GT(delegation.Shares) {
sharesToUnbond = delegation.Shares
}
tokensToBurn, err := k.unbond(ctx, redelegation.DelegatorAddr, redelegation.ValidatorDstAddr, sharesToUnbond)
if err != nil {
panic(fmt.Errorf("error unbonding delegator: %v", err))
}
// Burn loose tokens
pool := k.GetPool(ctx)
pool.LooseTokens = pool.LooseTokens.Sub(tokensToBurn)
k.SetPool(ctx, pool)
}
return slashAmount
}