prysm-pulse/beacon-chain/slasher/chunks.go
terencechain d17996f8b0
Update to V4 🚀 (#12134)
* Update V3 from V4

* Fix build v3 -> v4

* Update ssz

* Update beacon_chain.pb.go

* Fix formatter import

* Update update-mockgen.sh comment to v4

* Fix conflicts. Pass build and tests

* Fix test
2023-03-17 18:52:56 +00:00

554 lines
22 KiB
Go

package slasher
import (
"context"
"fmt"
"math"
"github.com/pkg/errors"
"github.com/prysmaticlabs/prysm/v4/beacon-chain/db"
slashertypes "github.com/prysmaticlabs/prysm/v4/beacon-chain/slasher/types"
"github.com/prysmaticlabs/prysm/v4/consensus-types/primitives"
ethpb "github.com/prysmaticlabs/prysm/v4/proto/prysm/v1alpha1"
)
// A struct encapsulating input arguments to
// functions used for attester slashing detection and
// loading, saving, and updating min/max span chunks.
type chunkUpdateArgs struct {
kind slashertypes.ChunkKind
chunkIndex uint64
validatorChunkIndex uint64
currentEpoch primitives.Epoch
}
// Chunker defines a struct which represents a slice containing a chunk for K different validator's
// min spans used for surround vote detection in slasher. The interface defines methods used to check
// if an attestation is slashable for a validator index based on the contents of
// the chunk as well as the ability to update the data in the chunk with incoming information.
type Chunker interface {
NeutralElement() uint16
Chunk() []uint16
CheckSlashable(
ctx context.Context,
slasherDB db.SlasherDatabase,
validatorIdx primitives.ValidatorIndex,
attestation *slashertypes.IndexedAttestationWrapper,
) (*ethpb.AttesterSlashing, error)
Update(
args *chunkUpdateArgs,
validatorIndex primitives.ValidatorIndex,
startEpoch,
newTargetEpoch primitives.Epoch,
) (keepGoing bool, err error)
StartEpoch(sourceEpoch, currentEpoch primitives.Epoch) (epoch primitives.Epoch, exists bool)
NextChunkStartEpoch(startEpoch primitives.Epoch) primitives.Epoch
}
// MinSpanChunksSlice represents a slice containing a chunk for K different validator's min spans.
//
// For a given epoch, e, and attestations a validator index has produced, atts,
// min_spans[e] is defined as min((att.target.epoch - e) for att in attestations)
// where att.source.epoch > e. That is, it is the minimum distance between the
// specified epoch and all attestation target epochs a validator has created
// where att.source.epoch > e.
//
// Under ideal network conditions, where every target epoch immediately follows its source,
// min spans for a validator will look as follows:
//
// min_spans = [2, 2, 2, ..., 2]
//
// Next, we can chunk this list of min spans into chunks of length C. For C = 2, for example:
//
// chunk0 chunk1 chunkN
// { } { } { }
// chunked_min_spans = [[2, 2], [2, 2], ..., [2, 2]]
//
// Finally, we can store each chunk index for K validators into a single flat slice. For K = 3:
//
// val0 val1 val2
// { } { } { }
// chunk_0_for_validators_0_to_2 = [[2, 2], [2, 2], [2, 2]]
//
// val0 val1 val2
// { } { } { }
// chunk_1_for_validators_0_to_2 = [[2, 2], [2, 2], [2, 2]]
//
// ...
//
// val0 val1 val2
// { } { } { }
// chunk_N_for_validators_0_to_2 = [[2, 2], [2, 2], [2, 2]]
//
// MinSpanChunksSlice represents the data structure above for a single chunk index.
type MinSpanChunksSlice struct {
params *Parameters
data []uint16
}
// MaxSpanChunksSlice represents the same data structure as MinSpanChunksSlice however
// keeps track of validator max spans for slashing detection instead.
type MaxSpanChunksSlice struct {
params *Parameters
data []uint16
}
// EmptyMinSpanChunksSlice initializes a min span chunk of length C*K for
// C = chunkSize and K = validatorChunkSize filled with neutral elements.
// For min spans, the neutral element is `undefined`, represented by MaxUint16.
func EmptyMinSpanChunksSlice(params *Parameters) *MinSpanChunksSlice {
m := &MinSpanChunksSlice{
params: params,
}
data := make([]uint16, params.chunkSize*params.validatorChunkSize)
for i := 0; i < len(data); i++ {
data[i] = m.NeutralElement()
}
m.data = data
return m
}
// EmptyMaxSpanChunksSlice initializes a max span chunk of length C*K for
// C = chunkSize and K = validatorChunkSize filled with neutral elements.
// For max spans, the neutral element is 0.
func EmptyMaxSpanChunksSlice(params *Parameters) *MaxSpanChunksSlice {
m := &MaxSpanChunksSlice{
params: params,
}
data := make([]uint16, params.chunkSize*params.validatorChunkSize)
for i := 0; i < len(data); i++ {
data[i] = m.NeutralElement()
}
m.data = data
return m
}
// MinChunkSpansSliceFrom initializes a min span chunks slice from a slice of uint16 values.
// Returns an error if the slice is not of length C*K for C = chunkSize and K = validatorChunkSize.
func MinChunkSpansSliceFrom(params *Parameters, chunk []uint16) (*MinSpanChunksSlice, error) {
requiredLen := params.chunkSize * params.validatorChunkSize
if uint64(len(chunk)) != requiredLen {
return nil, fmt.Errorf("chunk has wrong length, %d, expected %d", len(chunk), requiredLen)
}
return &MinSpanChunksSlice{
params: params,
data: chunk,
}, nil
}
// MaxChunkSpansSliceFrom initializes a max span chunks slice from a slice of uint16 values.
// Returns an error if the slice is not of length C*K for C = chunkSize and K = validatorChunkSize.
func MaxChunkSpansSliceFrom(params *Parameters, chunk []uint16) (*MaxSpanChunksSlice, error) {
requiredLen := params.chunkSize * params.validatorChunkSize
if uint64(len(chunk)) != requiredLen {
return nil, fmt.Errorf("chunk has wrong length, %d, expected %d", len(chunk), requiredLen)
}
return &MaxSpanChunksSlice{
params: params,
data: chunk,
}, nil
}
// NeutralElement for a min span chunks slice is undefined, in this case
// using MaxUint16 as a sane value given it is impossible we reach it.
func (_ *MinSpanChunksSlice) NeutralElement() uint16 {
return math.MaxUint16
}
// NeutralElement for a max span chunks slice is 0.
func (_ *MaxSpanChunksSlice) NeutralElement() uint16 {
return 0
}
// Chunk returns the underlying slice of uint16's for the min chunks slice.
func (m *MinSpanChunksSlice) Chunk() []uint16 {
return m.data
}
// Chunk returns the underlying slice of uint16's for the max chunks slice.
func (m *MaxSpanChunksSlice) Chunk() []uint16 {
return m.data
}
// CheckSlashable takes in a validator index and an incoming attestation
// and checks if the validator is slashable depending on the data
// within the min span chunks slice. Recall that for an incoming attestation, B, and an
// existing attestation, A:
//
// B surrounds A if and only if B.target > min_spans[B.source]
//
// That is, this condition is sufficient to check if an incoming attestation
// is surrounding a previous one. We also check if we indeed have an existing
// attestation record in the database if the condition holds true in order
// to be confident of a slashable offense.
func (m *MinSpanChunksSlice) CheckSlashable(
ctx context.Context,
slasherDB db.SlasherDatabase,
validatorIdx primitives.ValidatorIndex,
attestation *slashertypes.IndexedAttestationWrapper,
) (*ethpb.AttesterSlashing, error) {
sourceEpoch := attestation.IndexedAttestation.Data.Source.Epoch
targetEpoch := attestation.IndexedAttestation.Data.Target.Epoch
minTarget, err := chunkDataAtEpoch(m.params, m.data, validatorIdx, sourceEpoch)
if err != nil {
return nil, errors.Wrapf(
err, "could not get min target for validator %d at epoch %d", validatorIdx, sourceEpoch,
)
}
if targetEpoch > minTarget {
existingAttRecord, err := slasherDB.AttestationRecordForValidator(
ctx, validatorIdx, minTarget,
)
if err != nil {
return nil, errors.Wrapf(
err, "could not get existing attestation record at target %d", minTarget,
)
}
if existingAttRecord != nil {
if sourceEpoch < existingAttRecord.IndexedAttestation.Data.Source.Epoch {
surroundingVotesTotal.Inc()
return &ethpb.AttesterSlashing{
Attestation_1: attestation.IndexedAttestation,
Attestation_2: existingAttRecord.IndexedAttestation,
}, nil
}
}
}
return nil, nil
}
// CheckSlashable takes in a validator index and an incoming attestation
// and checks if the validator is slashable depending on the data
// within the max span chunks slice. Recall that for an incoming attestation, B, and an
// existing attestation, A:
//
// B surrounds A if and only if B.target < max_spans[B.source]
//
// That is, this condition is sufficient to check if an incoming attestation
// is surrounded by a previous one. We also check if we indeed have an existing
// attestation record in the database if the condition holds true in order
// to be confident of a slashable offense.
func (m *MaxSpanChunksSlice) CheckSlashable(
ctx context.Context,
slasherDB db.SlasherDatabase,
validatorIdx primitives.ValidatorIndex,
attestation *slashertypes.IndexedAttestationWrapper,
) (*ethpb.AttesterSlashing, error) {
sourceEpoch := attestation.IndexedAttestation.Data.Source.Epoch
targetEpoch := attestation.IndexedAttestation.Data.Target.Epoch
maxTarget, err := chunkDataAtEpoch(m.params, m.data, validatorIdx, sourceEpoch)
if err != nil {
return nil, errors.Wrapf(
err, "could not get max target for validator %d at epoch %d", validatorIdx, sourceEpoch,
)
}
if targetEpoch < maxTarget {
existingAttRecord, err := slasherDB.AttestationRecordForValidator(
ctx, validatorIdx, maxTarget,
)
if err != nil {
return nil, errors.Wrapf(
err, "could not get existing attestation record at target %d", maxTarget,
)
}
if existingAttRecord != nil {
if existingAttRecord.IndexedAttestation.Data.Source.Epoch < sourceEpoch {
surroundedVotesTotal.Inc()
return &ethpb.AttesterSlashing{
Attestation_1: existingAttRecord.IndexedAttestation,
Attestation_2: attestation.IndexedAttestation,
}, nil
}
}
}
return nil, nil
}
// Update a min span chunk for a validator index starting at the current epoch, e_c, then updating
// down to e_c - H where H is the historyLength we keep for each span. This historyLength
// corresponds to the weak subjectivity period of Ethereum consensus.
// This means our updates are done in a sliding window manner. For example, if the current epoch
// is 20 and the historyLength is 12, then we will update every value for the validator's min span
// from epoch 20 down to epoch 9.
//
// Recall that for an epoch, e, min((att.target - e) for att in attestations where att.source > e)
// That is, it is the minimum distance between the specified epoch and all attestation
// target epochs a validator has created where att.source.epoch > e.
//
// Recall that a MinSpanChunksSlice struct represents a single slice for a chunk index
// from the collection below:
//
// val0 val1 val2
// { } { } { }
// chunk_0_for_validators_0_to_2 = [[2, 2], [2, 2], [2, 2]]
//
// val0 val1 val2
// { } { } { }
// chunk_1_for_validators_0_to_2 = [[2, 2], [2, 2], [2, 2]]
//
// ...
//
// val0 val1 val2
// { } { } { }
// chunk_N_for_validators_0_to_2 = [[2, 2], [2, 2], [2, 2]]
//
// Let's take a look at how this update will look for a real set of min span chunk:
// For the purposes of a simple example, let's set H = 2, meaning a min span
// will hold 2 epochs worth of attesting history. Then we set C = 2 meaning we will
// chunk the min span into arrays each of length 2.
//
// So assume we get an epoch 4 and validator 0, then, we need to update every epoch in the span from
// 4 down to 3. First, we find out which chunk epoch 4 falls into, which is calculated as:
// chunk_idx = (epoch % H) / C = (4 % 2) / 2 = 0
//
// val0 val1 val2
// { } { } { }
// chunk_0_for_validators_0_to_3 = [[2, 2], [2, 2], [2, 2]]
// |
// |-> epoch 4 for validator 0
//
// Next up, we proceed with the update process for validator index 0, starting at epoch 4
// all the way down to epoch 2. We will need to go down the array as far as we can get. If the
// lowest epoch we need to update is < the lowest epoch of a chunk, we need to proceed to
// a different chunk index.
//
// Once we finish updating a chunk, we need to move on to the next chunk. This function
// returns a boolean named keepGoing which allows the caller to determine if we should
// continue and update another chunk index. We stop whenever we reach the min epoch we need
// to update. In our example, we stop at 2, which is still part of chunk 0, so no need
// to jump to another min span chunks slice to perform updates.
func (m *MinSpanChunksSlice) Update(
args *chunkUpdateArgs,
validatorIndex primitives.ValidatorIndex,
startEpoch,
newTargetEpoch primitives.Epoch,
) (keepGoing bool, err error) {
// The lowest epoch we need to update.
minEpoch := primitives.Epoch(0)
if args.currentEpoch > (m.params.historyLength - 1) {
minEpoch = args.currentEpoch - (m.params.historyLength - 1)
}
epochInChunk := startEpoch
// We go down the chunk for the validator, updating every value starting at start_epoch down to min_epoch.
// As long as the epoch, e, in the same chunk index and e >= min_epoch, we proceed with
// a for loop.
for m.params.chunkIndex(epochInChunk) == args.chunkIndex && epochInChunk >= minEpoch {
var chunkTarget primitives.Epoch
chunkTarget, err = chunkDataAtEpoch(m.params, m.data, validatorIndex, epochInChunk)
if err != nil {
err = errors.Wrapf(err, "could not get chunk data at epoch %d", epochInChunk)
return
}
// If the newly incoming value is < the existing value, we update
// the data in the min span to meet with its definition.
if newTargetEpoch < chunkTarget {
if err = setChunkDataAtEpoch(m.params, m.data, validatorIndex, epochInChunk, newTargetEpoch); err != nil {
err = errors.Wrapf(err, "could not set chunk data at epoch %d", epochInChunk)
return
}
} else {
// We can stop because spans are guaranteed to be minimums and
// if we did not meet the minimum condition, there is nothing to update.
return
}
if epochInChunk > 0 {
epochInChunk -= 1
}
}
// We should keep going and update the previous chunk if we are yet to reach
// the minimum epoch required for the update procedure.
keepGoing = epochInChunk >= minEpoch
return
}
// Update a max span chunk for a validator index starting at a given start epoch, e_c, then updating
// up to the current epoch according to the definition of max spans. If we need to continue updating
// a next chunk, this function returns a boolean letting the caller know it should keep going. To understand
// more about how update exactly works, refer to the detailed documentation for the Update function for
// MinSpanChunksSlice.
func (m *MaxSpanChunksSlice) Update(
args *chunkUpdateArgs,
validatorIndex primitives.ValidatorIndex,
startEpoch,
newTargetEpoch primitives.Epoch,
) (keepGoing bool, err error) {
epochInChunk := startEpoch
// We go down the chunk for the validator, updating every value starting at start_epoch up to
// and including the current epoch. As long as the epoch, e, is in the same chunk index and e <= currentEpoch,
// we proceed with a for loop.
for m.params.chunkIndex(epochInChunk) == args.chunkIndex && epochInChunk <= args.currentEpoch {
var chunkTarget primitives.Epoch
chunkTarget, err = chunkDataAtEpoch(m.params, m.data, validatorIndex, epochInChunk)
if err != nil {
err = errors.Wrapf(err, "could not get chunk data at epoch %d", epochInChunk)
return
}
// If the newly incoming value is > the existing value, we update
// the data in the max span to meet with its definition.
if newTargetEpoch > chunkTarget {
if err = setChunkDataAtEpoch(m.params, m.data, validatorIndex, epochInChunk, newTargetEpoch); err != nil {
err = errors.Wrapf(err, "could not set chunk data at epoch %d", epochInChunk)
return
}
} else {
// We can stop because spans are guaranteed to be maxima and
// if we did not meet the condition, there is nothing to update.
return
}
epochInChunk++
}
// If the epoch to update now lies beyond the current chunk, then
// continue to the next chunk to update it.
keepGoing = epochInChunk <= args.currentEpoch
return
}
// StartEpoch given a source epoch and current epoch, determines the start epoch of
// a min span chunk for use in chunk updates. To compute this value, we look at the difference between
// H = historyLength and the current epoch. Then, we check if the source epoch > difference. If so,
// then the start epoch is source epoch - 1. Otherwise, we return to the caller a boolean signifying
// the input argumets are invalid for the chunk and the start epoch does not exist.
func (m *MinSpanChunksSlice) StartEpoch(
sourceEpoch, currentEpoch primitives.Epoch,
) (epoch primitives.Epoch, exists bool) {
// Given min span chunks are used for detecting surrounding votes, we have no need
// for a start epoch of the chunk if the source epoch is 0 in the input arguments.
// To further clarify, min span chunks are updated in reverse order [a, b, c, d] where
// if the start epoch is d, then we go down the chunk updating everything from d, c, b, to
// a. If the source epoch is 0, this would correspond to a, which means there is nothing
// more to update.
if sourceEpoch == 0 {
return
}
var difference primitives.Epoch
if currentEpoch > m.params.historyLength {
difference = currentEpoch - m.params.historyLength
}
if sourceEpoch <= difference {
return
}
epoch = sourceEpoch.Sub(1)
exists = true
return
}
// StartEpoch given a source epoch and current epoch, determines the start epoch of
// a max span chunk for use in chunk updates. The source epoch cannot be >= the current epoch.
func (_ *MaxSpanChunksSlice) StartEpoch(
sourceEpoch, currentEpoch primitives.Epoch,
) (epoch primitives.Epoch, exists bool) {
if sourceEpoch >= currentEpoch {
return
}
// Given max spans is a list of max targets for source epochs, the precondition is that
// every attestation's source epoch must be < than its target epoch. So the start epoch
// for updates is given as source epoch + 1.
epoch = sourceEpoch.Add(1)
exists = true
return
}
// NextChunkStartEpoch given an epoch, determines the start epoch of the next chunk. For min
// span chunks, this will be the last epoch of chunk index = (current chunk - 1). For example:
//
// chunk0 chunk1 chunk2
// | | |
// max_spans_val_i = [[-, -, -], [-, -, -], [-, -, -]]
//
// If C = chunkSize is 3 epochs per chunk, and we input start epoch of chunk 1 which is 3 then the next start
// epoch is the last epoch of chunk 0, which is epoch 2. This is computed as:
//
// last_epoch(chunkIndex(startEpoch)-1)
// last_epoch(chunkIndex(3) - 1)
// last_epoch(1 - 1)
// last_epoch(0)
// 2
func (m *MinSpanChunksSlice) NextChunkStartEpoch(startEpoch primitives.Epoch) primitives.Epoch {
prevChunkIdx := m.params.chunkIndex(startEpoch)
if prevChunkIdx > 0 {
prevChunkIdx--
}
return m.params.lastEpoch(prevChunkIdx)
}
// NextChunkStartEpoch given an epoch, determines the start epoch of the next chunk. For max
// span chunks, this will be the start epoch of chunk index = (current chunk + 1). For example:
//
// chunk0 chunk1 chunk2
// | | |
// max_spans_val_i = [[-, -, -], [-, -, -], [-, -, -]]
//
// If C = chunkSize is 3 epochs per chunk, and we input start epoch of chunk 1 which is 3. The next start
// epoch is the start epoch of chunk 2, which is epoch 4. This is computed as:
//
// first_epoch(chunkIndex(startEpoch)+1)
// first_epoch(chunkIndex(3)+1)
// first_epoch(1 + 1)
// first_epoch(2)
// 4
func (m *MaxSpanChunksSlice) NextChunkStartEpoch(startEpoch primitives.Epoch) primitives.Epoch {
return m.params.firstEpoch(m.params.chunkIndex(startEpoch) + 1)
}
// Given a validator index and epoch, retrieves the target epoch at its specific
// index for the validator index and epoch in a min/max span chunk.
func chunkDataAtEpoch(
params *Parameters, chunk []uint16, validatorIdx primitives.ValidatorIndex, epoch primitives.Epoch,
) (primitives.Epoch, error) {
requiredLen := params.chunkSize * params.validatorChunkSize
if uint64(len(chunk)) != requiredLen {
return 0, fmt.Errorf("chunk has wrong length, %d, expected %d", len(chunk), requiredLen)
}
cellIdx := params.cellIndex(validatorIdx, epoch)
if cellIdx >= uint64(len(chunk)) {
return 0, fmt.Errorf("cell index %d out of bounds (len(chunk) = %d)", cellIdx, len(chunk))
}
distance := chunk[cellIdx]
return epoch.Add(uint64(distance)), nil
}
// Updates the value at a specific index in a chunk for a validator index + epoch
// pair given a target epoch. Recall that for min spans, each element in a chunk
// is the minimum distance between the a given epoch, e, and all attestation target epochs
// a validator has created where att.source.epoch > e.
func setChunkDataAtEpoch(
params *Parameters,
chunk []uint16,
validatorIdx primitives.ValidatorIndex,
epochInChunk,
targetEpoch primitives.Epoch,
) error {
distance, err := epochDistance(targetEpoch, epochInChunk)
if err != nil {
return err
}
return setChunkRawDistance(params, chunk, validatorIdx, epochInChunk, distance)
}
// Updates the value at a specific index in a chunk for a validator index and epoch
// to a specified, raw distance value.
func setChunkRawDistance(
params *Parameters,
chunk []uint16,
validatorIdx primitives.ValidatorIndex,
epochInChunk primitives.Epoch,
distance uint16,
) error {
cellIdx := params.cellIndex(validatorIdx, epochInChunk)
if cellIdx >= uint64(len(chunk)) {
return fmt.Errorf("cell index %d out of bounds (len(chunk) = %d)", cellIdx, len(chunk))
}
chunk[cellIdx] = distance
return nil
}
// Computes a distance between two epochs. Given the result stored in
// min/max spans is at maximum WEAK_SUBJECTIVITY_PERIOD, we are guaranteed the
// distance can be represented as a uint16 safely.
func epochDistance(epoch, baseEpoch primitives.Epoch) (uint16, error) {
if baseEpoch > epoch {
return 0, fmt.Errorf("base epoch %d cannot be less than epoch %d", baseEpoch, epoch)
}
return uint16(epoch.Sub(uint64(baseEpoch))), nil
}