prysm-pulse/beacon-chain/forkchoice/doubly-linked-tree/proposer_boost_test.go

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package doublylinkedtree
import (
"context"
"testing"
"time"
"github.com/prysmaticlabs/prysm/v4/config/params"
"github.com/prysmaticlabs/prysm/v4/consensus-types/primitives"
"github.com/prysmaticlabs/prysm/v4/testing/assert"
"github.com/prysmaticlabs/prysm/v4/testing/require"
)
// Helper function to simulate the block being on time or delayed for proposer
// boost. It alters the genesisTime tracked by the store.
func driftGenesisTime(f *ForkChoice, slot primitives.Slot, delay uint64) {
f.SetGenesisTime(uint64(time.Now().Unix()) - uint64(slot)*params.BeaconConfig().SecondsPerSlot - delay)
}
// Simple, ex-ante attack mitigation using proposer boost.
// In a nutshell, an adversarial block proposer in slot n+1 keeps its proposal hidden.
// The honest block proposer in slot n+2 will then propose an honest block. The
// adversary can now use its committee members votes from both slots n+1 and n+2.
// and release their withheld block of slot n+2 in an attempt to win fork choice.
// If the honest proposal is boosted at slot n+2, it will win against this attacker.
func TestForkChoice_BoostProposerRoot_PreventsExAnteAttack(t *testing.T) {
ctx := context.Background()
jEpoch, fEpoch := primitives.Epoch(0), primitives.Epoch(0)
zeroHash := params.BeaconConfig().ZeroHash
balances := make([]uint64, 64) // 64 active validators.
for i := 0; i < len(balances); i++ {
balances[i] = 10
}
t.Run("back-propagates boost score to ancestors after proposer boosting", func(t *testing.T) {
f := setup(jEpoch, fEpoch)
f.justifiedBalances = balances
f.store.committeeWeight = uint64(len(balances)*10) / uint64(params.BeaconConfig().SlotsPerEpoch)
f.numActiveValidators = uint64(len(balances))
// The head should always start at the finalized block.
headRoot, err := f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, zeroHash, headRoot, "Incorrect head with genesis")
// Insert block at slot 1 into the tree and verify head is at that block:
// 0
// |
// 1 <- HEAD
slot := primitives.Slot(1)
driftGenesisTime(f, slot, 0)
newRoot := indexToHash(1)
f.store.proposerBoostRoot = [32]byte{}
state, blkRoot, err := prepareForkchoiceState(
ctx,
slot,
newRoot,
headRoot,
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
f.ProcessAttestation(ctx, []uint64{0}, newRoot, fEpoch)
headRoot, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, newRoot, headRoot, "Incorrect head for justified epoch at slot 1")
// Insert block at slot 2 into the tree and verify head is at that block:
// 0
// |
// 1
// |
// 2 <- HEAD
slot = primitives.Slot(2)
driftGenesisTime(f, slot, 0)
newRoot = indexToHash(2)
f.store.proposerBoostRoot = [32]byte{}
state, blkRoot, err = prepareForkchoiceState(
ctx,
slot,
newRoot,
headRoot,
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
f.ProcessAttestation(ctx, []uint64{1}, newRoot, fEpoch)
headRoot, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, newRoot, headRoot, "Incorrect head for justified epoch at slot 2")
// Insert block at slot 3 into the tree and verify head is at that block:
// 0
// |
// 1
// |
// 2
// |
// 3 <- HEAD
slot = primitives.Slot(3)
driftGenesisTime(f, slot, 0)
newRoot = indexToHash(3)
f.store.proposerBoostRoot = [32]byte{}
state, blkRoot, err = prepareForkchoiceState(
ctx,
slot,
newRoot,
headRoot,
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
f.ProcessAttestation(ctx, []uint64{2}, newRoot, fEpoch)
headRoot, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, newRoot, headRoot, "Incorrect head for justified epoch at slot 3")
// Insert a second block at slot 4 into the tree and boost its score.
// 0
// |
// 1
// |
// 2
// / \
// 3 |
// 4 <- HEAD
slot = primitives.Slot(4)
driftGenesisTime(f, slot, 0)
newRoot = indexToHash(4)
f.store.proposerBoostRoot = [32]byte{}
state, blkRoot, err = prepareForkchoiceState(
ctx,
slot,
newRoot,
indexToHash(2),
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
f.ProcessAttestation(ctx, []uint64{3}, newRoot, fEpoch)
headRoot, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, newRoot, headRoot, "Incorrect head for justified epoch at slot 3")
// Check the ancestor scores from the store.
require.Equal(t, 5, f.NodeCount())
// Expect nodes to have a boosted, back-propagated score.
// Ancestors have the added weights of their children. Genesis is a special exception at 0 weight,
require.Equal(t, f.store.treeRootNode.weight, uint64(0))
// Proposer boost score with these test parameters is 8
// Each of the nodes received one attestation accounting for 10.
// Node D is the only one with proposer boost still applied:
//
// (1: 48) -> (2: 38) -> (3: 10)
// \--------------->(4: 18)
//
node1 := f.store.nodeByRoot[indexToHash(1)]
require.Equal(t, node1.weight, uint64(48))
node2 := f.store.nodeByRoot[indexToHash(2)]
require.Equal(t, node2.weight, uint64(38))
node3 := f.store.nodeByRoot[indexToHash(3)]
require.Equal(t, node3.weight, uint64(10))
node4 := f.store.nodeByRoot[indexToHash(4)]
require.Equal(t, node4.weight, uint64(18))
// Regression: process attestations for C, check that it
// becomes head, we need two attestations to have C.weight = 30 > 24 = D.weight
f.ProcessAttestation(ctx, []uint64{4, 5}, indexToHash(3), fEpoch)
headRoot, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, indexToHash(3), headRoot, "Incorrect head for justified epoch at slot 4")
})
t.Run("vanilla ex ante attack", func(t *testing.T) {
f := setup(jEpoch, fEpoch)
f.justifiedBalances = balances
// The head should always start at the finalized block.
r, err := f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, zeroHash, r, "Incorrect head with genesis")
// Proposer from slot 1 does not reveal their block, B, at slot 1.
// Proposer at slot 2 does reveal their block, C, and it becomes the head.
// C builds on A, as proposer at slot 1 did not reveal B.
// A
// / \
// (B?) \
// \
// C <- Slot 2 HEAD
honestBlockSlot := primitives.Slot(2)
driftGenesisTime(f, honestBlockSlot, 0)
honestBlock := indexToHash(2)
state, blkRoot, err := prepareForkchoiceState(
ctx,
honestBlockSlot,
honestBlock,
zeroHash,
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
r, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, honestBlock, r, "Incorrect head for justified epoch at slot 2")
maliciouslyWithheldBlockSlot := primitives.Slot(1)
maliciouslyWithheldBlock := indexToHash(1)
state, blkRoot, err = prepareForkchoiceState(
ctx,
maliciouslyWithheldBlockSlot,
maliciouslyWithheldBlock,
zeroHash,
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
// Ensure the head is C, the honest block.
r, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, honestBlock, r, "Incorrect head for justified epoch at slot 2")
// The maliciously withheld block has one vote.
votes := []uint64{1}
f.ProcessAttestation(ctx, votes, maliciouslyWithheldBlock, fEpoch)
// The honest block has one vote.
votes = []uint64{2}
f.ProcessAttestation(ctx, votes, honestBlock, fEpoch)
// Ensure the head is STILL C, the honest block, as the honest block had proposer boost.
r, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, honestBlock, r, "Incorrect head for justified epoch at slot 2")
})
t.Run("adversarial attestations > proposer boosting", func(t *testing.T) {
f := setup(jEpoch, fEpoch)
f.justifiedBalances = balances
// The head should always start at the finalized block.
r, err := f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, zeroHash, r, "Incorrect head with genesis")
// Proposer from slot 1 does not reveal their block, B, at slot 1.
// Proposer at slot 2 does reveal their block, C, and it becomes the head.
// C builds on A, as proposer at slot 1 did not reveal B.
// A
// / \
// (B?) \
// \
// C <- Slot 2 HEAD
honestBlockSlot := primitives.Slot(2)
driftGenesisTime(f, honestBlockSlot, 0)
honestBlock := indexToHash(2)
state, blkRoot, err := prepareForkchoiceState(
ctx,
honestBlockSlot,
honestBlock,
zeroHash,
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
// Ensure C is the head.
r, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, honestBlock, r, "Incorrect head for justified epoch at slot 2")
maliciouslyWithheldBlockSlot := primitives.Slot(1)
maliciouslyWithheldBlock := indexToHash(1)
state, blkRoot, err = prepareForkchoiceState(
ctx,
maliciouslyWithheldBlockSlot,
maliciouslyWithheldBlock,
zeroHash,
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
// Ensure C is still the head after the malicious proposer reveals their block.
r, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, honestBlock, r, "Incorrect head for justified epoch at slot 2")
// An attestation is received for B that has more voting power than C with the proposer boost,
// allowing B to then become the head if their attestation has enough adversarial votes.
votes := []uint64{1, 2}
f.ProcessAttestation(ctx, votes, maliciouslyWithheldBlock, fEpoch)
// Expect the head to have switched to B.
r, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, maliciouslyWithheldBlock, r, "Expected B to become the head")
})
t.Run("boosting necessary to sandwich attack", func(t *testing.T) {
// Boosting necessary to sandwich attack.
// Objects:
// Block A - slot N
// Block B (parent A) - slot N+1
// Block C (parent A) - slot N+2
// Block D (parent B) - slot N+3
// Attestation_1 (Block C); size 1 - slot N+2 (honest)
// Steps:
// Block A received at N — A is head
// Block C received at N+2 — C is head
// Block B received at N+2 — C is head
// Attestation_1 received at N+3 — C is head
// Block D received at N+3 — D is head
f := setup(jEpoch, fEpoch)
f.justifiedBalances = balances
f.store.committeeWeight = uint64(len(balances)*10) / uint64(params.BeaconConfig().SlotsPerEpoch)
f.numActiveValidators = uint64(len(balances))
a := zeroHash
// The head should always start at the finalized block.
r, err := f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, zeroHash, r, "Incorrect head with genesis")
cSlot := primitives.Slot(2)
driftGenesisTime(f, cSlot, 0)
c := indexToHash(2)
f.store.proposerBoostRoot = [32]byte{}
state, blkRoot, err := prepareForkchoiceState(
ctx,
cSlot,
c,
a, // parent
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
// Ensure C is the head.
r, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, c, r, "Incorrect head for justified epoch at slot 2")
bSlot := primitives.Slot(1)
b := indexToHash(1)
f.store.proposerBoostRoot = [32]byte{}
state, blkRoot, err = prepareForkchoiceState(
ctx,
bSlot,
b,
a, // parent
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
// Ensure C is still the head.
r, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, c, r, "Incorrect head for justified epoch at slot 2")
// An attestation for C is received at slot N+3.
votes := []uint64{1}
f.ProcessAttestation(ctx, votes, c, fEpoch)
// A block D, building on B, is received at slot N+3. It should not be able to win without boosting.
dSlot := primitives.Slot(3)
d := indexToHash(3)
f.store.proposerBoostRoot = [32]byte{}
state, blkRoot, err = prepareForkchoiceState(
ctx,
dSlot,
d,
b, // parent
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
// D cannot win without a boost.
r, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, c, r, "Expected C to remain the head")
// If the same block arrives with boosting then it becomes head:
driftGenesisTime(f, dSlot, 0)
d2 := indexToHash(30)
f.store.proposerBoostRoot = [32]byte{}
state, blkRoot, err = prepareForkchoiceState(
ctx,
dSlot,
d2,
b, // parent
zeroHash,
jEpoch,
fEpoch,
)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
votes = []uint64{2}
f.ProcessAttestation(ctx, votes, d2, fEpoch)
// Ensure D becomes the head thanks to boosting.
r, err = f.Head(ctx)
require.NoError(t, err)
assert.Equal(t, d2, r, "Expected D to become the head")
})
}
func TestForkChoice_BoostProposerRoot(t *testing.T) {
ctx := context.Background()
root := [32]byte{'A'}
var zeroHash [32]byte
t.Run("does not boost block from different slot", func(t *testing.T) {
f := setup(0, 0)
slot := primitives.Slot(0)
currentSlot := primitives.Slot(1)
driftGenesisTime(f, currentSlot, 0)
state, blkRoot, err := prepareForkchoiceState(ctx, slot, root, zeroHash, zeroHash, 0, 0)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
require.Equal(t, [32]byte{}, f.store.proposerBoostRoot)
})
t.Run("does not boost untimely block from same slot", func(t *testing.T) {
f := setup(0, 0)
slot := primitives.Slot(1)
currentSlot := primitives.Slot(1)
driftGenesisTime(f, currentSlot, params.BeaconConfig().SecondsPerSlot-1)
state, blkRoot, err := prepareForkchoiceState(ctx, slot, root, zeroHash, zeroHash, 0, 0)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
require.Equal(t, [32]byte{}, f.store.proposerBoostRoot)
})
t.Run("boosts perfectly timely block from same slot", func(t *testing.T) {
f := setup(0, 0)
slot := primitives.Slot(1)
currentSlot := primitives.Slot(1)
driftGenesisTime(f, currentSlot, 0)
state, blkRoot, err := prepareForkchoiceState(ctx, slot, root, zeroHash, zeroHash, 0, 0)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
require.Equal(t, root, f.store.proposerBoostRoot)
})
t.Run("boosts timely block from same slot", func(t *testing.T) {
f := setup(0, 0)
slot := primitives.Slot(1)
currentSlot := primitives.Slot(1)
driftGenesisTime(f, currentSlot, 1)
state, blkRoot, err := prepareForkchoiceState(ctx, slot, root, zeroHash, zeroHash, 0, 0)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, state, blkRoot))
require.Equal(t, root, f.store.proposerBoostRoot)
})
}
// Regression test (11053)
func TestForkChoice_missingProposerBoostRoots(t *testing.T) {
ctx := context.Background()
f := setup(1, 1)
balances := make([]uint64, 64) // 64 active validators.
for i := 0; i < len(balances); i++ {
balances[i] = 10
}
f.justifiedBalances = balances
driftGenesisTime(f, 1, 0)
st, root, err := prepareForkchoiceState(ctx, 1, [32]byte{'r'}, [32]byte{}, [32]byte{}, 1, 1)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, st, root))
f.store.previousProposerBoostRoot = [32]byte{'p'}
headRoot, err := f.Head(ctx)
require.NoError(t, err)
require.Equal(t, root, headRoot)
require.Equal(t, [32]byte{'r'}, f.store.proposerBoostRoot)
f.store.proposerBoostRoot = [32]byte{'p'}
driftGenesisTime(f, 3, 0)
st, root, err = prepareForkchoiceState(ctx, 2, [32]byte{'a'}, [32]byte{'r'}, [32]byte{}, 1, 1)
require.NoError(t, err)
require.NoError(t, f.InsertNode(ctx, st, root))
headRoot, err = f.Head(ctx)
require.NoError(t, err)
require.Equal(t, root, headRoot)
require.Equal(t, [32]byte{'p'}, f.store.proposerBoostRoot)
}