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*: harden partial signature exchange #4599

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14 changes: 8 additions & 6 deletions core/parsigex/parsigex.go
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Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,7 @@ func Protocols() []protocol.ID {
}

func NewParSigEx(p2pNode host.Host, sendFunc p2p.SendFunc, peerIdx int, peers []peer.ID,
verifyFunc func(context.Context, core.Duty, core.PubKey, core.ParSignedData) error,
verifyFunc func(context.Context, peer.ID, core.Duty, core.PubKey, core.ParSignedData) error,
gaterFunc core.DutyGaterFunc, p2pOpts ...p2p.SendRecvOption,
) *ParSigEx {
parSigEx := &ParSigEx{
Expand Down Expand Up @@ -72,12 +72,12 @@ type ParSigEx struct {
sendFunc p2p.SendFunc
peerIdx int
peers []peer.ID
verifyFunc func(context.Context, core.Duty, core.PubKey, core.ParSignedData) error
verifyFunc func(context.Context, peer.ID, core.Duty, core.PubKey, core.ParSignedData) error
gaterFunc core.DutyGaterFunc
subs []func(context.Context, core.Duty, core.ParSignedDataSet) error
}

func (m *ParSigEx) handle(ctx context.Context, _ peer.ID, req proto.Message) (proto.Message, bool, error) {
func (m *ParSigEx) handle(ctx context.Context, sender peer.ID, req proto.Message) (proto.Message, bool, error) {
pb, ok := req.(*pbv1.ParSigExMsg)
if !ok {
return nil, false, errors.New("invalid request type")
Expand Down Expand Up @@ -110,7 +110,7 @@ func (m *ParSigEx) handle(ctx context.Context, _ peer.ID, req proto.Message) (pr
verifyStart := time.Now()

for pubkey, data := range set {
if err = m.verifyFunc(ctx, duty, pubkey, data); err != nil {
if err = m.verifyFunc(ctx, sender, duty, pubkey, data); err != nil {
return nil, false, errors.Wrap(err, "invalid partial signature")
}
}
Expand Down Expand Up @@ -165,8 +165,10 @@ func (m *ParSigEx) Subscribe(fn func(context.Context, core.Duty, core.ParSignedD
}

// NewEth2Verifier returns a partial signature verification function for core workflow eth2 signatures.
func NewEth2Verifier(eth2Cl eth2wrap.Client, pubSharesByKey map[core.PubKey]map[int]tbls.PublicKey) (func(context.Context, core.Duty, core.PubKey, core.ParSignedData) error, error) {
return func(ctx context.Context, duty core.Duty, pubkey core.PubKey, data core.ParSignedData) error {
// Core workflow partial signatures are verified cryptographically against the pubshare for the
// claimed share index, so the authenticated sender is not needed here.
func NewEth2Verifier(eth2Cl eth2wrap.Client, pubSharesByKey map[core.PubKey]map[int]tbls.PublicKey) (func(context.Context, peer.ID, core.Duty, core.PubKey, core.ParSignedData) error, error) {
return func(ctx context.Context, _ peer.ID, duty core.Duty, pubkey core.PubKey, data core.ParSignedData) error {
pubshares, ok := pubSharesByKey[pubkey]
if !ok {
return errors.New("unknown pubkey, not part of cluster lock")
Expand Down
26 changes: 13 additions & 13 deletions core/parsigex/parsigex_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -73,7 +73,7 @@ func TestParSigEx(t *testing.T) {
}
}

verifyFunc := func(context.Context, core.Duty, core.PubKey, core.ParSignedData) error {
verifyFunc := func(context.Context, peer.ID, core.Duty, core.PubKey, core.ParSignedData) error {
return nil
}

Expand Down Expand Up @@ -171,7 +171,7 @@ func TestParSigExVerifier(t *testing.T) {
att.Deneb.Signature = sign(sigData[:])
data, err := core.NewPartialVersionedAttestation(att, shareIdx)
require.NoError(t, err)
require.NoError(t, verifyFunc(ctx, core.NewAttesterDuty(slot), pubkey, data))
require.NoError(t, verifyFunc(ctx, "", core.NewAttesterDuty(slot), pubkey, data))
})

t.Run("Verify proposal", func(t *testing.T) {
Expand All @@ -186,7 +186,7 @@ func TestParSigExVerifier(t *testing.T) {
data, err := core.NewPartialVersionedSignedProposal(proposal, shareIdx)
require.NoError(t, err)

require.NoError(t, verifyFunc(ctx, core.NewProposerDuty(slot), pubkey, data))
require.NoError(t, verifyFunc(ctx, "", core.NewProposerDuty(slot), pubkey, data))
})

t.Run("Verify blinded proposal", func(t *testing.T) {
Expand All @@ -204,7 +204,7 @@ func TestParSigExVerifier(t *testing.T) {
data, err := core.NewPartialVersionedSignedBlindedProposal(&eth2apiBlinded, shareIdx)
require.NoError(t, err)

require.NoError(t, verifyFunc(ctx, core.NewProposerDuty(slot), pubkey, data))
require.NoError(t, verifyFunc(ctx, "", core.NewProposerDuty(slot), pubkey, data))
})

t.Run("Verify Randao", func(t *testing.T) {
Expand All @@ -216,7 +216,7 @@ func TestParSigExVerifier(t *testing.T) {

randao := core.NewPartialSignedRandao(epoch, sign(sigData[:]), shareIdx)

require.NoError(t, verifyFunc(ctx, core.NewRandaoDuty(slot), pubkey, randao))
require.NoError(t, verifyFunc(ctx, "", core.NewRandaoDuty(slot), pubkey, randao))
})

t.Run("Verify Voluntary Exit", func(t *testing.T) {
Expand All @@ -232,7 +232,7 @@ func TestParSigExVerifier(t *testing.T) {

require.NoError(t, err)

require.NoError(t, verifyFunc(ctx, core.NewVoluntaryExit(slot), pubkey, data))
require.NoError(t, verifyFunc(ctx, "", core.NewVoluntaryExit(slot), pubkey, data))
})

t.Run("Verify validator registration", func(t *testing.T) {
Expand All @@ -249,7 +249,7 @@ func TestParSigExVerifier(t *testing.T) {
data, err := core.NewPartialVersionedSignedValidatorRegistration(&reg.VersionedSignedValidatorRegistration, shareIdx)
require.NoError(t, err)

require.NoError(t, verifyFunc(ctx, core.NewBuilderRegistrationDuty(slot), pubkey, data))
require.NoError(t, verifyFunc(ctx, "", core.NewBuilderRegistrationDuty(slot), pubkey, data))
})

t.Run("Verify beacon committee selection", func(t *testing.T) {
Expand All @@ -263,7 +263,7 @@ func TestParSigExVerifier(t *testing.T) {
selection.SelectionProof = sign(sigData[:])
data := core.NewPartialSignedBeaconCommitteeSelection(selection, shareIdx)

require.NoError(t, verifyFunc(ctx, core.NewPrepareAggregatorDuty(slot), pubkey, data))
require.NoError(t, verifyFunc(ctx, "", core.NewPrepareAggregatorDuty(slot), pubkey, data))
})

t.Run("Verify aggregate and proof", func(t *testing.T) {
Expand All @@ -286,7 +286,7 @@ func TestParSigExVerifier(t *testing.T) {
agg.Deneb.Signature = sign(sigData[:])
data := core.NewPartialVersionedSignedAggregateAndProof(agg, shareIdx)

require.NoError(t, verifyFunc(ctx, core.NewAggregatorDuty(slot), pubkey, data))
require.NoError(t, verifyFunc(ctx, "", core.NewAggregatorDuty(slot), pubkey, data))
})

t.Run("verify sync committee message", func(t *testing.T) {
Expand All @@ -299,11 +299,11 @@ func TestParSigExVerifier(t *testing.T) {
msg.Signature = sign(sigData[:])

data := core.NewPartialSignedSyncMessage(msg, shareIdx)
require.NoError(t, verifyFunc(ctx, core.NewSyncMessageDuty(slot), pubkey, data))
require.NoError(t, verifyFunc(ctx, "", core.NewSyncMessageDuty(slot), pubkey, data))

// Invalid sync committee message.
data = core.NewPartialSignedRandao(epoch, testutil.RandomEth2Signature(), shareIdx)
err = verifyFunc(ctx, core.NewSyncMessageDuty(slot), pubkey, data)
err = verifyFunc(ctx, "", core.NewSyncMessageDuty(slot), pubkey, data)
require.Error(t, err)
require.ErrorContains(t, err, "invalid signature")
})
Expand All @@ -326,7 +326,7 @@ func TestParSigExVerifier(t *testing.T) {

parSigData := core.NewPartialSignedSyncCommitteeSelection(selection, shareIdx)

require.NoError(t, verifyFunc(ctx, core.NewPrepareSyncContributionDuty(slot), pubkey, parSigData))
require.NoError(t, verifyFunc(ctx, "", core.NewPrepareSyncContributionDuty(slot), pubkey, parSigData))
})

t.Run("verify sync committee contribution and proof", func(t *testing.T) {
Expand All @@ -343,7 +343,7 @@ func TestParSigExVerifier(t *testing.T) {

parSigData := core.NewPartialSignedSyncContributionAndProof(proof, shareIdx)

require.NoError(t, verifyFunc(ctx, core.NewPrepareSyncContributionDuty(slot), pubkey, parSigData))
require.NoError(t, verifyFunc(ctx, "", core.NewPrepareSyncContributionDuty(slot), pubkey, parSigData))
})
}

Expand Down
21 changes: 12 additions & 9 deletions dkg/dkg.go
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Original file line number Diff line number Diff line change
Expand Up @@ -241,24 +241,27 @@ func Run(ctx context.Context, conf Config) (err error) {
return errors.Wrap(err, "get peer IDs")
}

ex := newExchanger(p2pNode, nodeIdx.PeerIdx, peerIDs, []sigType{
sigLock,
sigDepositData,
sigValidatorRegistration,
}, conf.Timeout)

// Register libp2p handlers
peerMap := make(map[peer.ID]cluster.NodeIdx)

for _, p := range peers {
nodeIdx, err := def.NodeIdx(p.ID)
idx, err := def.NodeIdx(p.ID)
if err != nil {
return err
}

peerMap[p.ID] = nodeIdx
peerMap[p.ID] = idx
}

ex, err := newExchanger(p2pNode, nodeIdx.PeerIdx, peerIDs, peerMap, []sigType{
sigLock,
sigDepositData,
sigValidatorRegistration,
}, conf.Timeout)
if err != nil {
return err
}

// Register libp2p handlers
caster := bcast.New(p2pNode, peerIDs, key)

// register bcast callbacks for frostp2p
Expand Down
46 changes: 40 additions & 6 deletions dkg/exchanger.go
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ import (

"github.com/obolnetwork/charon/app/errors"
"github.com/obolnetwork/charon/app/z"
"github.com/obolnetwork/charon/cluster"
"github.com/obolnetwork/charon/core"
"github.com/obolnetwork/charon/core/parsigdb"
"github.com/obolnetwork/charon/core/parsigex"
Expand Down Expand Up @@ -67,10 +68,25 @@ type exchanger struct {
dutyGaterFunc func(duty core.Duty) bool
}

func newExchanger(p2pNode host.Host, peerIdx int, peers []peer.ID, sigTypes []sigType, timeout time.Duration) *exchanger {
// Partial signature roots not known yet, so skip verification in parsigex, rather verify before we aggregate.
noopVerifier := func(context.Context, core.Duty, core.PubKey, core.ParSignedData) error {
return nil
func newExchanger(p2pNode host.Host, peerIdx int, peers []peer.ID, peerMap map[peer.ID]cluster.NodeIdx, sigTypes []sigType, timeout time.Duration) (*exchanger, error) {
if peerIdx < 0 || peerIdx >= len(peers) {
return nil, errors.New("peer index out of range", z.Int("peer_idx", peerIdx), z.Int("num_peers", len(peers)))
}

// Every peer must have a valid share index in peerMap, otherwise its partial signatures would be
// rejected as unknown and the exchange would silently time out. Fail fast on a misconfigured map.
for _, p := range peers {
if nodeIdx, ok := peerMap[p]; !ok || nodeIdx.ShareIdx <= 0 {
return nil, errors.New("peer map missing valid share index for peer", z.Str("peer", p.String()))
}
}

// Partial signature roots are not known during the exchange, so cryptographic verification is
// deferred until aggregation. Each received partial signature is still bound to its authenticated
// sender: a peer may only contribute partial signatures under its own assigned share index,
// consistent with the sender check in nodesigs.go.
verifyShareIdx := func(_ context.Context, sender peer.ID, _ core.Duty, _ core.PubKey, data core.ParSignedData) error {
return verifyPeerShareIdx(peerMap, sender, data)
}

st := make(map[sigType]bool)
Expand All @@ -94,7 +110,7 @@ func newExchanger(p2pNode host.Host, peerIdx int, peers []peer.ID, sigTypes []si
ex := &exchanger{
// threshold is len(peers) to wait until we get all the partial sigs from all the peers per DV
sigdb: parsigdb.NewMemDB(len(peers), noopDeadliner{}, parsigdb.NewMemDBMetadata(0, time.Now())), // metadata timestamps are used for metrics, irrelevant for DKG
sigex: parsigex.NewParSigEx(p2pNode, p2p.Send, peerIdx, peers, noopVerifier, dutyGaterFunc, p2p.WithSendTimeout(timeout), p2p.WithReceiveTimeout(timeout)),
sigex: parsigex.NewParSigEx(p2pNode, p2p.Send, peerIdx, peers, verifyShareIdx, dutyGaterFunc, p2p.WithSendTimeout(timeout), p2p.WithReceiveTimeout(timeout)),
sigTypes: st,
sigData: dataByPubkey{
store: sigTypeStore{},
Expand All @@ -108,7 +124,25 @@ func newExchanger(p2pNode host.Host, peerIdx int, peers []peer.ID, sigTypes []si
ex.sigdb.SubscribeThreshold(ex.pushPsigs)
ex.sigex.Subscribe(ex.sigdb.StoreExternal)

return ex
return ex, nil
}

// verifyPeerShareIdx checks that a received partial signature originates from a known peer and uses
// that peer's assigned share index. peerMap maps each participating peer to its node index, so the
// check remains correct when share indices are not contiguous with peer positions (for example when
// operators have been removed and the remaining ones keep their original share indices).
func verifyPeerShareIdx(peerMap map[peer.ID]cluster.NodeIdx, sender peer.ID, data core.ParSignedData) error {
nodeIdx, ok := peerMap[sender]
if !ok {
return errors.New("partial signature from unknown peer", z.Str("peer", sender.String()))
}

if data.ShareIdx <= 0 || data.ShareIdx != nodeIdx.ShareIdx {
return errors.New("partial signature share index does not match sender peer",
z.Str("peer", sender.String()), z.Int("share_idx", data.ShareIdx), z.Int("expected_share_idx", nodeIdx.ShareIdx))
}

return nil
}

// exchange exchanges partial signatures of lockhash/deposit-data among dkg participants and returns all the partial
Expand Down
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