enforce <1/3 validator updates

Refs #950

consensus/reactor_test.go

@@ -194,8 +194,8 @@ func TestReactorVotingPowerChange(t *testing.T) {
 }
 
 func TestReactorValidatorSetChanges(t *testing.T) {
-	nPeers := 7
-	nVals := 4
+	nPeers := 9
+	nVals := 6
 	css := randConsensusNetWithPeers(nVals, nPeers, "consensus_val_set_changes_test", newMockTickerFunc(true), newPersistentDummy)
 
 	logger := log.TestingLogger()

docs/app-development.rst

@@ -403,14 +403,16 @@ pick up from when it restarts. See information on the Handshake, below.
 EndBlock
 ^^^^^^^^
 
-The EndBlock request can be used to run some code at the end of every
-block. Additionally, the response may contain a list of validators,
-which can be used to update the validator set. To add a new validator or
-update an existing one, simply include them in the list returned in the
-EndBlock response. To remove one, include it in the list with a
-``power`` equal to ``0``. Tendermint core will take care of updating the
-validator set. Note validator set changes are only available in v0.8.0
-and up.
+The EndBlock request can be used to run some code at the end of every block.
+Additionally, the response may contain a list of validators, which can be used
+to update the validator set. To add a new validator or update an existing one,
+simply include them in the list returned in the EndBlock response. To remove
+one, include it in the list with a ``power`` equal to ``0``. Tendermint core
+will take care of updating the validator set. Note you can not update more than
+1/3 of validators in one block because this will make it impossible for a light
+client to prove the transition externally. See the `light client docs
+<https://godoc.org/github.com/tendermint/tendermint/lite#hdr-How_We_Track_Validators>`__
+for details on how it tracks validators.
 
 .. container:: toggle
 

docs/specification/light-client-protocol.rst

@@ -5,8 +5,8 @@ Light clients are an important part of the complete blockchain system
 for most applications. Tendermint provides unique speed and security
 properties for light client applications.
 
-See our developing `light-client
-repository <https://github.com/tendermint/light-client>`__.
+See our `lite package
+<https://godoc.org/github.com/tendermint/tendermint/lite>`__.
 
 Overview
 --------

state/execution.go

@@ -10,7 +10,6 @@ import (
 	crypto "github.com/tendermint/go-crypto"
 	"github.com/tendermint/tendermint/proxy"
 	"github.com/tendermint/tendermint/types"
-	cmn "github.com/tendermint/tmlibs/common"
 	"github.com/tendermint/tmlibs/log"
 )
 
@@ -112,9 +111,9 @@ func execBlockOnProxyApp(txEventPublisher types.TxEventPublisher, proxyAppConn p
 		return nil, err
 	}
 
-	valUpdates := abciResponses.EndBlock.ValidatorUpdates
-
 	logger.Info("Executed block", "height", block.Height, "validTxs", validTxs, "invalidTxs", invalidTxs)
+
+	valUpdates := abciResponses.EndBlock.ValidatorUpdates
 	if len(valUpdates) > 0 {
 		logger.Info("Updates to validators", "updates", abci.ValidatorsString(valUpdates))
 	}
@@ -122,10 +121,22 @@ func execBlockOnProxyApp(txEventPublisher types.TxEventPublisher, proxyAppConn p
 	return abciResponses, nil
 }
 
-func updateValidators(validators *types.ValidatorSet, changedValidators []*abci.Validator) error {
-	// TODO: prevent change of 1/3+ at once
+func updateValidators(currentSet *types.ValidatorSet, updates []*abci.Validator) error {
+	// ## prevent update of 1/3+ at once
+	//
+	// If more than 1/3 validators changed in one block, then a light
+	// client could never prove the transition externally. See
+	// ./lite/doc.go for details on how a light client tracks
+	// validators.
+	maxUpdates := currentSet.Size() / 3
+	if maxUpdates == 0 { // if current set size is less than 3
+		maxUpdates = 1
+	}
+	if len(updates) > maxUpdates {
+		return errors.New("Can not update more than 1/3 of validators at once")
+	}
 
-	for _, v := range changedValidators {
+	for _, v := range updates {
 		pubkey, err := crypto.PubKeyFromBytes(v.PubKey) // NOTE: expects go-wire encoded pubkey
 		if err != nil {
 			return err
@@ -135,28 +146,28 @@ func updateValidators(validators *types.ValidatorSet, changedValidators []*abci.
 		power := int64(v.Power)
 		// mind the overflow from int64
 		if power < 0 {
-			return errors.New(cmn.Fmt("Power (%d) overflows int64", v.Power))
+			return fmt.Errorf("Power (%d) overflows int64", v.Power)
 		}
 
-		_, val := validators.GetByAddress(address)
+		_, val := currentSet.GetByAddress(address)
 		if val == nil {
 			// add val
-			added := validators.Add(types.NewValidator(pubkey, power))
+			added := currentSet.Add(types.NewValidator(pubkey, power))
 			if !added {
-				return errors.New(cmn.Fmt("Failed to add new validator %X with voting power %d", address, power))
+				return fmt.Errorf("Failed to add new validator %X with voting power %d", address, power)
 			}
 		} else if v.Power == 0 {
 			// remove val
-			_, removed := validators.Remove(address)
+			_, removed := currentSet.Remove(address)
 			if !removed {
-				return errors.New(cmn.Fmt("Failed to remove validator %X)"))
+				return fmt.Errorf("Failed to remove validator %X", address)
 			}
 		} else {
 			// update val
 			val.VotingPower = power
-			updated := validators.Update(val)
+			updated := currentSet.Update(val)
 			if !updated {
-				return errors.New(cmn.Fmt("Failed to update validator %X with voting power %d", address, power))
+				return fmt.Errorf("Failed to update validator %X with voting power %d", address, power)
 			}
 		}
 	}
@@ -243,8 +254,8 @@ func (s *State) validateBlock(b *types.Block) error {
 		}
 	} else {
 		if len(b.LastCommit.Precommits) != s.LastValidators.Size() {
-			return errors.New(cmn.Fmt("Invalid block commit size. Expected %v, got %v",
-				s.LastValidators.Size(), len(b.LastCommit.Precommits)))
+			return fmt.Errorf("Invalid block commit size. Expected %v, got %v",
+				s.LastValidators.Size(), len(b.LastCommit.Precommits))
 		}
 		err := s.LastValidators.VerifyCommit(
 			s.ChainID, s.LastBlockID, b.Height-1, b.LastCommit)

state/state_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	abci "github.com/tendermint/abci/types"
 
@@ -130,81 +131,56 @@ func TestValidatorSimpleSaveLoad(t *testing.T) {
 	assert.IsType(ErrNoValSetForHeight{}, err, "expected err at unknown height")
 }
 
-// TestValidatorChangesSaveLoad tests saving and loading a validator set with changes.
+// TestValidatorChangesSaveLoad tests saving and loading a validator set with
+// changes.
 func TestValidatorChangesSaveLoad(t *testing.T) {
+	const valSetSize = 6
 	tearDown, _, state := setupTestCase(t)
+	state.Validators = genValSet(valSetSize)
+	state.Save()
 	defer tearDown(t)
-	// nolint: vetshadow
-	assert := assert.New(t)
 
-	// change vals at these heights
-	changeHeights := []int64{1, 2, 4, 5, 10, 15, 16, 17, 20}
-	N := len(changeHeights)
+	const height = 1
+	pubkey := crypto.GenPrivKeyEd25519().PubKey()
+	// swap the first validator with a new one ^^^ (validator set size stays the same)
+	header, parts, responses := makeHeaderPartsResponses(state, height, pubkey)
+	err := state.SetBlockAndValidators(header, parts, responses)
+	require.Nil(t, err)
+	state.saveValidatorsInfo()
 
-	// each valset is just one validator.
-	// create list of them
-	pubkeys := make([]crypto.PubKey, N+1)
-	_, val := state.Validators.GetByIndex(0)
-	pubkeys[0] = val.PubKey
-	for i := 1; i < N+1; i++ {
-		pubkeys[i] = crypto.GenPrivKeyEd25519().PubKey()
-	}
+	v, err := state.LoadValidators(height + 1)
+	assert.Nil(t, err)
+	assert.Equal(t, valSetSize, v.Size())
 
-	// build the validator history by running SetBlockAndValidators
-	// with the right validator set for each height
-	highestHeight := changeHeights[N-1] + 5
-	changeIndex := 0
-	pubkey := pubkeys[changeIndex]
-	for i := int64(1); i < highestHeight; i++ {
-		// when we get to a change height,
-		// use the next pubkey
-		if changeIndex < len(changeHeights) && i == changeHeights[changeIndex] {
-			changeIndex++
-			pubkey = pubkeys[changeIndex]
-		}
-		header, parts, responses := makeHeaderPartsResponses(state, i, pubkey)
-		state.SetBlockAndValidators(header, parts, responses)
-		state.saveValidatorsInfo()
-	}
-
-	// make all the test cases by using the same validator until after the change
-	testCases := make([]valChangeTestCase, highestHeight)
-	changeIndex = 0
-	pubkey = pubkeys[changeIndex]
-	for i := int64(1); i < highestHeight+1; i++ {
-		// we we get to the height after a change height
-		// use the next pubkey (note our counter starts at 0 this time)
-		if changeIndex < len(changeHeights) && i == changeHeights[changeIndex]+1 {
-			changeIndex++
-			pubkey = pubkeys[changeIndex]
-		}
-		testCases[i-1] = valChangeTestCase{i, pubkey}
+	index, val := v.GetByAddress(pubkey.Address())
+	assert.NotNil(t, val)
+	if index < 0 {
+		t.Fatal("expected to find newly added validator")
 	}
+}
 
-	for _, testCase := range testCases {
-		v, err := state.LoadValidators(testCase.height)
-		assert.Nil(err, fmt.Sprintf("expected no err at height %d", testCase.height))
-		assert.Equal(v.Size(), 1, "validator set size is greater than 1: %d", v.Size())
-		addr, _ := v.GetByIndex(0)
-
-		assert.Equal(addr, testCase.vals.Address(), fmt.Sprintf(`unexpected pubkey at
-                height %d`, testCase.height))
+func genValSet(size int) *types.ValidatorSet {
+	vals := make([]*types.Validator, size)
+	for i := 0; i < size; i++ {
+		vals[i] = types.NewValidator(crypto.GenPrivKeyEd25519().PubKey(), 10)
 	}
+	return types.NewValidatorSet(vals)
 }
 
-// TestConsensusParamsChangesSaveLoad tests saving and loading consensus params with changes.
+// TestConsensusParamsChangesSaveLoad tests saving and loading consensus params
+// with changes.
 func TestConsensusParamsChangesSaveLoad(t *testing.T) {
 	tearDown, _, state := setupTestCase(t)
+	const valSetSize = 20
+	state.Validators = genValSet(valSetSize)
+	state.Save()
 	defer tearDown(t)
-	// nolint: vetshadow
-	assert := assert.New(t)
 
 	// change vals at these heights
 	changeHeights := []int64{1, 2, 4, 5, 10, 15, 16, 17, 20}
 	N := len(changeHeights)
 
-	// each valset is just one validator.
-	// create list of them
+	// create list of new vals
 	params := make([]types.ConsensusParams, N+1)
 	params[0] = state.ConsensusParams
 	for i := 1; i < N+1; i++ {
@@ -225,7 +201,8 @@ func TestConsensusParamsChangesSaveLoad(t *testing.T) {
 			cp = params[changeIndex]
 		}
 		header, parts, responses := makeHeaderPartsResponsesParams(state, i, cp)
-		state.SetBlockAndValidators(header, parts, responses)
+		err := state.SetBlockAndValidators(header, parts, responses)
+		require.Nil(t, err)
 		state.saveConsensusParamsInfo()
 	}
 
@@ -245,8 +222,8 @@ func TestConsensusParamsChangesSaveLoad(t *testing.T) {
 
 	for _, testCase := range testCases {
 		p, err := state.LoadConsensusParams(testCase.height)
-		assert.Nil(err, fmt.Sprintf("expected no err at height %d", testCase.height))
-		assert.Equal(testCase.params, p, fmt.Sprintf(`unexpected consensus params at
+		assert.Nil(t, err, fmt.Sprintf("expected no err at height %d", testCase.height))
+		assert.Equal(t, testCase.params, p, fmt.Sprintf(`unexpected consensus params at
                 height %d`, testCase.height))
 	}
 }
@@ -270,6 +247,20 @@ func makeParams(blockBytes, blockTx, blockGas, txBytes,
 	}
 }
 
+func TestLessThanOneThirdOfValidatorUpdatesEnforced(t *testing.T) {
+	tearDown, _, state := setupTestCase(t)
+	defer tearDown(t)
+
+	height := state.LastBlockHeight + 1
+	block := makeBlock(state, height)
+	abciResponses := &ABCIResponses{
+		Height:   height,
+		EndBlock: &abci.ResponseEndBlock{ValidatorUpdates: []*abci.Validator{{PubKey: []byte("a"), Power: 10}}},
+	}
+	err := state.SetBlockAndValidators(block.Header, types.PartSetHeader{}, abciResponses)
+	assert.NotNil(t, err, "expected err when trying to update more than 1/3 of validators")
+}
+
 func TestApplyUpdates(t *testing.T) {
 	initParams := makeParams(1, 2, 3, 4, 5, 6)