From dda8b67f3747538bb560508de22aeef8a2153532 Mon Sep 17 00:00:00 2001
From: Anton Kaliaev <anton.kalyaev@gmail.com>
Date: Wed, 4 Jul 2018 12:36:11 +0400
Subject: [PATCH] state: err if 0 power validator is added to the validator set

Closes #1893
---
 state/execution.go      |  6 ++--
 state/execution_test.go | 73 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+), 3 deletions(-)

diff --git a/state/execution.go b/state/execution.go
index 1c0af17a..a36cbfb7 100644
--- a/state/execution.go
+++ b/state/execution.go
@@ -5,10 +5,10 @@ import (
 
 	fail "github.com/ebuchman/fail-test"
 	abci "github.com/tendermint/tendermint/abci/types"
-	"github.com/tendermint/tendermint/proxy"
-	"github.com/tendermint/tendermint/types"
 	dbm "github.com/tendermint/tendermint/libs/db"
 	"github.com/tendermint/tendermint/libs/log"
+	"github.com/tendermint/tendermint/proxy"
+	"github.com/tendermint/tendermint/types"
 )
 
 //-----------------------------------------------------------------------------
@@ -280,7 +280,7 @@ func updateValidators(currentSet *types.ValidatorSet, abciUpdates []abci.Validat
 	for _, valUpdate := range updates {
 		address := valUpdate.Address
 		_, val := currentSet.GetByAddress(address)
-		if val == nil {
+		if val == nil && valUpdate.VotingPower != 0 {
 			// add val
 			added := currentSet.Add(valUpdate)
 			if !added {
diff --git a/state/execution_test.go b/state/execution_test.go
index 9c0635dc..6b8a7e9e 100644
--- a/state/execution_test.go
+++ b/state/execution_test.go
@@ -149,6 +149,79 @@ func TestBeginBlockByzantineValidators(t *testing.T) {
 	}
 }
 
+func TestUpdateValidators(t *testing.T) {
+	pubkey1 := crypto.GenPrivKeyEd25519().PubKey()
+	val1 := types.NewValidator(pubkey1, 10)
+	pubkey2 := crypto.GenPrivKeyEd25519().PubKey()
+	val2 := types.NewValidator(pubkey2, 20)
+
+	testCases := []struct {
+		name string
+
+		currentSet  *types.ValidatorSet
+		abciUpdates []abci.Validator
+
+		resultingSet *types.ValidatorSet
+		shouldErr    bool
+	}{
+		{
+			"adding a validator is OK",
+
+			types.NewValidatorSet([]*types.Validator{val1}),
+			[]abci.Validator{{[]byte{}, types.TM2PB.PubKey(pubkey2), 20}},
+
+			types.NewValidatorSet([]*types.Validator{val1, val2}),
+			false,
+		},
+		{
+			"updating a validator is OK",
+
+			types.NewValidatorSet([]*types.Validator{val1}),
+			[]abci.Validator{{[]byte{}, types.TM2PB.PubKey(pubkey1), 20}},
+
+			types.NewValidatorSet([]*types.Validator{types.NewValidator(pubkey1, 20)}),
+			false,
+		},
+		{
+			"removing a validator is OK",
+
+			types.NewValidatorSet([]*types.Validator{val1, val2}),
+			[]abci.Validator{{[]byte{}, types.TM2PB.PubKey(pubkey2), 0}},
+
+			types.NewValidatorSet([]*types.Validator{val1}),
+			false,
+		},
+
+		{
+			"removing a non-existing validator results in error",
+
+			types.NewValidatorSet([]*types.Validator{val1}),
+			[]abci.Validator{{[]byte{}, types.TM2PB.PubKey(pubkey2), 0}},
+
+			types.NewValidatorSet([]*types.Validator{val1}),
+			true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			err := updateValidators(tc.currentSet, tc.abciUpdates)
+			if tc.shouldErr {
+				assert.Error(t, err)
+			} else {
+				require.Equal(t, tc.resultingSet.Size(), tc.currentSet.Size())
+
+				assert.Equal(t, tc.resultingSet.TotalVotingPower(), tc.currentSet.TotalVotingPower())
+
+				assert.Equal(t, tc.resultingSet.Validators[0].Address, tc.currentSet.Validators[0].Address)
+				if tc.resultingSet.Size() > 1 {
+					assert.Equal(t, tc.resultingSet.Validators[1].Address, tc.currentSet.Validators[1].Address)
+				}
+			}
+		})
+	}
+}
+
 //----------------------------------------------------------------------------
 
 // make some bogus txs