From f0426ac2d52b7f84e5c35882cdf8c171523b1548 Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Thu, 12 Sep 2019 12:02:38 +0300
Subject: [PATCH] vm: do nothing if SHL/SHR by 0

---
 pkg/vm/vm.go      |  6 ++++++
 pkg/vm/vm_test.go | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/pkg/vm/vm.go b/pkg/vm/vm.go
index 74a4057ae..a209a1382 100644
--- a/pkg/vm/vm.go
+++ b/pkg/vm/vm.go
@@ -505,11 +505,17 @@ func (v *VM) execute(ctx *Context, op Instruction) {
 
 	case SHL:
 		b := v.estack.Pop().BigInt()
+		if b.Int64() == 0 {
+			return
+		}
 		a := v.estack.Pop().BigInt()
 		v.estack.PushVal(new(big.Int).Lsh(a, uint(b.Int64())))
 
 	case SHR:
 		b := v.estack.Pop().BigInt()
+		if b.Int64() == 0 {
+			return
+		}
 		a := v.estack.Pop().BigInt()
 		v.estack.PushVal(new(big.Int).Rsh(a, uint(b.Int64())))
 
diff --git a/pkg/vm/vm_test.go b/pkg/vm/vm_test.go
index f75631fb7..87ac78092 100644
--- a/pkg/vm/vm_test.go
+++ b/pkg/vm/vm_test.go
@@ -283,6 +283,50 @@ func TestSub(t *testing.T) {
 	assert.Equal(t, int64(2), vm.estack.Pop().BigInt().Int64())
 }
 
+func TestSHRGood(t *testing.T) {
+	prog := makeProgram(SHR)
+	vm := load(prog)
+	vm.estack.PushVal(4)
+	vm.estack.PushVal(2)
+	vm.Run()
+	assert.Equal(t, false, vm.state.HasFlag(faultState))
+	assert.Equal(t, 1, vm.estack.Len())
+	assert.Equal(t, makeStackItem(1), vm.estack.Pop().value)
+}
+
+func TestSHRZero(t *testing.T) {
+	prog := makeProgram(SHR)
+	vm := load(prog)
+	vm.estack.PushVal([]byte{0, 1})
+	vm.estack.PushVal(0)
+	vm.Run()
+	assert.Equal(t, false, vm.state.HasFlag(faultState))
+	assert.Equal(t, 1, vm.estack.Len())
+	assert.Equal(t, makeStackItem([]byte{0, 1}), vm.estack.Pop().value)
+}
+
+func TestSHLGood(t *testing.T) {
+	prog := makeProgram(SHL)
+	vm := load(prog)
+	vm.estack.PushVal(4)
+	vm.estack.PushVal(2)
+	vm.Run()
+	assert.Equal(t, false, vm.state.HasFlag(faultState))
+	assert.Equal(t, 1, vm.estack.Len())
+	assert.Equal(t, makeStackItem(16), vm.estack.Pop().value)
+}
+
+func TestSHLZero(t *testing.T) {
+	prog := makeProgram(SHL)
+	vm := load(prog)
+	vm.estack.PushVal([]byte{0, 1})
+	vm.estack.PushVal(0)
+	vm.Run()
+	assert.Equal(t, false, vm.state.HasFlag(faultState))
+	assert.Equal(t, 1, vm.estack.Len())
+	assert.Equal(t, makeStackItem([]byte{0, 1}), vm.estack.Pop().value)
+}
+
 func TestLT(t *testing.T) {
 	prog := makeProgram(LT)
 	vm := load(prog)