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Merge pull request #874 from nspcc-dev/disallow-negative-SHL-SHR

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vm: disallow negative shifts for SHL/SHR
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Roman Khimov 2020-04-20 10:30:33 +03:00 committed by GitHub
commit c10c7d2100
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2 changed files with 5 additions and 19 deletions
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16
pkg/vm/vm.go
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@ -53,7 +53,6 @@ const (
MaxStackSize = 2 * 1024
maxSHLArg = MaxBigIntegerSizeBits
minSHLArg = -MaxBigIntegerSizeBits
)
// VM represents the virtual machine.
@ -797,23 +796,14 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
b := v.estack.Pop().BigInt().Int64()
if b == 0 {
return
} else if b < minSHLArg || b > maxSHLArg {
panic(fmt.Sprintf("operand must be between %d and %d", minSHLArg, maxSHLArg))
} else if b < 0 || b > maxSHLArg {
panic(fmt.Sprintf("operand must be between %d and %d", 0, maxSHLArg))
}
a := v.estack.Pop().BigInt()
v.checkBigIntSize(a)
newOp := op
if b < 0 {
b = -b
if op == opcode.SHR {
newOp = opcode.SHL
} else {
newOp = opcode.SHR
}
}
var item big.Int
if newOp == opcode.SHL {
if op == opcode.SHL {
item.Lsh(a, uint(b))
} else {
item.Rsh(a, uint(b))

8
pkg/vm/vm_test.go
View file

@ -884,16 +884,12 @@ func TestArithNegativeArguments(t *testing.T) {
t.Run("SHR", func(t *testing.T) {
t.Run("positive/positive", runCase(opcode.SHR, 5, 2, 1))
t.Run("positive/negative", runCase(opcode.SHR, 5, -2, 20))
t.Run("negative/positive", runCase(opcode.SHR, -5, 2, -2))
t.Run("negative/negative", runCase(opcode.SHR, -5, -2, -20))
})
t.Run("SHL", func(t *testing.T) {
t.Run("positive/positive", runCase(opcode.SHL, 5, 2, 20))
t.Run("positive/negative", runCase(opcode.SHL, 5, -2, 1))
t.Run("negative/positive", runCase(opcode.SHL, -5, 2, -20))
t.Run("negative/negative", runCase(opcode.SHL, -5, -2, -2))
})
}
@ -934,11 +930,11 @@ func TestSHRZero(t *testing.T) {
assert.Equal(t, makeStackItem([]byte{0, 1}), vm.estack.Pop().value)
}
func TestSHRSmallValue(t *testing.T) {
func TestSHRNegative(t *testing.T) {
prog := makeProgram(opcode.SHR)
vm := load(prog)
vm.estack.PushVal(5)
vm.estack.PushVal(minSHLArg - 1)
vm.estack.PushVal(-1)
checkVMFailed(t, vm)
}