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accounts/abi: Negative numbers not properly converted in ABI encoding

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When converting a negative number e.g., -2, the resulting ABI encoding
should look as follows:
fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffe.
However, since the check of the type is for an uint instead of an
int, it results in the following ABI encoding:
0101010101010101010101010101010101010101010101010101010101010102. The
Ethereum ABI
(https://github.com/ethereum/wiki/wiki/Ethereum-Contract-ABI) says,
that signed integers are stored in two's complement which should be
of the form ffffff.... and not 01010101..... for e.g. -1. Thus, I
removed the type check in numbers.go as well as the function S256
as I don't think they are correct. Or maybe I'm missing something?
This commit is contained in:
Thomas Bocek 2016-06-02 18:43:27 +02:00
parent 16a23ff740
commit 89c6c5bb85
4 changed files with 10 additions and 64 deletions
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2
accounts/abi/method.go
View File

@ -62,7 +62,7 @@ func (m Method) pack(method Method, args ...interface{}) ([]byte, error) {
// calculate the offset
offset := len(method.Inputs)*32 + len(variableInput)
// set the offset
ret = append(ret, packNum(reflect.ValueOf(offset), UintTy)...)
ret = append(ret, packNum(reflect.ValueOf(offset))...)
// Append the packed output to the variable input. The variable input
// will be appended at the end of the input.
variableInput = append(variableInput, packed...)

36
accounts/abi/numbers.go
View File

@ -61,54 +61,20 @@ func U256(n *big.Int) []byte {
return common.LeftPadBytes(common.U256(n).Bytes(), 32)
}
func S256(n *big.Int) []byte {
sint := common.S256(n)
ret := common.LeftPadBytes(sint.Bytes(), 32)
if sint.Cmp(common.Big0) < 0 {
for i, b := range ret {
if b == 0 {
ret[i] = 1
continue
}
break
}
}
return ret
}
// S256 will ensure signed 256bit on big nums
func U2U256(n uint64) []byte {
return U256(big.NewInt(int64(n)))
}
func S2S256(n int64) []byte {
return S256(big.NewInt(n))
}
// packNum packs the given number (using the reflect value) and will cast it to appropriate number representation
func packNum(value reflect.Value, to byte) []byte {
func packNum(value reflect.Value) []byte {
switch kind := value.Kind(); kind {
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
if to == UintTy {
return U2U256(value.Uint())
} else {
return S2S256(int64(value.Uint()))
}
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
if to == UintTy {
return U2U256(uint64(value.Int()))
} else {
return S2S256(value.Int())
}
case reflect.Ptr:
// This only takes care of packing and casting. No type checking is done here. It should be done prior to using this function.
if to == UintTy {
return U256(value.Interface().(*big.Int))
} else {
return S256(value.Interface().(*big.Int))
}
}
return nil

26
accounts/abi/numbers_test.go
View File

@ -26,48 +26,28 @@ import (
func TestNumberTypes(t *testing.T) {
ubytes := make([]byte, 32)
ubytes[31] = 1
sbytesmin := []byte{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
unsigned := U256(big.NewInt(1))
if !bytes.Equal(unsigned, ubytes) {
t.Errorf("expected %x got %x", ubytes, unsigned)
}
signed := S256(big.NewInt(1))
if !bytes.Equal(signed, ubytes) {
t.Errorf("expected %x got %x", ubytes, unsigned)
}
signed = S256(big.NewInt(-1))
if !bytes.Equal(signed, sbytesmin) {
t.Errorf("expected %x got %x", ubytes, unsigned)
}
}
func TestPackNumber(t *testing.T) {
ubytes := make([]byte, 32)
ubytes[31] = 1
sbytesmin := []byte{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}
maxunsigned := []byte{255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255}
packed := packNum(reflect.ValueOf(1), IntTy)
packed := packNum(reflect.ValueOf(1))
if !bytes.Equal(packed, ubytes) {
t.Errorf("expected %x got %x", ubytes, packed)
}
packed = packNum(reflect.ValueOf(-1), IntTy)
if !bytes.Equal(packed, sbytesmin) {
t.Errorf("expected %x got %x", ubytes, packed)
}
packed = packNum(reflect.ValueOf(1), UintTy)
if !bytes.Equal(packed, ubytes) {
t.Errorf("expected %x got %x", ubytes, packed)
}
packed = packNum(reflect.ValueOf(-1), UintTy)
packed = packNum(reflect.ValueOf(-1))
if !bytes.Equal(packed, maxunsigned) {
t.Errorf("expected %x got %x", maxunsigned, packed)
}
packed = packNum(reflect.ValueOf("string"), UintTy)
packed = packNum(reflect.ValueOf("string"))
if packed != nil {
t.Errorf("expected 'string' to pack to nil. got %x instead", packed)
}

4
accounts/abi/packing.go
View File

@ -25,7 +25,7 @@ import (
// packBytesSlice packs the given bytes as [L, V] as the canonical representation
// bytes slice
func packBytesSlice(bytes []byte, l int) []byte {
len := packNum(reflect.ValueOf(l), UintTy)
len := packNum(reflect.ValueOf(l))
return append(len, common.RightPadBytes(bytes, (l+31)/32*32)...)
}
@ -34,7 +34,7 @@ func packBytesSlice(bytes []byte, l int) []byte {
func packElement(t Type, reflectValue reflect.Value) []byte {
switch t.T {
case IntTy, UintTy:
return packNum(reflectValue, t.T)
return packNum(reflectValue)
case StringTy:
return packBytesSlice([]byte(reflectValue.String()), reflectValue.Len())
case AddressTy: