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fix overflow-related out-of-bounds panic in decodeBytes() #347

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8 changes: 7 additions & 1 deletion CHANGELOG.md
Original file line number Diff line number Diff line change
@@ -1,10 +1,16 @@
# Changelog

## 0.15.2 (December 14, 2020)

### Bug Fixes

- [\#347](https://github.com/cosmos/iavl/pull/347) Fix another integer overflow in `decodeBytes()` that can cause panics for certain inputs. The `ValueOp` and `AbsenceOp` proof decoders are vulnerable to this via malicious inputs since 0.15.0.

## 0.15.1 (December 13, 2020)

### Bug Fixes

- [\#340](https://github.com/cosmos/iavl/pull/340) Fix integer overflow in `decodeBytes()` that can cause out-of-memory errors on 32-bit machines for certain inputs.
[\#340](https://github.com/cosmos/iavl/pull/340) Fix integer overflow in `decodeBytes()` that can cause panics on 64-bit systems and out-of-memory issues on 32-bit systems. The `ValueOp` and `AbsenceOp` proof decoders are vulnerable to this via malicious inputs. The bug was introduced in 0.15.0.

## 0.15.0 (November 23, 2020)

Expand Down
23 changes: 15 additions & 8 deletions encoding.go
Original file line number Diff line number Diff line change
Expand Up @@ -16,18 +16,25 @@ func decodeBytes(bz []byte) ([]byte, int, error) {
if err != nil {
return nil, n, err
}
// ^uint(0) >> 1 will help determine the max int value variably on 32-bit and 64-bit machines.
if uint64(n)+s >= uint64(^uint(0)>>1) {
return nil, n, fmt.Errorf("invalid out of range length %v decoding []byte", uint64(n)+s)
}
// Make sure size doesn't overflow. ^uint(0) >> 1 will help determine the
// max int value variably on 32-bit and 64-bit machines. We also doublecheck
// that size is positive.
size := int(s)
if len(bz) < n+size {
if s >= uint64(^uint(0)>>1) || size < 0 {
return nil, n, fmt.Errorf("invalid out of range length %v decoding []byte", s)
}
// Make sure end index doesn't overflow. We know n>0 from decodeUvarint().
end := n + size
if end < n {
return nil, n, fmt.Errorf("invalid out of range length %v decoding []byte", size)
}
// Make sure the end index is within bounds.
if len(bz) < end {
return nil, n, fmt.Errorf("insufficient bytes decoding []byte of length %v", size)
}
bz2 := make([]byte, size)
copy(bz2, bz[n:n+size])
n += size
return bz2, n, nil
copy(bz2, bz[n:end])
return bz2, end, nil
}

// decodeUvarint decodes a varint-encoded unsigned integer from a byte slice, returning it and the
Expand Down
88 changes: 88 additions & 0 deletions encoding_test.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,88 @@
package iavl

import (
"encoding/binary"
"math"
"testing"

"github.com/stretchr/testify/require"
)

func TestDecodeBytes(t *testing.T) {
bz := []byte{0, 1, 2, 3, 4, 5, 6, 7}
testcases := map[string]struct {
bz []byte
lengthPrefix uint64
expect []byte
expectErr bool
}{
"full": {bz, 8, bz, false},
"empty": {bz, 0, []byte{}, false},
"partial": {bz, 3, []byte{0, 1, 2}, false},
"out of bounds": {bz, 9, nil, true},
"empty input": {[]byte{}, 0, []byte{}, false},
"empty input out of bounds": {[]byte{}, 1, nil, true},

// The following will always fail, since the byte slice is only 8 bytes,
// but we're making sure they don't panic due to overflow issues. See:
// https://github.com/cosmos/iavl/issues/339
"max int32": {bz, uint64(math.MaxInt32), nil, true},
"max int32 -1": {bz, uint64(math.MaxInt32) - 1, nil, true},
"max int32 -10": {bz, uint64(math.MaxInt32) - 10, nil, true},
"max int32 +1": {bz, uint64(math.MaxInt32) + 1, nil, true},
"max int32 +10": {bz, uint64(math.MaxInt32) + 10, nil, true},

"max int32*2": {bz, uint64(math.MaxInt32) * 2, nil, true},
"max int32*2 -1": {bz, uint64(math.MaxInt32)*2 - 1, nil, true},
"max int32*2 -10": {bz, uint64(math.MaxInt32)*2 - 10, nil, true},
"max int32*2 +1": {bz, uint64(math.MaxInt32)*2 + 1, nil, true},
"max int32*2 +10": {bz, uint64(math.MaxInt32)*2 + 10, nil, true},

"max uint32": {bz, uint64(math.MaxUint32), nil, true},
"max uint32 -1": {bz, uint64(math.MaxUint32) - 1, nil, true},
"max uint32 -10": {bz, uint64(math.MaxUint32) - 10, nil, true},
"max uint32 +1": {bz, uint64(math.MaxUint32) + 1, nil, true},
"max uint32 +10": {bz, uint64(math.MaxUint32) + 10, nil, true},

"max uint32*2": {bz, uint64(math.MaxUint32) * 2, nil, true},
"max uint32*2 -1": {bz, uint64(math.MaxUint32)*2 - 1, nil, true},
"max uint32*2 -10": {bz, uint64(math.MaxUint32)*2 - 10, nil, true},
"max uint32*2 +1": {bz, uint64(math.MaxUint32)*2 + 1, nil, true},
"max uint32*2 +10": {bz, uint64(math.MaxUint32)*2 + 10, nil, true},

"max int64": {bz, uint64(math.MaxInt64), nil, true},
"max int64 -1": {bz, uint64(math.MaxInt64) - 1, nil, true},
"max int64 -10": {bz, uint64(math.MaxInt64) - 10, nil, true},
"max int64 +1": {bz, uint64(math.MaxInt64) + 1, nil, true},
"max int64 +10": {bz, uint64(math.MaxInt64) + 10, nil, true},

"max uint64": {bz, uint64(math.MaxUint64), nil, true},
"max uint64 -1": {bz, uint64(math.MaxUint64) - 1, nil, true},
"max uint64 -10": {bz, uint64(math.MaxUint64) - 10, nil, true},
}
for name, tc := range testcases {
tc := tc
t.Run(name, func(t *testing.T) {
// Generate an input slice.
buf := make([]byte, binary.MaxVarintLen64)
varintBytes := binary.PutUvarint(buf, tc.lengthPrefix)
buf = append(buf[:varintBytes], tc.bz...)

// Attempt to decode it.
b, n, err := decodeBytes(buf)
if tc.expectErr {
require.Error(t, err)
require.Equal(t, varintBytes, n)
} else {
require.NoError(t, err)
require.Equal(t, uint64(n), uint64(varintBytes)+tc.lengthPrefix)
require.Equal(t, tc.bz[:tc.lengthPrefix], b)
}
})
}
}

func TestDecodeBytes_invalidVarint(t *testing.T) {
_, _, err := decodeBytes([]byte{0xff})
require.Error(t, err)
}