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proto: fix uint64->int overflow in table unmarshal #461

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merged 3 commits into from
Nov 29, 2017
Merged

proto: fix uint64->int overflow in table unmarshal #461

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a2fb0a9
proto: fix uint64->int overflow in table unmarshal
neild Nov 29, 2017
cddfb72
avoid overflow on addition, as well as uint64->int conversion
neild Nov 29, 2017
acfffe7
Merge branch 'fuzz' of github.com:neild/protobuf into fuzz
neild Nov 29, 2017
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10 changes: 9 additions & 1 deletion proto/all_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1306,7 +1306,7 @@ func (*NNIMessage) Reset() {}
func (*NNIMessage) String() string { return "" }
func (*NNIMessage) ProtoMessage() {}

type NMMessage struct {}
type NMMessage struct{}

func (*NMMessage) Reset() {}
func (*NMMessage) String() string { return "" }
Expand Down Expand Up @@ -1505,6 +1505,14 @@ func TestVarintOverflow(t *testing.T) {
}
}

func TestBytesWithInvalidLengthInGroup(t *testing.T) {
// Overflowing a 64-bit length should not be allowed.
b := []byte{0xbb, 0x30, 0xb2, 0x30, 0xb0, 0xb2, 0x83, 0xf1, 0xb0, 0xb2, 0xef, 0xbf, 0xbd, 0x01}
if err := Unmarshal(b, new(MyMessage)); err == nil {
t.Fatalf("Overflowed uint64 length without error")
}
}

func TestUnmarshalFuzz(t *testing.T) {
const N = 1000
seed := time.Now().UnixNano()
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2 changes: 1 addition & 1 deletion proto/table_unmarshal.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1849,7 +1849,7 @@ func findEndGroup(b []byte) (int, int) {
return -1, -1
}
i += k
if i+int(m) > len(b) {
if uint64(len(b)) < uint64(i)+m {
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@dsnet dsnet Nov 29, 2017 •
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Can't this still overflow with malicious values of m? E.g., if m was set to math.MaxUint64-i+1, then this check will never trigger.

Since, we know that i ≤ len(b), wouldn't a more safe check be: uint64(len(b)-i) < m since the LHS is guaranteed to be a positive value?

Similarly, we should also protect the WireFixed32 and WireFixed64 cases to be of this form, although it is far less likely those can be exploited.

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The i+m operation can wrap, although the harm is limited to misinterpreting the contents of the buffer--it can't panic, because we've ensured that the wrapped i+m is within the bounds of b.

Rewrote it anyway to be more correct. Fixed one other existing case where this could wrap at the same time.

return -1, -1
}
i += int(m)
Expand Down