Wireshark-dev: Re: [Wireshark-dev] proto_tree_add_item() calls where length doesn't match type
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From: Guy Harris <gharris@xxxxxxxxx>
Date: Fri, 16 Oct 2020 14:43:21 -0700
On Oct 16, 2020, at 2:38 PM, Martin Mathieson via Wireshark-dev <wireshark-dev@xxxxxxxxxxxxx> wrote:

> I made a quick change to have tools/check_typed_proto_items.py to check calls to proto_tree_add_item() - in particular if the length field in the call matches the length implied by the FT_ type.  The fewI've looked at seem to be genuine bugs to me, but if anyone could scan the list and check any dissectors they know well, it'd be good to work out if there are cases/patterns not worth flagging.

Sometimes a given field in a protocol is N bytes in some packets and M bytes in others, where N > M.

In those cases the field will be FT_UINT{N}, and some calls will have shorter lengths.

Having tools/check_typed_proto_items.py handle that would be more complicated, in that it'd have to check all calls before reporting an issue.

Whether any of these instances are cases of that is another matter.