Re: ASN.1 dissector Wireshark

[Vincent Randal <vtrandal () gmail com>]

Thank you. As for the second part I will post as a new separate question in
the morning.

On Mon, Apr 12, 2021 at 11:43 PM Guy Harris <gharris () sonic net> wrote:

> On Apr 12, 2021, at 10:08 PM, Vincent Randal <vtrandal () gmail com> wrote:
>
> > Thank you (John) for delving into a nice description of the overall
> process. I do have a couple more questions for you and the group:
> > 1. What is the meaning of "work is in progress to at least read all ASN1
> specifications" ???
> > I'm trying to imagine what that implies. Does it imply some dissectors
> in ./epan/dissectors/asn1 have an .asn file that is not being read?
>
> No.
>
> It implies that not all of the specifications out there that are in the
> form of text files using ASN.1's descriptive syntax can be handled by
> asn2wrs, so there are some specifications that would need manual tweaking
> to work with asn2wrs.
>
> That may be the case for some of the epan/dissectors/asn1/*/*.asn files.
>
> I don't know what all the limitations are, or whether anybody's
> *currently* working on removing any such limitations.  I don't think
> there's much being done to the specification for the ASN.1 descriptive
> syntax, so I don't think there's much that would be getting more out of
> date; it's more a question of some features in the X.whatever specs that
> isn't supported.
>
> The .cnf file's main purpose is to add additional semantics for fields
> that affects the way Wireshark dissects and displays them, over and above
> what can be expressed in the ASN.1 specification language.  For example, a
> field might be specified, in the specification language, as an OCTET
> STRING, but it might contain a blob of data with substructure *not* using
> the encoding rule for the protocol and thus *not* specifiable in the
> specification.
>
> And, even if it *could* be specified using ASN.1 specification syntax,
> doing so would mean modifying the .asn file, and if the specification is
> updated, and we wanted to update the .asn file to the latest version, we'd
> have to merge the specification changes and our changes.  That's what
> "Changing the ASN1 file is being depreciated as this creates problems when
> updating protocols." means.
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