Re: [PATCH v2] libebl: recognize FDO Packaging Metadata ELF note

[Luca Boccassi <luca.boccassi@gmail.com>]

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On Tue, 2021-11-30 at 12:25 +0100, Mark Wielaard wrote:
> Hi Luca,
> 
> On Thu, 2021-11-25 at 17:02 +0000, Luca Boccassi via Elfutils-devel
> wrote:
> > +/* Packaging metadata as defined on 
> > > https://systemd.io/COREDUMP_PACKAGE_METADATA/ */
> > > +#define FDO_PACKAGING_METADATA 0xcafe1a7e
> > > +
> > >  /* Note section name of program property.   */
> > >  #define NOTE_GNU_PROPERTY_SECTION_NAME ".note.gnu.property"
> > 
> > I could move this definition to an internal header if the change to
> > elf.h blocks this patch, if you prefer? Let me know.
> 
> It looks like it will be integrated into glibc elf.h later this week.
> I'll resync elf.h then and apply the other half of your patch.
> 
> While looking at how to implement the json parsing of the note data I
> noticed a couple of things that could be clarified in the spec to make
> this more clear and less ambiguous.
> 
> The spec says "a key-value JSON format", "JSON payload" and "a JSON
> string with the structure described below". Which isn't very exact, or
> seems to describe multiple different JSON concepts which aren't exactly
> the same thing. A JSON string is something different from a JSON object
> (which is the only JSON value that has a key-value format). And it
> doesn't really make clear what the encoding of the JSON itself is (it
> cannot be a JSON string, because that itself is expressed in an
> specific character encoding itself).
> 
> What I think the spec should say is something like:
> "The note data is a single JSON object encoded as a zero terminated
> UTF-8 string."
> 
> The spec does explain the requirements for JSON numbers, but doesn't
> mention any for JSON strings or JSON objects. It would be good to also
> explain how to make the strings and objects unambiguous.
> 
> For Objects it should require that all names are unique. See section 4
> in rfc8259.
> 
> For Strings it should require that \uXXXX escaping isn't used and that
> only control characters that have an explicit escape sequence are used
> (\b, \n, \f, \r, \t) [if you allow them in the first place, they are
> probably confusing and it may be good to simply say that Strings should
> not contain any control characters or use \uXXXX escaping]. See section
> 7 and section 8 in rfc8259.
> 
> That should get rid of various corner cases that different parsers are
> known to get wrong. Especially \uXXXX escaping is really confusing when
> using the UTF-8 encoding (and it is totally necessary since UTF-8 can
> express any valid UTF character already).
> 
> Cheers,
> 
> Mark

Thanks, see:

https://github.com/systemd/systemd/pull/21578

-- 
Kind regards,
Luca Boccassi

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