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List:       openldap-devel
Subject:    Re: ldap_get_values() called on binary data - does this return an error, or garbage data?
From:       Graham Leggett <minfrin () sharp ! fm>
Date:       2024-04-03 13:08:15
Message-ID: 5284A685-498D-4BCF-A4ED-FE34E0A98148 () sharp ! fm
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On 03 Apr 2024, at 13:03, Ondřej Kuzník <ondra@mistotebe.net> wrote:

> > This has been historically vague - first off, what happens if an
> > attempt is made to call ldap_get_values() on binary data, do you get
> > an error, or garbage data? The source isn't giving me a clear answer.
> 
> Hi Graham,
> in this case binary data means embedded NULs (\0) can be found: given
> that what you get back is a naive char * for each value, you stand to
> lose information about whether that NUL is part of the value or a
> string terminator.

So that means garbage data is returned.

> > Second question is how do you know which of ldap_get_values() or
> > ldap_get_values_len() to call? Obviously you can manually know this,
> > but I'm interested in automated behaviour. What is the canonical way
> > to discover that if you queried a jpegPhoto (for example) that the
> > result would be binary?
> 
> You either expect the data to be a string of some sort (no embedded
> NULs), then you're free to use whichever or you are prepared to accept
> arbitrary bytestreams and you need to use the one that returns bervals.
> That's all there is.

So am I right in understanding there is no way to ask the server "what type is this \
attribute you just gave me, is this arbitrary octets or a NUL terminated string"?

> You're welcome to propose better wording if you can make it clearer to a
> reasonably competent C developer (I'm sure we can assume that they
> understand how strings are laid out etc.)

The reason this matters has nothing to do with reasonably competent C developers, but \
rather options given to end users.

If the end user is allowed to provide an attribute in a configuration file, do I \
force the end user to know about binary values (as is common now), or is there a way \
I can be nice to the end user and have the system behave sensibly based on whether \
the return data is a string or binary?

Regards,
Graham
--


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