> Gesendet: Montag, 04. August 2014 um 08:22 Uhr
> Von: "Dan Fandrich" <dan_at_coneharvesters.com>
> An: curl-library_at_cool.haxx.se
> Betreff: Re: [PATCH] docs: Update SPNEGO and GSS-API related doc sections
>
> On Sun, Aug 03, 2014 at 11:02:21PM +0200, Michael Osipov wrote:
> > > On Sun, Aug 03, 2014 at 08:53:55PM +0200, Michael Osipov wrote:
> > > > Am 2014-08-03 um 11:27 schrieb Dan Fandrich:
> > > > >On Sun, Aug 03, 2014 at 10:50:21AM +0200, Michael Osipov wrote:
> > > > >>Am 2014-08-03 um 10:27 schrieb Dan Fandrich:
> > > > >>>On Sat, Aug 02, 2014 at 02:18:29PM +0000, Michael Osipov wrote:
> > > > >>>>@@ -180,7 +180,8 @@ FOOTNOTES
> > > > >>>> *1 = requires OpenSSL, GnuTLS, NSS, yassl, axTLS, PolarSSL, WinSSL (native
> > > > >>>> Windows), Secure Transport (native iOS/OS X) or qssl (native IBM i)
> > > > >>>> *2 = requires OpenLDAP
> > > > >>>>- *3 = requires a GSSAPI-compliant library, such as Heimdal or similar
> > > > >>>>+ *3 = requires a GSS-API implementation, such as Heimdal, MIT Kerberos or
> > > > >>>>+ SSPI (native Windows)
> > > > >>>> *4 = requires nghttp2 and possibly a recent TLS library
> > > > >>>> *5 = requires a krb4 library, such as the MIT one or similar
> > > > >>>> *6 = requires c-ares
> > > > >>>
> > > > >>>Minor nit on this one—this implies that SSPI provides a GSS-API implementation.
> > > > >>>This might be slightly clearer:
> > > > >>>
> > > > >>>+ *3 = requires a GSS-API implementation such as Heimdal or MIT Kerberos, or
> > > > >>>+ SSPI (native Windows)
> > > > >>
> > > > >>Infact, SSPI is a proprietary GSS-API implemenation but I do
> > > > >>understand what you are referring to. I have trouble phrasing this in
> > > > >>a unambigious way.
> > >
> > > But if SSPI provides an GSS-API implementation, why doesn't ftp.c use it?
> > > If SSPI provides the same API as as MIT/Heimdal, there would be no reason to
> > > avoid using it there. Where is my understanding going wrong?
> >
> > Your understanding is correct, but you aren't aware of the details. SSPI serves
> > the same purpose as GSS-API but Microsoft did choose a completely different approach
> > in a non-compatible API/ABI when this emerged in Windows 2000. So you always need
> > two code paths and no one did that for FTP. THIS IS Microsoft.
>
> That's what I suspected. So, calling what it does GSS-API is inaccurate as it
> doesn't provide the GSS Application Programming Interface. In my reading on
> this, I discovered that SAP has provided an Open Source GSS-API emulation
> wrapper over SSPI called gsskrb5.dll. It would be interesting to see if this
> is sufficient to enable Kerberos support in ftp on Windows.

I am aware of that wrapper from SAP because this is at our company's SAP core
but I did not know that is actually open source. It is a tremendous amount of
work to bridge both as they have different approaches in conventions. I am try
to bridge this too, SSPI to JGSS. Bumby, very bumpy road ahead.

Where is that library available? I wouldn't pull this into curl, I would rather
create a clean abstraction layer between curl and a framework and use that throughout
libcurl for all protocol, but that is work too :-)
 
> > > > >>Is this better: requires a GSS-API implementation (Unix-like OS) such
> > > > >>as Heimdal or MIT Kerberos, or SSPI (native Windows)
> > > > >>
> > > > >>In general, those who know that SPNEGO is, will know the difference
> > > > >>between GSS-API and SSPI, IMHO.
> > > > >>
> > > > >>How would you rephrase that?
> > > > >
> > > > >I'm no expert on these differences, but I note that the Kerberos code for
> > > > >FTP, IMAP, POP3, SMTP is disabled if SSPI is in use.
> > > >
> > > > Except FTP none of those SASL-aware protocols use any GSS mechanism in curl.
> > >
> > > Ah, I see it now. Those protocols detect a GSS-API request but there's no
> > > actual code to perform it.
> >
> > Yes exactly, the server advertises all supported SASL mechs, e.g., LOGIN
> > GSSAPI, EXTERNAL and you SASL client is free to choose one of them.
> >
> > > > >If SSPI truly provided
> > > > >a GSS-API implementation, then I would expect this GSS-API code to be enabled.
> > > > >As *3 seems to conflate GSS-API and SPNEGO requirements, perhaps it should be
> > > > >split into two line items in the spirit of clarified documentation.
> > > >
> > > > What about:
> > > >
> > > > *3 = requires a GSS-API implementation (Heimdal, MIT Kerberos) or
> > > > SSPI (native Windows)
> > >
> > > This still isn't accurate in the case of FTP, since FTP won't support Kerberos
> > > with SSPI.
> >
> > You are right. I will introduce another footnote for FTP and Kerberos 5 support.
> > Is that acceptable?
>
> That sounds like it would accurately describe the state of support for Kerberos
> in HTTP and FTP.

Preparing a reroll.

Michael

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Received on 2014-08-04