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Re: XSSO? How to communicate to XSSO/PAM external authentication info?

Ingo Luetkebohle wrote:
> S: FTP server ready
> S: 534 Request denied for policy reasons.
> S: 335 ADAT=<base64 stuff>
> C: ADAT morebase64stuff
> S: [loop until security exchange is complete]
> (C is the client, S the server)

So what you are saying is that pre-authentication, there is a protocol
negotiation phase that includes an exchange that will define the
authentication scheme to be used.

You are saying that neither PAM nor GSSAPI nor anything 'generic' is
involved in this negotiation. Could you explain why 'in principle' a PAM
module couldn't handle this sequence? [It looks like some sort of SASL
thing, and I remember previously concluding that PAM could support

> No, it wouldn't. You assume that PAM can select which of the
> mechanisms know to the FTP server is chosen. Well, it can't. It can
> only make *itself* be chosen and then do the rest inside the auth
> loop.

Well, its not exactly pretty, but with a sufficiently cross-referenced
pam.d/XXX file, couldn't you have some sort of:

auth requisite                  pam_negotiate.so "FTP server ready"
auth [default=1 success=IGNORE] pam_switch negotiate_key=GSSAPI
auth requisite                  pam_gss.so
auth [default=1 success=IGNORE] pam_switch negotiate_key=PLAIN
auth requisite                  pam_unix.so
auth requisite                  pam_deny.so

I'm sure there is something I am not understanding about this issue. In
the past, the way protocol negotiations tend to tangle up transport
layer encryption protocol and authentication protocol decisions seems to
be where the above scheme falls on its face. Is this the problem here?



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