Mailinglist Archive: yast-devel (34 mails)

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Re: [yast-devel] Webyast and rpam
  • From: Ralf Haferkamp <rhafer@xxxxxxx>
  • Date: Tue, 29 Jun 2010 12:18:14 +0200
  • Message-id: <201006291218.15148.rhafer@xxxxxxx>
Am Montag 21 Juni 2010, 14:00:28 schrieb Josef Reidinger:
Hi,
because of new feature to support more authentication backend I look
more closer how we currently authenticate. Result is that it works
only for /etc/passwd. So I try to research how work interesting world
of pam and look again how works rpam which we used in past. Rpam
doesn't work for our appliance in previous result, because it cannot
read /etc/shadow. Only way how to avoid it is to set suid, which is
not acceptable.
There is probably another possibility: "sssd". SSSD is a daemon that can
be configured to act a proxy for pam authentication. In your case you
could set up that system so that rpam would use pam_sss for
authentication and forward the request to pam_unix2 (or whatever other
PAM modules you want to use). sssd is running as root so it will have
access to /etc/shadow. sssd has also some other nice features like
caching and offline authentication. Additionally it offers native
backends for doing LDAP and Kerberos (i.e. for LDAP and Kerberos you
won't configure in proxy mode but use the native sssd backends through
pam_sss). There of course other pam modules for which you wouldn't need
to use sssd. E.g. when using winbind to authenticate against Active
Directory.

There are of course some drawbacks of sssd:
- we don't ship it with SLES11-SP1, we will have it in 11.3 though. And
I'd also like to see it in SLES11-SP2 (this hasn't be decided yet)
- the "proxy" mode does only support very simple setups. For more complex
PAM setups it won't be every userfriendly WRT to error handling IIRC.

So we use just unix2_chkpwd which is part of
pam_modules to allow pam to solve same problem as we have. So now we
use just unix2_chkpwd for result which of course doesn't work for
other authenticate backends. But for this purpose works good rpam as
pam can read from ldap, edir etc... Easy way how to solve it is to
revert patch which remove rpam usage, but I don't like much that we
must handle it. I think that it could be nice if rpam if detect that
if cannot read /etc/shadow then use unix2_chkpwd itself instead our
code.
How would you want to detect that? You'd need to put knowledge into rpam
which it shouldn't have (e.g. by trying to access /etc/shadow or reading
the pam-configuration). I don't think that would be a good idea.

What do you think about it? If you agree I plan to write patch
for rpam which do it and try to push it to upstream ( we really must
more pushing our fixes to upstream as shown workshop ) Josef


--
Ralf
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