On Mon, 25 Jan 2010, Aurelien Jarno wrote:
On Mon, Jan 25, 2010 at 09:08:08AM -0500, root wrote:
Package: libc6
Version: 2.7-18
Severity: critical
Justification: breaks unrelated software
I'm running Debian Lenny with a stock 2.6.26-2 AMD64 kernel, and after upgrading any of
my systems to use the latest libc6 package from debian-security (2.7-18lenny2), all of my
systems that use NIS can no longer authenticate. All I get is "Authentication
service cannot retrieve authentication info". If I upgrade a system to
2.7-18lenny2, I immediately start having problems, and as soon as I revert back to
2.7-18, everything works perfectly. I've been using the same NIS setup for close to 5
years now, and have been moving it along from Sarge, to Etch, to Lenny without any
problems...until now.
I am sorry about that. This security update was there to prevent leaking
adjunct passwords to normal users.
My /etc/nsswitch.conf:
passwd: compat
group: compat
shadow: compat
Like I said, I am using NIS, however both the NIS master server and the NIS
clients both break when I upgrade libc6 to 2.7-18lenny2. The NIS server is
again, a stock Debian Lenny server. With the NIS server, I am combining the
passwd/shadow files on the NIS server into just the passwd map (using the
MERGE_PASSWD option). So the NIS clients don't actually see any shadow file
entries for any of the NIS accounts.
Ok, so users were able to login even if there was no shadow entry.
I've also tried changing the nsswitch.conf file to:
passwd: nis files
group: nis files
shadow: files
You'll notice I left the "nis" option off of the shadow entry, since there's no need for
it, since there's no "shadow" map. My guess is that, this is the cause of the
problem...In other words, because the system isn't seeing shadow entries, it's bailing out. But
why all of a sudden did this break in the latest libc6? And is there a way to get the old
functionality back?
What the changes did is to stop merging adjunct passwords to the passwd
database, and merge them in the shadow database instead. There is no new
requirement for shadow entries.
If you are not using adjunct password, no changes should have happened
for you. As it doesn't work, it seems something has broken, we have to
understand why. FYI, I have just done a NIS setup using the MERGE_PASSWD
option, and only compat entries into /etc/nsswitch.conf, and I don't see
this problem.
I will need more informations to debug this:
- Are you using adjunct passwords in addition to merged passwords?
No.
- As I understand, you have upgraded libc6 on both the NIS server and
the clients. Can you please try to see if it also breaks if you
upgrade only the clients?
Yes it still breaks, when I upgrade just one of the clients.
- Are you using nscd on the clients?
No.
- What the result of "getent passwd a_nis_user" on a client when running
as a standard (local) user, a root user, for both
Very interesting... Whether I run the "getent" command as root or a
normal user, I get the following:
On the libc6 (2.7-18) system:
username:encrypted_passwd_here:123456:654321:MyName:/my/home/directory:/bin/tcsh
On the libc6 (2.7-18lenny2) system:
username:x:123456:654321:MyName:/my/home/directory:/bin/tcsh
That does seem to be what is causing my problems...
- Do you have more info the client system logs?
Not really, the only thing I see is just:
Jan 27 06:53:45 hostname su[31991]: pam_authenticate: Authentication service
cannot retrieve authentication info
Jan 27 06:53:45 hostname su[31991]: FAILED su for testuser2 by testuser1
Jan 27 06:53:45 hostname su[31991]: - pts/1 testuser1:testuser2
If you know of any way of getting more debug info from PAM, let me know
and I'll run more tests.
By the way, thank you for your help, I really appreciate it!
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurel...@aurel32.net http://www.aurel32.net
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