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
aurelien@aurel32.net http://www.aurel32.net