slackware 15 and pam

kikinovak · 01-29-2016, 07:16 AM

Quote:

Originally Posted by Didier Spaier

Could a moderator kindly close this thread?

Stop playing the police, Didier. Slax-Dude raised a perfectly valid point here.

ponce · 01-29-2016, 07:22 AM

sorry Niki, but I think Didier is right: what is the purpose of reviving this thread, just for quotin a three months' old statement?
maybe the discussion should be carried on in one place only.

Slax-Dude · 01-29-2016, 08:17 AM

The other thread is "Solved" and it is going off-topic.
Also, 3 months is not that long.

If it is, kindly ask a moderator to move my post to the more recent thread.

ttk · 01-29-2016, 02:25 PM

Quote:

Originally Posted by Didier Spaier

Could a moderator kindly close this thread?

Please do not. Slax-Dude raises interesting and informing points, and poses a valid question.

philanc · 01-29-2016, 03:51 PM

Quote:

Originally Posted by Slax-Dude

If so, then adding PAM on these terms (no kerberos + default config to flat file auth) would still be of tremendous usefulness.

I think this is an interesting subject that deserves a distinct thread (rather than being drowned here in the usual PAM uproar)

Could this post could be moved in its own thread? ("PAM only, no kerberos") - maybe the simplest would be for Slax-Dude to re-post in a new thread?

volkerdi · 01-29-2016, 04:00 PM

Quote:

Originally Posted by philanc

I think this is an interesting subject that deserves a distinct thread (rather than being drowned here in the usual PAM uproar)

Could this post could be moved in its own thread? ("PAM only, no kerberos") - maybe the simplest would be for Slax-Dude to re-post in a new thread?

Since we will likely never do "PAM only, no Kerberos" there's little use for a thread like that. Better to keep the flamewars in as few threads as possible, IMHO.

philanc · 01-29-2016, 04:33 PM

Quote:

Originally Posted by volkerdi

Since we will likely never do "PAM only, no Kerberos" there's little use for a thread like that. Better to keep the flamewars in as few threads as possible, IMHO.

Well, maybe I was naive, thinking that a distinct thread could be flamewar-free on this subject... but I get your point.

Regarding "we will likely never do "PAM only, no Kerberos"", I am curious about your rationale.

Anyway, this is an interesting clarification about what to expect. Thanks.

bassmadrigal · 01-29-2016, 06:10 PM

Quote:

Originally Posted by philanc

Regarding "we will likely never do "PAM only, no Kerberos"", I am curious about your rationale.

Just a guess, but I'd guess PAM without kerberos would take away too much expected functionality of a PAM system. Just like with adding pulseaudio (making it the default rather than piping all pulseaudio stuff through alsa), if/when they do it, they will probably do it right (as they always do) and get the implementation of PAM that most would expect.

ttk · 01-29-2016, 07:05 PM

Quote:

Originally Posted by bassmadrigal

Just a guess, but I'd guess PAM without kerberos would take away too much expected functionality of a PAM system.

*nod* it would make it useless for my particular use-case, where permission to access servers is expected to be controlled from a central corporate AD server (which typically uses Kerberos authentication).

I completely sympathize with the wariness over krb5's invasiveness, though.

Perhaps there's an alternative, or a way to make krb5 better-encapsulated. Will ponder.

ReaperX7 · 01-29-2016, 11:01 PM

You need kerberosv5 for handshake authentication between server and client especially samba. Unless you want a halfassed server...

philanc · 01-30-2016, 01:28 AM

Quote:

Originally Posted by ttk

*nod* it would make it useless for my particular use-case, where permission to access servers is expected to be controlled from a central corporate AD server (which typically uses Kerberos authentication).

I think this is a pretty common use case.

Let's say Bob is a sysadmin and has to access hundreds of Unix servers via SSH. A good practice is obviously to request that Bob logs into servers as Bob (then su / sudo) for traceability.

Bob is logged on his Windows PC on the AD domain. Bob fires putty and goes to some server. At the login prompt, he enters his name and password (his password in the AD domain - same as the Windows password). On the server, Bob is authenticated by AD, and enters a server session under his identity.

No Kerberos is required for this scenario on the server. PAM (with the standard LDAP auth module) is enough.

Now maybe what we would like to achieve is single sign-on login (SSO): Bob fires putty, goes to the server and is automatically authenticated by AD (no need to enter his password again, his Windows authentication is transparently reused for servers where he is authorized). In that SSO scenario, Kerberos is used in the background (IIRC, putty supports GSSAPI/Kerberos with SSH2)

I believe that the first scenario (LDAP authentication) is quite common and much simpler to implement.

That said, I perfectly understand that

- supporting this sort of environment is not a priority for the Slackware team,

- it may be better for Slackware to either implement all the kit (PAM + Kerberos + deps + pamified/kerberized apps) like all major distros, or else implement nothing, rather than a partial solution.

ivandi · 01-30-2016, 10:07 AM

Quote:

Originally Posted by philanc

I think this is a pretty common use case.

Let's say Bob is a sysadmin and has to access hundreds of Unix servers via SSH. A good practice is obviously to request that Bob logs into servers as Bob (then su / sudo) for traceability.

Bob is logged on his Windows PC on the AD domain. Bob fires putty and goes to some server. At the login prompt, he enters his name and password (his password in the AD domain - same as the Windows password). On the server, Bob is authenticated by AD, and enters a server session under his identity.

No Kerberos is required for this scenario on the server. PAM (with the standard LDAP auth module) is enough.

.
.
.

I believe that the first scenario (LDAP authentication) is quite common and much simpler to implement.

That is not correct.

A Directory consists of:
- LDAP database that replaces /etc/passwd and /etc/group and optionally other flat files.
- Kerberos database and KDC that replace /etc/shadow.

Passwords are managed by Kerberos. On the server you need something like this:

/etc/pam.d/system-auth

Code:

auth		sufficient	pam_winbind.so
auth		required	pam_unix.so		use_first_pass
account		sufficient	pam_winbind.so
account		required	pam_unix.so
session		sufficient	pam_winbind.so
session		required	pam_unix.so
password	sufficient	pam_winbind.so
password	required	pam_unix.so

Samba uses Heimdal internally so it works even if you don't have a system wide Kerberos install.

Quote:

Originally Posted by philanc

Now maybe what we would like to achieve is single sign-on login (SSO): Bob fires putty, goes to the server and is automatically authenticated by AD (no need to enter his password again, his Windows authentication is transparently reused for servers where he is authorized). In that SSO scenario, Kerberos is used in the background (IIRC, putty supports GSSAPI/Kerberos with SSH2)

Yes. You need a system wide install for all other software to be Kerberos aware. Also do not forget NFSv4.

Quote:

Originally Posted by philanc

That said, I perfectly understand that
- supporting this sort of environment is not a priority for the Slackware team,
- it may be better for Slackware to either implement all the kit (PAM + Kerberos + deps + pamified/kerberized apps) like all major distros, or else implement nothing, rather than a partial solution.

Actually the implementation of PAM+Kerberos needs less additional packages than PulseAudio. And most of the work has already been done outside the distribution.

Cheers

philanc · 01-30-2016, 11:59 AM

Quote:

Originally Posted by ivandi

That is not correct.

A Directory consists of:
- LDAP database that replaces /etc/passwd and /etc/group and optionally other flat files.
- Kerberos database and KDC that replace /etc/shadow.

AD supports several authentication methods:
- kerberos (the most well known these days)
- NTLMv2
- other methods (including the less secure NTLM, digest, down to plain text password)

NTLMv2 over ldaps is a perfectly valid and secure method involving no Kerberos ticket at all (--just a salted and hashed password). It is simple, works with the Windows password for Windows clients, and requires very few components on the target server.

On the other hand, Kerberos is the preferred solution for several reasons:

Technically, it is a solid, secure, proven solution. It provides a good single sign-on solution for users -- once I am logged into my PC, I can access other servers and I am transparently authenticated (no password entry required).

More importantly, it is the de facto standard in corporate environments, because of Microsoft prevalence, but also because it has been adopted and is supported by the majors Linux distros (redhat, suse, debian, ubuntu) in corporate IT.

It means that when you google for "Linux AD authentication", most of what you get is Kerberos-based auth.

For this non-technical reason only, I think that the Slackware team "PAM+Kerberos or nothing" approach is the wise one.

HTH

Phil

unSpawn · 02-02-2016, 12:12 PM

While it indeed is doubtful reviving this thread will be decisive in any way I notice post #299 was marked 5 times while post #300 was marked "helpful" 1 time. So apparently this thread still serves some purpose. I do caution the next posters to first read and understand the whole thread before contributing though: rehashing serves no purpose at all.

linux91 · 05-19-2020, 12:20 PM

Looking for current guidance on the topic of PAM and Slackware, this thread surfaced.

Found the answer in the Changelog for Slackware64-Current.
ref: ftp://ftp.osuosl.org/pub/slackware/s.../ChangeLog.txt
"Fri May 15 07:28:15 UTC 2020
Hey folks, just a heads-up that PAM is about to be merged into the main tree.
We can't have it blocking other upgrades any longer. The config files could be
improved (adding support for pam_krb5 and pam_ldap, for example), but they'll
do for now. Have a good weekend, and enjoy these updates! :-)"