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LDAP Authentication in Linux
hausmasta writes "HowtoForge has published a walkthrough to show you how to store your users in LDAP and authenticate some of the services against it. It will not show how to install particular packages, as it is distribution/system dependent, instead it will focus on pure configuration of all components needed to have LDAP authentication/storage of users. The howto assumes that you are migrating from a regular passwd/shadow authentication, but it is also suitable for people who do it from scratch."
You could now have several machines authenticating against one machine(although I know there are other ways).
You can also have all your software that is LDAP aware authenticating against the same username/password (assuming they don't already support the stuff like PAM or the like).
If you really want to, you can also setup samba to use it and you can have XP machines join the domain, get the users in the domain all that fun stuff. (Was going to do this in a small lab I help at, ended up not because I realized it wasn't necessary for anything we did down there).
You might have more than one machine to string together, and/or a very large number of users, and/or primary account administration happens somewhere else (like Active Directory, let's say) and account enablement/disablement, password resets, etc., should carry over across both environments.
Put together pam_ldap and pam_krb5 and you can do a lot of nifty stuff. You probably wouldn't care about hardly any of it for a standalone computer, but for a true multiuser system in a multisystem environment... almost anything else is scandalously silly.
For the same reasons as one would use NIS in the past, to allow central control and a single point of administration for your users.
/Anthony Whitehead
With some decent admin tools you can even share your users between variants of Unix and Windows environments.
There are some advantages of LDAP over NIS which are worth mentioning. LDAP can be made more secure than NIS (NIS+ is better in this respect, but oh so much more of a pain to administer) through the use of SSL or better authentication methods. LDAP will usually scale better for many thousands of users than plain NIS. NIS is limited as to what data may be stored for a user, which is ok if all you want your user database for is authentication and basic authorization, but LDAP is much more flexible if you need to store other user information and would rather have a single user store.
There are some sites that even use Unix LDAP clients to authenticate to an Active Directory service running on windows platforms. This can be done much more transparantly with LDAP than many other authentication methods.
http://www.nordicedge.se/
NordicEdge AB
Well not all of us live in our parents basement and have less then 10 systems. Some of use work in enterprise environments with 1000+ servers and would like a central way to manage logins/passwords/auditing. Especially for things like PCI compliance that require it. And no I don't mean PCI as in the system bus interface. I mean payment card industry.
Charles Wyble System Engineer
Really, you need to add kerberos to the mix, especially the heimdall kerberos implementation is attractive, since it allows you to store its settings inside the ldap tree, providing a true centralised secure single signon enviroment.
Using ldap itself is really not much better than using NIS, aside from the fact that it can contain much more than just the user database.
Because if you reject a "taken password", you now know another user's password. You can then use it to login as them.
er because when you reject a taken password, the user has all they need to know to get into somebody else's account!?
Warhammer forums
Ever since I rolled out an LDAPed Samba domain for a customer I was wondering why this is not beeing used for more stuff?
:) Been there...
Its relatively eay to setup and quite stable. This in combination with PAM should be the once and for all way of authentication.
If you have a directory like this you can add virtually everything to it, be it intranet pages, mailserver authentication, hell even an inhouse Jabber client for employees. This should be unified and used much more often.
The management is a blast with the ability to choose whatever LDAP-Frontend you might wanna use and worstcase you can go back to browserbased or console. Its really flexible, elegant and in a Unix style a tool for the job.
Who can enlighten me why this is still rather a niche? are Unixadmins simply too used to the passwd/shadow style auth?
Oh yeah: In case you are going to set it up stay the hell away from BerkeleyDB 4.3.
It can have some nasty surprises.
I use LDAP at work for everything and life is so much better now.
/home/username. Public drives are mapped as well.
Windows Desktops (Samba PDC and BDC -> LDAP)
Linux pam_ldap + nss -> LDAP and NFS shares
You can log into either a windows desktop or linux box and have the same file shares open. Windows has H: and Linux is
Then for email, postfix + dovecot -> ldap. You can store not only use the same username password as for linux, but you can add unlimited number of real-time mail aliases to each user. Also supports virtual domains.
Directory services for phone numbers, room locations, etc. in ldap. Mapped to email clients search/contact lists.
squid + ldap and apache + ldap, secure login to website.
Squirrelmail/horde both use ldap as well. Auth is done via imap, but horde can do much more with ldap. Both can use it for directory services.
Admin can be done either via CLI smbldap-tools, php ldap admin, gq (ldap tree browser), or ldapmodify if you're hard core. Plus with sync'ing data to other sites they have a copy of the data for their BDC/etc. If I need to add/modify a user there is only one place that needs to be modified. And I can do it from home. =)
I figured this was as good time as any to point out our relatively complete Linux LDAP HOWTO, which covers quite a few LDAP servers (MS AD, Novell eDir, OpenLDAP) and the security implications of different setups (eg. using PAM_LDAP vs just using NSS_LDAP). The article lives in a wiki so any improvements are welcome. :-)
I hope you find it useful.
Most of the common maps, including the auto-mount maps have schema and attributes in LDAP. So its just a simple matter of using a migration tool (or doing it by hand) to build your LDAP version of the auto-mount map.
A quick google and here is a link you might like to look at:
http://www.linuxjournal.com/article/6266
There are many other sources of information on this out there.
Anthony Whitehead
NordicEdge AB
https://dpw.threerings.net/projects/splat/ (written by the wonderful people I work with and BSD-licensed) hooks into LDAP, allowing for the storage of public keys for SSH access and other niftiness. We use it for managing passwordless SSH-key based access to the two dozen or so servers here with great success.
The big problem with ldap is that most of autentication plugins (apache, pam and the others) matches only first level group members, not nested groups, normally used, expecially, in big micro$oft directories. This creates a lot of "difficul to mantain" groups containing very big lists of accounts. I know that filters or organizational units can be used to group them, but most of the times this is not enaugh. For this reason i usually prefer radius which integrates well *nix and m$ worlds (even if i still use ldap for apache cause radius mod for apache is not so customizable).
i work for a company that handles large enterprises single sign on and user id consolidation needs... (as well as small/medium ones as well)
you are right on... when it comes to compliance and SOX requirements, getting all of your machines authenticating against one directory (AD or otherwise) makes perfect sense. I am sure there are a few sys admins here who have been asked for login failure and share access permissions across all of their network machines. adding more 'directories' makes it even more fun to gather these reports, comb through logs, look for changes across all the flavors of *nix and then the msft event logs, even network syslog...
There are a few companies out there who have built product lines that allow unix machines to authenticate against AD, their machine accounts can have Windows Group Polices and managed under one single console, they have the ability to appear in SMS as any other machine for reporting and hardware inventory and also to send their performance metrics over to MSFT MOM...
Why in the HELL would anyone want to authenticate against AD? well, it is simple really.. MSFT DID do the LDAP/Kerberos thing right and have been doing it right for a long time. They also have the whole pass-through, single id thing going and it works just fine in AD (when its an all windows network)... and its EVERYWHERE... how many LARGE companies are using whitepages/ldap type directories for authentication and how many are using AD? its a valid question to ask and what is happening is that most ARE already on AD or are moving to AD and they ARE using Exchange and this put AD into a space of being one of the main components of an enterprise. So why not just toss the unix machines in there as well?
yes, it empowers windows AD... but the first solution below (from quest) does not take anything out of the unix guys bag of tricks... in fact it allows for the unix guy to actually do things against AD that before was a pain to setup/admin...
anyway... sunday, should be out walking the dog and playing frisbee with the kids or working on my short game... check out http://www.quest.com/landing/?ID=531 or http://www.centrify.com/ for some good info on two companies that are doing this for the *nix world now...
sig goes here!
This tutorial should have some major security warnings plastered all over and I see nothing to that effect so here's a suppliment.
First, LDAP is NOT an authentication service. I cringe a little whenever someone mentions using "LDAP authentication" for anything other than LDAP clients. Some of these tools use LDAP as a make-shift "pass-through" style authentication service. This is like passing credentials to an SSH server to authenticate web clients (only SSH would be more secure since it enforces confidentiality and integrity).
Second, if you are going to use LDAP like this, make sure the bind is being conducted over SSL. Using SASL would be even better but that's a little harder for a long lived service account and somewhat pointless if you already have Kerberos setup. With a plain bind you're sending passwords in clear text. Do not ever do that or someone will eventually come to your cube asking funny questions.
Finally, using LDAP as an authentication service does not provide Single Sign-On (SSO). You basically have to store some kind of token in the user's HTTP session which means someone could get your session ID and impersonate you (e.g. inadvertantly send a link with a session ID in it).
In general I don't recommend using LDAP as a make-shift authentication service as it is very easy for it to be insecure. Use Kerberos through and through people. It's the correct way to do things, it scales well and it's portable across both UNIX and Microsoft.
I believe I have one of the most advanced LDAP/Kerberos/Samba/Bind "Open Directory" setups. I have two Samba 3 Domain Controllers, both Kerberos and Bind Enabled. with OpenLDAP and MIT Kerberos. I have no need for NFS.
My OpenLDAP stores:
POSIX User Attributes
Samba User Attributes
Radius User Attributes
eGroupware User Attributes (Egroupware accounts.)
DNS Information for our internal DNS Server
DHCP Lease information.
I use Kerberos with ssh-agent to distribute software RPMS for Mandriva Linux to mass distibute RPMs with a single command.
I have Samba Kerberos enabled so that Samba will not repeatedly ask for usernames and passwords, and requires zero configuration.
I have had the code to Egroupware modified so that eGroupware, and Nagios can use Apache's mod_auth_kerb addon to authenticate eGroupware users with a single click instead of a whole second login process.
I'm currently workong on creating a Samba Authenticated gateway with NTLM-SPNEGO support so that kerberos will handle Squid too.
All I need now is for someone to make the modifications nesessary to eGroupware's XMLRPC so that Kontact could use Kerberos and I would have the "Exchange Killer" I always wanted.
All of my users use Samba for network browsing under KDE's Konqueror, with Kerberos and LDAP, it just works.
I consider this my shining accomplishment.
I like to have myself believe that I accomplished "Active Direrctory" under Linux now. I don't use Windows at all in this network, so keep that in mind. The eGroupware people can attest to what a past I am. bugging them to include Kerberos detection in session management. But it all works.
Try changing your root password on 10 different servers on a regular basis.
You aren't thinking of putting your root login under LDAP are you?
Not meaning to be rude, but please, don't be such an idiot.
What happens when the LDAP server falls over and you are at the console and you try to login as root... and it can't authenticate root because the LDAP subsystem is down? Reboot and pray that LDAP starts up ok?
In the free world the media isn't government run; the government is media run.
We switched to ldap authentication on our UNIX systems about a year ago, and basically it rocks. Providing single-sign-on between all of your device of varying operating systems and utility (i.e. servers, routers, switches, terminal/console servers, a lot of applications, and even kvm's) is great when you have a multi-teared support organization, and even if you don't you can still save yourself a lot of useradd / usermod /userdel commands if you centralize.
Why does it rock so much? LDAP seems unique that, unlike almost every other authentication method under the sun (NIS, NIS+ radius) it can be used on a number of devices. Additionally LDAP tends to be a great back-end for other authentication protocols (i.e. radius) can use an LDAP backend.
Practically speaking, often times all someone needs to do is have read access to a device to find out if an interface is up but many system admins give up if they don't have the ability to centralize and allow the company to become altogether too dependent on them. LDAP basically gets rid of this hassle and the administration is minimal. This means that the system admin gets paged less and more people can get work done with better efficiency.
Huh? Surely Kerberos is more complex than plain LDAP authentication?
And a HELL of a lot less secure. You would be better off doing nothing than doing plain LDAP authentication.
And for large insitutions, Kerberos gives you a credential that can be used multiple places. NFS, AFS, websites (with SPEGNO goodness), may services such as SSH, IMAP, etc.
Unless this is for a 192.168 network in your basement, there is NEVER a good reason to do LDAP authenticaion. That is not what it was designed for, and certainly not something it is good at.
Finkployd