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last modified: 2007-05-10 22:29:59
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Note on Debian Sarge:
Please check out Part II: OpenLDAP on Debian Pre-Sarge below
for some information on LDAP with a pre-release version of Debian 3.1, aka "Debian Sarge".
For Debian 3.0 aka Debian Woody:
For Debian 3.1 aka Debian Sarge pre-release version:
Part III was created for miscellaneous comments and addons added after the actual lifetime of this document and which are not exactly bug fixes of existing content:
User Comments:
LDAP is one hell of a tool: it can be used to store any kind of information, starting with
your network's users (which is what we'll do) and not even ending with your favorite
cooking recipes.
As LDAP is one hell of a tool, it is all a pain in the you-know-what-I-mean to get to know it
and to get it up and running. I spent lots of time with basics just to understand it.
One problem for me was, that I didn't find any good documentation on this topic for a long
time.
Anyway, here is first of all a small list of IMHO good documentation on this topic as well
as my stuff to get it working: OpenLDAP (the software written to host the database and do
some other stuff) implements one part of the whole LDAP-specification, AFAICT. We'll use it
to do the major work: host the database. This "LDAP-server" (ldap.subnet.at) will serve
to Linux and Windows workstations hosting the local users and corresponding information.
Later on, it shall also serve the upcoming new Linux-based mailserver.
As Debian GNU/Linux is our distribution of choice, I'll focus on the description for Debian Woody. Nevertheless, lot's of stuff is generic material and you should be able to use it on other distributions too.
I'd like to thank all people I know and those I don't know which made this LDAP solution
possible - just to mention a few groups: Debian, OpenLDAP, Samba, #ldap (irc.debian.org),
the authors of all these Howto's and other documentations, package maintainers, etc. etc. etc.
Thanks!
This document was created during my work as network admin at
subnet - platform for media art and experimental technologies.
This document's home is
http://homex.subnet.at/~max/ldap/.
As Postscript- or PDF-versions of this document have been requested several times:
I created this file's HTML/PHP code directly using vim -- which makes it a bit harder
to create a proper PDF document that's up to date.
(If only I knew that this document became this large -- I'd really spent the time
to learn DocBook first, or had used
LyX -- or whatever.)
Still, Andreas Heinzen pointed out
to me, how to easily create a PDF version of this document
(the latest version is as of June 11, 2005).
Many thanks again to Andreas for his work and feedback on this!
(Just to let you know - in case you want to do this yourself:
Use html2ps and ps2pdf to create the document. Beforehand, the feedback-form
and the counter should be removed from the source code.)
I wouldn't have thought it to be necessary with a HOWTO, but it is: This section is for security issues coming up.
Overview:
The self-compiled Samba packages (DSA-280-1 samba -- buffer overflow)
as well as the self-compiled LDAP packages
(DSA-227-1 openldap2 -- buffer overflows and other bugs)
used in previous versions of this HOWTO unfortunately
are based on vulnerable versions of those packages. If you've simply downloaded and used the packages
from this site, you are strongly encouraged to either recompile them yourself or use the
new upgraded packages provided here.
Description:
For some reason I did not include
"deb-src http://security.debian.org woody/updates main contrib non-free" in my
/etc/apt/sources.list file when initially downloading and compiling
the source packages, this means I used
Woody's original packages which meanwhile turned out to be vulnerable here and there.)
Mind:
As to my knowledge, packages can now be considered "secure" currently. Nevertheless,
Today's security
advisory does not mean I necessarily put possibly needed packages up here in the future as well.
Don't rely on this howto, keep track of security issues yourself!
There is a local root exploit in Samba 2.2.3a-12 that is fixed in Woody's 2.2.3a-13 packages
(check out DSA-463).
04-09-02: Recompiled packages based on the fixed version 2.2.3a-13 are provided below now.
Samba 2.2.3a-13 is vulnerable, see DSA-600.
I removed the compiled packages, please follow the instructions below to build them yourself.
This document is published under the licenses GPL and GFDL (see notes below for details). You may choose, which license to apply.
Copyright © Markus Amersdorfer, subnet.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
A current copy of the license should be available
here.
In case of failure, Version 1.2 of the GNU FDL is also available
locally.
This document may be used under the terms of the GNU General Public License version 2 or higher.
Permission is granted to make and distribute verbatim copies of this
document provided the copyright notice and this permission notice are
preserved on all copies.
Permission is granted to copy and distribute modified versions of this
document under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.
Permission is granted to copy and distribute translations of this document
into another language, under the above conditions for modified versions,
except that this permission notice may be included in translations approved
by the Free Software Foundation instead of in the original English.
This document comes without any warranty and does not claim to be complete, nor does it necessarily hold correct information. The author(s) can not be held reliable for any loss of data or corrupted hardware or any other miscomfort due to information of this document. Use this at your own risk!
If you want to get to know what LDAP is and how its data is organized, please
check out the docs in the following subsection "Learning about LDAP".
I will not go into details, what LDAP really is and how to best design an LDAP tree - at least not for now. There are resources out there which can and do explain this, see section External Resources.
Nevertheless, I'd like to cite from the article
Building an LDAP Server on Linux, Part 1
by Carla Schroder as she points out some IMHO crucial thing concerning the LDAP-world:
"Let's get like all pedantic for a moment (please put on your geek beard
and pocket protector for this). LDAP--Lightweight Directory Access Protocol--is
a protocol, not a database. It accesses a special kind of database that is
optimized for fast reads. Use it for relatively static information, such
as company directories, user data, customer data, passwords, and security keys.
OpenLDAP uses the Sleepycat Berkeley DB. Having said all that, I'm not the pedant
police; I'm OK with calling the whole works a database and being done with it."
First thing to do is to install the OpenLDAP-server.
I'd like to thank the author of the LDAP HOWTO over at
howto.aphroland.de a lot.
This doc helped me a lot by describing the installation from a Debian user's
point of view. Lots of my description (above all to get this "LDAP-thing" do something close
to what I wanted) is based on this doc and thus my howto cuts off some details
which can be found at aphroland.de.
I'd like to notice one difference in advance: while aphroland's description uses a base
structure like "o=domain,c=country" for the LDAP tree, I'll use the more common
"dc=domain,dc=country". Nevertheless, this actually depends on your taste (among
other things) and is just kind of a naming-convention.
We want our server (as well as the clients later on) to support SSL, so we'll have to recompile and install our own Debian packages:
Get the source:
cd ~
mkdir slapd_woody-source
cd slapd_woody-source
apt-get source slapd
apt-get build-dep slapd
apt-get install libssl-dev
Activate SSL:
cd openldap2-2.0.23
vi debian/rules
--> and replace --without-tls with --with-tls
[ vi debian/changelog ]
Compile the packages:
dpkg-buildpackage -b -us -uc
Invoking dpkg-buildpackage -b -us -uc creates the .deb-packages in ~/slapd_woody-source/, which you should install blindly accepting the default-values presented by Debconf. (As described at aphroland.de, we'll wipe out the default-stuff and start from scratch on ourselves.)
cd ~/slapd_woody-source/
dpkg -i slapd_2.0.23-6_i386.deb
libldap2_2.0.23-6_i386.deb
libldap2-dev_2.0.23-6_i386.deb
ldap-utils_2.0.23-6_i386.deb
[ Get subnet's self-compiled slapd packages ]
/etc/init.d/slapd stop
In order to prevent the packages to be replaced by the ones from the Debian-repository,
set them to HOLD. (Use dselect or a command like
"echo "slapd hold" | dpkg --set-selections" for this.)
But be aware to keep track of possible security-updates for these packages on your own
from now on! (Upgrading to the possibly new packages then should be easily possible
by running "dpkg -i ..." again. Make sure to have backups of your configuration before
as well as to set the packages to HOLD afterwards again.)
Wiping out Debian's default configuration and setting up our own one works as follows:
adduser slapd
chown -R slapd.slapd /etc/ldap
chmod 770 /etc/ldap
find /etc/ldap -type f -exec chmod 440 {} \;
find /etc/ldap -type d -exec chmod 770 {} \;
chown -R slapd.slapd /var/lib/ldap
chmod 750 /var/lib/ldap
rm /var/lib/ldap/*
chown -R slapd.slapd /var/spool/slurpd
rm /var/spool/slurpd/*
cd /etc/ldap/
mv slapd.conf slapd.conf_DEB-orig
This way, the user "slapd" (which we'll use to run the LDAP-server later-on) is the only one who can read the LDAP configuration as well as the database.
Here's the first basic version of our main configuration file, /etc/ldap/slapd.conf:
######################### /etc/ldap/slapd.conf #########################
# http://homex.subnet.at/~max/ldap/
#
# Basic slapd.conf
include /etc/ldap/schema/core.schema
include /etc/ldap/schema/cosine.schema
include /etc/ldap/schema/nis.schema
include /etc/ldap/schema/inetorgperson.schema
include /etc/ldap/schema/misc.schema
schemacheck on
pidfile /home_local/slapd/slapd.pid
argsfile /home_local/slapd/slapd.args
password-hash {CRYPT}
replogfile /var/lib/ldap/replog
loglevel 256
database ldbm
suffix "dc=subnet,dc=at"
# use "/usr/sbin/slappasswd -h {CRYPT}" to create a rootpw-string below
# (note: if you use the tcsh shell, you will have to use single quotes
# to surround the {CRYPT}, i.e.: /usr/sbin/slappasswd -h '{CRYPT}')
rootpw {CRYPT}xxxxxxxxxx
directory "/var/lib/ldap"
index objectClass eq
lastmod on
access to attribute=userPassword
by dn="cn=manager,dc=subnet,dc=at" write
by anonymous auth
by * none
access to *
by dn="cn=manager,dc=subnet,dc=at" write
by dn="cn=nss,dc=subnet,dc=at" read
by * auth
#######################################################################
Differences to aphroland's description include using {CRYPT}-hashes instead of {MD5}-ones as well as starting the server as root and have it drop his privileges in order to become the user "slapd" as soon as it has bound to the ports 389 and 636. (See below for details.)
Next, besides editing the rootpw-line in your slapd.conf, run some more file-system stuff:
# chown slapd.slapd slapd.conf # chmod 440 slapd.conf # ll total 12 drwxrwx--- 2 slapd slapd 4096 Jun 3 14:38 schema -r--r----- 1 slapd slapd 864 Jun 3 14:41 slapd.conf -r--r----- 1 slapd slapd 1928 Jun 3 14:38 slapd.conf_DEB-orig
As our database is currently less than empty, we need to populate it.
To be able to test the setup, use a file like the following which
holds the basic data to be added.
As you've already checked out some general documents on LDAP (haven't you?),
you should already know that this file
is in "LDIF"-format:
dn: dc=subnet,dc=at
objectClass: organization
o: subnet
dn: cn=manager, dc=subnet,dc=at
objectClass: organizationalRole
objectClass: simpleSecurityObject
cn: admin
description: LDAP administrator
userPassword: {CRYPT}xxxxxxxxxx
dn: cn=nss, dc=subnet,dc=at
objectClass: organizationalRole
objectClass: simpleSecurityObject
cn: nss
description: LDAP NSS user for user-lookups
userPassword: {CRYPT}xxxxxxxxxx
dn: ou=People, dc=subnet,dc=at
objectClass: organizationalUnit
ou: People
dn: ou=Group, dc=subnet,dc=at
objectclass: top
objectclass: organizationalUnit
ou: Group
dn: uid=maxldap, ou=People,dc=subnet,dc=at
objectClass: inetOrgPerson
objectClass: posixAccount
objectClass: top
objectClass: shadowAccount
objectClass: organizationalPerson
objectClass: inetLocalMailRecipient
uid: maxldap
cn: Markus LDAP Test User Amersdorfer
sn: Amersdorfer
givenname: Markus LDAP Test User
title: Admin
departmentNumber: IT
mobile: 012-345-6789
postalAddress: AddressLine1$AddressLine2$AddressLine3
telephoneNumber: 1234-567890
facsimileTelephoneNumber: 012-345-6789
userpassword: {CRYPT}xxxxxxxxxx
labeleduri: http://homex.subnet.at/~max/
mail: my.email.address@example.com
mail: my.alternate.email.address@example.com
mailRoutingAddress: my.email.account@mail.server.example.com
loginShell: /bin/bash
uidNumber: 12345
gidNumber: 12345
homeDirectory: /home_local/maxldap/
gecos: maxldap_gecos-field
description: Not Available
localityName: Bellevue
dn: cn=maxldap,ou=Group,dc=subnet,dc=at
objectClass: posixGroup
objectClass: top
cn: maxldap
gidNumber: 12345
Don't forget to run the "/usr/sbin/slappasswd -h {CRYPT}"-command
to create password-hashes for the users with {CRYPT}-entries listed in the .ldif-file.
(Again, if you use the tcsh shell, this might produce an error stating something like
"Password generation failed for scheme CRYPT: scheme not recognized". To work around
this, surround the parameter with single quotes, i.e. run the following command
instead: "/usr/sbin/slappasswd -h '{CRYPT}'". Also see this
OpenLDAP mailing-list article
on this issue.
Many thanks to Martin B. Smith for pointing this out!)
The normal user uid=maxldap:
Mind the naming pattern used here for the normal user "maxldap": its distinguished name "dn:"
(which is unique within the global LDAP namespace)
is constructed by using the user's "uid=maxldap" attribute (which equals to the Linux user's login name,
the corresponding Linux user's UID can be found as LDAP's attribute "uidNumber") prefixing
the tree "ou=People,dc=subnet,dc=at".
This places the user in the organizational unit "ou=People" of "subnet.at" ("dc=subnet,dc=at").
Some sites use the users' common names ("cn:") instead of the uid's to differentiate between single
LDAP entries (users). While it basically boils down to a matter of taste on the one hand (whether you prefer
"uid=maxldap,ou=People,..." over "cn=Markus Amersdorfer,ou=People,..." or the other way round),
on the other hand it's definitely better
to use "uid=" here. The simple reason is that both the MigrationTools
(see section Migrate Your Linux Users below)
and Samba (see section Samba 2.2.x and LDAP below) use this pattern.
You'll save yourself a lot of time if you stick with "uid=,ou=,dc=,dc=".
The special user cn=nss:
With our current ACLs, nobody except cn=manager and cn=nss can perform standard read
functionality on our LDAP tree. Nevertheless, to be able to become a user (e.g. using "su user")
or to get information about the user ("finger user"), the tree must be readable, at least
to the Name Switch Service (NSS) (see section NSS: Name Service Switch below).
It depends on your situation to either set read-rights for everyone to ou=People, or
to use this cn=nss user so that NSS can lookup the users. I'll describe the latter scenario.
You can and should add the data above to the (currently not running) OpenLDAP database by executing:
# su - slapd $ /usr/sbin/slapadd -l /etc/ldap/basics-subnet.ldif
Using "slapcat" you get the database's current contents without having to perform "ldapsearch" or similar. This can be useful for debugging processes.
You can now - being root - start the OpenLDAP server (without having it disappear into daemon-mode):
# /usr/sbin/slapd -u slapd -h ldap://0.0.0.0/ -d 255
This starts the OpenLDAP server "slapd" initially as root, binds to the corresponding
port (TCP/389) on all local interfaces, drops root privileges by becoming the user
"slapd" and presents you with 'live' debugging information on your screen.
(Hint: Browse through this stuff to get a feeling for OpenLDAPs debugging information and error messages.)
Having the OpenLDAP server up and running, we can deal with the client-side now...
On Linux (and some other UNIX-flavours), accessing the users-database is not just
looking up the passwd/shadow/a.s.o. files. Nowadays, most applications use library
calls to get user information or accomplish user authentication.
While the PAM system (Pluggable Authentication Module, see below) is used to
accomplish a user's authentication (i.e. checking if provided login and password
are correct, accomplish some other (stackable and thus highly configurable) tasks
and finally decide for example whether the user may login or not),
the Name Service Switch is a service which provides you with a user/group/a.s.o. listing.
To get your local machine's or network's listing, just run "getent passwd".
The first task now is to set up the NSS correctly to query the OpenLDAP server additionally
to the local passwd-files (and/or the already used NIS). This is done by installing
the package "libnss-ldap" and configuring the nss-processes to use it.
This description goes for both your network-clients as well as the LDAP-server itself (as we want the server's Linux-system too to know the users and other information stored using OpenLDAP)!
In order to have any traffic between the clients and server be encrypted, we again need to compile the packages ourselves to support SSL. (The actual configuration of encrypted communication can be found later in the document.)
cd ~
mkdir libnss-ldap_woody-source
cd libnss-ldap_woody-source
apt-get source libnss-ldap
cd libnss-ldap-186
vi debian/rules
--> and replace --disable-ssl with --enable-ssl
[ vi debian/changelog ]
dpkg-buildpackage -b -us -uc
dpkg -i libnss-ldap_186-1_i386.deb
[ Get subnet's self-compiled libnss-ldap package ]
echo "libnss-ldap hold" | dpkg --set-selections
mv /etc/libnss-ldap.conf /etc/libnss-ldap.conf_DEB-orig
The final two commands install the new libnss-ldap-package and set it to HOLD status.
But be aware to keep track of possible security-updates for these packages on your own
from now on! (Upgrading to the possibly new packages then should be easily possible
by running "dpkg -i ..." again. Make sure to have backups of your configuration before
as well as to set the packages to HOLD afterwards again.)
Mind: The manual page for libnss-ldap.conf does not specify all of the module's options. In order to be able to browse through the capabilites later (and perhaps activate some of them), we made a backup of Debian's original and (throughout the file itself) well-documented libnss-ldap.conf-file.
Once the package is installed, use the following /etc/libnss-ldap.conf file to configure the new functionality correctly:
######################### /etc/libnss-ldap.conf ######################## # http://homex.subnet.at/~max/ldap/ host ldap.subnet.at base ou=People,dc=subnet,dc=at uri ldap://ldap.subnet.at/ ldap_version 3 binddn cn=nss,dc=subnet,dc=at bindpw the_one_you_set_above_in_the_ldif-file__as-plaintext nss_base_passwd ou=People,dc=subnet,dc=at nss_base_group ou=Group,dc=subnet,dc=at #######################################################################
The bindpw-entry is the password for the NSS-user (cn=nss,dc=subnet,dc=at) you created above when populating the LDAP database. The password has to be stated as plaintext here, do not use the {CRYPT}-hash.
Now, include the LDAP NSS module in the system lookups by editing /etc/nsswitch.conf:
passwd: ldap compat group: ldap compat shadow: ldap compat
This way, lookups for passwd, group and shadow try LDAP first ("ldap") and
NIS and the local files next ("compat").
(If a user is listed both locally and in LDAP, it will also show up
twice in the output.
This feature is used in the setup described here to have the user "root" both be
served from LDAP and - as a fallback in case of LDAP wasn't reachable - have it
stored locally.
See section PAM: The user "root" and other system UIDs
below for details.)
It should be possible to lookup the LDAP-user "maxldap" using finger or getent now:
# finger maxldap Login: maxldap Name: maxldap_gecos-field Directory: /home_local/maxldap/ Shell: /bin/bash Last login Mon Jun 2 16:53 (CEST) on pts/1 from some-client.subnet.at No mail. No Plan.
NSCD is "a daemon which handles passwd, group and host lookups for running programs and caches the results for the next query". While this makes NSS-lookups faster, it also might lead to the situation where it might take some time for an update of user-data to reach all clients. (Or is there some "pushing"- or any other mechanism that solves this?)
Anyway, installing "nscd" might definitely be a good idea from the security point of view: The above mentioned /etc/libnss-ldap.conf file holds some clear-text information necessary to be able to perform NSS-lookups. In order to prevent the users from not knowing who they are - resulting in funny situations such as the prompt saying "i have no name!" instead of the actual user's login-name - this file has to be world-readable. But then, this means that everybody knows about the credentials of the "cn=nss" user and can do everything this special user can (which depends on the access-lists of the LDAP server).
Though I haven't tried it yet, NSCD can help you solve this issue:
Just install it and set the file-access-rights for /etc/libnss-ldap.conf
to "600" (owned by root).
In this setup, the corresponding library-request executed with the user's rights
should be handled by NSCD, which in turn runs with root-privileges (I guess, at
least), and thus can read the credentials from the config-file and perform the
corresponding DB-lookup.
As mentioned above, user lookups are seperated from user authentication on Linux systems. While the first is covered by NSS, the second is usually dealt with using PAM nowadays.
Basically, it's the same process here for the package "libpam-ldap" as it was with libnss-ldap
above: recompilation with SSL enabled and installation of the new package.
Nevertheless, the Debian Woody package has a special patch applied to be able to use
filters when checking whether a user is allowed to login or not. We'll use
this feature to be able to allow users to login to some specific workstations and
block access on the network's other workstations (see below for details).
Unfortunately,
this filter patch has a bug,
which means we'll need to install a patched version of libpam-ldap, compiled ourselves to support SSL.
This patched version is available from
Christof Meerwalds Debian section.
As with NSS, we want the LDAP-server itself too to be able to use the LDAP-based users for authentication. Thus, basically, the same configuration applies to the server as it does to the client machines (= Linux/Unix stations not running the LDAP server but just querying it for user lookups and authentication.)
Nevertheless, you have several options here now, depending on your needs and wishes. It's all about the user "root" and about changing user passwords.
I'll describe a setup here where root can change any user's password, but only on the machine running the OpenLDAP server. Reasons are that I want root to be able to change the passwords by simply running "passwd $user" (without having to know the user's old password). Nevertheless, this ability includes the need for the password for "cn=manager,dc=,dc=" to be stored on such a machine locally in a file, additionally it has to be in plaintext. This doesn't seem to be easy to administer (especially in the case where the manager's password changes) on the one hand, and it doesn't seem to be very secure either for obvious reasons on the other hand.
The only difference lies in the file "/etc/pam_ldap.conf" using the option "rootbinddn" on the server and "binddn" on all other machines. Furthermore, the server needs the file "/etc/ldap.secret" which holds the manager-user's password in plaintext (with access rights "600", owned by "root").
Most of the steps following are the same for all machines, no matter which configuration you chose. If not stated otherwise, it's the same for both possible setups.
Add to /etc/apt/sources.list:
# Patched libpam-ldap for Woody (http://cmeerw.org/debian/)
deb-src http://cmeerw.org/files/debian woody libpam-ldap
Run:
cd ~
mkdir libpam-ldap_cmeerw-source
cd libpam-ldap_cmeerw-source
apt-get update
apt-get source libpam-ldap
vi debian/rules
--> and replace --disable-ssl with --enable-ssl
[ vi debian/changelog ]
dpkg-buildpackage -b -us -uc
cd ..
dpkg -i libpam-ldap_140-1cmeerw_i386.deb
[ Get subnet's self-compiled libpam-ldap package ]
echo "libpam-ldap hold" | dpkg --set-selections
mv /etc/pam_ldap.conf /etc/pam_ldap.conf_DEB-orig
Again after installing the package, we set its status to HOLD.
But be aware to keep track of possible security-updates for these packages on your own
from now on! (Upgrading to the possibly new packages then should be easily possible
by running "dpkg -i ..." again. Make sure to have backups of your configuration before
as well as to set the packages to HOLD afterwards again.)
Though we'll use a setup without SSL and without host-specific access controls
for the moment, using the patched package and recompiling it with our modifications
we're ready for these things to come later on.
Mind: The manual page for pam_ldap.conf does not specify all of the
module's options. In order to be able to browse through the capabilites later
(and perhaps activate some of them), we made a backup of Debian's original and
(throughout the file itself) well-documented pam_ldap.conf-file.
Next, on all the clients (where root is not able to change the users' passwords), configure the new PAM module using this /etc/pam_ldap.conf:
########################## /etc/pam_ldap.conf ######################### # http://homex.subnet.at/~max/ldap/ # # pam_ldap.conf for all client machines host ldap.subnet.at base dc=subnet,dc=at uri ldap://ldap.subnet.at/ ldap_version 3 binddn cn=nss,dc=subnet,dc=at bindpw the_one_you_set_above_in_the_ldif-file__as-plaintext pam_password crypt #######################################################################
On the server (or on all machines where you want root to be able to change the users' passwords), first, use this /etc/pam_ldap.conf:
########################## /etc/pam_ldap.conf ######################### # http://homex.subnet.at/~max/ldap/ # # pam_ldap.conf for the server (where root can change user passwords) host ldap.subnet.at base dc=subnet,dc=at uri ldap://ldap.subnet.at/ ldap_version 3 rootbinddn cn=manager,dc=subnet,dc=at # don't forget /etc/ldap.secret pam_password crypt #######################################################################
and second don't forget to create the file /etc/ldap.secret with
access rights "600" and owned by "root" (i.e. only root can read the file) which holds the plaintext-password for
LDAP's "cn=manager,...".
(While, if I'm correct, I didn't have such in my setup originally: according to
Setting up LDAP for use with Samba,
there has to be a blank second line in this file.)
Now that we have the PAM module configured, we need to include it into the PAM process:
We'll check out the modifications to be able to log in using ssh and su.
Most PAM-aware applications have their own PAM-stack they use. Debian stores these
configuration-files in /etc/pam.d/.
Here is /etc/pam.d/ssh:
########################### /etc/pam.d/ssh ############################ # http://homex.subnet.at/~max/ldap/ auth required pam_env.so # Woody's SSHD checks for /etc/nologin automatically, # so there's no need for pam_nologin in /etc/pam.d/ssh. #auth required pam_nologin.so auth sufficient pam_ldap.so auth required pam_unix.so account sufficient pam_ldap.so account required pam_unix.so session sufficient pam_ldap.so session required pam_unix.so session optional pam_lastlog.so # [1] session optional pam_motd.so # [1] session optional pam_mail.so standard noenv # [1] session required pam_limits.so password sufficient pam_ldap.so password required pam_unix.so #######################################################################
The changes to the original file are:
Here is /etc/pam.d/su as another example:
########################### /etc/pam.d/su ############################# # http://homex.subnet.at/~max/ldap/ auth sufficient pam_rootok.so auth sufficient pam_ldap.so auth required pam_unix.so use_first_pass account sufficient pam_ldap.so account required pam_unix.so session sufficient pam_ldap.so session required pam_unix.so #######################################################################
The changes to the original file are:
Things to take care of:
Logging in via SSH or su'ing to the LDAP-user "maxldap" should work now:
$ ssh maxldap@ldap.subnet.at maxldap@ldap.subnet.at's password: Last login: Tue Jun 3 15:11:30 2003 from some-client maxldap@ldap:~$
CRYPT vs. MD5:
The good old shadow file typically stores passwords as hashes using the "crypt" algorithm.
More up to date systems often use "md5" somewhere in the process of hashing the password.
(These "md5"-passwords can be distinguished from the "crypt"-only ones by starting with "$1$".)
The Mandrake-based document on mandrakesecure.net (see section External Resources)
describes a way to use exactly the newer MD5-based approach
with your LDAP database. Unfortunately, either Debian doesn't support it or I simply
couldn't get this thing to work. (It seems I managed to have passwords being created using
MD5 and have them stored in the LDAP database this way, but unfortunately, I couldn't use
these hashes. I never got a user to authenticate successfully.)
Being well known for my paranoia ;), I really would have liked the MD5-thing
as it creates longer password hashes and uses passwords with more than just 8 characters.
Anyway, good old CRYPT will (have to) suffice...
BTW: One reason for even me thinking that "crypt" really is secure enough is that
the password is never sent in any way in plaintext over the network, as every
traffic between clients and server is secured using SSL (see below).
Even a local "root" user can't see the password-hash by executing "getent shadow".
Only the "LDAP Manager" is allowed to see the hash.
The only (really bad) thing you should remember is: "Crypt"-passwords have a maximum
length of 8 characters!
Here is my /etc/pam.d/passwd. Using it, the users can change their passwords on their own from the command-line by simply executing passwd.
########################### /etc/pam.d/passwd ########################### # http://homex.subnet.at/~max/ldap/ password sufficient pam_ldap.so password required pam_unix.so nullok obscure min=4 max=8 #########################################################################
I tried several versions here. Unfortunately, this is the only one I found where both
root and the users themselves (both LDAP-based users and local-only ones in passwd|shadow) can change their
passwords.
(Especially, I could not get the stuff working using pam_cracklib.so
or using use_first_pass with pam_unix.so. This would have been nice!)
Oh, and of course, don't forget the setup of /etc/pam_ldap.conf concerning root's non/ability to change users' passwords explained in section PAM Clients vs. Server Configuration above, but you've already read it anyway, haven't you?
(You actually don't have to worry about that just yet, just bare in mind you will have to decide later (when actually doing all the migration stuff in section Migrate Your Linux Users below) what to do with all the system accounts and with "root". Nevertheless, as it's about user accounts, I think the general knowledge about it belongs to PAM and thus here.)
I definitly recommend to keep your system UIDs (Debian currently treats the UIDs 1-999 as such)
only locally on every machine, do not migrate them into LDAP!
It's up to you what you do with "root". If you prefer to have one root account
for all machines (as I do), migrate "root" to LDAP. Otherwise, just treat it as a
system account and do not migrate it.
If you need reasons for not migrating them to LDAP:
Different services on different servers/machines will need different
system users to be present (e.g. the user "mysql" should only be available on a machine hosting
a MySQL server).
One day, you will upgrade your machines from Woody to Sarge. It can (and probably will)
happen that according to a new policy some system accounts changed their UID.
Upgrading just only one server will not work in this context, as the user "root" should
not be able to simply change those LDAP values. Even if it worked properly for one
server, what about the second? (Well, ok, everything might turn
out to work somehow, but IMHO you really don't want it this way :) ...)
And of course (above all), if you want to serve your users to client machines which do not
run Debian Woody and thus use a different system accounts scheme,
you'll have problems on your hands.
If you want to migrate the user "root" into LDAP (like I did), simply migrate it as described below in section Migrate Your Linux Users.
But be sure to also have "root" locally in /etc/(passwd|shadow|group).
If for some reason your LDAP server was not reachable, you still can log in to your
(LDAP)-client machines using the local "root" account.
With the setup explained here, logging in as "root" will use the LDAP-account by default.
Only if the LDAP server is not accessible, you will automatically fall back to the local
user/password from the flat files. Try this yourself to make sure your machines
behave properly.
(Mind the order "ldap compat" in /etc/nsswitch.conf,
described in section NSS: Installation (with SSL capable packages).)
ToDo - verify this again:
Oh, and before I forget and because it differs from standard Linux behaviour:
if "root" tries to change its LDAP-account password using
"passwd", it also needs to know its old password, just as any other user does!
(If you can't remember the password anymore, you'll need to change it directly in the
LDAP database, but that's probably what you will do anyway, won't you? :) ...)
Additionally, this also depends on section PAM Clients vs. Server Configuration,
actually...
Up to now, if a user shall has access to one host, they actually have access to all hosts on the network.
As described in the
Mandrake based LDAP-article
already mentioned in the resources section, one can define one or more
"host"-attributes (host is part of "objectClass: account")
in the user's LDAP-entry, specifying that this user is allowed
to login to the listed host(s).
Debian offers several ways to achieve our goal, from "simple" to "advanced":
For every host the user shall be able to login, add an attribute similar to "host: allowed-host.mydomain.net".
While Mandrake seems to have merged "libnss-ldap.conf" and "pam_ldap.conf" to
on single "ldap.conf" file, you already know that Debian uses the split-up approach.
The "pam_check_host_attr" option can be found in "/etc/pam_ldap.conf",
you can add the following there:
/etc/pam_ldap.conf [...] pam_check_host_attr yes
But be careful: As the comment in Debian's original pam_ldap.conf indicates, you'll need pam_ldap.so to be "configured for account management (authorization)". This means, that in the /etc/pam.d/<service> files, you'll have to replace "account sufficient pam_ldap.so" with "account required pam_ldap.so". (Otherwise, despite the message "Access denied..." the user will be granted access to the host.)
The more powerful way is the following one:
Debian's package libpam-ldap has a "filtering" patch applied. This way it is
possible to accompany the LDAP PAM module with some filtering-rules which must
match in order for the module to return successfully and allow the authentication-process
to proceed.
As already mentioned in section PAM: Pluggable Authentication Module,
the standard Woody package's filter patch has a bug which needs to be fixed.
As we've installed the corrected version from cmeerw.org, we already have a working version.
So here's how to do it:
For every host that the user shall be able to login, add an attribute similar to
"host: allowed-host.mydomain.net". If the user is allowed to login
to all hosts, simply add "host: *" to the LDAP entry.
Next thing is to adapt the PAM stack: This can either be done by editing
one (or more) specific service's config file in /etc/pam.d/, or by editing
/etc/pam_ldap.conf (which has influence on all services at once):
For single services only (e.g. /etc/pam.d/ssh): #auth sufficient pam_ldap.so auth sufficient pam_ldap.so filter=|(host=this-host.mydomain.net)(host=\*) For all services at once (/etc/pam_ldap.conf): pam_filter |(host=this-host.mydomain.net)(host=\*)
Only if the user's LDAP entry contains "host: this-host.mydomain.net" or "host: *", they are allowed to login.
Things to take care of:
Add-On:
Of course this setup can be extended for example by using self-defined attributes representing
groups of hosts (e.g. "my-hosts: workstations") and adapting the PAM module's filters.
With a little imagination it could perhaps also be possible to assign a user different shells
on different hosts!? I don't know yet...
It's all up to you. :)
Now that we have a running LDAP-server which provides user-information and also have clients authenticating using these LDAP-users, let's move on and make everything safer: Up to now, any traffic between the server and the clients was unencrypted. Let's activate the SSL-encryption our packages already are capable of (as we recompiled them ourselves).
You can find a description of how to create an SSL certificate here: HOWTO Create an SSL Certificate.
Once you have your signed certificate, you need to configure your OpenLDAP server to use it:
Add to your /etc/ldap/slapd.conf: [ ... loglevel xxx ] TLSCipherSuite HIGH:MEDIUM:+SSLv2 TLSCertificateFile /etc/ldap/server.cert TLSCertificateKeyFile /etc/ldap/server.key TLSCACertificateFile /etc/ldap/ca.cert TLSVerifyClient 0 [ ... database ldbm ] Start the LDAP server with the following command: # /usr/sbin/slapd -u slapd -h 'ldap://0.0.0.0/ ldaps://0.0.0.0/' -d 1
You can test the server's SSL capabilities (of course the client you are executing the second command needs the "ldap-utils"-package with SSL-support compiled into it!):
ldapsearch -b "ou=People,dc=subnet,dc=at" -LLL -D "cn=manager,dc=subnet,dc=at" \
-H "ldap://ldap.subnet.at/" -W -x "(uid=maxldap)"
ldapsearch -b "ou=People,dc=subnet,dc=at" -LLL -D "cn=manager,dc=subnet,dc=at" \
-H "ldaps://ldap.subnet.at/" -W -x "(uid=maxldap)"
Both commands, with and without SSL encryption, should return the entry for the user "maxldap".
Next step is to adapt the clients' setup:
Having already installed our re-compiled library-packages, this is as easy as
changing "uri ldap://ldap.subnet.at/"
to "uri ldaps://ldap.subnet.at/"> in both /etc/libnss-ldap.conf and
/etc/pam_ldap.conf.
Add-On:
To test if your clients really are communicating with the server
using an encrypted connection, make user-queries and logins with both settings
ldap:// and ldaps:// and a concurrently running "tcpdump -X host ldapserver".
This tcpdump-command shows you in ASCII the transmitted data. While using ldap:// you
should be able to find some cleartext in the data garbage, after switching to ldaps://
you should only see ... well, lot's of stuff, but no plaintext information.
Now that we have everything set up correctly concerning the connections (including SSL-support), we should look at the changes necessary to /etc/init.d/slapd to have the OpenLDAP server started correctly every time the machine boots - all we have to do is to change one line:
# start-stop-daemon --start --quiet --pidfile "$pf" --exec /usr/sbin/slapd
start-stop-daemon --start --quiet --pidfile "$pf" --exec /usr/sbin/slapd -- -u slapd \
-h 'ldap://0.0.0.0/ ldaps://0.0.0.0/'
This way, we have the process' user changed to "slapd" as well as the server listen for ldap-traffic on port 389 and ldaps-traffic on port 636.
"slapd" now logs to /var/log/debug.
So far, on the server side we have accomplished to set up and populate the OpenLDAP server.
Next, on the client side (this means every machine querying OpenLDAP, this most probably also
includes the "server" where OpenLDAP is running on) we have configured the Linux clients to use it,
they can look up the users and use those to log into machines. Communication between
the clients and the server is secured using SSL encryption.
All you have to set up on each "client" is:
Of course you want to migrate your current Linux users from passwd/shadow to
the new OpenLDAP server. Debian offers help here by providing the MigrationTools from
padl.com as the Debian package migrationtools,
so you could apt-get install this package.
Unfortunately, the package in Debian Woody (version 40-1) is rather buggy:
"migrate_base.pl" forgot an "s" with "dc: subnet",
"migrate_group.pl" didn't produce any output and
"migrate_passwd.pl" produced junk values for the attributes "cn",
"givenname" an "sn". Furthermore, the latter also uses different letter cases
in a newer version than Woody's one does (e.g. "givenName" instead of "givenname").
The newer version of Debian Sarge (currently version 44-6) definitely works better,
but also still produces junk values for the attributes "cn".
In order to get a working package you should download the original version of the MigrationTools from padl.com. I used version 44, which works fine for me.
In either case, you'll have to execute the scripts on the machine which currently holds your users already, in my case this was our NIS server (which was a different machine than the upcoming LDAP server), so install the migration-package there.
After exploding the tar-ball, edit /usr/local/MigrationTools-44/migrate_common.ph and adapt the following variables:
$DEFAULT_MAIL_DOMAIN = "subnet.at"; $DEFAULT_BASE = "dc=subnet,dc=at"; $DEFAULT_MAIL_HOST = "mail.subnet.at"; $EXTENDED_SCHEMA = 1;
Citing the initial Mandrake-LDAP document on this one (with "localisation"): "This sets some defaults for the migrated data. Here we set the default mail domain, in this case "subnet.at" which will assign all users a default email address of "user@subnet.at". The default base is "dc=subnet,dc=at" which should be identical to the suffix defined in slapd.conf. The default mail host is the SMTP server used to send mail, in this case "mail.subnet.at". The extended schema is set to 1 to support more general object classes."
03-08-12:
As Buchan Milne pointed out
in a mail on the Samba mailing-list
and his Howto Implementing disconnected authentication and PDC/BDC relationships using Samba and OpenLDAP,
changing those values in migrate_common.ph is not necessary: Setting and exporting according environment
variables (for example export LDAP_DEFAULT_MAIL_DOMAIN="subnet.at") works too and would survive
an eventual upgrade (though of course migrating users will probably be performed only once).
It's possible to migrate nearly all data to LDAP (including
/etc/(hosts|protocols|services) etc.), nevertheless, the only things we'll
use LDAP for are users and groups. ("hosts" would be good to migrate too, but we
have a local DNS server running, so no need for this here.)
Furthermore, as already mentioned above in section
PAM: The user "root" and other system UIDs, you'll
have to exclude your system accounts (Debian Woody uses the UIDs 1-999 for this)
and decide on what to do with "root" (UID 0). Especially keep in mind
when migrating both groups and users to delete all system accounts from
the .ldif-file created by the migration scripts!
ToDo: It should be possible to do this using some /sed/awk/grep/etc/ scripts.
The migration scripts are located in /usr/local/MigrationTools-44/
(or wherever you saved them to):
migrate_base.pl creates the LDAP tree's base structure.
The migrate_all_* migrate everything by simply calling the
single perl scripts.
As I've already mentioned, the only things we'll migrate are users and groups,
and of course we'll check out the base structure, so let's start with this one:
cd /usr/share/migrationtools/ ./migrate_base.pl > base.ldif
The only entries which are or might become interesting for us are the following base.ldif:
dn: dc=subnet,dc=at dc: subnet objectClass: top objectClass: domain objectClass: domainRelatedObject associatedDomain: subnet.at dn: ou=People,dc=subnet,dc=at ou: People objectClass: top objectClass: organizationalUnit objectClass: domainRelatedObject associatedDomain: subnet.at dn: ou=Group,dc=subnet,dc=at ou: Group objectClass: top objectClass: organizationalUnit objectClass: domainRelatedObject associatedDomain: subnet.at
(Here is the original base.ldif file with all the additional entries.)
Well, we basically do have this base structure already. The only difference is
that we are missing "objectClass: domainRelatedObject" and its associated attribute.
So we won't do anything here at the moment.
Here is the minimized output from ./migrate_group.pl /etc/group group.ldif:
dn: cn=max,ou=Group,dc=subnet,dc=at
objectClass: posixGroup
objectClass: top
cn: max
userPassword: {crypt}x
gidNumber: 1000
dn: cn=users,ou=Group,dc=subnet,dc=at
objectClass: posixGroup
objectClass: top
cn: users
userPassword: {crypt}x
gidNumber: 100
dn: cn=nogroup,ou=Group,dc=subnet,dc=at
objectClass: posixGroup
objectClass: top
cn: nogroup
userPassword: {crypt}x
gidNumber: 65534
This information can now be added to the LDAP server by executing something like the following:
ldapadd -H ldap://ldap.subnet.at/ -D "cn=manager,dc=subnet,dc=at" -x -W -f $FILE
BTW: The main purpose of a group is to hold several users :).
An entry in /etc/group
like "somegrp:x:12345:userone,usertwo" can be accomplished by adding a
"memberUid" attribute for each user to the group's LDAP entry:
"memberUid: userone" and "memberUid: usertwo".
./migrate_passwd.pl /etc/passwd passwd.ldif # Restrict access as this file holds all passwords: chmod 600 passwd.ldif
If you don't have any user passwords in your ldif file, try the command with an explicit environment variable set: ETC_SHADOW=/etc/shadow ./migrate_passwd.pl /etc/passwd passwd.ldif. This should ensure that the script find the /etc/shadow file, which most probably holds your passwords.
Debian Woody's schema files do not provide the objectClass "mailRecipient". Instead, it is called "inetLocalMailRecipient". Additionally, we didn't include the Kerberos schema in our slapd.conf, so we have to remove the corresponding objectClass. You can simply adapt all the entries by executing "sed" like the following:
sed s/mailRecipient/inetLocalMailRecipient/g passwd.ldif | \
sed '/^objectClass: kerberosSecurityObject$/d' | sed '/^krbName: /d' \
> passwd.ldif_corrected
chmod 600 passwd.ldif_corrected
Here is the corresponding passwd.ldif file (again with one user only, the corrected objectClass and other values):
dn: uid=max,ou=People,dc=subnet,dc=at
uid: max
cn: Markus Amersdorfer
givenname: Markus
sn: Amersdorfer
mail: THEUSERNAME@subnet.at
mailRoutingAddress: THEUSERNAME@mail.subnet.at
mailHost: mail.subnet.at
objectClass: inetLocalMailRecipient
objectClass: person
objectClass: organizationalPerson
objectClass: inetOrgPerson
objectClass: account
objectClass: posixAccount
objectClass: top
objectClass: shadowAccount
userPassword: {crypt}$1$_my-password-hash-from-/etc/shadow
shadowLastChange: 12174
shadowMax: 99999
shadowWarning: 7
loginShell: /bin/bash
uidNumber: 1000
gidNumber: 1000
homeDirectory: /data/home/max
gecos: Markus Amersdorfer,,,
This information can again be added to the LDAP server by executing something like the following:
ldapadd -H ldap://ldap.subnet.at/ -D "cn=manager,dc=subnet,dc=at" -x -W -f passwd.ldif_corrected Enter LDAP Password: adding new entry "uid=max,ou=People,dc=subnet,dc=at"
Now that we have a working LDAP server to hold all our Linux-users, it would be useful
to have the network's Windows machines use this database too, of course.
As no flavour of Windows (AFAIK) can access the LDAP database directly, the Windows machines
(both servers and clients) will have to be part of a domain which is controlled by a Samba PDC.
Thus, the Windows machines will allow access based on what the (Samba) PDC says which again
makes its decisions on what the users in the LDAP database look like.
(This means, all Windows/Samba clients query the Samba-PDC. The Samba-PDC queries LDAP
for entries which are "objectClass: sambaAccount".)
03-08-15: See user comment from Aug 14, 2003.
Oh, and by the way, remember that this HOWTO-document uses Debian Woody
as the underlying distribution, so "Samba" refers to "Samba 2.2.3a" currently.
(Infos on Samba 3.x are as welcome and will be included here as any other feedback!)
Another add-on: You only have to install this "special LDAP-Samba version" on the machine which performs as your network's PDC. All other Samba machines should be configured to use this one Samba PDC as their "oracle" for user authentication. (You'll use options like "security = DOMAIN" and "password server = MYPDC" to accomplish this.)
Samba itself (if it's not configured to query some other server for user-authentication)
can either use the smbpasswd file to hold its users
or use an LDAP server to accomplish this. It's not
possible to do both at the same time, you have to decide at compile time.
The default behaviour is to use the flat smbpasswd file. Debian Woody's Samba packages
of course defaults to the default in this case. Conclusion: Recompilation is necessary.
cd ~
mkdir samba-source
cd samba-source
apt-get source samba
cd samba-2.2.3a
vi debian/rules
--> add "--with-ldapsam \" just before "--with-msdfs"
[ vi debian/changelog ]
dpkg-buildpackage -b -us -uc
[ Due to missing build-dependencies:
apt-get install libreadline4-dev libcupsys2-dev
[with extra-packages "libcupsys2 libjpeg62 libtiff3g"]
dpkg-buildpackage -b -us -uc
]
cd ..
dpkg -i samba-common_2.2.3a-13subnet_i386.deb
samba_2.2.3a-13subnet_i386.deb
smbclient_2.2.3a-13subnet_i386.deb
smbfs_2.2.3a-13subnet_i386.deb
samba-doc_2.2.3a-13subnet_all.deb
[ Currently now packages available, please build them yourself ... ]
Mind:
In order for Samba to support ACLs,
I also added "--with-acl-support" and changed in debian/config.cache the
value "ac_cv_header_sys_acl_h=${ac_cv_header_sys_acl_h=no}" to
"ac_cv_header_sys_acl_h=${ac_cv_header_sys_acl_h=yes}".
Again, "dpkg-buildpackage" might not compile the packages at the first time
you run it due to some missing build-dependencies. apt-get install the mentioned
packages and run "dpkg-buildpackage" again in this case.
Again, set the packages to HOLD using dselect or something like
"echo "samba-common hold" | dpkg --set-selections".
But be aware to keep track of possible security-updates for these packages on your own
from now on! (Upgrading to the possibly new packages then should be easily possible
by running "dpkg -i ..." again. Make sure to have backups of your configuration before
as well as to set the packages to HOLD afterwards again.)
Next, teach your LDAP server the possibilities of Samba by adding the Samba schema file and restrict the access to the users' Samba passwords using the Access Control Lists:
Run:
cp /usr/share/doc/samba-doc/examples/examples/LDAP/samba.schema.gz /etc/ldap/schema/
cd /etc/ldap/schema/
gunzip samba.schema.gz
chown slapd.slapd samba.schema
chmod 440 samba.schema
Add to /etc/ldap/slapd.conf:
include /etc/ldap/schema/samba.schema
Change the already exiting password ACL rule in /etc/ldap/slapd.conf:
# access to dn=".*,dc=subnet,dc=at" attribute=userPassword
access to dn=".*,dc=subnet,dc=at" attribute=userPassword,lmPassword,ntPassword
[...]
Restart OpenLDAP:
/etc/init.d/slapd restart
Now that you have an "LDAP capable" Samba installed and now that your OpenLDAP knows about the new attributes, of course the Samba server needs to be able to query the LDAP server for users. I tried to think of a setup which would not use "cn=manager,..." for this, but I just couldn't figure one out. The main reasons are that Samba (in some way) must be able to change the passwords (e.g. using "smbpasswd") and above all edit or even add LDAP entries (e.g. machine accounts for new SMB-clients joining the domain).
Of course, Samba has to know about this user and it's password. This leads us to the next (and one of the last) steps to do: configure smb.conf (and thus Samba and its tools) correctly to use the LDAP server properly. Here are the additions to be added to the [global] section of your Samba PDC:
/etc/samba/smb.conf, add to [global]: # Without SSL: ldap admin dn = cn=manager,dc=subnet,dc=at ldap server = ldap.subnet.at ldap suffix = ou=People,dc=subnet,dc=at # Plus these options for SSL support: #ldap port = 636 #ldap ssl = on Restart Samba: /etc/init.d/samba restart
Here is a sample smb.conf file.
BTW: As Implementing a Samba LDAP Primary Domain Controller Setup on Mandrake 9.x states, we probably don't need (and thus don't want) the overhead of encryption on the very same system where both OpenLDAP and Samba are running on. (If the two services run on different machines, you can add the two options "ldap port" and "ldap ssl" accordingly.
Last but not least, we have to tell Samba the corresponding password:
# read -s -p "Enter LDAP Root DN Password: " LDAP_BINDPW
# smbpasswd -w $LDAP_BINDPW
--> output:
Setting stored password for "cn=manager,dc=subnet,dc=at" in secrets.tdb
This way, you set an environment variable to the corresponding password and use it in the
next command to tell Samba about it. (That's a very neat trick I saw at B. Milne's
"Implementing Disconnected Authentication and PDC/BDC Relationships Using Samba and OpenLDAP"
to keep the password from your shell's history file and similar.
It will not show up anywhere :).)
"smbpasswd -w $LDAP_BINDPW" is the actual command of interest. Basically, it stores
a password hash for the user of smb.conf's option "ldap admin dn"
in the file /var/lib/samba/secrets.tdb.
Before messing around too much with your (already existing?)
LDAP users, you might want to test if the new setup works properly.
If you don't want to do this, just go on and proceed with the next section
Samba: Add (Windows) Users.
As Samba needs a "Linux user" for/below every "Samba user", we simply add
one to the local flat files (passwd|shadow|group). Not saving it
in LDAP at this time yet helps keeping things seperated, simple and "a way
which is already known".
Nevertheless, the corresponding Samba user to be added will - of course -
be stored in the LDAP database, 'cause that's what we want actually.
Add the "Linux user" (to local flat files):
# adduser --no-create-home maxsmb
[e.g. password: 12345]
Add the "Samba user" (to LDAP):
# smbpasswd -a maxsmb
--> output:
New SMB password: abcde
Retype new SMB password: abcde
LDAP search "(&(uid=maxsmb)(objectclass=sambaAccount))" returned 0 entries.
Added user maxsmb.
Check yourself:
# getent passwd | grep maxsmb
# ldapsearch -b "ou=People,dc=subnet,dc=at" -LLL -D "cn=manager,dc=subnet,dc=at" -W -x "(uid=maxsmb)"
One can now access the Samba server using this user, change its password using "smbpasswd $user", etc. - business as usual. The "only" difference is that now the LDAP server is used to hold the information which is usually stored in smbpasswd:
client$ smbclient -L //ldap
Password:
Anonymous login successful
Domain=[SUBLDAP] OS=[Unix] Server=[Samba 2.2.3a-12 for Debian]
Sharename Type Comment
--------- ---- -------
tmp Disk
maxsmb Disk
IPC$ IPC IPC Service (yellow server (Samba 2.2.3a-12, LDAP-Test))
ADMIN$ Disk IPC Service (yellow server (Samba 2.2.3a-12, LDAP-Test))
client$ smbclient //ldap/tmp
added interface ip=193.170.141.119 bcast=193.170.141.127 nmask=255.255.255.128
Password:
Anonymous login successful
Domain=[SUBLDAP] OS=[Unix] Server=[Samba 2.2.3a-12 for Debian]
smb: \>
client$ smbclient //ldap/maxsmb
added interface ip=193.170.141.119 bcast=193.170.141.127 nmask=255.255.255.128
Password:
Anonymous login successful
Domain=[SUBLDAP] OS=[Unix] Server=[Samba 2.2.3a-12 for Debian]
tree connect failed: NT_STATUS_WRONG_PASSWORD
client$ smbclient //ldap/maxsmb -U maxsmb
added interface ip=193.170.141.119 bcast=193.170.141.127 nmask=255.255.255.128
Password: abcde
Domain=[SUBLDAP] OS=[Unix] Server=[Samba 2.2.3a-12 for Debian]
smb: \>
Now that everything is proven to work properly, you can extend your LDAP users
to become Samba capable.
But before doing that, don't forget to remove this section's test user "maxsmb":
# ldapdelete -D "cn=manager,dc=subnet,dc=at" -W -x "uid=maxsmb,ou=People,dc=subnet,dc=at" # deluser --remove-home maxsmb
In order for Samba to allow access to shares for certain users (and don't allow for others), it needs to know these users. If you just have a few of them, there's nothing easier than to simply add them:
# smbpasswd -a $user
This command seems to perform an LDAP search for an already existing entry matching
"(&(uid=maxsmb)(objectclass=sambaAccount))".
If none is found, it either creates the entire user (as is the case in the example in section
Samba: Test your Setup), or it uses an already existing
normal Unix-user and adds the corresponding Samba attributes.
If it finds an entry matching its query (which means the user already exists as
a Samba-user), it simply updates the password-hashes
(no matter whether it's invoked as "smbpasswd $user" or "smbpasswd -a $user").
If you have lots of users already existing in the LDAP tree (e.g. due to migrating them as described above), or if you have lots of "Windows-users" to add, you'll need a script to do the work:
# Warning: This should work, but I didn't try it in large scale:
ldapsearch -b "ou=People,dc=subnet,dc=at" -LLL -D "cn=manager,dc=subnet,dc=at" \
-W -x '(&(objectClass=posixAccount)(!(objectClass=sambaAccount)))' | grep "uid: " \
| awk '{print $2}' > linux-and-not-samba-users.txt
for user in `cat linux-and-not-samba-users.txt`; do echo $user `makepasswd` \
>> users-with-samba-passwords.txt; done
sed s/^/"smbpasswd -a "/ users-with-samba-passwords.txt > make-them-samba-users.sh
chmod 600 users-with-samba-passwords.txt
chmod 700 make-them-samba-users.sh
./make-them-samba-users.sh
This takes all Linux-users which are not Samba-users already, makes them Samba-users and
assigns them a random password (creating the random passwords using makepasswd might
take a while!). You can easily tell your users about their passwords as they are stored in
users-with-samba-passwords.txt.
Mind that the filter is included in '...' and not "...". (Somehow the BASH
messes something up when using double-quotes, even when escaping & and ! using \.)
"net rpc vampire".
03-08-13:
In contrast to the initial release of this howto, I meanwhile figured out how to
have a machine account automatically be added to the LDAP-tree.
Both possible ways, adding the account manually or have Samba add it automatically
(if it doesn't exist already),
use this script I wrote: create-machine-account.sh.
ToDo: Some parts of the script should be rewritten to clear things up
and make the script simpler (e.g. by using functions to print the status messages).
It's a little mess currently, but it works.
add user script = /usr/local/sbin/create-machine-account.sh %u
What create-machine-account.sh does basically boils down to:
Usage: # ./create-machine-account.sh NewMachineName$ <I>
(WITH the machine account's trailing "$"). In "non-interactive" mode
(i.e. without option "I"), all the script's status messages are logged using /usr/bin/logger.
Mind: At the beginning of the script are three options which can be changed,
but are consistent with our setup here by default.
Joining the domain on the Windows machine works as usual. Just perform steps 1 and 3 of
this mini-Howto describing exactly that:
Howto join a Windows client to a domain.
(But be careful: You'll need the user "root" as mentioned in step 2.
If it doesn't already exist,
adding at least the "objectClass: sambaAccount" part to LDAP
"is left to the reader as an exercise".
I now, you probably hate this phrase as much as I do... sorry!)
You can now log on to this machine using all valid LDAP sambaAccount entries.
According to B. Milne's document it should be possible to have all
"Domain Administrators" join a machine to the domain. I didn't try this yet.
BTW: Using "ou=People" is different from the smbldap-tools
(smbldap-tools work-log) which use
"ou=Computers,dc=,dc=" for machine accounts.
Nevertheless, searching for MachineAccounts is easy here too: just "ldapsearch" for
"(gecos=MachineAccount)".
Add-on: Joining a Windows machine to the domain if the machine-account already exists works just fine too. (Thus it's possible to re-use machine-accounts in case a machine left the domain without having to delete the machine-account first.)
Joining a Samba-Workstation to our Samba-PDC controlled domain involves the
same steps on the server-side as does joining a Windows-Workstations. That makes
sense, of course, since both systems behave the same and talk the same protocol.
This results in in the same steps as described above in section
Samba: Join Windows-Workstations to our Samba-PDC Domain:
So, after creating the machine account (for both Linux and Samba) using our script "create-machine-account.sh", join the client to the domain by running the following commands on the new workstation:
client:~# /etc/init.d/samba stop client:~# smbpasswd -j SUBLDAP -r YELLOW 2003/08/08 20:24:31 : change_trust_account_password: Changed password for domain SUBLDAP. Joined domain SUBLDAP. client:~# /etc/init.d/samba start
Here is the according sample smb.conf of a joining workstation.
The most important options are
"workgroup = SUBLDAP", "security = DOMAIN",
"password server = YELLOW" and "local master = No".
Oh, and just to make sure: I performed this stuff with /etc/samba/ containing only
smb.conf, and no other files such as MACHINE.SID or similar stuff.
Just for your information: Joining the domain creates the file /etc/samba/MACHINE.SID on the joining Samba machine.
After successfully setting up the server and the (Linux-) clients (see So Far So Good, Part 1),
we migrated the current Linux-users of the network (which a NIS-server might have provided to the clients)
using the official MigrationTools package from padl.com: We created ldif files for the base structure, the groups
and the users (including shadow-passwords) and edited them (e.g. to exclude system users) prior to adding this
information to the LDAP-Server.
Next, we set up LDAP-capable Samba-packages on the server only. In our network, this Samba-server will become
the domain's PDC with all Windows- and Samba-clients querying this PDC. We taught the OpenLDAP-server
to use the new Samba-attributes. Using some commands, we added sambaAccount's to our posixAccount's users,
assigning random passwords to the users. Furthermore, we discussed joining SMB-clients (both Windows and Samba)
to the domain using a custom script to set up the corresponding machine accounts.
As the header indicates, this section is currently still marked "ToDo".
As basically goes for the total HOWTO: I'll add things as soon as they are ready,
corrections as soon as bugs are found.
Besides the Gnome- and web-based tools mentioned here, there are also KDE tools, of course. Check out this list of Graphical LDAP tools over at the LDAP Linux HOWTO.
Directory Administrator is a GTK-based LDAP client.
Directory Administrator makes adding/editing/deleting users/groups really easy!
If it wasn't for all our wish to understand what's behind all those
GUI tools, one would probably use this one from the beginning already.
Debian packages for a current version backported to Woody can be found in Christof Meerwald's Debian section.
GQ is a GTK-based LDAP client.
GQ is great to browse your overall LDAP tree and get a good feeling of
what's where. Easy access to all available attributes etc.
Debian packages for a current version backported to Woody can be found in Christof Meerwald's Debian section.
Citing the homepage:
phpLDAPadmin is a web-based LDAP
application for managing all aspects of your LDAP server."
(phpLDAPadmin was formerly known as "DaveDAP". Citing from its description: "DaveDAP is a web-based LDAP admin tool written in PHP. You can browse your LDAP tree, create, delete, edit, and copy objects, perform searches, and view your server's schema. You can even copy objects between two LDAP servers and recursively delete or copy entire trees.")
As much as I would have liked to re-work this document for Debian 3.1 ("Debian Sarge"), I unfortunately neither have the time nor the resources to do so. (I moved to the UK, and I do not have access to e.g. the necessary hardware resources here anymore.)
Still, I would like to share my experiences with a preliminary version
of Debian Sarge, dated back about half a year ago to January 2005.
Note though that my notes below are based on LDAP packages of versions 2.1.xx,
while the final Debian Sarge ships LDAP packages of versions 2.2.xx.
Since, thus, the following work-log is currently not
based on the final version of Sarge, please treat it as such: A work-log.
(This state of information is also reflected in the state of structuring:
It's more a "bunch of" than a "list of". Sorry 'bout that ... should I get
the time and resources again to work on this any further, I'll gladly do
so.)
With the Sarge version, I tried to stick more to the Debian default packages as they are. The default configuration is not removed anymore, for example. Recompilation of the packages is also not necessary ...
If you're running Debian Sarge, give the descriptions below a chance. For more information on some issues, please check the Woody documentation above. (The general LDAP principles are still the same, of course!)
Comments and corrections are welcome indeed, as always!
Install the packages "slapd" (2.1.30-3) and
"ldap-utils" (2.1.30-3) as well as the dependencies
and recommendations:
# dselect
Reading Package Lists... Done
Building Dependency Tree... Done
The following NEW packages will be installed:
db4.2-util ldap-utils libiodbc2 libltdl3 libsasl2-modules slapd
0 upgraded, 6 newly installed, 0 to remove and 0 not upgraded.
Need to get 1559kB of archives.
After unpacking 4026kB of additional disk space will be used.
Do you want to continue? [Y/n]
Concerning the configuration of these packages:
example.comexample.comadminpasswordNo.
The only thing to change in the /etc/ldap/slapd.conf file is to add
(near the beginning of the file) the "misc.schema" to be used:
######################### /etc/ldap/slapd.conf ######################### # Note: We need this to be able to have entries with attributes such as # "mailRoutingAddress" (which we need as we'll use the LDAP-server # to host the mail-users and -domains for the Postfix SMTP server). # # [...] include /etc/ldap/schema/misc.schema # [...]
Don't forget to restart the LDAP server afterwards:
# /etc/init.d/slapd restart
In order to connect to the server from an Ubuntu Linux client (which is what
I use on my client machine), simply install the "ldap-utils"
package and run something like:
$ ldapserach -x -b "dc=example,dc=com"
If you want to connect as the LDAP-admin from anywhere on the network, use something like this
$ ldapsearch -b "dc=example,dc=com" -LLL -D "cn=admin,dc=example,dc=com" \
-H "ldap://yourserver.example.com" -W -x
If you want a graphical client, install e.g. the package "gq".
Ubuntu 4.10 (aka "Warty") comes with version 1.0beta1-1. For some reason, I could not
add a new server to its config using the graphical menu. The solution is to
fire up your editor and add the following section to your (already existing
as you should start once and stop GQ first) ~/.gq file:
<ldapserver>
<name>peach</name>
<ldaphost>yourserver.example.com</ldaphost>
<ldapport>389</ldapport>
<basedn>dc=example,dc=com</basedn>
<binddn>cn=admin,dc=example,dc=com</binddn>
<pw-encoding>Base64</pw-encoding>
<search-attribute>cn</search-attribute>
</ldapserver>
You can now modify the server settings, but with the above config, you should already be able to connect to the server as "admin". Note though that all your data (including the password) is transferred in cleartext!
Next, add some test-data to your LDAP database, using the following file
"basic-test-user.ldif":
dn: ou=People,dc=example,dc=com
objectClass: organizationalUnit
ou: People
dn: ou=Group,dc=example,dc=com
objectclass: top
objectclass: organizationalUnit
ou: Group
dn: uid=maxldap,ou=People,dc=example,dc=com
objectClass: inetOrgPerson
objectClass: posixAccount
objectClass: top
objectClass: shadowAccount
objectClass: organizationalPerson
objectClass: inetLocalMailRecipient
uid: maxldap
cn: Markus Peach LDAP User Amersdorfer
sn: Amersdorfer
givenname: Markus Peach LDAP User
title: Dipl.-Ing.
departmentNumber: IT
mobile: 012-345-6789
postalAddress: AddressLine1$AddressLine2$AddressLine3
telephoneNumber: 1234-567890
facsimileTelephoneNumber: 012-345-6789
userpassword: {CRYPT}SOME-CHARACTERS-OF-YOUR-PASSWORD-HERE
labeleduri: http://homex.subnet.at/~max/
mail: my.email.address@example.com
mail: my.alternate.email.address@example.com
mailRoutingAddress: my.email.account@mail.server.example.com
loginShell: /bin/bash
uidNumber: 12345
gidNumber: 12345
homeDirectory: /home_local/maxldap/
gecos: maxldap_gecos-field
description: Not Available
localityName: I dont know
dn: cn=maxldap,ou=Group,dc=example,dc=com
objectClass: posixGroup
objectClass: top
cn: maxldap
gidNumber: 12345
To add this to the running slapd-LDAP-server's database, run the following:
$ ldapadd -f basic-test-user.ldif -D "cn=admin,dc=example,dc=com" -W -x Enter LDAP Password: adding new entry "ou=People,dc=example,dc=at" adding new entry "ou=Group,dc=example,dc=com" adding new entry "uid=maxldap,ou=People,dc=example,dc=com" adding new entry "cn=maxldap,ou=Group,dc=example,dc=com"
Running "slapcat" as root on your LDAP-server, you'll notice
that some additional attributes such as "creatorsName" and "modifyTimestamp"
were added automatically.
Note: AFAIK, you should use the "slapcat" and
"slapadd" commands only when the slapd-process is stopped!
If you wanted to remove these entries again, use the following file
"basic-remove.ldif":
dn: uid=maxldap,ou=People,dc=example,dc=com changetype: delete dn: cn=maxldap,ou=Group,dc=example,dc=com changetype: delete dn: ou=People,dc=example,dc=com changetype: delete dn: ou=Group,dc=example,dc=com changetype: delete
and run the following command:
$ ldapmodify -f basic-remove.ldif -D "cn=admin,dc=subnet,dc=at" -x -W Enter LDAP Password: deleting entry "uid=maxldap,ou=People,dc=subnet,dc=at" deleting entry "cn=maxldap,ou=Group,dc=subnet,dc=at" deleting entry "ou=People,dc=subnet,dc=at" deleting entry "ou=Group,dc=subnet,dc=at"
# apt-get install libnss-ldap
You are asked questions such as "is a login needed to retrieve data
from the LDAP db?" and "should the libnss-ldap configuration file be
readable and writable only by the file owner?", which is all more
than interesting and could be necessary if you use a non-Debian-default
setup. (This might be used to harden the installation later, but at
the moment, we use the defaults...)
(From one of those Debconf-dialogs: "Note: As a sanity check, libnss-ldap
will check if you have nscd installed and will only set the mode to 0600
if nscd is present." Thus, it might really be a good idea to use "nscd"!
See
http://homex.subnet.at/~max/ldap/index.php#nss-install,
section "NSCD and /etc/libnss-ldap.conf" for more details!)
The example-file /usr/share/doc/libnss-ldap/examples/nsswitch.ldap
holds really good information for decent configuration of our
/etc/nsswitch.conf.
Nevertheless, we'll stick with the basics
at the moment and just change the existing /etc/nsswitch.conf
a little bit - after making a backup of it:
# cp /etc/nsswitch.conf /etc/nsswitch.conf_05-01-05
# $EDIT /etc/nsswitch.conf
[...]
passwd: ldap compat
group: ldap compat
shadow: ldap compat
[...]
You should now be able to see the user via the NSS library calls:
# finger maxldap Login: maxldap Name: maxldap_gecos-field Directory: /home_local/maxldap/ Shell: /bin/bash Never logged in. No mail. No Plan. # getent passwd|grep maxldap maxldap:x:12345:12345:maxldap_gecos-field:/home_local/maxldap/:/bin/bash
Great.
In order to be able to authenticate against the LDAP server using the user's password, we need to adapt the PAM service:
# apt-get install libpam-ldap
I basically used the same choices are as mentioned in
http://people.debian.org/~torsten/ldapnss.html,
as described as follows.
(Note: You could choose to use "MD5" password hashes here!?
Again, this sounds like it would be a good idea, but we'll
stick with "crypt" for the moment though...)
I adapted common-account, common-auth and
common-password -- slightly different changes each:
# /etc/pam.d/common-account - authorization settings common to all services # markus -- 05-01-05 # To activate LDAP support, comment the default and add the LDAP config # markus -- 06-08-05 # With "use_first_pass", root cannot change the password anymore (affects common-password) # It seems to have been replaced with "try_first_pass". #account required pam_unix.so account sufficient pam_ldap.so account required pam_unix.so try_first_pass # /etc/pam.d/common-auth - authentication settings common to all services # markus -- 05-01-05 # To activate LDAP support, comment the default and add the LDAP config # markus -- 06-08-05 # With "use_first_pass", root cannot change the password anymore (affects common-password) # It seems to have been replaced with "try_first_pass". #auth required pam_unix.so nullok_secure auth sufficient pam_ldap.so auth required pam_unix.so nullok_secure try_first_pass # /etc/pam.d/common-password - password-related modules common to all services # markus -- 05-01-05 # To activate LDAP support, comment the default and add the LDAP config # markus -- 06-08-05 # With "use_first_pass", root cannot change the password anymore (affects common-password) # It seems to have been replaced with "try_first_pass". #password required pam_unix.so nullok obscure min=4 max=8 md5 password sufficient pam_ldap.so password required pam_unix.so nullok obscure min=4 max=8 md5 try_first_pass
(Note: As mentioned in Torsten's Howto, common-session
goes unchanged... At the moment I do not know why?
Shouldn't we make the ldap-changes there too?)
It is now possible to log in on the command-line using NIS-users (correct
password: accept; wrong password; reject) as well as the maxldap-LDAP-user!! :)
"su" and "ssh" work too!
(Note: For "ssh" to work properly, you have to restart the ssh-service first!)
In order to get the "slapd" process to run as a different user and
group than root, check out "/etc/default/slapd" first
of all.
According to /usr/share/doc/debian-policy/policy.txt.gz
(package "debian-policy"), section "9.2.2. UID and GID classes",
the system-UIDs 100-999 can be assigned for system-purposes on a
dynamical basis. Only 0-99 must not be used on a
per-machine-basis!
Thus, create the group and user as follows:
# addgroup --system ldap # adduser --system --no-create-home --group ldap
Check /etc/passwd and /etc/group. There should
be a group called "ldap", as well as a "ldap"-user with the GID of the
just mentioned group. Both IDs should be between 100-999.
After adding "ldap" to SLAPD_USER and SLAPD_GROUP in
/etc/default/slapd, trying to restart the slapd-process will
result in error. (Check /var/log/syslog for more
information.)
You need to enable "ldap" to read the config-file:
# chown ldap /etc/ldap/slapd.conf
Next, change the ownership of the files under /var/:
[<0> root@peach ldap]# ll /var/lib/ldap/ -d drwxr-xr-x 2 root root 4096 Jan 3 15:04 /var/lib/ldap/ [<0> root@peach ldap]# ll /var/lib/ldap/ -a total 540 drwxr-xr-x 2 root root 4096 Jan 3 15:04 . drwxr-xr-x 16 root root 4096 Jan 3 15:04 .. -rw------- 1 root root 8192 Jan 3 15:04 __db.001 -rw------- 1 root root 270336 Jan 3 15:04 __db.002 -rw------- 1 root root 98304 Jan 3 15:04 __db.003 -rw------- 1 root root 368640 Jan 3 15:04 __db.004 -rw------- 1 root root 16384 Jan 3 15:04 __db.005 -rw------- 1 root root 8192 Jan 7 16:31 dn2id.bdb -rw------- 1 root root 32768 Jan 7 16:31 id2entry.bdb -rw------- 1 root root 97140 Jan 7 16:31 log.0000000001 -rw------- 1 root root 12288 Jan 7 16:31 objectClass.bdb [<0> root@peach ldap]# ll /var/lib/slapd/ -d drwxr-xr-x 2 root root 4096 Jan 3 15:04 /var/lib/slapd/ [<0> root@peach ldap]# ll /var/lib/slapd/ -a total 8 drwxr-xr-x 2 root root 4096 Jan 3 15:04 . drwxr-xr-x 16 root root 4096 Jan 3 15:04 .. -rw-r--r-- 1 root root 0 Jan 3 15:04 suffix_change [<0> root@peach ldap]# ll /var/run/slapd/ -d drwxr-xr-x 2 root root 4096 Jan 7 16:31 /var/run/slapd/ [<0> root@peach ldap]# ll /var/run/slapd/ -a total 8 drwxr-xr-x 2 root root 4096 Jan 7 16:31 . drwxr-xr-x 6 root root 4096 Jan 7 16:31 .. # chown ldap /var/run/ldap/ -R # chown ldap /var/lib/slapd/ -R # chown ldap /var/run/slapd/ -R
Starting slapd again should work now (# /etc/init.d/slapd start),
and it should run as "ldap"-user now instead of "root":
# ps aux|grep slapd ldap 2039 0.0 0.5 32916 4480 ? Ss 16:39 0:00 /usr/sbin/slapd -g ldap -u ldap [...]
Apart from updating these notes to the actual Debian 3.1 release versions ... the following steps are some of those that needed to be performed next:
/etc/default/slapd: Activate "SSL"-startup-option
there (and NOT in /etc/init.d/slapd itself)!Ilja has sent me some feedback on a pre-release version Debian Etch (January 2007), whereas most of the stuff above works on Etch as well. Two steps needed to be adapted though to have slapd run under the ldap user:
"chown ldap /var/lib/ldap -R" (instead of "chown ldap /var/run/ldap -R")"/etc/default/slapd" to set the flag TRY_BDB_RECOVERY=no,
because otherwise some files under /var/run/ldap are assigned to the root user again.
This seems to be a bug in the start script of slapd.I would be glad to hear about your opinion, any corrections or additions. (The form is at the end of this file.)