The latest version of this document can be found at
http://pobox.com/~bcwhite/ldap-upgrade.txt
Last Updated: 2006-05-23
I just upgraded our company's network from a system created 6 years ago
(NIS and SMBPASSWD) to an up-to-date one (for 2006, at least) including
a central LDAP server. It was a far from painless experience, so I
thought I'd write up the experience in the hope that it may help others.
If I've left anything out, please let me know.
mailto:bcwhite@precidia.com (or if I've left there,
mailto:bcwhite@pobox.com).
I used my own "cfile" utility (http://sf.net/projects/cfile) to manage
all the configuration files across multiple machines. I hope to package
it up for Debian soon.
Here's what I did... Note that I'm using Debian 3.1 as my installed
system.
Create an LDAP Server (apt-get install slapd)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ref: http://www.metaconsultancy.com/whitepapers/ldap.htm
http://www.tldp.org/HOWTO/LDAP-HOWTO/
http://www.grennan.com/ldap-HOWTO.html
SLAPD has to be one of the most difficult things to wrap your head
around I've ever come across. Perhaps if you spoke LDAP in your sleep,
it would all be obvious, but I've smoothed out the brick wall next to me
banging my head against it these past few days.
Getting SLAPD (v2.2.23) started wasn't much trouble. I set my suffix
(aka "base") to "dc=precidia". This would typically be
"dc=precidia,dc=com", but I'm lazy. I also set my default
password
style to SSHA (salted-SHA) and set an administrator access point. Since
I planned on disabling this access point later, I just used a basic
"crypt" to store the password.
# "secret" is password, "XX" is salt (use any two
letters or
numbers)
perl -e 'print
crypt("secret","XX"),"\n"'
XXIABNgk3eFuw
password-hash SSHA
rootdn cn=root,dc=precidia
rootpw {crypt}XXIABNgk3eFuw
Also, create all the appropriate indices for speed:
index objectClass eq
index cn pres,sub,eq
index sn pres,sub,eq
index uid pres,sub,eq
index displayName pres,sub,eq
index uidNumber eq
index gidNumber eq
index memberUid eq
index sambaSID eq
#index sambaPrimaryGroups eq
index sambaDomainName eq
index default sub
Push these changes with: /etc/init.d/slapd force-reload
In brief, LDAP is an object storage system where objects are grouped
(typcially) by an "organizationalUnit", or "ou" for short.
Of course,
you can't simply store an object specifying a new "ou=something";
you
first have to create an object that describes it. Thus, before you can
store objects in "ou=Domains" you first have to store the object:
dn: ou=Domains,dc=precidia
ou: Domains
objectClass: top
objectClass: organizationalUnit
The first line is the "distinuguished name" and is the unique
identifier
for this object. Every object has one and it details the hierarchy
under which the object is stored. In this case, my "base" (the root
of
my tree) is "dc=precidia" and the sub-tree is "Domains".
Despite the
fact that I said you cannot store an object in a "ou=Domains" without
first creating it, it is possible to create it and store it there at the
same time.
Enabing Ssecure LDAP ("ldaps") is left as an exercise to the reader!
(That means I haven't yet done it at the time this was written.)
Luckily, the LDAP Account Manager will do much of that for you...
Migrate Existing UNIX Information
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ref: http://www.linuxjournal.com/article/6266
http://www.gurulabs.com/goodies/downloads.php
http://www.gurulabs.com/downloads/ldapmigrate
For this, I used the "ldapmigrate" perl script desribed above. For
this
to run, you'll have to install "libnet-ldap-perl" and maybe a few
others. Then, on your ldap server, do:
cd /var/data/ldap
/etc/init.d/slapd stop
rm -f *
/etc/init.d/slapd start
This will give you a clean database to start from. I restarted from
this point many, many times.
Create an "admin" account for LDAP administration. It will need a
valid
password but should have an invalid shell to prevent unix login (because
it will eventually have root access -- see Samba section). A vaild home
directory may be useful, though.
Before doing the migration, I edited the "ldapmigrate" script and
changed all occurances of "Group" to "Groups" for naming
consistancy and
to match the defaults of the LDAP Account Manager.
Then do the migration...
LDAPBIND="cn=root,dc=precidia"
LDAPPASS="secret"
LDAPBASE="dc=precidia"
LDAPHOST="localhost"
ldapmigrate -D $LDAPBIND -w $LDAPPASS -b $LDAPBASE -h $LDAPHOST
--extschema --extconts --prepdb
ldapmigrate -D $LDAPBIND -w $LDAPPASS -b $LDAPBASE -h $LDAPHOST
--extschema --minuid=1001 --mingid=1000 -f /etc/passwd passwd
ldapmigrate -D $LDAPBIND -w $LDAPPASS -b $LDAPBASE -h $LDAPHOST
--extschema --minuid=1001 --mingid=1000 -f /etc/group group
It's important to use the "--extschema" so that the objects will
be
ready to accept Samba information. Your minuid/maxuid and mingid/maxgid
may be different than mine.
Add Additional Information
~~~~~~~~~~~~~~~~~~~~~~~~~~
At this point, I wrote my own Perl script using Net::LDAP to add
additional information (phone number, fax number, email, etc.) from an
internal database of that information. I also generated samba SID
information from the /etc/smbpasswd file. I'll try to make it available
for reference, but it's not likely to be directly usable by anyone. The
LDAP Account Manager should allow you to add the samba information by hand.
Install LDAP Account Manager (apt-get install ldap-account-manager)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ref: http://lam.sourceforge.net/
Before you can use this for editing, you have to get it installed.
Version 0.4.9 goes in to "apache" automatically (I think) but to use
it
with "apache2" you need to do something like:
cd /etc/apache2/sites-available
ln -s /etc/ldap-account-manager/apache.conf ldap-account-manager
cd ../sites-enabled
ln -s ../sites-available/ldap-account-manager 010-lam
/etc/init.d/apache2 restart
Then you should be able to log in with http://hostname/lam/ and get a
login page. Additional Apache configuration is left as an exercise to
the reader. Once you do get a login page...
Select the "configuration login" from the upper right corner. The
default password is "lam". You'll need to change all the suffix
parameters to match the suffix you chose when you configured slapd. I use:
UserSuffix: ou=people,dc=precidia
GroupSuffix: ou=groups,dc=precidia
HostSuffix: ou=hosts,dc=precidia
DomainSuffix: ou=domains,dc=precidia
PasswordHash: SSHA
Set the "ranges" fields to match what you want for your site. Set the
list of valid users to whatever is appropriate. I set it to:
uid=admin,ou=People,dc=precidia
Finally, create a new configuration password (it's group with the "list
of valid users" under "security settings" but it only applies to
getting
to this configuration screen) and submit the changes.
Go back to the login screen and login as "admin" with the password for
that account (_not_ the configuration password you just changed). It
should tell you that some LDAP parts are missing and offer to create
them for you. Let it do so.
Create a new domain. To get the SID for a domain you're migrating from
a legacy system, go to your legacy system and run:
net getlocalsid precidia
Don't change the "algorithmic RID base" unless you've changed
it
previously. I haven't yet discovered exactly whan the "next ...
rid"
options do so I haven't played with them, yet. I believe they allow you
to specify starting RIDs that increment normally rather that being
generated by some function of your userid/groupid.
Note: There is also a "phpldapadmin" package that provides more
detailed control of the LDAP directory, but because it's a generic
interface you have to know much more to do account management.
Configure Linux Authentication (apt-get install libnss-ldap libpam-ldap
libpam-passwdqc)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ref: http://www.metaconsultancy.com/whitepapers/ldap-linux.htm
http://www.openwall.com/passwdqc/README.shtml
In brief, this involved editing several configuration files...
/etc/nsswitch.conf:
passwd: files ldap
group: files ldap
shadow: files ldap
/etc/pam_ldap.conf:
host admin1.ott.precidia.com
base dc=precidia
ldap_version 3
rootbinddn uid=admin,ou=People,dc=precidia
pam_filter &(objectclass=posixAccount)(!(uidNumber=0))
pam_password exop
/etc/libnss-ldap.conf:
uri ldap://admin1.ott.precidia.com ldap://admin2.ott.precidia.com
base dc=precidia
/etc/pam.d/common-account:
account sufficient pam_unix.so
account sufficient pam_ldap.so
account required pam_deny.so
/etc/pam.d/common-auth:
auth sufficient pam_ldap.so
auth sufficient pam_unix.so shadow use_first_pass
auth required pam_deny.so
/etc/pam.d/common-session:
session sufficient pam_ldap.so
session required pam_unix.so
/etc/pam.d/common-password:
password requisite pam_passwdqc.so
min=12,10,10,8,6 random=25 retry=3 passphrase=2
password sufficient pam_ldap.so type=network
use_authtok first_pass
password sufficient pam_unix.so type=machine
use_authtok md5
password required pam_deny.so
Once all of this is done, you should be able to "su - user" and become
that user. Whew!
Configure Samba Authentication (apt-get install samba)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ref: http://www.unav.es/cti/ldap-smb/smb-ldap-3-howto.html
http://www.coe.tamu.edu/cs/Manuals/Samba/Samba-LDAP-HOWTO.html
http://research.imb.uq.edu.au/~l.rathbone/ldap/samba.shtml
http://www.mami.net/univr/tng-ldap/howto/
http://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/passdb.html
man smb.conf
Congratulations on getting this far! The following was done with Samba
v3.0.14a.
You'll need to import the samba scheme in to slapd.conf by adding this
line. If the file is not in /etc/ldap/schema, you'll probably find a
gzipped version here: /usr/share/doc/samba-doc/examples/LDAP/samba.schema.gz
include /etc/ldap/schema/samba.schema
Then add the following to your working smb.conf configuration file:
passdb backend = ldapsam:ldap://admin1.ott.precidia.com
ldap admin dn = uid=samba,ou=Services,dc=precidia
ldap suffix = dc=precidia
ldap user suffix = ou=People
ldap group suffix = ou=Groups
ldap idmap suffix = ou=Idmap
ldap machine suffix = ou=Hosts
ldap replication sleep = 1000
ldap password sync = true
ldapsam:trusted = true
A few notes: The man pages for version 3.0.14a indicates that the
specific suffix directives replace the default "ldap suffix". In
fact,
they simply prepend to it. Also, don't put quote marks around the values!
This configuration assumes a user "samba" created in the
"Services" unit
of the directory. You'll have to do that manually with a command like:
ldapadd -D cn=root,dc=precidia -w secret -b dc=precidia -h 10.0.1.5
dn: uid=samba,ou=Services,dc=precidia
objectClass: top
objectClass: account
objectClass: posixAccount
cn: Samba Server
uid: samba
uidNumber: 3000
gidNumber: 3000
homeDirectory: /tmp
^D
ldappasswd -x -D cn=root,dc=precidia -w secret -h 10.0.1.5 -s
SOMETHING uid=samba,ou=Services,dc=precidia
The last command sets the password for the
"uid=samba,ou=Services,dc=precidia" account to "SOMETHING".
Obviously,
choose something other than SOMETHING. Now you need to tell samba what
it is. The reason for creating a special service account with these
permissions is because it's stored on disk by samba. As such, it's not
good to use an ordinary user account which may require it's password
changed if an employee leaves or something.
smbpasswd -w SOMETHING
Finally, you have to give that account special permission in the
"slapd.conf" file so it can update records in the directory as it
runs.
To do that, change the admin rule to something like:
access to *
by dn="uid=admin,ou=People,dc=precidia" write
by dn="uid=samba,ou=Services,dc=precidia" write
by * read
At the same time, add the following so that the samba passwords are
protected. (These encrypted passwords are actually "plain text
equivalents" which means that knowing them allows access just as though
one knew the original password from which they were derived -- thank
you, Microsoft security experts.)
access to attrs=sambaLMPassword,sambaNTPassword
by dn="uid=samba,ou=Services,dc=precidia" write
by * none
Doing /etc/init.d/samba restart should start quickly. If it appears to
hang while starting "smbd" then there is probably problems accessing
the
ldap server. The /var/log/syslog file on the LDAP server may have
useful information as to what was being accessed.
If your log level is set to zero, the "smbd" process will exit quietly
on an LDAP failure. The LDAP activity found in /var/log/syslog can be
quite helpful but don't expect it to be easy.
At this point, you should be able to use Windows Explorer to browse the
samba host and access shared drives using usernames and password that
were imported in to the LDAP directory. Connecting to the domain still
needs more work, though.
Connecting to a domain needs a privileged account. I used the same
"admin" account that had its information originally imported from a
unix
account. For this to work in samba, though, _MUST_ be user-id 0 (yes,
ZERO). I understood this requrirement when samba had to create new
local accounts, but seems to still be the case for LDAP directories.
This is unfortunate as it means you have a root account in your ldap
directory, but we'll mitigate this risk as much as possible. Log out of
the LDAP Account Manager and do a "configuration login". Set the
minimum UID number to "0" (zero), submit, and login normally. Edit the
"admin" user and set the UID number to 0. Previously it was stated to
not have a valid login password for this account during the initial
migration, but set the login shell to /bin/false, too. When done change
the minimum UID back to what you want.
Lastly, you have to choose between manual or automatic addition of new
hosts. You can use the LDAP Account Manager to manually add all new
hosts before connecting them to the domain, or you can have samba create
those accounts during the first join attempt. For now, I'm just
sticking with the manual addition. There appears to be no easy way to
get samba to do it automatically. You can find instructions on how this
can be done here
http://www.nomis52.net/?section=docs&page=samldap
but configuration is complex and I was unable to get the tools to work
properly. That's annoying! This should be a built-in feature of Samba!
==============================================================================
And that's it. Wasn't that easy! You know, I love the power and
flexibility of the GNU/Linux operating system, but it took me two weeks
to figure out all of the above. There were many times I yearned for a
simple graphical setup program under Windoze.
I'm trying to help out some by writing this, but I'm afraid it will
become just one more HOWTO is the huge mess of them, none of them
complete. Writing this after the fact instead of during the process
wasn't so smart, either; I'm sure there are things I have forgotten to
mention. I have this idea of duplicating the Wikipedia site
(http://www.wikipedia.org) but making it Linux documentation. Maybe
it's already out there...
One of the drawbacks of the "bazzaar" model is that developers
concentrate on getting the software to do the things they want it to do
and not on making easy installation. After all, installation only has
to be done once, they know how to do it, and a set installation program
would only limit easy expansion of the software itself. There is
something to be said for the czar of the cathedral decreeing, "you
people over there -- go and make a good install interface so our
software will get chosen in the first place".
Brian
( bcwhite@precidia.com )
-------------------------------------------------------------------------------
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