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## Auto-converted by kwiki2moinmoin v2005-10-07
= Configuring LDAP Authentication for Debian =
== OpenLDAPSetup ==
1. Install the ["OpenLDAP"] package [http://packages.debian.org/cgi-bin/search_packages.pl?searchon=names&keywords=slapd slapd]
## page was renamed from OpenLDAPSetup
= Setting up an LDAP server with OpenLDAP =
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Do '{{{apt-get install slapd}}}', answering prompts as required and generaly picking defaults except where they are obviously examples. == Install the OpenLDAP package slapd ==
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2. Edit the LDAP configuration file Install the package with:
{{{
  # apt-get install slapd
}}}
answering the prompts as follows:
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To make using LDAP utilities like '{{{ldapsearch}}}' a little less painful, edit {{{/etc/ldap/ldap.conf}}} (installed by the '{{{libldap2}}}' package on the stable (a.k.a. 'woody') distribution) to set:{{{
 BASE dc=<yourhost>,dc=<your>,dc=<domain>
 URI ldap://localhost
Note: if you don't get these options use {{{dpkg-reconfigure -plow slapd}}} after installation. With the latest version, it only asks you for admin user password and none of the rest, because the DNS domain name is taken from configured machine FQDN name.

 * For the DNS domain name, enter your domain name. This will be translated to an LDAP DN (for example, '{{{example.com}}}' would become '{{{dc=example, dc=com}}}'). This becomes what is known as your ''BaseDN'', the root of your database.
 * For your organization you can enter any string; this becomes associated to the '{{{o}}}' field of your ''BaseDN'' record.
 * Next enter your LDAP administrator password twice. This will set the password for '{{{cn=admin, BaseDN}}}' and give '{{{cn=admin, BaseDN}}}' write access to everything in your LDAP tree.
 * Accept the default of {{{No}}} to the question {{{Allow LDAPv2}}} protocol.
 * Use the default database backend.

For querying the LDAP server utilities like {{{ldapsearch}}} are available. See the [[LDAP/LDAPUtils]] topic for more details.

== Missing slapd.conf? ==
Since version 2.4.23-3 the configuration of OpenLDAP has been changed to /etc/ldap/slapd.d by default. The OpenLDAP packages in Debian provide an automatic migration to the new configuration style. With the new configuration style it is possible to change values on the fly without restarting slapd. Changes are made through the use of ldif files and ldap{add,modify}. In Debian you can use the following command to search the configuration:

      ldapsearch -Y EXTERNAL -H ldapi:/// -b "cn=config"

  To modify configuration use the command:

      ldapmodify -Y EXTERNAL -H ldapi:/// -f <file.ldif>

For configuration options see the several manpages that exist or the documentation provided upstream.

The use of slapd.conf remains possible (optional).

== For better performance do more indexing than the default. ==

Modify {{{/etc/ldap/slapd.conf}}} to contain the following:
{{{
index objectClass eq
index cn pres,sub,eq
index sn pres,sub,eq
index uid pres,sub,eq
index displayName pres,sub,eq
index default sub
index uidNumber eq
index gidNumber eq
index mail,givenName eq,subinitial
index dc eq
Line 15: Line 51:
3. Tune your LDAP server performance

To improve LDAP performance, edit {{{/etc/ldap/slapd.conf}}} to set more indexes than the stable (a.k.a. 'woody') default of just objectClass (taken from the Mandrake documentation):{{{
  index objectClass,uid,uidNumber,gidNumber eq
  index cn,mail,surname,givenName eq,subinitial
After any new indexes have been defined or other major database changes have been made (e.g. {{{slapadd}}} was used) it is best to recreate the indexes. Note that you should stop {{{slapd}}} before recreating the indexes and should fix the permissions afterward.
{{{
  # /etc/init.d/slapd stop
  # slapindex
  # chown -R openldap:openldap /var/lib/ldap
  # /etc/init.d/slapd start
Line 22: Line 59:
4. Update the LDAP indexes == Configuring 'chsh' and 'chfn' to work with LDAP ==
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Make sure the indexes are updated by doing (as {{{root}}}):{{{
  # /etc/init.d/slapd stop
  # slapindex
  # /etc/init.d/slapd start
Edit '{{{/etc/ldap/slapd.conf}}}' to allow access for users to update their {{{loginShell}}} and {{{gecos}}} entries by adding the following before the '{{{access to *}}}' entry:

{{{
access to attrs=loginShell,gecos
      by dn="cn=admin,dc=example,dc=com" write
      by self write
      by * read
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== For SAMBA LDAP support ==

For Samba LDAP, slapd needs the Samba schema. The Debian package seems to have a samba.schema file which is old and out of date, and a samba.schema.gz file which is actually the correct one. Do the following (as {{{root}}}):
{{{
  # zcat /usr/share/doc/samba-doc/examples/LDAP/samba.schema.gz > /etc/ldap/schema/samba.schema
}}}

Now add the following line to /etc/ldap/slapd.conf after the other includes:
{{{
include /etc/ldap/schema/samba.schema
}}}

And restart slapd:
{{{
  # /etc/init.d/slapd restart
}}}

== Access controls for subtree-specific LDAP Admins ==

If you choose to use LDAP for many functions, such as having a single server for DNS, Authentication, and networking flat file database replacement, you may wish to have LDAP administrative users for each subtree in addition to the global admin ({{{dn="cn=admin, dc=example, dc=com}}}). The following example is useful when using a separate authentication tree which includes Samba.

{{{
 # The manager dn has full write access to the auth subtree
 # Everyone else has read access to not otherwise protected fields and entries
 access to dn.sub="ou=auth,dc=example,dc=com"
         by dn="cn=Manager,ou=auth,dc=example,dc=com" write
         by * read
}}}

== Configuring LDAPS ==

Configuring the certificate (and possibly the CA used) in /etc/ldap/slapd.conf:

{{{
TLSCACertificateFile /etc/ssl/certs/whaterver_ca_you_use.pem
TLSCertificateKeyFile /etc/ssl/private/example.com.pem.pem
TLSCertificateFile /etc/ssl/certs/example.com.pem
}}}

By default, slapd runs as user/group openldap, so it can't read the key file. On Debian Lenny, the preferred solution to this dilemma seems to be to chown the key to root:ssl-cert, set permissions to 640 and add the user openldap to group ssl-cert.

=== Symptoms: ===
In {{{slapd}}} debug output:
{{{
[...] TLS: could not set cipher list HIGH:MEDIUM:-SSLv2. (or similar)
}}}
In /var/log/syslog:
{{{
[...] main: TLS init def ctx failed: -1
}}}

==== Diagnosis: ====
If you try to install the OpenLDAP server ({{{slapd}}}) with Debian Lenny, it comes compiled against the GnuTLS library. It means you cannot use an OpenSSL style directive like {{{TLSCipherSuite HIGH:MEDIUM:-SSLv2}}} in {{{slapd.conf}}}.

In squeeze I had a similar error in log:
{{{
main: TLS init def ctx failed: -1
}}}
which was solved by:
{{{
usermod -a -G ssl-cert openldap
}}}
 

==== Cure: ====
In {{{/etc/ldap/slapd.conf}}}, either comment out `TLSCipherSuite` option to let gnutls choose rather sane default for you, or use something like:
{{{
TLSCipherSuite NORMAL
}}}
To get all the supported GnuTLS cipher suite names:
{{{
# aptitude install gnutls-bin
# man gnutls-cli
}}}
And skip to `TLS/SSL control options` section of man page.

To use only 256 bit cyphers, use this (paranoiac?) setting:
{{{
TLSCipherSuite SECURE256:!AES-128-CBC:!ARCFOUR-128:!CAMELLIA-128-CBC:!3DES-CBC:!CAMELLIA-128-CBC
}}}

Another useful tool to test server-supported TLS options is to use `gnutls-cli-debug`. First add `ldaps:///` string to the `SLAPD_SERVICES` option in `/etc/default/slapd`, restart `slapd` and then run
{{{
gnutls-cli-debug -p 636 <fqdn_of_you_ldap_host>
}}}
That will show you cryptographic suits your LDAP server supports.


=== Symptoms (round 2) ===
If you are getting messages such as
{{{
slapd TLS: can't connect: A TLS packet with unexpected length was received..
}}}
or
{{{
Could not negotiate a supported cipher suite.
}}}
take a wander by this.

==== Diagnosis: ====
How did you generate your certificates? If you generated them using OpenSSL, you're going to run into problems. Debian switched over to using gnutls a while ago, and it doesn't play nice with OpenSSL certificates. So, to fix this, check out the next section.

NOTE: On Debian Squeeze openldap is linked with gnutls as well, but works just fine with certificate generated by openssl.

==== Procedure: ====
You're going to need the gnutls certificate generator: [[http://www.gnu.org/software/gnutls/manual/html_node/Invoking-certtool.html|certtool]].

Run these two commands to generate a new self-signed key (into the current working directory):
{{{
certtool --generate-privkey --outfile ca-key.pem
certtool --generate-self-signed --load-privkey ca-key.pem --outfile ca-cert.pem
}}}

Then, update your certificate locations in /etc/ldap/slapd.conf ({{{TLSCertificateFile}}} points to ca-cert.pem and {{{TLSCertificateKeyFile}}} points to ca-key.pem), comment out {{{TLSCACertificateFile}}}, and change {{{TLSVerifyClient}}} to {{{never}}}.

In /etc/ldap/ldap.conf, comment out {{{TLS_CACERT}}} and change {{{TLS_REQCERT}}} to {{{never}}}.

Since the certificate is self-signed, we can't have gnutls trying to verify it (hence the {{{never}}}), otherwise it will never run.

Then restart your services, and you're good (assuming all your links point properly to ldaps://url/).
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 * ["LDAPAuthentication"] CategorySystemAdministration

Setting up an LDAP server with OpenLDAP

Install the OpenLDAP package slapd

Install the package with:

  # apt-get install slapd

answering the prompts as follows:

Note: if you don't get these options use dpkg-reconfigure -plow slapd after installation. With the latest version, it only asks you for admin user password and none of the rest, because the DNS domain name is taken from configured machine FQDN name.

  • For the DNS domain name, enter your domain name. This will be translated to an LDAP DN (for example, 'example.com' would become 'dc=example, dc=com'). This becomes what is known as your BaseDN, the root of your database.

  • For your organization you can enter any string; this becomes associated to the 'o' field of your BaseDN record.

  • Next enter your LDAP administrator password twice. This will set the password for 'cn=admin, BaseDN' and give 'cn=admin, BaseDN' write access to everything in your LDAP tree.

  • Accept the default of No to the question Allow LDAPv2 protocol.

  • Use the default database backend.

For querying the LDAP server utilities like ldapsearch are available. See the LDAP/LDAPUtils topic for more details.

Missing slapd.conf?

Since version 2.4.23-3 the configuration of OpenLDAP has been changed to /etc/ldap/slapd.d by default. The OpenLDAP packages in Debian provide an automatic migration to the new configuration style. With the new configuration style it is possible to change values on the fly without restarting slapd. Changes are made through the use of ldif files and ldap{add,modify}. In Debian you can use the following command to search the configuration:

  • ldapsearch -Y EXTERNAL -H ldapi:/// -b "cn=config"
  • To modify configuration use the command:
    • ldapmodify -Y EXTERNAL -H ldapi:/// -f <file.ldif>

For configuration options see the several manpages that exist or the documentation provided upstream.

The use of slapd.conf remains possible (optional).

For better performance do more indexing than the default.

Modify /etc/ldap/slapd.conf to contain the following:

index   objectClass             eq
index   cn                      pres,sub,eq
index   sn                      pres,sub,eq
index   uid                     pres,sub,eq
index   displayName             pres,sub,eq
index   default                 sub
index   uidNumber               eq
index   gidNumber               eq
index   mail,givenName          eq,subinitial
index   dc                      eq

After any new indexes have been defined or other major database changes have been made (e.g. slapadd was used) it is best to recreate the indexes. Note that you should stop slapd before recreating the indexes and should fix the permissions afterward.

  # /etc/init.d/slapd stop
  # slapindex
  # chown -R openldap:openldap /var/lib/ldap
  # /etc/init.d/slapd start

Configuring 'chsh' and 'chfn' to work with LDAP

Edit '/etc/ldap/slapd.conf' to allow access for users to update their loginShell and gecos entries by adding the following before the 'access to *' entry:

access to attrs=loginShell,gecos
      by dn="cn=admin,dc=example,dc=com" write
      by self write
      by * read

For SAMBA LDAP support

For Samba LDAP, slapd needs the Samba schema. The Debian package seems to have a samba.schema file which is old and out of date, and a samba.schema.gz file which is actually the correct one. Do the following (as root):

  # zcat /usr/share/doc/samba-doc/examples/LDAP/samba.schema.gz > /etc/ldap/schema/samba.schema

Now add the following line to /etc/ldap/slapd.conf after the other includes:

include /etc/ldap/schema/samba.schema

And restart slapd:

  # /etc/init.d/slapd restart

Access controls for subtree-specific LDAP Admins

If you choose to use LDAP for many functions, such as having a single server for DNS, Authentication, and networking flat file database replacement, you may wish to have LDAP administrative users for each subtree in addition to the global admin (dn="cn=admin, dc=example, dc=com). The following example is useful when using a separate authentication tree which includes Samba.

 # The manager dn has full write access to the auth subtree
 # Everyone else has read access to not otherwise protected fields and entries
 access to dn.sub="ou=auth,dc=example,dc=com"
         by dn="cn=Manager,ou=auth,dc=example,dc=com" write
         by * read

Configuring LDAPS

Configuring the certificate (and possibly the CA used) in /etc/ldap/slapd.conf:

TLSCACertificateFile    /etc/ssl/certs/whaterver_ca_you_use.pem
TLSCertificateKeyFile   /etc/ssl/private/example.com.pem.pem
TLSCertificateFile      /etc/ssl/certs/example.com.pem

By default, slapd runs as user/group openldap, so it can't read the key file. On Debian Lenny, the preferred solution to this dilemma seems to be to chown the key to root:ssl-cert, set permissions to 640 and add the user openldap to group ssl-cert.

Symptoms:

In slapd debug output:

[...] TLS: could not set cipher list HIGH:MEDIUM:-SSLv2.  (or similar)

In /var/log/syslog:

[...] main: TLS init def ctx failed: -1

Diagnosis:

If you try to install the OpenLDAP server (slapd) with Debian Lenny, it comes compiled against the GnuTLS library. It means you cannot use an OpenSSL style directive like TLSCipherSuite HIGH:MEDIUM:-SSLv2 in slapd.conf.

In squeeze I had a similar error in log:

main: TLS init def ctx failed: -1

which was solved by:

usermod -a -G ssl-cert openldap

Cure:

In /etc/ldap/slapd.conf, either comment out TLSCipherSuite option to let gnutls choose rather sane default for you, or use something like:

TLSCipherSuite NORMAL

To get all the supported GnuTLS cipher suite names:

# aptitude install gnutls-bin
# man gnutls-cli

And skip to TLS/SSL control options section of man page.

To use only 256 bit cyphers, use this (paranoiac?) setting:

TLSCipherSuite SECURE256:!AES-128-CBC:!ARCFOUR-128:!CAMELLIA-128-CBC:!3DES-CBC:!CAMELLIA-128-CBC

Another useful tool to test server-supported TLS options is to use gnutls-cli-debug. First add ldaps:/// string to the SLAPD_SERVICES option in /etc/default/slapd, restart slapd and then run

gnutls-cli-debug -p 636 <fqdn_of_you_ldap_host>

That will show you cryptographic suits your LDAP server supports.

Symptoms (round 2)

If you are getting messages such as

slapd TLS: can't connect: A TLS packet with unexpected length was received..

or

Could not negotiate a supported cipher suite.

take a wander by this.

Diagnosis:

How did you generate your certificates? If you generated them using OpenSSL, you're going to run into problems. Debian switched over to using gnutls a while ago, and it doesn't play nice with OpenSSL certificates. So, to fix this, check out the next section.

NOTE: On Debian Squeeze openldap is linked with gnutls as well, but works just fine with certificate generated by openssl.

Procedure:

You're going to need the gnutls certificate generator: certtool.

Run these two commands to generate a new self-signed key (into the current working directory):

certtool --generate-privkey --outfile ca-key.pem
certtool --generate-self-signed --load-privkey ca-key.pem --outfile ca-cert.pem

Then, update your certificate locations in /etc/ldap/slapd.conf (TLSCertificateFile points to ca-cert.pem and TLSCertificateKeyFile points to ca-key.pem), comment out TLSCACertificateFile, and change TLSVerifyClient to never.

In /etc/ldap/ldap.conf, comment out TLS_CACERT and change TLS_REQCERT to never.

Since the certificate is self-signed, we can't have gnutls trying to verify it (hence the never), otherwise it will never run.

Then restart your services, and you're good (assuming all your links point properly to ldaps://url/).


CategorySystemAdministration