LDAP

Project: LDAP
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State	Active
Members	Stuiterveer
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Description	LDAP server for central logins using passwords or keypairs
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LDAP installation so we can use space-wide logins instead of seperate logins for every computer/server.

NOTE: Currently logging in doesn't add you to any additional groups besides the group(s) that the user was added to in LDAP. This means sudo and other things are not (yet) possible with LDAP logins.

Server

Server IP is 192.168.1.177. The server uses an installation of OpenLDAP with phpLDAPAdmin. The following settings were applied:

OpenLDAP

• DNS domain name: ackspace.nl ("dc=ackspace,dc=nl")
• Database backend: HDB

phpLDAPAdmin

/etc/phpldapadmin/config.php

The following values were set/changed in /etc/phpldapadmin/config.php:

$servers->setValue('server','host','0.0.0.0');
$servers->setValue('server','base',array('dc=ackspace,dc=nl'));
$config->custom->appearance['hide_template_warning'] = true;
$servers->setValue('login','bind_id','cn=admin,dc=ackspace,dc=nl');

SSH keys

A field to insert SSH keys for users is not present in OpenLDAP/phpLDAPAdmin by default, for this I created a file called openssh-lpk.ldif with the following content:

dn: cn=openssh-lpk,cn=schema,cn=config
objectClass: olcSchemaConfig
cn: openssh-lpk
olcAttributeTypes: ( 1.3.6.1.4.1.24552.500.1.1.1.13 NAME 'sshPublicKey'
  DESC 'MANDATORY: OpenSSH Public key'
  EQUALITY octetStringMatch
  SYNTAX 1.3.6.1.4.1.1466.115.121.1.40 )
olcObjectClasses: ( 1.3.6.1.4.1.24552.500.1.1.2.0 NAME 'ldapPublicKey' SUP top AUXILIARY
  DESC 'MANDATORY: OpenSSH LPK objectclass'
  MAY ( sshPublicKey $ uid )
  )

The following command was then used to add support (make sure ldapscripts is installed):

ldapadd -Y EXTERNAL -H ldapi:/// -f openssh-lpk.ldif

/etc/phpldapadmin/templates/creation/posixAccount.xml

Finally the User Account creation template was changed to add an SSH public key input field to the form by default. For this, /etc/phpldapadmin/templates/creation/posixAccount.xml was changed to the following:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE template SYSTEM "template.dtd">

<template>
<askcontainer>1</askcontainer>
<description>New User Account</description>
<icon>ldap-user.png</icon>
<invalid>0</invalid>
<rdn>cn</rdn>
<title>Generic: User Account</title>
<visible>1</visible>

<objectClasses>
<objectClass id="inetOrgPerson"></objectClass>
<objectClass id="posixAccount"></objectClass>
<objectClass id="ldapPublicKey"></objectClass>
</objectClasses>

<attributes>
<attribute id="givenName">
    <display>First name</display>
    <icon>ldap-uid.png</icon>
    <onchange>=autoFill(cn;%givenName% %sn%)</onchange>
    <onchange>=autoFill(uid;%givenName|0-1/l%%sn/l%)</onchange>
    <order>1</order>
    <page>1</page>
</attribute>
<attribute id="sn">
    <display>Last name</display>
    <onchange>=autoFill(cn;%givenName% %sn%)</onchange>
    <onchange>=autoFill(uid;%givenName|0-1/l%%sn/l%)</onchange>
    <order>2</order>
    <page>1</page>
</attribute>
<attribute id="cn">
    <display>Common Name</display>
    <order>3</order>
    <page>1</page>
</attribute>
<attribute id="uid">
    <display>User ID</display>
    <onchange>=autoFill(homeDirectory;/home/users/%uid%)</onchange>
    <order>4</order>
    <page>1</page>
    <spacer>1</spacer>
</attribute>
<attribute id="homeDirectory">
    <display>Home directory</display>
    <order>8</order>
    <page>1</page>
</attribute>
<attribute id="uidNumber">
    <display>UID Number</display>
    <icon>terminal.png</icon>
    <order>6</order>
    <page>1</page>
    <readonly>1</readonly>
    <value>=php.GetNextNumber(/;uidNumber)</value>
</attribute>
<attribute id="gidNumber">
    <display>GID Number</display>
    <order>7</order>
    <page>1</page>
    <value><![CDATA[=php.PickList(/;(&(objectClass=posixGroup));gidNumber;%cn%;;;;cn)]]></value>
</attribute>
<attribute id="loginShell">
    <display>Login shell</display>
    <order>9</order>
    <page>1</page>
    <type>select</type>
    <value id="/bin/bash">/bin/bash</value>
    <value id="/bin/sh">/bin/sh</value>
    <value id="/bin/csh">/bin/csh</value>
    <value id="/bin/tsh">/bin/tsh</value>
</attribute>
<attribute id="userPassword">
    <display>Password</display>
    <icon>lock.png</icon>
    <order>5</order>
    <page>1</page>
    <post>=php.PasswordEncrypt(%enc%;%userPassword%)</post>
    <spacer>1</spacer>
    <verify>1</verify>
</attribute>
<attribute id="sshPublicKey">
        <display>SSH public key</display>
        <icon>lock.png</icon>
        <order>10</order>
        <page>1</page>
</attribute>
</attributes>

</template>

Client

To obtain a user on the LDAP server, contact Stuiterveer.

PAM

To use LDAP to sign in to Linux, install libpam-ldapd. When asked, fill in the details mentioned in LDAP#OpenLDAP.

/etc/nsswitch.conf

Make sure LDAP is enabled for passwd, group and shadow. To verify, check to see if the following is present (edit the existing entries if needed) in /etc/nsswitch.conf:

passwd:         ldap compat
group:          ldap compat
shadow:         ldap compat

This will first check LDAP for entries, otherwise it will check locally. If preferred, you can switch around compat and ldap to first check locally and revert to LDAP on failure.

Home folder creation

If you want to make sure a user folder is created upon login, add the following to the end of /etc/pam.d/common-session:

session required        pam_mkhomedir.so skel=/etc/skel umask=0022

SSH key login

Create a file that has the following content:

#!/bin/bash
ldapsearch -h 192.168.1.177 -b "dc=ackspace,dc=nl" -x '(&(objectClass=posixAccount)(uid='"$1"'))' 'sshPublicKey' | sed -n '/^ /{H;d};/sshPublicKey:/x;$g;s/\n *//g;s/sshPublicKey: //gp'

Make sure the file and all folders above it are owned by root:root and have umask 022.

Then edit sshd_config to include the following:

AuthorizedKeysCommand /path/to/file
AuthorizedKeysCommandUser nobody

Restart services

When you restart the nscd and ssh services you will be up and running. Sign in to the computer/VM with your LDAP account to verify that it works.