source: branches/samba-3.2.x/docs-xml/Samba3-HOWTO/TOSHARG-SecureLDAP.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE chapter PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
<chapter id="ch-ldap-tls">
<chapterinfo>
        &author.ghenry;
        <pubdate>July 8, 2005</pubdate>
</chapterinfo>
<title>LDAP and Transport Layer Security</title>

<sect1 id="s1-intro-ldap-tls">
<title>Introduction</title>

        <para>
        <indexterm><primary>Transport Layer Seccurity, TLS</primary><secondary>Introduction</secondary></indexterm>
<indexterm><primary>ACL</primary></indexterm>
        Up until now, we have discussed the straightforward configuration of <trademark>OpenLDAP</trademark>,
        with some advanced features such as ACLs. This does not however, deal with the fact that the network
        transmissions are still in plain text. This is where <firstterm>Transport Layer Security (TLS)</firstterm>
        comes in.
        </para> 

        <para>
<indexterm><primary>RFC 2830</primary></indexterm>
        <trademark>OpenLDAP</trademark> clients and servers are capable of using the Transport Layer Security (TLS)
        framework to provide integrity and confidentiality protections in accordance with <ulink
        url="http://rfc.net/rfc2830.html">RFC 2830</ulink>; <emphasis>Lightweight Directory Access Protocol (v3):
        Extension for Transport Layer Security.</emphasis>
        </para>

        <para>
<indexterm><primary>X.509 certificates</primary></indexterm>
        TLS uses X.509 certificates. All servers are required to have valid certificates, whereas client certificates
        are optional. We will only be discussing server certificates.
        </para>

        <tip><para>
<indexterm><primary>DN</primary></indexterm>
<indexterm><primary>CN</primary></indexterm>
<indexterm><primary>FQDN</primary></indexterm>
        The DN of a server certificate must use the CN attribute to name the server, and the CN must carry the
        server's fully qualified domain name (FQDN). Additional alias names and wildcards may be present in the
        <option>subjectAltName</option> certificate extension. More details on server certificate names are in <ulink
        url="http://rfc.net/rfc2830.html">RFC2830</ulink>.
        </para></tip>

        <para>
        We will discuss this more in the next sections.
        </para>

        </sect1>

        <sect1 id="s1-config-ldap-tls">
        <title>Configuring</title>

        <para>
        <indexterm><primary>Transport Layer Seccurity, TLS</primary><secondary>Configuring</secondary></indexterm>
        Now on to the good bit.
        </para>

        <sect2 id="s1-config-ldap-tls-certs">
        <title>Generating the Certificate Authority</title>

        <para>
<indexterm><primary>Certificate Authority</primary><see>CA</see></indexterm>
        In order to create the relevant certificates, we need to become our own Certificate Authority (CA).
        <footnote><para>We could however, get our generated server certificate signed by proper CAs, like <ulink
        url="http://www.thawte.com/">Thawte</ulink> and <ulink url="http://www.verisign.com/">VeriSign</ulink>, which
        you pay for, or the free ones, via <ulink url="http://www.cacert.org/">CAcert</ulink>
        </para></footnote> This is necessary, so we can sign the server certificate.
        </para>

        <para>
<indexterm><primary>OpenSSL</primary></indexterm>
        We will be using the <ulink url="http://www.openssl.org">OpenSSL</ulink> <footnote><para>The downside to
        making our own CA, is that the certificate is not automatically recognized by clients, like the commercial
        ones are.</para></footnote> software for this, which is included with every great <trademark
        class="registered">Linux</trademark> distribution.
        </para>

        <para>
        TLS is used for many types of servers, but the instructions<footnote><para>For information straight from the
        horse's mouth, please visit <ulink
        url="http://www.openssl.org/docs/HOWTO/">http://www.openssl.org/docs/HOWTO/</ulink>; the main OpenSSL
        site.</para></footnote> presented here, are tailored for &OL;.
        </para>

        <note><para>
        The <emphasis>Common Name (CN)</emphasis>, in the following example, <emphasis>MUST</emphasis> be
        the fully qualified domain name (FQDN) of your ldap server.
        </para></note>

        <para>
        First we need to generate the CA:
<screen width="90">
<computeroutput>
&rootprompt; mkdir myCA
</computeroutput>
</screen>
        Move into that directory:
<screen width="90">
<computeroutput>
&rootprompt; cd myCA
</computeroutput>
</screen>
        Now generate the CA:<footnote><para>Your <filename>CA.pl</filename> or <filename>CA.sh</filename> might not be
        in the same location as mine is, you can find it by using the <command>locate</command> command, i.e.,
        <command>locate CA.pl</command>.  If the command complains about the database being too old, run
        <command>updatedb</command> as <emphasis>root</emphasis> to update it.</para></footnote>
<screen width="90">
<computeroutput>
&rootprompt; /usr/share/ssl/misc/CA.pl -newca
CA certificate filename (or enter to create)
  
Making CA certificate ...
Generating a 1024 bit RSA private key
.......................++++++
.............................++++++
writing new private key to './demoCA/private/cakey.pem'
Enter PEM pass phrase:
Verifying - Enter PEM pass phrase:
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:AU
State or Province Name (full name) [Some-State]:NSW
Locality Name (eg, city) []:Sydney
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Abmas
Organizational Unit Name (eg, section) []:IT
Common Name (eg, YOUR name) []:ldap.abmas.biz
Email Address []:support@abmas.biz
</computeroutput>
</screen>
        </para>

        <para>
        There are some things to note here. 
        </para>

        <orderedlist>
                <listitem>
                        <para>
                        You <emphasis>MUST</emphasis> remember the password, as we will need
                        it to sign the server certificate..
                        </para>
                </listitem>

                <listitem>
                        <para>
                        The <emphasis>Common Name (CN)</emphasis>, <emphasis>MUST</emphasis> be the
                        fully qualified domain name (FQDN) of your ldap server.
                        </para>
                </listitem>
        </orderedlist>

        </sect2>

        <sect2 id="s1-config-ldap-tls-server">
        <title>Generating the Server Certificate</title>

        <para>
        Now we need to generate the server certificate:
<screen width="90">
<computeroutput>
&rootprompt; openssl req -new -nodes -keyout newreq.pem -out newreq.pem
Generating a 1024 bit RSA private key
.............++++++
........................................................++++++
writing new private key to 'newreq.pem'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:AU
State or Province Name (full name) [Some-State]:NSW
Locality Name (eg, city) []:Sydney
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Abmas
Organizational Unit Name (eg, section) []:IT
Common Name (eg, YOUR name) []:ldap.abmas.biz
Email Address []:support@abmas.biz
  
Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:
</computeroutput>
</screen>
        </para> 

        <para>
        Again, there are some things to note here. 
        </para>         

        <orderedlist>
                <listitem>
                        <para>
                        You should <emphasis>NOT</emphasis> enter a password.
                        </para>
                </listitem>

                <listitem>
                        <para>
                        The <emphasis>Common Name (CN)</emphasis>, <emphasis>MUST</emphasis> be
                        the fully qualified domain name (FQDN) of your ldap server.
                        </para>
                </listitem>
        </orderedlist>

        <para>
        Now we sign the certificate with the new CA:
<screen width="90">
<computeroutput>
&rootprompt; /usr/share/ssl/misc/CA.pl -sign
Using configuration from /etc/ssl/openssl.cnf
Enter pass phrase for ./demoCA/private/cakey.pem:
Check that the request matches the signature
Signature ok
Certificate Details:
Serial Number: 1 (0x1)
Validity
        Not Before: Mar  6 18:22:26 2005 EDT
        Not After : Mar  6 18:22:26 2006 EDT
Subject:
        countryName               = AU
        stateOrProvinceName       = NSW
        localityName              = Sydney
        organizationName          = Abmas
        organizationalUnitName    = IT
        commonName                = ldap.abmas.biz
        emailAddress              = support@abmas.biz
X509v3 extensions:
        X509v3 Basic Constraints:
            CA:FALSE
        Netscape Comment:
            OpenSSL Generated Certificate
        X509v3 Subject Key Identifier:
            F7:84:87:25:C4:E8:46:6D:0F:47:27:91:F0:16:E0:86:6A:EE:A3:CE
        X509v3 Authority Key Identifier:
            keyid:27:44:63:3A:CB:09:DC:B1:FF:32:CC:93:23:A4:F1:B4:D5:F0:7E:CC
            DirName:/C=AU/ST=NSW/L=Sydney/O=Abmas/OU=IT/
                                                CN=ldap.abmas.biz/emailAddress=support@abmas.biz
            serial:00

Certificate is to be certified until Mar  6 18:22:26 2006 EDT (365 days)
Sign the certificate? [y/n]:y


1 out of 1 certificate requests certified, commit? [y/n]y
Write out database with 1 new entries
Data Base Updated
Signed certificate is in newcert.pem
</computeroutput>
</screen>
        </para>

        <para>
        That completes the server certificate generation. 
        </para>

        </sect2>

        <sect2 id="s1-config-ldap-tls-install">
        <title>Installing the Certificates</title>

        <para>
        Now we need to copy the certificates to the right configuration directories,
        rename them at the same time (for convenience), change the ownership and
        finally the permissions:
<screen width="90">
<computeroutput>
&rootprompt; cp demoCA/cacert.pem /etc/openldap/
&rootprompt; cp newcert.pem /etc/openldap/servercrt.pem
&rootprompt; cp newreq.pem /etc/openldap/serverkey.pem
&rootprompt; chown ldap.ldap /etc/openldap/*.pem
&rootprompt; chmod 640 /etc/openldap/cacert.pem;
&rootprompt; chmod 600 /etc/openldap/serverkey.pem
</computeroutput>
</screen>
        </para>

        <para>
        Now we just need to add these locations to <filename>slapd.conf</filename>,
        anywhere before the <option>database</option> declaration as shown here:
<screen width="90">
<computeroutput>
TLSCertificateFile /etc/openldap/servercrt.pem
TLSCertificateKeyFile /etc/openldap/serverkey.pem
TLSCACertificateFile /etc/openldap/cacert.pem
</computeroutput>
</screen>
        </para>

        <para>
        Here is the declaration and <filename>ldap.conf</filename>:
<filename>ldap.conf</filename>
<screen width="90">
<computeroutput>
TLS_CACERT /etc/openldap/cacert.pem
</computeroutput>
</screen>
        </para>

        <para>
        That's all there is to it. Now on to <xref linkend="s1-test-ldap-tls"></xref>
        </para>

        </sect2>

</sect1>

<sect1 id="s1-test-ldap-tls">
<title>Testing</title>

<para>
<indexterm><primary>Transport Layer Security, TLS</primary><secondary>Testing</secondary></indexterm>
This is the easy part. Restart the server:
<screen width="90">
<computeroutput>
&rootprompt; /etc/init.d/ldap restart
Stopping slapd:                                            [  OK  ]
Checking configuration files for slapd: config file testing succeeded
Starting slapd:                                            [  OK  ]
</computeroutput>
</screen>
        Then, using <command>ldapsearch</command>, test an anonymous search with the
        <option>-ZZ</option><footnote><para>See <command>man ldapsearch</command></para></footnote> option:
<screen width="90">
<computeroutput>
&rootprompt; ldapsearch -x -b "dc=ldap,dc=abmas,dc=biz" \
        -H 'ldap://ldap.abmas.biz:389' -ZZ
</computeroutput>
</screen>
        Your results should be the same as before you restarted the server, for example:
<screen width="90">
<computeroutput>
&rootprompt; ldapsearch -x -b "dc=ldap,dc=abmas,dc=biz" \
    -H 'ldap://ldap.abmas.biz:389' -ZZ

# extended LDIF
#
# LDAPv3
# base &lt;&gt; with scope sub
# filter: (objectclass=*)
# requesting: ALL
#

# abmas.biz
dn: dc=ldap,dc=abmas,dc=biz
objectClass: dcObject
objectClass: organization
o: Abmas
dc: abmas

# Manager, ldap.abmas.biz
dn: cn=Manager,dc=ldap,dc=abmas,dc=biz
objectClass: organizationalRole
cn: Manager

# ABMAS, abmas.biz
dn: sambaDomainName=ABMAS,dc=ldap,dc=abmas,dc=biz
sambaDomainName: ABMAS
sambaSID: S-1-5-21-238355452-1056757430-1592208922
sambaAlgorithmicRidBase: 1000
objectClass: sambaDomain
sambaNextUserRid: 67109862
sambaNextGroupRid: 67109863
</computeroutput>
</screen>
        If you have any problems, please read <xref linkend="s1-int-ldap-tls"></xref>
</para>

</sect1>

<sect1 id="s1-int-ldap-tls">
<title>Troubleshooting</title>

<para>
<indexterm><primary>Transport Layer Security, TLS</primary><secondary>Troubleshooting</secondary></indexterm>
The most common error when configuring TLS, as I have already mentioned numerous times, is that the
<emphasis>Common Name (CN)</emphasis> you entered in <xref linkend="s1-config-ldap-tls-server"></xref> is
<emphasis>NOT</emphasis> the Fully Qualified Domain Name (FQDN) of your ldap server.
</para>

<para>
Other errors could be that you have a typo somewhere in your <command>ldapsearch</command> command, or that
your have the wrong permissions on the <filename>servercrt.pem</filename> and <filename>cacert.pem</filename>
files. They should be set with <command>chmod 640</command>, as per <xref
linkend="s1-config-ldap-tls-install"></xref>.
</para>

<para>
For anything else, it's best to read through your ldap logfile or join the &OL; mailing list.
</para>

</sect1>

</chapter>