<?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"> <title>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> Up until now, we have discussed the straight forward 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> <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">RFC2830</ulink>; <emphasis>Lightweight Directory Access Protocol (v3): Extension for Transport Layer Security.</emphasis> </para> <para> 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> 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> 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> 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 recognised 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 horses 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>, if 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> Now, 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; 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 Seccurity, 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 <> 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 Seccurity, 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 Full 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>