samba-mirror/docs-xml/Samba3-ByExample/SBE-DomainAppsSupport.xml

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<!DOCTYPE chapter PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">

<chapter id="DomApps">
<title>Integrating Additional Services</title>

	<para>
	<indexterm><primary>authentication</primary></indexterm>
	<indexterm><primary>backends</primary></indexterm>
	<indexterm><primary>smbpasswd</primary></indexterm>
	<indexterm><primary>ldapsam</primary></indexterm>
	<indexterm><primary>Active Directory</primary></indexterm>
	You've come a long way now. You have pretty much mastered Samba-3 for 
	most uses it can be put to. Up until now, you have cast Samba-3 in the leading 
	role, and where authentication was required, you have used one or another of 
	Samba's many authentication backends (from flat text files with smbpasswd 
	to LDAP directory integration with ldapsam). Now you can design a 
	solution for a new Abmas business. This business is running Windows Server 
	2003 and Active Directory, and these are to stay. It's time to master 
	implementing Samba and Samba-supported services in a domain controlled by 
	the latest Windows authentication technologies. Let's get started &smbmdash; this is 
	leading edge.
	</para>

<sect1>
	<title>Introduction</title>

	<para>
	Abmas has continued its miraculous growth; indeed, nothing seems to be able 
	to stop its diversification into multiple (and seemingly unrelated) fields. 
	Its latest acquisition is Abmas Snack Foods, a big player in the snack-food 
	business.
	</para>

	<para>
	With this acquisition comes new challenges for you and your team. Abmas Snack 
	Foods is a well-developed business with a huge and heterogeneous network. It 
	already has Windows, NetWare, and Proprietary UNIX, but as yet no Samba or Linux. 
	The network is mature and well-established, and there is no question of its chosen 
	user authentication scheme being changed for now. You need to take a wise new 
	approach.
	</para>

	<para>
	You have decided to set the ball rolling by introducing Samba-3 into the network 
	gradually, taking over key services and easing the way to a full migration and, 
	therefore, integration into Abmas's existing business later.
	</para>

	<sect2>
	<title>Assignment Tasks</title>

		<para>
		<indexterm><primary>web</primary><secondary>proxying</secondary></indexterm>
		<indexterm><primary>web</primary><secondary>caching</secondary></indexterm>
	        You've promised the skeptical Abmas Snack Foods management team 
		that you can show them how Samba can ease itself and other Open Source 
		technologies into their existing infrastructure and deliver sound business 
		advantages. Cost cutting is high on their agenda (a major promise of the 
		acquisition). You have chosen Web proxying and caching as your proving ground.
		</para>

		<para>
		<indexterm><primary>bandwidth</primary></indexterm>
		<indexterm><primary>Microsoft ISA</primary></indexterm>
		Abmas Snack Foods has several thousand users housed at its head office 
		and multiple regional offices, plants, and warehouses. A high proportion of 
		the business's work is done online, so Internet access for most of these 
		users is essential. All Internet access, including for all regional offices, 
		is funneled through the head office and is the job of the (now your) networking 
		team. The bandwidth requirements were horrific (comparable to a small ISP), and 
		the team soon discovered proxying and caching. In fact, they became one of 
		the earliest commercial users of Microsoft ISA.
		</para>

		<para>
		<indexterm><primary>Active Directory</primary></indexterm>
		<indexterm><primary>authenticated</primary></indexterm>
		<indexterm><primary>proxy</primary></indexterm>
		The team is not happy with ISA. Because it never lived up to its marketing promises, 
		it underperformed and had reliability problems. You have pounced on the opportunity 
		to show what Open Source can do. The one thing they do like, however, is ISA's 
		integration with Active Directory. They like that their users, once logged on, 
		are automatically authenticated against the proxy. If your alternative to ISA 
		can operate completely seamlessly in their Active Directory domain, it will be
		approved.
		</para>

		<para>
		This is a hands-on exercise. You build software applications so
		that you obtain the functionality Abmas needs.
		</para>

	</sect2>
</sect1>

<sect1>
<title>Dissection and Discussion</title>

	<para>
	The key requirements in this business example are straightforward. You are not required 
	to do anything new, just to replicate an existing system, not lose any existing features, 
	and improve performance. The key points are:
	</para>

	<itemizedlist>
		<listitem><para>
		Internet access for most employees
		</para></listitem>
		<listitem><para>
		Distributed system to accommodate load and geographical distribution of users
		</para></listitem>
		<listitem><para>
		Seamless and transparent interoperability with the existing Active Directory domain
		</para></listitem>
	</itemizedlist>


	<sect2>
		<title>Technical Issues</title>

		<para>
		<indexterm><primary>browsing</primary></indexterm>
		<indexterm><primary>Squid proxy</primary></indexterm>
		<indexterm><primary>proxy</primary></indexterm>
		<indexterm><primary>authentication</primary></indexterm>
		<indexterm><primary>Internet Explorer</primary></indexterm>
		<indexterm><primary>winbind</primary></indexterm>
		<indexterm><primary>NTLM</primary></indexterm>
		<indexterm><primary>NTLM authentication daemon</primary></indexterm>
		<indexterm><primary>authentication</primary></indexterm>
		<indexterm><primary>daemon</primary></indexterm>
		<indexterm><primary>Active Directory</primary></indexterm>
		<indexterm><primary>domain</primary><secondary>Active Directory</secondary></indexterm>
		<indexterm><primary>Kerberos</primary></indexterm><indexterm><primary>token</primary></indexterm>
		Functionally, the user's Internet Explorer requests a browsing session with the 
		Squid proxy, for which it offers its AD authentication token. Squid hands off 
		the authentication request to the Samba-3 authentication helper application
		called <command>ntlm_auth</command>. This helper is a hook into winbind, the 
		Samba-3 NTLM authentication daemon. Winbind enables UNIX services to authenticate 
		against Microsoft Windows domains, including Active Directory domains. As Active 
		Directory authentication is a modified Kerberos authentication, winbind is assisted 
		in this by local Kerberos 5 libraries configured to check passwords with the Active 
		Directory server. Once the token has been checked, a browsing session is established. 
		This process is entirely transparent and seamless to the user.
		</para>

		<para>
		Enabling this consists of:
		</para>

		<itemizedlist>
			<listitem><para>
			Preparing the necessary environment using preconfigured packages
			</para></listitem>

			<listitem><para>
			Setting up raw Kerberos authentication against the Active Directory domain
			</para></listitem>

			<listitem><para>
			Configuring, compiling, and then installing the supporting Samba-3 components
			</para></listitem>

			<listitem><para>
			Tying it all together
			</para></listitem>
		</itemizedlist>

	</sect2>


	<sect2>
		<title>Political Issues</title>

		<para>
		You are a stranger in a strange land, and all eyes are upon you. Some would even like to see 
		you fail. For you to gain the trust of your newly acquired IT people, it is essential that your 
		solution does everything the old one did, but does it better in every way. Only then 
		will the entrenched positions consider taking up your new way of doing things on a 
		wider scale.
		</para>

	</sect2>

</sect1>

<sect1>
	<title>Implementation</title>

	<para>
	<indexterm><primary>Squid</primary></indexterm>
	First, your system needs to be prepared and in a known good state to proceed. This consists 
	of making sure that everything the system depends on is present and that everything that could 
	interfere or conflict with the system is removed. You will be configuring the Squid and Samba-3 
	packages and updating them if necessary. If conflicting packages of these programs are installed, 
	they must be removed.
	</para>

	<para>
	<indexterm><primary>Red Hat Linux</primary></indexterm>
	The following packages should be available on your Red Hat Linux system:
	</para>

	<itemizedlist>
		<listitem><para>
		<indexterm><primary>krb5</primary></indexterm>
		<indexterm><primary>Kerberos</primary></indexterm>
		krb5-libs
		</para></listitem>

		<listitem><para>
		krb5-devel
		</para></listitem>

		<listitem><para>
		krb5-workstation
		</para></listitem>

		<listitem><para>
		krb5-server
		</para></listitem>

		<listitem><para>
		pam_krb5
		</para></listitem>
	</itemizedlist>

	<para>
	<indexterm><primary>SUSE Linux</primary></indexterm>
	In the case of SUSE Linux, these packages are called:
	</para>

        <itemizedlist>
                <listitem><para>
                heimdal-lib
                </para></listitem>

                <listitem><para>
                heimdal-devel
                </para></listitem>

		<listitem><para>
		<indexterm><primary>Heimdal</primary></indexterm>
                heimdal
                </para></listitem>

                <listitem><para>
                pam_krb5
                </para></listitem>
        </itemizedlist>

	<para>
	If the required packages are not present on your system, you must install
	them from the vendor's installation media. Follow the administrative guide
	for your Linux system to ensure that the packages are correctly updated.
	</para>

	<note><para>
	<indexterm><primary>MS Windows Server 2003</primary></indexterm>
	<indexterm><primary>Kerberos</primary></indexterm>
	<indexterm><primary>MIT</primary></indexterm>
	If the requirement is for interoperation with MS Windows Server 2003, it
	will be necessary to ensure that you are using MIT Kerberos version 1.3.1
	or later. Red Hat Linux 9 ships with MIT Kerberos 1.2.7 and thus requires
	updating.
	</para>

	<para>
	<indexterm><primary>Heimdal</primary></indexterm>
	<indexterm><primary>SUSE Enterprise Linux Server</primary></indexterm>
	Heimdal 0.6 or later is required in the case of SUSE Linux. SUSE Enterprise
	Linux Server 8 ships with Heimdal 0.4. SUSE 9 ships with the necessary version.
	</para></note>

	<sect2 id="ch10-one">
	<title>Removal of Pre-Existing Conflicting RPMs</title>

	<para>
	<indexterm><primary>Squid</primary></indexterm>
	If Samba and/or Squid RPMs are installed, they should be updated. You can 
	build both from source.
	</para>

	<para>
	<indexterm><primary>rpm</primary></indexterm>
	<indexterm><primary>samba</primary></indexterm>
	<indexterm><primary>squid</primary></indexterm>
	Locating the packages to be un-installed can be achieved by running:
<screen>
&rootprompt; rpm -qa | grep -i samba
&rootprompt; rpm -qa | grep -i squid
</screen>
	The identified packages may be removed using:
<screen>
&rootprompt; rpm -e samba-common
</screen>
	</para>

	<sect2>
	<title>Kerberos Configuration</title>

	<para>
	<indexterm><primary>Kerberos</primary></indexterm>
	<indexterm><primary>Active Directory</primary><secondary>server</secondary></indexterm>
	<indexterm><primary>ADS</primary></indexterm>
	<indexterm><primary>KDC</primary></indexterm>
	The systems Kerberos installation must be configured to communicate with 
	your primary Active Directory server (ADS KDC).
	</para>

	<para>
	Strictly speaking, MIT Kerberos version 1.3.4 currently gives the best results, 
	although the current default Red Hat MIT version 1.2.7 gives acceptable results 
	unless you are using Windows 2003 servers.
	</para>

	<para>
	<indexterm><primary>MIT</primary></indexterm>
	<indexterm><primary>Heimdal</primary></indexterm>
	<indexterm><primary>Kerberos</primary></indexterm>
	<indexterm><primary>/etc/krb5.conf</primary></indexterm>
	<indexterm><primary>DNS</primary><secondary>SRV records</secondary></indexterm>
	<indexterm><primary>KDC</primary></indexterm>
	<indexterm><primary>DNS</primary><secondary>lookup</secondary></indexterm>
	Officially, neither MIT (1.3.4) nor Heimdal (0.63) Kerberos needs an <filename>/etc/krb5.conf</filename> 
	file in order to work correctly. All ADS domains automatically create SRV records in the 
	DNS zone <constant>Kerberos.REALM.NAME</constant> for each KDC in the realm. Since both 
	MIT and Heimdal, KRB5 libraries default to checking for these records, so they 
	automatically find the KDCs. In addition, <filename>krb5.conf</filename> allows 
	specifying only a single KDC, even if there is more than one. Using the DNS lookup 
	allows the KRB5 libraries to use whichever KDCs are available.
	</para>

	<procedure>
	<title>Kerberos Configuration Steps</title>

		<step><para>
		<indexterm><primary>krb5.conf</primary></indexterm>
		If you find the need to manually configure the <filename>krb5.conf</filename>, you should edit it
		to have the contents shown in <link linkend="ch10-krb5conf"/>. The final fully qualified path for this file 
		should be <filename>/etc/krb5.conf</filename>.
		</para></step>

		<step><para>
		<indexterm><primary>Kerberos</primary></indexterm>
		<indexterm><primary>realm</primary></indexterm>
		<indexterm><primary>case-sensitive</primary></indexterm>
		<indexterm><primary>KDC</primary></indexterm>
		<indexterm><primary>synchronization</primary></indexterm>
		<indexterm><primary>initial credentials</primary></indexterm>
		<indexterm><primary>Clock skew</primary></indexterm>
		<indexterm><primary>NTP</primary></indexterm>
		<indexterm><primary>DNS</primary><secondary>lookup</secondary></indexterm>
		<indexterm><primary>reverse DNS</primary></indexterm>
		<indexterm><primary>NetBIOS name </primary></indexterm>
		<indexterm><primary>/etc/hosts</primary></indexterm>
		<indexterm><primary>mapping</primary></indexterm>
		The following gotchas often catch people out. Kerberos is case sensitive. Your realm must
		be in UPPERCASE, or you will get an error: <quote>Cannot find KDC for requested realm while getting
		initial credentials</quote>.  Kerberos is picky about time synchronization. The time
		according to your participating servers must be within 5 minutes or you get an error:
		<quote>kinit(v5): Clock skew too great while getting initial credentials</quote>.
		Clock skew limits are, in fact, configurable in the Kerberos protocols (the default is
		5 minutes). A better solution is to implement NTP throughout your server network.
		Kerberos needs to be able to do a reverse DNS lookup on the IP address of your KDC.
		Also, the name that this reverse lookup maps to must either be the NetBIOS name of
		the KDC (i.e., the hostname with no domain attached) or the
		NetBIOS name followed by the realm. If all else fails, you can add a
		<filename>/etc/hosts</filename> entry mapping the IP address of your KDC to its
		NetBIOS name. If Kerberos cannot do this reverse lookup, you will get a local error
		when you try to join the realm.
		</para></step>

		<step><para>
		<indexterm><primary>kinit</primary></indexterm>
		You are now ready to test your installation by issuing the command:
<screen>
&rootprompt; kinit [USERNAME@REALM]
</screen> 
		You are asked for your password, which you should enter. The following
		is a typical console sequence:
<screen>
&rootprompt; kinit ADMINISTRATOR@LONDON.ABMAS.BIZ
Password for ADMINISTRATOR@LONDON.ABMAS.BIZ: 
</screen>
		Make sure that your password is accepted by the Active Directory KDC.
		</para></step>
	</procedure>

<example id="ch10-krb5conf">
<title>Kerberos Configuration &smbmdash; File: <filename>/etc/krb5.conf</filename></title>
<screen>
[libdefaults]
	default_realm = LONDON.ABMAS.BIZ

[realms] 
	LONDON.ABMAS.BIZ = {
	kdc = w2k3s.london.abmas.biz
	}
</screen>
</example>

	<para><indexterm>
	    <primary>klist</primary>
	  </indexterm>
	The command
<screen>
&rootprompt; klist -e 
</screen>
	shows the Kerberos tickets cached by the system.
	</para>

	<sect3>
	<title>Samba Configuration</title>

	<para>
	<indexterm><primary>Active Directory</primary></indexterm>
	Samba must be configured to correctly use Active Directory. Samba-3 must be used, since it 
	has the necessary components to interface with Active Directory.
	</para>

	<procedure>
	<title>Securing Samba-3 With ADS Support Steps</title>

		<step><para>
		<indexterm><primary>Red Hat Linux</primary></indexterm>
		<indexterm><primary>Samba Tea</primary></indexterm>
		<indexterm><primary>Red Hat Fedora Linux</primary></indexterm>
		<indexterm><primary>MIT KRB5</primary></indexterm>
		<indexterm><primary>ntlm_auth</primary></indexterm>
		Download the latest stable Samba-3 for Red Hat Linux from the official Samba Team
		<ulink url="http://ftp.samba.org">FTP site.</ulink> The official Samba Team
		RPMs for Red Hat Fedora Linux contain the <command>ntlm_auth</command> tool
		needed, and are linked against MIT KRB5 version 1.3.1 and therefore are ready for use.
		</para>

		<para>
		<indexterm><primary>SerNet</primary></indexterm>
		<indexterm><primary>RPMs</primary></indexterm>
		The necessary, validated RPM packages for SUSE Linux may be obtained from
		the <ulink url="ftp://ftp.sernet.de/pub/samba">SerNet</ulink> FTP site that
		is located in Germany. All SerNet RPMs are validated, have the necessary
		<command>ntlm_auth</command> tool, and are statically linked 
		against suitably patched Heimdal 0.6 libraries.
		</para></step>

		<step><para>
		Using your favorite editor, change the <filename>/etc/samba/smb.conf</filename>
		file so it has contents similar to the example shown in <link linkend="ch10-smbconf"/>.
		</para></step>

		<step><para>
		<indexterm><primary>computer account</primary></indexterm>
		<indexterm><primary>Active Directory</primary></indexterm>
		<indexterm><primary>net</primary><secondary>ads</secondary><tertiary>join</tertiary></indexterm>i
		<indexterm><primary>Kerberos ticket</primary></indexterm>
		<indexterm><primary>ticket</primary></indexterm>
		Next you need to create a computer account in the Active Directory. 
		This sets up the trust relationship needed for other clients to 
		authenticate to the Samba server with an Active Directory Kerberos ticket. 
		This is done with the <quote>net ads join -U [Administrator%Password]</quote>
		command, as follows:
<screen>
&rootprompt; net ads join -U administrator%vulcon
</screen>
		</para></step>

		<step><para>
		<indexterm><primary>smbd</primary></indexterm>
		<indexterm><primary>nmbd</primary></indexterm>
		<indexterm><primary>winbindd</primary></indexterm>
		<indexterm><primary>Active Directory</primary></indexterm>
		<indexterm><primary>Samba</primary></indexterm>
		Your new Samba binaries must be started in the standard manner as is applicable
		to the platform you are running on. Alternatively, start your Active Directory-enabled Samba with the following commands:
<screen>
&rootprompt; smbd -D
&rootprompt; nmbd -D
&rootprompt; winbindd -D
</screen>
		</para></step>

		<step><para>
		<indexterm><primary>winbind</primary></indexterm>
		<indexterm><primary>Active Directory</primary><secondary>domain</secondary></indexterm>
		<indexterm><primary>wbinfo</primary></indexterm>
		<indexterm><primary>enumerating</primary></indexterm>
		<indexterm><primary>Active Directory</primary><secondary>tree</secondary></indexterm>
		We now need to test that Samba is communicating with the Active 
		Directory domain; most specifically, we want to see whether winbind 
		is enumerating users and groups. Issue the following commands:
<screen>
&rootprompt; wbinfo -t
checking the trust secret via RPC calls succeeded
</screen>
		This tests whether we are authenticating against Active Directory:
<screen>
&rootprompt; wbinfo -u
LONDON+Administrator
LONDON+Guest
LONDON+SUPPORT_388945a0
LONDON+krbtgt
LONDON+jht
LONDON+xjht
</screen>
		This enumerates all the users in your Active Directory tree:
<screen>
&rootprompt; wbinfo -g
LONDON+Domain Computers
LONDON+Domain Controllers
LONDON+Schema Admins
LONDON+Enterprise Admins
LONDON+Domain Admins
LONDON+Domain Users
LONDON+Domain Guests
LONDON+Group Policy Creator Owners
LONDON+DnsUpdateProxy
</screen>
		This enumerates all the groups in your Active Directory tree.
		</para></step>

		<step><para>
		<indexterm><primary>Squid</primary></indexterm>
		<indexterm><primary>ntlm_auth</primary></indexterm>
		Squid uses the <command>ntlm_auth</command> helper build with Samba-3.
		You may test <command>ntlm_auth</command> with the command:
<screen>
&rootprompt; /usr/bin/ntlm_auth --username=jht
password: XXXXXXXX
</screen>
		You are asked for your password, which you should enter. You are rewarded with:
<screen>
&rootprompt; NT_STATUS_OK: Success (0x0)
</screen>
		</para></step>

		<step><para>
		<indexterm><primary>ntlm_auth</primary></indexterm>
		<indexterm><primary>authenticate</primary></indexterm>
		<indexterm><primary>winbind</primary></indexterm>
		<indexterm><primary>privileged pipe</primary></indexterm>
		<indexterm><primary>squid</primary></indexterm>
		<indexterm><primary>chgrp</primary></indexterm>
		<indexterm><primary>chmod</primary></indexterm>
		<indexterm><primary>failure</primary></indexterm>
		The <command>ntlm_auth</command> helper, when run from a command line as the user 
		<quote>root</quote>, authenticates against your Active Directory domain (with 
		the aid of winbind). It manages this by reading from the winbind privileged pipe. 
		Squid is running with the permissions of user <quote>squid</quote> and group 
		<quote>squid</quote> and is not able to do this unless we make a vital change. 
		Squid cannot read from the winbind privilege pipe unless you change the 
		permissions of its directory. This is the single biggest cause of failure in the 
		whole process. Remember to issue the following command (for Red Hat Linux):
<screen>
&rootprompt; chgrp squid /var/cache/samba/winbindd_privileged
&rootprompt; chmod 750 /var/cache/samba/winbindd_privileged
</screen>
		For SUSE Linux 9, execute the following:
<screen>
&rootprompt; chgrp squid /var/lib/samba/winbindd_privileged
&rootprompt; chmod 750 /var/lib/samba/winbindd_privileged
</screen>
		</para></step>

	</procedure>
	</sect3>

	<sect3>
	<title>NSS Configuration</title>

	<para>
	<indexterm><primary>NSS</primary></indexterm>
	<indexterm><primary>winbind</primary></indexterm>
	<indexterm><primary>authentication</primary></indexterm>
	For Squid to benefit from Samba-3, NSS must be updated to allow winbind as a valid route to user authentication.
	</para>

	<para>
	Edit your <filename>/etc/nsswitch.conf</filename> file so it has the parameters shown
	in <link linkend="ch10-etcnsscfg"/>.
	</para>

<example id="ch10-smbconf">
<title>Samba Configuration &smbmdash; File: <filename>/etc/samba/smb.conf</filename></title>
<smbconfblock>
<smbconfsection name="[global]"/>
<smbconfoption name="workgroup">LONDON</smbconfoption>
<smbconfoption name="netbios name">W2K3S</smbconfoption>
<smbconfoption name="realm">LONDON.ABMAS.BIZ</smbconfoption>
<smbconfoption name="security">ads</smbconfoption>
<smbconfoption name="encrypt passwords">yes</smbconfoption>
<smbconfoption name="password server">w2k3s.london.abmas.biz</smbconfoption>

<smbconfcomment>separate domain and username with '/', like DOMAIN/username</smbconfcomment>
<smbconfoption name="winbind separator">/</smbconfoption>

<smbconfcomment>use UIDs from 10000 to 20000 for domain users</smbconfcomment>
<smbconfoption name="idmap uid">10000-20000</smbconfoption>
<smbconfcomment>use GIDs from 10000 to 20000 for domain groups</smbconfcomment>
<smbconfoption name="idmap gid">10000-20000</smbconfoption>

<smbconfcomment>allow enumeration of winbind users and groups</smbconfcomment>
<smbconfoption name="winbind enum users">yes</smbconfoption>
<smbconfoption name="winbind enum groups">yes</smbconfoption>
<smbconfoption name="winbind user default domain">yes</smbconfoption>
</smbconfblock>
</example>

<example id="ch10-etcnsscfg">
<title>NSS Configuration File Extract &smbmdash; File: <filename>/etc/nsswitch.conf</filename></title>
<screen>
passwd: files winbind
shadow: files
group: files winbind
</screen>
</example>

	</sect3>

	<sect3>
	<title>Squid Configuration</title>

	<para>
	<indexterm><primary>Squid</primary></indexterm>
	<indexterm><primary>Active Directory</primary><secondary>authentication</secondary></indexterm>
	Squid must be configured correctly to interact with the Samba-3 
	components that handle Active Directory authentication.
	</para>

	</sect3>

	</sect2>

	<sect2>
	<title>Configuration</title></sect2>

	<procedure>
	<title>Squid Configuration Steps</title>

		<step><para>
		<indexterm><primary>SUSE Linux</primary></indexterm>
		<indexterm><primary>Squid</primary> </indexterm>
		<indexterm><primary>helper agent</primary></indexterm>
		If your Linux distribution is SUSE Linux 9, the version of Squid 
		supplied is already enabled to use the winbind helper agent. You
		can therefore omit the steps that would build the Squid binary
		programs.
		</para></step>

		<step><para>
		<indexterm><primary>nobody</primary></indexterm>
		<indexterm><primary>squid</primary></indexterm>
		<indexterm><primary>rpms</primary></indexterm>
		<indexterm><primary>/etc/passwd</primary></indexterm>
		<indexterm><primary>/etc/group</primary></indexterm>
		Squid, by default, runs as the user <constant>nobody</constant>. You need to 
		add a system user <constant>squid</constant> and a system group 
		<constant>squid</constant> if they are not set up already (if the default 
		Red Hat squid rpms were installed, they will be).  Set up a 
		<constant>squid</constant> user in <filename>/etc/passwd</filename> 
		and a <constant>squid</constant> group in <filename>/etc/group</filename> if these aren't there already.
		</para></step>

		<step><para>
		<indexterm><primary>permissions</primary></indexterm>
		<indexterm><primary>chown</primary></indexterm>
		You now need to change the permissions on Squid's <constant>var</constant>
		directory.  Enter the following command:
<screen>
&rootprompt; chown -R squid /var/cache/squid
</screen>
		</para></step>

		<step><para>
		<indexterm><primary>logging</primary></indexterm>
		<indexterm><primary>Squid</primary></indexterm>
		Squid must also have control over its logging. Enter the following commands:
<screen>
&rootprompt; chown -R chown squid:squid /var/log/squid
&rootprompt; chmod 770 /var/log/squid
</screen>
		</para></step>

		<step><para>
		Finally, Squid must be able to write to its disk cache!
		Enter the following commands:
<screen>
&rootprompt; chown -R chown squid:squid /var/cache/squid
&rootprompt; chmod 770 /var/cache/squid
</screen>
		</para></step>

		<step><para>
		<indexterm><primary>/etc/squid/squid.conf</primary></indexterm>
		The <filename>/etc/squid/squid.conf</filename> file must be edited to include the lines from 
		<link linkend="etcsquidcfg"/> and <link linkend="etcsquid2"/>.
		</para></step>

		<step><para>
		<indexterm><primary>cache directories</primary></indexterm>
		You must create Squid's cache directories before it may be run.  Enter the following command: 
<screen>
&rootprompt; squid -z
</screen>
		</para></step>

		<step><para>
		Finally, start Squid and enjoy transparent Active Directory authentication.
		Enter the following command:
<screen>
&rootprompt; squid
</screen>
		</para></step>
	</procedure>

<example id="etcsquidcfg">
<title>Squid Configuration File Extract &smbmdash; <filename>/etc/squid.conf</filename> [ADMINISTRATIVE PARAMETERS Section]</title>
<screen>
	cache_effective_user squid
	cache_effective_group squid
</screen>
</example>

<example id="etcsquid2">
<title>Squid Configuration File extract &smbmdash; File: <filename>/etc/squid.conf</filename> [AUTHENTICATION PARAMETERS Section]</title>
<screen>
	auth_param ntlm program /usr/bin/ntlm_auth \
                                --helper-protocol=squid-2.5-ntlmssp
	auth_param ntlm children 5
	auth_param ntlm max_challenge_reuses 0
	auth_param ntlm max_challenge_lifetime 2 minutes
	auth_param basic program /usr/bin/ntlm_auth \
                                --helper-protocol=squid-2.5-basic
	auth_param basic children 5
	auth_param basic realm Squid proxy-caching web server
	auth_param basic credentialsttl 2 hours
	acl AuthorizedUsers proxy_auth REQUIRED
	http_access allow all AuthorizedUsers
</screen>
</example>

	</sect2>

	<sect2>
		<title>Key Points Learned</title>

		<para>
		<indexterm><primary>Web browsers</primary></indexterm>
		<indexterm><primary>services</primary></indexterm>
		<indexterm><primary>authentication protocols</primary></indexterm>
		<indexterm><primary>Web</primary><secondary>proxy</secondary><tertiary>access</tertiary></indexterm>
		<indexterm><primary>NTLMSSP</primary></indexterm>
		Microsoft Windows networking protocols permeate the spectrum of technologies that Microsoft
		Windows clients use, even when accessing traditional services such as Web browsers. Depending 
		on whom you discuss this with, this is either good or bad. No matter how you might evaluate this,
		the use of NTLMSSP as the authentication protocol for Web proxy access has some advantages over
		the cookie-based authentication regime used by all competing browsers. It is Samba's implementation
		of NTLMSSP that makes it attractive to implement the solution that has been demonstrated in this chapter.
		</para>

	</sect2>

</sect1>

<sect1>
	<title>Questions and Answers</title>

	<para>
	<indexterm><primary>ntlm_auth</primary></indexterm>
	<indexterm><primary>SambaXP conference</primary></indexterm>
	<indexterm><primary>Goettingen</primary></indexterm>
	<indexterm><primary>Italian</primary></indexterm>
	The development of the <command>ntlm_auth</command> module was first discussed in many Open Source circles
	in 2002. At the SambaXP conference in Goettingen, Germany, Mr. Francesco Chemolli demonstrated the use of 
	<command>ntlm_auth</command> during one of the late developer meetings that took place. Since that time, the 
	adoption of <command>ntlm_auth</command> has spread considerably.
	</para>

	<para>
	The largest report from a site that uses Squid with <command>ntlm_auth</command>-based authentication
	support uses a dual processor server that has 2 GB of memory. It provides Web and FTP proxy services for 10,000
	users. Approximately 2,000 of these users make heavy use of the proxy services. According to the source, who
	wishes to remain anonymous, the sustained transaction load on this server hovers around 140 hits/sec. The following
	comments were made with respect to questions regarding the performance of this installation:
	</para>

	<blockquote><para>
	[In our] EXTREMELY optimized environment . . . [the] performance impact is almost [nothing]. The <quote>almost</quote> 
	part is due to the brain damage of the ntlm-over-http protocol definition. Suffice to say that its worst-case 
	scenario triples the number of hits needed to perform the same transactions versus basic or digest auth[entication].
	</para></blockquote>

	<para>
	You would be well-advised to recognize that all cache-intensive proxying solutions demand a lot of memory.
	Make certain that your Squid proxy server is equipped with sufficient memory to permit all proxy operations to run 
	out of memory without invoking the overheads involved in the use of memory that has to be swapped to disk.
	</para>

	<qandaset defaultlabel="chap10bqa" type="number">
	<qandaentry>
	<question>

		<para>
		What does Samba have to do with Web proxy serving?
		</para>

	</question>
	<answer>

		<para>
		<indexterm><secondary>transparent inter-operability</secondary></indexterm>
		<indexterm><primary>Windows clients</primary></indexterm>
		<indexterm><primary>network</primary><secondary>services</secondary></indexterm>
		<indexterm><primary>authentication</primary></indexterm>
		<indexterm><primary>wrapper</primary></indexterm>
		To provide transparent interoperability between Windows clients and the network services
		that are used from them, Samba had to develop tools and facilities that deliver that feature. The benefit
		of Open Source software is that it can readily be reused. The current <command>ntlm_auth</command>
		module is basically a wrapper around authentication code from the core of the Samba project.
		</para>

		<para>
		<indexterm><primary>plain-text</primary></indexterm>
		<indexterm><primary>authentication</primary><secondary>plain-text</secondary></indexterm>
		<indexterm><primary>Web</primary><secondary>proxy</secondary></indexterm>
		<indexterm><primary>FTP</primary><secondary>proxy</secondary></indexterm>
		<indexterm><primary>NTLMSSP</primary></indexterm>
		<indexterm><primary>logon credentials</primary></indexterm>
		<indexterm><primary>Windows explorer</primary></indexterm>
		<indexterm><primary>Internet Information Server</primary></indexterm>
		<indexterm><primary>Apache Web server</primary></indexterm>
		The <command>ntlm_auth</command> module supports basic plain-text authentication and NTLMSSP 
		protocols. This module makes it possible for Web and FTP proxy requests to be authenticated without
		the user being interrupted via his or her Windows logon credentials. This facility is available with
		MS Windows Explorer and is one of the key benefits claimed for Microsoft Internet Information Server.
		There are a few open source initiatives to provide support for these protocols in the Apache Web server
		also.
		</para>

		<para>
		<indexterm><primary>wrapper</primary></indexterm>
		The short answer is that by adding a wrapper around key authentication components of Samba, other
		projects (like Squid) can benefit from the labors expended in meeting user interoperability needs.
		</para>

	</answer>
	</qandaentry>

	<qandaentry>
	<question>

		<para>
		What other services does Samba provide?
		</para>

	</question>
	<answer>

		<para>
		<indexterm><primary>winbindd</primary></indexterm>
		<indexterm><primary>Identity resolver</primary></indexterm>
		<indexterm><primary>daemon</primary></indexterm>
		<indexterm><primary>smbd</primary></indexterm>
		<indexterm><primary>file and print server</primary></indexterm>
		Samba-3 is a file and print server. The core components that provide this functionality are <command>smbd</command>,
		<command>nmbd</command>, and the identity resolver daemon, <command>winbindd</command>.
		</para>

		<para>
		<indexterm><primary>SMB/CIFS</primary></indexterm>
		<indexterm><primary>smbclient</primary></indexterm>
		Samba-3 is an SMB/CIFS client. The core component that provides this is called <command>smbclient</command>.
		</para>

		<para>
		<indexterm><primary>modules</primary></indexterm>
		<indexterm><primary>utilities</primary></indexterm>
		<indexterm><primary>validation</primary></indexterm>
		<indexterm><primary>inter-operability</primary></indexterm>
		<indexterm><primary>authentication</primary></indexterm>
		Samba-3 includes a number of helper tools, plug-in modules, utilities, and test and validation facilities.
		Samba-3 includes glue modules that help provide interoperability between MS Windows clients and UNIX/Linux
		servers and clients. It includes Winbind agents that make it possible to authenticate UNIX/Linux access attempts
		as well as logins to an SMB/CIFS authentication server backend. Samba-3 includes name service switch (NSS) modules
		to permit identity resolution via SMB/CIFS servers (Windows NT4/200x, Samba, and a host of other commercial
		server products).
		</para>

	</answer>
	</qandaentry>

	<qandaentry>
	<question>

		<para>
		Does use of Samba (<command>ntlm_auth</command>) improve the performance of Squid?
		</para>

	</question>
	<answer>

		<para>
		Not really. Samba's <command>ntlm_auth</command> module handles only authentication. It requires that
		Squid make an external call to <command>ntlm_auth</command> and therefore actually incurs a
		little more overhead. Compared with the benefit obtained, that overhead is well worth enduring. Since
		Squid is a proxy server, and proxy servers tend to require lots of memory, it is good advice to provide
		sufficient memory when using Squid. Just add a little more to accommodate <command>ntlm_auth</command>.
		</para>

	</answer>
	</qandaentry>
	</qandaset>

</sect1>

</chapter>