Another set of updates.

[sfrench/samba-autobuild/.git] / docs / docbook / projdoc / DOMAIN_MEMBER.xml

<chapter id="domain-member">

<chapterinfo>
        &author.jeremy;
        &author.jerry;
        &author.jht;
</chapterinfo>

<title>Domain Membership</title>

<para>
Domain Membership is a subject of vital concern, Samba must be able to participate
as a member server in a Microsoft Domain security context, and Samba must be capable of
providing Domain machine member trust accounts, otherwise it would not be capable of offering
a viable option for many users.
</para>

<para>
This chapter covers background information pertaining to domain membership, Samba
configuration for it, and MS Windows client procedures for joining a domain.  Why is
this necessary? Because both are areas in which there exists within the current MS
Windows networking world and particularly in the Unix/Linux networking and administration
world, a considerable level of mis-information, incorrect understanding, and a lack of
knowledge. Hopefully this chapter will fill the voids.
</para>

<sect1>
<title>Features and Benefits</title>

<para>
MS Windows workstations and servers that want to participate in domain security need to
be made Domain members. Participating in Domain security is often called 
<emphasis>Single Sign On</emphasis> or SSO for short. This chapter describes the process
that must be followed to make a workstation (or another server - be it an MS Windows NT4 / 200x
server) or a Samba server a member of an MS Windows Domain security context.
</para>

<para>
Samba-3 can join an MS Windows NT4 style domain as a native member server, an MS Windows
Active Directory Domain as a native member server, or a Samba Domain Control network.
</para>

</sect1>

<sect1>
<title>MS Windows Workstation/Server Machine Trust Accounts</title>

<para>
A machine trust account is an account that is used to authenticate a client machine
(rather than a user) to the Domain Controller server.  In Windows terminology,
this is known as a "Computer Account."
</para>

<para>
The password of a machine trust account acts as the shared secret for
secure communication with the Domain Controller.  This is a security
feature to prevent an unauthorized machine with the same NetBIOS name
from joining the domain and gaining access to domain user/group
accounts.  Windows NT, 200x, XP Professional clients use machine trust
accounts, but Windows 9x / Me / XP Home clients do not.  Hence, a
Windows 9x / Me / XP Home  client is never a true member of a domain
because it does not possess a machine trust account, and thus has no
shared secret with the domain controller.
</para>

<para>
A Windows NT4 PDC stores each machine trust account in the Windows
Registry. The introduction of MS Windows 2000 saw the introduction of Active Directory,
the new repository for machine trust accounts.
</para>

<para>
A Samba PDC, however, stores each machine trust account in two parts,
as follows:

<itemizedlist>
        <listitem><para>
        A Domain Security Account (stored in the <emphasis>passdb backend</emphasis>
        that has been configured in the &smb.conf; file. The precise nature of the
        account information that is stored depends on the type of backend database
        that has been chosen.
        </para>

        <para>
        The older format of this data is the <filename>smbpasswd</filename> database
        which contains the unix login ID, the Unix user identifier (UID), and the
        LanMan and NT encrypted passwords. There is also some other information in
        this file that we do not need to concern ourselves with here.
        </para>

        <para>
        The two newer database types are called <emphasis>ldapsam, tdbsam</emphasis>.
        Both store considerably more data than the older <filename>smbpasswd</filename>
        file did. The extra information enables new user account controls to be used.
        </para></listitem>

        <listitem><para>
        A corresponding Unix account, typically stored in <filename>/etc/passwd</filename>.
        Work is in progress to allow a simplified mode of operation that does not require
        Unix user accounts, but this may not be a feature of the early releases of Samba-3.
        </para></listitem>
</itemizedlist>
</para>

<para>
There are two ways to create machine trust accounts:
</para>

<itemizedlist>
        <listitem><para>
        Manual creation. Both the Samba and corresponding Unix account are created by hand.
        </para></listitem>
        
        <listitem><para>
        "On-the-fly" creation. The Samba machine trust account is automatically created by
        Samba at the time the client is joined to the domain. (For security, this is the
        recommended method.) The corresponding Unix account may be created automatically or manually. 
        </para></listitem>
</itemizedlist>

<sect2>
<title>Manual Creation of Machine Trust Accounts</title>

<para>
The first step in manually creating a machine trust account is to manually create the
corresponding Unix account in <filename>/etc/passwd</filename>.  This can be done using
<command>vipw</command> or other 'add user' command that is normally used to create new
Unix accounts.  The following is an example for a Linux based Samba server:
</para>

<para>
<prompt>root# </prompt><command>/usr/sbin/useradd -g 100 -d /dev/null -c <replaceable>"machine nickname"</replaceable> -s /bin/false <replaceable>machine_name</replaceable>$ </command>
</para>

<para>
<prompt>root# </prompt><command>passwd -l <replaceable>machine_name</replaceable>$</command>
</para>

<para>
On *BSD systems, this can be done using the 'chpass' utility:
</para>

<para>
<prompt>root# </prompt><command>chpass -a "<replaceable>machine_name</replaceable>$:*:101:100::0:0:Workstation <replaceable>machine_name</replaceable>:/dev/null:/sbin/nologin"</command>
</para>

<para>
The <filename>/etc/passwd</filename> entry will list the machine name 
with a "$" appended, won't have a password, will have a null shell and no 
home directory. For example a machine named 'doppy' would have an 
<filename>/etc/passwd</filename> entry like this:
</para>

<para>
doppy$:x:505:501:<replaceable>machine_nickname</replaceable>:/dev/null:/bin/false
</para>

<para>
Above, <replaceable>machine_nickname</replaceable> can be any
descriptive name for the client, i.e., BasementComputer.
<replaceable>machine_name</replaceable> absolutely must be the NetBIOS
name of the client to be joined to the domain.  The "$" must be
appended to the NetBIOS name of the client or Samba will not recognize
this as a machine trust account.
</para>

<para>
Now that the corresponding Unix account has been created, the next step is to create 
the Samba account for the client containing the well-known initial 
machine trust account password.  This can be done using the <ulink 
url="smbpasswd.8.html"><command>smbpasswd(8)</command></ulink> command 
as shown here:
</para>

<para>
<programlisting>
<prompt>root# </prompt><userinput>smbpasswd -a -m <replaceable>machine_name</replaceable></userinput>
</programlisting>
</para>

<para>
where <replaceable>machine_name</replaceable> is the machine's NetBIOS
name.  The RID of the new machine account is generated from the UID of 
the corresponding Unix account.
</para>

<warning>
        <title>Join the client to the domain immediately</title>

        <para>
        Manually creating a machine trust account using this method is the 
        equivalent of creating a machine trust account on a Windows NT PDC using 
        the "Server Manager".  From the time at which the account is created
        to the time which the client joins the domain and changes the password,
        your domain is vulnerable to an intruder joining your domain using
        a machine with the same NetBIOS name.  A PDC inherently trusts
        members of the domain and will serve out a large degree of user 
        information to such clients.  You have been warned!
        </para>
</warning>
</sect2>


<sect2>
<title>"On-the-Fly" Creation of Machine Trust Accounts</title>

<para>
The second (and recommended) way of creating machine trust accounts is
simply to allow the Samba server to create them as needed when the client
is joined to the domain.
</para>

<para>Since each Samba machine trust account requires a corresponding
Unix account, a method for automatically creating the
Unix account is usually supplied; this requires configuration of the
<ulink url="smb.conf.5.html#ADDMACHINESCRIPT">add machine script</ulink> 
option in <filename>smb.conf</filename>.  This
method is not required, however; corresponding Unix accounts may also
be created manually.
</para>


<para>
Below is an example for a RedHat Linux system.
</para>

<para><programlisting>
[global]
   # &lt;...remainder of parameters...&gt;
   add machine script = /usr/sbin/useradd -d /dev/null -g 100 -s /bin/false -M %u 
</programlisting></para>

</sect2>


<sect2><title>Joining the Client to the Domain</title>

<para>
The procedure for joining a client to the domain varies with the version of Windows.
</para>

<itemizedlist>
        <listitem><para><emphasis>Windows 2000</emphasis></para>

        <para>
        When the user elects to join the client to a domain, Windows prompts for
        an account and password that is privileged to join the domain. A Samba administrative
        account (i.e., a Samba account that has root privileges on the Samba server) must be
        entered here; the operation will fail if an ordinary user account is given. 
        The password for this account should be set to a different password than the associated
        <filename>/etc/passwd</filename> entry, for security reasons.
        </para>

        <para>
        The session key of the Samba administrative account acts as an
        encryption key for setting the password of the machine trust
        account. The machine trust account will be created on-the-fly, or
        updated if it already exists.
        </para></listitem>

        <listitem><para><emphasis>Windows NT</emphasis></para>

        <para>
        If the machine trust account was created manually, on the
        Identification Changes menu enter the domain name, but do not
        check the box "Create a Computer Account in the Domain."  In this case,
        the existing machine trust account is used to join the machine to
        the domain.
        </para>

        <para>
        If the machine trust account is to be created
        on-the-fly, on the Identification Changes menu enter the domain
        name, and check the box "Create a Computer Account in the Domain."  In
        this case, joining the domain proceeds as above for Windows 2000
        (i.e., you must supply a Samba administrative account when
        prompted).
        </para></listitem>

        <listitem><para><emphasis>Samba</emphasis></para>
        <para>Joining a samba client to a domain is documented in 
        the <link linkend="domain-member">Domain Member</link> chapter.
        </para></listitem>
</itemizedlist>

</sect2>
</sect1>

<sect1>
<title>Domain Member Server</title>

<para>
This mode of server operation involves the samba machine being made a member
of a domain security context. This means by definition that all user authentication
will be done from a centrally defined authentication regime. The authentication
regime may come from an NT3/4 style (old domain technology) server, or it may be
provided from an Active Directory server (ADS) running on MS Windows 2000 or later.
</para>

<para>
<emphasis>
Of course it should be clear that the authentication back end itself could be from any
distributed directory architecture server that is supported by Samba. This can be
LDAP (from OpenLDAP), or Sun's iPlanet, of NetWare Directory Server, etc.
</emphasis>
</para>

<para>
Please refer to the section on Howto configure Samba as a Primary Domain Controller
and for more information regarding how to create a domain machine account for a
domain member server as well as for information regarding how to enable the samba
domain member machine to join the domain and to be fully trusted by it.
</para>

<sect2>
<title>Joining an NT4 type Domain with Samba-3</title>

<para>
<emphasis>Assumptions:</emphasis>
<programlisting>
        NetBIOS name: SERV1
        Win2K/NT domain name: DOM
        Domain's PDC NetBIOS name: DOMPDC
        Domain's BDC NetBIOS names: DOMBDC1 and DOMBDC2
</programlisting>
</para>

<para>
First, you must edit your &smb.conf; file to tell Samba it should
now use domain security.
</para>

<para>
Change (or add) your <ulink url="smb.conf.5.html#SECURITY">
<parameter>security =</parameter></ulink> line in the [global] section 
of your &smb.conf; to read:
</para>

<para>
<programlisting>
        <command>security = domain</command>
</programlisting>
</para>

<para>
Next change the <ulink url="smb.conf.5.html#WORKGROUP"><parameter>
workgroup =</parameter></ulink> line in the [global] section to read: 
</para>

<para>
<programlisting>
        <command>workgroup = DOM</command>
</programlisting>
</para>

<para>
as this is the name of the domain we are joining.
</para>

<para>
You must also have the parameter <ulink url="smb.conf.5.html#ENCRYPTPASSWORDS">
<parameter>encrypt passwords</parameter></ulink> set to <constant>yes
</constant> in order for your users to authenticate to the NT PDC.
</para>

<para>
Finally, add (or modify) a <ulink url="smb.conf.5.html#PASSWORDSERVER">
<parameter>password server =</parameter></ulink> line in the [global]
section to read: 
</para>

<para>
<programlisting>
        <command>password server = DOMPDC DOMBDC1 DOMBDC2</command>
</programlisting>
</para>

<para>
These are the primary and backup domain controllers Samba 
will attempt to contact in order to authenticate users. Samba will 
try to contact each of these servers in order, so you may want to 
rearrange this list in order to spread out the authentication load 
among domain controllers.
</para>

<para>
Alternatively, if you want smbd to automatically determine 
the list of Domain controllers to use for authentication, you may 
set this line to be:
</para>

<para>
<programlisting>
        <command>password server = *</command>
</programlisting>
</para>

<para>
This method, allows Samba to use exactly the same mechanism that NT does. This 
method either broadcasts or uses a WINS database in order to
find domain controllers to authenticate against.
</para>

<para>
In order to actually join the domain, you must run this command:
</para>

<para>
<programlisting>
        <prompt>root# </prompt><userinput>net join -S DOMPDC -U<replaceable>Administrator%password</replaceable></userinput>
</programlisting>
</para>

<para>
If the <userinput>-S DOMPDC</userinput> argument is not given then
the domain name will be obtained from smb.conf.
</para>

<para>
As we are joining the domain DOM and the PDC for that domain 
(the only machine that has write access to the domain SAM database) 
is DOMPDC. The <replaceable>Administrator%password</replaceable> is 
the login name and password for an account which has the necessary 
privilege to add machines to the domain.  If this is successful 
you will see the message:
</para>

<para>
<computeroutput>Joined domain DOM.</computeroutput>
or <computeroutput>Joined 'SERV1' to realm 'MYREALM'</computeroutput>
</para>

<para>
in your terminal window. See the <ulink url="net.8.html">
net(8)</ulink> man page for more details.
</para>

<para>
This process joins the server to the domain without having to create the machine
trust account on the PDC beforehand.
</para>

<para>
This command goes through the machine account password 
change protocol, then writes the new (random) machine account 
password for this Samba server into a file in the same directory 
in which an smbpasswd file would be stored - normally :
</para>

<para>
<filename>/usr/local/samba/private/secrets.tdb</filename>
</para>

<para>
This file is created and owned by root and is not 
readable by any other user. It is the key to the domain-level 
security for your system, and should be treated as carefully 
as a shadow password file.
</para>

<para>
Finally, restart your Samba daemons and get ready for 
clients to begin using domain security!
</para>

</sect2>

<sect2>
<title>Why is this better than security = server?</title>

<para>
Currently, domain security in Samba doesn't free you from 
having to create local Unix users to represent the users attaching 
to your server. This means that if domain user <constant>DOM\fred
</constant> attaches to your domain security Samba server, there needs 
to be a local Unix user fred to represent that user in the Unix 
filesystem. This is very similar to the older Samba security mode 
<ulink url="smb.conf.5.html#SECURITYEQUALSSERVER">security = server</ulink>, 
where Samba would pass through the authentication request to a Windows 
NT server in the same way as a Windows 95 or Windows 98 server would.
</para>

<para>
Please refer to the <ulink url="winbind.html">Winbind 
paper</ulink> for information on a system to automatically
assign UNIX uids and gids to Windows NT Domain users and groups.
</para>

<para>
The advantage to domain-level security is that the 
authentication in domain-level security is passed down the authenticated 
RPC channel in exactly the same way that an NT server would do it. This 
means Samba servers now participate in domain trust relationships in 
exactly the same way NT servers do (i.e., you can add Samba servers into 
a resource domain and have the authentication passed on from a resource
domain PDC to an account domain PDC).
</para>

<para>
In addition, with <command>security = server</command> every Samba 
daemon on a server has to keep a connection open to the 
authenticating server for as long as that daemon lasts. This can drain 
the connection resources on a Microsoft NT server and cause it to run 
out of available connections. With <command>security = domain</command>, 
however, the Samba daemons connect to the PDC/BDC only for as long 
as is necessary to authenticate the user, and then drop the connection, 
thus conserving PDC connection resources.
</para>

<para>
And finally, acting in the same manner as an NT server 
authenticating to a PDC means that as part of the authentication 
reply, the Samba server gets the user identification information such 
as the user SID, the list of NT groups the user belongs to, etc. 
</para>

<note>
<para>
Much of the text of this document 
was first published in the Web magazine <ulink url="http://www.linuxworld.com">         
LinuxWorld</ulink> as the article <ulink
url="http://www.linuxworld.com/linuxworld/lw-1998-10/lw-10-samba.html">Doing 
the NIS/NT Samba</ulink>.
</para>
</note>

</sect2>
</sect1>

<sect1>
<title>Samba ADS Domain Membership</title>

<para>
This is a rough guide to setting up Samba 3.0 with kerberos authentication against a
Windows2000 KDC. 
</para> 

<sect2>
<title>Setup your <filename>smb.conf</filename></title>

<para>
You must use at least the following 3 options in smb.conf:
</para>

<para><programlisting>
        realm = your.kerberos.REALM
        security = ADS
        encrypt passwords = yes
</programlisting></para>

<para>
In case samba can't figure out your ads server using your realm name, use the 
<command>ads server</command> option in <filename>smb.conf</filename>:
<programlisting>
        ads server = your.kerberos.server
</programlisting>
</para>

<note><para>
You do *not* need a smbpasswd file, and older clients will be authenticated as if
<command>security = domain</command>, although it won't do any harm and allows you
to have local users not in the domain. I expect that the above required options will
change soon when we get better active directory integration.
</para></note>

</sect2>
  
<sect2>
<title>Setup your <filename>/etc/krb5.conf</filename></title>

<para>
Note: you will need the krb5 workstation, devel, and libs installed
</para>

<para>
The minimal configuration for <filename>krb5.conf</filename> is:
</para>

<para><programlisting>
        [realms]
            YOUR.KERBEROS.REALM = {
                kdc = your.kerberos.server
            }
</programlisting></para>

<para>
Test your config by doing a <userinput>kinit
<replaceable>USERNAME</replaceable>@<replaceable>REALM</replaceable></userinput> and
making sure that your password is accepted by the Win2000 KDC.
</para>

<note><para>
The realm must be uppercase or you will get "Cannot find KDC for requested
realm while getting initial credentials" error
</para></note>

<note><para>
Time between the two servers must be synchronized.  You will get a
"kinit(v5): Clock skew too great while getting initial credentials" if the time
difference is more than five minutes. 
</para></note>

<para>
You also must ensure that you can 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 (ie. the hostname with no
domain attached) or it can alternatively be the netbios name
followed by the realm. 
</para>

<para>
The easiest way to ensure you get this right is to add a 
<filename>/etc/hosts</filename> entry mapping the IP address of your KDC to 
its netbios name. If you don't get this right then you will get a 
"local error" when you try to join the realm.
</para>

<para>
If all you want is kerberos support in &smbclient; then you can skip
straight to <link linkend="ads-test-smbclient">Test with &smbclient;</link> now. 
<link linkend="ads-create-machine-account">Creating a computer account</link> 
and <link linkend="ads-test-server">testing your servers</link>
is only needed if you want kerberos support for &smbd; and &winbindd;.
</para>

</sect2>

<sect2 id="ads-create-machine-account">
<title>Create the computer account</title>

<para>
As a user that has write permission on the Samba private directory
(usually root) run:
<programlisting>
        <userinput>net join -U Administrator%password</userinput>
</programlisting>
</para>

<sect3>
<title>Possible errors</title>

<para>
<variablelist>
        <varlistentry><term>"ADS support not compiled in"</term>
        <listitem><para>Samba must be reconfigured (remove config.cache) and recompiled
        (make clean all install) after the kerberos libs and headers are installed.
        </para></listitem></varlistentry>

        <varlistentry><term>net join prompts for user name</term>
        <listitem><para>You need to login to the domain using <userinput>kinit
        <replaceable>USERNAME</replaceable>@<replaceable>REALM</replaceable></userinput>.
        <replaceable>USERNAME</replaceable> must be a user who has rights to add a machine
        to the domain.  </para></listitem></varlistentry>
</variablelist>
</para>

</sect3>

</sect2>

<sect2 id="ads-test-server">
<title>Test your server setup</title>

<para>
If the join was successful, you will see a new computer account with the
NetBIOS name of your Samba server in Active Directory (in the "Computers"
folder under Users and Computers.
</para>

<para>
On a Windows 2000 client try <userinput>net use * \\server\share</userinput>. You should
be logged in with kerberos without needing to know a password. If
this fails then run <userinput>klist tickets</userinput>. Did you get a ticket for the
server? Does it have an encoding type of DES-CBC-MD5 ? 
</para>

</sect2>

<sect2 id="ads-test-smbclient">
<title>Testing with &smbclient;</title>

<para>
On your Samba server try to login to a Win2000 server or your Samba
server using &smbclient; and kerberos. Use &smbclient; as usual, but
specify the <parameter>-k</parameter> option to choose kerberos authentication.
</para>

</sect2>

<sect2>
<title>Notes</title>

<para>
You must change administrator password at least once after DC 
install, to create the right encoding types
</para>

<para>
w2k doesn't seem to create the _kerberos._udp and _ldap._tcp in
their defaults DNS setup. Maybe fixed in service packs?
</para>

</sect2>

</sect1>
</chapter>