samba-mirror/docs/docbook/projdoc/InterdomainTrusts.xml

<chapter id="InterdomainTrusts">
<chapterinfo>
	&author.jht;
	&author.mimir;
	<pubdate>April 3, 2003</pubdate>
</chapterinfo>

<title>Interdomain Trust Relationships</title>

<para>
Samba-3 supports NT4 style domain trust relationships. This is feature that many sites
will want to use if they migrate to Samba-3 from and NT4 style domain and do NOT want to
adopt Active Directory or an LDAP based authentication back end. This section explains
some background information regarding trust relationships and how to create them. It is now
possible for Samba-3 to NT4 trust (and vice versa), as well as Samba3 to Samba3 trusts.
</para>

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

<para>
Samba-3 can participate in Samba-to-Samba as well as in Samba-to-MS Windows NT4 style
trust relationships. This imparts to Samba similar scalability as is possible with
MS Windows NT4.
</para>

<para>
Given that Samba-3 has the capability to function with a scalable backend authentication
database such as LDAP, and given it's ability to run in Primary as well as Backup Domain control
modes, the administrator would be well advised to consider alternatives to the use of
Interdomain trusts simplt because by the very nature of how this works it is fragile.
That was after all a key reason for the development and adoption of Microsoft Active Directory.
</para>

</sect1>

<sect1>
<title>Trust Relationship Background</title>

<para>
MS Windows NT3.x/4.0 type security domains employ a non-hierarchical security structure.
The limitations of this architecture as it affects the scalability of MS Windows networking
in large organisations is well known. Additionally, the flat-name space that results from
this design significantly impacts the delegation of administrative responsibilities in
large and diverse organisations.
</para>

<para>
Microsoft developed Active Directory Service (ADS), based on Kerberos and LDAP, as a means
of circumventing the limitations of the older technologies. Not every organisation is ready
or willing to embrace ADS. For small companies the older NT4 style domain security paradigm
is quite adequate, there thus remains an entrenched user base for whom there is no direct
desire to go through a disruptive change to adopt ADS.
</para>

<para>
Microsoft introduced with MS Windows NT the ability to allow differing security domains
to affect a mechanism so that users from one domain may be given access rights and privileges
in another domain. The language that describes this capability is couched in terms of
<emphasis>Trusts</emphasis>. Specifically, one domain will <emphasis>trust</emphasis> the users
from another domain. The domain from which users are available to another security domain is
said to be a trusted domain. The domain in which those users have assigned rights and privileges
is the trusting domain. With NT3.x/4.0 all trust relationships are always in one direction only,
thus if users in both domains are to have privileges and rights in each others' domain, then it is
necessary to establish two (2) relationships, one in each direction.
</para>

<para>
In an NT4 style MS security domain, all trusts are non-transitive. This means that if there
are three (3) domains (let's call them RED, WHITE, and BLUE) where RED and WHITE have a trust
relationship, and WHITE and BLUE have a trust relationship, then it holds that there is no
implied trust between the RED and BLUE domains. ie: Relationships are explicit and not
transitive.
</para>

<para>
New to MS Windows 2000 ADS security contexts is the fact that trust relationships are two-way
by default. Also, all inter-ADS domain trusts are transitive. In the case of the RED, WHITE and BLUE
domains above, with Windows 2000 and ADS the RED and BLUE domains CAN trust each other. This is
an inherent feature of ADS domains. Samba-3 implements MS Windows NT4
style Interdomain trusts and interoperates with MS Windows 200x ADS
security domains in similar manner to MS Windows NT4 style domains.
</para>

</sect1>

<sect1>
<title>Native MS Windows NT4 Trusts Configuration</title>

<para>
There are two steps to creating an interdomain trust relationship.
</para>

<sect2>
<title>NT4 as the Trusting Domain (ie. creating the trusted account)</title>

<para>
For MS Windows NT4, all domain trust relationships are configured using the 
<application>Domain User Manager</application>. To affect a two way trust relationship it is 
necessary for each domain administrator to make available (for use by an external domain) it's 
security resources. This is done from the Domain User Manager Policies entry on the menu bar. 
From the <guimenu>Policy</guimenu> menu, select <guimenuitem>Trust Relationships</guimenuitem>, then
next to the lower box that is labelled <guilabel>Permitted to Trust this Domain</guilabel> are two 
buttons, <guibutton>Add</guibutton> and <guibutton>Remove</guibutton>. The <guibutton>Add</guibutton>
button will open a panel in which needs to be entered the remote domain that will be able to assign
user rights to your domain. In addition it is necessary to enter a password
that is specific to this trust relationship. The password needs to be
typed twice (for standard confirmation).
</para>

</sect2>

<sect2>
<title>NT4 as the Trusted Domain (ie. creating trusted account's password)</title>

<para>
A trust relationship will work only when the other (trusting) domain makes the appropriate connections
with the trusted domain. To consumate the trust relationship the administrator will launch the
Domain User Manager, from the menu select Policies, then select Trust Relationships, then click on the
<guibutton>Add</guibutton> button that is next to the box that is labelled 
<guilabel>Trusted Domains</guilabel>. A panel will open in which must be entered the name of the remote 
domain as well as the password assigned to that trust.
</para>

</sect2>
</sect1>

<sect1>
<title>Configuring Samba NT-style Domain Trusts</title>

<para>
This description is meant to be a fairly short introduction about how to set up a Samba server so
that it could participate in interdomain trust relationships. Trust relationship support in Samba
is in its early stage, so lot of things don't work yet.
</para>

<para>
Each of the procedures described below is treated as they were performed with Windows NT4 Server on
one end. The remote end could just as well be another Samba-3 domain. It can be clearly seen, after
reading this document, that combining Samba-specific parts of what's written below leads to trust
between domains in purely Samba environment.
</para>

<sect2>
<title>Samba-3 as the Trusting Domain</title>

<para>
In order to set the Samba PDC to be the trusted party of the relationship first you need
to create special account for the domain that will be the trusting party. To do that,
you can use the 'smbpasswd' utility. Creating the trusted domain account is very
similiar to creating a trusted machine account. Suppose, your domain is
called SAMBA, and the remote domain is called RUMBA. The first step
will be to issue this command from your favourite shell:
</para>

<para>
<screen>
&rootprompt; <userinput>smbpasswd -a -i rumba</userinput>
	New SMB password: XXXXXXXX
	Retype SMB password: XXXXXXXX
	Added user rumba$
</screen>

where <option>-a</option> means to add a new account into the
passdb database and <option>-i</option> means: ''create this
account with the InterDomain trust flag''
</para>

<para>
The account name will be 'rumba$' (the name of the remote domain)
</para>

<para>
After issuing this command you'll be asked to enter the password for
the account. You can use any password you want, but be aware that Windows NT will
not change this password until 7 days following account creation.
After the command returns successfully, you can look at the entry for the new account
(in the stardard way depending on your configuration) and see that account's name is
really RUMBA$ and it has 'I' flag in the flags field. Now you're ready to confirm
the trust by establishing it from Windows NT Server.
</para>

<para>
Open <application>User Manager for Domains</application> and from menu
<guimenu>Policies</guimenu> select <guimenuitem>Trust Relationships...</guimenuitem>.
Right beside <guilabel>Trusted domains</guilabel> list box press the 
<guimenu>Add...</guimenu> button. You will be prompted for
the trusted domain name and the relationship password. Type in SAMBA, as this is
your domain name, and the password used at the time of account creation.
Press OK and, if everything went without incident, you will see 
<computeroutput>Trusted domain relationship successfully 
established</computeroutput> message.
</para>

</sect2>
<sect2>
<title>Samba-3 as the Trusted Domain</title>

<para>
This time activities are somewhat reversed. Again, we'll assume that your domain
controlled by the Samba PDC is called SAMBA and NT-controlled domain is called RUMBA.
</para>

<para>
The very first thing requirement is to add an account for the SAMBA domain on RUMBA's PDC.
</para>

<para>
Launch the <application>Domain User Manager</application>, then from the menu select
<guimenu>Policies</guimenu>, <guimenuitem>Trust Relationships</guimenuitem>.
Now, next to <guilabel>Trusted Domains</guilabel> box press the <guibutton>Add</guibutton>
button, and type in the name of the trusted domain (SAMBA) and password securing
the relationship.
</para>

<para>
The password can be arbitrarily chosen. It is easy to change the password
from the Samba server whenever you want. After confirming the password your account is
ready for use. Now it's Samba's turn.
</para>

<para>
Using your favourite shell while being logged in as root, issue this command:
</para>

<para>
&rootprompt;<userinput>net rpc trustdom establish rumba</userinput>
</para>

<para>
You will be prompted for the password you just typed on your Windows NT4 Server box.
Do not worry if you see an error message that mentions a returned code of
<errorname>NT_STATUS_NOLOGON_INTERDOMAIN_TRUST_ACCOUNT</errorname>. It means the
password you gave is correct and the NT4 Server says the account is
ready for interdomain connection and not for ordinary
connection. After that, be patient it can take a while (especially
in large networks), you should see the <computeroutput>Success</computeroutput> message.
Congratulations! Your trust relationship has just been established.
</para>

<note><para>
Note that you have to run this command as root because you must have write access to
the <filename>secrets.tdb</filename> file.
</para></note>

</sect2>
</sect1>

<sect1>
<title>Common Errors</title>

<para>
Interdomain trust relationships should NOT be attempted on networks that are unstable
or that suffer regular outages. Network stability and integrity are key concerns with
distributed trusted domains.
</para>

	<sect2>
	<title>Tell me about Trust Relationships using Samba</title>

	<para>
	Like many, I administer multiple LANs connected together using NT trust
	relationships.  This was implemented about 4 years ago.  I now have the
	occasion to consider performing this same task again, but this time, I
	would like to implement it solely through samba - no Microsoft PDCs
	anywhere.
	</para>

	<para>
	I have read documentation on samba.org regarding NT-style trust
	relationships and am now wondering, can I do what I want to?  I already
	have successfully implemented 2 samba servers, but they are not PDCs.
	They merely act as file servers.  I seem to remember, and it appears to
	be true (according to samba.org) that trust relationships are a
	challenge.
	</para>

	<para>
	Please provide any helpful feedback that you may have.
	</para>

	<para>
	These are almost complete in Samba 3.0 snapshots.  The main catch
	is getting winbindd to be able to allocate uid/gid's for trusted
	users/groups.  See the updated Samba HOWTO collection for more
	details.
	</para>

	</sect2>

</sect1>

</chapter>