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<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 16. Interdomain Trust Relationships</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.61.2"><link rel="home" href="index.html" title="Samba HOWTO Collection"><link rel="up" href="optional.html" title="Part III. Advanced Configuration"><link rel="previous" href="securing-samba.html" title="Chapter 15. Securing Samba"><link rel="next" href="msdfs.html" title="Chapter 17. Hosting a Microsoft Distributed File System Tree"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 16. Interdomain Trust Relationships</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="securing-samba.html">Prev</a> </td><th width="60%" align="center">Part III. Advanced Configuration</th><td width="20%" align="right"> <a accesskey="n" href="msdfs.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="InterdomainTrusts"></a>Chapter 16. Interdomain Trust Relationships</h2></div><div><div class="author"><h3 class="author"><span class="firstname">John</span> <span class="othername">H.</span> <span class="surname">Terpstra</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><tt class="email"><<a href="mailto:jht@samba.org">jht@samba.org</a>></tt></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">Rafal</span> <span class="surname">Szczesniak</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><tt class="email"><<a href="mailto:mimir@samba.org">mimir@samba.org</a>></tt></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">Jelmer</span> <span class="othername">R.</span> <span class="surname">Vernooij</span></h3><span class="contrib">drawing</span><div class="affiliation"><span class="orgname">The Samba Team<br></span><div class="address"><p><tt class="email"><<a href="mailto:jelmer@samba.org">jelmer@samba.org</a>></tt></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">Stephen</span> <span class="surname">Langasek</span></h3><div class="affiliation"><div class="address"><p><tt class="email"><<a href="mailto:vorlon@netexpress.net">vorlon@netexpress.net</a>></tt></p></div></div></div></div><div><p class="pubdate">April 3, 2003</p></div></div><div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="InterdomainTrusts.html#id2923951">Features and Benefits</a></dt><dt><a href="InterdomainTrusts.html#id2923980">Trust Relationship Background</a></dt><dt><a href="InterdomainTrusts.html#id2924063">Native MS Windows NT4 Trusts Configuration</a></dt><dd><dl><dt><a href="InterdomainTrusts.html#id2924091">Creating an NT4 Domain Trust</a></dt><dt><a href="InterdomainTrusts.html#id2924164">Completing an NT4 Domain Trust</a></dt><dt><a href="InterdomainTrusts.html#id2924223">Inter-Domain Trust Facilities</a></dt></dl></dd><dt><a href="InterdomainTrusts.html#id2924421">Configuring Samba NT-Style Domain Trusts</a></dt><dd><dl><dt><a href="InterdomainTrusts.html#samba-trusted-domain">Samba as the Trusted Domain</a></dt><dt><a href="InterdomainTrusts.html#id2924648">Samba as the Trusting Domain</a></dt></dl></dd><dt><a href="InterdomainTrusts.html#id2924790">NT4-Style Domain Trusts with Windows 2000</a></dt><dt><a href="InterdomainTrusts.html#id2924898">Common Errors</a></dt><dd><dl><dt><a href="InterdomainTrusts.html#id2924912">Browsing of Trusted Domain Fails</a></dt><dt><a href="InterdomainTrusts.html#id2924962">Problems With LDAP ldapsam And The smbldap-tools</a></dt></dl></dd></dl></div><p>
<a class="indexterm" name="id2923934"></a>
Samba-3 supports NT4-style domain trust relationships. This is a feature that many sites
will want to use if they migrate to Samba-3 from an NT4-style domain and do not want to
adopt Active Directory or an LDAP-based authentication backend. This section explains
some background information regarding trust relationships and how to create them. It is now
possible for Samba-3 to trust NT4 (and vice versa), as well as to create Samba-to-Samba
trusts.
</p><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2923951"></a>Features and Benefits</h2></div></div><div></div></div><p>
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 with MS Windows NT4.
</p><p>
Given that Samba-3 has the capability to function with a scalable backend authentication
database such as LDAP, and given its 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 simply 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.
</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2923980"></a>Trust Relationship Background</h2></div></div><div></div></div><p>
MS Windows NT3/4 type security domains employ a non-hierarchical security structure.
The limitations of this architecture as it effects the scalability of MS Windows networking
in large organizations is well known. Additionally, the flat namespace that results from
this design significantly impacts the delegation of administrative responsibilities in
large and diverse organizations.
</p><p>
Microsoft developed Active Directory Service (ADS), based on Kerberos and LDAP, as a means
of circumventing the limitations of the older technologies. Not every organization is ready
or willing to embrace ADS. For small companies the older NT4-style domain security paradigm
is quite adequate, there remains an entrenched user base for whom there is no direct
desire to go through a disruptive change to adopt ADS.
</p><p>
With MS Windows NT, Microsoft introduced the ability to allow differing security domains
to effect a mechanism so 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
<span class="emphasis"><em>Trusts</em></span>. Specifically, one domain will <span class="emphasis"><em>trust</em></span> 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 relationships, one in each direction.
</p><p>
In an NT4-style MS security domain, all trusts are non-transitive. This means that if there
are three 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. Relationships are explicit and not
transitive.
</p><p>
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.
</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2924063"></a>Native MS Windows NT4 Trusts Configuration</h2></div></div><div></div></div><p>
There are two steps to creating an interdomain trust relationship. To effect a two-way trust
relationship, it is necessary for each domain administrator to create a trust account for the
other domain to use in verifying security credentials.
<a class="indexterm" name="id2924080"></a>
</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2924091"></a>Creating an NT4 Domain Trust</h3></div></div><div></div></div><p>
For MS Windows NT4, all domain trust relationships are configured using the
<span class="application">Domain User Manager</span>. This is done from the Domain User Manager Policies
entry on the menu bar. From the <span class="guimenu">Policy</span> menu, select
<span class="guimenuitem">Trust Relationships</span>. Next to the lower box labeled
<span class="guilabel">Permitted to Trust this Domain</span> are two buttons, <span class="guibutton">Add</span>
and <span class="guibutton">Remove</span>. The <span class="guibutton">Add</span> button will open a panel in which
to enter the name of the remote domain that will be able to assign access rights to users in
your domain. You will also need to enter a password for this trust relationship, which the
trusting domain will use when authenticating users from the trusted domain.
The password needs to be typed twice (for standard confirmation).
</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2924164"></a>Completing an NT4 Domain Trust</h3></div></div><div></div></div><p>
<a class="indexterm" name="id2924175"></a>
A trust relationship will work only when the other (trusting) domain makes the appropriate connections
with the trusted domain. To consummate the trust relationship, the administrator will launch the
Domain User Manager from the menu select <span class="guilabel">Policies</span>, then select
<span class="guilabel">Trust Relationships</span>, click on the <span class="guibutton">Add</span> button
next to the box that is labeled <span class="guilabel">Trusted Domains</span>. A panel will open in which
must be entered the name of the remote domain as well as the password assigned to that trust.
</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2924223"></a>Inter-Domain Trust Facilities</h3></div></div><div></div></div><p>
<a class="indexterm" name="id2924235"></a>
A two-way trust relationship is created when two one-way trusts are created, one in each direction.
Where a one-way trust has been established between two MS Windows NT4 domains (let's call them
DomA and DomB), the following facilities are created:
</p><div class="figure"><a name="trusts1"></a><p class="title"><b>Figure 16.1. Trusts overview.</b></p><div class="mediaobject"><img src="images/trusts1.png" width="270" alt="Trusts overview."></div></div><div class="itemizedlist"><ul type="disc"><li><p>
DomA (completes the trust connection) <i class="parameter"><tt>Trusts</tt></i> DomB.
</p></li><li><p>
DomA is the <i class="parameter"><tt>Trusting</tt></i> domain.
</p></li><li><p>
DomB is the <i class="parameter"><tt>Trusted</tt></i> domain (originates the trust account).
</p></li><li><p>
Users in DomB can access resources in DomA.
</p></li><li><p>
Users in DomA cannot access resources in DomB.
</p></li><li><p>
Global groups from DomB can be used in DomA.
</p></li><li><p>
Global groups from DomA cannot be used in DomB.
</p></li><li><p>
DomB does appear in the logon dialog box on client workstations in DomA.
</p></li><li><p>
DomA does not appear in the logon dialog box on client workstations in DomB.
</p></li></ul></div><div class="itemizedlist"><ul type="disc"><li><p>
Users/Groups in a trusting domain cannot be granted rights, permissions or access
to a trusted domain.
</p></li><li><p>
The trusting domain can access and use accounts (Users/Global Groups) in the
trusted domain.
</p></li><li><p>
Administrators of the trusted domain can be granted administrative rights in the
trusting domain.
</p></li><li><p>
Users in a trusted domain can be given rights and privileges in the trusting
domain.
</p></li><li><p>
Trusted domain Global Groups can be given rights and permissions in the trusting
domain.
</p></li><li><p>
Global Groups from the trusted domain can be made members in Local Groups on
MS Windows Domain Member machines.
</p></li></ul></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2924421"></a>Configuring Samba NT-Style Domain Trusts</h2></div></div><div></div></div><p>
This description is meant to be a fairly short introduction about how to set up a Samba server so
that it can participate in interdomain trust relationships. Trust relationship support in Samba
is at an early stage, so do not be surprised if something does not function as it should.
</p><p>
Each of the procedures described below assumes the peer domain in the trust relationship is
controlled by a Windows NT4 server. However, 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 a purely Samba
environment.
</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="samba-trusted-domain"></a>Samba as the Trusted Domain</h3></div></div><div></div></div><p>
In order to set the Samba PDC to be the trusted party of the relationship, you first need
to create a special account for the domain that will be the trusting party. To do that,
you can use the <b class="command">smbpasswd</b> utility. Creating the trusted domain account is
similar 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 favorite shell:
</p><p>
</p><pre class="screen">
<tt class="prompt">root# </tt> <b class="userinput"><tt>smbpasswd -a -i rumba</tt></b>
New SMB password: <b class="userinput"><tt>XXXXXXXX</tt></b>
Retype SMB password: <b class="userinput"><tt>XXXXXXXX</tt></b>
Added user rumba$
</pre><p>
where <tt class="option">-a</tt> means to add a new account into the
passdb database and <tt class="option">-i</tt> means: “<span class="quote"><span class="emphasis"><em>create this
account with the Inter-Domain trust flag</em></span></span>”.
</p><p>
The account name will be “<span class="quote"><span class="emphasis"><em>rumba$</em></span></span>” (the name of the remote domain).
If this fails, you should check that the trust account has been added to the system
password database (<tt class="filename">/etc/passwd</tt>). If it has not been added, you
can add it manually and then repeat the step above.
</p><p>
After issuing this command, you will be asked to enter the password for
the account. You can use any password you want, but be aware that Windows NT will
not change this password until seven days following account creation.
After the command returns successfully, you can look at the entry for the new account
(in the standard way as appropriate for your configuration) and see that accounts name is
really RUMBA$ and it has the “<span class="quote"><span class="emphasis"><em>I</em></span></span>” flag set in the flags field. Now you are ready to confirm
the trust by establishing it from Windows NT Server.
</p><p>
<a class="indexterm" name="id2924583"></a>
Open <span class="application">User Manager for Domains</span> and from the
<span class="guimenu">Policies</span> menu, select <span class="guimenuitem">Trust Relationships...</span>.
Beside the <span class="guilabel">Trusted domains</span> list box click the
<span class="guimenu">Add...</span> button. You will be prompted for
the trusted domain name and the relationship password. Type in SAMBA, as this is
the name of the remote domain and the password used at the time of account creation.
Click on <span class="guibutton">OK</span> and, if everything went without incident, you will see
the <tt class="computeroutput">Trusted domain relationship successfully
established</tt> message.
</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2924648"></a>Samba as the Trusting Domain</h3></div></div><div></div></div><p>
This time activities are somewhat reversed. Again, we'll assume that your domain
controlled by the Samba PDC is called SAMBA and the NT-controlled domain is called RUMBA.
</p><p>
The very first step is to add an account for the SAMBA domain on RUMBA's PDC.
</p><p>
<a class="indexterm" name="id2924673"></a>
Launch the <span class="application">Domain User Manager</span>, then from the menu select
<span class="guimenu">Policies</span>, <span class="guimenuitem">Trust Relationships</span>.
Now, next to the <span class="guilabel">Trusted Domains</span> box press the <span class="guibutton">Add</span>
button and type in the name of the trusted domain (SAMBA) and the password to use in securing
the relationship.
</p><p>
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 its Samba's turn.
</p><p>
Using your favorite shell while being logged in as root, issue this command:
</p><p>
<tt class="prompt">root# </tt><b class="userinput"><tt>net rpc trustdom establish rumba</tt></b>
</p><p>
You will be prompted for the password you just typed on your Windows NT4 Server box.
An error message <span class="errorname">`NT_STATUS_NOLOGON_INTERDOMAIN_TRUST_ACCOUNT'</span>
that may be reported periodically is of no concern and may safely be ignored.
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), but eventually you should see
the <tt class="computeroutput">Success</tt> message. Congratulations! Your trust
relationship has just been established.
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
You have to run this command as root because you must have write access to
the <tt class="filename">secrets.tdb</tt> file.
</p></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2924790"></a>NT4-Style Domain Trusts with Windows 2000</h2></div></div><div></div></div><p>
Although <span class="application">Domain User Manager</span> is not present in Windows 2000, it is
also possible to establish an NT4-style trust relationship with a Windows 2000 domain
controller running in mixed mode as the trusting server. It should also be possible for
Samba to trust a Windows 2000 server, however, more testing is still needed in this area.
</p><p>
After <a href="InterdomainTrusts.html#samba-trusted-domain" title="Samba as the Trusted Domain">creating the interdomain trust account on the
Samba server</a> as described above, open <span class="application">Active Directory Domains and
Trusts</span> on the AD controller of the domain whose resources you wish Samba users
to have access to. Remember that since NT4-style trusts are not transitive, if you want
your users to have access to multiple mixed-mode domains in your AD forest, you will need to
repeat this process for each of those domains. With <span class="application">Active Directory Domains
and Trusts</span> open, right-click on the name of the Active Directory domain that
will trust our Samba domain and choose <span class="guimenuitem">Properties</span>, then click on
the <span class="guilabel">Trusts</span> tab. In the upper part of the panel, you will see a list box
labeled <span class="guilabel">Domains trusted by this domain:</span>, and an
<span class="guilabel">Add...</span> button next to it. Press this button and just as with NT4, you
will be prompted for the trusted domain name and the relationship password. Press OK and
after a moment, Active Directory will respond with <tt class="computeroutput">The trusted domain has
been added and the trust has been verified.</tt> Your Samba users can now be
granted access to resources in the AD domain.
</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2924898"></a>Common Errors</h2></div></div><div></div></div><p>
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.
</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2924912"></a>Browsing of Trusted Domain Fails</h3></div></div><div></div></div><p>
Browsing from a machine in a trusted Windows 200x Domain to a Windows 200x member of
a trusting samba domain, I get the following error:
</p><p><span class="emphasis"><em>
The system detected a possible attempt to compromise security. Please ensure that
you can contact the server that authenticated you.</em></span></p><p>
The event logs on the box I'm trying to connect to have entries regarding group
policy not being applied because it is a member of a down-level domain.
</p><p><span class="emphasis"><em>Answer: </em></span> If there is a computer account in the Windows
200x Domain for the machine in question, and it is disabled, this problem can
occur. If there is no computer account (removed or never existed), or if that
account is still intact (i.e.: you just joined it to another domain) everything
seems to be fine. By default, when you un-join a domain (the Windows 200x
Domain), the computer tries to automatically disable the computer account in
the domain. If you are running as an account which has privileges to do this
when you un-join the machine, it is done, otherwise it is not done.
</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2924962"></a>Problems With LDAP ldapsam And The smbldap-tools</h3></div></div><div></div></div><p>
If you use the <b class="command">smbldap-useradd.pl</b> script to create a trust
account to set up Interdomain trusts the process of setting up the trust will
fail. The account that was created in the LDAP database will have an account
flags field that has <tt class="constant">[W ]</tt>, when it must have
<tt class="constant">[I ]</tt> for Interdomain trusts to work.
</p><p><span class="emphasis"><em>Answer: </em></span>Here is a simple solution.
Create a machine account as follows:
</p><pre class="screen">
<tt class="prompt">root# </tt> smbldap-useradd.pl -w domain_name
</pre><p>
Then set the desired trust account password as shown here:
</p><pre class="screen">
<tt class="prompt">root# </tt> smbldap-passwd.pl domain_name\$
</pre><p>
Using a text editor, create the following file:
</p><pre class="screen">
dn: uid=domain_name$,ou=People,dc={your-domain},dc={your-top-level-domain}
changetype: modify
sambaAcctFlags: [I ]
</pre><p>
Then apply the text file to the LDAP database as follows:
</p><pre class="screen">
<tt class="prompt">root# </tt> ldapmodify -x -h localhost \
-D "cn=Manager,dc={your-domain},dc={your-top-level-domain}" \
-W -f /path-to/foobar
</pre><p>
Create a single-sided trust under the NT4 Domain User Manager, then execute:
</p><pre class="screen">
<tt class="prompt">root# </tt> net rpc trustdom establish domain_name
</pre><p>
</p><p>
It works with Samba-3 and NT4 Domains, and also with Samba-3 and Windows 200x ADS in mixed mode.
Both DC's, samba and NT, must have the same WINS server otherwise
the trust will never work.
</p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="securing-samba.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="optional.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="msdfs.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 15. Securing Samba </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 17. Hosting a Microsoft Distributed File System Tree</td></tr></table></div></body></html>