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1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 19. Interdomain Trust Relationships</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.70.1"><link rel="start" href="index.html" title="The Official Samba-3 HOWTO and Reference Guide"><link rel="up" href="optional.html" title="Part III. Advanced Configuration"><link rel="prev" href="securing-samba.html" title="Chapter 18. Securing Samba"><link rel="next" href="msdfs.html" title="Chapter 20. 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 19. 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 19. 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><code class="email"><<a href="mailto:jht@samba.org">jht@samba.org</a>></code></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><code class="email"><<a href="mailto:mimir@samba.org">mimir@samba.org</a>></code></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><code class="email"><<a href="mailto:jelmer@samba.org">jelmer@samba.org</a>></code></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><code class="email"><<a href="mailto:vorlon@netexpress.net">vorlon@netexpress.net</a>></code></p></div></div></div></div><div><p class="pubdate">April 3, 2003</p></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="InterdomainTrusts.html#id2623286">Features and Benefits</a></span></dt><dt><span class="sect1"><a href="InterdomainTrusts.html#id2623359">Trust Relationship Background</a></span></dt><dt><span class="sect1"><a href="InterdomainTrusts.html#id2623637">Native MS Windows NT4 Trusts Configuration</a></span></dt><dd><dl><dt><span class="sect2"><a href="InterdomainTrusts.html#id2623674">Creating an NT4 Domain Trust</a></span></dt><dt><span class="sect2"><a href="InterdomainTrusts.html#id2623770">Completing an NT4 Domain Trust</a></span></dt><dt><span class="sect2"><a href="InterdomainTrusts.html#id2623856">Interdomain Trust Facilities</a></span></dt></dl></dd><dt><span class="sect1"><a href="InterdomainTrusts.html#id2624064">Configuring Samba NT-Style Domain Trusts</a></span></dt><dd><dl><dt><span class="sect2"><a href="InterdomainTrusts.html#samba-trusted-domain">Samba as the Trusted Domain</a></span></dt><dt><span class="sect2"><a href="InterdomainTrusts.html#id2624405">Samba as the Trusting Domain</a></span></dt></dl></dd><dt><span class="sect1"><a href="InterdomainTrusts.html#id2624601">NT4-Style Domain Trusts with Windows 2000</a></span></dt><dt><span class="sect1"><a href="InterdomainTrusts.html#id2624750">Common Errors</a></span></dt><dd><dl><dt><span class="sect2"><a href="InterdomainTrusts.html#id2624763">Browsing of Trusted Domain Fails</a></span></dt><dt><span class="sect2"><a href="InterdomainTrusts.html#id2624809">Problems with LDAP ldapsam and Older Versions of smbldap-tools</a></span></dt></dl></dd></dl></div><p>
11 Samba-3 supports NT4-style domain trust relationships. This is a feature that many sites
12 will want to use if they migrate to Samba-3 from an NT4-style domain and do not want to
13 adopt Active Directory or an LDAP-based authentication backend. This chapter explains
14 some background information regarding trust relationships and how to create them. It is now
15 possible for Samba-3 to trust NT4 (and vice versa), as well as to create Samba-to-Samba
16 trusts.
17 </p><p>
23 The use of interdomain trusts requires use of <span><strong class="command">winbind</strong></span>, so the
24 <span><strong class="command">winbindd</strong></span> daemon must be running. Winbind operation in this mode is
25 dependent on the specification of a valid UID range and a valid GID range in the <code class="filename">smb.conf</code> file.
26 These are specified respectively using:
27 </p><table class="simplelist" border="0" summary="Simple list"><tr><td><a class="indexterm" name="id2623198"></a><em class="parameter"><code>idmap uid = 10000-20000</code></em></td></tr><tr><td><a class="indexterm" name="id2623211"></a><em class="parameter"><code>idmap gid = 10000-20000</code></em></td></tr></table><p>
32 The range of values specified must not overlap values used by the host operating system and must
33 not overlap values used in the passdb backend for POSIX user accounts. The maximum value is
34 limited by the upper-most value permitted by the host operating system. This is a UNIX kernel
36 (32-bit unsigned variable).
37 </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
41 The use of winbind is necessary only when Samba is the trusting domain, not when it is the
42 trusted domain.
43 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2623286"></a>Features and Benefits</h2></div></div></div><p>
46 Samba-3 can participate in Samba-to-Samba as well as in Samba-to-MS Windows NT4-style
47 trust relationships. This imparts to Samba scalability similar to that with MS Windows NT4.
48 </p><p>
54 Given that Samba-3 can function with a scalable backend authentication database such as LDAP, and given its
55 ability to run in primary as well as backup domain control modes, the administrator would be well-advised to
56 consider alternatives to the use of interdomain trusts simply because, by the very nature of how trusts
57 function, this system is fragile. That was, after all, a key reason for the development and adoption of
58 Microsoft Active Directory.
59 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2623359"></a>Trust Relationship Background</h2></div></div></div><p>
66 MS Windows NT3/4-type security domains employ a nonhierarchical security structure.
67 The limitations of this architecture as it effects the scalability of MS Windows networking
68 in large organizations is well known. Additionally, the flat namespace that results from
69 this design significantly impacts the delegation of administrative responsibilities in
70 large and diverse organizations.
71 </p><p>
77 Microsoft developed Active Directory Service (ADS), based on Kerberos and LDAP, as a means
78 of circumventing the limitations of the older technologies. Not every organization is ready
79 or willing to embrace ADS. For small companies the older NT4-style domain security paradigm
80 is quite adequate, and so there remains an entrenched user base for whom there is no direct
81 desire to go through a disruptive change to adopt ADS.
82 </p><p>
90 With Windows NT, Microsoft introduced the ability to allow different security domains
91 to effect a mechanism so users from one domain may be given access rights and privileges
92 in another domain. The language that describes this capability is couched in terms of
93 <span class="emphasis"><em>trusts</em></span>. Specifically, one domain will <span class="emphasis"><em>trust</em></span> the users
94 from another domain. The domain from which users can access another security domain is
95 said to be a trusted domain. The domain in which those users have assigned rights and privileges
96 is the trusting domain. With NT3.x/4.0 all trust relationships are always in one direction only,
97 so if users in both domains are to have privileges and rights in each others' domain, then it is
98 necessary to establish two relationships, one in each direction.
99 </p><p>
105 Further, in an NT4-style MS security domain, all trusts are nontransitive. This means that if there are three
106 domains (let's call them red, white, and blue), where red and white have a trust relationship, and white and
107 blue have a trust relationship, then it holds that there is no implied trust between the red and blue domains.
108 Relationships are explicit and not transitive.
109 </p><p>
117 New to MS Windows 2000 ADS security contexts is the fact that trust relationships are two-way by default.
118 Also, all inter-ADS domain trusts are transitive. In the case of the red, white, and blue domains, with
119 Windows 2000 and ADS, the red and blue domains can trust each other. This is an inherent feature of ADS
120 domains. Samba-3 implements MS Windows NT4-style interdomain trusts and interoperates with MS Windows 200x ADS
121 security domains in similar manner to MS Windows NT4-style domains.
122 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2623637"></a>Native MS Windows NT4 Trusts Configuration</h2></div></div></div><p>
126 There are two steps to creating an interdomain trust relationship. To effect a two-way trust
127 relationship, it is necessary for each domain administrator to create a trust account for the
128 other domain to use in verifying security credentials.
129 </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2623674"></a>Creating an NT4 Domain Trust</h3></div></div></div><p>
135 For MS Windows NT4, all domain trust relationships are configured using the
136 <span class="application">Domain User Manager</span>. This is done from the Domain User Manager Policies
139 <span class="guilabel">Permitted to Trust this Domain</span> are two buttons, <span class="guibutton">Add</span>
140 and <span class="guibutton">Remove</span>. The <span class="guibutton">Add</span> button will open a panel in which
141 to enter the name of the remote domain that will be able to assign access rights to users in
142 your domain. You will also need to enter a password for this trust relationship, which the
143 trusting domain will use when authenticating users from the trusted domain.
144 The password needs to be typed twice (for standard confirmation).
145 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2623770"></a>Completing an NT4 Domain Trust</h3></div></div></div><p>
152 A trust relationship will work only when the other (trusting) domain makes the appropriate connections
153 with the trusted domain. To consummate the trust relationship, the administrator launches the
155 <span class="guilabel">Trust Relationships</span>, and clicks on the <span class="guibutton">Add</span> button
156 next to the box that is labeled <span class="guilabel">Trusted Domains</span>. A panel opens in which
157 must be entered the name of the remote domain as well as the password assigned to that trust.
158 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2623856"></a>Interdomain Trust Facilities</h3></div></div></div><p>
165 A two-way trust relationship is created when two one-way trusts are created, one in each direction.
166 Where a one-way trust has been established between two MS Windows NT4 domains (let's call them
167 DomA and DomB), the following facilities are created:
168 </p><div class="figure"><a name="trusts1"></a><p class="title"><b>Figure 19.1. Trusts overview.</b></p><div class="figure-contents"><div class="mediaobject"><img src="images/trusts1.png" alt="Trusts overview."></div></div></div><br class="figure-break"><div class="itemizedlist"><ul type="disc"><li><p>
170 </p></li><li><p>
172 </p></li><li><p>
173 DomB is the <em class="parameter"><code>Trusted</code></em> domain (originates the trust account).
174 </p></li><li><p>
175 Users in DomB can access resources in DomA.
176 </p></li><li><p>
177 Users in DomA cannot access resources in DomB.
178 </p></li><li><p>
179 Global groups from DomB can be used in DomA.
180 </p></li><li><p>
181 Global groups from DomA cannot be used in DomB.
182 </p></li><li><p>
183 DomB does appear in the logon dialog box on client workstations in DomA.
184 </p></li><li><p>
185 DomA does not appear in the logon dialog box on client workstations in DomB.
187 Users and groups in a trusting domain cannot be granted rights, permissions, or access
188 to a trusted domain.
189 </p></li><li><p>
190 The trusting domain can access and use accounts (users/global groups) in the
191 trusted domain.
192 </p></li><li><p>
193 Administrators of the trusted domain can be granted administrative rights in the
194 trusting domain.
195 </p></li><li><p>
196 Users in a trusted domain can be given rights and privileges in the trusting
197 domain.
198 </p></li><li><p>
199 Trusted domain global groups can be given rights and permissions in the trusting
200 domain.
201 </p></li><li><p>
202 Global groups from the trusted domain can be made members in local groups on
203 MS Windows domain member machines.
204 </p></li></ul></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2624064"></a>Configuring Samba NT-Style Domain Trusts</h2></div></div></div><p>
206 This description is meant to be a fairly short introduction about how to set up a Samba server so
207 that it can participate in interdomain trust relationships. Trust relationship support in Samba
208 is at an early stage, so do not be surprised if something does not function as it should.
209 </p><p>
214 Each of the procedures described next assumes the peer domain in the trust relationship is controlled by a
215 Windows NT4 server. However, the remote end could just as well be another Samba-3 domain. It can be clearly
216 seen, after reading this document, that combining Samba-specific parts of what's written in the following
217 sections leads to trust between domains in a purely Samba environment.
218 </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><p>
224 In order to set the Samba PDC to be the trusted party of the relationship, you first need
225 to create a special account for the domain that will be the trusting party. To do that,
226 you can use the <span><strong class="command">smbpasswd</strong></span> utility. Creating the trusted domain account is
227 similar to creating a trusted machine account. Suppose, your domain is
228 called SAMBA, and the remote domain is called RUMBA. The first step
229 will be to issue this command from your favorite shell:
230 </p><p>
232 <code class="prompt">root# </code> <strong class="userinput"><code>smbpasswd -a -i rumba</code></strong>
235 Added user rumba$
236 </pre><p>
239 passdb database and <code class="option">-i</code> means to “<span class="quote">create this
241 </p><p>
246 The account name will be “<span class="quote">rumba$</span>” (the name of the remote domain).
247 If this fails, you should check that the trust account has been added to the system
249 can add it manually and then repeat the previous step.
250 </p><p>
255 After issuing this command, you will be asked to enter the password for the account. You can use any password
256 you want, but be aware that Windows NT will not change this password until 7 days following account creation.
257 After the command returns successfully, you can look at the entry for the new account (in the standard way as
258 appropriate for your configuration) and see that the account's name is really RUMBA$ and it has the
259 “<span class="quote">I</span>” flag set in the flags field. Now you are ready to confirm the trust by establishing it from
260 Windows NT Server.
261 </p><p>
267 Open <span class="application">User Manager for Domains</span> and from the <span class="guimenu">Policies</span> menu, select
268 <span class="guimenuitem">Trust Relationships...</span>. Beside the <span class="guilabel">Trusted domains</span> list box,
269 click the <span class="guimenu">Add...</span> button. You will be prompted for the trusted domain name and the
270 relationship password. Type in SAMBA, as this is the name of the remote domain and the password used at the
271 time of account creation. Click on <span class="guibutton">OK</span> and, if everything went without incident, you
272 will see the <code class="computeroutput">Trusted domain relationship successfully established</code> message.
273 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2624405"></a>Samba as the Trusting Domain</h3></div></div></div><p>
276 This time activities are somewhat reversed. Again, we'll assume that your domain
277 controlled by the Samba PDC is called SAMBA and the NT-controlled domain is called RUMBA.
278 </p><p>
279 The very first step is to add an account for the SAMBA domain on RUMBA's PDC.
280 </p><p>
286 Now, next to the <span class="guilabel">Trusted Domains</span> box, press the <span class="guibutton">Add</span>
287 button and type in the name of the trusted domain (SAMBA) and the password to use in securing
288 the relationship.
289 </p><p>
292 The password can be arbitrarily chosen. It is easy to change the password from the Samba server whenever you
293 want. After you confirm the password, your account is ready for use. Now its Samba's turn.
294 </p><p>
295 Using your favorite shell while logged in as root, issue this command:
297 </p><p>
298 <code class="prompt">root# </code><strong class="userinput"><code>net rpc trustdom establish rumba</code></strong>
299 </p><p>
303 You will be prompted for the password you just typed on your Windows NT4 Server box.
305 that may be reported periodically is of no concern and may safely be ignored.
306 It means the password you gave is correct and the NT4 server says the account is ready for
307 interdomain connection and not for ordinary connection. After that, be patient;
308 it can take a while (especially in large networks), but eventually you should see
310 relationship has just been established.
311 </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
312 You have to run this command as root because you must have write access to
314 </p></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2624601"></a>NT4-Style Domain Trusts with Windows 2000</h2></div></div></div><p>
319 Although <span class="application">Domain User Manager</span> is not present in Windows 2000, it is
320 also possible to establish an NT4-style trust relationship with a Windows 2000 domain
321 controller running in mixed mode as the trusting server. It should also be possible for
322 Samba to trust a Windows 2000 server; however, more testing is still needed in this area.
323 </p><p>
328 After <a href="InterdomainTrusts.html#samba-trusted-domain" title="Samba as the Trusted Domain">creating the interdomain trust account on the Samba server</a>
329 as described previously, open <span class="application">Active Directory Domains and Trusts</span> on the AD
330 controller of the domain whose resources you wish Samba users to have access to. Remember that since NT4-style
331 trusts are not transitive, if you want your users to have access to multiple mixed-mode domains in your AD
332 forest, you will need to repeat this process for each of those domains. With <span class="application">Active Directory
333 domains and trusts</span> open, right-click on the name of the Active Directory domain that will trust
335 <span class="guilabel">Trusts</span> tab. In the upper part of the panel, you will see a list box labeled
336 <span class="guilabel">Domains trusted by this domain:</span> and an <span class="guilabel">Add...</span> button next to it.
337 Press this button and, just as with NT4, you will be prompted for the trusted domain name and the relationship
338 password. Press <span class="emphasis"><em>OK</em></span> and after a moment, Active Directory will respond with
339 <code class="computeroutput">The trusted domain has been added and the trust has been verified.</code> Your
340 Samba users can now be granted access to resources in the AD domain.
341 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2624750"></a>Common Errors</h2></div></div></div><p>
342 Interdomain trust relationships should not be attempted on networks that are unstable
343 or that suffer regular outages. Network stability and integrity are key concerns with
344 distributed trusted domains.
345 </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2624763"></a>Browsing of Trusted Domain Fails</h3></div></div></div><p>
346 <span class="emphasis"><em>Browsing from a machine in a trusted Windows 200x domain to a Windows 200x member of
347 a trusting Samba domain, I get the following error:</em></span>
349 The system detected a possible attempt to compromise security. Please
350 ensure that you can contact the server that authenticated you.
351 </pre><p>
352 </p><p>
353 <span class="emphasis"><em>The event logs on the box I'm trying to connect to have entries regarding group
354 policy not being applied because it is a member of a down-level domain.</em></span>
355 </p><p>If there is a computer account in the Windows
356 200x domain for the machine in question, and it is disabled, this problem can
357 occur. If there is no computer account (removed or never existed), or if that
358 account is still intact (i.e., you just joined it to another domain), everything
359 seems to be fine. By default, when you unjoin a domain (the Windows 200x
360 domain), the computer tries to automatically disable the computer account in
361 the domain. If you are running as an account that has privileges to do this
362 when you unjoin the machine, it is done; otherwise it is not done.
363 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2624809"></a>Problems with LDAP ldapsam and Older Versions of smbldap-tools</h3></div></div></div><p>
364 If you use the <span><strong class="command">smbldap-useradd</strong></span> script to create a trust
365 account to set up interdomain trusts, the process of setting up the trust will
366 fail. The account that was created in the LDAP database will have an account
369 </p><p>Here is a simple solution.
370 Create a machine account as follows:
373 </pre><p>
374 Then set the desired trust account password as shown here:
377 </pre><p>
378 Using a text editor, create the following file:
380 dn: uid=domain_name$,ou=People,dc={your-domain},dc={your-top-level-domain}
381 changetype: modify
382 sambaAcctFlags: [I ]
383 </pre><p>
384 Then apply the text file to the LDAP database as follows:
387 -D "cn=Manager,dc={your-domain},dc={your-top-level-domain}" \
388 -W -f /path-to/foobar
389 </pre><p>
390 Create a single-sided trust under the NT4 Domain User Manager, then execute:
393 </pre><p>
394 </p><p>
395 It works with Samba-3 and NT4 domains, and also with Samba-3 and Windows 200x ADS in mixed mode.
396 Both domain controllers, Samba and NT must have the same WINS server; otherwise,
397 the trust will never work.
398 </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 18. 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 20. Hosting a Microsoft Distributed File System Tree</td></tr></table></div></body></html>