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+<?xml version="1.0" encoding="iso-8859-1"?>
+<!DOCTYPE chapter PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
+<chapter id="InterdomainTrusts">
+<chapterinfo>
+ &author.jht;
+ &author.mimir;
+ <author>&person.jelmer;<contrib>drawing</contrib></author>
+ <author>
+ <firstname>Stephen</firstname><surname>Langasek</surname>
+ <affiliation>
+ <address><email>vorlon@netexpress.net</email></address>
+ </affiliation>
+ </author>
+ <pubdate>April 3, 2003</pubdate>
+</chapterinfo>
+
+<title>Interdomain Trust Relationships</title>
+
+
+<para>
+<indexterm><primary>Interdomain Trusts</primary></indexterm>
+<indexterm><primary>LDAP</primary></indexterm>
+<indexterm><primary>trusts</primary></indexterm>
+<indexterm><primary>samba-to-samba trusts</primary></indexterm>
+<indexterm><primary>Active Directory</primary></indexterm>
+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.
+</para>
+
+<para>
+<indexterm><primary>winbind</primary></indexterm>
+<indexterm><primary>UID range</primary></indexterm>
+<indexterm><primary>GID range</primary></indexterm>
+The use of interdomain trusts requires use of <command>winbind</command>. Thus the
+<command>winbindd</command> daemon must be running. Winbind operation in this mode is
+dependant on the specification of a valid UID range and a valid GID range in the &smb.conf; file.
+These are specified respectively using
+<smbconfoption name="idmap uid">10000-20000</smbconfoption> and
+<smbconfoption name="idmap gid">10000-20000</smbconfoption>.
+</para>
+
+<note><para>
+The use of winbind is necessary only when Samba is the trusting Domain, not when it is the
+trusted Domain.
+</para></note>
+
+<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 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 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.
+</para>
+
+</sect1>
+
+<sect1>
+<title>Trust Relationship Background</title>
+
+<para>
+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.
+</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 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.
+</para>
+
+<para>
+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
+<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 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 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.
+</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. 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.
+<indexterm><primary>Interdomain Trusts</primary><secondary>creating</secondary></indexterm>
+</para>
+
+
+<sect2>
+<title>Creating an NT4 Domain Trust</title>
+
+<para>
+For MS Windows NT4, all domain trust relationships are configured using the
+<application>Domain User Manager</application>. 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>. Next to the lower box labeled
+<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
+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).
+</para>
+
+</sect2>
+
+
+<sect2>
+<title>Completing an NT4 Domain Trust</title>
+
+<para>
+<indexterm><primary>Interdomain Trusts</primary><secondary>Completing</secondary></indexterm>
+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 <guilabel>Policies</guilabel>, then select
+<guilabel>Trust Relationships</guilabel>, click on the <guibutton>Add</guibutton> button
+next to the box that is labeled <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>
+
+<sect2>
+<title>Inter-Domain Trust Facilities</title>
+
+
+<para>
+<indexterm><primary>Interdomain Trusts</primary><secondary>Facilities</secondary></indexterm>
+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:
+</para>
+
+<image id="trusts1">
+ <imagedescription>Trusts overview.</imagedescription>
+ <imagefile>trusts1</imagefile>
+</image>
+
+<itemizedlist>
+ <listitem><para>
+ DomA (completes the trust connection) <parameter>Trusts</parameter> DomB.
+ </para></listitem>
+
+ <listitem><para>
+ DomA is the <parameter>Trusting</parameter> domain.
+ </para></listitem>
+
+ <listitem><para>
+ DomB is the <parameter>Trusted</parameter> domain (originates the trust account).
+ </para></listitem>
+
+ <listitem><para>
+ Users in DomB can access resources in DomA.
+ </para></listitem>
+
+ <listitem><para>
+ Users in DomA cannot access resources in DomB.
+ </para></listitem>
+
+ <listitem><para>
+ Global groups from DomB can be used in DomA.
+ </para></listitem>
+
+ <listitem><para>
+ Global groups from DomA cannot be used in DomB.
+ </para></listitem>
+
+ <listitem><para>
+ DomB does appear in the logon dialog box on client workstations in DomA.
+ </para></listitem>
+
+ <listitem><para>
+ DomA does not appear in the logon dialog box on client workstations in DomB.
+ </para></listitem>
+</itemizedlist>
+
+<itemizedlist>
+ <listitem><para>
+ Users/Groups in a trusting domain cannot be granted rights, permissions or access
+ to a trusted domain.
+ </para></listitem>
+
+ <listitem><para>
+ The trusting domain can access and use accounts (Users/Global Groups) in the
+ trusted domain.
+ </para></listitem>
+
+ <listitem><para>
+ Administrators of the trusted domain can be granted administrative rights in the
+ trusting domain.
+ </para></listitem>
+
+ <listitem><para>
+ Users in a trusted domain can be given rights and privileges in the trusting
+ domain.
+ </para></listitem>
+
+ <listitem><para>
+ Trusted domain Global Groups can be given rights and permissions in the trusting
+ domain.
+ </para></listitem>
+
+ <listitem><para>
+ Global Groups from the trusted domain can be made members in Local Groups on
+ MS Windows Domain Member machines.
+ </para></listitem>
+</itemizedlist>
+
+</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 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.
+</para>
+
+<para>
+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.
+</para>
+
+<sect2 id="samba-trusted-domain">
+<title>Samba as the Trusted Domain</title>
+
+<para>
+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 <command>smbpasswd</command> 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:
+</para>
+
+<para>
+<screen>
+&rootprompt; <userinput>smbpasswd -a -i rumba</userinput>
+New SMB password: <userinput>XXXXXXXX</userinput>
+Retype SMB password: <userinput>XXXXXXXX</userinput>
+Added user rumba$
+</screen>
+
+where <option>-a</option> means to add a new account into the
+passdb database and <option>-i</option> means: <quote>create this
+account with the Inter-Domain trust flag</quote>.
+</para>
+
+<para>
+The account name will be <quote>rumba$</quote> (the name of the remote domain).
+If this fails, you should check that the trust account has been added to the system
+password database (<filename>/etc/passwd</filename>). If it has not been added, you
+can add it manually and then repeat the step above.
+</para>
+
+<para>
+After issuing this command, you will be asked to enter the password for
+the account. You can use any password you want, but be aware that Windows NT will
+not change this password until seven days following account creation.
+After the command returns successfully, you can look at the entry for the new account
+(in the standard way as appropriate for your configuration) and see that accounts name is
+really RUMBA$ and it has the <quote>I</quote> flag set in the flags field. Now you are ready to confirm
+the trust by establishing it from Windows NT Server.
+</para>
+
+
+<para>
+<indexterm><primary>User Manager</primary></indexterm>
+Open <application>User Manager for Domains</application> and from the
+<guimenu>Policies</guimenu> menu, select <guimenuitem>Trust Relationships...</guimenuitem>.
+Beside the <guilabel>Trusted domains</guilabel> list box click the
+<guimenu>Add...</guimenu> 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 <guibutton>OK</guibutton> and, if everything went without incident, you will see
+the <computeroutput>Trusted domain relationship successfully
+established</computeroutput> message.
+</para>
+
+</sect2>
+<sect2>
+<title>Samba as the Trusting 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 the NT-controlled domain is called RUMBA.
+</para>
+
+<para>
+The very first step is to add an account for the SAMBA domain on RUMBA's PDC.
+</para>
+
+
+<para>
+<indexterm><primary>User Manager</primary></indexterm>
+Launch the <application>Domain User Manager</application>, then from the menu select
+<guimenu>Policies</guimenu>, <guimenuitem>Trust Relationships</guimenuitem>.
+Now, next to the <guilabel>Trusted Domains</guilabel> box press the <guibutton>Add</guibutton>
+button and type in the name of the trusted domain (SAMBA) and the password to use in 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 its Samba's turn.
+</para>
+
+<para>
+Using your favorite 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.
+An error message <errorname>`NT_STATUS_NOLOGON_INTERDOMAIN_TRUST_ACCOUNT'</errorname>
+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 <computeroutput>Success</computeroutput> message. Congratulations! Your trust
+relationship has just been established.
+</para>
+
+<note><para>
+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>NT4-Style Domain Trusts with Windows 2000</title>
+<para>
+Although <application>Domain User Manager</application> 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.
+</para>
+
+<para>
+After <link linkend="samba-trusted-domain">creating the interdomain trust account on the
+Samba server</link> as described above, open <application>Active Directory Domains and
+Trusts</application> 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 <application>Active Directory Domains
+and Trusts</application> open, right-click on the name of the Active Directory domain that
+will trust our Samba domain and choose <guimenuitem>Properties</guimenuitem>, then click on
+the <guilabel>Trusts</guilabel> tab. In the upper part of the panel, you will see a list box
+labeled <guilabel>Domains trusted by this domain:</guilabel>, and an
+<guilabel>Add...</guilabel> 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 <computeroutput>The trusted domain has
+been added and the trust has been verified.</computeroutput> Your Samba users can now be
+granted access to resources in the AD domain.
+</para>
+</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>Browsing of Trusted Domain Fails</title>
+
+<para>
+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:
+</para>
+
+<screen>
+The system detected a possible attempt to compromise security. Please ensure that
+you can contact the server that authenticated you.
+</screen>
+
+<para>
+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.
+</para>
+
+<para><emphasis>Answer: </emphasis> 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.
+</para>
+
+</sect2>
+
+<sect2>
+<title>Problems With LDAP ldapsam And The smbldap-tools</title>
+
+<para>
+If you use the <command>smbldap-useradd</command> 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 <constant>[W ]</constant>, when it must have
+<constant>[I ]</constant> for Interdomain trusts to work.
+</para>
+
+<para><emphasis>Answer: </emphasis>Here is a simple solution.
+Create a machine account as follows:
+<screen>
+&rootprompt; smbldap-useradd -w domain_name
+</screen>
+Then set the desired trust account password as shown here:
+<screen>
+&rootprompt; smbldap-passwd domain_name\$
+</screen>
+Using a text editor, create the following file:
+<screen>
+dn: uid=domain_name$,ou=People,dc={your-domain},dc={your-top-level-domain}
+changetype: modify
+sambaAcctFlags: [I ]
+</screen>
+Then apply the text file to the LDAP database as follows:
+<screen>
+&rootprompt; ldapmodify -x -h localhost \
+ -D "cn=Manager,dc={your-domain},dc={your-top-level-domain}" \
+ -W -f /path-to/foobar
+</screen>
+Create a single-sided trust under the NT4 Domain User Manager, then execute:
+<screen>
+&rootprompt; net rpc trustdom establish domain_name
+</screen>
+</para>
+
+<para>
+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.
+</para>
+
+</sect2>
+
+</sect1>
+
+</chapter>