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authorGerald Carter <jerry@samba.org>2002-01-05 06:11:29 +0000
committerGerald Carter <jerry@samba.org>2002-01-05 06:11:29 +0000
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yeah! I think I figured it out now
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+<chapter id="samba-ldap-howto">
+
+
+<chapterinfo>
+ <author>
+ <firstname>Gerald (Jerry)></firstname><surname>Carter></surname>
+ <affiliation>
+ <orgname>Samba Team</orgname>
+ <address><email>jerry@samba.org</email></address>
+ </affiliation>
+ </author>
+
+
+ <pubdate> (29 Dec 2001) </pubdate>
+</chapterinfo>
+
+<title>Storing Samba's User/Machine Account information in an LDAP Directory</title>
+
+<sect1>
+<title>Purpose</title>
+
+<para>
+This document describes how to use an LDAP directory for storing Samba user
+account information normally stored in the smbpasswd(5) file. It is
+assumed that the reader already has a basic understanding of LDAP concepts
+and has a working directory server already installed. For more information
+on LDAP architectures and Directories, please refer to the following sites.
+</para>
+
+<itemizedlist>
+ <listitem><para>OpenLDAP - <ulink url="http://www.openldap.org/">http://www.openldap.org/</ulink></para></listitem>
+ <listitem><para>iPlanet Directory Server - <ulink url="http://iplanet.netscape.com/directory">http://iplanet.netscape.com/directory</ulink></para></listitem>
+</itemizedlist>
+
+<para>
+Note that <ulink url="http://www.ora.com/">O'Reilly Publishing</ulink> is working on
+a guide to LDAP for System Administrators which has a planned release date of
+early summer, 2002.
+</para>
+
+<para>It may also be helpful to suppplement the reading of the HOWTO with
+the <ulink url="http://www.unav.es/cti/ldap-smb/ldap-smb-2_2-howto.html">Samba-PDC-LDAP-HOWTO</ulink>
+maintained by Ignacio Coupeau.
+</para>
+
+</sect1>
+
+
+<sect1>
+<title>Introduction</title>
+
+<para>
+Traditionally, when configuring <ulink url="smb.conf.5.html#ENCRYPTPASSWORDS">"encrypt
+passwords = yes"</ulink> in Samba's <filename>smb.conf</filename> file, user account
+information such as username, LM/NT password hashes, password change times, and account
+flags have been stored in the <filename>smbpasswd(5)</filename> file. There are several
+disadvantages to this approach for sites with very large numbers of users (counted
+in the thousands).
+</para>
+
+<para>
+The first is that all lookups must be performed sequentially. Given that
+there are approximately two lookups per domain logon (one for a normal
+session connection such as when mapping a network drive or printer), this
+is non-optimal. What is needed is an indexed approach such as is used in
+databases.
+</para>
+
+<para>
+The second problem is that administrators which desired to replicate an
+smbpasswd file to more than one Samba server were left to use external
+tools such as <command>rsync(1)</command> and <command>ssh(1)</command>
+and write custom, in-house scripts.
+</para>
+
+<para>
+And finally, the amount of information which is stored in an
+smbpasswd entry leaves no room for additional attributes such as
+a home directory, password expiration time, or even a Relative
+Identified (RID).
+</para>
+
+<para>
+As a result of these defeciencies, a more robust means of storing user attributes
+used by smbd was developed. The API which defines access to user accounts
+is referred to as the samdb interface (previously this was called the passdb
+API, and is still so named in the CVS trees). In Samba 2.2.3, enabling support
+for a samdb backend (e.g. <parameter>--with-ldapsam</parameter> or
+<parameter>--with-tdbsam</parameter>) requires compile time support.
+</para>
+
+<para>
+When compiling Samba to include the <parameter>--with-ldapsam</parameter> autoconf
+option, smbd (and associated tools) will store and lookup user accounts in
+an LDAP directory. In reality, this is very easy to understand. If you are
+comfortable with using an smbpasswd file, simply replace "smbpasswd" with
+"LDAP directory" in all the documentation.
+</para>
+
+<para>
+There are a few points to stress about what the <parameter>--with-ldapsam</parameter>
+does not provide. The LDAP support referred to in the this documentat does not
+include:
+</para>
+
+<itemizedlist>
+ <listitem><para>A means of retrieving user account information from
+ an Windows 2000 Active Directory server.</para></listitem>
+ <listitem><para>A means of replacing /etc/passwd.</para></listitem>
+</itemizedlist>
+
+<para>
+The second item can be accomplished by using LDAP NSS and PAM modules. LGPL
+versions of these libraries can be obtained from PADL Software
+(<ulink url="http://www.padl.com/">http://www.padl.com/</ulink>). However,
+the details of configuring these packages i beyond the scope of this document.
+</para>
+
+</sect1>
+
+<sect1>
+<title>Supported LDAP Servers</title>
+
+<para>
+The LDAP samdb code in 2.2.3 has been developed and tested using the OpenLDAP
+2.0 server and client libraries. The same code should be able to work with
+Netscape's Directory Server and client SDK. However, due to lack of testing
+so far, there are bounds to be compile errors and bugs. These should not be
+hard to fix. If you are so inclined, please be sure to forward all pacthes to
+<ulink url="samba-patches@samba.org">samba-patches@samba.org</ulink> and
+<ulink url="jerry@samba.org">jerry@samba.org</ulink>.
+</para>
+
+</sect1>
+
+
+
+
+<sect1>
+<title>Schema and Relationship to the RFC 2307 posixAccount</title>
+
+
+<para>
+Samba 2.2.3 includes the necessary schema file for OpenLDAP 2.0 in
+<filename>examples/LDAP/samba.schema</filename>. (Note that this schema
+file has been modified since the experimental support initially included
+in 2.2.2). The sambaAccount objectclass is given here:
+</para>
+
+<para><programlisting>
+objectclass ( 1.3.1.5.1.4.1.7165.2.2.2 NAME 'sambaAccount' SUP top STRUCTURAL
+ DESC 'Samba Account'
+ MUST ( uid $ rid )
+ MAY ( cn $ lmPassword $ ntPassword $ pwdLastSet $ logonTime $
+ logoffTime $ kickoffTime $ pwdCanChange $ pwdMustChange $ acctFlags $
+ displayName $ smbHome $ homeDrive $ scriptPath $ profilePath $
+ description $ userWorkstations $ primaryGroupID ))
+</programlisting></para>
+
+<para>
+The samba.schema file has been formatted for OpenLDAP 2.0. The OID's are
+owned by the Samba Team and as such as legal to be openly published.
+If you translate the schema to be used with Netscape DS, please
+submit the modified schema file as a patch to <ulink
+url="jerry@samba.org">jerry@samba.org</ulink>
+</para>
+
+<para>
+Just as the smbpasswd file is mean to store information which supplements a
+user's <filename>/etc/passwd</filename> entry, so is the sambaAccount object
+meant to supplement the UNIX user account information. A sambaAccount is a
+<constant>STRUCTURAL</constant> objectclass so it can be stored individually
+in the directory. However, there are several fields (e.g. uid) which overlap
+with the posixAccount objectclass outlined in RFC2307. This is by design.
+</para>
+
+<para>
+In order to store all user account information (UNIX and Samba) in the directory,
+it is necessary to use the sambaAccount and posixAccount objectclasses in
+combination. However, smbd will still obtain the user's UNIX account
+information via the standard C library calls (e.g. getpwnam(), et. al.).
+This means that the Samba server must also have the LDAP NSS library installed
+and functioning correctly. This division of information mkes it posible to
+store all Samba account information in LDAP, but still maintain UNIX account
+information in NIS while the network is transitioning to a full LDAP infratrsucture.
+</para>
+
+<para>
+To include support for the sambaAccount object in an OpenLDAP directory
+server, first copy the samba.schema file to slapd's configuration directory.
+</para>
+
+<para>
+<prompt>root# </prompt><command>cp samba.schema /etc/openldap/schema/</command>
+</para>
+
+<para>
+Next, include the <filename>samba.schema</filename> file in <filename>slapd.conf</filename>.
+The sambaAccount object contains two attributes which depend upon other schema
+files. The 'uid' attribute is defined in <filename>cosine.schema</filename> and
+the 'displayName' attribute is defined in the <filename>inetorgperson.schema</filename>
+file. Bother of these must be included before the <filename>samba.schema</filename> file.
+</para>
+
+<para><programlisting>
+## /etc/openldap/slapd.conf
+
+## schema files (core.schema is required by default)
+include /etc/openldap/schema/core.schema
+
+## needed for sambaAccount
+include /etc/openldap/schema/cosine.schema
+include /etc/openldap/schema/inetorgperson.schema
+include /etc/openldap/schema/samba.schema
+
+## uncomment this line if you want to support the RFC2307 (NIS) schema
+## include /etc/openldap/schema/nis.schema
+
+....
+</programlisting></para>
+
+
+</sect1>
+
+
+
+<sect1>
+<title>smb.conf LDAP parameters</title>
+
+
+<para>
+The following parameters are available in smb.conf only with <parameter>--with-ldapsam</parameter>
+was included with compiling Samba.
+</para>
+
+<itemizedlist>
+ <listitem><para><ulink url="smb.conf.5.html#LDAPSSL">ldap ssl</ulink></para></listitem>
+ <listitem><para><ulink url="smb.conf.5.html#LDAPSERVER">ldap server</ulink></para></listitem>
+ <listitem><para><ulink url="smb.conf.5.html#LDAPADMINDN">ldap admin dn</ulink></para></listitem>
+ <listitem><para><ulink url="smb.conf.5.html#LDAPSUFFIX">ldap suffix</ulink></para></listitem>
+ <listitem><para><ulink url="smb.conf.5.html#LDAPFILTER">ldap filter</ulink></para></listitem>
+ <listitem><para><ulink url="smb.conf.5.html#LDAPPORT">ldap port</ulink></para></listitem>
+</itemizedlist>
+
+<para>
+These are described in the <ulink url="smb.conf.5.html">smb.conf(5)</ulink> man
+page and so will not be repeated here. However, a sample smb.conf file for
+use with an LDAP directory could appear as
+</para>
+
+<para><programlisting>
+## /usr/local/samba/lib/smb.conf
+[global]
+ security = user
+ encrypt passwords = yes
+
+ netbios name = TASHTEGO
+ workgroup = NARNIA
+
+ # ldap related parameters
+
+ # define the DN to use when binding to the directory servers
+ # The password for this DN is not stored in smb.conf. Rather it
+ # must be set by using 'smbpasswd -w <replaceable>secretpw</replaceable>' to store the
+ # passphrase in the secrets.tdb file. If the "ldap admin dn" values
+ # changes, this password will need to be reset.
+ ldap admin dn = "cn=Manager,dc=samba,dc=org"
+
+ # specify the LDAP server's hostname (defaults to locahost)
+ ldap server = ahab.samba.org
+
+ # Define the SSL option when connecting to the directory
+ # ('off', 'start tls', or 'on' (default))
+ ldap ssl = start tls
+
+ # define the port to use in the LDAP session (defaults to 636 when
+ # "ldap ssl = on")
+ ldap port = 389
+
+ # specify the base DN to use when searching the directory
+ ldap suffix = "ou=people,dc=samba,dc=org"
+
+ # generally the default ldap search filter is ok
+ # ldap filter = "(&(uid=%u)(objectclass=sambaAccount))"
+</programlisting></para>
+
+
+
+</sect1>
+
+
+
+
+<sect1>
+<title>Security and sambaAccount</title>
+
+
+<para>
+There are two important points to remember when discussing the security
+of sambaAccount entries in the directory.
+</para>
+
+<itemizedlist>
+ <listitem><para><emphasis>Never</emphasis> retrieve the lmPassword or
+ ntPassword attribute values over and unencrypted LDAP session.</para></listitem>
+ <listitem><para><emphasis>Never</emphasis> allow non-admin users to
+ view the lmPassword or ntPassword attribute values.</para></listitem>
+</itemizedlist>
+
+<para>
+These password hashes are clear text equivalents and can be used to impersonate
+the user without deriving the original clear text strings.
+</para>
+
+<para>
+To remedy the first security issue, the "ldap ssl" smb.conf parameter defaults
+to require an encrypted session (<command>ldap ssl = on</command>) using
+the default port of 636
+when contacting the directory server. When using an OpenLDAP 2.0 server, it
+is possible to use the use the StartTLS LDAP extended operation in the place of
+LDAPS. In either case, you are strongly discouraged to disable this security
+(<command>ldap ssl = off</command>).
+</para>
+
+<para>
+The second security precaution is to prevent non-administrative users from
+harvesting password hashes from the directory. This can be done using the
+following ACL in <filename>slapd.conf</filename>:
+</para>
+
+<para><programlisting>
+## allow users to update their own password, but not to browse others
+access to attrs=userPassword,lmPassword,ntPassword
+ by self write
+ by * auth
+</programlisting></para>
+
+<para>
+You may of course, add in write access to administrative DN's as necessary.
+</para>
+
+</sect1>
+
+
+
+<sect1>
+<title></title>
+
+
+<para>
+There are currently four sambaAccount attributes which map directly onto
+<filename>smb.conf</filename> parameters.
+</para>
+
+<itemizedlist>
+ <listitem><para>smbHome -&gt; "logon home"</para></listitem>
+ <listitem><para>profilePath -&gt; "logon path"</para></listitem>
+ <listitem><para>homeDrive -&gt; "logon drive"</para></listitem>
+ <listitem><para>scriptPath -&gt; "logon script"</para></listitem>
+</itemizedlist>
+
+<para>
+First of all, these parameters are only used when Samba is acting as a
+PDC or a domain (refer to the <ulink url="Samba-PDC-HOWTO.html">Samba-PDC-HOWTO</ulink>
+for details on how to configure Samba as a Primary Domain Controller).
+Furthermore, these attributes are only stored with the sambaAccount entry if
+the values are non-default values. For example, assume TASHTEGO has now been
+configured as a PDC and that <command>logon home = \\%L\%u</command> was defined in
+its <filename>smb.conf</filename> file. Assuming <filename>smb.conf</filename>
+also contains , when a user named "becky" logons to the domain, the <parameter>logon
+home</parameter> string is expanded to \\TASHTEGO\becky.
+</para>
+
+<para>
+If the smbHome attribute exists in the entry "uid=becky,ou=people,dc=samba,dc=org",
+this value is used. However, if this attribute does not exist, then the value
+of the <parameter>logon home</parameter> parameter is used in its place. Samba
+will only write the attribute value to the directory entry is the value is
+something other than the default (e.g. \\MOBY\becky).
+</para>
+
+
+</sect1>
+
+
+
+
+<sect1>
+<title>Example LDIF Entries for a sambaAccount</title>
+
+
+<para>
+The following is a working LDIF with the inclusion of the posixAccount objectclass:
+</para>
+
+<para><programlisting>
+dn: uid=guest2, ou=people,dc=plainjoe,dc=org
+ntPassword: 878D8014606CDA29677A44EFA1353FC7
+pwdMustChange: 2147483647
+primaryGroupID: 1201
+lmPassword: 552902031BEDE9EFAAD3B435B51404EE
+pwdLastSet: 1010179124
+logonTime: 0
+objectClass: sambaAccount
+uid: guest2
+kickoffTime: 2147483647
+acctFlags: [UX ]
+logoffTime: 2147483647
+rid: 19006
+pwdCanChange: 0
+</programlisting></para>
+
+<para>
+The following is an LDIF entry for using both the sambaAccount and
+posixAccount objectclasses:
+</para>
+
+<para><programlisting>
+dn: uid=gcarter, ou=people,dc=plainjoe,dc=org
+logonTime: 0
+displayName: Gerald Carter
+lmPassword: 552902031BEDE9EFAAD3B435B51404EE
+primaryGroupID: 1201
+objectClass: posixAccount
+objectClass: sambaAccount
+acctFlags: [UX ]
+userPassword: {crypt}BpM2ej8Rkzogo
+uid: gcarter
+uidNumber: 9000
+cn: Gerald Carter
+loginShell: /bin/bash
+logoffTime: 2147483647
+gidNumber: 100
+kickoffTime: 2147483647
+pwdLastSet: 1010179230
+rid: 19000
+homeDirectory: /home/tashtego/gcarter
+pwdCanChange: 0
+pwdMustChange: 2147483647
+ntPassword: 878D8014606CDA29677A44EFA1353FC7
+</programlisting></para>
+
+
+</sect1>
+
+
+
+<sect1>
+<title>Comments</title>
+
+
+<para>
+Please mail all comments regarding this HOWTO to <ulink
+url="mailto:jerry@samba.org">jerry@samba.org</ulink>. This documents was
+last updated to reflect the Samba 2.2.3 release.
+
+</para>
+
+
+</sect1>
+
+
+</chapter>