Chapter 11. Account Information Databases

Chapter 11. Account Information Databases
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Jelmer R. Vernooij

The Samba Team

<jelmer@samba.org>

Gerald (Jerry) Carter

Samba Team

<jerry@samba.org>

Jeremy Allison

Samba Team

<jra@samba.org>

John H. Terpstra

Samba Team

<jht@samba.org>

Olivier (lem) Lemaire

IDEALX

<olem@IDEALX.org>

May 24, 2003

+Samba 3 implements a new capability to work concurrently with multiple account backends. +The possible new combinations of password backends allows Samba 3 a degree of flexibility +and scalability that previously could be achieved only with MS Windows Active Directory. +This chapter describes the new functionality and how to get the most out of it. +

+In the course of development of Samba-3, a number of requests were received to provide the +ability to migrate MS Windows NT4 SAM accounts to Samba-3 without the need to provide +matching UNIX/Linux accounts. We called this the Non UNIX Accounts (NUA) +capability. The intent was that an administrator could decide to use the tdbsam +backend and by simply specifying passdb backend = tdbsam_nua +this would allow Samba-3 to implement a solution that did not use UNIX accounts per se. Late +in the development cycle, the team doing this work hit upon some obstacles that prevents this +solution from being used. Given the delays with Samba-3 release a decision was made to NOT +deliver this functionality until a better method of recognising NT Group SIDs from NT User +SIDs could be found. This feature may thus return during the life cycle for the Samba-3 series. +

Note

+Samba-3 does NOT support Non-UNIX Account (NUA) operation for user accounts. +Samba-3 does support NUA operation for machine accounts. +

Features and Benefits

+Samba-3 provides for complete backwards compatibility with Samba-2.2.x functionality +as follows: +

Backwards Compatibility Backends

Plain Text:

+ This option uses nothing but the UNIX/Linux /etc/passwd + style back end. On systems that have PAM (Pluggable Authentication Modules) + support all PAM modules are supported. The behaviour is just as it was with + Samba-2.2.x, and the protocol limitations imposed by MS Windows clients + apply likewise. +

smbpasswd:

+ This option allows continues use of the smbpasswd + file that maintains a plain ASCII (text) layout that includes the MS Windows + LanMan and NT encrypted passwords as well as a field that stores some + account information. This form of password backend does NOT store any of + the MS Windows NT/200x SAM (Security Account Manager) information needed to + provide the extended controls that are needed for more comprehensive + interoperation with MS Windows NT4 / 200x servers. +

+ This backend should be used only for backwards compatibility with older + versions of Samba. It may be deprecated in future releases. +

ldapsam_compat (Samba-2.2 LDAP Compatibility):

+ There is a password backend option that allows continued operation with + a existing OpenLDAP backend that uses the Samba-2.2.x LDAP schema extension. + This option is provided primarily as a migration tool, although there is + no reason to force migration at this time. Note that this tool will eventually + be deprecated. +

New Backends

+Samba-3 introduces the following new password backend capabilities: +

tdbsam:

+ This backend provides a rich database backend for local servers. This + backend is NOT suitable for multiple domain controller (ie: PDC + one + or more BDC) installations. +

+ The tdbsam password backend stores the old + smbpasswd information PLUS the extended MS Windows NT / 200x + SAM information into a binary format TDB (trivial database) file. + The inclusion of the extended information makes it possible for Samba-3 + to implement the same account and system access controls that are possible + with MS Windows NT4 and MS Windows 200x based systems. +

+ The inclusion of the tdbsam capability is a direct + response to user requests to allow simple site operation without the overhead + of the complexities of running OpenLDAP. It is recommended to use this only + for sites that have fewer than 250 users. For larger sites or implementations + the use of OpenLDAP or of Active Directory integration is strongly recommended. +

ldapsam:

+ This provides a rich directory backend for distributed account installation. +

+ Samba-3 has a new and extended LDAP implementation that requires configuration + of OpenLDAP with a new format samba schema. The new format schema file is + included in the examples/LDAP directory of the Samba distribution. +

+ The new LDAP implementation significantly expands the control abilities that + were possible with prior versions of Samba. It is now possible to specify + "per user" profile settings, home directories, account access controls, and + much more. Corporate sites will see that the Samba-Team has listened to their + requests both for capability and to allow greater scalability. +

mysqlsam (MySQL based backend):

+ It is expected that the MySQL based SAM will be very popular in some corners. + This database backend will be on considerable interest to sites that want to + leverage existing MySQL technology. +

xmlsam (XML based datafile):

+ Allows the account and password data to be stored in an XML format + data file. This backend can not be used for normal operation, it can only + be used in conjunction with pdbedit's pdb2pdb + functionality. The DTD that is used might be subject to changes in the future. +

+ The xmlsam option can be useful for account migration between database + backends or backups. Use of this tool will allow the data to be edited before migration + into another backend format. +

Technical Information

+ Old windows clients send plain text passwords over the wire. Samba can check these + passwords by crypting them and comparing them to the hash stored in the unix user database. +

+ Newer windows clients send encrypted passwords (so-called Lanman and NT hashes) over + the wire, instead of plain text passwords. The newest clients will send only encrypted + passwords and refuse to send plain text passwords, unless their registry is tweaked. +

+ These passwords can't be converted to unix style encrypted passwords. Because of that, + you can't use the standard unix user database, and you have to store the Lanman and NT + hashes somewhere else. +

+ In addition to differently encrypted passwords, windows also stores certain data for each + user that is not stored in a unix user database. e.g: workstations the user may logon from, + the location where the users' profile is stored, and so on. Samba retrieves and stores this + information using a passdb backend. Commonly available backends are LDAP, plain text + file, MySQL and nisplus. For more information, see the man page for smb.conf regarding the + passdb backend parameter. +

Figure 11.1. IDMAP

Important Notes About Security

+ The unix and SMB password encryption techniques seem similar on the surface. This + similarity is, however, only skin deep. The unix scheme typically sends clear text + passwords over the network when logging in. This is bad. The SMB encryption scheme + never sends the cleartext password over the network but it does store the 16 byte + hashed values on disk. This is also bad. Why? Because the 16 byte hashed values + are a "password equivalent". You cannot derive the user's password from them, but + they could potentially be used in a modified client to gain access to a server. + This would require considerable technical knowledge on behalf of the attacker but + is perfectly possible. You should thus treat the data stored in whatever passdb + backend you use (smbpasswd file, ldap, mysql) as though it contained the cleartext + passwords of all your users. Its contents must be kept secret, and the file should + be protected accordingly. +

+ Ideally we would like a password scheme that involves neither plain text passwords + on the net nor on disk. Unfortunately this is not available as Samba is stuck with + having to be compatible with other SMB systems (WinNT, WfWg, Win95 etc). +

+ Windows NT 4.0 Service pack 3 changed the default setting so that plaintext passwords + are disabled from being sent over the wire. This mandates either the use of encrypted + password support or edit the Windows NT registry to re-enable plaintext passwords. +

+ The following versions of MS Windows do not support full domain security protocols, + although they may log onto a domain environment: +

MS DOS Network client 3.0 with the basic network redirector installed
Windows 95 with the network redirector update installed
Windows 98 [se]
Windows Me

Note

+ MS Windows XP Home does not have facilities to become a domain member and it can + not participate in domain logons. +

+ The following versions of MS Windows fully support domain security protocols. +

Windows NT 3.5x
Windows NT 4.0
Windows 2000 Professional
Windows 200x Server/Advanced Server
Windows XP Professional

+ All current release of Microsoft SMB/CIFS clients support authentication via the + SMB Challenge/Response mechanism described here. Enabling clear text authentication + does not disable the ability of the client to participate in encrypted authentication. + Instead, it allows the client to negotiate either plain text _or_ encrypted password + handling. +

+ MS Windows clients will cache the encrypted password alone. Where plain text passwords + are re-enabled, through the appropriate registry change, the plain text password is NEVER + cached. This means that in the event that a network connections should become disconnected + (broken) only the cached (encrypted) password will be sent to the resource server to + affect a auto-reconnect. If the resource server does not support encrypted passwords the + auto-reconnect will fail. USE OF ENCRYPTED PASSWORDS IS STRONGLY ADVISED. +

Advantages of Encrypted Passwords

Plain text passwords are not passed across + the network. Someone using a network sniffer cannot just + record passwords going to the SMB server.
Plain text passwords are not stored anywhere in + memory or on disk.
WinNT doesn't like talking to a server + that does not support encrypted passwords. It will refuse + to browse the server if the server is also in user level + security mode. It will insist on prompting the user for the + password on each connection, which is very annoying. The + only things you can do to stop this is to use SMB encryption. +
Encrypted password support allows automatic share + (resource) reconnects.
Encrypted passwords are essential for PDC/BDC + operation.

Advantages of non-encrypted passwords

Plain text passwords are not kept + on disk, and are NOT cached in memory.
Uses same password file as other unix + services such as login and ftp
Use of other services (such as telnet and ftp) which + send plain text passwords over the net, so sending them for SMB + isn't such a big deal.

Mapping User Identifiers between MS Windows and UNIX

+ Every operation in UNIX/Linux requires a user identifier (UID), just as in + MS Windows NT4 / 200x this requires a Security Identifier (SID). Samba provides + two means for mapping an MS Windows user to a UNIX/Linux UID. +

+ Firstly, all Samba SAM (Security Account Manager database) accounts require + a UNIX/Linux UID that the account will map to. As users are added to the account + information database, Samba will call the add user script + interface to add the account to the Samba host OS. In essence all accounts in + the local SAM require a local user account. +

+ The second way to affect Windows SID to UNIX UID mapping is via the + idmap uid, idmap gid parameters in smb.conf. + Please refer to the man page for information about these parameters. + These parameters are essential when mapping users from a remote SAM server. +

Mapping Common UIDs/GIDs on Distributed Machines

+ Samba-3 has a special facility that makes it possible to maintain identical UIDs and GIDs + on all servers in a distributed network. A distributed network is one where there exists + a PDC, one or more BDCs and/or one or more domain member servers. Why is this important? + This is important if files are being shared over more than one protocol (eg: NFS) and where + users are copying files across UNIX/Linux systems using tools such as rsync. +

+ The special facility is enabled using a parameter called idmap backend. + The default setting for this parameter is an empty string. Administrators should NOT set this + parameter except when an LDAP based passdb backend is in use. An example of use is: +

Example 11.1.

[global]

idmap backend = ldapsam://ldap-server.quenya.org:636

Account Management Tools

+Samba provides two (2) tools for management of User and machine accounts. These tools are +called smbpasswd and pdbedit. A third tool is under +development but is NOT expected to ship in time for Samba-3.0.0. The new tool will be a TCL/TK +GUI tool that looks much like the MS Windows NT4 Domain User Manager - hopefully this will +be announced in time for the Samba-3.0.1 release. +

The smbpasswd Command

+ The smbpasswd utility is a utility similar to the passwd + or yppasswd programs. It maintains the two 32 byte password + fields in the passdb backend. +

+ smbpasswd works in a client-server mode where it contacts the + local smbd to change the user's password on its behalf. This has enormous benefits + as follows: +

+ smbpasswd has the capability to change passwords on Windows NT + servers (this only works when the request is sent to the NT Primary Domain Controller + if changing an NT Domain user's password). +

+ smbpasswd can be used to: +

add user or machine accounts
delete user or machine accounts
enable user or machine accounts
disable user or machine accounts
set to NULL user passwords
manage interdomain trust accounts

+ To run smbpasswd as a normal user just type: +

+$ smbpasswd
+Old SMB password: secret
+

+ For secret type old value here - or hit return if + there was no old password +

+New SMB Password: new secret
+Repeat New SMB Password: new secret
+

+ If the old value does not match the current value stored for that user, or the two + new values do not match each other, then the password will not be changed. +

+ When invoked by an ordinary user it will only allow change of their own + SMB password. +

+ When run by root smbpasswd may take an optional argument, specifying + the user name whose SMB password you wish to change. When run as root, smbpasswd + does not prompt for or check the old password value, thus allowing root to set passwords + for users who have forgotten their passwords. +

+ smbpasswd is designed to work in the way familiar to UNIX + users who use the passwd or yppasswd commands. + While designed for administrative use, this tool provides essential user level + password change capabilities. +

+ For more details on using smbpasswd refer to the man page (the + definitive reference). +

The pdbedit Command

+ pdbedit is a tool that can be used only by root. It is used to + manage the passdb backend. pdbedit can be used to: +

add, remove or modify user accounts
listing user accounts
migrate user accounts

+ The pdbedit tool is the only one that can manage the account + security and policy settings. It is capable of all operations that smbpasswd can + do as well as a super set of them. +

+ One particularly important purpose of the pdbedit is to allow + the migration of account information from one passdb backend to another. See the + XML password backend section of this chapter. +

+ The following is an example of the user account information that is stored in + a tdbsam password backend. This listing was produced by running: +

+$ pdbedit -Lv met
+UNIX username:        met
+NT username:
+Account Flags:        [UX         ]
+User SID:             S-1-5-21-1449123459-1407424037-3116680435-2004
+Primary Group SID:    S-1-5-21-1449123459-1407424037-3116680435-1201
+Full Name:            Melissa E Terpstra
+Home Directory:       \\frodo\met\Win9Profile
+HomeDir Drive:        H:
+Logon Script:         scripts\logon.bat
+Profile Path:         \\frodo\Profiles\met
+Domain:               MIDEARTH
+Account desc:
+Workstations:         melbelle
+Munged dial:
+Logon time:           0
+Logoff time:          Mon, 18 Jan 2038 20:14:07 GMT
+Kickoff time:         Mon, 18 Jan 2038 20:14:07 GMT
+Password last set:    Sat, 14 Dec 2002 14:37:03 GMT
+Password can change:  Sat, 14 Dec 2002 14:37:03 GMT
+Password must change: Mon, 18 Jan 2038 20:14:07 GMT
+

+ The pdbedit tool allows migration of authentication (account) + databases from one backend to another. For example: To migrate accounts from an + old smbpasswd database to a tdbsam + backend: +

+ Set the passdb backend = tdbsam, smbpasswd. +
+ Execute: +
```
+root# pdbedit -i smbpassed -e tdbsam
+
```
+
+ Now remove the smbpasswd from the passdb backend + configuration in smb.conf. +

Password Backends

+Samba offers the greatest flexibility in backend account database design of any SMB/CIFS server +technology available today. The flexibility is immediately obvious as one begins to explore this +capability. +

+It is possible to specify not only multiple different password backends, but even multiple +backends of the same type. For example, to use two different tdbsam databases: +

passdb backend = tdbsam:/etc/samba/passdb.tdb, tdbsam:/etc/samba/old-passdb.tdb

Plain Text

+ Older versions of Samba retrieved user information from the unix user database + and eventually some other fields from the file /etc/samba/smbpasswd + or /etc/smbpasswd. When password encryption is disabled, no + SMB specific data is stored at all. Instead all operations are conducted via the way + that the Samba host OS will access its /etc/passwd database. + eg: On Linux systems that is done via PAM. +

smbpasswd - Encrypted Password Database

+ Traditionally, when configuring encrypt passwords = yes in Samba's smb.conf file, user account + information such as username, LM/NT password hashes, password change times, and account + flags have been stored in the smbpasswd(5) file. There are several + disadvantages to this approach for sites with very large numbers of users (counted + in the thousands). +

+ 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 a performance bottleneck for large sites. What is needed is an indexed approach + such as is used in databases. +
+ The second problem is that administrators who desire to replicate a smbpasswd file + to more than one Samba server were left to use external tools such as + rsync(1) and ssh(1) and wrote custom, + in-house scripts. +
+ 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 Identifier (RID). +

+ As a result of these deficiencies, a more robust means of storing user attributes + used by smbd was developed. The API which defines access to user accounts + is commonly referred to as the samdb interface (previously this was called the passdb + API, and is still so named in the Samba CVS trees). +

+ Samba provides an enhanced set of passdb backends that overcome the deficiencies + of the smbpasswd plain text database. These are tdbsam, ldapsam, and xmlsam. + Of these ldapsam will be of most interest to large corporate or enterprise sites. +

tdbsam

Samba can store user and machine account data in a "TDB" (Trivial Database). + Using this backend doesn't require any additional configuration. This backend is + recommended for new installations that do not require LDAP. +

+ As a general guide the Samba-Team does NOT recommend using the tdbsam backend for sites + that have 250 or more users. Additionally, tdbsam is not capable of scaling for use + in sites that require PDB/BDC implementations that requires replication of the account + database. Clearly, for reason of scalability, the use of ldapsam should be encouraged. +

ldapsam

+ There are a few points to stress that the ldapsam does not provide. The LDAP + support referred to in the this documentation does not include: +

A means of retrieving user account information from + an Windows 200x Active Directory server.
A means of replacing /etc/passwd.

+ The second item can be accomplished by using LDAP NSS and PAM modules. LGPL + versions of these libraries can be obtained from PADL Software + (http://www.padl.com/). More + information about the configuration of these packages may be found at "LDAP, + System Administration; Gerald Carter, O'Reilly; Chapter 6: Replacing NIS". + Refer to + http://safari.oreilly.com/?XmlId=1-56592-491-6 for those who might wish to know + more about configuration and administration of an OpenLDAP server. +

Note

+ This section is outdated for Samba-3 schema. Samba-3 introduces a new schema + that has not been documented at the time of this publication. +

+ This document describes how to use an LDAP directory for storing Samba user + account information traditionally 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. +

OpenLDAP - http://www.openldap.org/
iPlanet Directory Server - + http://iplanet.netscape.com/directory

+ Two additional Samba resources which may prove to be helpful are +

The Samba-PDC-LDAP-HOWTO + maintained by Ignacio Coupeau.
The NT migration scripts from IDEALX that are + geared to manage users and group in such a Samba-LDAP Domain Controller configuration. +

Supported LDAP Servers

+ The LDAP ldapsam code has been developed and tested using the OpenLDAP 2.0 and 2.1 server and + client libraries. The same code should work with Netscape's Directory Server and client SDK. + However, there are bound to be compile errors and bugs. These should not be hard to fix. + Please submit fixes via Bug reporting facility. +

Schema and Relationship to the RFC 2307 posixAccount

+ Samba 3.0 includes the necessary schema file for OpenLDAP 2.0 in + examples/LDAP/samba.schema. The sambaSamAccount objectclass is given here: +

+objectclass ( 1.3.6.1.4.1.7165.2.2.6 NAME 'sambaSamAccount' SUP top AUXILIARY
+    DESC 'Samba 3.0 Auxiliary SAM Account'
+    MUST ( uid $ sambaSID )
+    MAY  ( cn $ sambaLMPassword $ sambaNTPassword $ sambaPwdLastSet $
+          sambaLogonTime $ sambaLogoffTime $ sambaKickoffTime $
+          sambaPwdCanChange $ sambaPwdMustChange $ sambaAcctFlags $
+          displayName $ sambaHomePath $ sambaHomeDrive $ sambaLogonScript $
+          sambaProfilePath $ description $ sambaUserWorkstations $
+          sambaPrimaryGroupSID $ sambaDomainName ))
+

+ The samba.schema file has been formatted for OpenLDAP 2.0/2.1. + The OID's are owned by the Samba Team and as such is 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 + jerry@samba.org. +

+ Just as the smbpasswd file is meant to store information which supplements a + user's /etc/passwd entry, so is the sambaSamAccount object + meant to supplement the UNIX user account information. A sambaSamAccount is a + STRUCTURAL 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. +

+ In order to store all user account information (UNIX and Samba) in the directory, + it is necessary to use the sambaSamAccount 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 makes it possible 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 infrastructure. +

OpenLDAP configuration

+ To include support for the sambaSamAccount object in an OpenLDAP directory + server, first copy the samba.schema file to slapd's configuration directory. + The samba.schema file can be found in the directory examples/LDAP + in the samba source distribution. +

+root# cp samba.schema /etc/openldap/schema/
+

+ Next, include the samba.schema file in slapd.conf. + The sambaSamAccount object contains two attributes which depend upon other schema + files. The 'uid' attribute is defined in cosine.schema and + the 'displayName' attribute is defined in the inetorgperson.schema + file. Both of these must be included before the samba.schema file. +

+## /etc/openldap/slapd.conf
+
+## schema files (core.schema is required by default)
+include	           /etc/openldap/schema/core.schema
+
+## needed for sambaSamAccount
+include            /etc/openldap/schema/cosine.schema
+include            /etc/openldap/schema/inetorgperson.schema
+include            /etc/openldap/schema/samba.schema
+include            /etc/openldap/schema/nis.schema
+....
+

+ It is recommended that you maintain some indices on some of the most useful attributes, + like in the following example, to speed up searches made on sambaSamAccount objectclasses + (and possibly posixAccount and posixGroup as well). +

+# Indices to maintain
+## required by OpenLDAP
+index objectclass             eq
+
+index cn                      pres,sub,eq
+index sn                      pres,sub,eq
+## required to support pdb_getsampwnam
+index uid                     pres,sub,eq
+## required to support pdb_getsambapwrid()
+index displayName             pres,sub,eq
+
+## uncomment these if you are storing posixAccount and
+## posixGroup entries in the directory as well
+##index uidNumber               eq
+##index gidNumber               eq
+##index memberUid               eq
+
+index   sambaSID              eq
+index   sambaPrimaryGroupSID  eq
+index   sambaDomainName       eq
+index   default               sub
+

+ Create the new index by executing: +

+root# ./sbin/slapindex -f slapd.conf
+

+ Remember to restart slapd after making these changes: +

+root# /etc/init.d/slapd restart
+

Initialise the LDAP database

+ Before you can add accounts to the LDAP database you must create the account containers + that they will be stored in. The following LDIF file should be modified to match your + needs (ie: Your DNS entries, etc.). +

+# Organization for Samba Base
+dn: dc=quenya,dc=org
+objectclass: dcObject
+objectclass: organization
+dc: quenya
+o: Quenya Org Network
+description: The Samba-3 Network LDAP Example
+
+# Organizational Role for Directory Management
+dn: cn=Manager,dc=quenya,dc=org
+objectclass: organizationalRole
+cn: Manager
+description: Directory Manager
+
+# Setting up container for users
+dn: ou=People,dc=quenya,dc=org
+objectclass: top
+objectclass: organizationalUnit
+ou: People
+
+# Setting up admin handle for People OU
+dn: cn=admin,ou=People,dc=quenya,dc=org
+cn: admin
+objectclass: top
+objectclass: organizationalRole
+objectclass: simpleSecurityObject
+userPassword: {SSHA}c3ZM9tBaBo9autm1dL3waDS21+JSfQVz
+

+ The userPassword shown above should be generated using slappasswd. +

+ The following command will then load the contents of the LDIF file into the LDAP + database. +

+$ slapadd -v -l initldap.dif
+

+ Do not forget to secure your LDAP server with an adequate access control list, + as well as an admin password. +

Note

+ Before Samba can access the LDAP server you need to store the LDAP admin password + into the Samba-3 secrets.tdb database by: +

+root# smbpasswd -w secret
+

Configuring Samba

+ The following parameters are available in smb.conf only if your + version of samba was built with LDAP support. Samba automatically builds with LDAP support if the + LDAP libraries are found. +

LDAP related smb.conf options: + passdb backend = ldapsam:url, + ldap ssl, + ldap admin dn, + ldap suffix, + ldap filter, + ldap machine suffix, + ldap user suffix, + ldap delete dn, + ldap passwd sync, + ldap trust ids. +

+ These are described in the smb.conf man + page and so will not be repeated here. However, a sample smb.conf file for + use with an LDAP directory could appear as +

Example 11.2. Configuration with LDAP

[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 secretpw' to store the

# passphrase in the secrets.tdb file. If the "ldap admin dn" values

# change, this password will need to be reset.

ldap admin dn = "cn=Samba Manager,ou=people,dc=samba,dc=org"

# Define the SSL option when connecting to the directory

# ('off', 'start tls', or 'on' (default))

ldap ssl = start tls

# syntax: passdb backend = ldapsam:ldap://server-name[:port]

passdb backend = ldapsam:ldap://funball.samba.org

# smbpasswd -x delete the entire dn-entry

ldap delete dn = no

# the machine and user suffix added to the base suffix

# wrote WITHOUT quotes. NULL suffixes by default

ldap user suffix = ou=People

ldap machine suffix = ou=Systems

# Trust unix account information in LDAP

# (see the smb.conf manpage for details)

ldap trust ids = Yes

# 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=sambaSamAccount))"

Accounts and Groups management

+ As users accounts are managed through the sambaSamAccount objectclass, you should + modify your existing administration tools to deal with sambaSamAccount attributes. +

+ Machines accounts are managed with the sambaSamAccount objectclass, just + like users accounts. However, it's up to you to store those accounts + in a different tree of your LDAP namespace: you should use + "ou=Groups,dc=quenya,dc=org" to store groups and + "ou=People,dc=quenya,dc=org" to store users. Just configure your + NSS and PAM accordingly (usually, in the /etc/ldap.conf configuration + file). +

+ In Samba release 3.0, the group management system is based on POSIX + groups. This means that Samba makes use of the posixGroup objectclass. + For now, there is no NT-like group system management (global and local + groups). +

Security and sambaSamAccount

+ There are two important points to remember when discussing the security + of sambaSamAccount entries in the directory. +

Never retrieve the lmPassword or + ntPassword attribute values over an unencrypted LDAP session.
Never allow non-admin users to + view the lmPassword or ntPassword attribute values.

+ These password hashes are clear text equivalents and can be used to impersonate + the user without deriving the original clear text strings. For more information + on the details of LM/NT password hashes, refer to the + Account Information Database section of this chapter. +

+ To remedy the first security issue, the ldap ssl smb.conf parameter defaults + to require an encrypted session (ldap ssl = on) using + the default port of 636 + when contacting the directory server. When using an OpenLDAP 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 + (ldap ssl = off). +

+ Note that the LDAPS protocol is deprecated in favor of the LDAPv3 StartTLS + extended operation. However, the OpenLDAP library still provides support for + the older method of securing communication between clients and servers. +

+ 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 slapd.conf: +

+## allow the "ldap admin dn" access, but deny everyone else
+access to attrs=lmPassword,ntPassword
+     by dn="cn=Samba Admin,ou=people,dc=quenya,dc=org" write
+     by * none
+

LDAP special attributes for sambaSamAccounts

+ The sambaSamAccount objectclass is composed of the following attributes: +

Table 11.1. Attributes in the sambaSamAccount objectclass (LDAP)

`sambaLMPassword`	the LANMAN password 16-byte hash stored as a character +representation of a hexadecimal string.
`sambaNTPassword`	the NT password hash 16-byte stored as a character + representation of a hexadecimal string.
`sambaPwdLastSet`	The integer time in seconds since 1970 when the + `sambaLMPassword` and `sambaNTPassword` attributes were last set. +
`sambaAcctFlags`	string of 11 characters surrounded by square brackets [] + representing account flags such as U (user), W(workstation), X(no password expiration), + I(Domain trust account), H(Home dir required), S(Server trust account), + and D(disabled).
`sambaLogonTime`	Integer value currently unused
`sambaLogoffTime`	Integer value currently unused
`sambaKickoffTime`	Integer value currently unused
`sambaPwdCanChange`	Integer value currently unused
`sambaPwdMustChange`	Integer value currently unused
`sambaHomeDrive`	specifies the drive letter to which to map the + UNC path specified by sambaHomePath. The drive letter must be specified in the form "X:" + where X is the letter of the drive to map. Refer to the "logon drive" parameter in the + smb.conf(5) man page for more information.
`sambaLogonScript`	The sambaLogonScript property specifies the path of + the user's logon script, .CMD, .EXE, or .BAT file. The string can be null. The path + is relative to the netlogon share. Refer to the `logon script` parameter in the + `smb.conf` man page for more information.
`sambaProfilePath`	specifies a path to the user's profile. + This value can be a null string, a local absolute path, or a UNC path. Refer to the + `logon path` parameter in the `smb.conf` man page for more information.
`sambaHomePath`	The sambaHomePath property specifies the path of +the home directory for the user. The string can be null. If sambaHomeDrive is set and specifies +a drive letter, sambaHomePath should be a UNC path. The path must be a network +UNC path of the form `\\server\share\directory`. This value can be a null string. +Refer to the logon home parameter in the `smb.conf` man page for more information. +
`sambaUserWorkstations`	character string value currently unused. +
`sambaSID`	The security identifier(SID) of the user. The windows equivalent of unix uid's.
`sambaPrimaryGroupSID`	the relative identifier (RID) of the primary group + of the user.
`sambaDomainName`	domain the user is part of.

+ The majority of these parameters are only used when Samba is acting as a PDC of + a domain (refer to the Samba as a primary domain controller chapter for details on + how to configure Samba as a Primary Domain Controller). The following four attributes + are only stored with the sambaSamAccount entry if the values are non-default values: +

sambaHomePath
sambaLogonScript
sambaProfilePath
sambaHomeDrive

+ These attributes are only stored with the sambaSamAccount entry if + the values are non-default values. For example, assume TASHTEGO has now been + configured as a PDC and that logon home = \\%L\%u was defined in + its smb.conf file. When a user named "becky" logons to the domain, + the logon home string is expanded to \\TASHTEGO\becky. + 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 logon home parameter is used in its place. Samba + will only write the attribute value to the directory entry if the value is + something other than the default (e.g. \\MOBY\becky). +

Example LDIF Entries for a sambaSamAccount

+ The following is a working LDIF with the inclusion of the posixAccount objectclass: +

+	dn: uid=guest2, ou=people,dc=quenya,dc=org
+	sambaNTPassword: 878D8014606CDA29677A44EFA1353FC7
+	sambaPwdMustChange: 2147483647
+	sambaPrimaryGroupSID: S-1-5-21-2447931902-1787058256-3961074038-513
+	sambaNTPassword: 552902031BEDE9EFAAD3B435B51404EE
+	sambaPwdLastSet: 1010179124
+	sambaLogonTime: 0
+	objectClass: sambaSamAccount
+	uid: guest2
+	sambaKickoffTime: 2147483647
+	sambaAcctFlags: [UX         ]
+	sambaLogoffTime: 2147483647
+	sambaSID: S-1-5-21-2447931902-1787058256-3961074038-5006
+	sambaPwdCanChange: 0
+

+ The following is an LDIF entry for using both the sambaSamAccount and + posixAccount objectclasses: +

+	dn: uid=gcarter, ou=people,dc=quenya,dc=org
+	sambaLogonTime: 0
+	displayName: Gerald Carter
+	sambaLMPassword: 552902031BEDE9EFAAD3B435B51404EE
+	sambaPrimaryGroupSID: S-1-5-21-2447931902-1787058256-3961074038-1201
+	objectClass: posixAccount
+	objectClass: sambaSamAccount
+	sambaAcctFlags: [UX         ]
+	userPassword: {crypt}BpM2ej8Rkzogo
+	uid: gcarter
+	uidNumber: 9000
+	cn: Gerald Carter
+	loginShell: /bin/bash
+	logoffTime: 2147483647
+	gidNumber: 100
+	sambaKickoffTime: 2147483647
+	sambaPwdLastSet: 1010179230
+	sambaSID: S-1-5-21-2447931902-1787058256-3961074038-5004
+	homeDirectory: /home/tashtego/gcarter
+	sambaPwdCanChange: 0
+	sambaPwdMustChange: 2147483647
+	sambaNTPassword: 878D8014606CDA29677A44EFA1353FC7
+

Password synchronisation

+ Since version 3.0 samba can update the non-samba (LDAP) password stored with an account. When + using pam_ldap, this allows changing both unix and windows passwords at once. +

The ldap passwd sync options can have the following values:

yes: When the user changes his password, update + ntPassword, lmPassword + and the password fields.
no: Only update ntPassword and lmPassword.
only: Only update the LDAP password and let the LDAP server worry about the other fields. This option is only available on some LDAP servers. ^[3]

More information can be found in the smb.conf manpage. +

MySQL

+ Every so often someone will come along with a great new idea. Storing of user accounts in an + SQL backend is one of them. Those who want to do this are in the best position to know what the + specific benefits are to them. This may sound like a cop-out, but in truth we can not attempt + to document every nitty little detail why certain things of marginal utility to the bulk of + Samba users might make sense to the rest. In any case, the following instructions should help + the determined SQL user to implement a working system. +

Creating the database

+ You either can set up your own table and specify the field names to pdb_mysql (see below + for the column names) or use the default table. The file examples/pdb/mysql/mysql.dump + contains the correct queries to create the required tables. Use the command : + +

+$ mysql -uusername -hhostname -ppassword \
+databasename < /path/to/samba/examples/pdb/mysql/mysql.dump
+

Configuring

This plugin lacks some good documentation, but here is some short info:

Add a the following to the passdb backend variable in your smb.conf: +

passdb backend = [other-plugins] mysql:identifier [other-plugins]

The identifier can be any string you like, as long as it doesn't collide with + the identifiers of other plugins or other instances of pdb_mysql. If you + specify multiple pdb_mysql.so entries in passdb backend, you also need to + use different identifiers! +

+ Additional options can be given through the smb.conf file in the [global] section. +

Table 11.2. Basic smb.conf options for MySQL passdb backend

Field	Contents
mysql host	host name, defaults to 'localhost'
mysql password
mysql user	defaults to 'samba'
mysql database	defaults to 'samba'
mysql port	defaults to 3306
table	Name of the table containing users

Warning

+ Since the password for the MySQL user is stored in the + smb.conf file, you should make the smb.conf file + readable only to the user that runs Samba This is considered a security + bug and will be fixed soon. +

Names of the columns in this table (I've added column types those columns should have first):

Table 11.3. MySQL field names for MySQL passdb backend

Field	Type	Contents
logon time column	int(9)
logoff time column	int(9)
kickoff time column	int(9)
pass last set time column	int(9)
pass can change time column	int(9)
pass must change time column	int(9)
username column	varchar(255)	unix username
domain column	varchar(255)	NT domain user is part of
nt username column	varchar(255)	NT username
fullname column	varchar(255)	Full name of user
home dir column	varchar(255)	UNIX homedir path
dir drive column	varchar(2)	Directory drive path (eg: 'H:')
logon script column	varchar(255)	Batch file to run on client side when logging on
profile path column	varchar(255)	Path of profile
acct desc column	varchar(255)	Some ASCII NT user data
workstations column	varchar(255)	Workstations user can logon to (or NULL for all)
unknown string column	varchar(255)	unknown string
munged dial column	varchar(255)	?
user sid column	varchar(255)	NT user SID
group sid column	varchar(255)	NT group ID
lanman pass column	varchar(255)	encrypted lanman password
nt pass column	varchar(255)	encrypted nt passwd
plain pass column	varchar(255)	plaintext password
acct control column	int(9)	nt user data
unknown 3 column	int(9)	unknown
logon divs column	int(9)	?
hours len column	int(9)	?
unknown 5 column	int(9)	unknown
unknown 6 column	int(9)	unknown

+ Eventually, you can put a colon (:) after the name of each column, which + should specify the column to update when updating the table. You can also + specify nothing behind the colon - then the data from the field will not be + updated. +

Using plaintext passwords or encrypted password

+ I strongly discourage the use of plaintext passwords, however, you can use them: +

+ If you would like to use plaintext passwords, set + 'identifier:lanman pass column' and 'identifier:nt pass column' to + 'NULL' (without the quotes) and 'identifier:plain pass column' to the + name of the column containing the plaintext passwords. +

+ If you use encrypted passwords, set the 'identifier:plain pass + column' to 'NULL' (without the quotes). This is the default. +

Getting non-column data from the table

+ It is possible to have not all data in the database and making some 'constant'. +

+ For example, you can set 'identifier:fullname column' to : + CONCAT(First_name,' ',Sur_name) +

+ Or, set 'identifier:workstations column' to : + NULL

See the MySQL documentation for more language constructs.

XML

This module requires libxml2 to be installed.

The usage of pdb_xml is pretty straightforward. To export data, use: +

+ $ pdbedit -e xml:filename +

+ (where filename is the name of the file to put the data in) +

+ To import data, use: + $ pdbedit -i xml:filename +

Common Errors

Users can not logon

“I've installed samba, but now I can't log on with my unix account!”

Make sure your user has been added to the current samba passdb backend. Read the section Account Management Tools for details.

Users being added to wrong backend database

+ A few complaints have been received from users that just moved to Samba-3. The following + smb.conf file entries were causing problems, new accounts were being added to the old + smbpasswd file, not to the tdbsam passdb.tdb file: +

[global]

...

passdb backend = smbpasswd, tdbsam

...

+ Samba will add new accounts to the first entry in the passdb backend + parameter entry. If you want to update to the tdbsam, then change the entry to: +

[globals]

...

passdb backend = tdbsam, smbpasswd

...

auth methods does not work

+ If you explicitly set an auth methods parameter, guest must be specified as the first + entry on the line. Eg: auth methods = guest sam. +

+ This is the exact opposite of the requirement for the passdb backend + option, where it must be the LAST parameter on the line. +

^[3]Only when the LDAP server supports LDAP_EXOP_X_MODIFY_PASSWD

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