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Chapter 3. User information database

3.1. Introduction

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 only send 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.

Next to a 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 his/her + profile is stored, etc. + 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 documentation about the + passdb backend = parameter. +

3.2. 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 which neither requires + plain text passwords on the net or on disk. Unfortunately this + is not available as Samba is stuck with being compatible with + other SMB systems (WinNT, WfWg, Win95 etc).

Note that Windows NT 4.0 Service pack 3 changed the + default for permissible authentication so that plaintext + passwords are never sent over the wire. + The solution to this is either to switch to encrypted passwords + with Samba or edit the Windows NT registry to re-enable plaintext + passwords. See the document WinNT.txt for details on how to do + this.

Other Microsoft operating systems which also exhibit + this behavior includes

MS DOS Network client 3.0 with + the basic network redirector installed

Windows 95 with the network redirector + update installed

Windows 98 [se]

Windows 2000

Note :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.

3.2.1. Advantages of SMB Encryption

plain text passwords are not passed across + the network. Someone using a network sniffer cannot just + record passwords going to the SMB server.

WinNT doesn't like talking to a server + that isn't using SMB 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. +

3.2.2. Advantages of non-encrypted passwords

plain text passwords are not kept + on disk.

uses same password file as other unix + services such as login and ftp

you are probably already using 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.

3.3. 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 you + are changing an NT Domain user's password).

To run smbpasswd as a normal user just type :

$ smbpasswd

Old SMB password: <type old value here - + or hit return if there was no old password>

New SMB Password: <type new value> +

Repeat New SMB Password: <re-type new value +

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.

If invoked by an ordinary user it will only allow the user + to change his or her own Samba password.

If run by the root user smbpasswd may take an optional + argument, specifying the user name whose SMB password you wish to + change. Note that 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 same way + and be familiar to UNIX users who use the passwd or + yppasswd commands.

For more details on using smbpasswd refer + to the man page which will always be the definitive reference.

3.4. 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 +data is stored at all.

3.5. TDB

Samba can also store the user data in a "TDB" (Trivial Database). Using this backend +doesn't require any additional configuration. This backend is recommended for new installations who +don't require LDAP.

3.6. LDAP

3.6.1. Introduction

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

Note that O'Reilly Publishing is working on +a guide to LDAP for System Administrators which has a planned release date of +early summer, 2002.

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. +

3.6.2. Introduction

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 lareg sites. What is needed is an indexed approach +such as is used in databases.
The second problem is that administrators who desired 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 +Identified (RID).

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 commonly 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. --with-ldapsam or +--with-tdbsam) requires compile time support.

When compiling Samba to include the --with-ldapsam 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.

There are a few points to stress about what the --with-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 2000 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/). However, +the details of configuring these packages are beyond the scope of this document.

3.6.3. Supported LDAP Servers

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 bound to be compile errors and bugs. These should not be +hard to fix. If you are so inclined, please be sure to forward all patches to +samba-patches@samba.org and +jerry@samba.org.

3.6.4. 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 sambaAccount objectclass is given here:

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 $ domain ))

The samba.schema file has been formatted for OpenLDAP 2.0. 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 mean to store information which supplements a +user's /etc/passwd entry, so is the sambaAccount object +meant to supplement the UNIX user account information. A sambaAccount 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 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 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.

3.6.5. Configuring Samba with LDAP

3.6.5.1. OpenLDAP configuration

To include support for the sambaAccount object in an OpenLDAP directory +server, first copy the samba.schema file to slapd's configuration directory.

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

Next, include the samba.schema file in slapd.conf. +The sambaAccount 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 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
+
+....

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

# Indices to maintain
+## required by OpenLDAP 2.0
+index objectclass   eq
+
+## support pb_getsampwnam()
+index uid           pres,eq
+## support pdb_getsambapwrid()
+index rid           eq
+
+## uncomment these if you are storing posixAccount and
+## posixGroup entries in the directory as well
+##index uidNumber     eq
+##index gidNumber     eq
+##index cn            eq
+##index memberUid     eq

3.6.5.2. Configuring Samba

The following parameters are available in smb.conf only with --with-ldapsam +was included with compiling Samba.

ldap ssl
ldap server
ldap admin dn
ldap suffix
ldap filter
ldap port

These are described in the smb.conf(5) man +page and so will not be repeated here. However, a sample smb.conf file for +use with an LDAP directory could appear as

## /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 secretpw' 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=Samba Manager,ou=people,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))"

3.6.6. Accounts and Groups management

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

Machines accounts are managed with the sambaAccount objectclass, just +like users accounts. However, it's up to you to stored thoses accounts +in a different tree of you LDAP namespace: you should use +"ou=Groups,dc=plainjoe,dc=org" to store groups and +"ou=People,dc=plainjoe,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 make usage of the posixGroup objectclass. +For now, there is no NT-like group system management (global and local +groups).

3.6.7. Security and sambaAccount

There are two important points to remember when discussing the security +of sambaAccount 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 ENCRYPTION chapter of the Samba-HOWTO-Collection.

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 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 +(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=plainjoe,dc=org" write
+     by * none

3.6.8. LDAP specials attributes for sambaAccounts

The sambaAccount objectclass is composed of the following attributes:

lmPassword: the LANMAN password 16-byte hash stored as a character + representation of a hexidecimal string.
ntPassword: the NT password hash 16-byte stored as a character + representation of a hexidecimal string.
pwdLastSet: The integer time in seconds since 1970 when the + lmPassword and ntPassword attributes were last set. +
acctFlags: string of 11 characters surrounded by square brackets [] + representing account flags such as U (user), W(workstation), X(no password expiration), and + D(disabled).
logonTime: Integer value currently unused
logoffTime: Integer value currently unused
kickoffTime: Integer value currently unused
pwdCanChange: Integer value currently unused
pwdMustChange: Integer value currently unused
homeDrive: specifies the drive letter to which to map the + UNC path specified by homeDirectory. 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.
scriptPath: The scriptPath 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(5) man page for more information.
profilePath: 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(5) man page for more information.
smbHome: The homeDirectory property specifies the path of + the home directory for the user. The string can be null. If homeDrive is set and specifies + a drive letter, homeDirectory 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(5) man page for more information. +
userWorkstation: character string value currently unused. +
rid: the integer representation of the user's relative identifier + (RID).
primaryGroupID: the relative identifier (RID) of the primary group + of the user.

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

smbHome
scriptPath
logonPath
homeDrive

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 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 is the value is +something other than the default (e.g. \\MOBY\becky).

3.6.9. Example LDIF Entries for a sambaAccount

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

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

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

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

3.7. MySQL

3.7.1. Building

To build the plugin, run make bin/pdb_mysql.so +in the source/ directory of samba distribution.

Next, copy pdb_mysql.so to any location you want. I +strongly recommend installing it in $PREFIX/lib or /usr/lib/samba/

3.7.2. 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

3.7.3. 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] plugin:/location/to/pdb_mysql.so: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 thru the smb.conf file in the [global] section.

identifier:mysql host                     - host name, defaults to 'localhost'
+identifier:mysql password
+identifier:mysql user                     - defaults to 'samba'
+identifier:mysql database                 - defaults to 'samba'
+identifier:mysql port                     - defaults to 3306
+identifier:table                          - Name of the table containing users

Since the password for the mysql user is stored in the +smb.conf file, you should make the 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):

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

3.7.4. 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.

3.7.5. 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.

3.8. Passdb XML plugin

3.8.1. Building

This module requires libxml2 to be installed.

To build pdb_xml, run: make bin/pdb_xml.so in +the directory source/.

3.8.2. Usage

The usage of pdb_xml is pretty straightforward. To export data, use: + +pdbedit -e plugin:/usr/lib/samba/pdb_xml.so:filename + +(where filename is the name of the file to put the data in)

To import data, use: +pdbedit -i plugin:/usr/lib/samba/pdb_xml.so:filename -e current-pdb + +Where filename is the name to read the data from and current-pdb to put it in.

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