Integrating-with-Windows.html [plain text]
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><DIV
CLASS="TITLEPAGE"
><H1
CLASS="TITLE"
><A
NAME="INTEGRATE-MS-NETWORKS"
>Integrating MS Windows networks with Samba</A
></H1
><HR></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="AEN3"
>Agenda</A
></H1
><P
>To identify the key functional mechanisms of MS Windows networking
to enable the deployment of Samba as a means of extending and/or
replacing MS Windows NT/2000 technology.</P
><P
>We will examine:</P
><P
></P
><OL
TYPE="1"
><LI
><P
>Name resolution in a pure Unix/Linux TCP/IP
environment
</P
></LI
><LI
><P
>Name resolution as used within MS Windows
networking
</P
></LI
><LI
><P
>How browsing functions and how to deploy stable
and dependable browsing using Samba
</P
></LI
><LI
><P
>MS Windows security options and how to
configure Samba for seemless integration
</P
></LI
><LI
><P
>Configuration of Samba as:</P
><P
></P
><OL
TYPE="a"
><LI
><P
>A stand-alone server</P
></LI
><LI
><P
>An MS Windows NT 3.x/4.0 security domain member
</P
></LI
><LI
><P
>An alternative to an MS Windows NT 3.x/4.0 Domain Controller
</P
></LI
></OL
></LI
></OL
></DIV
><DIV
CLASS="SECT1"
><HR><H1
CLASS="SECT1"
><A
NAME="AEN25"
>Name Resolution in a pure Unix/Linux world</A
></H1
><P
>The key configuration files covered in this section are:</P
><P
></P
><UL
><LI
><P
><TT
CLASS="FILENAME"
>/etc/hosts</TT
></P
></LI
><LI
><P
><TT
CLASS="FILENAME"
>/etc/resolv.conf</TT
></P
></LI
><LI
><P
><TT
CLASS="FILENAME"
>/etc/host.conf</TT
></P
></LI
><LI
><P
><TT
CLASS="FILENAME"
>/etc/nsswitch.conf</TT
></P
></LI
></UL
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN41"
><TT
CLASS="FILENAME"
>/etc/hosts</TT
></A
></H2
><P
>Contains a static list of IP Addresses and names.
eg:</P
><P
><PRE
CLASS="PROGRAMLISTING"
> 127.0.0.1 localhost localhost.localdomain
192.168.1.1 bigbox.caldera.com bigbox alias4box</PRE
></P
><P
>The purpose of <TT
CLASS="FILENAME"
>/etc/hosts</TT
> is to provide a
name resolution mechanism so that uses do not need to remember
IP addresses.</P
><P
>Network packets that are sent over the physical network transport
layer communicate not via IP addresses but rather using the Media
Access Control address, or MAC address. IP Addresses are currently
32 bits in length and are typically presented as four (4) decimal
numbers that are separated by a dot (or period). eg: 168.192.1.1</P
><P
>MAC Addresses use 48 bits (or 6 bytes) and are typically represented
as two digit hexadecimal numbers separated by colons. eg:
40:8e:0a:12:34:56</P
><P
>Every network interfrace must have an MAC address. Associated with
a MAC address there may be one or more IP addresses. There is NO
relationship between an IP address and a MAC address, all such assignments
are arbitary or discretionary in nature. At the most basic level all
network communications takes place using MAC addressing. Since MAC
addresses must be globally unique, and generally remains fixed for
any particular interface, the assignment of an IP address makes sense
from a network management perspective. More than one IP address can
be assigned per MAC address. One address must be the primary IP address,
this is the address that will be returned in the ARP reply.</P
><P
>When a user or a process wants to communicate with another machine
the protocol implementation ensures that the "machine name" or "host
name" is resolved to an IP address in a manner that is controlled
by the TCP/IP configuration control files. The file
<TT
CLASS="FILENAME"
>/etc/hosts</TT
> is one such file.</P
><P
>When the IP address of the destination interface has been
determined a protocol called ARP/RARP isused to identify
the MAC address of the target interface. ARP stands for Address
Resolution Protocol, and is a broadcast oriented method that
uses UDP (User Datagram Protocol) to send a request to all
interfaces on the local network segment using the all 1's MAC
address. Network interfaces are programmed to respond to two
MAC addresses only; their own unique address and the address
ff:ff:ff:ff:ff:ff. The reply packet from an ARP request will
contain the MAC address and the primary IP address for each
interface.</P
><P
>The <TT
CLASS="FILENAME"
>/etc/hosts</TT
> file is foundational to all
Unix/Linux TCP/IP installations and as a minumum will contain
the localhost and local network interface IP addresses and the
primary names by which they are known within the local machine.
This file helps to prime the pump so that a basic level of name
resolution can exist before any other method of name resolution
becomes available.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN57"
><TT
CLASS="FILENAME"
>/etc/resolv.conf</TT
></A
></H2
><P
>This file tells the name resolution libraries:</P
><P
></P
><UL
><LI
><P
>The name of the domain to which the machine
belongs
</P
></LI
><LI
><P
>The name(s) of any domains that should be
automatically searched when trying to resolve unqualified
host names to their IP address
</P
></LI
><LI
><P
>The name or IP address of available Domain
Name Servers that may be asked to perform name to address
translation lookups
</P
></LI
></UL
></DIV
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN68"
><TT
CLASS="FILENAME"
>/etc/host.conf</TT
></A
></H2
><P
><TT
CLASS="FILENAME"
>/etc/host.conf</TT
> is the primary means by
which the setting in /etc/resolv.conf may be affected. It is a
critical configuration file. This file controls the order by
which name resolution may procede. The typical structure is:</P
><P
><PRE
CLASS="PROGRAMLISTING"
> order hosts,bind
multi on</PRE
></P
><P
>then both addresses should be returned. Please refer to the
man page for host.conf for further details.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN76"
><TT
CLASS="FILENAME"
>/etc/nsswitch.conf</TT
></A
></H2
><P
>This file controls the actual name resolution targets. The
file typically has resolver object specifications as follows:</P
><P
><PRE
CLASS="PROGRAMLISTING"
> # /etc/nsswitch.conf
#
# Name Service Switch configuration file.
#
passwd: compat
# Alternative entries for password authentication are:
# passwd: compat files nis ldap winbind
shadow: compat
group: compat
hosts: files nis dns
# Alternative entries for host name resolution are:
# hosts: files dns nis nis+ hesoid db compat ldap wins
networks: nis files dns
ethers: nis files
protocols: nis files
rpc: nis files
services: nis files</PRE
></P
><P
>Of course, each of these mechanisms requires that the appropriate
facilities and/or services are correctly configured.</P
><P
>It should be noted that unless a network request/message must be
sent, TCP/IP networks are silent. All TCP/IP communications assumes a
principal of speaking only when necessary.</P
><P
>Samba version 2.2.0 will add Linux support for extensions to
the name service switch infrastructure so that linux clients will
be able to obtain resolution of MS Windows NetBIOS names to IP
Addresses. To gain this functionality Samba needs to be compiled
with appropriate arguments to the make command (ie: <B
CLASS="COMMAND"
>make
nsswitch/libnss_wins.so</B
>). The resulting library should
then be installed in the <TT
CLASS="FILENAME"
>/lib</TT
> directory and
the "wins" parameter needs to be added to the "hosts:" line in
the <TT
CLASS="FILENAME"
>/etc/nsswitch.conf</TT
> file. At this point it
will be possible to ping any MS Windows machine by it's NetBIOS
machine name, so long as that machine is within the workgroup to
which both the samba machine and the MS Windows machine belong.</P
></DIV
></DIV
><DIV
CLASS="SECT1"
><HR><H1
CLASS="SECT1"
><A
NAME="AEN88"
>Name resolution as used within MS Windows networking</A
></H1
><P
>MS Windows networking is predicated about the name each machine
is given. This name is known variously (and inconsistently) as
the "computer name", "machine name", "networking name", "netbios name",
"SMB name". All terms mean the same thing with the exception of
"netbios name" which can apply also to the name of the workgroup or the
domain name. The terms "workgroup" and "domain" are really just a
simply name with which the machine is associated. All NetBIOS names
are exactly 16 characters in length. The 16th character is reserved.
It is used to store a one byte value that indicates service level
information for the NetBIOS name that is registered. A NetBIOS machine
name is therefore registered for each service type that is provided by
the client/server.</P
><P
>The following are typical NetBIOS name/service type registrations:</P
><P
><PRE
CLASS="PROGRAMLISTING"
> Unique NetBIOS Names:
MACHINENAME<00> = Server Service is running on MACHINENAME
MACHINENAME<03> = Generic Machine Name (NetBIOS name)
MACHINENAME<20> = LanMan Server service is running on MACHINENAME
WORKGROUP<1b> = Domain Master Browser
Group Names:
WORKGROUP<03> = Generic Name registered by all members of WORKGROUP
WORKGROUP<1c> = Domain Controllers / Netlogon Servers
WORKGROUP<1d> = Local Master Browsers
WORKGROUP<1e> = Internet Name Resolvers</PRE
></P
><P
>It should be noted that all NetBIOS machines register their own
names as per the above. This is in vast contrast to TCP/IP
installations where traditionally the system administrator will
determine in the /etc/hosts or in the DNS database what names
are associated with each IP address.</P
><P
>One further point of clarification should be noted, the <TT
CLASS="FILENAME"
>/etc/hosts</TT
>
file and the DNS records do not provide the NetBIOS name type information
that MS Windows clients depend on to locate the type of service that may
be needed. An example of this is what happens when an MS Windows client
wants to locate a domain logon server. It find this service and the IP
address of a server that provides it by performing a lookup (via a
NetBIOS broadcast) for enumeration of all machines that have
registered the name type *<1c>. A logon request is then sent to each
IP address that is returned in the enumerated list of IP addresses. Which
ever machine first replies then ends up providing the logon services.</P
><P
>The name "workgroup" or "domain" really can be confusing since these
have the added significance of indicating what is the security
architecture of the MS Windows network. The term "workgroup" indicates
that the primary nature of the network environment is that of a
peer-to-peer design. In a WORKGROUP all machines are responsible for
their own security, and generally such security is limited to use of
just a password (known as SHARE MORE security). In most situations
with peer-to-peer networking the users who control their own machines
will simply opt to have no security at all. It is possible to have
USER MODE security in a WORKGROUP environment, thus requiring use
of a user name and a matching password.</P
><P
>MS Windows networking is thus predetermined to use machine names
for all local and remote machine message passing. The protocol used is
called Server Message Block (SMB) and this is implemented using
the NetBIOS protocol (Network Basic Input Output System). NetBIOS can
be encapsulated using LLC (Logical Link Control) protocol - in which case
the resulting protocol is called NetBEUI (Network Basic Extended User
Interface). NetBIOS can also be run over IPX (Internetworking Packet
Exchange) protocol as used by Novell NetWare, and it can be run
over TCP/IP protocols - in which case the resulting protocol is called
NBT or NetBT, the NetBIOS over TCP/IP.</P
><P
>MS Windows machines use a complex array of name resolution mechanisms.
Since we are primarily concerned with TCP/IP this demonstration is
limited to this area.</P
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN100"
>The NetBIOS Name Cache</A
></H2
><P
>All MS Windows machines employ an in memory buffer in which is
stored the NetBIOS names and their IP addresses for all external
machines that that the local machine has communicated with over the
past 10-15 minutes. It is more efficient to obtain an IP address
for a machine from the local cache than it is to go through all the
configured name resolution mechanisms.</P
><P
>If a machine whose name is in the local name cache has been shut
down before the name had been expired and flushed from the cache, then
an attempt to exchange a message with that machine will be subject
to time-out delays. ie: It's name is in the cache, so a name resolution
lookup will succeed, but the machine can not respond. This can be
frustrating for users - but it is a characteristic of the protocol.</P
><P
>The MS Windows utility that allows examination of the NetBIOS
name cache is called "nbtstat". The Samba equivalent of this
is called "nmblookup".</P
></DIV
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN105"
>The LMHOSTS file</A
></H2
><P
>This file is usually located in MS Windows NT 4.0 or
2000 in <TT
CLASS="FILENAME"
>C:\WINNT\SYSTEM32\DRIVERS\ETC</TT
> and contains
the IP Address and the machine name in matched pairs. The
<TT
CLASS="FILENAME"
>LMHOSTS</TT
> file performs NetBIOS name
to IP address mapping oriented.</P
><P
>It typically looks like:</P
><P
><PRE
CLASS="PROGRAMLISTING"
> # Copyright (c) 1998 Microsoft Corp.
#
# This is a sample LMHOSTS file used by the Microsoft Wins Client (NetBIOS
# over TCP/IP) stack for Windows98
#
# This file contains the mappings of IP addresses to NT computernames
# (NetBIOS) names. Each entry should be kept on an individual line.
# The IP address should be placed in the first column followed by the
# corresponding computername. The address and the comptername
# should be separated by at least one space or tab. The "#" character
# is generally used to denote the start of a comment (see the exceptions
# below).
#
# This file is compatible with Microsoft LAN Manager 2.x TCP/IP lmhosts
# files and offers the following extensions:
#
# #PRE
# #DOM:<domain>
# #INCLUDE <filename>
# #BEGIN_ALTERNATE
# #END_ALTERNATE
# \0xnn (non-printing character support)
#
# Following any entry in the file with the characters "#PRE" will cause
# the entry to be preloaded into the name cache. By default, entries are
# not preloaded, but are parsed only after dynamic name resolution fails.
#
# Following an entry with the "#DOM:<domain>" tag will associate the
# entry with the domain specified by <domain>. This affects how the
# browser and logon services behave in TCP/IP environments. To preload
# the host name associated with #DOM entry, it is necessary to also add a
# #PRE to the line. The <domain> is always preloaded although it will not
# be shown when the name cache is viewed.
#
# Specifying "#INCLUDE <filename>" will force the RFC NetBIOS (NBT)
# software to seek the specified <filename> and parse it as if it were
# local. <filename> is generally a UNC-based name, allowing a
# centralized lmhosts file to be maintained on a server.
# It is ALWAYS necessary to provide a mapping for the IP address of the
# server prior to the #INCLUDE. This mapping must use the #PRE directive.
# In addtion the share "public" in the example below must be in the
# LanManServer list of "NullSessionShares" in order for client machines to
# be able to read the lmhosts file successfully. This key is under
# \machine\system\currentcontrolset\services\lanmanserver\parameters\nullsessionshares
# in the registry. Simply add "public" to the list found there.
#
# The #BEGIN_ and #END_ALTERNATE keywords allow multiple #INCLUDE
# statements to be grouped together. Any single successful include
# will cause the group to succeed.
#
# Finally, non-printing characters can be embedded in mappings by
# first surrounding the NetBIOS name in quotations, then using the
# \0xnn notation to specify a hex value for a non-printing character.
#
# The following example illustrates all of these extensions:
#
# 102.54.94.97 rhino #PRE #DOM:networking #net group's DC
# 102.54.94.102 "appname \0x14" #special app server
# 102.54.94.123 popular #PRE #source server
# 102.54.94.117 localsrv #PRE #needed for the include
#
# #BEGIN_ALTERNATE
# #INCLUDE \\localsrv\public\lmhosts
# #INCLUDE \\rhino\public\lmhosts
# #END_ALTERNATE
#
# In the above example, the "appname" server contains a special
# character in its name, the "popular" and "localsrv" server names are
# preloaded, and the "rhino" server name is specified so it can be used
# to later #INCLUDE a centrally maintained lmhosts file if the "localsrv"
# system is unavailable.
#
# Note that the whole file is parsed including comments on each lookup,
# so keeping the number of comments to a minimum will improve performance.
# Therefore it is not advisable to simply add lmhosts file entries onto the
# end of this file.</PRE
></P
></DIV
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN113"
>HOSTS file</A
></H2
><P
>This file is usually located in MS Windows NT 4.0 or 2000 in
<TT
CLASS="FILENAME"
>C:\WINNT\SYSTEM32\DRIVERS\ETC</TT
> and contains
the IP Address and the IP hostname in matched pairs. It can be
used by the name resolution infrastructure in MS Windows, depending
on how the TCP/IP environment is configured. This file is in
every way the equivalent of the Unix/Linux <TT
CLASS="FILENAME"
>/etc/hosts</TT
> file.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN118"
>DNS Lookup</A
></H2
><P
>This capability is configured in the TCP/IP setup area in the network
configuration facility. If enabled an elaborate name resolution sequence
is followed the precise nature of which isdependant on what the NetBIOS
Node Type parameter is configured to. A Node Type of 0 means use
NetBIOS broadcast (over UDP broadcast) is first used if the name
that is the subject of a name lookup is not found in the NetBIOS name
cache. If that fails then DNS, HOSTS and LMHOSTS are checked. If set to
Node Type 8, then a NetBIOS Unicast (over UDP Unicast) is sent to the
WINS Server to obtain a lookup before DNS, HOSTS, LMHOSTS, or broadcast
lookup is used.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN121"
>WINS Lookup</A
></H2
><P
>A WINS (Windows Internet Name Server) service is the equivaent of the
rfc1001/1002 specified NBNS (NetBIOS Name Server). A WINS server stores
the names and IP addresses that are registered by a Windows client
if the TCP/IP setup has been given at least one WINS Server IP Address.</P
><P
>To configure Samba to be a WINS server the following parameter needs
to be added to the <TT
CLASS="FILENAME"
>smb.conf</TT
> file:</P
><P
><PRE
CLASS="PROGRAMLISTING"
> wins support = Yes</PRE
></P
><P
>To configure Samba to use a WINS server the following parameters are
needed in the smb.conf file:</P
><P
><PRE
CLASS="PROGRAMLISTING"
> wins support = No
wins server = xxx.xxx.xxx.xxx</PRE
></P
><P
>where <TT
CLASS="REPLACEABLE"
><I
>xxx.xxx.xxx.xxx</I
></TT
> is the IP address
of the WINS server.</P
></DIV
></DIV
><DIV
CLASS="SECT1"
><HR><H1
CLASS="SECT1"
><A
NAME="AEN133"
>How browsing functions and how to deploy stable and
dependable browsing using Samba</A
></H1
><P
>As stated above, MS Windows machines register their NetBIOS names
(ie: the machine name for each service type in operation) on start
up. Also, as stated above, the exact method by which this name registration
takes place is determined by whether or not the MS Windows client/server
has been given a WINS server address, whether or not LMHOSTS lookup
is enabled, or if DNS for NetBIOS name resolution is enabled, etc.</P
><P
>In the case where there is no WINS server all name registrations as
well as name lookups are done by UDP broadcast. This isolates name
resolution to the local subnet, unless LMHOSTS is used to list all
names and IP addresses. In such situations Samba provides a means by
which the samba server name may be forcibly injected into the browse
list of a remote MS Windows network (using the "remote announce" parameter).</P
><P
>Where a WINS server is used, the MS Windows client will use UDP
unicast to register with the WINS server. Such packets can be routed
and thus WINS allows name resolution to function across routed networks.</P
><P
>During the startup process an election will take place to create a
local master browser if one does not already exist. On each NetBIOS network
one machine will be elected to function as the domain master browser. This
domain browsing has nothing to do with MS security domain control.
Instead, the domain master browser serves the role of contacting each local
master browser (found by asking WINS or from LMHOSTS) and exchanging browse
list contents. This way every master browser will eventually obtain a complete
list of all machines that are on the network. Every 11-15 minutes an election
is held to determine which machine will be the master browser. By nature of
the election criteria used, the machine with the highest uptime, or the
most senior protocol version, or other criteria, will win the election
as domain master browser.</P
><P
>Clients wishing to browse the network make use of this list, but also depend
on the availability of correct name resolution to the respective IP
address/addresses. </P
><P
>Any configuration that breaks name resolution and/or browsing intrinsics
will annoy users because they will have to put up with protracted
inability to use the network services.</P
><P
>Samba supports a feature that allows forced synchonisation
of browse lists across routed networks using the "remote
browse sync" parameter in the smb.conf file. This causes Samba
to contact the local master browser on a remote network and
to request browse list synchronisation. This effectively bridges
two networks that are separated by routers. The two remote
networks may use either broadcast based name resolution or WINS
based name resolution, but it should be noted that the "remote
browse sync" parameter provides browse list synchronisation - and
that is distinct from name to address resolution, in other
words, for cross subnet browsing to function correctly it is
essential that a name to address resolution mechanism be provided.
This mechanism could be via DNS, <TT
CLASS="FILENAME"
>/etc/hosts</TT
>,
and so on.</P
></DIV
><DIV
CLASS="SECT1"
><HR><H1
CLASS="SECT1"
><A
NAME="AEN143"
>MS Windows security options and how to configure
Samba for seemless integration</A
></H1
><P
>MS Windows clients may use encrypted passwords as part of a
challenege/response authentication model (a.k.a. NTLMv1) or
alone, or clear text strings for simple password based
authentication. It should be realized that with the SMB
protocol the password is passed over the network either
in plain text or encrypted, but not both in the same
authentication requets.</P
><P
>When encrypted passwords are used a password that has been
entered by the user is encrypted in two ways:</P
><P
></P
><UL
><LI
><P
>An MD4 hash of the UNICODE of the password
string. This is known as the NT hash.
</P
></LI
><LI
><P
>The password is converted to upper case,
and then padded or trucated to 14 bytes. This string is
then appended with 5 bytes of NULL characters and split to
form two 56 bit DES keys to encrypt a "magic" 8 byte value.
The resulting 16 bytes for the LanMan hash.
</P
></LI
></UL
><P
>You should refer to the <A
HREF="ENCRYPTION.html"
TARGET="_top"
>Password Encryption</A
> chapter in this HOWTO collection
for more details on the inner workings</P
><P
>MS Windows 95 pre-service pack 1, MS Windows NT versions 3.x
and version 4.0 pre-service pack 3 will use either mode of
password authentication. All versions of MS Windows that follow
these versions no longer support plain text passwords by default.</P
><P
>MS Windows clients have a habit of dropping network mappings that
have been idle for 10 minutes or longer. When the user attempts to
use the mapped drive connection that has been dropped the SMB protocol
has a mechanism by which the connection can be re-established using
a cached copy of the password.</P
><P
>When Microsoft changed the default password mode, they dropped support for
caching of the plain text password. This means that when the registry
parameter is changed to re-enable use of plain text passwords it appears to
work, but when a dropped mapping attempts to revalidate it will fail if
the remote authentication server does not support encrypted passwords.
This means that it is definitely not a good idea to re-enable plain text
password support in such clients.</P
><P
>The following parameters can be used to work around the
issue of Windows 9x client upper casing usernames and
password before transmitting them to the SMB server
when using clear text authentication.</P
><P
><PRE
CLASS="PROGRAMLISTING"
> <A
HREF="smb.conf.5.html#PASSWORDLEVEL"
TARGET="_top"
>passsword level</A
> = <TT
CLASS="REPLACEABLE"
><I
>integer</I
></TT
>
<A
HREF="smb.conf.5.html#USERNAMELEVEL"
TARGET="_top"
>username level</A
> = <TT
CLASS="REPLACEABLE"
><I
>integer</I
></TT
></PRE
></P
><P
>By default Samba will lower case the username before attempting
to lookup the user in the database of local system accounts.
Because UNIX usernames conventionally only contain lower case
character, the <TT
CLASS="PARAMETER"
><I
>username level</I
></TT
> parameter
is rarely even needed.</P
><P
>However, password on UNIX systems often make use of mixed case
characters. This means that in order for a user on a Windows 9x
client to connect to a Samba server using clear text authentication,
the <TT
CLASS="PARAMETER"
><I
>password level</I
></TT
> must be set to the maximum
number of upper case letter which <I
CLASS="EMPHASIS"
>could</I
> appear
is a password. Note that is the server OS uses the traditional
DES version of crypt(), then a <TT
CLASS="PARAMETER"
><I
>password level</I
></TT
>
of 8 will result in case insensitive passwords as seen from Windows
users. This will also result in longer login times as Samba
hash to compute the permutations of the password string and
try them one by one until a match is located (or all combinations fail).</P
><P
>The best option to adopt is to enable support for encrypted passwords
where ever Samba is used. There are three configuration possibilities
for support of encrypted passwords:</P
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN171"
>Use MS Windows NT as an authentication server</A
></H2
><P
>This method involves the additions of the following parameters
in the smb.conf file:</P
><P
><PRE
CLASS="PROGRAMLISTING"
> encrypt passwords = Yes
security = server
password server = "NetBIOS_name_of_PDC"</PRE
></P
><P
>There are two ways of identifying whether or not a username and
password pair was valid or not. One uses the reply information provided
as part of the authentication messaging process, the other uses
just and error code.</P
><P
>The down-side of this mode of configuration is the fact that
for security reasons Samba will send the password server a bogus
username and a bogus password and if the remote server fails to
reject the username and password pair then an alternative mode
of identification of validation is used. Where a site uses password
lock out after a certain number of failed authentication attempts
this will result in user lockouts.</P
><P
>Use of this mode of authentication does require there to be
a standard Unix account for the user, this account can be blocked
to prevent logons by other than MS Windows clients.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN179"
>Make Samba a member of an MS Windows NT security domain</A
></H2
><P
>This method involves additon of the following paramters in the smb.conf file:</P
><P
><PRE
CLASS="PROGRAMLISTING"
> encrypt passwords = Yes
security = domain
workgroup = "name of NT domain"
password server = *</PRE
></P
><P
>The use of the "*" argument to "password server" will cause samba
to locate the domain controller in a way analogous to the way
this is done within MS Windows NT.</P
><P
>In order for this method to work the Samba server needs to join the
MS Windows NT security domain. This is done as follows:</P
><P
></P
><UL
><LI
><P
>On the MS Windows NT domain controller using
the Server Manager add a machine account for the Samba server.
</P
></LI
><LI
><P
>Next, on the Linux system execute:
<B
CLASS="COMMAND"
>smbpasswd -r PDC_NAME -j DOMAIN_NAME</B
>
</P
></LI
></UL
><P
>Use of this mode of authentication does require there to be
a standard Unix account for the user in order to assign
a uid once the account has been authenticated by the remote
Windows DC. This account can be blocked to prevent logons by
other than MS Windows clients by things such as setting an invalid
shell in the <TT
CLASS="FILENAME"
>/etc/passwd</TT
> entry.</P
><P
>An alternative to assigning UIDs to Windows users on a
Samba member server is presented in the <A
HREF="winbind.html"
TARGET="_top"
>Winbind Overview</A
> chapter in
this HOWTO collection.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H2
CLASS="SECT2"
><A
NAME="AEN196"
>Configure Samba as an authentication server</A
></H2
><P
>This mode of authentication demands that there be on the
Unix/Linux system both a Unix style account as well as and
smbpasswd entry for the user. The Unix system account can be
locked if required as only the encrypted password will be
used for SMB client authentication.</P
><P
>This method involves addition of the following parameters to
the smb.conf file:</P
><P
><PRE
CLASS="PROGRAMLISTING"
>## please refer to the Samba PDC HOWTO chapter later in
## this collection for more details
[global]
encrypt passwords = Yes
security = user
domain logons = Yes
; an OS level of 33 or more is recommended
os level = 33
[NETLOGON]
path = /somewhare/in/file/system
read only = yes</PRE
></P
><P
>in order for this method to work a Unix system account needs
to be created for each user, as well as for each MS Windows NT/2000
machine. The following structure is required.</P
><DIV
CLASS="SECT3"
><HR><H3
CLASS="SECT3"
><A
NAME="AEN203"
>Users</A
></H3
><P
>A user account that may provide a home directory should be
created. The following Linux system commands are typical of
the procedure for creating an account.</P
><P
><PRE
CLASS="PROGRAMLISTING"
> # useradd -s /bin/bash -d /home/"userid" -m "userid"
# passwd "userid"
Enter Password: <pw>
# smbpasswd -a "userid"
Enter Password: <pw></PRE
></P
></DIV
><DIV
CLASS="SECT3"
><HR><H3
CLASS="SECT3"
><A
NAME="AEN208"
>MS Windows NT Machine Accounts</A
></H3
><P
>These are required only when Samba is used as a domain
controller. Refer to the Samba-PDC-HOWTO for more details.</P
><P
><PRE
CLASS="PROGRAMLISTING"
> # useradd -s /bin/false -d /dev/null "machine_name"\$
# passwd -l "machine_name"\$
# smbpasswd -a -m "machine_name"</PRE
></P
></DIV
></DIV
></DIV
><DIV
CLASS="SECT1"
><HR><H1
CLASS="SECT1"
><A
NAME="AEN213"
>Conclusions</A
></H1
><P
>Samba provides a flexible means to operate as...</P
><P
></P
><UL
><LI
><P
>A Stand-alone server - No special action is needed
other than to create user accounts. Stand-alone servers do NOT
provide network logon services, meaning that machines that use this
server do NOT perform a domain logon but instead make use only of
the MS Windows logon which is local to the MS Windows
workstation/server.
</P
></LI
><LI
><P
>An MS Windows NT 3.x/4.0 security domain member.
</P
></LI
><LI
><P
>An alternative to an MS Windows NT 3.x/4.0
Domain Controller.
</P
></LI
></UL
></DIV
></DIV
></BODY
></HTML
>