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-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
-<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter�4.�Samba as Stand-Alone Server</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.59.1"><link rel="home" href="index.html" title="SAMBA Project Documentation"><link rel="up" href="type.html" title="Part�II.�Server Configuration Basics"><link rel="previous" href="ServerType.html" title="Chapter�3.�Nomenclature of Server Types"><link rel="next" href="samba-pdc.html" title="Chapter�5.�
-Samba as an NT4 or Win2k Primary Domain Controller
-"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter�4.�Samba as Stand-Alone Server</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ServerType.html">Prev</a>�</td><th width="60%" align="center">Part�II.�Server Configuration Basics</th><td width="20%" align="right">�<a accesskey="n" href="samba-pdc.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><h2 class="title"><a name="securitylevels"></a>Chapter�4.�Samba as Stand-Alone Server</h2></div><div><div class="author"><h3 class="author">Andrew Tridgell</h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><tt>&lt;<a href="mailto:tridge@samba.org">tridge@samba.org</a>&gt;</tt></p></div></div></div></div><div><div class="author"><h3 class="author">Jelmer R. Vernooij</h3><div class="affiliation"><span class="orgname">The Samba Team<br></span><div class="address"><p><tt>&lt;<a href="mailto:jelmer@samba.org">jelmer@samba.org</a>&gt;</tt></p></div></div></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="securitylevels.html#id2807692">User and Share security level</a></dt><dd><dl><dt><a href="securitylevels.html#id2807727">User Level Security</a></dt><dt><a href="securitylevels.html#id2810322">Share Level Security</a></dt><dt><a href="securitylevels.html#id2812328">Server Level Security</a></dt><dt><a href="securitylevels.html#id2876991">Domain Level Security</a></dt><dt><a href="securitylevels.html#id2877129">ADS Level Security</a></dt></dl></dd></dl></div><p>
-In this section the function and purpose of Samba's <span class="emphasis"><em>security</em></span>
-modes are described.
-</p><div class="sect1" lang="en"><div class="titlepage"><div><h2 class="title" style="clear: both"><a name="id2807692"></a>User and Share security level</h2></div></div><p>
-A SMB server tells the client at startup what &quot;security level&quot; it is
-running. There are two options &quot;share level&quot; and &quot;user level&quot;. Which
-of these two the client receives affects the way the client then tries
-to authenticate itself. It does not directly affect (to any great
-extent) the way the Samba server does security. I know this is
-strange, but it fits in with the client/server approach of SMB. In SMB
-everything is initiated and controlled by the client, and the server
-can only tell the client what is available and whether an action is
-allowed.
-</p><div class="sect2" lang="en"><div class="titlepage"><div><h3 class="title"><a name="id2807727"></a>User Level Security</h3></div></div><p>
-I'll describe user level security first, as its simpler. In user level
-security the client will send a &quot;session setup&quot; command directly after
-the protocol negotiation. This contains a username and password. The
-server can either accept or reject that username/password
-combination. Note that at this stage the server has no idea what
-share the client will eventually try to connect to, so it can't base
-the &quot;accept/reject&quot; on anything other than:
-</p><div class="orderedlist"><ol type="1"><li><p>the username/password</p></li><li><p>the machine that the client is coming from</p></li></ol></div><p>
-If the server accepts the username/password then the client expects to
-be able to mount any share (using a &quot;tree connection&quot;) without
-specifying a password. It expects that all access rights will be as
-the username/password specified in the &quot;session setup&quot;.
-</p><p>
-It is also possible for a client to send multiple &quot;session setup&quot;
-requests. When the server responds it gives the client a &quot;uid&quot; to use
-as an authentication tag for that username/password. The client can
-maintain multiple authentication contexts in this way (WinDD is an
-example of an application that does this)
-</p></div><div class="sect2" lang="en"><div class="titlepage"><div><h3 class="title"><a name="id2810322"></a>Share Level Security</h3></div></div><p>
-Ok, now for share level security. In share level security the client
-authenticates itself separately for each share. It will send a
-password along with each &quot;tree connection&quot; (share mount). It does not
-explicitly send a username with this operation. The client is
-expecting a password to be associated with each share, independent of
-the user. This means that samba has to work out what username the
-client probably wants to use. It is never explicitly sent the
-username. Some commercial SMB servers such as NT actually associate
-passwords directly with shares in share level security, but samba
-always uses the unix authentication scheme where it is a
-username/password that is authenticated, not a &quot;share/password&quot;.
-</p><p>
-Many clients send a &quot;session setup&quot; even if the server is in share
-level security. They normally send a valid username but no
-password. Samba records this username in a list of &quot;possible
-usernames&quot;. When the client then does a &quot;tree connection&quot; it also adds
-to this list the name of the share they try to connect to (useful for
-home directories) and any users listed in the <b>user =</b> <tt>smb.conf</tt>
-line. The password is then checked in turn against these &quot;possible
-usernames&quot;. If a match is found then the client is authenticated as
-that user.
-</p></div><div class="sect2" lang="en"><div class="titlepage"><div><h3 class="title"><a name="id2812328"></a>Server Level Security</h3></div></div><p>
-Finally &quot;server level&quot; security. In server level security the samba
-server reports to the client that it is in user level security. The
-client then does a &quot;session setup&quot; as described earlier. The samba
-server takes the username/password that the client sends and attempts
-to login to the &quot;password server&quot; by sending exactly the same
-username/password that it got from the client. If that server is in
-user level security and accepts the password then samba accepts the
-clients connection. This allows the samba server to use another SMB
-server as the &quot;password server&quot;.
-</p><p>
-You should also note that at the very start of all this, where the
-server tells the client what security level it is in, it also tells
-the client if it supports encryption. If it does then it supplies the
-client with a random &quot;cryptkey&quot;. The client will then send all
-passwords in encrypted form. You have to compile samba with encryption
-enabled to support this feature, and you have to maintain a separate
-smbpasswd file with SMB style encrypted passwords. It is
-cryptographically impossible to translate from unix style encryption
-to SMB style encryption, although there are some fairly simple management
-schemes by which the two could be kept in sync.
-</p><p>
-&quot;security = server&quot; means that Samba reports to clients that
-it is running in &quot;user mode&quot; but actually passes off all authentication
-requests to another &quot;user mode&quot; server. This requires an additional
-parameter &quot;password server =&quot; that points to the real authentication server.
-That real authentication server can be another Samba server or can be a
-Windows NT server, the later natively capable of encrypted password support.
-</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
-<span class="emphasis"><em>Server</em></span> level security is incompatible with what is known
-as <span class="emphasis"><em>schannel</em></span> or &quot;sign and seal&quot; protocols. This means that
-if you want to use <span class="emphasis"><em>server</em></span> level security you must disable
-the use of &quot;sign and seal&quot; on all machines on your network.
-</p></div><div class="sect3" lang="en"><div class="titlepage"><div><h4 class="title"><a name="id2876754"></a>Configuring Samba for Seemless Windows Network Integration</h4></div></div><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 request.
-</p><p>
-When encrypted passwords are used a password that has been entered by the user
-is encrypted in two ways:
-</p><div class="itemizedlist"><ul type="disc"><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 &quot;magic&quot; 8 byte value.
- The resulting 16 bytes for the LanMan hash.
- </p></li></ul></div><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 client re-establishes the connection using
-a cached copy of the password.
-</p><p>
-When Microsoft changed the default password mode, support was dropped 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
-service connection 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><pre class="programlisting">
- <a href="smb.conf.5.html#PASSWORDLEVEL" target="_top">passsword level</a> = <i><tt>integer</tt></i>
- <a href="smb.conf.5.html#USERNAMELEVEL" target="_top">username level</a> = <i><tt>integer</tt></i>
-</pre><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 <i><tt>username level</tt></i> parameter
-is rarely needed.
-</p><p>
-However, passwords 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 <i><tt>password level</tt></i>
-must be set to the maximum number of upper case letter which <span class="emphasis"><em>could</em></span>
-appear is a password. Note that the server OS uses the traditional DES version
-of crypt(), a <i><tt>password level</tt></i> of 8 will result in case
-insensitive passwords as seen from Windows users. This will also result in longer
-login times as Samba has 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><div class="sect3" lang="en"><div class="titlepage"><div><h4 class="title"><a name="id2876930"></a>Use MS Windows NT as an authentication server</h4></div></div><p>
-This method involves the additions of the following parameters in the <tt>smb.conf</tt> file:
-</p><pre class="programlisting">
- encrypt passwords = Yes
- security = server
- password server = &quot;NetBIOS_name_of_PDC&quot;
-</pre><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 an 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><div class="sect2" lang="en"><div class="titlepage"><div><h3 class="title"><a name="id2876991"></a>Domain Level Security</h3></div></div><p>
-When samba is operating in <span class="emphasis"><em>security = domain</em></span> mode this means that
-the Samba server has a domain security trust account (a machine account) and will cause
-all authentication requests to be passed through to the domain controllers.
-</p><div class="sect3" lang="en"><div class="titlepage"><div><h4 class="title"><a name="id2877011"></a>Samba as a member of an MS Windows NT security domain</h4></div></div><p>
-This method involves addition of the following parameters in the <tt>smb.conf</tt> file:
-</p><pre class="programlisting">
- encrypt passwords = Yes
- security = domain
- workgroup = &quot;name of NT domain&quot;
- password server = *
-</pre><p>
-The use of the &quot;*&quot; argument to <b>password server</b> will cause samba to locate the
-domain controller in a way analogous to the way this is done within MS Windows NT.
-This is the default behaviour.
-</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><div class="itemizedlist"><ul type="disc"><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>smbpasswd -r PDC_NAME -j DOMAIN_NAME</b> (samba 2.x)
-
- <b>net join -U administrator%password</b> (samba-3)
- </p></li></ul></div><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 clients other than
-MS Windows through things such as setting an invalid shell in the
-<tt>/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" title="Chapter�15.�Unified Logons between Windows NT and UNIX using Winbind">Winbind Overview</a> chapter
-in this HOWTO collection.
-</p></div></div><div class="sect2" lang="en"><div class="titlepage"><div><h3 class="title"><a name="id2877129"></a>ADS Level Security</h3></div></div><p>
-For information about the configuration option please refer to the entire section entitled
-<span class="emphasis"><em>Samba as an ADS Domain Member.</em></span>
-</p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ServerType.html">Prev</a>�</td><td width="20%" align="center"><a accesskey="u" href="type.html">Up</a></td><td width="40%" align="right">�<a accesskey="n" href="samba-pdc.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter�3.�Nomenclature of Server Types�</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">�Chapter�5.�
-Samba as an NT4 or Win2k Primary Domain Controller
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