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diff --git a/docs/htmldocs/Samba3-ByExample/primer.html b/docs/htmldocs/Samba3-ByExample/primer.html new file mode 100644 index 0000000000..50481ef7ff --- /dev/null +++ b/docs/htmldocs/Samba3-ByExample/primer.html @@ -0,0 +1,546 @@ +<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 16. Networking Primer</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.71.0"><link rel="start" href="index.html" title="Samba-3 by Example"><link rel="up" href="RefSection.html" title="Part III. Reference Section"><link rel="prev" href="appendix.html" title="Chapter 15. A Collection of Useful Tidbits"><link rel="next" href="gpl.html" title="Appendix A. GNU General Public License"></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 16. Networking Primer</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="appendix.html">Prev</a> </td><th width="60%" align="center">Part III. Reference Section</th><td width="20%" align="right"> <a accesskey="n" href="gpl.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="primer"></a>Chapter 16. Networking Primer</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="primer.html#id386080">Requirements and Notes</a></span></dt><dt><span class="sect1"><a href="primer.html#id386216">Introduction</a></span></dt><dd><dl><dt><span class="sect2"><a href="primer.html#id386266">Assignment Tasks</a></span></dt></dl></dd><dt><span class="sect1"><a href="primer.html#id386373">Exercises</a></span></dt><dd><dl><dt><span class="sect2"><a href="primer.html#id386486">Single-Machine Broadcast Activity</a></span></dt><dt><span class="sect2"><a href="primer.html#secondmachine">Second Machine Startup Broadcast Interaction</a></span></dt><dt><span class="sect2"><a href="primer.html#id387580">Simple Windows Client Connection Characteristics</a></span></dt><dt><span class="sect2"><a href="primer.html#id388041">Windows 200x/XP Client Interaction with Samba-3</a></span></dt><dt><span class="sect2"><a href="primer.html#id388566">Conclusions to Exercises</a></span></dt></dl></dd><dt><span class="sect1"><a href="primer.html#chap01conc">Dissection and Discussion</a></span></dt><dd><dl><dt><span class="sect2"><a href="primer.html#id388668">Technical Issues</a></span></dt></dl></dd><dt><span class="sect1"><a href="primer.html#chap01qa">Questions and Answers</a></span></dt></dl></div><p> + You are about to use the equivalent of a microscope to look at the information + that runs through the veins of a Windows network. We do more to observe the information than + to interrogate it. When you are done with this primer, you should have a good understanding + of the types of information that flow over the network. Do not worry, this is not + a biology lesson. We won't lose you in unnecessary detail. Think to yourself, “<span class="quote">This + is easy,</span>” then tackle each exercise without fear. + </p><p> + Samba can be configured with a minimum of complexity. Simplicity should be mastered + before you get too deeply into complexities. Let's get moving: we have work to do. + </p><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id386080"></a>Requirements and Notes</h2></div></div></div><p> + Successful completion of this primer requires two Microsoft Windows 9x/Me Workstations + as well as two Microsoft Windows XP Professional Workstations, each equipped with an Ethernet + card connected using a hub. Also required is one additional server (either Windows + NT4 Server, Windows 2000 Server, or a Samba-3 on UNIX/Linux server) running a network + sniffer and analysis application (ethereal is a good choice). All work should be undertaken + on a quiet network where there is no other traffic. It is best to use a dedicated hub + with only the machines under test connected at the time of the exercises. + </p><p><a class="indexterm" name="id386095"></a> + Ethereal has become the network protocol analyzer of choice for many network administrators. + You may find more information regarding this tool from the + <a href="http://www.ethereal.com" target="_top">Ethereal</a> Web site. Ethereal installation + files for Windows may be obtained from the Ethereal Web site. Ethereal is provided with + SUSE and Red Hat Linux distributions, as well as with many other Linux distributions. It may + not be installed on your system by default. If it is not installed, you may also need + to install the <code class="literal">libpcap </code> software before you can install or use Ethereal. + Please refer to the instructions for your operating system or to the Ethereal Web site + for information regarding the installation and operation of Ethereal. + </p><p> + To obtain <code class="literal">ethereal</code> for your system, please visit the Ethereal + <a href="http://www.ethereal.com/download.html#binaries" target="_top">download site</a>. + </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p> + The successful completion of this chapter requires that you capture network traffic + using <code class="literal">Ethereal</code>. It is recommended that you use a hub, not an + Ethernet switch. It is necessary for the device used to act as a repeater, not as a + filter. Ethernet switches may filter out traffic that is not directed at the machine + that is used to monitor traffic; this would not allow you to complete the projects. + </p></div><p> + <a class="indexterm" name="id386154"></a> + Do not worry too much if you do not have access to all this equipment; network captures + from the exercises are provided on the enclosed CD-ROM. This makes it possible to dive directly + into the analytical part of the exercises if you so desire. + </p><p><a class="indexterm" name="id386168"></a><a class="indexterm" name="id386179"></a> + Please do not be alarmed at the use of a high-powered analysis tool (Ethereal) in this + primer. We expose you only to a minimum of detail necessary to complete + the exercises. If you choose to use any other network sniffer and protocol + analysis tool, be advised that it may not allow you to examine the contents of + recently added security protocols used by Windows 200x/XP. + </p><p> + You could just skim through the exercises and try to absorb the key points made. + The exercises provide all the information necessary to convince the die-hard network + engineer. You possibly do not require so much convincing and may just want to move on, + in which case you should at least read <a href="primer.html#chap01conc" title="Dissection and Discussion">???</a>. + </p><p> + <a href="primer.html#chap01qa" title="Questions and Answers">???</a> also provides useful information + that may help you to avoid significantly time-consuming networking problems. + </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id386216"></a>Introduction</h2></div></div></div><p> + The purpose of this chapter is to create familiarity with key aspects of Microsoft Windows + network computing. If you want a solid technical grounding, do not gloss over these exercises. + The points covered are recurrent issues on the Samba mailing lists. + </p><p><a class="indexterm" name="id386228"></a> + You can see from these exercises that Windows networking involves quite a lot of network + broadcast traffic. You can look into the contents of some packets, but only to see + some particular information that the Windows client sends to a server in the course of + establishing a network connection. + </p><p> + To many people, browsing is everything that happens when one uses Microsoft Internet Explorer. + It is only when you start looking at network traffic and noting the protocols + and types of information that are used that you can begin to appreciate the complexities of + Windows networking and, more importantly, what needs to be configured so that it can work. + Detailed information regarding browsing is provided in the recommended + preparatory reading. + </p><p> + Recommended preparatory reading: <span class="emphasis"><em>The Official Samba-3 HOWTO and Reference Guide, Second + Edition</em></span> (TOSHARG2) Chapter 9, “<span class="quote">Network Browsing,</span>” and Chapter 3, + “<span class="quote">Server Types and Security Modes.</span>” + </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id386266"></a>Assignment Tasks</h3></div></div></div><p><a class="indexterm" name="id386273"></a> + You are about to witness how Microsoft Windows computer networking functions. The + exercises step through identification of how a client machine establishes a + connection to a remote Windows server. You observe how Windows machines find + each other (i.e., how browsing works) and how the two key types of user identification + (share mode security and user mode security) are affected. + </p><p><a class="indexterm" name="id386287"></a> + The networking protocols used by MS Windows networking when working with Samba + use TCP/IP as the transport protocol. The protocols that are specific to Windows + networking are encapsulated in TCP/IP. The network analyzer we use (Ethereal) + is able to show you the contents of the TCP/IP packets (or messages). + </p><div class="procedure"><a name="chap01tasks"></a><p class="title"><b>Procedure 16.1. Diagnostic Tasks</b></p><ol type="1"><li><p><a class="indexterm" name="id386318"></a><a class="indexterm" name="id386329"></a><a class="indexterm" name="id386337"></a> + Examine network traces to witness SMB broadcasts, host announcements, + and name resolution processes. + </p></li><li><p> + Examine network traces to witness how share mode security functions. + </p></li><li><p> + Examine network traces to witness the use of user mode security. + </p></li><li><p> + Review traces of network logons for a Windows 9x/Me client as well as + a domain logon for a Windows XP Professional client. + </p></li></ol></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id386373"></a>Exercises</h2></div></div></div><p> + <a class="indexterm" name="id386381"></a> + You are embarking on a course of discovery. The first part of the exercise requires + two MS Windows 9x/Me systems. We called one machine <code class="constant">WINEPRESSME</code> and the + other <code class="constant">MILGATE98</code>. Each needs an IP address; we used <code class="literal">10.1.1.10</code> + and <code class="literal">10.1.1.11</code>. The test machines need to be networked via a <span class="emphasis"><em>hub</em></span>. A UNIX/Linux + machine is required to run <code class="literal">Ethereal</code> to enable the network activity to be captured. + It is important that the machine from which network activity is captured must not interfere with + the operation of the Windows workstations. It is helpful for this machine to be passive (does not + send broadcast information) to the network. + </p><p> + For these exercises, our test environment consisted of a SUSE 9.2 Professional Linux Workstation running + VMWare 4.5. The following VMWare images were prepared: + </p><div class="itemizedlist"><ul type="disc"><li><p>Windows 98 name: MILGATE98</p></li><li><p>Windows Me name: WINEPRESSME</p></li><li><p>Windows XP Professional name: LightrayXP</p></li><li><p>Samba-3.0.20 running on a SUSE Enterprise Linux 9</p></li></ul></div><p> + Choose a workgroup name (MIDEARTH) for each exercise. + </p><p> + <a class="indexterm" name="id386463"></a> + The network captures provided on the CD-ROM included with this book were captured using <code class="constant">Ethereal</code> + version <code class="literal">0.10.6</code>. A later version suffices without problems, but an earlier version may not + expose all the information needed. Each capture file has been decoded and listed as a trace file. A summary of all + packets has also been included. This makes it possible for you to do all the studying you like without the need to + perform the time-consuming equipment configuration and test work. This is a good time to point out that the value + that can be derived from this book really does warrant your taking sufficient time to practice each exercise with + care and attention to detail. + </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id386486"></a>Single-Machine Broadcast Activity</h3></div></div></div><p> + In this section, we start a single Windows 9x/Me machine, then monitor network activity for 30 minutes. + </p><div class="procedure"><a name="id386496"></a><p class="title"><b>Procedure 16.2. Monitoring Windows 9x Steps</b></p><ol type="1"><li><p> + Start the machine from which network activity will be monitored (using <code class="literal">ethereal</code>). + Launch <code class="literal">ethereal</code>, click + <span class="guimenu">Capture</span> → <span class="guimenuitem">Start</span>. + </p><p> + Click the following: + </p><div class="orderedlist"><ol type="1"><li><p>Update list of packets in real time</p></li><li><p>Automatic scrolling in live capture</p></li><li><p>Enable MAC name resolution</p></li><li><p>Enable network name resolution</p></li><li><p>Enable transport name resolution</p></li></ol></div><p> + Click <span class="guibutton">OK</span>. + </p></li><li><p> + Start the Windows 9x/Me machine to be monitored. Let it run for a full 30 minutes. While monitoring, + do not press any keyboard keys, do not click any on-screen icons or menus, and do not answer any dialog boxes. + </p></li><li><p> + At the conclusion of 30 minutes, stop the capture. Save the capture to a file so you can go back to it later. + Leave this machine running in preparation for the task in <a href="primer.html#secondmachine" title="Second Machine Startup Broadcast Interaction">???</a>. + </p></li><li><p> + Analyze the capture. Identify each discrete message type that was captured. Note what transport protocol + was used. Identify the timing between messages of identical types. + </p></li></ol></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id386612"></a>Findings</h4></div></div></div><p> + The summary of the first 10 minutes of the packet capture should look like <a href="primer.html#pktcap01" title="Figure 16.1. Windows Me Broadcasts The First 10 Minutes">???</a>. + A screenshot of a later stage of the same capture is shown in <a href="primer.html#pktcap02" title="Figure 16.2. Windows Me Later Broadcast Sample">???</a>. + </p><div class="figure"><a name="pktcap01"></a><p class="title"><b>Figure 16.1. Windows Me Broadcasts The First 10 Minutes</b></p><div class="figure-contents"><div class="mediaobject"><img src="images/WINREPRESSME-Capture.png" width="216" alt="Windows Me Broadcasts The First 10 Minutes"></div></div></div><br class="figure-break"><div class="figure"><a name="pktcap02"></a><p class="title"><b>Figure 16.2. Windows Me Later Broadcast Sample</b></p><div class="figure-contents"><div class="mediaobject"><img src="images/WINREPRESSME-Capture2.png" width="226.8" alt="Windows Me Later Broadcast Sample"></div></div></div><br class="figure-break"><p><a class="indexterm" name="id386725"></a><a class="indexterm" name="id386736"></a> + Broadcast messages observed are shown in <a href="primer.html#capsstats01" title="Table 16.1. Windows Me Startup Broadcast Capture Statistics">???</a>. + Actual observations vary a little, but not by much. + Early in the startup process, the Windows Me machine broadcasts its name for two reasons: + first to ensure that its name would not result in a name clash, and second to establish its + presence with the Local Master Browser (LMB). + </p><div class="table"><a name="capsstats01"></a><p class="title"><b>Table 16.1. Windows Me Startup Broadcast Capture Statistics</b></p><div class="table-contents"><table summary="Windows Me Startup Broadcast Capture Statistics" border="1"><colgroup><col align="left"><col align="center"><col align="center"><col align="left"></colgroup><thead><tr><th align="left">Message</th><th align="center">Type</th><th align="center">Num</th><th align="left">Notes</th></tr></thead><tbody><tr><td align="left">WINEPRESSME<00></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.6 sec apart</td></tr><tr><td align="left">WINEPRESSME<03></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.6 sec apart</td></tr><tr><td align="left">WINEPRESSME<20></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.75 sec apart</td></tr><tr><td align="left">MIDEARTH<00></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.75 sec apart</td></tr><tr><td align="left">MIDEARTH<1d></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.75 sec apart</td></tr><tr><td align="left">MIDEARTH<1e></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.75 sec apart</td></tr><tr><td align="left">MIDEARTH<1b></td><td align="center">Qry</td><td align="center">84</td><td align="left">300 sec apart at stable operation</td></tr><tr><td align="left">__MSBROWSE__</td><td align="center">Reg</td><td align="center">8</td><td align="left">Registered after winning election to Browse Master</td></tr><tr><td align="left">JHT<03></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 x 2. This is the name of the user that logged onto Windows</td></tr><tr><td align="left">Host Announcement WINEPRESSME</td><td align="center">Ann</td><td align="center">2</td><td align="left">Observed at 10 sec</td></tr><tr><td align="left">Domain/Workgroup Announcement MIDEARTH</td><td align="center">Ann</td><td align="center">18</td><td align="left">300 sec apart at stable operation</td></tr><tr><td align="left">Local Master Announcement WINEPRESSME</td><td align="center">Ann</td><td align="center">18</td><td align="left">300 sec apart at stable operation</td></tr><tr><td align="left">Get Backup List Request</td><td align="center">Qry</td><td align="center">12</td><td align="left">6 x 2 early in startup, 0.5 sec apart</td></tr><tr><td align="left">Browser Election Request</td><td align="center">Ann</td><td align="center">10</td><td align="left">5 x 2 early in startup</td></tr><tr><td align="left">Request Announcement WINEPRESSME</td><td align="center">Ann</td><td align="center">4</td><td align="left">Early in startup</td></tr></tbody></table></div></div><br class="table-break"><p><a class="indexterm" name="id387071"></a><a class="indexterm" name="id387079"></a> + From the packet trace, it should be noted that no messages were propagated over TCP/IP; + all messages employed UDP/IP. When steady-state operation has been achieved, there is a cycle + of various announcements, re-election of a browse master, and name queries. These create + the symphony of announcements by which network browsing is made possible. + </p><p><a class="indexterm" name="id387093"></a> + For detailed information regarding the precise behavior of the CIFS/SMB protocols, + refer to the book “<span class="quote">Implementing CIFS: The Common Internet File System,</span>” + by Christopher Hertel, (Prentice Hall PTR, ISBN: 013047116X). + </p></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="secondmachine"></a>Second Machine Startup Broadcast Interaction</h3></div></div></div><p> + At this time, the machine you used to capture the single-system startup trace should still be running. + The objective of this task is to identify the interaction of two machines in respect to broadcast activity. + </p><div class="procedure"><a name="id387125"></a><p class="title"><b>Procedure 16.3. Monitoring of Second Machine Activity</b></p><ol type="1"><li><p> + On the machine from which network activity will be monitored (using <code class="literal">ethereal</code>), + launch <code class="literal">ethereal</code> and click + <span class="guimenu">Capture</span> → <span class="guimenuitem">Start</span>. + </p><p> + Click: + </p><div class="orderedlist"><ol type="1"><li><p>Update list of packets in real time</p></li><li><p>Automatic scrolling in live capture</p></li><li><p>Enable MAC name resolution</p></li><li><p>Enable network name resolution</p></li><li><p>Enable transport name resolution</p></li></ol></div><p> + Click <span class="guibutton">OK</span>. + </p></li><li><p> + Start the second Windows 9x/Me machine. Let it run for 15 to 20 minutes. While monitoring, do not press + any keyboard keys, do not click any on-screen icons or menus, and do not answer any dialog boxes. + </p></li><li><p> + At the conclusion of the capture time, stop the capture. Be sure to save the captured data so you + can examine the network data capture again at a later date should that be necessary. + </p></li><li><p> + Analyze the capture trace, taking note of the transport protocols used, the types of messages observed, + and what interaction took place between the two machines. Leave both machines running for the next task. + </p></li></ol></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id387234"></a>Findings</h4></div></div></div><p> + <a href="primer.html#capsstats02" title="Table 16.2. Second Machine (Windows 98) Capture Statistics">???</a> summarizes capture statistics observed. As in the previous case, + all announcements used UDP/IP broadcasts. Also, as was observed with the last example, the second + Windows 9x/Me machine broadcasts its name on startup to ensure that there exists no name clash + (i.e., the name is already registered by another machine) on the network segment. Those wishing + to explore the inner details of the precise mechanism of how this functions should refer to + “<span class="quote">Implementing CIFS: The Common Internet File System.</span>” + </p><div class="table"><a name="capsstats02"></a><p class="title"><b>Table 16.2. Second Machine (Windows 98) Capture Statistics</b></p><div class="table-contents"><table summary="Second Machine (Windows 98) Capture Statistics" border="1"><colgroup><col align="left"><col align="center"><col align="center"><col align="left"></colgroup><thead><tr><th align="left">Message</th><th align="center">Type</th><th align="center">Num</th><th align="left">Notes</th></tr></thead><tbody><tr><td align="left">MILGATE98<00></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.6 sec apart</td></tr><tr><td align="left">MILGATE98<03></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.6 sec apart</td></tr><tr><td align="left">MILGATE98<20></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.75 sec apart</td></tr><tr><td align="left">MIDEARTH<00></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.75 sec apart</td></tr><tr><td align="left">MIDEARTH<1d></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.75 sec apart</td></tr><tr><td align="left">MIDEARTH<1e></td><td align="center">Reg</td><td align="center">8</td><td align="left">4 lots of 2, 0.75 sec apart</td></tr><tr><td align="left">MIDEARTH<1b></td><td align="center">Qry</td><td align="center">18</td><td align="left">900 sec apart at stable operation</td></tr><tr><td align="left">JHT<03></td><td align="center">Reg</td><td align="center">2</td><td align="left">This is the name of the user that logged onto Windows</td></tr><tr><td align="left">Host Announcement MILGATE98</td><td align="center">Ann</td><td align="center">14</td><td align="left">Every 120 sec</td></tr><tr><td align="left">Domain/Workgroup Announcement MIDEARTH</td><td align="center">Ann</td><td align="center">6</td><td align="left">900 sec apart at stable operation</td></tr><tr><td align="left">Local Master Announcement WINEPRESSME</td><td align="center">Ann</td><td align="center">6</td><td align="left">Insufficient detail to determine frequency</td></tr></tbody></table></div></div><br class="table-break"><p> + <a class="indexterm" name="id387506"></a> + <a class="indexterm" name="id387513"></a> + <a class="indexterm" name="id387520"></a> + Observation of the contents of Host Announcements, Domain/Workgroup Announcements, + and Local Master Announcements is instructive. These messages convey a significant + level of detail regarding the nature of each machine that is on the network. An example + dissection of a Host Announcement is given in <a href="primer.html#hostannounce" title="Figure 16.3. Typical Windows 9x/Me Host Announcement">???</a>. + </p><div class="figure"><a name="hostannounce"></a><p class="title"><b>Figure 16.3. Typical Windows 9x/Me Host Announcement</b></p><div class="figure-contents"><div class="mediaobject"><img src="images/HostAnnouncment.png" width="221.4" alt="Typical Windows 9x/Me Host Announcement"></div></div></div><br class="figure-break"></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id387580"></a>Simple Windows Client Connection Characteristics</h3></div></div></div><p> + The purpose of this exercise is to discover how Microsoft Windows clients create (establish) + connections with remote servers. The methodology involves analysis of a key aspect of how + Windows clients access remote servers: the session setup protocol. + </p><div class="procedure"><a name="id387592"></a><p class="title"><b>Procedure 16.4. Client Connection Exploration Steps</b></p><ol type="1"><li><p> + Configure a Windows 9x/Me machine (MILGATE98) with a share called <code class="constant">Stuff</code>. + Create a <em class="parameter"><code>Full Access</code></em> control password on this share. + </p></li><li><p> + Configure another Windows 9x/Me machine (WINEPRESSME) as a client. Make sure that it exports + no shared resources. + </p></li><li><p> + Start both Windows 9x/Me machines and allow them to stabilize for 10 minutes. Log on to both + machines using a user name (JHT) of your choice. Wait approximately 2 minutes before proceeding. + </p></li><li><p> + Start ethereal (or the network sniffer of your choice). + </p></li><li><p> + From the WINEPRESSME machine, right-click <span class="guimenu">Network Neighborhood</span>, select + <span class="guimenuitem">Explore</span>, select + <span class="guimenuitem">My Network Places</span> → <span class="guimenuitem">Entire Network</span> → <span class="guimenuitem">MIDEARTH</span> → <span class="guimenuitem">MILGATE98</span> → <span class="guimenuitem">Stuff</span>. + Enter the password you set for the <code class="constant">Full Control</code> mode for the + <code class="constant">Stuff</code> share. + </p></li><li><p> + When the share called <code class="constant">Stuff</code> is being displayed, stop the capture. + Save the captured data in case it is needed for later analysis. + </p></li><li><p> + <a class="indexterm" name="id387716"></a> + From the top of the packets captured, scan down to locate the first packet that has + interpreted as <code class="constant">Session Setup AndX, User: anonymous; Tree Connect AndX, + Path: \\MILGATE98\IPC$</code>. + </p></li><li><p><a class="indexterm" name="id387733"></a><a class="indexterm" name="id387741"></a> + In the dissection (analysis) panel, expand the <code class="constant">SMB, Session Setup AndX Request, + and Tree Connect AndX Request</code>. Examine both operations. Identify the name of + the user Account and what password was used. The Account name should be empty. + This is a <code class="constant">NULL</code> session setup packet. + </p></li><li><p> + Return to the packet capture sequence. There will be a number of packets that have been + decoded of the type <code class="constant">Session Setup AndX</code>. Locate the last such packet + that was targeted at the <code class="constant">\\MILGATE98\IPC$</code> service. + </p></li><li><p> + <a class="indexterm" name="id387782"></a> + <a class="indexterm" name="id387788"></a> + Dissect this packet as per the previous one. This packet should have a password length + of 24 (characters) and should have a password field, the contents of which is a + long hexadecimal number. Observe the name in the Account field. This is a User Mode + session setup packet. + </p></li></ol></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id387800"></a>Findings and Comments</h4></div></div></div><p> + <a class="indexterm" name="id387808"></a> + The <code class="constant">IPC$</code> share serves a vital purpose<sup>[<a name="id387819" href="#ftn.id387819">15</a>]</sup> + in SMB/CIFS-based networking. A Windows client connects to this resource to obtain the list of + resources that are available on the server. The server responds with the shares and print queues that + are available. In most but not all cases, the connection is made with a <code class="constant">NULL</code> + username and a <code class="constant">NULL</code> password. + </p><p> + <a class="indexterm" name="id387836"></a> + The two packets examined are material evidence of how Windows clients may + interoperate with Samba. Samba requires every connection setup to be authenticated using + valid UNIX account credentials (UID/GID). This means that even a <code class="constant">NULL</code> + session setup can be established only by automatically mapping it to a valid UNIX + account. + </p><p> + <a class="indexterm" name="id387853"></a><a class="indexterm" name="id387859"></a> + <a class="indexterm" name="id387868"></a> + Samba has a special name for the <code class="constant">NULL</code>, or empty, user account: + it calls it the <a class="indexterm" name="id387879"></a>guest account. The + default value of this parameter is <code class="constant">nobody</code>; however, this can be + changed to map the function of the guest account to any other UNIX identity. Some + UNIX administrators prefer to map this account to the system default anonymous + FTP account. A sample NULL Session Setup AndX packet dissection is shown in + <a href="primer.html#nullconnect" title="Figure 16.4. Typical Windows 9x/Me NULL SessionSetUp AndX Request">???</a>. + </p><div class="figure"><a name="nullconnect"></a><p class="title"><b>Figure 16.4. Typical Windows 9x/Me NULL SessionSetUp AndX Request</b></p><div class="figure-contents"><div class="mediaobject"><img src="images/NullConnect.png" width="221.4" alt="Typical Windows 9x/Me NULL SessionSetUp AndX Request"></div></div></div><br class="figure-break"><p> + <a class="indexterm" name="id387943"></a> + <a class="indexterm" name="id387950"></a> + <a class="indexterm" name="id387956"></a> + When a UNIX/Linux system does not have a <code class="constant">nobody</code> user account + (<code class="filename">/etc/passwd</code>), the operation of the <code class="constant">NULL</code> + account cannot validate and thus connections that utilize the guest account + fail. This breaks all ability to browse the Samba server and is a common + problem reported on the Samba mailing list. A sample User Mode session setup AndX + is shown in <a href="primer.html#userconnect" title="Figure 16.5. Typical Windows 9x/Me User SessionSetUp AndX Request">???</a>. + </p><div class="figure"><a name="userconnect"></a><p class="title"><b>Figure 16.5. Typical Windows 9x/Me User SessionSetUp AndX Request</b></p><div class="figure-contents"><div class="mediaobject"><img src="images/UserConnect.png" width="221.4" alt="Typical Windows 9x/Me User SessionSetUp AndX Request"></div></div></div><br class="figure-break"><p> + <a class="indexterm" name="id388029"></a> + The User Mode connection packet contains the account name and the domain name. + The password is provided in Microsoft encrypted form, and its length is shown + as 24 characters. This is the length of Microsoft encrypted passwords. + </p></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id388041"></a>Windows 200x/XP Client Interaction with Samba-3</h3></div></div></div><p> + By now you may be asking, “<span class="quote">Why did you choose to work with Windows 9x/Me?</span>” + </p><p> + First, we want to demonstrate the simple case. This book is not intended to be a detailed treatise + on the Windows networking protocols, but rather to provide prescriptive guidance for deployment of Samba. + Second, by starting out with the simple protocol, it can be demonstrated that the more complex case mostly + follows the same principles. + </p><p> + The following exercise demonstrates the case that even MS Windows XP Professional with up-to-date service + updates also uses the <code class="constant">NULL</code> account, as well as user accounts. Simply follow the procedure + to complete this exercise. + </p><p> + To complete this exercise, you need a Windows XP Professional client that has been configured as + a domain member of either a Samba-controlled domain or a Windows NT4 or 200x Active Directory domain. + Here we do not provide details for how to configure this, as full coverage is provided earlier in this book. + </p><div class="procedure"><a name="id388076"></a><p class="title"><b>Procedure 16.5. Steps to Explore Windows XP Pro Connection Set-up</b></p><ol type="1"><li><p> + Start your domain controller. Also, start the ethereal monitoring machine, launch ethereal, + and then wait for the next step to complete. + </p></li><li><p> + Start the Windows XP Client and wait 5 minutes before proceeding. + </p></li><li><p> + On the machine from which network activity will be monitored (using <code class="literal">ethereal</code>), + launch <code class="literal">ethereal</code> and click + <span class="guimenu">Capture</span> → <span class="guimenuitem">Start</span>. + </p><p> + Click: + </p><div class="orderedlist"><ol type="1"><li><p>Update list of packets in real time</p></li><li><p>Automatic scrolling in live capture</p></li><li><p>Enable MAC name resolution</p></li><li><p>Enable network name resolution</p></li><li><p>Enable transport name resolution</p></li></ol></div><p> + Click <span class="guibutton">OK</span>. + </p></li><li><p> + On the Windows XP Professional client, press <span class="guimenu">Ctrl-Alt-Delete</span> to bring + up the domain logon screen. Log in using valid credentials for a domain user account. + </p></li><li><p> + Now proceed to connect to the domain controller as follows: + <span class="guimenu">Start</span> → <span class="guimenuitem">(right-click) My Network Places</span> → <span class="guimenuitem">Explore</span> → <span class="guimenuitem">{Left Panel} [+] Entire Network</span> → <span class="guimenuitem">{Left Panel} [+] Microsoft Windows Network</span> → <span class="guimenuitem">{Left Panel} [+] Midearth</span> → <span class="guimenuitem">{Left Panel} [+] Frodo</span> → <span class="guimenuitem">{Left Panel} [+] data</span>. Close the explorer window. + </p><p> + In this step, our domain name is <code class="constant">Midearth</code>, the domain controller is called + <code class="constant">Frodo</code>, and we have connected to a share called <code class="constant">data</code>. + </p></li><li><p> + Stop the capture on the <code class="literal">ethereal</code> monitoring machine. Be sure to save the captured data + to a file so that you can refer to it again later. + </p></li><li><p> + If desired, the Windows XP Professional client and the domain controller are no longer needed for exercises + in this chapter. + </p></li><li><p> + <a class="indexterm" name="id388290"></a> + <a class="indexterm" name="id388296"></a> + From the top of the packets captured, scan down to locate the first packet that has + interpreted as <code class="constant">Session Setup AndX Request, NTLMSSP_AUTH</code>. + </p></li><li><p> + <a class="indexterm" name="id388315"></a> + <a class="indexterm" name="id388322"></a> + <a class="indexterm" name="id388328"></a> + In the dissection (analysis) panel, expand the <code class="constant">SMB, Session Setup AndX Request</code>. + Expand the packet decode information, beginning at the <code class="constant">Security Blob:</code> + entry. Expand the <code class="constant">GSS-API -> SPNEGO -> netTokenTarg -> responseToken -> NTLMSSP</code> + keys. This should reveal that this is a <code class="constant">NULL</code> session setup packet. + The <code class="constant">User name: NULL</code> so indicates. An example decode is shown in + <a href="primer.html#XPCap01" title="Figure 16.6. Typical Windows XP NULL Session Setup AndX Request">???</a>. + </p></li><li><p> + Return to the packet capture sequence. There will be a number of packets that have been + decoded of the type <code class="constant">Session Setup AndX Request</code>. Click the last such packet that + has been decoded as <code class="constant">Session Setup AndX Request, NTLMSSP_AUTH</code>. + </p></li><li><p> + <a class="indexterm" name="id388386"></a> + In the dissection (analysis) panel, expand the <code class="constant">SMB, Session Setup AndX Request</code>. + Expand the packet decode information, beginning at the <code class="constant">Security Blob:</code> + entry. Expand the <code class="constant">GSS-API -> SPNEGO -> netTokenTarg -> responseToken -> NTLMSSP</code> + keys. This should reveal that this is a <code class="constant">User Mode</code> session setup packet. + The <code class="constant">User name: jht</code> so indicates. An example decode is shown in + <a href="primer.html#XPCap02" title="Figure 16.7. Typical Windows XP User Session Setup AndX Request">???</a>. In this case the user name was <code class="constant">jht</code>. This packet + decode includes the <code class="constant">Lan Manager Response:</code> and the <code class="constant">NTLM Response:</code>. + The values of these two parameters are the Microsoft encrypted password hashes: respectively, the LanMan + password and then the NT (case-preserving) password hash. + </p></li><li><p> + <a class="indexterm" name="id388440"></a> + <a class="indexterm" name="id388447"></a> + The passwords are 24-character hexadecimal numbers. This packet confirms that this is a User Mode + session setup packet. + </p></li></ol></div><div class="figure"><a name="XPCap01"></a><p class="title"><b>Figure 16.6. Typical Windows XP NULL Session Setup AndX Request</b></p><div class="figure-contents"><div class="mediaobject"><img src="images/WindowsXP-NullConnection.png" width="270" alt="Typical Windows XP NULL Session Setup AndX Request"></div></div></div><br class="figure-break"><div class="figure"><a name="XPCap02"></a><p class="title"><b>Figure 16.7. Typical Windows XP User Session Setup AndX Request</b></p><div class="figure-contents"><div class="mediaobject"><img src="images/WindowsXP-UserConnection.png" width="270" alt="Typical Windows XP User Session Setup AndX Request"></div></div></div><br class="figure-break"><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id388539"></a>Discussion</h4></div></div></div><p><a class="indexterm" name="id388546"></a> + This exercise demonstrates that, while the specific protocol for the Session Setup AndX is handled + in a more sophisticated manner by recent MS Windows clients, the underlying rules or principles + remain the same. Thus it is demonstrated that MS Windows XP Professional clients still use a + <code class="constant">NULL-Session</code> connection to query and locate resources on an advanced network + technology server (one using Windows NT4/200x or Samba). It also demonstrates that an authenticated + connection must be made before resources can be used. + </p></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id388566"></a>Conclusions to Exercises</h3></div></div></div><p> + In summary, the following points have been established in this chapter: + </p><div class="itemizedlist"><ul type="disc"><li><p> + When NetBIOS over TCP/IP protocols are enabled, MS Windows networking employs broadcast-oriented messaging protocols to provide knowledge of network services. + </p></li><li><p> + Network browsing protocols query information stored on browse masters that manage + information provided by NetBIOS Name Registrations and by way of ongoing host + announcements and workgroup announcements. + </p></li><li><p> + All Samba servers must be configured with a mechanism for mapping the <code class="constant">NULL-Session</code> + to a valid but nonprivileged UNIX system account. + </p></li><li><p> + The use of Microsoft encrypted passwords is built right into the fabric of Windows + networking operations. Such passwords cannot be provided from the UNIX <code class="filename">/etc/passwd</code> + database and thus must be stored elsewhere on the UNIX system in a manner that Samba can + use. Samba-2.x permitted such encrypted passwords to be stored in the <code class="constant">smbpasswd</code> + file or in an LDAP database. Samba-3 permits use of multiple <em class="parameter"><code>passdb backend</code></em> + databases in concurrent deployment. Refer to <span class="emphasis"><em>TOSHARG2</em></span>, Chapter 10, “<span class="quote">Account Information Databases.</span>” + </p></li></ul></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="chap01conc"></a>Dissection and Discussion</h2></div></div></div><p> + <a class="indexterm" name="id388644"></a> + The exercises demonstrate the use of the <code class="constant">guest</code> account, the way that + MS Windows clients and servers resolve computer names to a TCP/IP address, and how connections + between a client and a server are established. + </p><p> + Those wishing background information regarding NetBIOS name types should refer to + the Microsoft knowledgebase article + <a href="http://support.microsoft.com/support/kb/articles/Q102/78/8.asp" target="_top">Q102878.</a> + </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id388668"></a>Technical Issues</h3></div></div></div><p> + <a class="indexterm" name="id388676"></a> + Network browsing involves SMB broadcast announcements, SMB enumeration requests, + connections to the <code class="constant">IPC$</code> share, share enumerations, and SMB connection + setup processes. The use of anonymous connections to a Samba server involve the use of + the <em class="parameter"><code>guest account</code></em> that must map to a valid UNIX UID. + </p></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="chap01qa"></a>Questions and Answers</h2></div></div></div><p> + The questions and answers given in this section are designed to highlight important aspects of Microsoft + Windows networking. + </p><div class="qandaset"><dl><dt> <a href="primer.html#id388717"> + What is the significance of the MIDEARTH<1b> type query? + </a></dt><dt> <a href="primer.html#id388760"> + What is the significance of the MIDEARTH<1d> type name registration? + </a></dt><dt> <a href="primer.html#id388826"> + What is the role and significance of the <01><02>__MSBROWSE__<02><01> + name registration? + </a></dt><dt> <a href="primer.html#id388854"> + What is the significance of the MIDEARTH<1e> type name registration? + </a></dt><dt> <a href="primer.html#id388881"> + + What is the significance of the guest account in smb.conf? + </a></dt><dt> <a href="primer.html#id388948"> + Is it possible to reduce network broadcast activity with Samba-3? + </a></dt><dt> <a href="primer.html#id389046"> + Can I just use plain-text passwords with Samba? + </a></dt><dt> <a href="primer.html#id389122"> + What parameter in the smb.conf file is used to enable the use of encrypted passwords? + </a></dt><dt> <a href="primer.html#id389161"> + Is it necessary to specify encrypt passwords = Yes + when Samba-3 is configured as a domain member? + </a></dt><dt> <a href="primer.html#id389185"> + Is it necessary to specify a guest account when Samba-3 is configured + as a domain member server? + </a></dt></dl><table border="0" summary="Q and A Set"><col align="left" width="1%"><tbody><tr class="question"><td align="left" valign="top"><a name="id388717"></a><a name="id388720"></a></td><td align="left" valign="top"><p> + What is the significance of the MIDEARTH<1b> type query? + </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p> + <a class="indexterm" name="id388731"></a> + <a class="indexterm" name="id388740"></a> + This is a broadcast announcement by which the Windows machine is attempting to + locate a Domain Master Browser (DMB) in the event that it might exist on the network. + Refer to <span class="emphasis"><em>TOSHARG2,</em></span> Chapter 9, Section 9.7, “<span class="quote">Technical Overview of Browsing,</span>” + for details regarding the function of the DMB and its role in network browsing. + </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id388760"></a><a name="id388762"></a></td><td align="left" valign="top"><p> + What is the significance of the MIDEARTH<1d> type name registration? + </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p> + <a class="indexterm" name="id388773"></a> + <a class="indexterm" name="id388782"></a> + This name registration records the machine IP addresses of the LMBs. + Network clients can query this name type to obtain a list of browser servers from the + master browser. + </p><p> + The LMB is responsible for monitoring all host announcements on the local network and for + collating the information contained within them. Using this information, it can provide answers to other Windows + network clients that request information such as: + </p><div class="itemizedlist"><ul type="disc"><li><p> + The list of machines known to the LMB (i.e., the browse list) + </p></li><li><p> + The IP addresses of all domain controllers known for the domain + </p></li><li><p> + The IP addresses of LMBs + </p></li><li><p> + The IP address of the DMB (if one exists) + </p></li><li><p> + The IP address of the LMB on the local segment + </p></li></ul></div></td></tr><tr class="question"><td align="left" valign="top"><a name="id388826"></a><a name="id388829"></a></td><td align="left" valign="top"><p> + What is the role and significance of the <01><02>__MSBROWSE__<02><01> + name registration? + </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p> + <a class="indexterm" name="id388842"></a> + This name is registered by the browse master to broadcast and receive domain announcements. + Its scope is limited to the local network segment, or subnet. By querying this name type, + master browsers on networks that have multiple domains can find the names of master browsers + for each domain. + </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id388854"></a><a name="id388856"></a></td><td align="left" valign="top"><p> + What is the significance of the MIDEARTH<1e> type name registration? + </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p> + <a class="indexterm" name="id388868"></a> + This name is registered by all browse masters in a domain or workgroup. The registration + name type is known as the Browser Election Service. Master browsers register themselves + with this name type so that DMBs can locate them to perform cross-subnet + browse list updates. This name type is also used to initiate elections for Master Browsers. + </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id388881"></a><a name="id388883"></a></td><td align="left" valign="top"><p> + <a class="indexterm" name="id388888"></a> + What is the significance of the <em class="parameter"><code>guest account</code></em> in smb.conf? + </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p> + This parameter specifies the default UNIX account to which MS Windows networking + NULL session connections are mapped. The default name for the UNIX account used for + this mapping is called <code class="constant">nobody</code>. If the UNIX/Linux system that + is hosting Samba does not have a <code class="constant">nobody</code> account and an alternate + mapping has not been specified, network browsing will not work at all. + </p><p> + It should be noted that the <em class="parameter"><code>guest account</code></em> is essential to + Samba operation. Either the operating system must have an account called <code class="constant">nobody</code> + or there must be an entry in the <code class="filename">smb.conf</code> file with a valid UNIX account, such as + <a class="indexterm" name="id388938"></a>guest account = ftp. + </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id388948"></a><a name="id388950"></a></td><td align="left" valign="top"><p> + Is it possible to reduce network broadcast activity with Samba-3? + </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p> + <a class="indexterm" name="id388962"></a> + <a class="indexterm" name="id388968"></a> + Yes, there are two ways to do this. The first involves use of WINS (See <span class="emphasis"><em>TOSHARG2</em></span>, Chapter 9, + Section 9.5, “<span class="quote">WINS The Windows Inter-networking Name Server</span>”); the + alternate method involves disabling the use of NetBIOS over TCP/IP. This second method requires + a correctly configured DNS server (see <span class="emphasis"><em>TOSHARG2</em></span>, Chapter 9, Section 9.3, “<span class="quote">Discussion</span>”). + </p><p> + <a class="indexterm" name="id388998"></a> + <a class="indexterm" name="id389005"></a> + <a class="indexterm" name="id389014"></a> + The use of WINS reduces network broadcast traffic. The reduction is greatest when all network + clients are configured to operate in <em class="parameter"><code>Hybrid Mode</code></em>. This can be effected through + use of DHCP to set the NetBIOS node type to type 8 for all network clients. Additionally, it is + beneficial to configure Samba to use <a class="indexterm" name="id389030"></a>name resolve order = wins host cast. + </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p> + Use of SMB without NetBIOS is possible only on Windows 200x/XP Professional clients and servers, as + well as with Samba-3. + </p></div></td></tr><tr class="question"><td align="left" valign="top"><a name="id389046"></a><a name="id389048"></a></td><td align="left" valign="top"><p> + Can I just use plain-text passwords with Samba? + </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p> + Yes, you can configure Samba to use plain-text passwords, though this does create a few problems. + </p><p> + First, the use of <code class="filename">/etc/passwd</code>-based plain-text passwords requires that registry + modifications be made on all MS Windows client machines to enable plain-text passwords support. This + significantly diminishes the security of MS Windows client operation. Many network administrators + are bitterly opposed to doing this. + </p><p> + Second, Microsoft has not maintained plain-text password support since the default setting was made + disabling this. When network connections are dropped by the client, it is not possible to re-establish + the connection automatically. Users need to log off and then log on again. Plain-text password support + may interfere with recent enhancements that are part of the Microsoft move toward a more secure computing + environment. + </p><p> + Samba-3 supports Microsoft encrypted passwords. Be advised not to reintroduce plain-text password handling. + Just create user accounts by running <code class="literal">smbpasswd -a 'username'</code> + </p><p> + It is not possible to add a user to the <em class="parameter"><code>passdb backend</code></em> database unless there is + a UNIX system account for that user. On systems that run <code class="literal">winbindd</code> to access the Samba + PDC/BDC to provide Windows user and group accounts, the <em class="parameter"><code>idmap uid, idmap gid</code></em> ranges + set in the <code class="filename">smb.conf</code> file provide the local UID/GIDs needed for local identity management purposes. + </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id389122"></a><a name="id389124"></a></td><td align="left" valign="top"><p> + What parameter in the <code class="filename">smb.conf</code> file is used to enable the use of encrypted passwords? + </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p> + The parameter in the <code class="filename">smb.conf</code> file that controls this behavior is known as <em class="parameter"><code>encrypt + passwords</code></em>. The default setting for this in Samba-3 is <code class="constant">Yes (Enabled)</code>. + </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id389161"></a><a name="id389163"></a></td><td align="left" valign="top"><p> + Is it necessary to specify <a class="indexterm" name="id389168"></a>encrypt passwords = Yes + when Samba-3 is configured as a domain member? + </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p> + No. This is the default behavior. + </p></td></tr><tr class="question"><td align="left" valign="top"><a name="id389185"></a><a name="id389188"></a></td><td align="left" valign="top"><p> + Is it necessary to specify a <em class="parameter"><code>guest account</code></em> when Samba-3 is configured + as a domain member server? + </p></td></tr><tr class="answer"><td align="left" valign="top"></td><td align="left" valign="top"><p> + Yes. This is a local function on the server. The default setting is to use the UNIX account + <code class="constant">nobody</code>. If this account does not exist on the UNIX server, then it is + necessary to provide a <a class="indexterm" name="id389210"></a>guest account = an_account, + where <code class="constant">an_account</code> is a valid local UNIX user account. + </p></td></tr></tbody></table></div></div><div class="footnotes"><br><hr width="100" align="left"><div class="footnote"><p><sup>[<a name="ftn.id387819" href="#id387819">15</a>] </sup>TOSHARG2, Sect 4.5.1</p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="appendix.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="RefSection.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="gpl.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 15. A Collection of Useful Tidbits </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Appendix A. GNU General Public License</td></tr></table></div></body></html> |