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diff --git a/docs-xml/Samba3-ByExample/SBE-Appendix2.xml b/docs-xml/Samba3-ByExample/SBE-Appendix2.xml new file mode 100644 index 00000000000..51d24889f18 --- /dev/null +++ b/docs-xml/Samba3-ByExample/SBE-Appendix2.xml @@ -0,0 +1,1283 @@ +<?xml version="1.0" encoding="iso-8859-1"?> +<!DOCTYPE chapter PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc"> +<chapter id="primer"> + <title>Networking Primer</title> + + <para> + 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, <quote>This + is easy,</quote> then tackle each exercise without fear. + </para> + + <para> + 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. + </para> + +<sect1> + <title>Requirements and Notes</title> + <para> + 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 (Wireshark 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. + </para> + + <para><indexterm> + <primary>Wireshark</primary> + </indexterm> + Wireshark (formerly Ethereal) has become the network protocol analyzer of choice for many network administrators. + You may find more information regarding this tool from the + <ulink url="http://www.wireshark.org">Wireshark</ulink> Web site. Wireshark installation + files for Windows may be obtained from the Wireshark Web site. Wireshark 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 <command>libpcap</command> software before you can install or use Wireshark. + Please refer to the instructions for your operating system or to the Wireshark Web site + for information regarding the installation and operation of Wireshark. + </para> + + <para> + To obtain <command>Wireshark</command> for your system, please visit the Wireshark + <ulink url="http://www.wireshark.org/download.html">download site</ulink>. + </para> + + <note><para> + The successful completion of this chapter requires that you capture network traffic + using <command>Wireshark</command>. 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. + </para></note> + + <para> + <indexterm><primary>network</primary><secondary>captures</secondary></indexterm> + 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. + </para> + + <para><indexterm> + <primary>network</primary> + <secondary>sniffer</secondary> + </indexterm><indexterm> + <primary>protocol analysis</primary> + </indexterm> + Please do not be alarmed at the use of a high-powered analysis tool (Wireshark) 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. + </para> + + <para> + 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 <link linkend="chap01conc"/>. + </para> + + <para> + <link linkend="chap01qa"/> also provides useful information + that may help you to avoid significantly time-consuming networking problems. + </para> +</sect1> + +<sect1> + <title>Introduction</title> + + <para> + 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. + </para> + + <para><indexterm> + <primary>network</primary> + <secondary>broadcast</secondary> + </indexterm> + 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. + </para> + + <para> + 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. + </para> + + <para> + Recommended preparatory reading: <emphasis>The Official Samba-3 HOWTO and Reference Guide, Second + Edition</emphasis> (TOSHARG2) Chapter 9, <quote>Network Browsing,</quote> and Chapter 3, + <quote>Server Types and Security Modes.</quote> + </para> + + <sect2> + <title>Assignment Tasks</title> + + <para><indexterm> + <primary>browsing</primary> + </indexterm> + 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. + </para> + + <para><indexterm> + <primary>network</primary> + <secondary>analyzer</secondary> + </indexterm> + 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 (Wireshark) + is able to show you the contents of the TCP/IP packets (or messages). + </para> + + <procedure id="chap01tasks"> + <title>Diagnostic Tasks</title> + + <step><para><indexterm> + <primary>network</primary> + <secondary>trace</secondary> + </indexterm><indexterm> + <primary>host announcement</primary> + </indexterm><indexterm> + <primary>name resolution</primary> + </indexterm> + Examine network traces to witness SMB broadcasts, host announcements, + and name resolution processes. + </para></step> + + <step><para> + Examine network traces to witness how share mode security functions. + </para></step> + + <step><para> + Examine network traces to witness the use of user mode security. + </para></step> + + <step><para> + Review traces of network logons for a Windows 9x/Me client as well as + a domain logon for a Windows XP Professional client. + </para></step> + </procedure> + + </sect2> +</sect1> + +<sect1> + <title>Exercises</title> + + <para> + <indexterm><primary>wireshark</primary></indexterm> + 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 <constant>WINEPRESSME</constant> and the + other <constant>MILGATE98</constant>. Each needs an IP address; we used <literal>10.1.1.10</literal> + and <literal>10.1.1.11</literal>. The test machines need to be networked via a <emphasis>hub</emphasis>. A UNIX/Linux + machine is required to run <command>Wireshark</command> 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. + </para> + + <para> + 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: + </para> + + <itemizedlist> + <listitem><para>Windows 98 &smbmdash; name: MILGATE98</para></listitem> + <listitem><para>Windows Me &smbmdash; name: WINEPRESSME</para></listitem> + <listitem><para>Windows XP Professional &smbmdash; name: LightrayXP</para></listitem> + <listitem><para>Samba-3.0.20 running on a SUSE Enterprise Linux 9</para></listitem> + </itemizedlist> + + <para> + Choose a workgroup name (MIDEARTH) for each exercise. + </para> + + <para> + <indexterm><primary>ethereal</primary></indexterm> + The network captures provided on the CD-ROM included with this book were captured using <constant>Ethereal</constant> + version <literal>0.10.6</literal>. A later version suffices without problems (i.e. you should be using Wireshark), 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. + </para> + + <sect2> + <title>Single-Machine Broadcast Activity</title> + + <para> + In this section, we start a single Windows 9x/Me machine, then monitor network activity for 30 minutes. + </para> + + <procedure> + <title>Monitoring Windows 9x Steps</title> + + <step><para> + Start the machine from which network activity will be monitored (using <command>Wireshark</command>). + Launch <command>Wireshark</command>, click + <menuchoice> + <guimenu>Capture</guimenu> + <guimenuitem>Start</guimenuitem> + </menuchoice>. + </para> + + <para> + Click the following: + <orderedlist> + <listitem><para>Update list of packets in real time</para></listitem> + <listitem><para>Automatic scrolling in live capture</para></listitem> + <listitem><para>Enable MAC name resolution</para></listitem> + <listitem><para>Enable network name resolution</para></listitem> + <listitem><para>Enable transport name resolution</para></listitem> + </orderedlist> + Click <guibutton>OK</guibutton>. + </para></step> + + <step><para> + 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. + </para></step> + + <step><para> + 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 <link linkend="secondmachine"/>. + </para></step> + + <step><para> + 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. + </para></step> + + </procedure> + + <sect3> + <title>Findings</title> + + <para> + The summary of the first 10 minutes of the packet capture should look like <link linkend="pktcap01"/>. + A screenshot of a later stage of the same capture is shown in <link linkend="pktcap02"/>. + </para> + + <figure id="pktcap01"> + <title>Windows Me &smbmdash; Broadcasts &smbmdash; The First 10 Minutes</title> + <imagefile scale="40">WINREPRESSME-Capture</imagefile> + </figure> + + <figure id="pktcap02"> + <title>Windows Me &smbmdash; Later Broadcast Sample</title> + <imagefile scale="42">WINREPRESSME-Capture2</imagefile> + </figure> + + <para><indexterm> + <primary>Local Master Browser</primary> + <see>LMB</see> + </indexterm><indexterm> + <primary>LMB</primary> + </indexterm> + Broadcast messages observed are shown in <link linkend="capsstats01"/>. + 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). + </para> + + <table id="capsstats01"> + <title>Windows Me &smbmdash; Startup Broadcast Capture Statistics</title> + <tgroup cols="4"> + <colspec align="left" colwidth="3*"/> + <colspec align="center"/> + <colspec align="center"/> + <colspec align="left" colwidth="3*"/> + <thead> + <row> + <entry>Message</entry> + <entry>Type</entry> + <entry>Num</entry> + <entry>Notes</entry> + </row> + </thead> + <tbody> + <row> + <entry>WINEPRESSME<00></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.6 sec apart</entry> + </row> + <row> + <entry>WINEPRESSME<03></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.6 sec apart</entry> + </row> + <row> + <entry>WINEPRESSME<20></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.75 sec apart</entry> + </row> + <row> + <entry>MIDEARTH<00></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.75 sec apart</entry> + </row> + <row> + <entry>MIDEARTH<1d></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.75 sec apart</entry> + </row> + <row> + <entry>MIDEARTH<1e></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.75 sec apart</entry> + </row> + <row> + <entry>MIDEARTH<1b></entry> + <entry>Qry</entry> + <entry>84</entry> + <entry>300 sec apart at stable operation</entry> + </row> + <row> + <entry>__MSBROWSE__</entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>Registered after winning election to Browse Master</entry> + </row> + <row> + <entry>JHT<03></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 x 2. This is the name of the user that logged onto Windows</entry> + </row> + <row> + <entry>Host Announcement WINEPRESSME</entry> + <entry>Ann</entry> + <entry>2</entry> + <entry>Observed at 10 sec</entry> + </row> + <row> + <entry>Domain/Workgroup Announcement MIDEARTH</entry> + <entry>Ann</entry> + <entry>18</entry> + <entry>300 sec apart at stable operation</entry> + </row> + <row> + <entry>Local Master Announcement WINEPRESSME</entry> + <entry>Ann</entry> + <entry>18</entry> + <entry>300 sec apart at stable operation</entry> + </row> + <row> + <entry>Get Backup List Request</entry> + <entry>Qry</entry> + <entry>12</entry> + <entry>6 x 2 early in startup, 0.5 sec apart</entry> + </row> + <row> + <entry>Browser Election Request</entry> + <entry>Ann</entry> + <entry>10</entry> + <entry>5 x 2 early in startup</entry> + </row> + <row> + <entry>Request Announcement WINEPRESSME</entry> + <entry>Ann</entry> + <entry>4</entry> + <entry>Early in startup</entry> + </row> + </tbody> + </tgroup> + </table> + + <para><indexterm> + <primary>election</primary> + </indexterm><indexterm> + <primary>browse master</primary> + </indexterm> + 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. + </para> + + <para><indexterm> + <primary>CIFS</primary> + </indexterm> + For detailed information regarding the precise behavior of the CIFS/SMB protocols, + refer to the book <quote>Implementing CIFS: The Common Internet File System,</quote> + by Christopher Hertel, (Prentice Hall PTR, ISBN: 013047116X). + </para> + + </sect3> + + </sect2> + + <sect2 id="secondmachine"> + <title>Second Machine Startup Broadcast Interaction</title> + + <para> + 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. + </para> + + <procedure> + <title>Monitoring of Second Machine Activity</title> + + <step><para> + On the machine from which network activity will be monitored (using <command>Wireshark</command>), + launch <command>Wireshark</command> and click + <menuchoice> + <guimenu>Capture</guimenu> + <guimenuitem>Start</guimenuitem> + </menuchoice>. + </para> + + <para> + Click: + <orderedlist> + <listitem><para>Update list of packets in real time</para></listitem> + <listitem><para>Automatic scrolling in live capture</para></listitem> + <listitem><para>Enable MAC name resolution</para></listitem> + <listitem><para>Enable network name resolution</para></listitem> + <listitem><para>Enable transport name resolution</para></listitem> + </orderedlist> + Click <guibutton>OK</guibutton>. + </para></step> + + <step><para> + 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. + </para></step> + + <step><para> + 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. + </para></step> + + <step><para> + 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. + </para></step> + </procedure> + + <sect3> + <title>Findings</title> + + <para> + <link linkend="capsstats02"/> 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 + <quote>Implementing CIFS: The Common Internet File System.</quote> + </para> + + <table id="capsstats02"> + <title>Second Machine (Windows 98) &smbmdash; Capture Statistics</title> + <tgroup cols="4"> + <colspec align="left" colwidth="3*"/> + <colspec align="center"/> + <colspec align="center"/> + <colspec align="left" colwidth="3*"/> + <thead> + <row> + <entry>Message</entry> + <entry>Type</entry> + <entry>Num</entry> + <entry>Notes</entry> + </row> + </thead> + <tbody> + <row> + <entry>MILGATE98<00></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.6 sec apart</entry> + </row> + <row> + <entry>MILGATE98<03></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.6 sec apart</entry> + </row> + <row> + <entry>MILGATE98<20></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.75 sec apart</entry> + </row> + <row> + <entry>MIDEARTH<00></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.75 sec apart</entry> + </row> + <row> + <entry>MIDEARTH<1d></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.75 sec apart</entry> + </row> + <row> + <entry>MIDEARTH<1e></entry> + <entry>Reg</entry> + <entry>8</entry> + <entry>4 lots of 2, 0.75 sec apart</entry> + </row> + <row> + <entry>MIDEARTH<1b></entry> + <entry>Qry</entry> + <entry>18</entry> + <entry>900 sec apart at stable operation</entry> + </row> + <row> + <entry>JHT<03></entry> + <entry>Reg</entry> + <entry>2</entry> + <entry>This is the name of the user that logged onto Windows</entry> + </row> + <row> + <entry>Host Announcement MILGATE98</entry> + <entry>Ann</entry> + <entry>14</entry> + <entry>Every 120 sec</entry> + </row> + <row> + <entry>Domain/Workgroup Announcement MIDEARTH</entry> + <entry>Ann</entry> + <entry>6</entry> + <entry>900 sec apart at stable operation</entry> + </row> + <row> + <entry>Local Master Announcement WINEPRESSME</entry> + <entry>Ann</entry> + <entry>6</entry> + <entry>Insufficient detail to determine frequency</entry> + </row> + </tbody> + </tgroup> + </table> + + <para> + <indexterm><primary>host announcement</primary></indexterm> + <indexterm><primary>Local Master Announcement</primary></indexterm> + <indexterm><primary>Workgroup Announcement</primary></indexterm> + 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 <link linkend="hostannounce"/>. + </para> + + + <figure id="hostannounce"> + <title>Typical Windows 9x/Me Host Announcement</title> + <imagefile scale="41">HostAnnouncment</imagefile> + </figure> + </sect3> + + </sect2> + + <sect2> + <title>Simple Windows Client Connection Characteristics</title> + + <para> + 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. + </para> + + <procedure> + <title>Client Connection Exploration Steps</title> + + <step><para> + Configure a Windows 9x/Me machine (MILGATE98) with a share called <constant>Stuff</constant>. + Create a <parameter>Full Access</parameter> control password on this share. + </para></step> + + <step><para> + Configure another Windows 9x/Me machine (WINEPRESSME) as a client. Make sure that it exports + no shared resources. + </para></step> + + <step><para> + 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. + </para></step> + + <step><para> + Start Wireshark (or the network sniffer of your choice). + </para></step> + + <step><para> + From the WINEPRESSME machine, right-click <guimenu>Network Neighborhood</guimenu>, select + <guimenuitem>Explore</guimenuitem>, select + <menuchoice> + <guimenuitem>My Network Places</guimenuitem> + <guimenuitem>Entire Network</guimenuitem> + <guimenuitem>MIDEARTH</guimenuitem> + <guimenuitem>MILGATE98</guimenuitem> + <guimenuitem>Stuff</guimenuitem> + </menuchoice>. + Enter the password you set for the <constant>Full Control</constant> mode for the + <constant>Stuff</constant> share. + </para></step> + + <step><para> + When the share called <constant>Stuff</constant> is being displayed, stop the capture. + Save the captured data in case it is needed for later analysis. + </para></step> + + <step><para> + <indexterm><primary>session setup</primary></indexterm> + From the top of the packets captured, scan down to locate the first packet that has + interpreted as <constant>Session Setup AndX, User: anonymous; Tree Connect AndX, + Path: \\MILGATE98\IPC$</constant>. + </para></step> + + <step><para><indexterm> + <primary>Session Setup</primary> + </indexterm><indexterm> + <primary>Tree Connect</primary> + </indexterm> + In the dissection (analysis) panel, expand the <constant>SMB, Session Setup AndX Request, + and Tree Connect AndX Request</constant>. Examine both operations. Identify the name of + the user Account and what password was used. The Account name should be empty. + This is a <constant>NULL</constant> session setup packet. + </para></step> + + <step><para> + Return to the packet capture sequence. There will be a number of packets that have been + decoded of the type <constant>Session Setup AndX</constant>. Locate the last such packet + that was targeted at the <constant>\\MILGATE98\IPC$</constant> service. + </para></step> + + <step><para> + <indexterm><primary>password length</primary></indexterm> + <indexterm><primary>User Mode</primary></indexterm> + 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. + </para></step> + </procedure> + + <sect3> + <title>Findings and Comments</title> + + <para> + <indexterm><primary>IPC$</primary></indexterm> + The <constant>IPC$</constant> share serves a vital purpose<footnote><para>TOSHARG2, Sect 4.5.1</para></footnote> + 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 <constant>NULL</constant> + username and a <constant>NULL</constant> password. + </para> + + <para> + <indexterm><primary>account credentials</primary></indexterm> + 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 <constant>NULL</constant> + session setup can be established only by automatically mapping it to a valid UNIX + account. + </para> + + <para> + <indexterm><primary>NULL session</primary></indexterm><indexterm> + <primary>guest account</primary> + </indexterm> + <indexterm><primary>nobody</primary></indexterm> + Samba has a special name for the <constant>NULL</constant>, or empty, user account: + it calls it the <smbconfoption name="guest account"/>. The + default value of this parameter is <constant>nobody</constant>; 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 + <link linkend="nullconnect"/>. + </para> + + <figure id="nullconnect"> + <title>Typical Windows 9x/Me NULL SessionSetUp AndX Request</title> + + <imagefile scale="41">NullConnect</imagefile> + </figure> + + <para> + <indexterm><primary>nobody</primary></indexterm> + <indexterm><primary>/etc/passwd</primary></indexterm> + <indexterm><primary>guest account</primary></indexterm> + When a UNIX/Linux system does not have a <constant>nobody</constant> user account + (<filename>/etc/passwd</filename>), the operation of the <constant>NULL</constant> + 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 <link linkend="userconnect"/>. + </para> + + <figure id="userconnect"> + <title>Typical Windows 9x/Me User SessionSetUp AndX Request</title> + <imagefile scale="41">UserConnect</imagefile> + </figure> + + <para> + <indexterm><primary>encrypted</primary></indexterm> + 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. + </para> + + </sect3> + + </sect2> + + <sect2> + <title>Windows 200x/XP Client Interaction with Samba-3</title> + + <para> + By now you may be asking, <quote>Why did you choose to work with Windows 9x/Me?</quote> + </para> + + <para> + 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. + </para> + + <para> + The following exercise demonstrates the case that even MS Windows XP Professional with up-to-date service + updates also uses the <constant>NULL</constant> account, as well as user accounts. Simply follow the procedure + to complete this exercise. + </para> + + <para> + 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. + </para> + + <procedure> + <title>Steps to Explore Windows XP Pro Connection Set-up</title> + + <step><para> + Start your domain controller. Also, start the Wireshark monitoring machine, launch Wireshark, + and then wait for the next step to complete. + </para></step> + + <step><para> + Start the Windows XP Client and wait 5 minutes before proceeding. + </para></step> + + <step><para> + On the machine from which network activity will be monitored (using <command>Wireshark</command>), + launch <command>Wireshark</command> and click + <menuchoice> + <guimenu>Capture</guimenu> + <guimenuitem>Start</guimenuitem> + </menuchoice>. + </para> + + <para> + Click: + <orderedlist> + <listitem><para>Update list of packets in real time</para></listitem> + <listitem><para>Automatic scrolling in live capture</para></listitem> + <listitem><para>Enable MAC name resolution</para></listitem> + <listitem><para>Enable network name resolution</para></listitem> + <listitem><para>Enable transport name resolution</para></listitem> + </orderedlist> + Click <guibutton>OK</guibutton>. + </para></step> + + <step><para> + On the Windows XP Professional client, press <guimenu>Ctrl-Alt-Delete</guimenu> to bring + up the domain logon screen. Log in using valid credentials for a domain user account. + </para></step> + + <step><para> + Now proceed to connect to the domain controller as follows: + <menuchoice> + <guimenu>Start</guimenu> + <guimenuitem>(right-click) My Network Places</guimenuitem> + <guimenuitem>Explore</guimenuitem> + <guimenuitem>{Left Panel} [+] Entire Network</guimenuitem> + <guimenuitem>{Left Panel} [+] Microsoft Windows Network</guimenuitem> + <guimenuitem>{Left Panel} [+] Midearth</guimenuitem> + <guimenuitem>{Left Panel} [+] Frodo</guimenuitem> + <guimenuitem>{Left Panel} [+] data</guimenuitem> + </menuchoice>. Close the explorer window. + </para> + + <para> + In this step, our domain name is <constant>Midearth</constant>, the domain controller is called + <constant>Frodo</constant>, and we have connected to a share called <constant>data</constant>. + </para></step> + + <step><para> + Stop the capture on the <command>Wireshark</command> monitoring machine. Be sure to save the captured data + to a file so that you can refer to it again later. + </para></step> + + <step><para> + If desired, the Windows XP Professional client and the domain controller are no longer needed for exercises + in this chapter. + </para></step> + + <step><para> + <indexterm><primary>NTLMSSP_AUTH</primary></indexterm> + <indexterm><primary>session setup</primary></indexterm> + From the top of the packets captured, scan down to locate the first packet that has + interpreted as <constant>Session Setup AndX Request, NTLMSSP_AUTH</constant>. + </para></step> + + <step><para> + <indexterm><primary>GSS-API</primary></indexterm> + <indexterm><primary>SPNEGO</primary></indexterm> + <indexterm><primary>NTLMSSP</primary></indexterm> + In the dissection (analysis) panel, expand the <constant>SMB, Session Setup AndX Request</constant>. + Expand the packet decode information, beginning at the <constant>Security Blob:</constant> + entry. Expand the <constant>GSS-API -> SPNEGO -> netTokenTarg -> responseToken -> NTLMSSP</constant> + keys. This should reveal that this is a <constant>NULL</constant> session setup packet. + The <constant>User name: NULL</constant> so indicates. An example decode is shown in + <link linkend="XPCap01"/>. + </para></step> + + <step><para> + Return to the packet capture sequence. There will be a number of packets that have been + decoded of the type <constant>Session Setup AndX Request</constant>. Click the last such packet that + has been decoded as <constant>Session Setup AndX Request, NTLMSSP_AUTH</constant>. + </para></step> + + <step><para> + <indexterm><primary>encrypted password</primary></indexterm> + In the dissection (analysis) panel, expand the <constant>SMB, Session Setup AndX Request</constant>. + Expand the packet decode information, beginning at the <constant>Security Blob:</constant> + entry. Expand the <constant>GSS-API -> SPNEGO -> netTokenTarg -> responseToken -> NTLMSSP</constant> + keys. This should reveal that this is a <constant>User Mode</constant> session setup packet. + The <constant>User name: jht</constant> so indicates. An example decode is shown in + <link linkend="XPCap02"/>. In this case the user name was <constant>jht</constant>. This packet + decode includes the <constant>Lan Manager Response:</constant> and the <constant>NTLM Response:</constant>. + The values of these two parameters are the Microsoft encrypted password hashes: respectively, the LanMan + password and then the NT (case-preserving) password hash. + </para></step> + + <step><para> + <indexterm><primary>password length</primary></indexterm> + <indexterm><primary>User Mode</primary></indexterm> + The passwords are 24-character hexadecimal numbers. This packet confirms that this is a User Mode + session setup packet. + </para></step> + + </procedure> + + <figure id="XPCap01"> + <title>Typical Windows XP NULL Session Setup AndX Request</title> + <imagefile scale="50">WindowsXP-NullConnection</imagefile> + </figure> + + <figure id="XPCap02"> + <title>Typical Windows XP User Session Setup AndX Request</title> + <imagefile scale="50">WindowsXP-UserConnection</imagefile> + </figure> + + <sect3> + <title>Discussion</title> + + <para><indexterm> + <primary>NULL-Session</primary> + </indexterm> + 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 + <constant>NULL-Session</constant> 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. + </para> + + </sect3> + + </sect2> + + <sect2> + <title>Conclusions to Exercises</title> + + <para> + In summary, the following points have been established in this chapter: + </para> + + <itemizedlist> + <listitem><para> + When NetBIOS over TCP/IP protocols are enabled, MS Windows networking employs broadcast-oriented messaging protocols to provide knowledge of network services. + </para></listitem> + + <listitem><para> + 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. + </para></listitem> + + <listitem><para> + All Samba servers must be configured with a mechanism for mapping the <constant>NULL-Session</constant> + to a valid but nonprivileged UNIX system account. + </para></listitem> + + <listitem><para> + The use of Microsoft encrypted passwords is built right into the fabric of Windows + networking operations. Such passwords cannot be provided from the UNIX <filename>/etc/passwd</filename> + 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 <constant>smbpasswd</constant> + file or in an LDAP database. Samba-3 permits use of multiple <parameter>passdb backend</parameter> + databases in concurrent deployment. Refer to <emphasis>TOSHARG2</emphasis>, Chapter 10, <quote>Account Information Databases.</quote> + </para></listitem> + </itemizedlist> + + </sect2> + +</sect1> + +<sect1 id="chap01conc"> + <title>Dissection and Discussion</title> + + <para> + <indexterm><primary>guest account</primary></indexterm> + The exercises demonstrate the use of the <constant>guest</constant> 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. + </para> + + <para> + Those wishing background information regarding NetBIOS name types should refer to + the Microsoft knowledgebase article + <ulink url="http://support.microsoft.com/support/kb/articles/Q102/78/8.asp">Q102878.</ulink> + </para> + + <sect2> + <title>Technical Issues</title> + + <para> + <indexterm><primary>guest account</primary></indexterm> + Network browsing involves SMB broadcast announcements, SMB enumeration requests, + connections to the <constant>IPC$</constant> share, share enumerations, and SMB connection + setup processes. The use of anonymous connections to a Samba server involve the use of + the <parameter>guest account</parameter> that must map to a valid UNIX UID. + </para> + + </sect2> + +</sect1> + +<sect1 id="chap01qa"> + <title>Questions and Answers</title> + + <para> + The questions and answers given in this section are designed to highlight important aspects of Microsoft + Windows networking. + </para> + + <qandaset defaultlabel="chap01qa" type="number"> + <qandaentry> + <question> + + <para> + What is the significance of the MIDEARTH<1b> type query? + </para> + + </question> + <answer> + + <para> + <indexterm><primary>Domain Master Browser</primary><see>DMB</see></indexterm> + <indexterm><primary>DMB</primary></indexterm> + 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 <emphasis>TOSHARG2,</emphasis> Chapter 9, Section 9.7, <quote>Technical Overview of Browsing,</quote> + for details regarding the function of the DMB and its role in network browsing. + </para> + + </answer> + </qandaentry> + + <qandaentry> + <question> + + <para> + What is the significance of the MIDEARTH<1d> type name registration? + </para> + + </question> + <answer> + + <para> + <indexterm><primary>Local Master Browser</primary><see>LMB</see></indexterm> + <indexterm><primary>LMB</primary></indexterm> + 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. + </para> + + <para> + 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: + </para> + + <itemizedlist> + <listitem><para> + The list of machines known to the LMB (i.e., the browse list) + </para></listitem> + + <listitem><para> + The IP addresses of all domain controllers known for the domain + </para></listitem> + + <listitem><para> + The IP addresses of LMBs + </para></listitem> + + <listitem><para> + The IP address of the DMB (if one exists) + </para></listitem> + + <listitem><para> + The IP address of the LMB on the local segment + </para></listitem> + </itemizedlist> + + </answer> + </qandaentry> + + <qandaentry> + <question> + + <para> + What is the role and significance of the <01><02>__MSBROWSE__<02><01> + name registration? + </para> + + </question> + <answer> + + <para> + <indexterm><primary>Browse Master</primary></indexterm> + 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. + </para> + + </answer> + </qandaentry> + + <qandaentry> + <question> + + <para> + What is the significance of the MIDEARTH<1e> type name registration? + </para> + + </question> + <answer> + + <para> + <indexterm><primary>Browser Election Service</primary></indexterm> + 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. + </para> + + </answer> + </qandaentry> + + <qandaentry> + <question> + + <para> + <indexterm><primary>guest account</primary></indexterm> + What is the significance of the <parameter>guest account</parameter> in smb.conf? + </para> + + </question> + <answer> + + <para> + 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 <constant>nobody</constant>. If the UNIX/Linux system that + is hosting Samba does not have a <constant>nobody</constant> account and an alternate + mapping has not been specified, network browsing will not work at all. + </para> + + <para> + It should be noted that the <parameter>guest account</parameter> is essential to + Samba operation. Either the operating system must have an account called <constant>nobody</constant> + or there must be an entry in the &smb.conf; file with a valid UNIX account, such as + <smbconfoption name="guest account">ftp</smbconfoption>. + </para> + + </answer> + </qandaentry> + + <qandaentry> + <question> + + <para> + Is it possible to reduce network broadcast activity with Samba-3? + </para> + + </question> + <answer> + + <para> + <indexterm><primary>WINS</primary></indexterm> + <indexterm><primary>NetBIOS</primary></indexterm> + Yes, there are two ways to do this. The first involves use of WINS (See <emphasis>TOSHARG2</emphasis>, Chapter 9, + Section 9.5, <quote>WINS &smbmdash; The Windows Inter-networking Name Server</quote>); the + alternate method involves disabling the use of NetBIOS over TCP/IP. This second method requires + a correctly configured DNS server (see <emphasis>TOSHARG2</emphasis>, Chapter 9, Section 9.3, <quote>Discussion</quote>). + </para> + + <para> + <indexterm><primary>broadcast</primary></indexterm> + <indexterm><primary>NetBIOS</primary><secondary>Node Type</secondary></indexterm> + <indexterm><primary>Hybrid</primary></indexterm> + The use of WINS reduces network broadcast traffic. The reduction is greatest when all network + clients are configured to operate in <parameter>Hybrid Mode</parameter>. 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 <smbconfoption name="name resolve order">wins host cast</smbconfoption>. + </para> + + <note><para> + Use of SMB without NetBIOS is possible only on Windows 200x/XP Professional clients and servers, as + well as with Samba-3. + </para></note> + + </answer> + </qandaentry> + + <qandaentry> + <question> + + <para> + Can I just use plain-text passwords with Samba? + </para> + + </question> + <answer> + + <para> + Yes, you can configure Samba to use plain-text passwords, though this does create a few problems. + </para> + + <para> + First, the use of <filename>/etc/passwd</filename>-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. + </para> + + <para> + 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. + </para> + + <para> + Samba-3 supports Microsoft encrypted passwords. Be advised not to reintroduce plain-text password handling. + Just create user accounts by running <command>smbpasswd -a 'username'</command> + </para> + + <para> + It is not possible to add a user to the <parameter>passdb backend</parameter> database unless there is + a UNIX system account for that user. On systems that run <command>winbindd</command> to access the Samba + PDC/BDC to provide Windows user and group accounts, the <parameter>idmap uid, idmap gid</parameter> ranges + set in the &smb.conf; file provide the local UID/GIDs needed for local identity management purposes. + </para> + + </answer> + </qandaentry> + + <qandaentry> + <question> + + <para> + What parameter in the &smb.conf; file is used to enable the use of encrypted passwords? + </para> + + </question> + <answer> + + <para> + The parameter in the &smb.conf; file that controls this behavior is known as <parameter>encrypt + passwords</parameter>. The default setting for this in Samba-3 is <constant>Yes (Enabled)</constant>. + </para> + + </answer> + </qandaentry> + + <qandaentry> + <question> + + <para> + Is it necessary to specify <smbconfoption name="encrypt passwords">Yes</smbconfoption> + when Samba-3 is configured as a domain member? + </para> + + </question> + <answer> + + <para> + No. This is the default behavior. + </para> + + </answer> + </qandaentry> + + <qandaentry> + <question> + + <para> + Is it necessary to specify a <parameter>guest account</parameter> when Samba-3 is configured + as a domain member server? + </para> + + </question> + <answer> + + <para> + Yes. This is a local function on the server. The default setting is to use the UNIX account + <constant>nobody</constant>. If this account does not exist on the UNIX server, then it is + necessary to provide a <smbconfoption name="guest account">an_account</smbconfoption>, + where <constant>an_account</constant> is a valid local UNIX user account. + </para> + + </answer> + </qandaentry> + </qandaset> + +</sect1> + +</chapter> + |