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r368 r411 1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 18. Securing Samba</title><link rel="stylesheet" href="../samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.7 5.2"><link rel="home" href="index.html" title="The Official Samba 3.3.x HOWTO and Reference Guide"><link rel="up" href="optional.html" title="Part III. Advanced Configuration"><link rel="prev" href="locking.html" title="Chapter 17. File and Record Locking"><link rel="next" href="InterdomainTrusts.html" title="Chapter 19. Interdomain Trust Relationships"></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 18. Securing Samba</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="locking.html">Prev</a> </td><th width="60%" align="center">Part III. Advanced Configuration</th><td width="20%" align="right"> <a accesskey="n" href="InterdomainTrusts.html">Next</a></td></tr></table><hr></div><div class="chapter" title="Chapter 18. Securing Samba"><div class="titlepage"><div><div><h2 class="title"><a name="securing-samba"></a>Chapter 18. Securing Samba</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Andrew</span> <span class="surname">Tridgell</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><code class="email"><<a class="email" href="mailto:tridge@samba.org">tridge@samba.org</a>></code></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">John</span> <span class="othername">H.</span> <span class="surname">Terpstra</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><code class="email"><<a class="email" href="mailto:jht@samba.org">jht@samba.org</a>></code></p></div></div></div></div><div><p class="pubdate">May 26, 2003</p></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="securing-samba.html#id2624168">Introduction</a></span></dt><dt><span class="sect1"><a href="securing-samba.html#id2624266">Features and Benefits</a></span></dt><dt><span class="sect1"><a href="securing-samba.html#id2624413">Technical Discussion of Protective Measures and Issues</a></span></dt><dd><dl><dt><span class="sect2"><a href="securing-samba.html#id2624429">Using Host-Based Protection</a></span></dt><dt><span class="sect2"><a href="securing-samba.html#id2624583">User-Based Protection</a></span></dt><dt><span class="sect2"><a href="securing-samba.html#id2624642">Using Interface Protection</a></span></dt><dt><span class="sect2"><a href="securing-samba.html#firewallports">Using a Firewall</a></span></dt><dt><span class="sect2"><a href="securing-samba.html#id2624993">Using IPC$ Share-Based Denials </a></span></dt><dt><span class="sect2"><a href="securing-samba.html#id2625141">NTLMv2 Security</a></span></dt></dl></dd><dt><span class="sect1"><a href="securing-samba.html#id2625196">Upgrading Samba</a></span></dt><dt><span class="sect1"><a href="securing-samba.html#id2625240">Common Errors</a></span></dt><dd><dl><dt><span class="sect2"><a href="securing-samba.html#id2625255">Smbclient Works on Localhost, but the Network Is Dead</a></span></dt><dt><span class="sect2"><a href="securing-samba.html#id2625284">Why Can Users Access Other Users' Home Directories?</a></span></dt></dl></dd></dl></div><div class="sect1" title="Introduction"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2624168"></a>Introduction</h2></div></div></div><p>2 <a class="indexterm" name="id26 24176"></a>3 <a class="indexterm" name="id26 24182"></a>4 <a class="indexterm" name="id26 24190"></a>5 <a class="indexterm" name="id26 24196"></a>6 <a class="indexterm" name="id26 24203"></a>7 <a class="indexterm" name="id26 24210"></a>8 <a class="indexterm" name="id26 24217"></a>1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 18. Securing Samba</title><link rel="stylesheet" href="../samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.74.0"><link rel="home" href="index.html" title="The Official Samba 3.3.x HOWTO and Reference Guide"><link rel="up" href="optional.html" title="Part III. Advanced Configuration"><link rel="prev" href="locking.html" title="Chapter 17. File and Record Locking"><link rel="next" href="InterdomainTrusts.html" title="Chapter 19. Interdomain Trust Relationships"></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 18. Securing Samba</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="locking.html">Prev</a> </td><th width="60%" align="center">Part III. Advanced Configuration</th><td width="20%" align="right"> <a accesskey="n" href="InterdomainTrusts.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="securing-samba"></a>Chapter 18. Securing Samba</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Andrew</span> <span class="orgname">Samba Team</span> <span class="surname">Tridgell</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><code class="email"><<a class="email" href="mailto:tridge@samba.org">tridge@samba.org</a>></code></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">John</span> <span class="othername">H.</span> <span class="orgname">Samba Team</span> <span class="surname">Terpstra</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><code class="email"><<a class="email" href="mailto:jht@samba.org">jht@samba.org</a>></code></p></div></div></div></div><div><p class="pubdate">May 26, 2003</p></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="securing-samba.html#id2618082">Introduction</a></span></dt><dt><span class="sect1"><a href="securing-samba.html#id2618181">Features and Benefits</a></span></dt><dt><span class="sect1"><a href="securing-samba.html#id2618327">Technical Discussion of Protective Measures and Issues</a></span></dt><dd><dl><dt><span class="sect2"><a href="securing-samba.html#id2618343">Using Host-Based Protection</a></span></dt><dt><span class="sect2"><a href="securing-samba.html#id2618497">User-Based Protection</a></span></dt><dt><span class="sect2"><a href="securing-samba.html#id2618557">Using Interface Protection</a></span></dt><dt><span class="sect2"><a href="securing-samba.html#firewallports">Using a Firewall</a></span></dt><dt><span class="sect2"><a href="securing-samba.html#id2618907">Using IPC$ Share-Based Denials </a></span></dt><dt><span class="sect2"><a href="securing-samba.html#id2619056">NTLMv2 Security</a></span></dt></dl></dd><dt><span class="sect1"><a href="securing-samba.html#id2619110">Upgrading Samba</a></span></dt><dt><span class="sect1"><a href="securing-samba.html#id2619154">Common Errors</a></span></dt><dd><dl><dt><span class="sect2"><a href="securing-samba.html#id2619170">Smbclient Works on Localhost, but the Network Is Dead</a></span></dt><dt><span class="sect2"><a href="securing-samba.html#id2619198">Why Can Users Access Other Users' Home Directories?</a></span></dt></dl></dd></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2618082"></a>Introduction</h2></div></div></div><p> 2 <a class="indexterm" name="id2618090"></a> 3 <a class="indexterm" name="id2618097"></a> 4 <a class="indexterm" name="id2618104"></a> 5 <a class="indexterm" name="id2618111"></a> 6 <a class="indexterm" name="id2618118"></a> 7 <a class="indexterm" name="id2618124"></a> 8 <a class="indexterm" name="id2618131"></a> 9 9 The information contained in this chapter applies in general to all Samba installations. Security is 10 10 everyone's concern in the information technology world. A surprising number of Samba servers are being … … 13 13 some network administrators to insist on the installation of robust firewalls even on servers that are located 14 14 inside secured networks. This chapter provides information to assist the administrator who understands 15 how to create the needed barriers and deterents against <span class="quote">“<span class="quote">the enemy</span>”</span>, no matter where [s]he may15 how to create the needed barriers and deterents against “<span class="quote">the enemy</span>”, no matter where [s]he may 16 16 come from. 17 17 </p><div class="blockquote"><blockquote class="blockquote"><p> 18 A new apprentice reported for duty to the chief engineer of a boiler house. He said, <span class="quote">“<span class="quote">Here I am,19 if you will show me the boiler I'll start working on it.</span>” </span> Then engineer replied, <span class="quote">“<span class="quote">You're leaning20 on it!</span>” </span>18 A new apprentice reported for duty to the chief engineer of a boiler house. He said, “<span class="quote">Here I am, 19 if you will show me the boiler I'll start working on it.</span>” Then engineer replied, “<span class="quote">You're leaning 20 on it!</span>” 21 21 </p></blockquote></div><p> 22 22 Security concerns are just like that. You need to know a little about the subject to appreciate 23 23 how obvious most of it really is. The challenge for most of us is to discover that first morsel 24 24 of knowledge with which we may unlock the secrets of the masters. 25 </p></div><div class="sect1" title="Features and Benefits"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2624266"></a>Features and Benefits</h2></div></div></div><p>26 <a class="indexterm" name="id26 24274"></a>27 <a class="indexterm" name="id26 24281"></a>28 <a class="indexterm" name="id26 24288"></a>29 <a class="indexterm" name="id26 24295"></a>25 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2618181"></a>Features and Benefits</h2></div></div></div><p> 26 <a class="indexterm" name="id2618189"></a> 27 <a class="indexterm" name="id2618196"></a> 28 <a class="indexterm" name="id2618203"></a> 29 <a class="indexterm" name="id2618210"></a> 30 30 There are three levels at which security principles must be observed in order to render a site 31 31 at least moderately secure. They are the perimeter firewall, the configuration of the host … … 35 35 the latest protocols to permit more secure MS Windows file and print operations. 36 36 </p><p> 37 <a class="indexterm" name="id26 24316"></a>38 <a class="indexterm" name="id26 24323"></a>39 <a class="indexterm" name="id26 24330"></a>37 <a class="indexterm" name="id2618230"></a> 38 <a class="indexterm" name="id2618237"></a> 39 <a class="indexterm" name="id2618244"></a> 40 40 Samba can be secured from connections that originate from outside the local network. This can be done using 41 41 <span class="emphasis"><em>host-based protection</em></span>, using Samba's implementation of a technology known as 42 <span class="quote">“<span class="quote">tcpwrappers,</span>”</span>or it may be done be using <span class="emphasis"><em>interface-based exclusion</em></span> so42 “<span class="quote">tcpwrappers,</span>” or it may be done be using <span class="emphasis"><em>interface-based exclusion</em></span> so 43 43 <span class="application">smbd</span> will bind only to specifically permitted interfaces. It is also possible to set specific share- or 44 44 resource-based exclusions, for example, on the <em class="parameter"><code>[IPC$]</code></em> autoshare. The <em class="parameter"><code>[IPC$]</code></em> share is used for browsing purposes as well as to establish TCP/IP connections. 45 45 </p><p> 46 <a class="indexterm" name="id26 24377"></a>47 <a class="indexterm" name="id26 24386"></a>48 <a class="indexterm" name="id26 24393"></a>46 <a class="indexterm" name="id2618291"></a> 47 <a class="indexterm" name="id2618301"></a> 48 <a class="indexterm" name="id2618307"></a> 49 49 Another method by which Samba may be secured is by setting Access Control Entries (ACEs) in an Access 50 50 Control List (ACL) on the shares themselves. This is discussed in 51 51 <a class="link" href="AccessControls.html" title="Chapter 16. File, Directory, and Share Access Controls">File, Directory, and Share Access Controls</a>. 52 </p></div><div class="sect1" title="Technical Discussion of Protective Measures and Issues"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2624413"></a>Technical Discussion of Protective Measures and Issues</h2></div></div></div><p>52 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2618327"></a>Technical Discussion of Protective Measures and Issues</h2></div></div></div><p> 53 53 The key challenge of security is that protective measures suffice at best 54 54 only to close the door on known exploits and breach techniques. Never assume that … … 56 56 fortress! Given the history of information systems so far, it is only a matter of time 57 57 before someone will find yet another vulnerability. 58 </p><div class="sect2" title="Using Host-Based Protection"><div class="titlepage"><div><div><h3 class="title"><a name="id2624429"></a>Using Host-Based Protection</h3></div></div></div><p>59 <a class="indexterm" name="id26 24437"></a>60 <a class="indexterm" name="id26 24443"></a>61 <a class="indexterm" name="id26 24450"></a>58 </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2618343"></a>Using Host-Based Protection</h3></div></div></div><p> 59 <a class="indexterm" name="id2618351"></a> 60 <a class="indexterm" name="id2618358"></a> 61 <a class="indexterm" name="id2618364"></a> 62 62 In many installations of Samba, the greatest threat comes from outside 63 63 your immediate network. By default, Samba accepts connections from … … 66 66 especially vulnerable. 67 67 </p><p> 68 <a class="indexterm" name="id26 24465"></a>69 <a class="indexterm" name="id26 24472"></a>68 <a class="indexterm" name="id2618380"></a> 69 <a class="indexterm" name="id2618386"></a> 70 70 One of the simplest fixes in this case is to use the <a class="link" href="smb.conf.5.html#HOSTSALLOW" target="_top">hosts allow</a> and 71 71 <a class="link" href="smb.conf.5.html#HOSTSDENY" target="_top">hosts deny</a> options in the Samba <code class="filename">smb.conf</code> configuration file to 72 72 allow access to your server only from a specific range of hosts. An example might be: 73 </p><table border="0" summary="Simple list" class="simplelist"><tr><td><a class="indexterm" name="id2624519"></a><em class="parameter"><code>hosts allow = 127.0.0.1 192.168.2.0/24 192.168.3.0/24</code></em></td></tr><tr><td><a class="indexterm" name="id2624531"></a><em class="parameter"><code>hosts deny = 0.0.0.0/0</code></em></td></tr></table><p>74 </p><p> 75 <a class="indexterm" name="id26 24546"></a>76 <a class="indexterm" name="id26 24553"></a>77 <a class="indexterm" name="id26 24560"></a>73 </p><table class="simplelist" border="0" summary="Simple list"><tr><td><a class="indexterm" name="id2618433"></a><em class="parameter"><code>hosts allow = 127.0.0.1 192.168.2.0/24 192.168.3.0/24</code></em></td></tr><tr><td><a class="indexterm" name="id2618445"></a><em class="parameter"><code>hosts deny = 0.0.0.0/0</code></em></td></tr></table><p> 74 </p><p> 75 <a class="indexterm" name="id2618460"></a> 76 <a class="indexterm" name="id2618467"></a> 77 <a class="indexterm" name="id2618474"></a> 78 78 The above will allow SMB connections only from <code class="constant">localhost</code> (your own 79 79 computer) and from the two private networks 192.168.2 and 192.168.3. All other 80 80 connections will be refused as soon as the client sends its first packet. The refusal 81 81 will be marked as <code class="literal">not listening on called name</code> error. 82 </p></div><div class="sect2" title="User-Based Protection"><div class="titlepage"><div><div><h3 class="title"><a name="id2624583"></a>User-Based Protection</h3></div></div></div><p>82 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2618497"></a>User-Based Protection</h3></div></div></div><p> 83 83 If you want to restrict access to your server to valid users only, then the following 84 84 method may be of use. In the <code class="filename">smb.conf</code> <em class="parameter"><code>[global]</code></em> section put: 85 </p><table border="0" summary="Simple list" class="simplelist"><tr><td><a class="indexterm" name="id2624610"></a><em class="parameter"><code>valid users = @smbusers, jacko</code></em></td></tr></table><p>86 </p><p> 87 <a class="indexterm" name="id26 24626"></a>85 </p><table class="simplelist" border="0" summary="Simple list"><tr><td><a class="indexterm" name="id2618525"></a><em class="parameter"><code>valid users = @smbusers, jacko</code></em></td></tr></table><p> 86 </p><p> 87 <a class="indexterm" name="id2618540"></a> 88 88 This restricts all server access either to the user <span class="emphasis"><em>jacko</em></span> 89 89 or to members of the system group <span class="emphasis"><em>smbusers</em></span>. 90 </p></div><div class="sect2" title="Using Interface Protection"><div class="titlepage"><div><div><h3 class="title"><a name="id2624642"></a>Using Interface Protection</h3></div></div></div><p>91 <a class="indexterm" name="id26 24650"></a>92 <a class="indexterm" name="id26 24657"></a>93 <a class="indexterm" name="id26 24664"></a>90 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2618557"></a>Using Interface Protection</h3></div></div></div><p> 91 <a class="indexterm" name="id2618565"></a> 92 <a class="indexterm" name="id2618572"></a> 93 <a class="indexterm" name="id2618579"></a> 94 94 By default, Samba accepts connections on any network interface that 95 95 it finds on your system. That means if you have an ISDN line or a PPP … … 98 98 </p><p> 99 99 You can change this behavior using options like this: 100 </p><table border="0" summary="Simple list" class="simplelist"><tr><td><a class="indexterm" name="id2624685"></a><em class="parameter"><code>interfaces = eth* lo</code></em></td></tr><tr><td><a class="indexterm" name="id2624697"></a><em class="parameter"><code>bind interfaces only = yes</code></em></td></tr></table><p>101 </p><p> 102 <a class="indexterm" name="id26 24712"></a>103 <a class="indexterm" name="id26 24719"></a>104 <a class="indexterm" name="id26 24726"></a>105 <a class="indexterm" name="id26 24733"></a>100 </p><table class="simplelist" border="0" summary="Simple list"><tr><td><a class="indexterm" name="id2618600"></a><em class="parameter"><code>interfaces = eth* lo</code></em></td></tr><tr><td><a class="indexterm" name="id2618611"></a><em class="parameter"><code>bind interfaces only = yes</code></em></td></tr></table><p> 101 </p><p> 102 <a class="indexterm" name="id2618626"></a> 103 <a class="indexterm" name="id2618633"></a> 104 <a class="indexterm" name="id2618640"></a> 105 <a class="indexterm" name="id2618647"></a> 106 106 This tells Samba to listen for connections only on interfaces with a name starting with 107 107 <code class="constant">eth</code> such as <code class="constant">eth0</code> or <code class="constant">eth1</code>, plus on the loopback interface called … … 109 109 the common name for Ethernet adapters on Linux. 110 110 </p><p> 111 <a class="indexterm" name="id26 24762"></a>112 <a class="indexterm" name="id26 24769"></a>113 <a class="indexterm" name="id26 24775"></a>114 <a class="indexterm" name="id26 24782"></a>111 <a class="indexterm" name="id2618676"></a> 112 <a class="indexterm" name="id2618683"></a> 113 <a class="indexterm" name="id2618690"></a> 114 <a class="indexterm" name="id2618696"></a> 115 115 If you use the above and someone tries to make an SMB connection to your host over a PPP interface called 116 116 <code class="constant">ppp0</code>, then [s]he will get a TCP connection refused reply. In that case, no Samba code … … 119 119 valid active services. 120 120 </p><p> 121 <a class="indexterm" name="id26 24803"></a>122 <a class="indexterm" name="id26 24810"></a>123 <a class="indexterm" name="id26 24817"></a>124 <a class="indexterm" name="id26 24824"></a>125 <a class="indexterm" name="id26 24831"></a>121 <a class="indexterm" name="id2618717"></a> 122 <a class="indexterm" name="id2618724"></a> 123 <a class="indexterm" name="id2618731"></a> 124 <a class="indexterm" name="id2618738"></a> 125 <a class="indexterm" name="id2618745"></a> 126 126 A better response would be to ignore the connection (from, for example, ppp0) altogether. The 127 127 advantage of ignoring the connection attempt, as compared with refusing it, is that it foils those who … … 129 129 or denial of service attacks. This method of dealing with potential malicious activity demands the 130 130 use of appropriate firewall mechanisms. 131 </p></div><div class="sect2" title="Using a Firewall"><div class="titlepage"><div><div><h3 class="title"><a name="firewallports"></a>Using a Firewall</h3></div></div></div><p>132 <a class="indexterm" name="id26 24860"></a>133 <a class="indexterm" name="id26 24866"></a>134 <a class="indexterm" name="id26 24873"></a>131 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="firewallports"></a>Using a Firewall</h3></div></div></div><p> 132 <a class="indexterm" name="id2618774"></a> 133 <a class="indexterm" name="id2618781"></a> 134 <a class="indexterm" name="id2618787"></a> 135 135 Many people use a firewall to deny access to services they do not want exposed outside their network. This can 136 136 be a good idea, although I recommend using it in conjunction with the above methods so you are protected even … … 139 139 If you are setting up a firewall, you need to know what TCP and UDP ports to allow and block. Samba uses 140 140 the following: 141 <a class="indexterm" name="id26 24890"></a>142 <a class="indexterm" name="id26 24897"></a>143 <a class="indexterm" name="id26 24904"></a>144 <a class="indexterm" name="id26 24911"></a>145 <a class="indexterm" name="id26 24918"></a>146 </p><table border="0" summary="Simple list" class="simplelist"><tr><td>Port 135/TCP - used by smbd</td></tr><tr><td>Port 137/UDP - used by nmbd</td></tr><tr><td>Port 138/UDP - used by nmbd</td></tr><tr><td>Port 139/TCP - used by smbd</td></tr><tr><td>Port 445/TCP - used by smbd</td></tr></table><p>147 <a class="indexterm" name="id26 24952"></a>141 <a class="indexterm" name="id2618804"></a> 142 <a class="indexterm" name="id2618811"></a> 143 <a class="indexterm" name="id2618818"></a> 144 <a class="indexterm" name="id2618825"></a> 145 <a class="indexterm" name="id2618832"></a> 146 </p><table class="simplelist" border="0" summary="Simple list"><tr><td>Port 135/TCP - used by smbd</td></tr><tr><td>Port 137/UDP - used by nmbd</td></tr><tr><td>Port 138/UDP - used by nmbd</td></tr><tr><td>Port 139/TCP - used by smbd</td></tr><tr><td>Port 445/TCP - used by smbd</td></tr></table><p> 147 <a class="indexterm" name="id2618866"></a> 148 148 The last one is important because many older firewall setups may not be aware of it, given that this port 149 149 was only added to the protocol in recent years. 150 150 </p><p> 151 <a class="indexterm" name="id26 24965"></a>152 <a class="indexterm" name="id26 24972"></a>153 <a class="indexterm" name="id26 24979"></a>151 <a class="indexterm" name="id2618879"></a> 152 <a class="indexterm" name="id2618886"></a> 153 <a class="indexterm" name="id2618893"></a> 154 154 When configuring a firewall, the high order ports (1024-65535) are often used for outgoing connections and 155 155 therefore should be permitted through the firewall. It is prudent to block incoming packets on the high order 156 156 ports except for established connections. 157 </p></div><div class="sect2" title="Using IPC$ Share-Based Denials"><div class="titlepage"><div><div><h3 class="title"><a name="id2624993"></a>Using IPC$ Share-Based Denials </h3></div></div></div><p>158 <a class="indexterm" name="id26 25001"></a>159 <a class="indexterm" name="id26 25008"></a>160 <a class="indexterm" name="id26 25014"></a>157 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2618907"></a>Using IPC$ Share-Based Denials </h3></div></div></div><p> 158 <a class="indexterm" name="id2618915"></a> 159 <a class="indexterm" name="id2618922"></a> 160 <a class="indexterm" name="id2618929"></a> 161 161 If the above methods are not suitable, then you could also place a more specific deny on the IPC$ share that 162 162 is used in the recently discovered security hole. This allows you to offer access to other shares while … … 164 164 </p><p> 165 165 To do this you could use: 166 </p><table border="0" summary="Simple list" class="simplelist"><tr><td> </td></tr><tr><td><em class="parameter"><code>[IPC$]</code></em></td></tr><tr><td><a class="indexterm" name="id2625049"></a><em class="parameter"><code>hosts allow = 192.168.115.0/24 127.0.0.1</code></em></td></tr><tr><td><a class="indexterm" name="id2625061"></a><em class="parameter"><code>hosts deny = 0.0.0.0/0</code></em></td></tr></table><p>167 </p><p> 168 <a class="indexterm" name="id26 25076"></a>169 <a class="indexterm" name="id26 25083"></a>170 <a class="indexterm" name="id26 25090"></a>166 </p><table class="simplelist" border="0" summary="Simple list"><tr><td> </td></tr><tr><td><em class="parameter"><code>[IPC$]</code></em></td></tr><tr><td><a class="indexterm" name="id2618963"></a><em class="parameter"><code>hosts allow = 192.168.115.0/24 127.0.0.1</code></em></td></tr><tr><td><a class="indexterm" name="id2618975"></a><em class="parameter"><code>hosts deny = 0.0.0.0/0</code></em></td></tr></table><p> 167 </p><p> 168 <a class="indexterm" name="id2618990"></a> 169 <a class="indexterm" name="id2618997"></a> 170 <a class="indexterm" name="id2619004"></a> 171 171 This instructs Samba that IPC$ connections are not allowed from anywhere except the two listed network 172 172 addresses (localhost and the 192.168.115 subnet). Connections to other shares are still allowed. Because the … … 174 174 against attackers who do not know a valid username/password for your host. 175 175 </p><p> 176 <a class="indexterm" name="id26 25107"></a>177 <a class="indexterm" name="id26 25114"></a>178 <a class="indexterm" name="id26 25121"></a>176 <a class="indexterm" name="id2619021"></a> 177 <a class="indexterm" name="id2619028"></a> 178 <a class="indexterm" name="id2619035"></a> 179 179 If you use this method, then clients will be given an <code class="literal">`access denied'</code> reply when they try 180 180 to access the IPC$ share. Those clients will not be able to browse shares and may also be unable to access 181 181 some other resources. This is not recommended unless for some reason you cannot use one of the other methods 182 182 just discussed. 183 </p></div><div class="sect2" title="NTLMv2 Security"><div class="titlepage"><div><div><h3 class="title"><a name="id2625141"></a>NTLMv2 Security</h3></div></div></div><p>184 <a class="indexterm" name="id26 25149"></a>183 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2619056"></a>NTLMv2 Security</h3></div></div></div><p> 184 <a class="indexterm" name="id2619063"></a> 185 185 To configure NTLMv2 authentication, the following registry keys are worth knowing about: 186 186 </p><p> … … 202 202 NtlmMinServerSec is set to 0x00080000, the connection will fail if NTLMv2 203 203 session security is negotiated. 204 </p></div></div><div class="sect1" title="Upgrading Samba"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2625196"></a>Upgrading Samba</h2></div></div></div><p>205 <a class="indexterm" name="id26 25204"></a>206 <a class="indexterm" name="id26 25211"></a>207 <a class="indexterm" name="id26 25218"></a>204 </p></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2619110"></a>Upgrading Samba</h2></div></div></div><p> 205 <a class="indexterm" name="id2619118"></a> 206 <a class="indexterm" name="id2619125"></a> 207 <a class="indexterm" name="id2619132"></a> 208 208 Please check regularly on <a class="ulink" href="http://www.samba.org/" target="_top">http://www.samba.org/</a> for 209 209 updates and important announcements. Occasionally security releases are made, and it is highly recommended to 210 210 upgrade Samba promptly when a security vulnerability is discovered. Check with your OS vendor for OS-specific 211 211 upgrades. 212 </p></div><div class="sect1" title="Common Errors"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2625240"></a>Common Errors</h2></div></div></div><p>212 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2619154"></a>Common Errors</h2></div></div></div><p> 213 213 If all Samba and host platform configurations were really as intuitive as one might like them to be, this 214 214 chapter would not be necessary. Security issues are often vexing for a support person to resolve, not because 215 215 of the complexity of the problem, but because most administrators who post what turns out to be a security 216 216 problem request are totally convinced that the problem is with Samba. 217 </p><div class="sect2" title="Smbclient Works on Localhost, but the Network Is Dead"><div class="titlepage"><div><div><h3 class="title"><a name="id2625255"></a>Smbclient Works on Localhost, but the Network Is Dead</h3></div></div></div><p>217 </p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2619170"></a>Smbclient Works on Localhost, but the Network Is Dead</h3></div></div></div><p> 218 218 This is a common problem. Linux vendors tend to install a default firewall. 219 219 With the default firewall in place, only traffic on the loopback adapter (IP address 127.0.0.1) … … 223 223 allow SMB networking traffic through. See <a class="link" href="securing-samba.html#firewallports" title="Using a Firewall">the Using a 224 224 Firewall</a> section. 225 </p></div><div class="sect2" title="Why Can Users Access Other Users' Home Directories?"><div class="titlepage"><div><div><h3 class="title"><a name="id2625284"></a>Why Can Users Access Other Users' Home Directories?</h3></div></div></div><p>226 <span class="quote">“<span class="quote">227 <a class="indexterm" name="id26 25295"></a>228 <a class="indexterm" name="id26 25302"></a>225 </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2619198"></a>Why Can Users Access Other Users' Home Directories?</h3></div></div></div><p> 226 “<span class="quote"> 227 <a class="indexterm" name="id2619209"></a> 228 <a class="indexterm" name="id2619216"></a> 229 229 We are unable to keep individual users from mapping to any other user's home directory once they have 230 230 supplied a valid password! They only need to enter their own password. I have not found any method to 231 231 configure Samba so that users may map only their own home directory. 232 </span>” </span>233 </p><p> <span class="quote">“<span class="quote">232 </span>” 233 </p><p>“<span class="quote"> 234 234 User xyzzy can map his home directory. Once mapped, user xyzzy can also map anyone else's home directory. 235 </span>”</ span></p><p>236 <a class="indexterm" name="id26 25324"></a>237 <a class="indexterm" name="id26 25331"></a>235 </span>”</p><p> 236 <a class="indexterm" name="id2619238"></a> 237 <a class="indexterm" name="id2619245"></a> 238 238 This is not a security flaw, it is by design. Samba allows users to have exactly the same access to the UNIX 239 239 file system as when they were logged on to the UNIX box, except that it only allows such views onto the file 240 240 system as are allowed by the defined shares. 241 241 </p><p> 242 <a class="indexterm" name="id26 25345"></a>243 <a class="indexterm" name="id26 25352"></a>242 <a class="indexterm" name="id2619260"></a> 243 <a class="indexterm" name="id2619267"></a> 244 244 If your UNIX home directories are set up so that one user can happily <code class="literal">cd</code> 245 245 into another user's directory and execute <code class="literal">ls</code>, the UNIX security solution is to change file 246 246 permissions on the user's home directories so that the <code class="literal">cd</code> and <code class="literal">ls</code> are denied. 247 247 </p><p> 248 <a class="indexterm" name="id26 25390"></a>249 <a class="indexterm" name="id26 25397"></a>248 <a class="indexterm" name="id2619304"></a> 249 <a class="indexterm" name="id2619311"></a> 250 250 Samba tries very hard not to second guess the UNIX administrator's security policies and 251 251 trusts the UNIX admin to set the policies and permissions he or she desires. … … 256 256 The <a class="link" href="smb.conf.5.html#ONLYUSER" target="_top">only user</a> works in conjunction with the <a class="link" href="smb.conf.5.html#USERS" target="_top">users = list</a>, 257 257 so to get the behavior you require, add the line: 258 </p><table border="0" summary="Simple list" class="simplelist"><tr><td><a class="indexterm" name="id2625463"></a><em class="parameter"><code>users = %S</code></em></td></tr></table><p>258 </p><table class="simplelist" border="0" summary="Simple list"><tr><td><a class="indexterm" name="id2619377"></a><em class="parameter"><code>users = %S</code></em></td></tr></table><p> 259 259 This is equivalent to adding 260 </p><table border="0" summary="Simple list" class="simplelist"><tr><td><a class="indexterm" name="id2625480"></a><em class="parameter"><code>valid users = %S</code></em></td></tr></table><p>260 </p><table class="simplelist" border="0" summary="Simple list"><tr><td><a class="indexterm" name="id2619395"></a><em class="parameter"><code>valid users = %S</code></em></td></tr></table><p> 261 261 to the definition of the <em class="parameter"><code>[homes]</code></em> share, as recommended in 262 262 the <code class="filename">smb.conf</code> man page.
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