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| author | Gerald Carter <jerry@samba.org> | 2003-09-09 02:58:53 +0000 |
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| committer | Gerald Carter <jerry@samba.org> | 2003-09-09 02:58:53 +0000 |
| commit | 99bde6889d3d8b7a9e950c86c30e82662e1dacdd (patch) | |
| tree | bb7d34722e3b2b98ae7e36c11f4e7e4d4538b6fb /docs/htmldocs/securing-samba.html | |
| parent | a50367ee119d0acf1bcaaf93f8c6fcc8fa68c999 (diff) | |
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syncing files from 3.0 into HEAD again
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diff --git a/docs/htmldocs/securing-samba.html b/docs/htmldocs/securing-samba.html index a790816d02..492780765e 100644 --- a/docs/htmldocs/securing-samba.html +++ b/docs/htmldocs/securing-samba.html @@ -1,4 +1,4 @@ -<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 15. Securing Samba</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.60.1"><link rel="home" href="index.html" title="SAMBA Project Documentation"><link rel="up" href="optional.html" title="Part III. Advanced Configuration"><link rel="previous" href="locking.html" title="Chapter 14. File and Record Locking"><link rel="next" href="InterdomainTrusts.html" title="Chapter 16. 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 15. 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 15. 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><tt class="email"><<a href="mailto:tridge@samba.org">tridge@samba.org</a>></tt></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><tt class="email"><<a href="mailto:jht@samba.org">jht@samba.org</a>></tt></p></div></div></div></div><div><p class="pubdate">May 26, 2003</p></div></div><div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="securing-samba.html#id2931943">Introduction</a></dt><dt><a href="securing-samba.html#id2931976">Features and Benefits</a></dt><dt><a href="securing-samba.html#id2932050">Technical Discussion of Protective Measures and Issues</a></dt><dd><dl><dt><a href="securing-samba.html#id2932069">Using host based protection</a></dt><dt><a href="securing-samba.html#id2932140">User based protection</a></dt><dt><a href="securing-samba.html#id2932191">Using interface protection</a></dt><dt><a href="securing-samba.html#id2932244">Using a firewall</a></dt><dt><a href="securing-samba.html#id2932300">Using a IPC$ share deny</a></dt><dt><a href="securing-samba.html#id2932362">NTLMv2 Security</a></dt></dl></dd><dt><a href="securing-samba.html#id2932402">Upgrading Samba</a></dt><dt><a href="securing-samba.html#id2932426">Common Errors</a></dt><dd><dl><dt><a href="securing-samba.html#id2932444">Smbclient works on localhost, but the network is dead</a></dt><dt><a href="securing-samba.html#id2932469">Why can users access home directories of other users?</a></dt></dl></dd></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2931943"></a>Introduction</h2></div></div><div></div></div><p> +<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 15. Securing Samba</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.60.1"><link rel="home" href="samba-doc.html" title="SAMBA Project Documentation"><link rel="up" href="optional.html" title="Part III. Advanced Configuration"><link rel="previous" href="locking.html" title="Chapter 14. File and Record Locking"><link rel="next" href="InterdomainTrusts.html" title="Chapter 16. 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 15. 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 15. 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><tt class="email"><<a href="mailto:tridge@samba.org">tridge@samba.org</a>></tt></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><tt class="email"><<a href="mailto:jht@samba.org">jht@samba.org</a>></tt></p></div></div></div></div><div><p class="pubdate">May 26, 2003</p></div></div><div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="securing-samba.html#id2910685">Introduction</a></dt><dt><a href="securing-samba.html#id2910722">Features and Benefits</a></dt><dt><a href="securing-samba.html#id2910796">Technical Discussion of Protective Measures and Issues</a></dt><dd><dl><dt><a href="securing-samba.html#id2910816">Using host based protection</a></dt><dt><a href="securing-samba.html#id2910915">User based protection</a></dt><dt><a href="securing-samba.html#id2910975">Using interface protection</a></dt><dt><a href="securing-samba.html#id2911042">Using a firewall</a></dt><dt><a href="securing-samba.html#id2911098">Using a IPC$ share deny</a></dt><dt><a href="securing-samba.html#id2911187">NTLMv2 Security</a></dt></dl></dd><dt><a href="securing-samba.html#id2911245">Upgrading Samba</a></dt><dt><a href="securing-samba.html#id2911271">Common Errors</a></dt><dd><dl><dt><a href="securing-samba.html#id2911289">Smbclient works on localhost, but the network is dead</a></dt><dt><a href="securing-samba.html#id2911314">Why can users access home directories of other users?</a></dt></dl></dd></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2910685"></a>Introduction</h2></div></div><div></div></div><p> This note was attached to the Samba 2.2.8 release notes as it contained an important security fix. The information contained here applies to Samba installations in general. @@ -10,7 +10,7 @@ on it!" Security concerns are just like that: You need to know a little about the subject to appreciate how obvious most of it really is. The challenge for most of us is to discover that first morsel of knowledge with which we may unlock the secrets of the masters. -</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2931976"></a>Features and Benefits</h2></div></div><div></div></div><p> +</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2910722"></a>Features and Benefits</h2></div></div><div></div></div><p> There are three level at which security principals must be observed in order to render a site at least moderately secure. These are: the perimeter firewall, the configuration of the host server that is running Samba, and Samba itself. @@ -22,58 +22,50 @@ Samba may be secured from connections that originate from outside the local netw done using <span class="emphasis"><em>host based protection</em></span> (using samba's implementation of a technology known as "tcpwrappers", or it may be done be using <span class="emphasis"><em>interface based exclusion</em></span> so that <span class="application">smbd</span> will bind only to specifically permitted interfaces. It is also -possible to set specific share or resource based exclusions, eg: on the <i class="parameter"><tt>IPC$</tt></i> -auto-share. The <i class="parameter"><tt>IPC$</tt></i> share is used for browsing purposes as well as to establish +possible to set specific share or resource based exclusions, eg: on the <i class="parameter"><tt>[IPC$]</tt></i> +auto-share. The <i class="parameter"><tt>[IPC$]</tt></i> share is used for browsing purposes as well as to establish TCP/IP connections. </p><p> Another method by which Samba may be secured is by way of setting Access Control Entries in an Access Control List on the shares themselves. This is discussed in the chapter on File, Directory and Share Access Control. -</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2932050"></a>Technical Discussion of Protective Measures and Issues</h2></div></div><div></div></div><p> +</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2910796"></a>Technical Discussion of Protective Measures and Issues</h2></div></div><div></div></div><p> The key challenge of security is the fact that protective measures suffice at best only to close the door on known exploits and breach techniques. Never assume that because you have followed these few measures that the Samba server is now an impenetrable fortress! Given the history of information systems so far, it is only a matter of time before someone will find yet another vulnerability. -</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2932069"></a>Using host based protection</h3></div></div><div></div></div><p> +</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2910816"></a>Using host based protection</h3></div></div><div></div></div><p> In many installations of Samba the greatest threat comes for outside your immediate network. By default Samba will accept connections from any host, which means that if you run an insecure version of Samba on a host that is directly connected to the Internet you can be especially vulnerable. </p><p> - One of the simplest fixes in this case is to use the <i class="parameter"><tt>hosts allow</tt></i> and - <i class="parameter"><tt>hosts deny</tt></i> options in the Samba <tt class="filename">smb.conf</tt> configuration file to only + One of the simplest fixes in this case is to use the <a class="indexterm" name="id2910838"></a><i class="parameter"><tt>hosts allow</tt></i> and + <a class="indexterm" name="id2910852"></a><i class="parameter"><tt>hosts deny</tt></i> options in the Samba <tt class="filename">smb.conf</tt> configuration file to only allow access to your server from a specific range of hosts. An example might be: - </p><pre class="programlisting"> - hosts allow = 127.0.0.1 192.168.2.0/24 192.168.3.0/24 - hosts deny = 0.0.0.0/0 - </pre><p> + </p><table class="simplelist" border="0" summary="Simple list"><tr><td><i class="parameter"><tt>hosts allow = 127.0.0.1 192.168.2.0/24 192.168.3.0/24</tt></i></td></tr><tr><td><i class="parameter"><tt>hosts deny = 0.0.0.0/0</tt></i></td></tr></table><p> The above will only allow SMB connections from 'localhost' (your own computer) and from the two private networks 192.168.2 and 192.168.3. All other connections will be refused as soon as the client sends its first packet. The refusal will be marked as a <span class="errorname">not listening on called name</span> error. - </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2932140"></a>User based protection</h3></div></div><div></div></div><p> + </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2910915"></a>User based protection</h3></div></div><div></div></div><p> If you want to restrict access to your server to valid users only then the following - method may be of use. In the <tt class="filename">smb.conf</tt> <i class="parameter"><tt>[globals]</tt></i> section put: - </p><pre class="programlisting"> - valid users = @smbusers, jacko - </pre><p> + method may be of use. In the <tt class="filename">smb.conf</tt> <i class="parameter"><tt>[global]</tt></i> section put: + </p><table class="simplelist" border="0" summary="Simple list"><tr><td><i class="parameter"><tt>valid users = @smbusers, jacko</tt></i></td></tr></table><p> What this does is, it restricts all server access to either the user <span class="emphasis"><em>jacko</em></span> or to members of the system group <span class="emphasis"><em>smbusers</em></span>. - </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2932191"></a>Using interface protection</h3></div></div><div></div></div><p> + </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2910975"></a>Using interface protection</h3></div></div><div></div></div><p> By default Samba will accept connections on any network interface that it finds on your system. That means if you have a ISDN line or a PPP connection to the Internet then Samba will accept connections on those links. This may not be what you want. </p><p> You can change this behaviour using options like the following: - </p><pre class="programlisting"> - interfaces = eth* lo - bind interfaces only = yes - </pre><p> + </p><table class="simplelist" border="0" summary="Simple list"><tr><td><i class="parameter"><tt>interfaces = eth* lo</tt></i></td></tr><tr><td><i class="parameter"><tt>bind interfaces only = yes</tt></i></td></tr></table><p> This tells Samba to only listen for connections on interfaces with a name starting with 'eth' such as eth0, eth1, plus on the loopback interface called 'lo'. The name you will need to use depends on what @@ -85,7 +77,7 @@ before someone will find yet another vulnerability. connection refused reply. In that case no Samba code is run at all as the operating system has been told not to pass connections from that interface to any samba process. - </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2932244"></a>Using a firewall</h3></div></div><div></div></div><p> + </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2911042"></a>Using a firewall</h3></div></div><div></div></div><p> Many people use a firewall to deny access to services that they don't want exposed outside their network. This can be a very good idea, although I would recommend using it in conjunction with the above @@ -98,7 +90,7 @@ before someone will find yet another vulnerability. The last one is important as many older firewall setups may not be aware of it, given that this port was only added to the protocol in recent years. - </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2932300"></a>Using a IPC$ share deny</h3></div></div><div></div></div><p> + </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2911098"></a>Using a IPC$ share deny</h3></div></div><div></div></div><p> If the above methods are not suitable, then you could also place a more specific deny on the IPC$ share that is used in the recently discovered security hole. This allows you to offer access to other @@ -106,11 +98,7 @@ before someone will find yet another vulnerability. hosts. </p><p> To do that you could use: - </p><pre class="programlisting"> -[ipc$] - hosts allow = 192.168.115.0/24 127.0.0.1 - hosts deny = 0.0.0.0/0 - </pre><p> + </p><table class="simplelist" border="0" summary="Simple list"><tr><td> </td></tr><tr><td><i class="parameter"><tt>[ipc$]</tt></i></td></tr><tr><td><i class="parameter"><tt>hosts allow = 192.168.115.0/24 127.0.0.1</tt></i></td></tr><tr><td><i class="parameter"><tt>hosts deny = 0.0.0.0/0</tt></i></td></tr></table><p> this would tell Samba that IPC$ connections are not allowed from anywhere but the two listed places (localhost and a local subnet). Connections to other shares would still be allowed. As the @@ -125,42 +113,44 @@ before someone will find yet another vulnerability. </p><p> This is not recommended unless you cannot use one of the other methods listed above for some reason. - </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2932362"></a>NTLMv2 Security</h3></div></div><div></div></div><p> + </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2911187"></a>NTLMv2 Security</h3></div></div><div></div></div><p> To configure NTLMv2 authentication the following registry keys are worth knowing about: </p><p> - </p><pre class="screen"> + </p><pre class="screen"> [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa] "lmcompatibilitylevel"=dword:00000003 - + </pre><p> + </p><p> 0x3 - Send NTLMv2 response only. Clients will use NTLMv2 authentication, use NTLMv2 session security if the server supports it. Domain controllers accept LM, NTLM and NTLMv2 authentication. - + </p><p> + </p><pre class="screen"> [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0] "NtlmMinClientSec"=dword:00080000 - + </pre><p> + </p><p> 0x80000 - NTLMv2 session security. If either NtlmMinClientSec or NtlmMinServerSec is set to 0x80000, the connection will fail if NTLMv2 session security is not negotiated. - </pre><p> - </p></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2932402"></a>Upgrading Samba</h2></div></div><div></div></div><p> + </p></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2911245"></a>Upgrading Samba</h2></div></div><div></div></div><p> Please check regularly on <a href="http://www.samba.org/" target="_top">http://www.samba.org/</a> for updates and important announcements. Occasionally security releases are made and it is highly recommended to upgrade Samba when a security vulnerability -is discovered. -</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2932426"></a>Common Errors</h2></div></div><div></div></div><p> +is discovered. Check with your OS vendor for OS specific upgrades. +</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2911271"></a>Common Errors</h2></div></div><div></div></div><p> If all of samba and host platform configuration were really as intuitive as one might like then this section would not be necessary. Security issues are often vexing for a support person to resolve, not because of the complexity of the problem, but for reason that most administrators who post what turns out to be a security problem request are totally convinced that the problem is with Samba. -</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2932444"></a>Smbclient works on localhost, but the network is dead</h3></div></div><div></div></div><p> +</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2911289"></a>Smbclient works on localhost, but the network is dead</h3></div></div><div></div></div><p> This is a very common problem. Red Hat Linux (as do others) will install a default firewall. With the default firewall in place only traffic on the loopback adapter (IP address 127.0.0.1) will be allowed through the firewall. </p><p> The solution is either to remove the firewall (stop it) or to modify the firewall script to allow SMB networking traffic through. See section above in this chapter. - </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2932469"></a>Why can users access home directories of other users?</h3></div></div><div></div></div><p> + </p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2911314"></a>Why can users access home directories of other users?</h3></div></div><div></div></div><p> “<span class="quote"> We are unable to keep individual users from mapping to any other user's home directory once they have supplied a valid password! They only need @@ -189,18 +179,14 @@ out to be a security problem request are totally convinced that the problem is w the policies and permissions he or she desires. </p><p> Samba does allow the setup you require when you have set the - <i class="parameter"><tt>only user = yes</tt></i> option on the share, is that you have not set the + <a class="indexterm" name="id2911373"></a><i class="parameter"><tt>only user</tt></i> = yes option on the share, is that you have not set the valid users list for the share. </p><p> Note that only user works in conjunction with the users= list, so to get the behavior you require, add the line : - </p><pre class="programlisting"> - users = %S - </pre><p> + </p><table class="simplelist" border="0" summary="Simple list"><tr><td><i class="parameter"><tt>users = %S</tt></i></td></tr></table><p> this is equivalent to: - </p><pre class="programlisting"> - valid users = %S - </pre><p> + </p><table class="simplelist" border="0" summary="Simple list"><tr><td><i class="parameter"><tt>valid users = %S</tt></i></td></tr></table><p> to the definition of the <i class="parameter"><tt>[homes]</tt></i> share, as recommended in the <tt class="filename">smb.conf</tt> man page. - </p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="locking.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="optional.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="InterdomainTrusts.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 14. File and Record Locking </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 16. Interdomain Trust Relationships</td></tr></table></div></body></html> + </p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="locking.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="optional.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="InterdomainTrusts.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 14. File and Record Locking </td><td width="20%" align="center"><a accesskey="h" href="samba-doc.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 16. Interdomain Trust Relationships</td></tr></table></div></body></html> |