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diff --git a/doc/arm/Bv9ARM.ch07.html b/doc/arm/Bv9ARM.ch07.html new file mode 100644 index 0000000..c973734 --- /dev/null +++ b/doc/arm/Bv9ARM.ch07.html @@ -0,0 +1,254 @@ +<!-- + - Copyright (C) 2004-2008 Internet Systems Consortium, Inc. ("ISC") + - Copyright (C) 2000-2003 Internet Software Consortium. + - + - Permission to use, copy, modify, and distribute this software for any + - purpose with or without fee is hereby granted, provided that the above + - copyright notice and this permission notice appear in all copies. + - + - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH + - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY + - AND FITNESS. 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Troubleshooting"> +</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 7. <acronym class="acronym">BIND</acronym> 9 Security Considerations</th></tr> +<tr> +<td width="20%" align="left"> +<a accesskey="p" href="Bv9ARM.ch06.html">Prev</a> </td> +<th width="60%" align="center"> </th> +<td width="20%" align="right"> <a accesskey="n" href="Bv9ARM.ch08.html">Next</a> +</td> +</tr> +</table> +<hr> +</div> +<div class="chapter" lang="en"> +<div class="titlepage"><div><div><h2 class="title"> +<a name="Bv9ARM.ch07"></a>Chapter 7. <acronym class="acronym">BIND</acronym> 9 Security Considerations</h2></div></div></div> +<div class="toc"> +<p><b>Table of Contents</b></p> +<dl> +<dt><span class="sect1"><a href="Bv9ARM.ch07.html#Access_Control_Lists">Access Control Lists</a></span></dt> +<dt><span class="sect1"><a href="Bv9ARM.ch07.html#id2597645"><span><strong class="command">Chroot</strong></span> and <span><strong class="command">Setuid</strong></span></a></span></dt> +<dd><dl> +<dt><span class="sect2"><a href="Bv9ARM.ch07.html#id2597722">The <span><strong class="command">chroot</strong></span> Environment</a></span></dt> +<dt><span class="sect2"><a href="Bv9ARM.ch07.html#id2597782">Using the <span><strong class="command">setuid</strong></span> Function</a></span></dt> +</dl></dd> +<dt><span class="sect1"><a href="Bv9ARM.ch07.html#dynamic_update_security">Dynamic Update Security</a></span></dt> +</dl> +</div> +<div class="sect1" lang="en"> +<div class="titlepage"><div><div><h2 class="title" style="clear: both"> +<a name="Access_Control_Lists"></a>Access Control Lists</h2></div></div></div> +<p> + Access Control Lists (ACLs), are address match lists that + you can set up and nickname for future use in <span><strong class="command">allow-notify</strong></span>, + <span><strong class="command">allow-query</strong></span>, <span><strong class="command">allow-query-on</strong></span>, + <span><strong class="command">allow-recursion</strong></span>, <span><strong class="command">allow-recursion-on</strong></span>, + <span><strong class="command">blackhole</strong></span>, <span><strong class="command">allow-transfer</strong></span>, + etc. + </p> +<p> + Using ACLs allows you to have finer control over who can access + your name server, without cluttering up your config files with huge + lists of IP addresses. + </p> +<p> + It is a <span class="emphasis"><em>good idea</em></span> to use ACLs, and to + control access to your server. Limiting access to your server by + outside parties can help prevent spoofing and denial of service (DoS) attacks against + your server. + </p> +<p> + Here is an example of how to properly apply ACLs: + </p> +<pre class="programlisting"> +// Set up an ACL named "bogusnets" that will block RFC1918 space +// and some reserved space, which is commonly used in spoofing attacks. +acl bogusnets { + 0.0.0.0/8; 1.0.0.0/8; 2.0.0.0/8; 192.0.2.0/24; 224.0.0.0/3; + 10.0.0.0/8; 172.16.0.0/12; 192.168.0.0/16; +}; + +// Set up an ACL called our-nets. Replace this with the real IP numbers. +acl our-nets { x.x.x.x/24; x.x.x.x/21; }; +options { + ... + ... + allow-query { our-nets; }; + allow-recursion { our-nets; }; + ... + blackhole { bogusnets; }; + ... +}; + +zone "example.com" { + type master; + file "m/example.com"; + allow-query { any; }; +}; +</pre> +<p> + This allows recursive queries of the server from the outside + unless recursion has been previously disabled. + </p> +<p> + For more information on how to use ACLs to protect your server, + see the <span class="emphasis"><em>AUSCERT</em></span> advisory at: + </p> +<p> + <a href="ftp://ftp.auscert.org.au/pub/auscert/advisory/AL-1999.004.dns_dos" target="_top">ftp://ftp.auscert.org.au/pub/auscert/advisory/AL-1999.004.dns_dos</a> + </p> +</div> +<div class="sect1" lang="en"> +<div class="titlepage"><div><div><h2 class="title" style="clear: both"> +<a name="id2597645"></a><span><strong class="command">Chroot</strong></span> and <span><strong class="command">Setuid</strong></span> +</h2></div></div></div> +<p> + On UNIX servers, it is possible to run <acronym class="acronym">BIND</acronym> in a <span class="emphasis"><em>chrooted</em></span> environment + (using the <span><strong class="command">chroot()</strong></span> function) by specifying the "<code class="option">-t</code>" + option. This can help improve system security by placing <acronym class="acronym">BIND</acronym> in + a "sandbox", which will limit the damage done if a server is + compromised. + </p> +<p> + Another useful feature in the UNIX version of <acronym class="acronym">BIND</acronym> is the + ability to run the daemon as an unprivileged user ( <code class="option">-u</code> <em class="replaceable"><code>user</code></em> ). + We suggest running as an unprivileged user when using the <span><strong class="command">chroot</strong></span> feature. + </p> +<p> + Here is an example command line to load <acronym class="acronym">BIND</acronym> in a <span><strong class="command">chroot</strong></span> sandbox, + <span><strong class="command">/var/named</strong></span>, and to run <span><strong class="command">named</strong></span> <span><strong class="command">setuid</strong></span> to + user 202: + </p> +<p> + <strong class="userinput"><code>/usr/local/bin/named -u 202 -t /var/named</code></strong> + </p> +<div class="sect2" lang="en"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="id2597722"></a>The <span><strong class="command">chroot</strong></span> Environment</h3></div></div></div> +<p> + In order for a <span><strong class="command">chroot</strong></span> environment + to + work properly in a particular directory + (for example, <code class="filename">/var/named</code>), + you will need to set up an environment that includes everything + <acronym class="acronym">BIND</acronym> needs to run. + From <acronym class="acronym">BIND</acronym>'s point of view, <code class="filename">/var/named</code> is + the root of the filesystem. You will need to adjust the values of + options like + like <span><strong class="command">directory</strong></span> and <span><strong class="command">pid-file</strong></span> to account + for this. + </p> +<p> + Unlike with earlier versions of BIND, you typically will + <span class="emphasis"><em>not</em></span> need to compile <span><strong class="command">named</strong></span> + statically nor install shared libraries under the new root. + However, depending on your operating system, you may need + to set up things like + <code class="filename">/dev/zero</code>, + <code class="filename">/dev/random</code>, + <code class="filename">/dev/log</code>, and + <code class="filename">/etc/localtime</code>. + </p> +</div> +<div class="sect2" lang="en"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="id2597782"></a>Using the <span><strong class="command">setuid</strong></span> Function</h3></div></div></div> +<p> + Prior to running the <span><strong class="command">named</strong></span> daemon, + use + the <span><strong class="command">touch</strong></span> utility (to change file + access and + modification times) or the <span><strong class="command">chown</strong></span> + utility (to + set the user id and/or group id) on files + to which you want <acronym class="acronym">BIND</acronym> + to write. + </p> +<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> +<h3 class="title">Note</h3> + Note that if the <span><strong class="command">named</strong></span> daemon is running as an + unprivileged user, it will not be able to bind to new restricted + ports if the server is reloaded. + </div> +</div> +</div> +<div class="sect1" lang="en"> +<div class="titlepage"><div><div><h2 class="title" style="clear: both"> +<a name="dynamic_update_security"></a>Dynamic Update Security</h2></div></div></div> +<p> + Access to the dynamic + update facility should be strictly limited. In earlier versions of + <acronym class="acronym">BIND</acronym>, the only way to do this was + based on the IP + address of the host requesting the update, by listing an IP address + or + network prefix in the <span><strong class="command">allow-update</strong></span> + zone option. + This method is insecure since the source address of the update UDP + packet + is easily forged. Also note that if the IP addresses allowed by the + <span><strong class="command">allow-update</strong></span> option include the + address of a slave + server which performs forwarding of dynamic updates, the master can + be + trivially attacked by sending the update to the slave, which will + forward it to the master with its own source IP address causing the + master to approve it without question. + </p> +<p> + For these reasons, we strongly recommend that updates be + cryptographically authenticated by means of transaction signatures + (TSIG). That is, the <span><strong class="command">allow-update</strong></span> + option should + list only TSIG key names, not IP addresses or network + prefixes. Alternatively, the new <span><strong class="command">update-policy</strong></span> + option can be used. + </p> +<p> + Some sites choose to keep all dynamically-updated DNS data + in a subdomain and delegate that subdomain to a separate zone. This + way, the top-level zone containing critical data such as the IP + addresses + of public web and mail servers need not allow dynamic update at + all. + </p> +</div> +</div> +<div class="navfooter"> +<hr> +<table width="100%" summary="Navigation footer"> +<tr> +<td width="40%" align="left"> +<a accesskey="p" href="Bv9ARM.ch06.html">Prev</a> </td> +<td width="20%" align="center"> </td> +<td width="40%" align="right"> <a accesskey="n" href="Bv9ARM.ch08.html">Next</a> +</td> +</tr> +<tr> +<td width="40%" align="left" valign="top">Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference </td> +<td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td> +<td width="40%" align="right" valign="top"> Chapter 8. Troubleshooting</td> +</tr> +</table> +</div> +</body> +</html> |