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28 KiB
HTML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><link rel="stylesheet" type="text/css" href="libvirt.css" /><link rel="SHORTCUT ICON" href="/32favicon.png" /><title>Remote support</title></head><body><div id="container"><div id="intro"><div id="adjustments"></div><div id="pageHeader"></div><div id="content2"><h1 class="style1">Remote support</h1><p>
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Libvirt allows you to access hypervisors running on remote
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machines through authenticated and encrypted connections.
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</p><ul><li><a href="#Remote_basic_usage">Basic usage</a></li>
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<li><a href="#Remote_transports">Transports</a></li>
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<li><a href="#Remote_URI_reference">Remote URIs</a>
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<ul><li><a href="#Remote_URI_parameters">Extra parameters</a></li>
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</ul></li>
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<li><a href="#Remote_certificates">Generating TLS certificates</a>
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<ul><li><a href="#Remote_PKI">Public Key Infrastructure set up</a></li>
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<li><a href="#Remote_TLS_background">Background to TLS certificates</a></li>
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<li><a href="#Remote_TLS_CA">Setting up a Certificate Authority (CA)</a></li>
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<li><a href="#Remote_TLS_server_certificates">Issuing server certificates</a></li>
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<li><a href="#Remote_TLS_client_certificates">Issuing client certificates</a></li>
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<li><a href="#Remote_TLS_troubleshooting">Troubleshooting TLS certificate problems</a></li>
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</ul></li>
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<li><a href="#Remote_libvirtd_configuration">libvirtd configuration file</a></li>
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<li><a href="#Remote_IPv6">IPv6 support</a></li>
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<li><a href="#Remote_limitations">Limitations</a></li>
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<li><a href="#Remote_implementation_notes">Implementation notes</a></li>
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</ul><h3><a name="Remote_basic_usage" id="Remote_basic_usage">Basic usage</a></h3><p>
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On the remote machine, <code>libvirtd</code> should be running.
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See <a href="#Remote_libvirtd_configuration">the section
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on configuring libvirtd</a> for more information.
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</p><p>
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To tell libvirt that you want to access a remote resource,
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you should supply a hostname in the normal <a href="uri.html">URI</a> that is passed
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to <code>virConnectOpen</code> (or <code>virsh -c ...</code>).
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For example, if you normally use <code>qemu:///system</code>
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to access the system-wide QEMU daemon, then to access
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the system-wide QEMU daemon on a remote machine called
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<code>oirase</code> you would use <code>qemu://oirase/system</code>.
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</p><p>
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The <a href="#Remote_URI_reference">section on remote URIs</a>
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describes in more detail these remote URIs.
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</p><p>
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From an API point of view, apart from the change in URI, the
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API should behave the same. For example, ordinary calls
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are routed over the remote connection transparently, and
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values or errors from the remote side are returned to you
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as if they happened locally. Some differences you may notice:
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</p><ul><li> Additional errors can be generated, specifically ones
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relating to failures in the remote transport itself. </li>
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<li> Remote calls are handled synchronously, so they will be
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much slower than, say, direct hypervisor calls. </li>
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</ul><h3><a name="Remote_transports" id="Remote_transports">Transports</a></h3><p>
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Remote libvirt supports a range of transports:
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</p><dl><dt> tls </dt>
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<dd> <a href="http://en.wikipedia.org/wiki/Transport_Layer_Security" title="Transport Layer Security">TLS</a>
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1.0 (SSL 3.1) authenticated and encrypted TCP/IP socket, usually
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listening on a public port number. To use this you will need to
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<a href="#Remote_certificates" title="Generating TLS certificates">generate client and
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server certificates</a>.
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The standard port is 16514.
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</dd>
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<dt> unix </dt>
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<dd> Unix domain socket. Since this is only accessible on the
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local machine, it is not encrypted, and uses Unix permissions or
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SELinux for authentication.
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The standard socket names are
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<code>/var/run/libvirt/libvirt-sock</code> and
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<code>/var/run/libvirt/libvirt-sock-ro</code> (the latter
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for read-only connections).
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</dd>
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<dt> ssh </dt>
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<dd> Transported over an ordinary
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<a href="http://www.openssh.com/" title="OpenSSH homepage">ssh
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(secure shell)</a> connection.
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Requires <a href="http://netcat.sourceforge.net/">Netcat (nc)</a>
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installed on the remote machine, and the remote libvirtd should
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be listening on the unix transport. You should use some sort of
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ssh key management (eg.
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<a href="http://mah.everybody.org/docs/ssh" title="Using ssh-agent with ssh">ssh-agent</a>)
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otherwise programs which use
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this transport will stop to ask for a password. </dd>
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<dt> ext </dt>
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<dd> Any external program which can make a connection to the
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remote machine by means outside the scope of libvirt. </dd>
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<dt> tcp </dt>
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<dd> Unencrypted TCP/IP socket. Not recommended for production
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use, this is normally disabled, but an administrator can enable
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it for testing or use over a trusted network.
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The standard port is 16509.
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</dd>
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</dl><p>
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The default transport, if no other is specified, is <code>tls</code>.
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</p><h3><a name="Remote_URI_reference" id="Remote_URI_reference">Remote URIs</a></h3><p>
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See also: <a href="uri.html">documentation on ordinary ("local") URIs</a>.
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</p><p>
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Remote URIs have the general form ("[...]" meaning an optional part):
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</p><p>
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<code>driver</code>[<code>+transport</code>]<code>://</code>[<code>username@</code>][<code>hostname</code>][<code>:port</code>]<code>/</code>[<code>path</code>][<code>?extraparameters</code>]
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</p><p>
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Either the transport or the hostname must be given in order
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to distinguish this from a local URI.
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</p><p>
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Some examples:
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</p><ul><li> <code>xen+ssh://rjones@towada/</code> <br /> — Connect to a
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remote Xen hypervisor on host <code>towada</code> using ssh transport and ssh
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username <code>rjones</code>.
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</li>
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<li> <code>xen://towada/</code> <br /> — Connect to a
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remote Xen hypervisor on host <code>towada</code> using TLS.
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</li>
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<li> <code>xen://towada/?no_verify=1</code> <br /> — Connect to a
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remote Xen hypervisor on host <code>towada</code> using TLS. Do not verify
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the server's certificate.
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</li>
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<li> <code>qemu+unix:///system?socket=/opt/libvirt/run/libvirt/libvirt-sock</code> <br /> —
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Connect to the local qemu instances over a non-standard
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Unix socket (the full path to the Unix socket is
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supplied explicitly in this case).
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</li>
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<li> <code>test+tcp://localhost:5000/default</code> <br /> —
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Connect to a libvirtd daemon offering unencrypted TCP/IP connections
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on localhost port 5000 and use the test driver with default
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settings.
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</li>
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</ul><h4><a name="Remote_URI_parameters" id="Remote_URI_parameters">Extra parameters</a></h4><p>
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Extra parameters can be added to remote URIs as part
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of the query string (the part following <q><code>?</code></q>).
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Remote URIs understand the extra parameters shown below.
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Any others are passed unmodified through to the back end.
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Note that parameter values must be
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<a href="http://xmlsoft.org/html/libxml-uri.html#xmlURIEscapeStr">URI-escaped</a>.
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</p><table class="top_table"><tr><th> Name </th>
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<th> Transports </th>
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<th> Meaning </th>
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</tr><tr><td> <code>name</code> </td>
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<td> <i>any transport</i> </td>
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<td>
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The name passed to the remote virConnectOpen function. The
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name is normally formed by removing transport, hostname, port
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number, username and extra parameters from the remote URI, but in certain
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very complex cases it may be better to supply the name explicitly.
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</td>
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</tr><tr><td colspan="2"></td>
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<td> Example: <code>name=qemu:///system</code> </td>
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</tr><tr><td> <code>command</code> </td>
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<td> ssh, ext </td>
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<td>
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The external command. For ext transport this is required.
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For ssh the default is <code>ssh</code>.
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The PATH is searched for the command.
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</td>
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</tr><tr><td colspan="2"></td>
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<td> Example: <code>command=/opt/openssh/bin/ssh</code> </td>
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</tr><tr><td> <code>socket</code> </td>
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<td> unix, ssh </td>
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<td>
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The path to the Unix domain socket, which overrides the
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compiled-in default. For ssh transport, this is passed to
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the remote netcat command (see next).
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</td>
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</tr><tr><td colspan="2"></td>
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<td> Example: <code>socket=/opt/libvirt/run/libvirt/libvirt-sock</code> </td>
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</tr><tr><td> <code>netcat</code> </td>
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<td> ssh </td>
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<td>
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The name of the netcat command on the remote machine.
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The default is <code>nc</code>. For ssh transport, libvirt
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constructs an ssh command which looks like:
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<pre>
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<i>command</i> -p <i>port</i> [-l <i>username</i>] <i>hostname</i> <i>netcat</i> -U <i>socket</i>
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</pre>
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where <i>port</i>, <i>username</i>, <i>hostname</i> can be
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specified as part of the remote URI, and <i>command</i>, <i>netcat</i>
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and <i>socket</i> come from extra parameters (or
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sensible defaults).
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</td>
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</tr><tr><td colspan="2"></td>
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<td> Example: <code>netcat=/opt/netcat/bin/nc</code> </td>
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</tr><tr><td> <code>no_verify</code> </td>
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<td> tls </td>
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<td>
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If set to a non-zero value, this disables client checks of the
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server's certificate. Note that to disable server checks of
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the client's certificate or IP address you must
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<a href="#Remote_libvirtd_configuration">change the libvirtd
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configuration</a>.
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</td>
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</tr><tr><td colspan="2"></td>
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<td> Example: <code>no_verify=1</code> </td>
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</tr></table><h3><a name="Remote_certificates" id="Remote_certificates">Generating TLS certificates</a></h3><h4><a name="Remote_PKI" id="Remote_PKI">Public Key Infrastructure set up</a></h4><p>
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If you are unsure how to create TLS certificates, skip to the
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next section.
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</p><table class="top_table"><tr><th> Location </th>
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<th> Machine </th>
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<th> Description </th>
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<th> Required fields </th>
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</tr><tr><td> <code>/etc/pki/CA/cacert.pem</code> </td>
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<td> Installed on all clients and servers </td>
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<td> CA's certificate (<a href="#Remote_TLS_CA">more info</a>)</td>
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<td> n/a </td>
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</tr><tr><td> <code>/etc/pki/libvirt/ private/serverkey.pem</code> </td>
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<td> Installed on the server </td>
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<td> Server's private key (<a href="#Remote_TLS_server_certificates">more info</a>)</td>
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<td> n/a </td>
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</tr><tr><td> <code>/etc/pki/libvirt/ servercert.pem</code> </td>
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<td> Installed on the server </td>
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<td> Server's certificate signed by the CA.
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(<a href="#Remote_TLS_server_certificates">more info</a>) </td>
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<td> CommonName (CN) must be the hostname of the server as it
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is seen by clients. </td>
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</tr><tr><td> <code>/etc/pki/libvirt/ private/clientkey.pem</code> </td>
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<td> Installed on the client </td>
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<td> Client's private key. (<a href="#Remote_TLS_client_certificates">more info</a>) </td>
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<td> n/a </td>
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</tr><tr><td> <code>/etc/pki/libvirt/ clientcert.pem</code> </td>
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<td> Installed on the client </td>
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<td> Client's certificate signed by the CA
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(<a href="#Remote_TLS_client_certificates">more info</a>) </td>
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<td> Distinguished Name (DN) can be checked against an access
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control list (<code>tls_allowed_dn_list</code>).
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</td>
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</tr></table><h4><a name="Remote_TLS_background" id="Remote_TLS_background">Background to TLS certificates</a></h4><p>
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Libvirt supports TLS certificates for verifying the identity
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of the server and clients. There are two distinct checks involved:
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</p><ul><li> The client should know that it is connecting to the right
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server. Checking done by client by matching the certificate that
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the server sends to the server's hostname. May be disabled by adding
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<code>?no_verify=1</code> to the
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<a href="#Remote_URI_parameters">remote URI</a>.
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</li>
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<li> The server should know that only permitted clients are
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connecting. This can be done based on client's IP address, or on
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client's IP address and client's certificate. Checking done by the
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server. May be enabled and disabled in the <a href="#Remote_libvirtd_configuration">libvirtd.conf file</a>.
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</li>
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</ul><p>
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For full certificate checking you will need to have certificates
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issued by a recognised <a href="http://en.wikipedia.org/wiki/Certificate_authority">Certificate
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Authority (CA)</a> for your server(s) and all clients. To avoid the
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expense of getting certificates from a commercial CA, you can set up
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your own CA and tell your server(s) and clients to trust certificates
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issues by your own CA. Follow the instructions in the next section.
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</p><p>
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Be aware that the <a href="#Remote_libvirtd_configuration">default
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configuration for libvirtd</a> allows any client to connect provided
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they have a valid certificate issued by the CA for their own IP
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address. You may want to change this to make it less (or more)
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permissive, depending on your needs.
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</p><h4><a name="Remote_TLS_CA" id="Remote_TLS_CA">Setting up a Certificate Authority (CA)</a></h4><p>
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You will need the <a href="http://www.gnu.org/software/gnutls/manual/html_node/Invoking-certtool.html">GnuTLS
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certtool program documented here</a>. In Fedora, it is in the
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<code>gnutls-utils</code> package.
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</p><p>
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Create a private key for your CA:
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</p><pre>
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certtool --generate-privkey > cakey.pem
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</pre><p>
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and self-sign it by creating a file with the
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signature details called
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<code>ca.info</code> containing:
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</p><pre>
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cn = <i>Name of your organization</i>
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ca
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cert_signing_key
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</pre><pre>
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certtool --generate-self-signed --load-privkey cakey.pem \
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--template ca.info --outfile cacert.pem
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</pre><p>
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(You can delete <code>ca.info</code> file now if you
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want).
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</p><p>
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Now you have two files which matter:
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</p><ul><li>
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<code>cakey.pem</code> - Your CA's private key (keep this very secret!)
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</li>
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<li>
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<code>cacert.pem</code> - Your CA's certificate (this is public).
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</li>
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</ul><p>
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<code>cacert.pem</code> has to be installed on clients and
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server(s) to let them know that they can trust certificates issued by
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your CA.
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</p><p>
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The normal installation directory for <code>cacert.pem</code>
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is <code>/etc/pki/CA/cacert.pem</code> on all clients and servers.
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</p><p>
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To see the contents of this file, do:
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</p><pre>
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<b>certtool -i --infile cacert.pem</b>
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X.509 certificate info:
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Version: 3
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Serial Number (hex): 00
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Subject: CN=Red Hat Emerging Technologies
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Issuer: CN=Red Hat Emerging Technologies
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Signature Algorithm: RSA-SHA
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Validity:
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Not Before: Mon Jun 18 16:22:18 2007
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Not After: Tue Jun 17 16:22:18 2008
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<i>[etc]</i>
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</pre><p>
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This is all that is required to set up your CA. Keep the CA's private
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key carefully as you will need it when you come to issue certificates
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for your clients and servers.
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</p><h4><a name="Remote_TLS_server_certificates" id="Remote_TLS_server_certificates">Issuing server certificates</a></h4><p>
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For each server (libvirtd) you need to issue a certificate
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with the X.509 CommonName (CN) field set to the hostname
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of the server. The CN must match the hostname which
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clients will be using to connect to the server.
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</p><p>
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In the example below, clients will be connecting to the
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server using a <a href="#Remote_URI_reference">URI</a> of
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<code>xen://oirase/</code>, so the CN must be "<code>oirase</code>".
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</p><p>
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Make a private key for the server:
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</p><pre>
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certtool --generate-privkey > serverkey.pem
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</pre><p>
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and sign that key with the CA's private key by first
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creating a template file called <code>server.info</code>
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(only the CN field matters, which as explained above must
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be the server's hostname):
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</p><pre>
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organization = <i>Name of your organization</i>
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cn = oirase
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tls_www_server
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encryption_key
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signing_key
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</pre><p>
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and sign:
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</p><pre>
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certtool --generate-certificate --load-privkey serverkey.pem \
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--load-ca-certificate cacert.pem --load-ca-privkey cakey.pem \
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--template server.info --outfile servercert.pem
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</pre><p>
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This gives two files:
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</p><ul><li>
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<code>serverkey.pem</code> - The server's private key.
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</li>
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<li>
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<code>servercert.pem</code> - The server's public key.
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</li>
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</ul><p>
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We can examine this certificate and its signature:
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</p><pre>
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<b>certtool -i --infile servercert.pem</b>
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X.509 certificate info:
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Version: 3
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Serial Number (hex): 00
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Subject: O=Red Hat Emerging Technologies,CN=oirase
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Issuer: CN=Red Hat Emerging Technologies
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Signature Algorithm: RSA-SHA
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Validity:
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Not Before: Mon Jun 18 16:34:49 2007
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Not After: Tue Jun 17 16:34:49 2008
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</pre><p>
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Note the "Issuer" CN is "Red Hat Emerging Technologies" (the CA) and
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the "Subject" CN is "oirase" (the server).
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</p><p>
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Finally we have two files to install:
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</p><ul><li>
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<code>serverkey.pem</code> is
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the server's private key which should be copied to the
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server <i>only</i> as
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<code>/etc/pki/libvirt/private/serverkey.pem</code>.
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</li>
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<li>
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<code>servercert.pem</code> is the server's certificate
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which can be installed on the server as
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<code>/etc/pki/libvirt/servercert.pem</code>.
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</li>
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</ul><h4><a name="Remote_TLS_client_certificates" id="Remote_TLS_client_certificates">Issuing client certificates</a></h4><p>
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For each client (ie. any program linked with libvirt, such as
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<a href="http://virt-manager.et.redhat.com/">virt-manager</a>)
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you need to issue a certificate with the X.509 Distinguished Name (DN)
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set to a suitable name. You can decide this on a company / organisation
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policy. For example, I use:
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|
</p><pre>
|
|
C=GB,ST=London,L=London,O=Red Hat,CN=<i>name_of_client</i>
|
|
</pre><p>
|
|
The process is the same as for
|
|
<a href="#Remote_TLS_server_certificates">setting up the
|
|
server certificate</a> so here we just briefly cover the
|
|
steps.
|
|
</p><ol><li>
|
|
Make a private key:
|
|
<pre>
|
|
certtool --generate-privkey > clientkey.pem
|
|
</pre>
|
|
</li>
|
|
|
|
<li>
|
|
Act as CA and sign the certificate. Create client.info containing:
|
|
<pre>
|
|
country = GB
|
|
state = London
|
|
locality = London
|
|
organization = Red Hat
|
|
cn = client1
|
|
tls_www_client
|
|
encryption_key
|
|
signing_key
|
|
</pre>
|
|
and sign by doing:
|
|
<pre>
|
|
certtool --generate-certificate --load-privkey clientkey.pem \
|
|
--load-ca-certificate cacert.pem --load-ca-privkey cakey.pem \
|
|
--template client.info --outfile clientcert.pem
|
|
</pre>
|
|
</li>
|
|
|
|
<li>
|
|
Install the certificates on the client machine:
|
|
<pre>
|
|
cp clientkey.pem /etc/pki/libvirt/private/clientkey.pem
|
|
cp clientcert.pem /etc/pki/libvirt/clientcert.pem
|
|
</pre>
|
|
</li>
|
|
</ol><h4><a name="Remote_TLS_troubleshooting" id="Remote_TLS_troubleshooting">Troubleshooting TLS certificate problems</a></h4><dl><dt> failed to verify client's certificate </dt>
|
|
<dd>
|
|
<p>
|
|
On the server side, run the libvirtd server with
|
|
the '--listen' and '--verbose' options while the
|
|
client is connecting. The verbose log messages should
|
|
tell you enough to diagnose the problem.
|
|
</p>
|
|
</dd>
|
|
</dl><p> You can use the <a href="pki_check.sh">pki_check.sh</a> shell script
|
|
to analyze the setup on the client or server machines, preferably as root.
|
|
It will try to point out the possible problems and provide solutions to
|
|
fix the set up up to a point where you have secure remote access.</p><h3><a name="Remote_libvirtd_configuration" id="Remote_libvirtd_configuration">libvirtd configuration file</a></h3><p>
|
|
Libvirtd (the remote daemon) is configured from a file called
|
|
<code>/etc/libvirt/libvirtd.conf</code>, or specified on
|
|
the command line using <code>-f filename</code> or
|
|
<code>--config filename</code>.
|
|
</p><p>
|
|
This file should contain lines of the form below.
|
|
Blank lines and comments beginning with <code>#</code> are ignored.
|
|
</p><pre>setting = value</pre><p>The following settings, values and default are:</p><table class="top_table"><tr><th> Line </th>
|
|
<th> Default </th>
|
|
<th> Meaning </th>
|
|
</tr><tr><td> listen_tls <i>[0|1]</i> </td>
|
|
<td> 1 (on) </td>
|
|
<td>
|
|
Listen for secure TLS connections on the public TCP/IP port.
|
|
</td>
|
|
</tr><tr><td> listen_tcp <i>[0|1]</i> </td>
|
|
<td> 0 (off) </td>
|
|
<td>
|
|
Listen for unencrypted TCP connections on the public TCP/IP port.
|
|
</td>
|
|
</tr><tr><td> tls_port <i>"service"</i> </td>
|
|
<td> "16514" </td>
|
|
<td>
|
|
The port number or service name to listen on for secure TLS connections.
|
|
</td>
|
|
</tr><tr><td> tcp_port <i>"service"</i> </td>
|
|
<td> "16509" </td>
|
|
<td>
|
|
The port number or service name to listen on for unencrypted TCP connections.
|
|
</td>
|
|
</tr><tr><td> tls_no_verify_certificate <i>[0|1]</i> </td>
|
|
<td> 0 (certificates are verified) </td>
|
|
<td>
|
|
If set to 1 then if a client certificate check fails, it is not an error.
|
|
</td>
|
|
</tr><tr><td> tls_no_verify_address <i>[0|1]</i> </td>
|
|
<td> 0 (addresses are verified) </td>
|
|
<td>
|
|
If set to 1 then if a client IP address check fails, it is not an error.
|
|
</td>
|
|
</tr><tr><td> key_file <i>"filename"</i> </td>
|
|
<td> "/etc/pki/libvirt/ private/serverkey.pem" </td>
|
|
<td>
|
|
Change the path used to find the server's private key.
|
|
If you set this to an empty string, then no private key is loaded.
|
|
</td>
|
|
</tr><tr><td> cert_file <i>"filename"</i> </td>
|
|
<td> "/etc/pki/libvirt/ servercert.pem" </td>
|
|
<td>
|
|
Change the path used to find the server's certificate.
|
|
If you set this to an empty string, then no certificate is loaded.
|
|
</td>
|
|
</tr><tr><td> ca_file <i>"filename"</i> </td>
|
|
<td> "/etc/pki/CA/cacert.pem" </td>
|
|
<td>
|
|
Change the path used to find the trusted CA certificate.
|
|
If you set this to an empty string, then no trusted CA certificate is loaded.
|
|
</td>
|
|
</tr><tr><td> crl_file <i>"filename"</i> </td>
|
|
<td> (no CRL file is used) </td>
|
|
<td>
|
|
Change the path used to find the CA certificate revocation list (CRL) file.
|
|
If you set this to an empty string, then no CRL is loaded.
|
|
</td>
|
|
</tr><tr><td> tls_allowed_dn_list ["DN1", "DN2"] </td>
|
|
<td> (none - DNs are not checked) </td>
|
|
<td>
|
|
<p>
|
|
Enable an access control list of client certificate Distinguished
|
|
Names (DNs) which can connect to the TLS port on this server.
|
|
</p>
|
|
<p>
|
|
The default is that DNs are not checked.
|
|
</p>
|
|
<p>
|
|
This list may contain wildcards such as <code>"C=GB,ST=London,L=London,O=Red Hat,CN=*"</code>
|
|
See the POSIX <code>fnmatch</code> function for the format
|
|
of the wildcards.
|
|
</p>
|
|
<p>
|
|
Note that if this is an empty list, <i>no client can connect</i>.
|
|
</p>
|
|
<p>
|
|
Note also that GnuTLS returns DNs without spaces
|
|
after commas between the fields (and this is what we check against),
|
|
but the <code>openssl x509</code> tool shows spaces.
|
|
</p></td>
|
|
</tr><tr><td> tls_allowed_ip_list ["ip1", "ip2", "ip3"] </td>
|
|
<td> (none - clients can connect from anywhere) </td>
|
|
<td>
|
|
<p>
|
|
Enable an access control list of the IP addresses of clients
|
|
who can connect to the TLS or TCP ports on this server.
|
|
</p>
|
|
<p>
|
|
The default is that clients can connect from any IP address.
|
|
</p>
|
|
<p>
|
|
This list may contain wildcards such as <code>192.168.*</code>
|
|
See the POSIX <code>fnmatch</code> function for the format
|
|
of the wildcards.
|
|
</p>
|
|
<p>
|
|
Note that if this is an empty list, <i>no client can connect</i>.
|
|
</p>
|
|
</td>
|
|
</tr></table><h3><a name="Remote_IPv6" id="Remote_IPv6">IPv6 support</a></h3><p>
|
|
The libvirtd service and libvirt remote client driver both use the
|
|
<code>getaddrinfo()</code> functions for name resolution and are
|
|
thus fully IPv6 enabled. ie, if a server has IPv6 address configured
|
|
the daemon will listen for incoming connections on both IPv4 and IPv6
|
|
protocols. If a client has an IPv6 address configured and the DNS
|
|
address resolved for a service is reachable over IPv6, then an IPv6
|
|
connection will be made, otherwise IPv4 will be used. In summary it
|
|
should just 'do the right thing(tm)'.
|
|
</p><h3><a name="Remote_limitations" id="Remote_limitations">Limitations</a></h3><ul><li> Remote storage: To be fully useful, particularly for
|
|
creating new domains, it should be possible to enumerate
|
|
and provision storage on the remote machine. This is currently
|
|
in the design phase. </li>
|
|
|
|
<li> Migration: We expect libvirt will support migration,
|
|
and obviously remote support is what makes migration worthwhile.
|
|
This is also in the design phase. Issues <a href="https://www.redhat.com/mailman/listinfo/libvir-list" title="libvir-list mailing list">to discuss</a> include
|
|
which path the migration data should follow (eg. client to
|
|
client direct, or client to server to client) and security.
|
|
</li>
|
|
|
|
<li> Fine-grained authentication: libvirt in general,
|
|
but in particular the remote case should support more
|
|
fine-grained authentication for operations, rather than
|
|
just read-write/read-only as at present.
|
|
</li>
|
|
</ul><p>
|
|
Please come and discuss these issues and more on <a href="https://www.redhat.com/mailman/listinfo/libvir-list" title="libvir-list mailing list">the mailing list</a>.
|
|
</p><h3><a name="Remote_implementation_notes" id="Remote_implementation_notes">Implementation notes</a></h3><p>
|
|
The current implementation uses <a href="http://en.wikipedia.org/wiki/External_Data_Representation" title="External Data Representation">XDR</a>-encoded packets with a
|
|
simple remote procedure call implementation which also supports
|
|
asynchronous messaging and asynchronous and out-of-order replies,
|
|
although these latter features are not used at the moment.
|
|
</p><p>
|
|
The implementation should be considered <b>strictly internal</b> to
|
|
libvirt and <b>subject to change at any time without notice</b>. If
|
|
you wish to talk to libvirtd, link to libvirt. If there is a problem
|
|
that means you think you need to use the protocol directly, please
|
|
first discuss this on <a href="https://www.redhat.com/mailman/listinfo/libvir-list" title="libvir-list mailing list">the mailing list</a>.
|
|
</p><p>
|
|
The messaging protocol is described in
|
|
<code>qemud/remote_protocol.x</code>.
|
|
</p><p>
|
|
Authentication and encryption (for TLS) is done using <a href="http://www.gnu.org/software/gnutls/" title="GnuTLS project page">GnuTLS</a> and the RPC protocol is unaware of this layer.
|
|
</p><p>
|
|
Protocol messages are sent using a simple 32 bit length word (encoded
|
|
XDR int) followed by the message header (XDR
|
|
<code>remote_message_header</code>) followed by the message body. The
|
|
length count includes the length word itself, and is measured in
|
|
bytes. Maximum message size is <code>REMOTE_MESSAGE_MAX</code> and to
|
|
avoid denial of services attacks on the XDR decoders strings are
|
|
individually limited to <code>REMOTE_STRING_MAX</code> bytes. In the
|
|
TLS case, messages may be split over TLS records, but a TLS record
|
|
cannot contain parts of more than one message. In the common RPC case
|
|
a single <code>REMOTE_CALL</code> message is sent from client to
|
|
server, and the server then replies synchronously with a single
|
|
<code>REMOTE_REPLY</code> message, but other forms of messaging are
|
|
also possible.
|
|
</p><p>
|
|
The protocol contains support for multiple program types and protocol
|
|
versioning, modelled after SunRPC.
|
|
</p></div></div><div class="linkList2"><div class="llinks2"><h3 class="links2"><span>main menu</span></h3><ul><li><a href="index.html">Home</a></li><li><a href="news.html">Releases</a></li><li><a href="intro.html">Introduction</a></li><li><a href="architecture.html">libvirt architecture</a></li><li><a href="downloads.html">Downloads</a></li><li><a href="format.html">XML Format</a></li><li><a href="python.html">Binding for Python</a></li><li><a href="errors.html">Handling of errors</a></li><li><a href="FAQ.html">FAQ</a></li><li><a href="bugs.html">Reporting bugs and getting help</a></li><li><a href="remote.html">Remote support</a></li><li><a href="uri.html">Connection URIs</a></li><li><a href="hvsupport.html">Hypervisor support</a></li><li><a href="html/index.html">API Menu</a></li><li><a href="examples/index.html">C code examples</a></li><li><a href="ChangeLog.html">Recent Changes</a></li></ul></div><div class="llinks2"><h3 class="links2"><span>related links</span></h3><ul><li><a href="https://www.redhat.com/archives/libvir-list/">Mail archive</a></li><li><a href="https://bugzilla.redhat.com/bugzilla/buglist.cgi?product=Fedora+Core&component=libvirt&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&bug_status=MODIFIED&short_desc_type=allwordssubstr&short_desc=&long_desc_type=allwordssubstr">Open bugs</a></li><li><a href="http://virt-manager.et.redhat.com/">virt-manager</a></li><li><a href="http://search.cpan.org/~danberr/Sys-Virt-0.1.0/">Perl bindings</a></li><li><a href="http://et.redhat.com/~rjones/ocaml-libvirt/">OCaml bindings</a></li><li><a href="http://www.cl.cam.ac.uk/Research/SRG/netos/xen/index.html">Xen project</a></li><li><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="12" value="Search..." /><input name="submit" type="submit" value="Go" /></form></li><li><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-90x34.gif" alt="Made with Libxml2 Logo" /></a></li></ul><p class="credits">Graphics and design by <a href="mail:dfong@redhat.com">Diana Fong</a></p></div></div><div id="bottom"><p class="p1"></p></div></div></body></html>
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