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<?xml version="1.0"?>
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
"http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd">
<chapter id="https">
<title>SSL/TLS Usage</title>
<para>Cockpit usually requires that web browsers communicate with it using HTTPS,
for security reasons.</para>
<section id="https-required">
<title>HTTPS Requirement</title>
<para>Cockpit listens for both HTTP and HTTPS connections on the same port, by
default 9090. If an HTTP connection is made, Cockpit will redirect that
connection to HTTPS. There are some exceptions:</para>
<itemizedlist>
<listitem><para>If an HTTP connection comes from <code>127.0.0.0/8</code>, then
Cockpit will allow communication without redirecting to HTTPS.</para></listitem>
<listitem><para>Certain URLs, like <code>/ping</code> are not required to use
HTTPS.</para></listitem>
</itemizedlist>
<para>This behavior can be overridden by setting the
<code>AllowUnencrypted</code> option in <code>cockpit.conf</code>.</para>
</section>
<section id="https-certificates">
<title>Certificates</title>
<para>Cockpit will load a certificate from the <code>/etc/cockpit/ws-certs.d</code>
directory. It will use the last file with a <code>.cert</code> extension in
alphabetical order. The <literal>.cert</literal> file should contain at least two
OpenSSL style PEM blocks. First one or more <literal>BEGIN CERTIFICATE</literal>
blocks for the server certificate and the intermediate certificate authorities
and a last one containing a <literal>BEGIN PRIVATE KEY</literal> or similar.
The key may not be encrypted. For example:</para>
<programlisting>
-----BEGIN CERTIFICATE-----
MIIDUzCCAjugAwIBAgIJAPXW+CuNYS6QMA0GCSqGSIb3DQEBCwUAMD8xKTAnBgNV
BAoMIGI0OGE2NGNkNmMwNTQ1YThhZTgxOTEzZDE5YmJjMmRjMRIwEAYDVQQDDAls
...
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
MIIDUzCCAjugAwIBAgIJAPXW+CuNYS6QMA0GCSqGSIb3DQEBCwUAMD8xKTAnBgNV
BAoMIGI0OGE2NGNkNmMwNTQ1YThhZTgxOTEzZDE5YmJjMmRjMRIwEAYDVQQDDAls
...
-----END CERTIFICATE-----
-----BEGIN PRIVATE KEY-----
MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQCyOJ5garOYw0sm
8TBCDSqQ/H1awGMzDYdB11xuHHsxYS2VepPMzMzryHR137I4dGFLhvdTvJUH8lUS
...
-----END PRIVATE KEY-----
</programlisting>
<para>If no certificate is found, a self-signed certificate is created and
stored in the <filename>0-self-signed.cert</filename> file. On some
platforms, Cockpit will also generate a ca.crt in that directory, which
may be safely imported into client browsers.</para>
<para>To check which certificate <code>cockpit-ws</code> will use run
the following command.</para>
<programlisting>
$ sudo remotectl certificate
</programlisting>
<para>If using <code>certmonger</code> to manage certificates, following command can
be used to automatically prepare concatenated .cert file:</para>
<programlisting>
CERT_FILE=/etc/pki/tls/certs/$(hostname).pem
KEY_FILE=/etc/pki/tls/private/$(hostname).key
getcert request -f ${CERT_FILE} -k ${KEY_FILE} -D $(hostname --fqdn) -C "sed -n w/etc/cockpit/ws-certs.d/50-from-certmonger.cert ${CERT_FILE} ${KEY_FILE}"
</programlisting>
</section>
<section id="https-compat">
<title>SSL Versions and Ciphers</title>
<para>By default Cockpit will only use modern secure ciphers and versions of TLS.
In particular SSL v3.0 is disabled by default, as well as the RC4 cipher.</para>
<para>If you wish to enable these legacy protocols and algorithms you can do so
by passing an environment variable to cockpit-ws. Place the following in the
<code>/etc/systemd/system/cockpit.service.d/ssl.conf</code> file. Create the
file and directories in that path which don't already exist.</para>
<programlisting>
[Service]
Environment=G_TLS_GNUTLS_PRIORITY=NORMAL:%COMPAT
</programlisting>
<para>The environment variable value is a
<ulink url="https://gnutls.org/manual/html_node/Priority-Strings.html#Priority-Strings">GnuTLS priority string</ulink>.</para>
</section>
</chapter>
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