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<h1>Encrypting Syslog Traffic with TLS (SSL)</h1>
<p><small><i>Written by <a href="http://www.adiscon.com/en/people/rainer-gerhards.php">Rainer
Gerhards</a> (2008-06-17)</i></small></p>

<ul>
<li><a href="rsyslog_secure_tls.html">Overview</a>
<li><a href="tls_cert_scenario.html">Sample Scenario</a>
<li><a href="tls_cert_ca.html">Setting up the CA</a>
<li><a href="tls_cert_machine.html">Generating Machine Certificates</a>
<li><a href="tls_cert_server.html">Setting up the Central Server</a>
<li><a href="tls_cert_client.html">Setting up syslog Clients</a>
<li><a href="tls_cert_udp_relay.html">Setting up the UDP syslog relay</a>
<li><a href="tls_cert_summary.html">Wrapping it all up</a>
</ul>

<h3>Setting up the CA</h3>
<p>The first step is to set up a certificate authority (CA). It must be 
maintained by a trustworthy person (or group) and approves the indentities of 
all machines. It does so by issuing their certificates. In a small setup, the 
administrator can provide the CA function. What is important is the the CA's 
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private key is well-protocted and machine certificates are only issued if it is 
know they are valid (in a single-admin case that means the admin should not 
issue certificates to anyone else except himself).</p>
<p>The CA creates a so-called self-signed certificate. That is, it approves its 
own authenticy. This sounds useless, but the key point to understand is that 
every machine will be provided a copy of the CA's certificate. Accepting this 
certificate is a matter of trust. So by configuring the CA certificate, the 
administrator tells <a href="http://www.rsyslog.com">rsyslog</a> which certificates to trust. This is the root of all 
trust under this model. That is why the CA's private key is so important - 
everyone getting hold of it is trusted by our rsyslog instances.</p>
<center><img src="tls_cert_ca.jpg"></center>
<p>To create a self-signed certificate, use the following commands with GnuTLS (which 
is currently the only supported TLS library, what may change in the future).
Please note that GnuTLS' tools are not installed by default on many platforms. Also,
the tools do not necessarily come with the GnuTLS core package. If you do not
have certtool on your system, check if there is package for the GnuTLS tools available
(under Fedora, for example, this is named gnutls-utils-&lt;version&gt; and
it is NOT installed by default). </p>
<ol>
<li>generate the private key:
<pre>certtool --generate-privkey --outfile ca-key.pem</pre>
<br>
This takes a short while. Be sure to do some work on your workstation,
it waits for radom input. Switching between windows is sufficient ;)
</li>
<li>now create the (self-signed) CA certificate itself:<br>
<pre>certtool --generate-self-signed --load-privkey ca-key.pem --outfile ca.pem</pre>
This generates the CA certificate. This command queries you for a
number of things. Use appropriate responses. When it comes to
certificate validity, keep in mind that you need to recreate all
certificates when this one expires. So it may be a good idea to use a
long period, eg. 3650 days (roughly 10 years). You need to specify that
the certificates belongs to an authority. The certificate is used to
sign other certificates.<br>
</li>
</ol>
<h3>Sample Screen Session</h3>
<p>Text in red is user input. Please note that for some questions, there is no
user input given. This means the default was accepted by simply pressing the 
enter key.
<code><pre>
[root@rgf9dev sample]# <font color="red">certtool --generate-privkey --outfile ca-key.pem --bits 2048</font>
Generating a 2048 bit RSA private key...
[root@rgf9dev sample]# <font color="red">certtool --generate-self-signed --load-privkey ca-key.pem --outfile ca.pem</font>
Generating a self signed certificate...
Please enter the details of the certificate's distinguished name. Just press enter to ignore a field.
Country name (2 chars): <font color="red">US</font>
Organization name: <font color="red">SomeOrg</font>
Organizational unit name: <font color="red">SomeOU</font>
Locality name: <font color="red">Somewhere</font>
State or province name: <font color="red">CA</font>
Common name: <font color="red">someName (not necessarily DNS!)</font>
UID: 
This field should not be used in new certificates.
E-mail: 
Enter the certificate's serial number (decimal):

Activation/Expiration time.
The certificate will expire in (days): <font color="red">3650</font>

Extensions.
Does the certificate belong to an authority? (Y/N): <font color="red">y</font>
Path length constraint (decimal, -1 for no constraint): 
Is this a TLS web client certificate? (Y/N): 
Is this also a TLS web server certificate? (Y/N): 
Enter the e-mail of the subject of the certificate: <font color="red">someone@example.net</font>
Will the certificate be used to sign other certificates? (Y/N): <font color="red">y</font>
Will the certificate be used to sign CRLs? (Y/N): 
Will the certificate be used to sign code? (Y/N): 
Will the certificate be used to sign OCSP requests? (Y/N): 
Will the certificate be used for time stamping? (Y/N): 
Enter the URI of the CRL distribution point:        
X.509 Certificate Information:
	Version: 3
	Serial Number (hex): 485a365e
	Validity:
		Not Before: Thu Jun 19 10:35:12 UTC 2008
		Not After: Sun Jun 17 10:35:25 UTC 2018
	Subject: C=US,O=SomeOrg,OU=SomeOU,L=Somewhere,ST=CA,CN=someName (not necessarily DNS!)
	Subject Public Key Algorithm: RSA
		Modulus (bits 2048):
			d9:9c:82:46:24:7f:34:8f:60:cf:05:77:71:82:61:66
			05:13:28:06:7a:70:41:bf:32:85:12:5c:25:a7:1a:5a
			28:11:02:1a:78:c1:da:34:ee:b4:7e:12:9b:81:24:70
			ff:e4:89:88:ca:05:30:0a:3f:d7:58:0b:38:24:a9:b7
			2e:a2:b6:8a:1d:60:53:2f:ec:e9:38:36:3b:9b:77:93
			5d:64:76:31:07:30:a5:31:0c:e2:ec:e3:8d:5d:13:01
			11:3d:0b:5e:3c:4a:32:d8:f3:b3:56:22:32:cb:de:7d
			64:9a:2b:91:d9:f0:0b:82:c1:29:d4:15:2c:41:0b:97
		Exponent:
			01:00:01
	Extensions:
		Basic Constraints (critical):
			Certificate Authority (CA): TRUE
		Subject Alternative Name (not critical):
			RFC822name: someone@example.net
		Key Usage (critical):
			Certificate signing.
		Subject Key Identifier (not critical):
			fbfe968d10a73ae5b70d7b434886c8f872997b89
Other Information:
	Public Key Id:
		fbfe968d10a73ae5b70d7b434886c8f872997b89

Is the above information ok? (Y/N): <font color="red">y</font>

Signing certificate...
[root@rgf9dev sample]# <font color="red">chmod 400 ca-key.pem</font>
[root@rgf9dev sample]# <font color="red">ls -l</font>
total 8
-r-------- 1 root root  887 2008-06-19 12:33 ca-key.pem
-rw-r--r-- 1 root root 1029 2008-06-19 12:36 ca.pem
[root@rgf9dev sample]# 
</pre></code>
<p><font color="red"><b>Be sure to safeguard ca-key.pem!</b> Nobody except the CA itself
needs to have it. If some third party obtains it, you security is broken!</font>
<h2>Copyright</h2>
<p>Copyright (c) 2008 <a href="http://www.adiscon.com/en/people/rainer-gerhards.php">Rainer
Gerhards</a> and
<a href="http://www.adiscon.com/en/">Adiscon</a>.</p>
<p> Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version
1.2 or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license can be viewed at
<a href="http://www.gnu.org/copyleft/fdl.html">http://www.gnu.org/copyleft/fdl.html</a>.</p>
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