Written by Rainer Gerhards (2008-06-18)
In this step, we generate certificates for each of the machines. Please note that both clients and servers need certificates. The certificate identifies each machine to the remote peer. The DNSName specified inside the certificate can be specified inside the $<object>PermittedPeer config statements.
For now, we assume that a single person (or group) is responsible for the whole rsyslog system and thus it is OK if that single person is in posession of all machine's private keys. This simplification permits us to use a somewhat less complicated way of generating the machine certificates. So, we generate both the private and public key on the CA (which is NOT a server!) and then copy them over to the respective machines.
If the roles of machine and CA administrators are split, the private key must be generated by the machine administrator. This is done via a certificate request. This request is then sent to the CA admin, which in turn generates the certificate (containing the public key). The CA admin then sends back the certificate to the machine admin, who installs it. That way, the CA admin never get's hold of the machine's private key. Instructions for this mode will be given in a later revision of this document.
In any case, it is vital that the machine's private key is protected. Anybody able to obtain that private key can imporsonate as the machine to which it belongs, thus breaching your security.
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.
Please note: you need to substitute the names specified below with values
that match your environment. Most importantly, machine.example.net must be replaced
by the actual name of the machine that will be using this certificate. For example,
if you generate a certificate for a machine named "server.example.com", you need
to use that name. If you generate a certificate for "client.example.com", you need
to use this name. Make sure that each machine certificate has a unique name. If not,
you can not apply proper access control.
[root@rgf9dev sample]# certtool --generate-privkey --outfile key.pem --bits 2048
Generating a 2048 bit RSA private key...
[root@rgf9dev sample]# certtool --generate-request --load-privkey key.pem --outfile request.pem
Generating a PKCS #10 certificate request...
Country name (2 chars): US
Organization name: SomeOrg
Organizational unit name: SomeOU
Locality name: Somewhere
State or province name: CA
Common name: machine.example.net
UID:
Enter a challenge password:
[root@rgf9dev sample]# certtool --generate-certificate --load-request request.pem --outfile cert.pem --load-ca-certificate ca.pem --load-ca-privkey ca-key.pem
Generating a signed certificate...
Enter the certificate's serial number (decimal):
Activation/Expiration time.
The certificate will expire in (days): 1000
Extensions.
Does the certificate belong to an authority? (Y/N): n
Is this a TLS web client certificate? (Y/N): y
Is this also a TLS web server certificate? (Y/N): y
Enter the dnsName of the subject of the certificate: machine.example.net {This is the name of the machine that will use the certificate}
Will the certificate be used for signing (DHE and RSA-EXPORT ciphersuites)? (Y/N):
Will the certificate be used for encryption (RSA ciphersuites)? (Y/N):
X.509 Certificate Information:
Version: 3
Serial Number (hex): 485a3819
Validity:
Not Before: Thu Jun 19 10:42:54 UTC 2008
Not After: Wed Mar 16 10:42:57 UTC 2011
Subject: C=US,O=SomeOrg,OU=SomeOU,L=Somewhere,ST=CA,CN=machine.example.net
Subject Public Key Algorithm: RSA
Modulus (bits 2048):
b2:4e:5b:a9:48:1e:ff:2e:73:a1:33:ee:d8:a2:af:ae
2f:23:76:91:b8:39:94:00:23:f2:6f:25:ad:c9:6a:ab
2d:e6:f3:62:d8:3e:6e:8a:d6:1e:3f:72:e5:d8:b9:e0
d0:79:c2:94:21:65:0b:10:53:66:b0:36:a6:a7:cd:46
1e:2c:6a:9b:79:c6:ee:c6:e2:ed:b0:a9:59:e2:49:da
c7:e3:f0:1c:e0:53:98:87:0d:d5:28:db:a4:82:36:ed
3a:1e:d1:5c:07:13:95:5d:b3:28:05:17:2a:2b:b6:8e
8e:78:d2:cf:ac:87:13:15:fc:17:43:6b:15:c3:7d:b9
Exponent:
01:00:01
Extensions:
Basic Constraints (critical):
Certificate Authority (CA): FALSE
Key Purpose (not critical):
TLS WWW Client.
TLS WWW Server.
Subject Alternative Name (not critical):
DNSname: machine.example.net
Subject Key Identifier (not critical):
0ce1c3dbd19d31fa035b07afe2e0ef22d90b28ac
Authority Key Identifier (not critical):
fbfe968d10a73ae5b70d7b434886c8f872997b89
Other Information:
Public Key Id:
0ce1c3dbd19d31fa035b07afe2e0ef22d90b28ac
Is the above information ok? (Y/N): y
Signing certificate...
[root@rgf9dev sample]# rm -f request.pem
[root@rgf9dev sample]# ls -l
total 16
-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
-rw-r--r-- 1 root root 1074 2008-06-19 12:43 cert.pem
-rw-r--r-- 1 root root 887 2008-06-19 12:40 key.pem
[root@rgf9dev sample]# # it may be a good idea to rename the files to indicate where they belong to
[root@rgf9dev sample]# mv cert.pem machine-cert.pem
[root@rgf9dev sample]# mv key.pem machine-key.pem
[root@rgf9dev sample]#
Provide the machine with:
This is how the relevant part of rsyslog.conf looks on the target machine:
$DefaultNetstreamDriverCAFile /home/rger/proj/rsyslog/sample/ca.pem
$DefaultNetstreamDriverCertFile /home/rger/proj/rsyslog/sample/machine-cert.pem
$DefaultNetstreamDriverKeyFile /home/rger/proj/rsyslog/sample/machine-key.pem
Never provide anyone with ca-key.pem! Also, make sure nobody but the machine in question gets hold of key.pem.
Copyright (c) 2008 Rainer Gerhards and Adiscon.
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 http://www.gnu.org/copyleft/fdl.html.