Configure a secure connection to a syslog server

You can use an external certificate to send TLS-encrypted logs to the syslog server from Sophos Firewall. You need to use the default Certificate Authority (CA) of Sophos Firewall.

Introduction

Prerequisite: To establish a TLS connection with the syslog server, you must turn on TLS encryption on the syslog server.

In this example, we use the following:

• Syslog server: syslog-ng
• Client: Sophos Firewall
• External certificate (ExternalCertificate.pem), external key (ExternalPrivateKey.key), and external CA (ExternalCA.pem). You generate these using a third-party CA.
• Default CA certificate (Default.pem) available on Sophos Firewall.

The configuration steps are as follows:

• Specify the attributes and details of the default CA on Sophos Firewall.
• Copy the default and external CA certificates, the external certificate, and the external key to the syslog server.
• On Sophos Firewall, add the syslog server.
• Select the modules for which logs are to be sent to the syslog server.

Configure the attributes for the default CA on Sophos Firewall

To get the CA certificate, specify the attributes for the default CA, and download the file.

1. Go to Certificates > Certificate authorities and click the default CA (Default).

   You can't change the CA name.

2. You can change the following attributes:

   Name	Description
   Country name	Country in which the device is deployed.
   State	The state within the country.
   Locality name	Name of the city.
   Organization name	Name of the certificate owner. Example: Sophos Group
   Organization unit name	Name of the department to which the certificate will be assigned. Example: Marketing
   Common name	Common name or FQDN. Example: marketing.sophos.com
   Email address	Contact person's email address.
   Private key password	If a password was set for the CA, you can change it here.
   Key type	Select from the following options: RSA Elliptic curve
   Key length	If you've set the key type to RSA, select the key length. It's the number of bits used to construct the key. Larger keys offer greater security, but it takes longer to encrypt and decrypt data.
   Curve name	If you've set the key type to Elliptic curve, select the curve name.
   Secure hash	Select the algorithm from the list.

3. Click Save.

4. Click download for the default CA you updated.

   It's a tar.gz file.

5. Extract the files to get the CA certificate Default.pem.

Copy the certificate and CA to the syslog server

Copy the default CA certificate of Sophos Firewall and the external certificate and key to the syslog server.

1. Go to the syslog server and copy Default.pem and ExternalCA.pem to the /etc/syslog-ng/ca.d/ directory.
2. Copy the syslog server's certificate (ExternalCertificate.pem) and key (ExternalPrivateKey.key) to the /etc/syslog-ng/cert.d/ directory

3. Go to the /etc/syslog-ng/ca.d/ directory, and enter the following command to create a hash based on Default.pem:

   #openssl x509 -noout -hash -in Default.pem

   The result is an alphanumeric hash (example: 52412b66) based on the distinguished name in the CA certificate.

4. Enter the following command using the hash with the suffix .0 to create a symbolic link to Default.pem:

   #ln -s Default.pem 52412b66.0

5. Edit the syslog-ng.conf file to point to the certificate (ExternalCertificate.pem), the key (ExternalPrivateKey.key), the third-party CA certificate (ExternalCA.pem), and the CA certificate of Sophos Firewall (Default.pem). Do as follows:

   1. Enter ExternalCertificate.pem and ExternalPrivateKey.key with the paths for the respective directories.
   2. Enter ca.d with the path for the CA directory.

   Example

   @version: 3.15
   
   @include "scl.conf"
   
   source s_src {
   
       network(ip(0.0.0.0) port(6514)
   
           transport("tls")
   
           tls( key-file("/etc/syslog-ng/cert.d/ExternalPrivateKey.key")
   
                cert-file("/etc/syslog-ng/cert.d/ExternalCertificate.pem")
   
                ca-dir("/etc/syslog-ng/ca.d")
   
                peer_verify(required-trusted))
   
       ); };
   
   destination d_local {
   
           file("/var/log/messages");
   
           file("/var/log/messages-kv.log" template("$ISODATE $HOST $(format-welf --scope all-nv-pairs)\n") frac-digits(3));
   
   };
   
   log { source(s_src);
   
           destination(d_local);
   
   };
   

6. Start the syslog-ng server.

Add a syslog server

Add a syslog server to Sophos Firewall, and specify the log settings for the server.

1. Go to System services > Log settings and click Add.

2. Specify the settings.

   Option	Description
   IP address/domain	IP address or domain name of the syslog server.
   Secure log transmission	Encrypts logs sent to the syslog server using TLS.
   Port	6514

3. Click Save.

   Here's an example:

   

4. Go to System services > Log settings and scroll down to Log settings. Under Syslog server, select the logs you want to send.

   Here's an example: