NXLog Documentation

Encrypted transfer

In order to protect log data in transit from being modified or viewed by an attacker, NXLog provides SSL/TLS data encryption support in many input and output modules. Benefits of using SSL/TLS encrypted log transfer include:

  • strong authentication,

  • message integrity (assures that the logs are not changed), and

  • message confidentiality (assures that the logs cannot be viewed by an unauthorized party).

It is important that certificates be renewed before expiration. The NXLog Manager dashboard can be configured with a "Certificate summary" which lists soon-to-expire certificates in a separate group.

SSL/TLS encryption in NXLog

The SSL/TLS protocol encrypts log data on the client side and then decrypts it on the server side. It’s recommended to use 2048-bit keys or larger.

There are several modules in NXLog Enterprise Edition that support SSL/TLS encryption:

When using the SSL/TLS, there are two ways to handle authentication.

  • With mutual authentication, both client and log server agents are authenticated, and certificates/keys must be deployed for both agents. This is the most secure and prevents log collection if the client’s certificate is untrusted or has expired.

  • With server-side authentication only, authentication takes place only via a certificate/key deployed on the server. On the log server, the im_ssl AllowUntrusted directive (or corresponding directive for im_http or im_batchcompress) must be set to TRUE. The client is prevented from sending logs to an untrusted server but the server accepts logs from untrusted clients.

Example 1. Client/Server encrypted transfer

With the following configurations, a client reads logs from all log files under the /var/log directory, parses the events with parse_syslog(), converts to JSON with to_json(), and forwards them over a secure connection to the central server.

These configurations use mutual authentication: both agents are authenticated and certificates must be created for both agents.

nxlog.conf (client)
<Extension _syslog>
    Module      xm_syslog

<Extension _json>
    Module      xm_json

<Input messages>
    Module      im_file
    File        "/var/log/*"
    Exec        parse_syslog();

<Output central_ssl>
    Module      om_ssl
    Port        516
    CAFile      /opt/ssl/rootCA.pem
    CertFile    /opt/ssl/client.crt
    CertKeyFile /opt/ssl/client.key
    KeyPass     password
    Exec        to_json();

The server receives the logs on port 516 and writes them to /var/log/logmsg.log.

nxlog.conf (central server)
<Extension _syslog>
    Module      xm_syslog

<Input input_ssl>
    Module      im_ssl
    Port        516
    CAFile      /opt/ssl/rootCA.pem
    CertFile    /opt/ssl/central.crt
    CertKeyFile /opt/ssl/central.key
    KeyPass     password

<Output fileout>
    Module      om_file
    File        "/var/log/logmsg.log"

OpenSSL certificate creation

NXLog Manager provides various features for creating, deploying, and managing SSL/TLS certificates, and is especially helpful when managing many NXLog agents across an organization. This section, however, provides steps for creating self-signed certificates with OpenSSL, a Linux-based SSL/TLS cryptography toolkit.

  1. Generate the private root key for your Certification Authority (CA).

    $ openssl genrsa -out rootCA.key 2048
  2. Self-sign the key and create a CA certificate.

    $ openssl req -x509 -new -nodes -key rootCA.key -sha256 -days 730 -out rootCA.pem
  3. Create a certificate for each server.

    1. Generate a private key for the server.

      $ openssl genrsa -out server.key 2048
    2. Generate the certificate signing request for the CA. When prompted for the Common Name, enter the server’s name or IP address.

      $ openssl req -new -key server.key -out server.csr
    3. Sign the request.

      $ openssl x509 -req -in server.csr -CA rootCA.pem -CAkey rootCA.key \
                          -CAcreateserial -out server.crt -days 500 -sha256