This monitor is used to test if a SSL certificate presented by a remote network server are valid. A certificate is invalid if its initial time is prior to the current time, or if the current time is prior to 7 days (configurable) before the expiration time. The monitor only supports SSL on the socket and does not support a higher level protocol above it. Additionally, it does not support Server Name Indication (SNI) and so is unable to validate different certificates if they would be presented on the same connection.

You can simulate the behavior by running a command like this:

echo | openssl s_client -connect <site>:<port> 2>/dev/null | openssl x509 -noout -dates

The output shows you the time range a certificate is valid:

notBefore=Dec 24 14:11:34 2013 GMT
notAfter=Dec 25 10:37:40 2014 GMT

You can configure a threshold in days applied on the notAfter date.

Monitor facts

Class Name


Remote Enabled


Configuration and Usage
Table 1. Monitor specific parameters for the SSLCertMonitor
Parameter Description Required Default value


TCP port for the service with SSL certificate.




Number of attempts to get the certificate state




Time in milliseconds to wait before next attempt.




Number of days before the certificate expires that we mark the service as failed.




This is the DNS hostname to send as part of the TLS negotiation, known as server name indication (SNI) (See: RFC3546 section 3.1)



Table 2. Variables which can be passed in the configuration for server-name
Variable Description


The node’s IP-Address


The node ID


Label of the node the monitor is associated to.


The service name

The monitor has no support for communicating on other protocol layers above the SSL session layer. It is not able to send a Host header for HTTPS, or issue a STARTTLS command for IMAP, POP3, SMTP, FTP, XMPP, LDAP, or NNTP.

The following example shows how to monitor SSL certificates on services like IMAPS, SMTPS and HTTPS. If the certificates expire within 30 days the service goes down and indicates this issue in the reason of the monitor. In this example the monitoring interval is reduced to test the certificate every 2 hours (7,200,000 ms). Configuration in poller-configuration.xml is as the following:

<service name="SSL-Cert-IMAPS-993" interval="7200000" user-defined="false" status="on">
    <parameter key="retry" value="2"/>
    <parameter key="timeout" value="2000"/>
    <parameter key="port" value="993"/>
    <parameter key="days" value="30"/>
<service name="SSL-Cert-SMTPS-465" interval="7200000" user-defined="false" status="on">
    <parameter key="retry" value="2"/>
    <parameter key="timeout" value="2000"/>
    <parameter key="port" value="465"/>
    <parameter key="days" value="30"/>
<service name="SSL-Cert-HTTPS-443" interval="7200000" user-defined="false" status="on">
    <parameter key="retry" value="2"/>
    <parameter key="timeout" value="3000"/>
    <parameter key="port" value="443"/>
    <parameter key="days" value="30"/>
    <parameter key="server-name" value="${nodelabel}"/>

<monitor service="SSL-Cert-IMAPS-993" class-name="org.opennms.netmgt.poller.monitors.SSLCertMonitor" />
<monitor service="SSL-Cert-SMTPS-465" class-name="org.opennms.netmgt.poller.monitors.SSLCertMonitor" />
<monitor service="SSL-Cert-HTTPS-443" class-name="org.opennms.netmgt.poller.monitors.SSLCertMonitor" />