<%NUMBERING1%>.<%NUMBERING2%>.<%NUMBERING3%> PRTG Manual: SSL Certificate Sensor

The SSL Certificate sensor monitors the certificate of a secure Secure Sockets Layer (SSL)/Transport Layer Security (TLS) connection.

The sensor can show the following:

  • Days to expiration with predefined lower warning limit (28 days) and lower error limit (7 days)
  • Public key length
    • RSA keys: Warning status for 1024-bit keys (weak security); Up status for 2048-bit keys (good security) and longer (perfect security); Down status for shorter keys (unsafe)
    • Elliptic Curve Cryptography (ECC) keys: Up status for 128-bit and 192-bit keys (good security) and longer perfect security); Down status for shorter keys (unsafe)
  • If common name or subject-alternative names match the host address or Server Name Identification (SNI) (if certificate name validation is enabled)
  • If the certificate has been revoked (failing to query the certificate revocation list results in a Warning status)
  • If the certificate is trusted as root authority
  • If a self-signed certificate is used
  • Certificate common name (sensor message)
  • Certificate thumbprint (sensor message)
SSL Certificate Sensor

SSL Certificate Sensor

Sensor in Other Languages

  • Dutch: SSL Certificaat
  • French: Certificat SSL
  • German: SSL-Zertifikat
  • Japanese: SSL 証明書
  • Portuguese: Certificado SSL
  • Russian: Сертификат SSL
  • Simplified Chinese: SSL 证书
  • Spanish: Certificado SSL

Remarks

  • To check the revocation status of a certificate, the sensor uses WinHTTP to auto-detect the proxy server to use. You can also manually define a server. If you do not define a proxy server, PRTG uses the default WinHTTP proxy settings. For more information, see the Knowledge Base: How can I configure the WinHTTP proxy settings for the SSL Certificate Sensor?.
  • This sensor has predefined limits for several metrics. You can individually change these limits in the channel settings. For detailed information about channel limits, see section Sensor Channel Settings.
  • This sensor supports the IPv6 protocol.
  • This sensor uses lookups to determine the status values of one or more channels. This means that possible states are defined in a lookup file. You can change the behavior of a channel by editing the lookup file that the channel uses. For details, see section Define Lookups.

icon-i-round-blueThis sensor supersedes the deprecated HTTP Certificate Expiry sensor.

Add Sensor

The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the setting fields that are required for creating the sensor. Therefore, you do not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

Settings

Click the Settings tab of a sensor to change its settings.

icon-i-round-blueUsually, a sensor connects to the IP Address or DNS Name of the parent device on which you created the sensor. See the device settings for details. For some sensors, you can explicitly define the monitoring target in the sensor settings. See below for details on available settings.

Setting

Description

Sensor Name

Enter a meaningful name to identify the sensor. By default, PRTG shows this name in the device tree, as well as in alarms, logs, notifications, reports, maps, libraries, and tickets.

Parent Tags

Shows tags that this sensor inherits from its parent device, group, and probe. This setting is shown for your information only and cannot be changed here.

Tags

Enter one or more tags. Confirm each tag with the Spacebar key, a comma, or the Enter key. You can use tags to group objects and use tag-filtered views later on. Tags are not case-sensitive. Tags are automatically inherited. You can add additional tags to the sensor.

icon-i-round-blueIt is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).

There are default tags that are automatically predefined in a sensor's settings when you add a sensor. See section Default Tags below.

Priority

Select a priority for the sensor. This setting determines where the sensor is placed in sensor lists. A sensor with a top priority is at the top of a list. Choose from one star (low priority) to five stars (top priority).

Default Tags

sslcertificate, ssl, certificate

SSL Certificate Specific

Setting

Description

Port

Enter the number of the port to which this sensor connects. Enter an integer value. The default port is 443.

Virtual Host (SNI Domain)

Define the host name that the sensor tries to query if your server has multiple certificates on the same IP address and port combination. Enter a string.

In case of virtual hosting, you need to identify the specific certificate for a specific domain while all domains use the same IP address, you can use SNI, which is an extension of TLS.

icon-i-round-blueIf you enable Certificate Name Validation below, the sensor compares the common name and optionally alternative names with the SNI defined here. Leave this field empty to validate the common name with the host address of the parent device.

Certificate Name Validation

Define if you want the sensor to validate the certificate name:

  • Do not compare common name with device address or SNI (default): The sensor does not check if the certificate name is valid by comparing it with the address of the parent device or the defined SNI.
  • Compare and show down status if common name and address/SNI do not match: Check the common name to validate the certificate. If you set an SNI domain above, the sensor compares the common name with this SNI. If you leave the SNI field empty, the sensor uses the host address of the parent device. If the common name and the checked address/SNI do not match, the sensor shows a Down status.
  • Compare and show down status if common name/alternative names and address/SNI do not match: Check common name and Subject Alternative Names (SAN) to validate the certificate. If you set an SNI domain above, the sensor compares the common name and alternative names with the SNI. If you leave the SNI field empty, the sensor uses the host address of the parent device. If the common name or alternative names and the checked address/SNI do not match, the sensor shows a Down status.

Connection Specific

Setting

Description

Use SOCKS Proxy (v5 only)

Define if you want to use a SOCKS proxy server for the sensor connection:

  • Do not use SOCKS proxy (default): The sensor directly connects to the target host without using a SOCKS proxy.
  • Use SOCKS proxy: The sensor connects using SOCKS5. Provide data for the SOCKS connection below.
    icon-i-round-blueOther SOCKS versions are not supported.

icon-i-round-blueThis sensor only supports SOCKS5 proxies. HTTP proxies are not supported.

SOCKS Proxy Server

This field is only visible if you enable Use SOCKS proxy above. Enter the IP address or host name of the SOCKS5 proxy server that the sensor uses for connection.

SOCKS Proxy Server Port

This field is only visible if you enable Use SOCKS proxy above. Enter the port number of the SOCKS5 proxy server that the sensor uses for connection.

SOCKS Proxy Server User

This field is only visible if you enable Use SOCKS proxy above. If the SOCKS5 proxy server requires authentication, enter a username.

SOCKS Proxy Server Password

This field is only visible if you enable Use SOCKS proxy above. If the SOCKS5 proxy server requires authentication, enter the password for the user you specified above.

Debug Options

Setting

Description

Sensor Result

Define what PRTG does with the sensor results:

  • Discard sensor result: Do not store the sensor result.
  • Write sensor result to disk (file name: Result of Sensor [ID].txt): Store the last result received from the sensor to the \Logs\sensors subfolder of the PRTG data directory on the probe system (master node, if in a cluster). File names: Result of Sensor [ID].txt and Result of Sensor [ID].Data.txt. This is for debugging purposes. PRTG overwrites these files with each scanning interval.

icon-prtg-on-demandThis option is not available when the sensor runs on the hosted probe of a PRTG hosted by Paessler instance.

icon-i-round-blueYou can use the debug option to get a logfile with information about the certificate chain. Additionally, certificates in the certificate chain are stored in the log folder (.cer files). This can help you, for example, if you have issues with the Root Authority Trusted channel of this sensor.

Sensor Display

Setting

Description

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel is always displayed below the sensor's name. The available options depend on what channels are available for this sensor.

icon-i-round-blueYou can set a different primary channel later by clicking the pin symbol of a channel on the sensor's Overview tab.

Graph Type

Define how different channels are shown for this sensor:

  • Show channels independently (default): Show a graph for each channel.
  • Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This generates a graph that visualizes the different components of your total traffic.
    icon-i-round-blueThis option cannot be used in combination with manual Vertical Axis Scaling (available in the channel settings).

Stack Unit

This field is only visible if you enable Stack channels on top of each other as Graph Type. Select a unit from the list. All channels with this unit are stacked on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.

Inherited Settings

By default, all of the following settings are inherited from objects that are higher in the hierarchy and should be changed there if necessary. Often, best practice is to change them centrally in the root group settings. For more information, see section Inheritance of Settings. To change a setting for this object only, disable inheritance by clicking the button next to inherit from under the corresponding setting name. You then see the options described below.

Scanning Interval

Click inherited_settings_button to interrupt the inheritance. See section Inheritance of Settings for more information.

Setting

Description

Scanning Interval

Select a scanning interval (seconds, minutes, or hours). The scanning interval determines the amount of time that the sensor waits between two scans. You can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Define the number of scanning intervals that the sensor has time to reach and check a device again in case a sensor query fails. Depending on the option that you select, the sensor can try to reach and check a device again several times before the sensor shows a Down status. This can avoid false alarms if the monitored device only has temporary issues. For previous scanning intervals with failed requests, the sensor shows a Warning status. Choose from:

  • Set sensor to down immediately: Set the sensor to a Down status immediately after the first failed request.
  • Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to a Warning status after the first failed request. If the following request also fails, the sensor shows an error.
  • Set sensor to warning for 2 intervals, then set to down: Set the sensor to a Down status only after three consecutively failed requests.
  • Set sensor to warning for 3 intervals, then set to down: Set the sensor to a Down status only after four consecutively failed requests.
  • Set sensor to warning for 4 intervals, then set to down: Set the sensor to a Down status only after five consecutively failed requests.
  • Set sensor to warning for 5 intervals, then set to down: Set the sensor to a Down status only after six consecutively failed requests.

icon-i-round-blueSensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval before they show a Down status. It is not possible to immediately set a WMI sensor to a Down status, so the first option does not apply to these sensors. All other options can apply.

icon-i-round-blueIf you define error limits for a sensor's channels, the sensor immediately shows a Down status. No "wait" option applies.

icon-i-round-blueIf a channel uses lookup values, the sensor immediately shows a Down status. No "wait" options apply.

Schedules, Dependencies, and Maintenance Window

icon-i-round-blueYou cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. The corresponding settings from the parent objects are always active. However, you can define additional settings here. They are active at the same time as the parent objects' settings.

Setting

Description

Schedule

Select a schedule from the list. Schedules can be used to monitor for a certain time span (days or hours) every week.

icon-square-cyanYou can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Account Settings—Schedules.

icon-i-round-blueSchedules are generally inherited. New schedules are added to schedules that you already set up, so all schedules are active at the same time.

Maintenance Window

Specify if you want to set up a one-time maintenance window. During a maintenance window, the selected object and all child objects are not monitored. They are in a Paused status instead. Choose between:

  • Not set (monitor continuously): No maintenance window is set and monitoring is always active.
  • Set up a one-time maintenance window: Pause monitoring within a maintenance window. You can define a time span for a monitoring pause below and change it even for an active maintenance window.

icon-i-round-blueTo terminate an active maintenance window before the defined end date, change the time entry in Maintenance Ends to a date in the past.

Maintenance Begins

This field is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the start date and time of the maintenance window.

Maintenance Ends

This field is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the end date and time of the maintenance window.

Dependency Type

Define a dependency type. You can use dependencies to pause monitoring for an object depending on the status of a different object. You can choose from:

  • Use parent: Use the dependency type of the parent object.
  • Select a sensor: Use the dependency type of the parent object. Additionally, pause the current object if a specific sensor is in a Down status or in a Paused status caused by another dependency.
  • Master sensor for parent: Make this sensor the master object for its parent device. The sensor influences the behavior of its parent device: If the sensor is in a Down status, the device is paused. For example, it is a good idea to make a Ping sensor the master object for its parent device to pause monitoring for all other sensors on the device in case the device cannot even be pinged. Additionally, the sensor is paused if the parent group is paused by another dependency.

icon-i-round-blueTo test your dependencies, select Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later, all dependent objects are paused. You can check all dependencies under Devices | Dependencies in the main menu bar.

Dependency

This field is only visible if you enable Select a sensor above. Click the Search button and use the object selector to select a sensor on which the current object will depend.

Dependency Delay (Sec.)

This field is only visible if you enable Select a sensor above. Define a time span in seconds for dependency delay.

After the master sensor for this dependency comes back to an Up status, monitoring of the dependent objects is additionally delayed by the defined time span. This can prevent false alarms, for example, after a server restart, by giving systems more time for all services to start up. Enter an integer value.

icon-i-round-redThis setting is not available if you set this sensor to Use parent or to be the Master sensor for parent. In this case, define delays in the parent device settings or in its parent group settings.

Access Rights

Click inherited_settings_button to interrupt the inheritance. See section Inheritance of Settings for more information.

Setting

Description

User Group Access

Define the user groups that have access to the sensor. You see a table with user groups and group access rights. The table contains all user groups in your setup. For each user group, you can choose from the following group access rights:

  • Inherited: Inherit the access rights settings of the parent object.
  • No access: Users in this user group cannot see or edit the sensor. The sensor neither shows up in lists nor in the device tree.
  • Read access: Users in this group can see the sensor and view its monitoring results. They cannot edit any settings.
  • Write access: Users in this group can see the sensor, view its monitoring results, and edit its settings. They cannot edit its access rights settings.
  • Full access: Users in this group can see the sensor, view its monitoring results, edit its settings, and edit its access rights settings.

icon-square-cyanFor more details on access rights, see section Access Rights Management.

Using Wildcards

You can use wildcards in the IP Address/DNS Name in the device settings. Wildcards that apply to only one level of the domain name are supported.

Example

Result

*.wildcard.com for www.wildcard.com

Works

api.wildcard.com for api.wildcard.com

Works

contoso.com for contoso.com

Works

*.subapi.subapi2.wildcard.com for de.subapi.subapi2.wildcard.com

Works

*. *.wildcard.com for www.de.wildcard.com

Not supported

*.wildcard.com for de.subapi.wildcard.com

Doesn't work

www.contoso.com for contoso.com

Doesn't work

subapi.*.wildcard.com for subapi.dns.wildcard.com

Doesn't work

Edit Channels

To change display settings, spike filtering, and limits, switch to the sensor's Overview tab and click the gear icon of a specific channel. For detailed information, see section Sensor Channel Settings.

Notification Triggers

Click the Notification Triggers tab to change notification triggers. For detailed information, see section Sensor Notification Triggers Settings.

Others

For more general information about settings, see section Object Settings.

Sensor Settings Overview

For information about sensor settings, see the following sections: