Werk #6788: Notification spooler: Fixed deserialization of arbitrary input

The notification daemon of one site connects to the notification daemon of another site to exchange notifications between both sites.

The messages that are sent between the notification daemons were encoded in an insecure format which allowed code injections between the communication partners. This means it was possible to inject code from one notification spooler to another.

We have now changed the message format to a secure alternative which prevents code injections.

To be able to perform this transition without loosing notifications and preventing subtile incompatibilities we decided to keep the new format disabled by default for all sites created with Check_MK 1.4 and 1.5. This means your installation will still be affected by this issue by default after updating.

However, once you have updated all your sites to at least 1.4.0p37 in case of the 1.4.0 branch or or at least 1.5.0p7 in case of the 1.5.0 branch you can change the main configuration option "Notification Spooler insecure messages" to "off" and activate the new configuration. Once you have done this all notification spoolers will use the new secure message format.

Please note that the 1.6 notification spoolers will always use the new message format and not be compatible to the old message format of the 1.5 notification spoolers anymore. If you plan to use 1.5 and 1.6 together during migration you will have to ensure that you use the new message format in your 1.5 sites.

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