package/mosquitto: security bump to version 1.6.6

package/mosquitto: security bump to version 1.6.6

Fixes a security issue. From the annoncement:

A vulnerability exists in Mosquitto versions 1.5 to 1.6.5 inclusive.

If a client sends a SUBSCRIBE packet containing a topic that consists of
approximately 65400 or more '/' characters, i.e.  the topic hierarchy
separator, then a stack overflow will occur.

The issue is fixed in Mosquitto 1.6.6 and 1.5.9.  Patches for older versions
are available at https://mosquitto.org/files/cve/2019-hier

The fix addresses the problem by restricting the allowed number of topic
hierarchy levels to 200.  An alternative fix is to increase the size of the
stack by a small amount.

https://mosquitto.org/blog/2019/09/version-1-6-6-released/

Also notice that 1.6.5 silently fixed a security issue:

CVE-2019-11778

A vulnerability exists in Mosquitto version 1.6 to 1.6.4 inclusive, known as CVE-2019-11778

If an MQTT v5 client connects to Mosquitto, sets a last will and testament,
sets a will delay interval, sets a session expiry interval, and the will
delay interval is set longer than the session expiry interval, then a use
after free error occurs, which has the potential to cause a crash in some
situations.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>