The message queue is a critical piece of infrastructure that supports a number of OpenStack services but is most strongly associated with the Compute service. Due to the nature of the message queue service, Alice and Bob have similar security concerns. One of the larger concerns that remains is that many systems have access to this queue and there is no way for a consumer of the queue messages to verify which host or service placed the messages on the queue. An attacker who is able to successfully place messages on the queue is able to create and delete VM instances, attach the block storage of any tenant and a myriad of other malicious actions. There are a number of solutions on the horizon to fix this, with several proposals for message signing and encryption making their way through the OpenStack development process.
In this case Alice's controls mimic those Bob has deployed for the public cloud.
Bob assumes that at some point infrastructure or networks underpinning the Compute service may become compromised. Due to this, he recognizes the importance of locking down access to the message queue. To do this Bob deploys his RabbitMQ servers with SSL and X.509 client auth for access control. This in turn limits the capabilities of an attacker who has compromised a system that does not have queue access.
Additionally, Bob adds strong network ACL rulesets to enforce which endpoints can communicate with the message servers. This second control provides some additional assurance should the other protections fail.
