Protecting Pub Sub Topics

Note: pubsub-topic protection is a work in progress, and its implementation is in a feature branch.

VIP authorization enables VOLTTRON platform owners to protect pub/sub topics. More specifically, a platform owner can limit who can publish to a given topic. This protects subscribers on that platform from receiving messages (on the protected topic) from unauthorized agents.

Example

To protect a topic, add the topic name to $VOLTTRON_HOME/protected_topics.json. For example, the following protected-topics file declares that the topic foo is protected:

{
   "write-protect": [
      {"topic": "foo", "capabilities": ["can_publish_to_foo"]}
   ]
}

Note: The capability name can_publish_to_foo is not special. It can be any string, but it is easier to manage capabilities with meaningful names.

Now only agents with the capability can_publish_to_foo can publish to the topic foo. To add this capability to authenticated agents, edit the file $VOLTTRON_HOME/auth.json:

{
  "allow": [
    {"user_id": "Alice", "capabilities" : ["can_publish_to_foo"], "credentials": "CURVE:abc...", },
    {"user_id": "Bobby", "credentials": "CURVE:xyz...", },
  ]
}

(The credentials are abbreviated to simplify the example.)

Alice's agents (i.e., agents that have been authenticated using Alice's credentials) can publish to topic foo. That is, Alice's agents can call:

self.vip.pubsub.publish('pubsub', 'foo', message='Here is a message')

Because Bobby's agents do not have the necessary capabilities, if those agents try to publish to topic foo they will get an exception:

to publish to topic "foo" requires capabilities ['can_publish_to_foo'], but capability list [] was provided

Regular Expressions

Topic names in $VOLTTRON_HOME/protected_topics.json can be specified as regular expressions. To an regular expression in the topic name begin and end the name with a "/". For example:

{
   "write-protect": [
      {"topic": "/foo/*.*/", "capabilities": ["can_publish_to_foo"]}
   ]
}

This protects topics such as foo/bar and foo/anything.

Ideas for Improvement

Read Protection

Currently, pub/sub protection can only write-protect topics. This is useful when protecting the integrity of topic's messages. To protect message confidentiality, we need a read-protection mechanism for pub/sub.

Usability

Currently, JSON files have to be manually edited to protect a pub/sub topic. It would be nice to have an interface in volttron-ctl and/or VOLTTRON Central for managing protected topics.