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From Chris Egerton <chr...@confluent.io>
Subject Re: [DISCUSS] KIP-507: Securing Internal Connect REST Endpoints
Date Mon, 19 Aug 2019 19:02:52 GMT
Hi Ryanne,

The reasoning for this is provided in the KIP: "There would be no clear way
to achieve consensus amongst the workers in a cluster on whether to switch
to this new behavior." To elaborate on this--it would be bad if a follower
worker began writing task configurations to the topic while the leader
continued to only listen on the internal REST endpoint. It's necessary to
ensure that every worker in a cluster supports this new behavior before
switching it on.

To be fair, it is technically possible to achieve consensus without using
the group coordination protocol by adding new configurations and using a
multi-phase rolling upgrade, but the operational complexity of this
approach would significantly complicate things for the default case of just
wanting to bump your Connect cluster to the next version without having to
alter your existing worker config files and with only a single restart per
worker. The proposed approach provides a much simpler user experience for
the most common use case and doesn't impose much additional complexity for
other use cases.

I've updated the KIP to expand on points from your last emails; let me know
what you think.

Cheers,

Chris

On Thu, Aug 15, 2019 at 4:53 PM Ryanne Dolan <ryannedolan@gmail.com> wrote:

> Thanks Chris, that makes sense.
>
> I know you have already considered this, but I'm not convinced we should
> rule out using Kafka topics for this purpose. That would enable the same
> level of security without introducing any new authentication or
> authorization mechanisms (your keys). And as you say, you'd need to lock
> down Connect's topics and groups anyway.
>
> Can you explain what you mean when you say using Kafka topics would require
> "reworking the group coordination protocol"? I don't see how these are
> related. Why would it matter if the workers sent Kafka messages vs POST
> requests among themselves?
>
> Ryanne
>
> On Thu, Aug 15, 2019 at 3:57 PM Chris Egerton <chrise@confluent.io> wrote:
>
> > Hi Ryanne,
> >
> > Yes, if the Connect group is left unsecured then that is a potential
> > vulnerability. However, in a truly secure Connect cluster, the group
> would
> > need to be secured anyways to prevent attackers from joining the group
> with
> > the intent to either snoop on connector/task configurations or bring the
> > cluster to a halt by spamming the group with membership requests and then
> > not running the assigned connectors/tasks. Additionally, for a Connect
> > cluster to be secure, access to internal topics (for configs, offsets,
> and
> > statuses) would also need to be restricted so that attackers could not,
> > e.g., write arbitrary connector/task configurations to the configs topic.
> > This is all currently possible in Kafka with the use of ACLs.
> >
> > I think the bottom line here is that there's a number of steps that need
> to
> > be taken to effectively lock down a Connect cluster; the point of this
> KIP
> > is to close a loophole that exists even after all of those steps are
> taken,
> > not to completely secure this one vulnerability even when no other
> security
> > measures are taken.
> >
> > Cheers,
> >
> > Chris
> >
> > On Wed, Aug 14, 2019 at 10:56 PM Ryanne Dolan <ryannedolan@gmail.com>
> > wrote:
> >
> > > Chris, I don't understand how the rebalance protocol can be used to
> give
> > > out session tokens in a secure way. It seems that any attacker could
> just
> > > join the group and sign requests with the provided token. Am I missing
> > > something?
> > >
> > > Ryanne
> > >
> > > On Wed, Aug 14, 2019, 2:31 PM Chris Egerton <chrise@confluent.io>
> wrote:
> > >
> > > > The KIP page can be found at
> > > >
> > > >
> > >
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-507%3A+Securing+Internal+Connect+REST+Endpoints
> > > > ,
> > > > by the way. Apologies for neglecting to include it in my initial
> email!
> > > >
> > > > On Wed, Aug 14, 2019 at 12:29 PM Chris Egerton <chrise@confluent.io>
> > > > wrote:
> > > >
> > > > > Hi all,
> > > > >
> > > > > I'd like to start discussion on a KIP to secure the internal "POST
> > > > > /connectors/<name>/tasks" endpoint for the Connect framework.
The
> > > > proposed
> > > > > changes address a vulnerability in the framework in its current
> state
> > > > that
> > > > > allows malicious users to write arbitrary task configurations for
> > > > > connectors; it is vital that this issue be addressed in order for
> any
> > > > > Connect cluster to be secure.
> > > > >
> > > > > Looking forward to your thoughts,
> > > > >
> > > > > Chris
> > > > >
> > > >
> > >
> >
>

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