Internal/external domains

Krannich, Bernd <bernd.krannich@...>

Hi all,

Dr. Nic’s blog post [1] addresses a requirement that we keep hearing frequently: To have certain applications that can only be accessed from other apps running in the same Cloud Foundry deployment.

I wanted to check with the community here to see if anybody has come across this requirement as well. Is this something one should actually be advocating in terms of architecture?

Also, the solution suggested in [1] in our opinion is prone to bypassing if implemented in the described way (see top-most comment in the same blog post). Of course, one could work around that by terminating SSL at the two load balancers, introspecting the header fields there. On the other hand, this requires a much more complex “internal/external” DNS setup.

A logical next step would be to extend the requirement to only allow calls from apps being deployed into certain orgs and spaces. This can no longer be achieved by a setup “external” to CF given that apps from all types of orgs and spaces are usually deployed on the very same runners with calls being “indistinguishable” once a call has left the runner.

As alternatives, we came up with the following potential options:

1. Avoiding the notion of “private” services altogether, making sure that each application is secured by - for example - a JWT token carrying a shared secret.
2. Using messaging via a backing service instead of HTTP-based communication.
3. Recently suggested/implemented CF functionality like “container networking for applications” [2] (what’s the status on this one, actually?) and “Context Path Routing” [3] (this was discussed on the mailing list some time back, even though I’m not sure how you would actually use it to solve the above scenario). Is any of that allowing to implement the above requirement?

Any thoughts, opinions, suggestions are welcome.

Thanks in advance,


Bernd Krannich
Products & Innovation Technology
Dietmar-Hopp-Allee 16
69190 Walldorf Germany

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