Edit: To clarify, this question is all about whether we should insist on implementing TLS for internal communications over public cloud tenants as a man-in-the-middle risk reduction control, given the complexity and sophistication required to apply MiTM techniques on an SDN-based network as opposed to on-premises networks, and given the threat model excludes state-sponsored, organized crime, advanced adversaries. The implementation does not come for free as it has an operational cost, noticeable performance footprint, and other factors.
Background
The question is about assessing the actual feasibility of exploiting Man-in-the-middle attacks over a public could customer's internal network, while assessing the benefits and caveats of implementing TLS over internal communications as a risk reduction control.
It is well known that implementing TLS everywhere is considered to be a security best practice. However, when it boils down to the ROI, the TLS overhead (even the slightest) versus the actual guarantees provided for an SDN (Software-defined network) based internal network, it raises doubts.
Scenario
You are a security consultant for a B2C company whose infrastructure is hosted on one of the public cloud providers. You provide TLS from the external clients but offload it right after it reaches the load balancer at the entrance of your K8s cluster or VMs. The question on the table is whether to implement TLS past the load balancer, so it would be end-to-end encryption. The threat model does not include state-sponsored adversaries or advanced crime groups.
Implementing TLS for the components beyond the load balancer for the sake of best practices does not hold ground, the performance hit is around %2-3 and so it increases the operational costs (expanded machine resources, certificate management, etc).
The Question
And with that background the question is as follows:
Given the network stack is based on the SDN of the cloud provider which requires significant effort to be able to eavesdrop in the first place and to execute part of the MiTM techniques (e.g., ARP spoofing) over the SDN controller, is it really necessary to implement TLS for a threat model that does not include the top tier threat actors? are the benefits out weights the costs?
