Secure Cloud Computing with Virtualized Network Infrastructure

HotCloud 10By Xuanran Zong

Cloud Security

• Two end of the spectrum– Amazon EC2• Shared, public cloud• Resource multiplexing, low cost• Low security

– Government cloud• Dedicated infrastructure• High cost• High security

Design Goal

• Isolation• Transparency• Location independence• Easy policy control• Scalability (?)• Low cost

Conventional data center architecture

• VLAN to ensure security– Scalability issue: can take up to 4K id– Management and control overhead

• Per-user security policy control– But, how to enforce?• End-host? Not secure enough• Middlebox? Unnecessary traffic

Secure Elastic Cloud Computing

Reference: http://www.usenix.org/events/hotcloud10/tech/slides/hao.pdf

Numbering and addressing

• Each customer has a unique cnet id• VM can be identified by (cnet id, IP)• Each domain has a unique eid• Use VLAN to separate different customer in

the same domain• VLAN id can be reused in different domain

Customer network integration

• Private network can be treated as a special domain where VPN is used to connect it to core domain

Central controller

• Address mapping – VM MAC <-> (cnet id, IP)– VM MAC <-> eid– eid <-> FE MAC list– (cnet id, eid) <-> VLAN id

• Policy databas– E.g. packet from customer A are first forwarded to

firewall F.

Forwarding elements

• Address lookup and mapping– FE MAC of the destination domain– VLAN ID

• Policy enforcement– By default, packets designated to a different

customer are dropped• Tunneling between FEs– Encapsulate another MAC header

Data forwarding

Reference: http://www.usenix.org/events/hotcloud10/tech/slides/hao.pdf

How does it solve the limitation?

• VLAN scalability– Partition network into smaller edge domain, each

maintains its own VLAN– VLAN id can be reused

• Per-user security– Security policy enforced by FE– CC stores security policies for all customers

Discussion

• Security via isolation and access control– Consider the co-residence problem proposed by

“Get off my cloud” paper– Matching Dom0 IP address• Disable traceroute

– Small round-trip time• Every packet needs to go through FE

– Numerically close IP address• Each customer has private IP address

Discussion

• Cached vs installed forwarding table• VM migration– Update CC (eid, VLAN id)

Discussion

• Pros– Security enforcement via isolation and access control– Scalable in terms of number of customers supported

by VLAN– Most networking equipments are off-the-shelf

• Cons?– Scalability? Centralized CC?– Larger round trip time within the same edge domain– Tunneling?