Outsourcing software middlebox (aka. virtual network function) to third-party service provider, like public cloud, has been a recent trend for many well-known benefits. However, redirecting a large influx of raw traffic from enterprises to the service providers, who are often outside the traditional trust domain, raises severe security concerns. Over the past few years, steady progress has been made towards enabling the middlebox functionalities without revealing sensitive traffic. Following the direction, in this paper, we present LightBox, the first system that can drive full-stack protected stateful middleboxes at native speed. Similar to existing hardware-assisted designs, LightBox is built on top of SGX enclave. But, different from all prior systems, LightBox is designed to further address two new challenges that, surprisingly, are largely overlooked in the literature. First, LightBox enables enterprises to safely forward the packets intended for processing to the enclaved middlebox with all metadata, including low-level packet headers, packet size, count and timestamps, fully protected. Studies have shown that such metadata can be information-rich and potentially exploited by many traffic analysis attacks. Second, LightBox achieves very efficient in- enclave stateful middlebox processing within the highly constraint enclave space, without incurring unreasonably high overhead. The confidentiality, integrity, and freshness of the flow states are always ensured throughout our efficient state management procedures. Evaluations show that LightBox, with all the extra security benefits, can still perform packet I/O at 10Gbps line rate. Even when tracking 600K flows, LightBox can obtain 3.5X to 30X performance speedup than direct adoption of SGX, while incurring negligible packet delay (<1{\mu}s) for most test cases.
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