Applying consensus and replication securely with FLAQR

TL;DR

This paper introduces FLAQR, a core calculus with a type system that enables secure, high-level programming of distributed systems using heterogeneous quorum protocols, ensuring confidentiality, integrity, and availability.

Contribution

It presents FLAQR, a novel calculus with a type system that enforces security and correctness properties for distributed applications employing quorum replication protocols.

Findings

Type system guarantees no security violations in well-typed programs

Noninterference theorems characterize confidentiality and integrity

Liveness theorem ensures progress under certain fault conditions

Abstract

Availability is crucial to the security of distributed systems, but guaranteeing availability is hard, especially when participants in the system may act maliciously. Quorum replication protocols provide both integrity and availability: data and computation is replicated at multiple independent hosts, and a quorum of these hosts must agree on the output of all operations applied to the data. Unfortunately, these protocols have high overhead and can be difficult to calibrate for a specific application's needs. Ideally, developers could use high-level abstractions for consensus and replication to write fault-tolerant code by that is secure by construction. This paper presents Flow-Limited Authorization for Quorum Replication (FLAQR), a core calculus for building distributed applications with heterogeneous quorum replication protocols while enforcing end-to-end information security. Our type system ensures that well-typed FLAQR programs cannot_fail_ (experience an unrecoverable error) in ways that violate their type-level specifications. We present noninterference theorems that characterize FLAQR's confidentiality, integrity, and availability in the presence of consensus, replication, and failures, as well as a liveness theorem for the class of majority quorum protocols under a bounded number of faults.