BigFoot: Exploiting and Mitigating Leakage in Encrypted Write-Ahead Logs

TL;DR

This paper demonstrates that encrypted write-ahead logs can leak sensitive information through size patterns and introduces BigFoot, a modification that mitigates this leakage to enhance database security.

Contribution

The paper reveals size-based leakage in encrypted logs and presents BigFoot, a novel WAL modification to prevent such information leaks.

Findings

Encrypted write sizes reveal sensitive data patterns

BigFoot effectively reduces size leakage

Enhanced security against storage-based attacks

Abstract

Modern databases and data-warehousing systems separate query processing and durable storage. Storage systems have idiosyncratic bugs and security vulnerabilities, thus attacks that compromise only storage are a realistic threat. In this paper, we show that encryption alone is not sufficient to protect databases from compromised storage. Using MongoDB WiredTiger as a concrete example, we demonstrate that sizes of encrypted writes to a durable write-ahead log can reveal sensitive information about the inputs and activities of MongoDB applications. We then design, implement, and evaluate BigFoot, a WAL modification that mitigates size leakage.