DBREACH: Stealing from Databases Using Compression Side Channels.

We introduce new compression side-channel attacks against database storage engines that simultaneously support compression of database pages and encryption at rest. Given only limited, indirect access to an encrypted and compressed database table, our attacks extract arbitrary plaintext with high accuracy. We demonstrate accurate and performant attacks on the InnoDB storage engine variants found in MariaDB and MySQL as well as the WiredTiger storage engine for MongoDB. Our attacks overcome obstacles unique to the database setting that render previous techniques developed to attack TLS ineffective. Unlike the web setting, where the exact length of a compressed and encrypted message can be observed, we make use of only approximate ciphertext size information gleaned from file sizes on disk. We amplify this noisy signal and combine it with new attack heuristics tailored to the database setting to extract secret plaintext. Our attacks can detect whether a random string appears in a table with > 90% accuracy and extract 10-character random strings from encrypted tables with > 95% success.