Revisiting SSL/TLS Implementations: New Bleichenbacher Side Channels and Attacks presented at DeepSec 2014

by Juraj Somorovsky,

Summary : As a countermeasure against the famous Bleichenbacher attack on RSA based ciphersuites, all TLS RFCs starting
from RFC 2246 (TLS 1.0) propose “to treat incorrectly
formatted messages in a manner indistinguishable from
correctly formatted RSA blocks”. In this talk we show that this objective has not been achieved yet (cf. Table 1): We present four new Bleichenbacher side channels, and three successful Bleichenbacher attacks against the Java Secure Socket Extension (JSSE) SSL/TLS implementation and against hardware security appliances using the Cavium NITROX SSL accelerator chip. Three of these side channels are timing-based, and two of them provide the first timing-based Bleichenbacher attacks on SSL/TLS described in the literature. Our measurements confirmed that all these side channels are observable over a switched network, with timing differences between 1 and 23 microseconds. We were able to successfully recover the PreMasterSecret using three of the four side channels in a realistic measurement setup.