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Transient execution attacks leveraging port contention
From: Mathias Payer <mathias.payer () nebelwelt net>
Date: Wed, 6 Mar 2019 21:35:17 +0100
Hi there, # Intro We (a team of researchers from EPFL and IBM Research) are releasing details about a new transient execution attack that leaks secrets from an uncooperating process through a combination of speculative execution (we use branch target injection) and port contention (for SMT threads). # SMoTherSpecre We introduce SMoTher, a port-based side channel that leaks information on what instruction sequences were executed by the victim due to port contention. We precisely characterize and measure this side channel. Second, we combine SMoTher with a speculative execution attack to leak register values or memory values (that are likely in caches). We call the combined side channel SMoTherSpectre. Our attack requires two gadgets: a BTI gadget that speculatively redirects execution to a SMoTher gadgets that, through port contention, leaks which branch was taken. By competing for execution ports, the attacker measures if the JCC in the SMoTher gadget was either taken or not taken (based on the execution profiles of either branch). We first analyze the capabilities of this transient execution attack and find that we can guess one bit with 60% probability (on one try) and 98% probability (on 9 tries). Second, we target OpenSSL where we leverage an indirect call that selects the cipher to encrypt/decrypt as BTI target to compare individual bytes of the plaintext to zero (through a SMoTher gadget). See the blog post for more details: http://nebelwelt.net/blog/20190306-SMoTherSpectre.html The paper draft is at: https://arxiv.org/abs/1903.01843 The PoC is at: https://github.com/HexHive/SMoTherSpectre In our PoC we target Intel Skylake 6700 CPUs. # Disclosure We discovered SMoTher in June 2018 and SMoTherSpectre in November 2018. We disclosed the details and PoC to Intel early December 2018. Our IBM research collaborators finished the internal disclosure process on February 28. # Credit Atri Bhattacharyya, Alexandra Sandulescu, Matthias Neugschwandtner, Alessandro Sorniotti, Babak Falsafi, Mathias Payer, and Anil Kurmus As always, feedback, comments, and discussions are welcome. Best, Mathias (and all collaborators)
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- Transient execution attacks leveraging port contention Mathias Payer (Mar 06)