oss-sec mailing list archives
Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations
From: Billy Brumley <bbrumley () gmail com>
Date: Thu, 9 Jun 2016 23:19:38 +0300
The paper very resourceful, and thank you for sharing your thoughts even beyond it!
My pleasure :)
Control over CPU utilization (and thereby cache eviction) can be achieved by a remote attacker: Web applications are influenced remotely by definition, and they are far from slim or localized these days. Keepalives allow to keep the system in a sling with predictable resource utilization including cache fills, as there is not only just data stuffed through some buffers. The question remains if the deterioration of the SNR (*) leaves enough resolution to be useful. This would no longer constitute a cache-based attack with the terrifyingly clear signal, but the sharp edges in the latency that you have demonstrated may contribute to filtering the effect from the noise. While the cause - non-constant-time implementation - remains.
What you are saying is all valid on paper. But when you move to the uarch level, the techniques we are using are very specific --- rdtsc and clflush instructions, paired with targeted malicious performance degradation techniques. When you take away these tools, it really complicates things for an attacker.
Are the orders of magnitude in range?
This is more of an interesting research question that would take maybe six months to definitively answer. BBB
Current thread:
- CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Solar Designer (Jun 08)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Gsunde Orangen (Jun 08)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Alex Gaynor (Jun 08)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Gsunde Orangen (Jun 08)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Marcus Meissner (Jun 08)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Roman Drahtmueller (Jun 08)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Roman Drahtmueller (Jun 08)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Billy Brumley (Jun 08)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Roman Drahtmueller (Jun 09)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Billy Brumley (Jun 09)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Alex Gaynor (Jun 08)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Gsunde Orangen (Jun 08)
- Re: CVE-2016-2178: OpenSSL DSA follows a non-constant time codepath for certain operations Billy Brumley (Jun 08)