Date: Tue, 16 Feb 2016 20:45:32 +0300 From: Solar Designer <solar@...nwall.com> To: musl@...ts.openwall.com Subject: Re: list of security features in musl On Thu, Feb 11, 2016 at 08:11:19PM +0100, Szabolcs Nagy wrote: > - about 'security feature lists': > the fedora project lists 'sha256 based passwd hash' in glibc > as a security feature, that implementation is > - a denial of service attack vector (computation depends on > key length more than the admin controlled round count). > - arch dependent(!), one can craft a passwd entry such that > only 32bit machines can log in. What do you mean here? 32-bit overflow/wraparound with very high rounds= specification? > - unbounded alloca(!) use was fixed in 2012, long after > fedora added support for it (the reference implementation > in the spec still has the problem, among other issues). > - uses arbitrary sized realloc for the global crypt state > even though 100 bytes would be enough (checks salt len > after reallocation). > - not standard conform c code: aligned attribute, alloca, > section attribute, undefined behaviour: (tmp - (char *) 0). > - meant to be used outside the libc, but secrets are cleared > with memset which can be optimized away. > (i think there are other issues in this sha256-crypt.c, but > the point is: implementation details matter so security check > lists should be taken with a grain of salt.) > > : https://fedoraproject.org/wiki/Security_Features#Glibc_Enhancements > : http://www.openwall.com/lists/musl/2012/08/19/9 Another issue is that SHA-crypt leaks 8 bits via timing (total execution time, not just cache-timing), for no good reason at all (not a tradeoff): "18. repeast the following 16+A times, where A represents the first byte in digest A interpreted as an 8-bit unsigned value add the salt to digest DS" For comparison, bcrypt is not cache-timing-safe, but that's a tradeoff. Alexander
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.