Date: Fri, 21 Aug 2015 00:41:25 +0300 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: BENCHMARK_LENGTH bugs Kai, On Fri, Aug 21, 2015 at 01:13:15AM +0800, Kai Zhao wrote: > On Mon, Aug 17, 2015 at 11:22 PM, Solar Designer <solar@...nwall.com> wrote: > > For a start, maybe --test-full should warn about formats that have: > > > > (benchmark_length == -1 && salt_size != 0) || > > (benchmark_length == 0 && salt_size == 0) > > > > The latter combination is strictly an error (can't benchmark for > > different salt counts when there are no salts), so perhaps even the > > non-full --test should complain when it sees it. > > > > The former is sometimes valid: we use it on very slow hashes (and > > non-hashes), where the results would be effectively the same anyway (key > > setup overhead is negligible). Perhaps we'll need a (growing) whitelist > > of formats for which --test-full should mute this warning. Note that I had suggested a whitelist to mute a warning, but what you implemented is totally different: > I think I should add more slow hashes. The top slow hashes are in the > attached file. You implemented a list of formats for which an extra check is performed. This isn't useful at all. So please just drop the "else if (is_slow_hash(format->params.label))" for now. You may later replace it with a benchmark, as discussed in the previous message I just sent. For now: You may instead complete "if (format->params.benchmark_length == -1 && format->params.salt_size != 0)", but not with a slow hash check (as you have in commented out code in there). Rather, you first have it report warnings unconditionally, and then start building a whitelist of formats for which this warning should be muted. Or you can have the code run a benchmark and automatically mute the warning if the two results are too similar (difference below 1%). Alexander
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