From: Rich Felker <dalias@aerifal.cx>
To: musl@lists.openwall.com
Subject: Re: crypt* files in crypt directory
Date: Wed, 8 Aug 2012 09:06:23 -0400 [thread overview]
Message-ID: <20120808130622.GJ27715@brightrain.aerifal.cx> (raw)
In-Reply-To: <20120808075233.GJ30810@port70.net>
On Wed, Aug 08, 2012 at 09:52:34AM +0200, Szabolcs Nagy wrote:
> * Solar Designer <solar@openwall.com> [2012-08-08 08:42:35 +0400]:
> > I see that you did this - and I think you took it too far. The code
> > became twice slower on Pentium 3 when compiling with gcc 3.4.5 (approx.
> > 140 c/s down to 77 c/s). Adding -finline-functions
> > -fold-unroll-all-loops regains only a fraction of the speed (112 c/s);
> > less aggressive loop unrolling results in lower speeds.
> >
>
> i thought slowness is a feature in this case..
>
> at least that was the general agreement about the
> size vs speed tradeoff of the des code
Solar's argument is that if you want more slowness, you should just
use a higher iteration count that also affects people trying to crack
your passwords. And being slower at the same count discourages
increasing the count.
Actually this brings up a HUGE DoS vuln in blowfish crypt: with tcb
passwords, a malicious user can put a password with count=31 (it's
logarithmic, so this means 2^31) in their tcb shadow file. This will
cause a root-owned process to eat 100% cpu for hours if not days.
Perform a few simultaneous login attempts and the whole server becomes
unusable.
I don't know how to solve it, but in musl I think we'll have to put a
low limit on count if we're going to support blowfish. Unfortunately I
don't see a good way to make it runtime configurable without
hard-coding additional non-standard config paths, but letting the DoS
bug slip in is not acceptable.
Rich
next prev parent reply other threads:[~2012-08-08 13:06 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-21 15:23 Łukasz Sowa
2012-07-21 17:11 ` Solar Designer
2012-07-21 20:17 ` Rich Felker
2012-07-22 16:23 ` Łukasz Sowa
2012-07-25 7:57 ` Rich Felker
2012-08-08 2:24 ` Rich Felker
2012-08-08 4:42 ` Solar Designer
2012-08-08 5:28 ` Rich Felker
2012-08-08 6:27 ` Solar Designer
2012-08-08 7:03 ` Daniel Cegiełka
2012-08-08 7:24 ` Solar Designer
2012-08-08 7:42 ` Daniel Cegiełka
2012-08-08 21:48 ` Rich Felker
2012-08-08 23:08 ` Isaac Dunham
2012-08-08 23:24 ` John Spencer
2012-08-09 1:03 ` Isaac Dunham
2012-08-09 3:16 ` Rich Felker
2012-08-09 3:36 ` Solar Designer
2012-08-09 7:13 ` orc
2012-08-09 7:28 ` Rich Felker
2012-08-09 7:29 ` Solar Designer
2012-08-09 10:53 ` Solar Designer
2012-08-09 11:58 ` Szabolcs Nagy
2012-08-09 16:43 ` Solar Designer
2012-08-09 17:30 ` Szabolcs Nagy
2012-08-09 18:22 ` Rich Felker
2012-08-09 23:21 ` Rich Felker
2012-08-10 17:04 ` Solar Designer
2012-08-10 18:06 ` Rich Felker
2012-08-09 21:46 ` crypt_blowfish integration, optimization Rich Felker
2012-08-09 22:21 ` Solar Designer
2012-08-09 22:32 ` Rich Felker
2012-08-10 17:18 ` Solar Designer
2012-08-10 18:08 ` Rich Felker
2012-08-10 22:52 ` Solar Designer
2012-08-08 7:52 ` crypt* files in crypt directory Szabolcs Nagy
2012-08-08 13:06 ` Rich Felker [this message]
2012-08-08 14:30 ` orc
2012-08-08 14:53 ` Szabolcs Nagy
2012-08-08 15:05 ` orc
2012-08-08 18:10 ` Rich Felker
2012-08-09 1:51 ` Solar Designer
2012-08-09 3:25 ` Rich Felker
2012-08-09 4:04 ` Solar Designer
2012-08-09 5:48 ` Rich Felker
2012-08-09 15:52 ` Solar Designer
2012-08-09 17:59 ` Rich Felker
2012-08-09 21:17 ` Rich Felker
2012-08-09 21:44 ` Solar Designer
2012-08-09 22:08 ` Rich Felker
2012-08-09 23:33 ` Rich Felker
2012-08-09 6:03 ` Rich Felker
-- strict thread matches above, loose matches on Subject: below --
2012-07-17 9:40 Daniel Cegiełka
2012-07-17 17:51 ` Rich Felker
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