Date: Thu, 6 Jun 2013 14:19:50 +1000 From: Michael Samuel <mik@...net.net> To: Solar Designer <solar@...nwall.com> Cc: oss-security@...ts.openwall.com Subject: Re: CVE Request: pwgen I've done some further analysis of the program after reading the previous thread, and I think there needs to be CVEs and fixes for: - When used from a non-tty passwords are trivially weak by default (first reported by Solar Designer) - Phonemes mode has heavy bias and is enabled by default (first reported by Solar Designer) - Silent fallback to insecure entropy (first reported by Jean-Michel Vourgère) (Debian bug #672241 - tagged as "wishlist") - Secure mode has bias towards numbers and uppercase letters I've attached a patch that fixes most issues - it doesn't solve the bias towards numbers, because it's caused by requiring at-least one number per password - so in an 8 character password there'd have to be 0.1 numbers to avoid bias. There's an argument to be made for removing the at-least-one rule, but if the system that password is being used with has those rules, it doesn't fix the problem anyway. Perhaps a separate flag for that? The changes are: - Print a message and abort() of there's trouble opening or reading /dev/urandom (So apport should pick up any packages that have been using insecure entropy) - Make "-s" the default - Add an argument --insecure-phonemes (or -P) - Non-tty passwords are now as secure as tty - Require lower-case characters be present to even out some bias - Pull in passwdqc as a Suggests on the debian package - pwqgen can generate sane random passphrases I can't imagine any reasonable use-case for the non-tty defaults (except maybe combining with espeak as an enhanced interrogation technique), and you can be certain that there's some people out there with it embedded in a script that's generating useless passwords. For phonemes mode in general, the bias is extreme, there are a limited number of possible combinations and it is generally not suitable for security purposes. I have some fairly detailed analysis of it, but I believe this list has a no-exploits policy... Regards, Michael On 28 May 2013 11:47, Solar Designer <solar@...nwall.com> wrote: > On Tue, May 28, 2013 at 01:33:48AM +0000, Michael Samuel wrote: > > The default mode of this program generates extremely low entropy > passwords - > > It is probably worth changing the default to "secure" mode and removing > > phonemes mode, to avoid putting users at risk. > > Yes. You have seen the thread on pwgen from last year, right? - > > http://www.openwall.com/lists/oss-security/2012/01/22/6 > > (Use the "thread-prev" link for more messages from that thread.) > > Alexander > Content of type "text/html" skipped Download attachment "pwgen-security.patch" of type "application/octet-stream" (6141 bytes)
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