Date: Sun, 13 Mar 2011 22:05:52 +0000 From: RW <rwmaillists@googlemail.com> To: freebsd-security@freebsd.org Subject: Re: It's not possible to allow non-OPIE logins only from trusted networks Message-ID: <20110313220552.5b79de13@gumby.homeunix.com> In-Reply-To: <1300050377.5900.12.camel@w500.local> References: <1299682310.17149.24.camel@w500.local> <alpine.BSF.2.00.1103100147350.1891@qvfongpu.qngnvk.ybpny> <1299769253.20266.23.camel@w500.local> <2E5C0CE8-4F70-4A4D-A91D-3274FD394C80@elvandar.org> <1299784361.18199.4.camel@w500.local> <20110310202653.GG9421@shame.svkt.org> <1299798547.20831.59.camel@w500.local> <20110313204054.GA5392@server.vk2pj.dyndns.org> <1300050377.5900.12.camel@w500.local>
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On Sun, 13 Mar 2011 21:06:17 +0000 Miguel Lopes Santos Ramos <mbox@miguel.ramos.name> wrote: >=20 > Seg, 2011-03-14 =E0s 07:40 +1100, Peter Jeremy escreveu: > > On 2011-Mar-10 23:09:07 +0000, Miguel Lopes Santos Ramos > > <mbox@miguel.ramos.name> wrote: > > >- The objection on S/KEY on that wiki page, that it's possible to > > >compute all previous passwords, is a bit odd, since past passwords > > >won't be used anymore. > >=20 > > One weakness of S/KEY and OPIE is that if an attacker finds the > > password (response) for sequence N then they can trivially determine > > the response for any sequence > N. This could occur if (eg) you > > have a printout of OPIE keys and are just crossing them off (which > > was a common recommendation prior to smart phones etc) - an > > attacker just needs to memorise the lowest N and response. >=20 > Ok, admittedly, it took me a while to see in what way that could be a > weekness. It's a bit like hoping for a little remaining security after > the password list was compromised. It means they can compute keys that they already have on the printout plus obsolete keys. In what sense is that a weakness? IIRC there is/was a weakness in FreeBSD's OPIE implementation in that it's susceptible to rainbow table attacks - I think part of the hash is discarded.
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