Date: Fri, 3 Apr 2015 11:58:37 +0100 From: "Robert N. M. Watson" <rwatson@FreeBSD.org> To: Hans Petter Selasky <hps@selasky.org> Cc: Mateusz Guzik <mjguzik@gmail.com>, Ian Lepore <ian@freebsd.org>, svn-src-all@freebsd.org, src-committers@freebsd.org, Gleb Smirnoff <glebius@FreeBSD.org>, svn-src-head@freebsd.org Subject: Re: svn commit: r280971 - in head: contrib/ipfilter/tools share/man/man4 sys/contrib/ipfilter/netinet sys/netinet sys/netipsec sys/netpfil/pf Message-ID: <A91D1F45-FCF0-414B-97BF-11CB906DD268@FreeBSD.org> In-Reply-To: <551E6E72.8050208@selasky.org> References: <201504012226.t31MQedN044443@svn.freebsd.org> <20150402123522.GC64665@FreeBSD.org> <20150402133751.GA549@dft-labs.eu> <20150402134217.GG64665@FreeBSD.org> <20150402135157.GB549@dft-labs.eu> <1427983109.82583.115.camel@freebsd.org> <20150402142318.GC549@dft-labs.eu> <20150402143420.GI64665@FreeBSD.org> <20150402153805.GD549@dft-labs.eu> <alpine.BSF.2.11.1504021657440.27263@fledge.watson.org> <551D8143.4060509@selasky.org> <551D8945.8050906@selasky.org> <8900318B-8155-4131-A0C3-3DE169782EFC@FreeBSD.org> <551D8C6C.9060504@selasky.org> <alpine.BSF.2.11.1504021939390.64391@fledge.watson.org> <551DA5EA.1080908@selasky.org> <551DAC9E.9010303@selasky.org> <358EC58D-1F92-411E-ADEB-8072020E9EB3@FreeBSD.org> <551DEF26.4000403@selasky.org> <4B7DAA59-389F-41AE-99D8-034A7AA61C99@FreeBSD.org> <551E520E.1040708@selasky.org> <6DF5FB51-8135-4144-BD3A-6E4127A23AA7@FreeBSD.org> <551E5C38.7070203@selasky.org> <78DD67BD-621C-451D-8E30-EC9BF396716F@FreeBSD.org> <551E6E72.8050208@selasky .org>
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On 3 Apr 2015, at 11:41, Hans Petter Selasky <hps@selasky.org> wrote: > On 04/03/15 11:31, Robert N. M. Watson wrote: >> TCP/IP covert and side channels >=20 > Hi, >=20 > Can you provide a reference to a document in the area of "TCP/IP = covert and side channels" which is considered state of the art? Or is = this litterature not publically available? I'm not sure there's a recent survey article on the topic, but a keyword = search of the ACM Digital Library returns 493 articles for "TCP covert = channel". The second is this article by my colleague Steven Murdoch: http://www.cl.cam.ac.uk/~sjm217/papers/ih05coverttcp.pdf It contains a nice introduction to the concepts and 2005 framing, but = there has been significant work in this area since that was published. Note that the goal of a stronger IP ID scheme is *not* randomness per = se: it is a blend of non-predictability with maximising the interval of = non-reuse of IP IDs. Simple use of a random number generator = accomplishes the former adequately -- but the latter not at all, as it = makes no guarantees about reuse interval -- and in fact can experience = pessimal reuse intervals in normal operation. Mike Silbersack did quite = a bit of work in this area in FreeBSD about a decade ago and is the = person you want to talk to to understand the IP ID issue better. However, the more fundamental issue, regardless of covert and side = channels, is that we share the IP ID space across many 2-tuples. = Addressing that issue would markedly improve the robustness of large UDP = datagram support -- while as a side effect reducing covert and side = channels far more effectively than randomisation. Robert=
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