From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Phil Sutter <phil@nwl.cc>,
Fernando Fernandez Mancera <ffmancera@riseup.net>,
netfilter-devel@vger.kernel.org
Subject: Re: [PATCH nft v2 1/6] osf: add version fingerprint support
Date: Thu, 14 Mar 2019 21:07:37 +0100 [thread overview]
Message-ID: <20190314200737.erhjrhoaciclapsn@salvia> (raw)
In-Reply-To: <20190314173454.GA19244@orbyte.nwl.cc>
On Thu, Mar 14, 2019 at 06:34:54PM +0100, Phil Sutter wrote:
> Hi,
>
> On Thu, Mar 14, 2019 at 02:58:40PM +0100, Pablo Neira Ayuso wrote:
> > Hi,
> >
> > On Thu, Mar 14, 2019 at 12:14:23PM +0100, Fernando Fernandez Mancera wrote:
> > > Hi,
> > >
> > > I have been thinking more about this today. I don't know how access to
> > > the right-hand-side string from the kernel if it is possible. Sorry if
> > > the question is very dumb, but I may lack experience with the nft
> > > registers and RHS data of an expression.
> >
> > I think you can hide flags from json, which is what Phil suggests, I
> > mean, just infer version flags from the syntax, ie. if
> > "genre::version" is used, then set of the version flag.
> >
> > I think Phil is not suggesting kernel changes.
>
> Actually I'm still in the process of understanding how all this works.
> What I got so far is (correct me if I'm wrong): osf expr does the
> fingerprinting and returns a string which relational expr compares to
> right-hand side. This new version flag defines whether osf expr adds the
> version to returned string or not.
>
> Assuming the above is correct, my suggestion of making the flag option
> implicit does not quite hold, at least not without painful
> postprocessing of relational statement in userspace.
>
> Right now this all seems to me like enabling multiple comparisons within
> a single relational, i.e. one for genre and the other for version.
> Nftables doesn't quite do such things. E.g. matching on two TCP header
> fields requires two relationals, e.g. 'tcp dport 22 tcp sport > 1024'.
> Internally then, these two statements may be combined into a single
> payload match if suitable.
The osf expression returns a string with the OS genre, and if the
version flag is set on, it appends the version to this string, ie.
genre + version.
This allows us to build maps, ie.
meta mark set osf genre { "linux" : 0x10, "windows" : 0x20, "macos" : 0x40 }
But, with this new version, you could also do:
meta mark set osf genre { "linux::4.0" : 0x11, "linux::3.0" : 0x12, ...}
and so on.
So I see this version thing as a extended matching.
The osf engine actually _already_ finds a precise matching, ie. genre
+ version, since the fingerprint is per genre + version. But you can
just decide to match on the genre (eg. linux).
> Applying the same logic to osf expression, we would implement 'osf name
> foo osf version 3.141' and add 'osf_try_merge()' routine to
> 'rule_postprocess()' which tries to combine the two statements.
> Obviously, this is quite a bit of extra work, not sure if feasible.
I think the discussion here is the syntax, ie.
osf genre "Linux::4.10"
vs.
osf genre "Linux" version "4.10"
This only requires changes to the userspace nftables side, if you
prefer this syntax, which is what I understand you would like to see,
right?
The use of the colon, which comes from the pf.os file:
512:64:0:44:M*: Linux:2.0:3x:Linux 2.0.3x
^^^^^^^^^
Then, this allows us to match for "Linux:2.0".
Thanks!
next prev parent reply other threads:[~2019-03-14 20:07 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-11 15:14 [PATCH nft v2 1/6] osf: add version fingerprint support Fernando Fernandez Mancera
2019-03-11 15:14 ` [PATCH nft v2 2/6] json: osf: add version json support Fernando Fernandez Mancera
2019-03-11 15:14 ` [PATCH nft v2 3/6] tests: py: add osf tests with versions Fernando Fernandez Mancera
2019-03-11 15:14 ` [PATCH nft v2 4/6] doc: add osf version option to man page Fernando Fernandez Mancera
2019-03-11 15:14 ` [PATCH nft v2 5/6] files: osf: update pf.os with newer OS fingerprints Fernando Fernandez Mancera
2019-03-11 15:14 ` [PATCH nft v2 6/6] files: pf.os: merge the signatures spllited by version Fernando Fernandez Mancera
2019-03-13 9:44 ` [PATCH nft v2 1/6] osf: add version fingerprint support Phil Sutter
2019-03-13 10:14 ` Fernando Fernandez Mancera
2019-03-13 11:27 ` Phil Sutter
2019-03-13 14:15 ` Fernando Fernandez Mancera
2019-03-13 15:06 ` Phil Sutter
2019-03-13 15:22 ` Fernando Fernandez Mancera
2019-03-13 15:34 ` Phil Sutter
2019-03-13 16:46 ` Fernando Fernandez Mancera
2019-03-14 11:14 ` Fernando Fernandez Mancera
2019-03-14 13:58 ` Pablo Neira Ayuso
2019-03-14 17:34 ` Phil Sutter
2019-03-14 18:24 ` Fernando Fernandez Mancera
2019-03-15 10:03 ` Phil Sutter
2019-03-15 17:13 ` Pablo Neira Ayuso
2019-03-15 20:21 ` Fernando Fernandez Mancera
2019-03-16 9:05 ` Pablo Neira Ayuso
2019-03-17 17:10 ` Fernando Fernandez Mancera
2019-03-18 17:42 ` Phil Sutter
2019-03-19 11:06 ` Pablo Neira Ayuso
2019-03-20 13:46 ` Phil Sutter
2019-03-21 8:32 ` Pablo Neira Ayuso
2019-03-21 11:15 ` Phil Sutter
2019-03-21 11:18 ` Pablo Neira Ayuso
2019-03-21 14:06 ` Phil Sutter
2019-03-21 16:57 ` Pablo Neira Ayuso
2019-03-21 18:14 ` Phil Sutter
2019-03-14 20:07 ` Pablo Neira Ayuso [this message]
2019-03-14 20:13 ` [PATCH nft v2 1/6] osf: add version fingerprint supportg Pablo Neira Ayuso
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