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Re: [GNUnet-developers] Camouflage
Re: [GNUnet-developers] Camouflage
Thu, 29 Nov 2012 19:53:32 +0100
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On 11/29/2012 07:26 PM, Bart Polot wrote:
These are my thoughts on the matter, especially point 1:
- The spreading of false info is leads to quite some inefficiency for
the network in general.
- Even if you spread X false adresses for you, "they" can always issue
X+1 search orders/legal procedures and catch you.
- If you are worried about not getting recognized as a GNUnet user, I
think the best way to do this is to run in F2F mode and have your
friends not spread your HELLO at all. If anybody wants anything from
you, he can connect you on mesh level (tunnel through your friends). If
you trust your friends enough to allow them connect to you, you should
trust them not to spread your hello, right? Otherwise, acquire new
friends, repeat ;)
Also, our current spreading of HELLOs of peers that are in 'pure' F2F
mode is inefficient anyway. So adding a way to flag a HELLO as
"F2F-only" which means that other peers must not pass it on (or at least
not with network addresses in it, I guess the public key itself is
harmless), would make sense. We can probably easily do this by, for
example, adding another message type (F2F_HELLO), have F2F-only peers
generate that HELLO and have our processing of F2F_HELLOs make sure that
we do not pass them to other peers.
On 24 November 2012 13:56, LRN <address@hidden
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This is the idea that i've been thinking on.
It should be possible for GNUnet node operator to hide the fact that
his machine runs a GNUnet node.
Ways to achieve this:
1) Fake HELLO messages.
AFAIU, right now anyone can collect HELLO messages (by running a node,
or by querying a hostlist server), and then claim (with certain degree
of sureness) that GNUnet nodes run on all addresses listed in these
messages. Companies that track torrent users do this for BitTorrent.
They may then proceed to actually connect to listed addresses to
verify them, but that is quite another story.
The solution is to spread fake HELLOs with fake public keys and fake
A node should use its private key (key K) as a seed to generate a set
fake of addresses (set A). Then use K and A themselves to generate
fake public key (key F) for each A, thus getting a complete HELLO
message. The use of K as a seed ensures that the node will keep lying
about the same set of addresses (how large that set should be is an
open question) with the same keys, making the fakes more believable
(observer might think that these are real nodes, maintaining their
real HELLOs over time; failure to validate any of them might be blamed
on firewalls, etc).
Address sets will intersect (A1 and A2 generated from K1 and K2 may
share some elements), obviously, although that might not be true for
I expect that address generator will apply some rules to generate
believable addresses (i.e. don't generate invalid IP addresses, like
As an extra, a node could validate generated addresses and do
non-agressive portscanning (or something similar - we're not speaking
only of tcp) on them, to be able to add ports (or other parts of the
address) that look believable to observers.
AFAIU, right now nodes won't gossip about fake HELLOs (i.e. a node
will never tell another node about a HELLO it got, unless it validated
that HELLO). That might need to be changed to allow nodes to choose a
random subset of invalid HELLOs and gossip about them as well.
Otherwise only the node that generated them will be able to spread them.
Not sure about hostlists.
Extra yummy feature - add user-configurable fake templates, which
could have addresses only, or addresses and private keys. GNUnet node
will use templates from time to time (configurable) instead of
generated addresses, and will generate missing template elements.
It would be neat to be able to tell the world that 188.8.131.52 
runs a GNUnet http_server transport on port 80...
This is also too complex, I prefer Bart's idea.
2) Transport disguise.
Modify the protocol to allow clients to ignore initial data sent by
the server, and require clients to be the first ones to speak GNUnet
protocol after connecting (i'm not sure how the protocol works right
now; what a GNUnet node sends to the connected party immediately after
accepting an incoming connection? Does it send anything at all?).
No, clients always first send their peer identity. Transport plugins
are supposed to hang up (or 404 for HTTP) if they are in F2F mode and
the identity is not that of a friend. Naturally, a powerful adversary
can still observe traffic and replay (which will only fail once the
server sends the challenge), but at least adversaries that cannot
monitor your inbound traffic should not be able to simply probe to see
if a host is running GNUnet (if in F2F mode -- otherwise sending any
identity would of course trigger a full handshake). Again, this is the
theory, bugs may exist (in individual plugins) --- there is no easy way
to test this.
A node should send fake data that looks like, say, FTP greeting,
faking a real-life FTP server.
This will prevent casual observers from identifying the node as GNUnet
Non-casual observer should not follow the fake protocol, but proceed
to send a normal GNUnet handshake.
If the node doesn't get a GNUnet handshake as a reply to its fake
greeting, it might either drop the connection, or use some kind of
bogus access control error as an excuse to drop it (i.e. ask for ftp
login/password combo, and then reject all such combos and drop
"clients" that failed to "authenticate" this way).
Well, this point seems to go a bit further --- you want to fully fake a
protocol. The closest we have to that are the HTTP and HTTPS plugins.
Here, both side run a real HTTP(S) session, with the full, standard
HTTPS-handshake first. Again, the client sends its own identity in the
HTTP header, so the server can 404 for non-friends / invalid requests.
This *still* may not prevent a sophisticated attacker from detecting
GNUnet on the host --- we have people here across the hallway that can
identify protocols (IMAP, HTTP, etc.) as they are tunneled over SSL,
just by observing message sizes and timing. So even if your traffic is
encrypted, traffic profiling can tell you a lot about the underlying
protocol. I do not believe in even attempting to defeat this kind of
traffic-profiling attack, as faking another protocol 'perfectly' is
incompatible with reasonable performance in my mind (it gets too close
Or a node should simply remain silent until it gets incoming handshake
They all do. In all of our protocols, the client must talk first.
3) Handshake-first protocol
Besides (2), which may or may not be implemented, don't identify
yourself as GNUnet node until incoming peer sends a handshake, then
drop it, if it doesn't match one of your friends, if you're running in
F2F-only mode. You will be able to hide the fact that you're a GNUnet
node, since only friends will get _anything_ out of you. Other
non-friend (normal or malicious) GNUnet clients will have their
connections dropped after their handshake message.
That's how it works already (modulo unknown bugs).
To make it work both ways, GNUnet should establish a generic session
with TLS encryption first. Again, it's not uncommon for services to
have ports on which clients are expected to connect with an SSL/TLS
session (instead of connecting normally and then issuing StartTLS).
The point here is to use common TLS certificates and TLS connections
for initial authentication (friend nodes will know TLS certificates of
each other in advance). Otherwise your node will not be able to
connect to any of your friends without revealing that it's a GNUnet
node (friend won't identify itself as a GNUnet node initially, until
you send a handshake, thus preventing you from verifying that you've
connected to your friend, not to some man in the middle; and if you
send a GNUnet handshake, you will reveal yourself as GNUnet node to
the other end of the connection, not knowing who might be there). TLS
allows authentication without revealing that nodes are using GNUnet.
And using TLS itself is, thankfully, not illegal yet (and, hopefully,
will never be).
This will have to be a separate transport, since
A) that is somewhat incompatible with existing tcp transport, which
does not rely in TLS at all, AFAIK.
B) Your friend might not be running in F2F-mode only, in which case
you will reveal that you run GNUnet by connecting to your friend on
the same port that other nodes connect to. If there's a separate port,
which only accepts TLSed sessions, and only accepts known friends on
them (at TLS level), it will be much more difficult for non-friends to
identify you. If you make a TLS connection on port A to a machine that
_also_ runs GNUnet on port B, that will not immediately prove that you
are running GNUnet in F2F-only mode.
We already discussed (3) in the past, AFAIR, just making sure that
this discussion sticks somewhere.
Have you tried to configure GNUnet's HTTPS transport via reverse proxy?
(see https://gnunet.org/https-reverse-proxy)? This one goes as far as
running 'real' HTTP inside of the TLS connection, so even simplistic
traffic profiling might not succeed at telling it apart from normal HTTPS.
Did you know that https://gnunet.org/SpeedTest/ and
http://gnunet.org/SpeedTest/ are addresses for a GNUnet peer?
Given that we can already do this, I don't quite see that we'd need
anything else. Now, we might do a "TLS" plugin which runs GNUnet's TCP
over TLS to avoid the HTTP-overhead.
However, in combination with a reverse proxy which essentially allows us
to run a "hidden" GNUnet peer on a normal HTTPS-server (that serves a
normal website as well) the existing HTTPS plugin is the best practical
form of camouflage that I can think of...
 That's what microsoft.com <http://microsoft.com> resolves to,
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GNUnet-developers mailing list
Re: [GNUnet-developers] Camouflage, Matthias Wachs, 2012/11/30