The check ping packets are for detecting spoofing. The malicious
man-in-the-middle already has all the info from Charles simply because
Charles went to his region: UUID, sessionID, secureSessionID, Viewer
EndPoint... everything that we send around to regions. Note that the
info wasn't sniffed, it was given, as we always do. Yeah, what I'm
talking about does not involve sophisticated equipment...
So it can easily launch an agent at WP pretending to be Charles,
spoofing the UDP EndPoint. What it *can't* do is to *receive* the UDP
PingCheck packets that WP sends to that EndPoint. The best it can do is
to send a reply guessing what the seq number might be.
Frisby, Adam wrote:
I think the 3 ping check is technically invalid. Anyone capable of
capturing a packet and sniffing a session/securesession ID out of it,
is quite capable of injecting our check packets in too.
Adam
*From:* [email protected]
[mailto:[email protected]] *On Behalf Of *Diva Canto
*Sent:* Tuesday, 24 February 2009 9:03 PM
*To:* [email protected]
*Subject:* Re: [Opensim-dev] User Authentication
Mike Mazur wrote:
Hi,
On Tue, 24 Feb 2009 19:54:16 -0800
Diva Canto <[email protected]> <mailto:[email protected]> wrote:
* Within a few days: write a simple [optional]
UserAuthenticationModule along the lines of option a) that does the
following: upon a NewUserConnection, regions will check with the
incoming user's User server that the declared user exists and is
logged into the system.
In a grid a region can be told (via a configuration option) which user
server to check. What about HG regions? How does an HG region know
which user server to ping? Is this information supplied by the
connecting client? If so, what's to prevent a malicious client from
supplying a user server that will always reply favorably?
The HG region sends that information along when the user moves away
from the home UGAIM. The user carries along the collection of URLs of
all of the servers it uses. It's ok if the given User Server @
foobar.com always says yes -- that's not the problem. The problem we
need to detect is the user claiming to be from Intel.com or
OSGrid.org, when, in fact, isn't.
Furthermore, upon AddNewClient (which happens
shortly after), regions will challenge the incoming client with 3 UDP
Ping messages having random seq numbers, to which the incoming client
must respond correctly
How does the client know the correct response?
In fiddling with the client after talking to Teravus, I discovered a
pair of response-reply packets that can be initiated from the server.
They are StartPingCheck / CompletePingCheck. They take a byte as
argument. The server sends StartPingCheck(33), the client responds
with CompletePingCheck(33). Handy.
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