Ethereal-dev: Re: [Ethereal-dev] [DCE RPC] Incorrect dissection with CVS version 2004060315332

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From: Jean-Baptiste Marchand <Jean-Baptiste.Marchand@xxxxxx>
Date: Sun, 6 Jun 2004 15:38:27 +0200
Hello,

* Jean-Baptiste Marchand <Jean-Baptiste.Marchand@xxxxxx> [04/06/04 - 11:29]:

> it seems that there is a dissection problem with a current version of
> the DCE RPC dissector.
> 
> The first attached capture (epm1_anon.cap) contains 6 frames, 2 two TCP segments
> (SYN-ACK, ACK) and 4 DCE RPC PDUs. The last two DCE RPC PDUs are not
> properly dissected as EPM operations.
> 
> The second attached capture (epm2_anon.cap) is identical to the first one,
> except that the first TCP segment has been removed. The last two DCE RPC
> PDUs are properly dissected as EPM operations.
> 
> The only difference is that in the first case, we see a SYN-ACK TCP
> segment and thus, this might be something related to TCP conversations?
> 
> PS: attached traces have been anonymized with ipsumdump
> (http://www.icir.org/kohler/ipsumdump/), thus IP addresses are different
> in the traces but they were both generated from the same original trace.

I'm a bit confused because I've tried to open these two captures on a
recent build of ethereal on MacOS X (CVS tree updated this morning) and
the two are dissected properly.

On the other hand, I've just updated my CVS tree on my FreeBSD laptop
and I still have the same problem I described on ethereal-dev@.

It does not seem to be related to a difference in my preferences, as
I've tried with the default ethereal preference settings (I rename the
~/.ethereal directory to ~/.ethereal_old).

Follow tethereal outputs for me (checksum is incorrect because IP
addresses have been modified because of anonymization with ipsumdump):

jbm@garbarek ~> tethereal -r epm1_anon.cap
  1   0.000000 194.115.240.203 -> 194.115.240.48 TCP loc-srv > 1053
[SYN, ACK] Seq=0 Ack=1 Win=17520 [CHECKSUM INCORRECT] Len=0 MSS=1460
  2   0.001235 194.115.240.48 -> 194.115.240.203 TCP 1053 > loc-srv
[ACK] Seq=1 Ack=1 Win=17520 [CHECKSUM INCORRECT] Len=0
  3   0.006250 194.115.240.48 -> 194.115.240.203 DCERPC Bind: call_id: 1
UUID: EPM
  4   0.016912 194.115.240.203 -> 194.115.240.48 DCERPC Bind_ack:
call_id: 1 accept max_xmit: 5840 max_recv: 5840
  5   0.018674 194.115.240.48 -> 194.115.240.203 DCERPC Request:
call_id: 1 opnum: 3 ctx_id: 0
  6   0.021197 194.115.240.203 -> 194.115.240.48 DCERPC Response:
call_id: 1 ctx_id: 0

jbm@garbarek ~> tethereal -r epm2_anon.cap
  1   0.000000 205.61.107.240 -> 205.61.107.6 TCP 1053 > loc-srv [ACK]
Seq=0 Ack=0 Win=17520 [CHECKSUM INCORRECT] Len=0
  2   0.005015 205.61.107.240 -> 205.61.107.6 DCERPC Bind: call_id: 1
UUID: EPM
  3   0.015677 205.61.107.6 -> 205.61.107.240 DCERPC Bind_ack: call_id:
1 accept max_xmit: 5840 max_recv: 5840
  4   0.017439 205.61.107.240 -> 205.61.107.6 EPM Map request
  5   0.019962 205.61.107.6 -> 205.61.107.240 EPM Map response


As you can, frames 5 and 6 are not properly dissected in the first trace
whereas in the second one, frames 4 and 5 (the first frame is remove in
the second trace), there are properly recognized as EPM operations...

Any ideas?

Thanks in advance,

Jean-Baptiste Marchand
-- 
Jean-Baptiste.Marchand@xxxxxx
HSC - http://www.hsc.fr/