[OTR-dev] Flaw in OTR Protocol (with workaround!)

[Evan Schoenberg]

This just happened, thought it was clearly illustrate both the  
problem under discussion and a related issue:

<I'm in an OTR session with OtherUser, both of us are on Manual>
2:45:31 PM OtherUser: brb
OtherUser disconnected (2:45:32 PM)
OtherUser connected (2:49:00 PM)
2:49:45 PM OtherUser: The following message received from OtherUser  
was not encrypted: [and we're back
2:49:52 PM tekjew: and this.
2:49:52 PM OtherUser: ?OTR Error: You sent encrypted data to  
OtherUser, who wasn't expecting it.
2:49:53 PM tekjew: is
2:49:53 PM OtherUser: ?OTR Error: You sent encrypted data to  
OtherUser, who wasn't expecting it.
2:49:54 PM tekjew: what
2:49:54 PM OtherUser: ?OTR Error: You sent encrypted data to  
OtherUser, who wasn't expecting it.
2:50:00 PM tekjew: I mean, Ian.
2:50:00 PM OtherUser: ?OTR Error: You sent encrypted data to  
OtherUser, who wasn't expecting it.
Ended encrypted OTR chat. (2:50:02 PM)
2:50:03 PM OtherUser: ?OTR Error: You sent encrypted data to  
OtherUser, who wasn't expecting it.
2:50:07 PM tekjew: hehe
2:50:08 PM tekjew: perfect!
2:50:12 PM tekjew: thanks for letting me demo that :)

So OtherUser quit and then reloaded.  He sent me an unencrypted  
message... fine so far, that's to be expected.  But when I sent "and  
this." I would have wanted the Magic Opportunistic (Private/Broken)  
mode to take effect and renegotiate a session.

Note the other interesting oddity, though I can see why it would  
happen -- When I did click "End encrypted session" locally, the  
encrypted 'closed' packet was sent to OtherUser, and then I was told  
that I sent encrypted data.  Most users would be very confused by  
this particular bit of information, since as far as they know they  
didn't send any data to the other user.

-Evan


On Aug 4, 2005, at 2:41 PM, Ian Goldberg wrote:

> On Thu, Aug 04, 2005 at 02:35:35PM -0400, Ian Goldberg wrote:
>
>> On Thu, Aug 04, 2005 at 01:36:01PM -0400, Evan Schoenberg wrote:
>>
>>> Currently:
>>> OTR session with Alice
>>> I exit my client (without selecting End Private Conversation, which
>>> is what happens with most users)
>>> I reconnect
>>> Alice says something.  Her client is currently in the Private state,
>>> with the previous secure session.
>>> I get an encrypted message I can't read (sent using the encryption
>>> from the old secure session).
>>>
>>
>> Note that this causes OTR to automatically restart if you're in
>> Opportunistic mode.
>>
>
> And I forgot to say: which will also cause Alice's message to get
> resent.
>
> That being said, it's arguably more correct for gaim to disconnect its
> contexts before exiting, and the patch is totally trivial, so I
> committed it to CVS.  ;-)
>
>    - Ian
> _______________________________________________
> OTR-dev mailing list
> OTR-dev at lists.cypherpunks.ca
> http://lists.cypherpunks.ca/mailman/listinfo/otr-dev
>
>

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