[OTR-users] QQ is blocking OTR

[Eliah Kagan]

On Sat, Oct 18, 2008 at 4:35 PM, Ananda Samaddar said:
> A user has e-mailed me off list to confirm he can reproduce my results
> w.r.t the strings ?, ?O, ?OT and ?OTR.  This was using Adium 1.3.2 and
> Pidgin on Linux with OTR 3.1.0 on either end.  As I've stated before
> there are issue with Pidgin + QQ on Windows so it would be helpful if
> someone with an up to date Pidgin + OTR on Linux could contact me to
> see if the results are replicated on Linux to Linux Pidgin clients.
> This could hopefully rule out a buggy QQ implementation in libpurple.

It appears that, in spite of a reproducible problem sending ?OTR
between libpurple-based clients running OTR, Tencent QQ is probably
not deliberately blocking OTR after all.

I am the user who initially contacted Ananda to confirm her findings.
In all my tests described herein, separate QQ accounts were used on
separate computers at different physical locations connecting to the
Internet with different IP addresses. I was using Pidgin 2.5.0 on
Xubuntu Linux 8.04. A friend of mine (hereafter to be referred to as
"my associate") was using Adium X 1.3.2 on Mac OS X 10.5.5 (Intel). My
OTR plugin was enabled, but set not to automatically initiate OTR
conversations. Neither of us could send ?OTR to the other. When we
then tried to actually start an OTR conversation (with either of us
starting it--we tried it both ways), it would fail silently on my end
and my associate got the error: "Could not send the last message
because it was too large."

That is what I reported to Ananda. Since then, Ananda and I have
verified that OTR does not work over QQ (and fails silently) between
two Linux Pidgin 2.5.0 clients.

Today my associate and I tried both using Pidgin 2.5.0 on Xubuntu
Linux 8.0.4. With the OTR plugin turned off, we were able to both send
?OTR to one another successfully. With the plugin turned on but set
not to automatically initiate OTR conversations, neither of us was
able to do so. We then found that whoever had OTR turned off
completely was able to receive "?OTR" as an IM.

We tested it with QQ for Windows, using QQ2005 v05.0.200.020 (English)
on each end. Mine ran on Windows FLP Version 2006 SP3. My associate
ran it on Windows XP Professional Version 2002 SP3. We were able to
send ?OTR in both directions. We tried it with QQ2005 on my end and
Adium X 1.3.2 on my associate's end, and I was able to receive ?OTR
(i.e. my associate was able to send it), but my associate was not able
to receive it (i.e. I was not able to send it). This further bolstered
the hypothesis that the failure to send ?OTR is actually due to OTR
not displaying incoming messages that start with that string.

Finally, my associate and I tested that by sending ?OTR via AOL
Instant Messenger (the service). I used Carrier 2.5.0 (a close fork of
Pidgin) on Windows XP Professional Version 2002 SP3, and my associate
used the original Adium setup. Neither was able to send ?OTR to the
other when OTR was enabled but not being used (i.e. with an
unencrypted connection). In light of this, it is unlikely that the
failure to send ?OTR via QQ is related to QQ specifically.

Therefore, I believe the explanation that remains is that the recent
failure of QQ to work with OTR is due to a decrease by Tencent in the
maximum message size you can send over QQ. This is consistent with the
Adium error messages, and is an issue that could probably be addressed
without too much difficulty.

-Eliah