[jdev] Checking the from of iq replies

[Lars Noschinski]

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Hi everyone,

I am working on implementing better checks against spoofed iq-replies in
Smack. I want to avoid the pitfalls other projects fell into, so I
looked at Pidgin, Psi and PyXMPP to find the most sensible behaviour.
I'm detailing my findings here, maybe they are helpful for somebody.

The following table shows the IQ-replies accepted by P(i)dgin[1], P(s)i
(Task::iqVerify) and P(y)XMPP.

    From\to| e   | l   | bl  | dl+s | o
    -------+-----+-----+-----+------+-----
    e      | isy |     |     | s    |
    l      | isy | isy | s   | s    |
    bl     | isy | s   | isy | s    |
    dl+s   | isy | s   | s   | isy  |
    o      |     |     |     |      | isy

Legend
    e: empty
    l: local (client) jid
    bl: bare local jid
    dl: domainpart of local jid
    s: server jid
    o: other jid

Pidgin and PyXMPP behave very similar, while Psi is more lenient in the
answers it allows. Unfortunately, the repository history sheds no light
on whether this lenient behaviour was introduced to cope with real
problems.

Best regards,
   Lars


[1] <https://hg.pidgin.im/pidgin/main/rev/b8e2a5fbffd3>
[2]
<https://github.com/psi-im/iris/blob/master/src/xmpp/xmpp-im/xmpp_task.cpp>,
Task::iqVerify
[3]
<https://github.com/Jajcus/pyxmpp/blob/master/pyxmpp/stanzaprocessor.py>,
process_iq
[4] http://xmpp.org/rfcs/rfc6120.html#stanzas-attributes-from

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