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Re: [tor-bugs] #22934 [Core Tor/Tor]: PADDING cells can't be sent immediately after a VERSIONS cell
#22934: PADDING cells can't be sent immediately after a VERSIONS cell
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Reporter: teor | Owner: nickm
Type: defect | Status: accepted
Priority: Medium | Milestone: Tor: 0.3.1.x-final
Component: Core Tor/Tor | Version: Tor: 0.3.1.1-alpha
Severity: Normal | Resolution:
Keywords: tor-spec, tor-relay | Actual Points:
Parent ID: #18856 | Points: 0.5
Reviewer: | Sponsor:
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Changes (by nickm):
* owner: (none) => nickm
* status: new => accepted
Comment:
So, two issues here: "can this happen on clients that are doing padding"
and "what behavior should we allow"?
I am fairly confident that the answer to the first question is "no". The
function `channelpadding_send_padding_cell_for_callback()` is where the
code sends its cells, and it is always checks whether the channel state is
CHAN_STATE_OPEN. We only set the channel to that state when the OR
connection enters OR_CONN_STATE_OPEN. The same check is performed in
channelpadding_decide_to_pad_channel().
So we won't trigger this today from the channel padding code. Hooray!
So, what _should_ we be doing? It's sure desirable to allow PADDING and
VPADDING after the VERSIONS cell, but we can't actually do that until some
Tors allow it, and we need some means to signal that they will.
I suggest that for 0.3.2, we just fix the spec to note that this doesn't
work, and for 0.3.3 we write a proposal and implement it.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22934#comment:4>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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