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Commit Graph

6 Commits

Author SHA1 Message Date
Simon Tatham
f6f8219a3d Replace PktIn reference count with a 'free queue'.
This is a new idea I've had to make memory-management of PktIn even
easier. The idea is that a PktIn is essentially _always_ an element of
some linked-list queue: if it's not one of the queues by which packets
move through ssh.c, then it's a special 'free queue' which holds
packets that are unowned and due to be freed.

pq_pop() on a PktInQueue automatically relinks the packet to the free
queue, and also triggers an idempotent callback which will empty the
queue and really free all the packets on it. Hence, you can pop a
packet off a real queue, parse it, handle it, and then just assume
it'll get tidied up at some point - the only constraint being that you
have to finish with it before returning to the application's main loop.

The exception is that it's OK to pq_push() the packet back on to some
other PktInQueue, because a side effect of that will be to _remove_ it
from the free queue again. (And if _all_ the incoming packets get that
treatment, then when the free-queue handler eventually runs, it may
find it has nothing to do - which is harmless.)
2018-09-24 14:12:56 +01:00
Simon Tatham
09c3439b5a Move SSH_MSG_UNEXPECTED generation into the BPP.
Now I've got a list macro defining all the packet types we recognise,
I can use it to write a test for 'is this a recognised code?', and use
that in turn to centralise detection of completely unrecognised codes
into the binary packet protocol, where any such messages will be
handled entirely internally and never even be seen by the next level
up. This lets me remove another big pile of boilerplate in ssh.c.
2018-09-24 14:12:56 +01:00
Simon Tatham
26f7a2ac72 Add missing 'static' to BPP vtable definitions.
Vtable objects only need to be globally visible throughout the code if
they're used directly in some interchangeable way, e.g. by passing
them to a constructor like cipher_new that's the same for all
implementations of the vtable, or by directly looking up public data
fields in the vtable itself.

But the BPPs are never used like that: each BPP has its own
constructor function with a different type signature, so the BPP types
are not interchangeable in any way _before_ an instance of one has
been constructed. Hence, their vtable objects don't need external
linkage.
2018-09-23 09:43:43 +01:00
Simon Tatham
93f2df9b83 New system for tracking data-limit-based rekeys.
I've removed the encrypted_len fields from PktIn and PktOut, which
were used to communicate from the BPP to ssh.c how much each packet
contributed to the amount of data encrypted with a given set of cipher
keys. It seems more sensible to have the BPP itself keep that counter
- especially since only one of the three BPPs even needs to count it
at all. So now there's a new DataTransferStats structure which the BPP
updates, and ssh.c only needs to check it for overflow and reset the
limits.
2018-09-19 23:08:28 +01:00
Simon Tatham
d4abff521a Reinstate calls to ssh_free_pktout!
I think ever since commit 679fa90df last month, PuTTY has been
forgetting to free any of its outgoing packet structures after turning
them into their encrypted wire format. And apparently no users of the
development snapshots have noticed - including me!
2018-07-09 20:59:36 +01:00
Simon Tatham
679fa90dfe Move binary packet protocols and censoring out of ssh.c.
sshbpp.h now defines a classoid that encapsulates both directions of
an SSH binary packet protocol - that is, a system for reading a
bufchain of incoming data and turning it into a stream of PktIn, and
another system for taking a PktOut and turning it into data on an
outgoing bufchain.

The state structure in each of those files contains everything that
used to be in the 'rdpkt2_state' structure and its friends, and also
quite a lot of bits and pieces like cipher and MAC states that used to
live in the main Ssh structure.

One minor effect of this layer separation is that I've had to extend
the packet dispatch table by one, because the BPP layer can no longer
directly trigger sending of SSH_MSG_UNIMPLEMENTED for a message too
short to have a type byte. Instead, I extend the PktIn type field to
use an out-of-range value to encode that, and the easiest way to make
that trigger an UNIMPLEMENTED message is to have the dispatch table
contain an entry for it.

(That's a system that may come in useful again - I was also wondering
about inventing a fake type code to indicate network EOF, so that that
could be propagated through the layers and be handled by whichever one
currently knew best how to respond.)

I've also moved the packet-censoring code into its own pair of files,
partly because I was going to want to do that anyway sooner or later,
and mostly because it's called from the BPP code, and the SSH-2
version in particular has to be called from both the main SSH-2 BPP
and the bare unencrypted protocol used for connection sharing. While I
was at it, I took the opportunity to merge the outgoing and incoming
censor functions, so that the parts that were common between them
(e.g. CHANNEL_DATA messages look the same in both directions) didn't
need to be repeated.
2018-06-09 14:41:30 +01:00