This gives us room in the future to put other keys there, like one which
says we want to use Noise for the phase-message encryption instead of
our current HKDF scheme.
This will be useful for the upcoming "persistent wormhole" mode. A
client might send an allocation request, crash/terminate before
receiving a response, then restart, then re-send the request. If the
server sees a request with the same request_id a previous request, it
can return the same nameplate.
We'll need code changes on both sides to support this (nothing sends or
checks request_id yet), but this lands the schema change early to reduce
future disruption.
This will allow a future peer to figure out what transit modes we can
and cannot do, and thus avoid spinning up expensive modes that we won't
be able to use (e.g. WebRTC).
This enhances the ACK that wormhole-receive returns when it finishes
receiving all the data to be a dictionary. The dict includes the SHA256
hash of everything it received, and the sender checks this for a match
before declaring the transfer to be a success. This guards against data
being shuffled somehow during transit.
This better reflects the purpose of the message. Key confirmation is a
side-effect.
This patch only changes the "phase:" name and the key-derivation string.
A subsequent patch will modify the function and variable names to match.
The file-send protocol now sends a "hints-v1" key in the "transit"
message, which contains a list of JSON data structures that describe the
connection hints (a mixture of direct, tor, and relay hints, for now).
Previously the direct/tor and relay hints were sent in different keys,
and all were sent as strings like "tcp:hostname:1234" which had to be
parsed by the recipient.
The new structures include a version string, to make it easier to add
new types in the future. Transit logs+ignores hints it cannot
understand.
In the future, both sides should expect to receive "transit" messages at
any time, and they will add to the list of hints that they should try.
For now, each side only sends a single transit message, before they send
the offer (sender) or answer (receiver).
This moves us slowly towards a file-transfer protocol that exchanges
multiple messages, with a single offer (sender->receiver) and
answer (receiver->sender), and one or more connection hint messages (in
either direction) that appear gradually over time as connection
providers come online.
At present the protocol still expects the whole hint list to be present
in the offer/answer message.
This should enable forwards-compatibility with clients which send extra
data, like a pre-PAKE "auxdata" message that hints we should spin up a
tor client (because they can connect to it) while we're waiting for the
user to type in the wormhole code.
Previously the encryption key used for "phase messages" (anything sent
from one side to the other, protected by the shared PAKE-generated
session key) was derived just from the session key and the phase name.
The two sides would use the same key for their first message (but with
random, thus different, nonces).
This uses the sending side's string (a random 5-byte/10-character hex
string) in the derivation process too, so the two sides use different
keys. This gives us an easy way to reject reflected messages. We already
ignore messages that claim to use a "side" which matches our own (to
ignore server echoes of our own outbound messages). With this change, an
attacker (or the server) can't swap in the payload of an outbound
message, change the "side" to make it look like a peer message, and then
let us decrypt it correctly.
It also changes the derivation function to combine the phase and side
values safely. This didn't matter much when we only had one
externally-provided string, but with two, there's an opportunity for
format confusion if they were combined with a simple delimiter. Now we
hash both values before concatenating them.
This breaks interoperability with clients from before this change. They
will always get WrongPasswordErrors.
* add "released" ack-response for "release" command, to sync w.close()
* move websocket URL to root
* relayurl= should now be a "ws://" URL
* many tests pass (except for test_twisted, which will be removed, and
test_scripts)
* still moving integration tests from test_twisted to
test_wormhole.Wormholes
This made sense for ServerSentEvent channels (which has no purpose once
the channel was gone), but not so much for websockets. And it prevented
testing duplicate-close.
Pass in a handle and a pair of functions, rather than an object with two
well-known methods. This should make it easier to subscribe to multiple
channels in the future.
but only if the client is modern enough to include "id" in the message,
which lets us avoid sending acks to an 0.7.5 client (which would cause
them to abort, they don't like unrecognized server messages).
The acks let the client learn the server_rx time of messages that
terminate on the server, like "allocate" and "claim".
