This provides a clear error in case the user doesn't have an internet
connection at all, or something is so broken with their DNS or routing that
they can't reach the server. I think this is better than waiting and
retrying (silently) forever.
If the first connection succeeds, but is then lost, subsequent retries occur
without fanfare.
closes#68
This renames all the existing API methods, to use a consistent
"d=get_XYZ()" (for Deferred mode) or "dg.wormhole_got_XYZ()" (for Delegated
mode). It updates cmd_send/cmd_receive/cmd_ssh to use the new API.
Since we now have get_welcome(), apps handle the Welcome message with a
Deferred callback instead of registering a "welcome handler". This lets us
make sure we've finished printing any server message-of-the-day or "you
should update your client" message to stdout before using stdio to ask for
the wormhole code. (Previously, the code-input prompt was overwritten by the
server message, and it was ugly). refs #145. This approach adds an extra
roundtrip to the receiver, but we can fix that (see #145 for details).
Because of that change, the server-is-being-slow message is printed at a
slightly different time, so those tests needed some extra work to exercise it
properly.
Previously, w.when_verified() was documented to fire only after a valid
encrypted message was received, but in fact it fired as soon as the shared
key was derived (before any encrypted messages are seen, so no actual
"verification" could occur yet).
This fixes that, and also adds a new w.when_key() API call which fires at the
earlier point. Having something which fires early is useful for the CLI
commands that want to print a pacifier message when the peer is responding
slowly. In particular it helps detect the case where 'wormhole send' has quit
early (after depositing the PAKE message on the server, but before the
receiver has started). In this case, the receiver will compute the shared
key, but then wait forever hoping for a VERSION that will never come. By
starting a timer when w.when_key() fires, and cancelling it when
w.when_verified() fires, we have a good place to tell the user that something
is taking longer than it should have.
This shifts responsibility for notifying Boss.got_verifier, out of Key and
into Receive, since Receive is what notices the first valid encrypted
message. It also shifts the Boss's ordering expectations: it now receives
B.happy() before B.got_verifier(), and consequently got_verifier ought to
arrive in the S2_happy state rather than S1_lonely.
* finally wire up "application versions"
* remove when_verifier (which used to fire after key establishment, but
before the VERSION message was received or verified)
* fire when_verified and when_version at the same time (after VERSION is
verified), but with different args
(one displayed message per received welcome["motd"])
There's not much value in prohibiting the server from sending multiple
MOTD messages, and it would prevent us from using it to display a "your
client is using an old API, please upgrade" message after having already
sent a regular "please donate" MOTD message. (We could send a second
welcome message with ["error"] to kill the client, but ["motd"] is the
most convenient way to deliver a non-fatal warning).
The reasoning is that this string is only ever likely to refer to the
version of the primary/initial client (the CLI application, written in
Python, that you get with "pip install magic-wormhole"). When there are
other implementations, with unrelated versions, they should obviously
not pay attention to a warning about the other implementation being out
of date.
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 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.
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
