mirror of
https://github.com/tahoe-lafs/tahoe-lafs.git
synced 2024-12-21 05:53:12 +00:00
72 lines
2.6 KiB
ReStructuredText
72 lines
2.6 KiB
ReStructuredText
**********************
|
|
Magic Wormhole Invites
|
|
**********************
|
|
|
|
Magic Wormhole
|
|
==============
|
|
|
|
`magic wormhole`_ is a server and a client which together use Password
|
|
Authenticated Key Exchange (PAKE) to use a short code to establish a
|
|
secure channel between two computers. These codes are one-time use and
|
|
an attacker gets at most one "guess", thus allowing low-entropy codes
|
|
to be used.
|
|
|
|
.. _magic wormhole: https://github.com/warner/magic-wormhole#design
|
|
|
|
|
|
Invites and Joins
|
|
=================
|
|
|
|
Inside Tahoe-LAFS we are using a channel created using `magic
|
|
wormhole`_ to exchange configuration and the secret fURL of the
|
|
Introducer with new clients.
|
|
|
|
This is a two-part process. Alice runs a grid and wishes to have her
|
|
friend Bob use it as a client. She runs ``tahoe invite bob`` which
|
|
will print out a short "wormhole code" like ``2-unicorn-quiver``. You
|
|
may also include some options for total, happy and needed shares if
|
|
you like.
|
|
|
|
Alice then transmits this one-time secret code to Bob. Alice must keep
|
|
her command running until Bob has done his step as it is waiting until
|
|
a secure channel is established before sending the data.
|
|
|
|
Bob then runs ``tahoe create-client --join <secret code>`` with any
|
|
other options he likes. This will "use up" the code establishing a
|
|
secure session with Alice's computer. If an attacker tries to guess
|
|
the code, they get only once chance to do so (and then Bob's side will
|
|
fail). Once Bob's computer has connected to Alice's computer, the two
|
|
computers performs the protocol described below, resulting in some
|
|
JSON with the Introducer fURL, nickname and any other options being
|
|
sent to Bob's computer. The ``tahoe create-client`` command then uses
|
|
these options to set up Bob's client.
|
|
|
|
|
|
|
|
Tahoe-LAFS Secret Exchange
|
|
==========================
|
|
|
|
The protocol that the Alice (the one doing the invite) and Bob (the
|
|
one being invited) sides perform once a magic wormhole secure channel
|
|
has been established goes as follows:
|
|
|
|
Alice and Bob both immediately send an "abilities" message as
|
|
JSON. For Alice this is ``{"abilities": {"server-v1": {}}}``. For Bob,
|
|
this is ``{"abilities": {"client-v1": {}}}``.
|
|
|
|
After receiving the message from the other side and confirming the
|
|
expected protocol, Alice transmits the configuration JSON::
|
|
|
|
{
|
|
"needed": 3,
|
|
"total": 10,
|
|
"happy": 7,
|
|
"nickname": "bob",
|
|
"introducer": "pb://xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx@example.com:41505/yyyyyyyyyyyyyyyyyyyyyyy"
|
|
}
|
|
|
|
Both sides then disconnect.
|
|
|
|
As you can see, there is room for future revisions of the protocol but
|
|
as of yet none have been sketched out.
|