81 lines
4.3 KiB
Markdown
81 lines
4.3 KiB
Markdown
# Key verification flow additions: `m.key.verification.ready` and `m.key.verification.done`
|
|
|
|
The current key verification framework is asymmetrical in that the user who
|
|
requests the verification is unable to select the key verification method.
|
|
This makes it harder for more experienced users who wish to guide less
|
|
experienced users through the verification process, especially if they are not
|
|
verifying in-person, but are using a trusted but remote channel of verification
|
|
(such as telephone or video conference).
|
|
|
|
As an example, let us say that Alice is an experienced Matrix user and is
|
|
introducing Bob to the wonders of federated communications. Alice wants to
|
|
verify keys with Bob, so she clicks on the "Verify" button in her client on
|
|
Bob's profile (which sends a `m.key.verification.request` message to Bob).
|
|
Bob's device receives the verification request and prompts Bob to accept the
|
|
verification request. At this point, under the current framework, Bob is
|
|
responsible for choosing the verification method to use. However, with this
|
|
proposal, Bob would be able to just accept the verification request without
|
|
choosing a method, and allow Alice to choose the verification method.
|
|
|
|
In addition, the current key verification framework does not have a method for
|
|
clients to signal to the other side that a key verification was successful.
|
|
Some clients may wish to wait until the other side has either confirmed a
|
|
successful verification or indicated an error before displaying the result of
|
|
the verification, in order to give the two users a consistent view of the
|
|
verification as a whole.
|
|
|
|
## Proposal
|
|
|
|
Two new event types are added to the [key verification
|
|
framework](https://matrix.org/docs/spec/client_server/r0.6.1#key-verification-framework)
|
|
when verifying in to-device messages. The new event
|
|
types are already described in [MSC2241 (Key verification in
|
|
DMs)](https://github.com/matrix-org/matrix-doc/pull/2241). This proposal adds
|
|
them to verifications in to-device messages.
|
|
|
|
The first event type is `m.key.verification.ready`, which must be sent by the
|
|
target of the `m.key.verification.request` message, upon receipt of the
|
|
`m.key.verification.request` event. It has the fields:
|
|
|
|
- `from_device`: the ID of the device that sent the `m.key.verification.ready`
|
|
message
|
|
- `methods`: an array of verification methods that the device supports
|
|
|
|
It also has the usual `transaction_id` or `m.relates_to` fields for key
|
|
verification events, depending on whether it is sent as a to-device event
|
|
or an in-room event.
|
|
|
|
After the `m.key.verification.ready` event is sent, either party can send an
|
|
`m.key.verification.start` event to begin the verification. If both parties
|
|
send an `m.key.verification.start` event, and they both specify the same
|
|
verification method, then the event sent by the user whose user ID is the
|
|
lexicographically smallest is used, and the other `m.key.verification.start` event is ignored.
|
|
In the case of a single user verifying two of their devices, the device ID is
|
|
compared instead. If both parties send an `m.key.verification.start` event,
|
|
but they specify different verification methods, the verification should be
|
|
cancelled with a `code` of `m.unexpected_message`.
|
|
|
|
With to-device messages, previously the sender of the
|
|
`m.key.verification.request` message would send an `m.key.verification.cancel`
|
|
message to the recipient's other devices when it received an
|
|
`m.key.verification.start` event. With this new event, the sender of the
|
|
`m.key.verification.request` message should send an `m.key.verification.cancel`
|
|
message when it receives an `m.key.verification.ready` or
|
|
`m.key.verification.start` message, whichever comes first.
|
|
|
|
The `m.key.verification.ready` event is required for verifications in both DMs
|
|
and in to-device messages to accept verifications requested using an
|
|
`m.key.verification.request` event.
|
|
|
|
The second event type is `m.key.verification.done`, which has no fields other
|
|
than the usual `transaction_id` or `m.relates_to` field. This indicates that
|
|
the device has successfully completed its side of the verification.
|
|
|
|
## Potential issues
|
|
|
|
Clients that follow the Client-Server 0.6.0 spec may not expect an
|
|
`m.key.verification.ready` message in response to `m.key.verification.request`.
|
|
However to our knowledge, no clients implement `m.key.verification.request` in
|
|
this way yet -- to our knowledge, all clients that implement verification
|
|
implement this proposal.
|