Federation API for canonicalising MXIDs

[matrixbot]

Documentation: https://docs.google.com/document/d/1B7q_3ruJzeQTg-uJHe1UScxbVLzgm451c25OjpYcojI/edit#
Author: @ara4n

I'm seeing more and more disasters with people failing to identify users correctly due to case sensitive IDs. For instance Amandine's business cards say @​amandine:matrix.org whereas she's registered as @​Amandine:matrix.org.

Splitting this out from matrix-org/synapse#1220

(Imported from https://matrix.org/jira/browse/SPEC-289)

(Reported by @ara4n)

[matrixbot]

Jira watchers: @NegativeMjark @ara4n @richvdh

[matrixbot]

Links exported from Jira:

is blocked by SPEC-62
relates to SPEC-1
relates to https://github.com/matrix-org/matrix-doc/issues/494
relates to SPEC-390
relates to matrix-org/synapse#1220
vector-web issue

[matrixbot]

If we want any level of flexibility for this lookup we need the HS to implement mapping from printed user-id to actual matrix ID.

Unless we restrict the space of IDs to fit into ASCII then rigorously defining a case insensitive match is slightly painful.

-- @NegativeMjark

[matrixbot]

Blocked by specifying a lookup API.

-- @NegativeMjark

[matrixbot]

The current plan of action on this (as discussed IRL yesterday evening is):

• Store IDs case-sensitively in the DB
• Compare them case-sensitively in the code & protocol
• Canonicalise them either at the origin client or origin HS by querying a lookup API on the destination HS (as per SPEC-62). This adds a roundtrip, but it may be suppressable by combining with some other roundtrip.

Open questions are:

• Do you do the canonicalisation lookup from the origin client (yet another random thing to expect clients to remember to do, which they will never remember to)
• Do you do the canonicalisation lookup from the origin HS?
• Do you use a user alias->id (assuming user aliases were separated from underlying IDs) lookup to also perform the canonicalisation?

-- @ara4n

[matrixbot]

this looks to have been mistakenly closed; the problem is still glaringly open.

-- @ara4n

[matrixbot]

A solution to this (at least for invites) is proposed at https://docs.google.com/document/d/1B7q_3ruJzeQTg-uJHe1UScxbVLzgm451c25OjpYcojI.

-- @richvdh

[cavebeat]

i also have this problem

user registered @foo and i want to rename to lower-case
deactivation of @foo and new registering @foo is not possible, as @foo is already taken.
it is suggested-and-not-suggested to do surgery on the DB... there is no other way for this.

if user registration is case insensitive, create from now on just lower case users... !

[richvdh]

previously, this was MSC586.