Upstream OAuth registration requires usernames of length 3 or more, Matrix Spec allows 1 or more

[thegcat]

We unfortunately have a user with a 2-character username that is currently unable to register with our Matrix server. This seems to be cause by the registration policy https://github.com/matrix-org/matrix-authentication-service/blob/main/policies/register.rego#L17-L19 requiring usernames to be of a length between 3 and 64. The MXID spec however allows the local part of the ID (i.e. the username) to be as short as 1 character, and only requires that the length of the whole MXID not be over 255 characters.

A stop-gap solution for us would be to remove the lower bound and just check that a username is present at all. The better solution would probably be to rework this part of the policy to adhere to the Matrix spec.

Thank you for your help.

[thegcat]

Mmh, it seems I fudged the link to the spec…