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MSC2181: Add an Error Code for Signaling a Deactivated User #2181

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Jul 31, 2019
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MSC2181: Add an Error Code for Signaling a Deactivated User #2181

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Add proposal regarding user deactivated err codes
anoadragon453 Jul 16, 2019
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anoadragon453 Jul 16, 2019
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anoadragon453 Jul 16, 2019
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Update proposals/2181-user-deactivated-errcode.md
anoadragon453 Jul 19, 2019
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Specify /login should have M_USER_DEACTIVATED
anoadragon453 Jul 19, 2019
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Merge branch 'anoa/user_deactivated_msc' of github.com:matrix-org/mat…
anoadragon453 Jul 19, 2019
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kill the hashes
anoadragon453 Jul 22, 2019
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anoadragon453 Jul 26, 2019
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anoadragon453 Jul 26, 2019
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50 changes: 50 additions & 0 deletions proposals/2181-user-deactivated-errcode.md
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# Add an Error Code for Signaling a Deactivated User

Currently, when a user attempts to log in, they will receive an `M_FORBIDDEN`
error code if their password is incorrect. However, if the user's account is
deactivated, they will also receive an `M_FORBIDDEN`, leaving clients in a
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Question: What do homeservers do if the user is deactivated and somebody tries to log in with an incorrect password? Is the homeserver expected to retain the password forever? If the password is not retained, should all attempts to login as a deactivated user return the deactivated error (which may have some privacy implications?).

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It should still return M_USER_DEACTIVATED. Password hashes are wiped (at least in Synapse) upon user deactivation.

which may have some privacy implications?

Privacy implications are here whether password hashes are retained or not, no?

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The problem with shifting it so that you need to login to see if you're deactivated, is that we already have tons of deactivated users whose password hashes have been cleared.

Also worth noting reddit's APIs allow you to tell if any user has been shadowbanned, something that ideally even the user wouldn't know, and that doesn't seem to have caused their service any harm. https://nullprogram.com/am-i-shadowbanned/

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... also by nature of being deactivated you shouldn't be allowed back in. Why would we let people get that far into the process without telling them to go away? I think the proposed approach is fine

state where they are unable to inform the user that the reason they cannot
log in is that their account has been deactivated. This leads to confusion
and password resetting which ultimately results in frustration.

## Proposal

This proposal asks to create a new error code, `M_USER_DEACTIVATED`, that may
be returned whenever an action is attempted that requires an activited user,
but the authenticating user is deactivated. The HTTP code to return alongside
is `403`.

An example of this could be returning `M_USER_DEACTIVATED` on `/login`, when
an identifier of a deactivated user is sent to the homeserver. Whether the
password has to be correct depends on whether the Homeserver implementation
removes login information on deactivation. This is an implementation detail.

It should be noted that this proposal is not requiring implementations to
return `M_USER_DEACTIVATED` on any endpoints when a request from a
deactivated user appears. Instead it is simply defining the new error code,
recommends that it should be used in situations as described above, and that
the client should understand the meaning of it when it is received.

## Tradeoffs
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The alternative is to continue returning an `M_FORBIDDEN`, but send back a
different error message. This is undesirable as clients are supposed to treat
the message as an opaque string, and should not be performing any
pattern-matching on it.

## Potential issues

None

## Security considerations
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While the existence of a user was already public knowledge (one can check if
the User ID is available through
[/_matrix/client/r0/register/available](https://matrix.org/docs/spec/client_server/r0.5.0#get-matrix-client-r0-register-available),
this proposal would allow any user to be able to detect if a registered
account has been deactivated, depending on the homeserver's implementation.

## Conclusion

Adding `M_USER_DEACTIVATED` would better inform clients about the state of a
user's account, and lead to less confusion when they cannot log in.