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@ -55,11 +55,10 @@ not a member of at least one of the rooms, the homeserver should return an error
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response with HTTP status code of 403 and an `errcode` of `M_FORBIDDEN`.
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It is possible for a homeserver receiving a `/make_join` / `/send_join` request
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to not know if the user is in a particular room (due to not participating in any
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of the necessary rooms). In this case the homeserver should reject the join,
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the requesting server may wish to attempt to join via another homeserver. If no
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servers are in an allowed room its membership cannot be checked (and this is a
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misconfiguration).
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to not know if the user is in any of the allowed room (due to not participating
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in them). In this case the homeserver should reject the join, the requesting
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server may wish to attempt to join via another homeserver. If no servers are in
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an allowed room its membership cannot be checked (and this is a misconfiguration).
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From the perspective of the [auth rules](https://spec.matrix.org/unstable/rooms/v1/#authorization-rules),
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the `restricted` join rule has the same behavior as `public`, with the additional
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@ -78,8 +77,6 @@ event in the room.)
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Note that the homeservers whose users can issue invites are trusted to confirm
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that the `allow` rules were properly checked (since this cannot easily be
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enforced over federation by event authorisation).<sup id="a3">[3](#f3)</sup>
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(The rationale for trusting these homeservers is that they could easily
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side-step the restriction by issuing an invite first.)
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## Summary of the behaviour of join rules
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@ -99,15 +96,11 @@ between `public`, `invite`, and `restricted`.
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## Security considerations
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Although increased trust to enforce the join rules during `/join` / `/make_join`
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/ `/send_join` is placed in the homeservers whose users can issue invites, this
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is considered only a miniscule change in room security.
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This MSC limits the homeservers who can issue join events (via calls to `/join`,
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`/make_join`, and `/send_join`) and trusts those servers to enforce the additional
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allow rules. Although other homeservers may not be able to verify that a join
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event was issued in good faith, there is no benefit for a homeserver to do this
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since they could have issued an invite anyway.
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Increased trust to enforce the join rules during calls to `/join`, `/make_join`,
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and `/send_join` is placed in the homeservers whose users can issue invites.
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Although it is possible for those homeservers to issue a join event in bad faith,
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there is no real-world benefit to doing this as those homeservers could easily
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side-side the restriction by issuing an invite first anyway.
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## Unstable prefix
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