dendrite/roomserver/auth/auth.go

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// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package auth
import (
"encoding/json"
"github.com/matrix-org/gomatrixserverlib"
)
// TODO: This logic should live in gomatrixserverlib
// IsServerAllowed returns true if the server is allowed to see events in the room
// at this particular state. This function implements https://matrix.org/docs/spec/client_server/r0.6.0#id87
func IsServerAllowed(
serverName gomatrixserverlib.ServerName,
serverCurrentlyInRoom bool,
authEvents []gomatrixserverlib.Event,
) bool {
historyVisibility := HistoryVisibilityForRoom(authEvents)
// 1. If the history_visibility was set to world_readable, allow.
if historyVisibility == "world_readable" {
return true
}
// 2. If the user's membership was join, allow.
joinedUserExists := IsAnyUserOnServerWithMembership(serverName, authEvents, gomatrixserverlib.Join)
if joinedUserExists {
return true
}
// 3. If history_visibility was set to shared, and the user joined the room at any point after the event was sent, allow.
if historyVisibility == "shared" && serverCurrentlyInRoom {
return true
}
// 4. If the user's membership was invite, and the history_visibility was set to invited, allow.
invitedUserExists := IsAnyUserOnServerWithMembership(serverName, authEvents, gomatrixserverlib.Invite)
if invitedUserExists && historyVisibility == "invited" {
return true
}
// 5. Otherwise, deny.
return false
}
func HistoryVisibilityForRoom(authEvents []gomatrixserverlib.Event) string {
// https://matrix.org/docs/spec/client_server/r0.6.0#id87
// By default if no history_visibility is set, or if the value is not understood, the visibility is assumed to be shared.
visibility := "shared"
knownStates := []string{"invited", "joined", "shared", "world_readable"}
for _, ev := range authEvents {
if ev.Type() != gomatrixserverlib.MRoomHistoryVisibility {
continue
}
// TODO: This should be HistoryVisibilityContent to match things like 'MemberContent'. Do this when moving to GMSL
content := struct {
HistoryVisibility string `json:"history_visibility"`
}{}
if err := json.Unmarshal(ev.Content(), &content); err != nil {
break // value is not understood
}
for _, s := range knownStates {
if s == content.HistoryVisibility {
visibility = s
break
}
}
}
return visibility
}
func IsAnyUserOnServerWithMembership(serverName gomatrixserverlib.ServerName, authEvents []gomatrixserverlib.Event, wantMembership string) bool {
for _, ev := range authEvents {
membership, err := ev.Membership()
if err != nil || membership != wantMembership {
continue
}
stateKey := ev.StateKey()
if stateKey == nil {
continue
}
_, domain, err := gomatrixserverlib.SplitID('@', *stateKey)
if err != nil {
continue
}
if domain == serverName {
return true
}
}
return false
}