encryption: add ability to control rotation settings

Signed-off-by: Sumner Evans <sumner@beeper.com>

config/upgrade.go

@@ -47,6 +47,9 @@ func DoUpgrade(helper *up.Helper) {
 	helper.Copy(up.Bool, "bridge", "encryption", "key_sharing", "allow")
 	helper.Copy(up.Bool, "bridge", "encryption", "key_sharing", "require_cross_signing")
 	helper.Copy(up.Bool, "bridge", "encryption", "key_sharing", "require_verification")
+	helper.Copy(up.Bool, "bridge", "encryption", "rotation", "enable_custom")
+	helper.Copy(up.Int, "bridge", "encryption", "rotation", "milliseconds")
+	helper.Copy(up.Int, "bridge", "encryption", "rotation", "messages")
 
 	helper.Copy(up.Str, "bridge", "provisioning", "prefix")
 	if secret, ok := helper.Get(up.Str, "bridge", "provisioning", "shared_secret"); !ok || secret == "generate" {

example-config.yaml

@@ -143,6 +143,23 @@ bridge:
             # Require devices to be verified by the bridge?
             # Verification by the bridge is not yet implemented.
             require_verification: true
+        # Options for Megolm room key rotation. These options allow you to
+        # configure the m.room.encryption event content. See:
+        # https://spec.matrix.org/v1.3/client-server-api/#mroomencryption for
+        # more information about that event.
+        rotation:
+            # Enable custom Megolm room key rotation settings. Note that these
+            # settings will only apply to rooms created after this option is
+            # set.
+            enable_custom: false
+            # The maximum number of milliseconds a session should be used
+            # before changing it. The Matrix spec recommends 604800000 (a week)
+            # as the default.
+            milliseconds: 604800000
+            # The maximum number of messages that should be sent with a given a
+            # session before changing it. The Matrix spec recommends 100 as the
+            # default.
+            messages: 100
 
     # Settings for provisioning API
     provisioning:

go.mod

@@ -11,7 +11,7 @@ require (
 	github.com/skip2/go-qrcode v0.0.0-20200617195104-da1b6568686e
 	github.com/yuin/goldmark v1.4.12
 	maunium.net/go/maulogger/v2 v2.3.2
-	maunium.net/go/mautrix v0.11.1-0.20220531091243-d75452b1e36b
+	maunium.net/go/mautrix v0.11.1-0.20220621174128-b64dc2427d45
 )
 
 require (

go.sum

@@ -58,5 +58,5 @@ maunium.net/go/mauflag v1.0.0 h1:YiaRc0tEI3toYtJMRIfjP+jklH45uDHtT80nUamyD4M=
 maunium.net/go/mauflag v1.0.0/go.mod h1:nLivPOpTpHnpzEh8jEdSL9UqO9+/KBJFmNRlwKfkPeA=
 maunium.net/go/maulogger/v2 v2.3.2 h1:1XmIYmMd3PoQfp9J+PaHhpt80zpfmMqaShzUTC7FwY0=
 maunium.net/go/maulogger/v2 v2.3.2/go.mod h1:TYWy7wKwz/tIXTpsx8G3mZseIRiC5DoMxSZazOHy68A=
-maunium.net/go/mautrix v0.11.1-0.20220531091243-d75452b1e36b h1:Ta+etLMqLdckOHtR087/2Y6uYTlz5EXfH8cIBDsHAys=
+maunium.net/go/mautrix v0.11.1-0.20220621174128-b64dc2427d45 h1:3ld9X4COzaeGrfAAUYD5f4is0siPGzodTFtX/+o8Q50=
-maunium.net/go/mautrix v0.11.1-0.20220531091243-d75452b1e36b/go.mod h1:CiKpMhAx5QZFHK03jpWb0iKI3sGU8x6+LfsOjDrcO8I=
+maunium.net/go/mautrix v0.11.1-0.20220621174128-b64dc2427d45/go.mod h1:CiKpMhAx5QZFHK03jpWb0iKI3sGU8x6+LfsOjDrcO8I=

portal.go

@@ -278,6 +278,15 @@ func (portal *Portal) UpdateBridgeInfo() {
 	}
 }
 
+func (portal *Portal) GetEncryptionEventContent() (evt *event.EncryptionEventContent) {
+	evt = &event.EncryptionEventContent{Algorithm: id.AlgorithmMegolmV1}
+	if rot := portal.bridge.Config.Bridge.Encryption.Rotation; rot.EnableCustom {
+		evt.RotationPeriodMillis = rot.Milliseconds
+		evt.RotationPeriodMessages = rot.Messages
+	}
+	return
+}
+
 func (portal *Portal) CreateMatrixRoom(user *User, channel *discordgo.Channel) error {
 	portal.roomCreateLock.Lock()
 	defer portal.roomCreateLock.Unlock()
@@ -356,7 +365,7 @@ func (portal *Portal) CreateMatrixRoom(user *User, channel *discordgo.Channel) e
 		initialState = append(initialState, &event.Event{
 			Type: event.StateEncryption,
 			Content: event.Content{
-				Parsed: event.EncryptionEventContent{Algorithm: id.AlgorithmMegolmV1},
+				Parsed: portal.GetEncryptionEventContent(),
 			},
 		})
 		portal.Encrypted = true