From 6728ac523cec8318ca030b64ed0df4dc2cdbebea Mon Sep 17 00:00:00 2001
From: Max Sandholm <vurpo@vurpo.fi>
Date: Thu, 22 Jun 2023 09:09:19 +0300
Subject: [PATCH] Add option to delete outdated inbound keys (keys which lack
 the metadata about when they're safe to delete)

---
 bridge/bridgeconfig/config.go |  1 +
 bridge/crypto.go              | 10 ++++++++++
 crypto/sql_store.go           | 16 ++++++++++++++++
 crypto/store.go               |  6 ++++++
 4 files changed, 33 insertions(+)

diff --git a/bridge/bridgeconfig/config.go b/bridge/bridgeconfig/config.go
index c80f5555..4cb9c777 100644
--- a/bridge/bridgeconfig/config.go
+++ b/bridge/bridgeconfig/config.go
@@ -184,6 +184,7 @@ type EncryptionConfig struct {
 		DeletePrevOnNewSession    bool `yaml:"delete_prev_on_new_session"`
 		DeleteOnDeviceDelete      bool `yaml:"delete_on_device_delete"`
 		PeriodicallyDeleteExpired bool `yaml:"periodically_delete_expired"`
+		DeleteOutdatedInbound     bool `yaml:"delete_outdated_inbound"`
 	} `yaml:"delete_keys"`
 
 	VerificationLevels struct {
diff --git a/bridge/crypto.go b/bridge/crypto.go
index c9a97894..3c3c27c0 100644
--- a/bridge/crypto.go
+++ b/bridge/crypto.go
@@ -110,6 +110,16 @@ func (helper *CryptoHelper) Init() error {
 		go helper.mach.ExpiredKeyDeleteLoop(ctx)
 	}
 
+	if encryptionConfig.DeleteKeys.DeleteOutdatedInbound {
+		deleted, err := helper.store.RedactOutdatedGroupSessions()
+		if err != nil {
+			return err
+		}
+		if len(deleted) > 0 {
+			helper.log.Debug().Int("deleted", len(deleted)).Msg("Deleted inbound keys which lacked expiration metadata")
+		}
+	}
+
 	helper.client.Syncer = &cryptoSyncer{helper.mach}
 	helper.client.Store = helper.store
 
diff --git a/crypto/sql_store.go b/crypto/sql_store.go
index 09175727..a46fb286 100644
--- a/crypto/sql_store.go
+++ b/crypto/sql_store.go
@@ -418,6 +418,22 @@ func (store *SQLCryptoStore) RedactExpiredGroupSessions() ([]id.SessionID, error
 	return sessionIDs, err
 }
 
+func (store *SQLCryptoStore) RedactOutdatedGroupSessions() ([]id.SessionID, error) {
+	res, err := store.DB.Query(`
+			UPDATE crypto_megolm_inbound_session
+			SET withheld_code=$1, withheld_reason=$2, session=NULL, forwarding_chains=NULL
+			WHERE account_id=$3 AND session IS NOT NULL AND received_at IS NULL
+			RETURNING session_id
+		`, event.RoomKeyWithheldBeeperRedacted, "Session redacted: outdated", store.AccountID)
+	var sessionIDs []id.SessionID
+	for res.Next() {
+		var sessionID id.SessionID
+		_ = res.Scan(&sessionID)
+		sessionIDs = append(sessionIDs, sessionID)
+	}
+	return sessionIDs, err
+}
+
 func (store *SQLCryptoStore) PutWithheldGroupSession(content event.RoomKeyWithheldEventContent) error {
 	_, err := store.DB.Exec("INSERT INTO crypto_megolm_inbound_session (session_id, sender_key, room_id, withheld_code, withheld_reason, received_at, account_id) VALUES ($1, $2, $3, $4, $5, $6, $7)",
 		content.SessionID, content.SenderKey, content.RoomID, content.Code, content.Reason, time.Now().UTC(), store.AccountID)
diff --git a/crypto/store.go b/crypto/store.go
index 55f70491..99e464d2 100644
--- a/crypto/store.go
+++ b/crypto/store.go
@@ -59,6 +59,8 @@ type Store interface {
 	RedactGroupSessions(id.RoomID, id.SenderKey, string) ([]id.SessionID, error)
 	// RedactExpiredGroupSessions removes the session data for all inbound Megolm sessions that have expired.
 	RedactExpiredGroupSessions() ([]id.SessionID, error)
+	// RedactOutdatedGroupSessions removes the session data for all inbound Megolm sessions that are lacking the expiration metadata.
+	RedactOutdatedGroupSessions() ([]id.SessionID, error)
 	// PutWithheldGroupSession tells the store that a specific Megolm session was withheld.
 	PutWithheldGroupSession(event.RoomKeyWithheldEventContent) error
 	// GetWithheldGroupSession gets the event content that was previously inserted with PutWithheldGroupSession.
@@ -317,6 +319,10 @@ func (gs *MemoryStore) RedactExpiredGroupSessions() ([]id.SessionID, error) {
 	return nil, fmt.Errorf("not implemented")
 }
 
+func (gs *MemoryStore) RedactOutdatedGroupSessions() ([]id.SessionID, error) {
+	return nil, fmt.Errorf("not implemented")
+}
+
 func (gs *MemoryStore) getWithheldGroupSessions(roomID id.RoomID, senderKey id.SenderKey) map[id.SessionID]*event.RoomKeyWithheldEventContent {
 	room, ok := gs.WithheldGroupSessions[roomID]
 	if !ok {