Key Backups (2/3) : Add E2E backup key tables (#1945)

* Add PUT key backup endpoints and glue them to PerformKeyBackup

* Add tables for storing backup keys and glue them into the user API

* Don't create tables whilst still WIPing

* writer on sqlite please

* Linting

3 files changed, 268 insertions, 16 deletions

diff --git a/userapi/storage/accounts/sqlite3/key_backup_table.go b/userapi/storage/accounts/sqlite3/key_backup_table.go
new file mode 100644
index 00000000..268bda93
--- /dev/null
+++ b/userapi/storage/accounts/sqlite3/key_backup_table.go
@@ -0,0 +1,134 @@
+// Copyright 2021 The Matrix.org Foundation C.I.C.
+//
+// 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 sqlite3
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+
+	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/userapi/api"
+)
+
+const keyBackupTableSchema = `
+CREATE TABLE IF NOT EXISTS account_e2e_room_keys (
+    user_id TEXT NOT NULL,
+    room_id TEXT NOT NULL,
+    session_id TEXT NOT NULL,
+
+    version TEXT NOT NULL,
+    first_message_index INTEGER NOT NULL,
+    forwarded_count INTEGER NOT NULL,
+    is_verified BOOLEAN NOT NULL,
+    session_data TEXT NOT NULL
+);
+CREATE UNIQUE INDEX IF NOT EXISTS e2e_room_keys_idx ON account_e2e_room_keys(user_id, room_id, session_id);
+`
+
+const insertBackupKeySQL = "" +
+	"INSERT INTO account_e2e_room_keys(user_id, room_id, session_id, version, first_message_index, forwarded_count, is_verified, session_data) " +
+	"VALUES ($1, $2, $3, $4, $5, $6, $7, $8)"
+
+const updateBackupKeySQL = "" +
+	"UPDATE account_e2e_room_keys SET first_message_index=$1, forwarded_count=$2, is_verified=$3, session_data=$4 " +
+	"WHERE user_id=$5 AND room_id=$6 AND session_id=$7 AND version=$8"
+
+const countKeysSQL = "" +
+	"SELECT COUNT(*) FROM account_e2e_room_keys WHERE user_id = $1 AND version = $2"
+
+const selectKeysSQL = "" +
+	"SELECT room_id, session_id, first_message_index, forwarded_count, is_verified, session_data FROM account_e2e_room_keys " +
+	"WHERE user_id = $1 AND version = $2"
+
+type keyBackupStatements struct {
+	insertBackupKeyStmt *sql.Stmt
+	updateBackupKeyStmt *sql.Stmt
+	countKeysStmt       *sql.Stmt
+	selectKeysStmt      *sql.Stmt
+}
+
+// nolint:unused
+func (s *keyBackupStatements) prepare(db *sql.DB) (err error) {
+	_, err = db.Exec(keyBackupTableSchema)
+	if err != nil {
+		return
+	}
+	if s.insertBackupKeyStmt, err = db.Prepare(insertBackupKeySQL); err != nil {
+		return
+	}
+	if s.updateBackupKeyStmt, err = db.Prepare(updateBackupKeySQL); err != nil {
+		return
+	}
+	if s.countKeysStmt, err = db.Prepare(countKeysSQL); err != nil {
+		return
+	}
+	if s.selectKeysStmt, err = db.Prepare(selectKeysSQL); err != nil {
+		return
+	}
+	return
+}
+
+func (s keyBackupStatements) countKeys(
+	ctx context.Context, txn *sql.Tx, userID, version string,
+) (count int64, err error) {
+	err = txn.Stmt(s.countKeysStmt).QueryRowContext(ctx, userID, version).Scan(&count)
+	return
+}
+
+func (s *keyBackupStatements) insertBackupKey(
+	ctx context.Context, txn *sql.Tx, userID, version string, key api.InternalKeyBackupSession,
+) (err error) {
+	_, err = txn.Stmt(s.insertBackupKeyStmt).ExecContext(
+		ctx, userID, key.RoomID, key.SessionID, version, key.FirstMessageIndex, key.ForwardedCount, key.IsVerified, string(key.SessionData),
+	)
+	return
+}
+
+func (s *keyBackupStatements) updateBackupKey(
+	ctx context.Context, txn *sql.Tx, userID, version string, key api.InternalKeyBackupSession,
+) (err error) {
+	_, err = txn.Stmt(s.updateBackupKeyStmt).ExecContext(
+		ctx, key.FirstMessageIndex, key.ForwardedCount, key.IsVerified, string(key.SessionData), userID, key.RoomID, key.SessionID, version,
+	)
+	return
+}
+
+func (s *keyBackupStatements) selectKeys(
+	ctx context.Context, txn *sql.Tx, userID, version string,
+) (map[string]map[string]api.KeyBackupSession, error) {
+	result := make(map[string]map[string]api.KeyBackupSession)
+	rows, err := txn.Stmt(s.selectKeysStmt).QueryContext(ctx, userID, version)
+	if err != nil {
+		return nil, err
+	}
+	defer internal.CloseAndLogIfError(ctx, rows, "selectKeysStmt.Close failed")
+	for rows.Next() {
+		var key api.InternalKeyBackupSession
+		// room_id, session_id, first_message_index, forwarded_count, is_verified, session_data
+		var sessionDataStr string
+		if err := rows.Scan(&key.RoomID, &key.SessionID, &key.FirstMessageIndex, &key.ForwardedCount, &key.IsVerified, &sessionDataStr); err != nil {
+			return nil, err
+		}
+		key.SessionData = json.RawMessage(sessionDataStr)
+		roomData := result[key.RoomID]
+		if roomData == nil {
+			roomData = make(map[string]api.KeyBackupSession)
+		}
+		roomData[key.SessionID] = key.KeyBackupSession
+		result[key.RoomID] = roomData
+	}
+	return result, nil
+}
diff --git a/userapi/storage/accounts/sqlite3/key_backup_version_table.go b/userapi/storage/accounts/sqlite3/key_backup_version_table.go
index 3e85705c..72e9b132 100644
--- a/userapi/storage/accounts/sqlite3/key_backup_version_table.go
+++ b/userapi/storage/accounts/sqlite3/key_backup_version_table.go
@@ -31,6 +31,7 @@ CREATE TABLE IF NOT EXISTS account_e2e_room_keys_versions (
     version INTEGER PRIMARY KEY AUTOINCREMENT,
     algorithm TEXT NOT NULL,
     auth_data TEXT NOT NULL,
+	etag TEXT NOT NULL,
     deleted INTEGER DEFAULT 0 NOT NULL
 );
 
@@ -38,16 +39,19 @@ CREATE UNIQUE INDEX IF NOT EXISTS account_e2e_room_keys_versions_idx ON account_
 `
 
 const insertKeyBackupSQL = "" +
-	"INSERT INTO account_e2e_room_keys_versions(user_id, algorithm, auth_data) VALUES ($1, $2, $3) RETURNING version"
+	"INSERT INTO account_e2e_room_keys_versions(user_id, algorithm, auth_data, etag) VALUES ($1, $2, $3, $4) RETURNING version"
 
-const updateKeyBackupAuthDataSQL = "" + // TODO: do we need to WHERE algorithm = $3 as well?
+const updateKeyBackupAuthDataSQL = "" +
 	"UPDATE account_e2e_room_keys_versions SET auth_data = $1 WHERE user_id = $2 AND version = $3"
 
+const updateKeyBackupETagSQL = "" +
+	"UPDATE account_e2e_room_keys_versions SET etag = $1 WHERE user_id = $2 AND version = $3"
+
 const deleteKeyBackupSQL = "" +
 	"UPDATE account_e2e_room_keys_versions SET deleted=1 WHERE user_id = $1 AND version = $2"
 
 const selectKeyBackupSQL = "" +
-	"SELECT algorithm, auth_data, deleted FROM account_e2e_room_keys_versions WHERE user_id = $1 AND version = $2"
+	"SELECT algorithm, auth_data, etag, deleted FROM account_e2e_room_keys_versions WHERE user_id = $1 AND version = $2"
 
 const selectLatestVersionSQL = "" +
 	"SELECT MAX(version) FROM account_e2e_room_keys_versions WHERE user_id = $1"
@@ -58,8 +62,10 @@ type keyBackupVersionStatements struct {
 	deleteKeyBackupStmt         *sql.Stmt
 	selectKeyBackupStmt         *sql.Stmt
 	selectLatestVersionStmt     *sql.Stmt
+	updateKeyBackupETagStmt     *sql.Stmt
 }
 
+// nolint:unused
 func (s *keyBackupVersionStatements) prepare(db *sql.DB) (err error) {
 	_, err = db.Exec(keyBackupVersionTableSchema)
 	if err != nil {
@@ -80,14 +86,17 @@ func (s *keyBackupVersionStatements) prepare(db *sql.DB) (err error) {
 	if s.selectLatestVersionStmt, err = db.Prepare(selectLatestVersionSQL); err != nil {
 		return
 	}
+	if s.updateKeyBackupETagStmt, err = db.Prepare(updateKeyBackupETagSQL); err != nil {
+		return
+	}
 	return
 }
 
 func (s *keyBackupVersionStatements) insertKeyBackup(
-	ctx context.Context, txn *sql.Tx, userID, algorithm string, authData json.RawMessage,
+	ctx context.Context, txn *sql.Tx, userID, algorithm string, authData json.RawMessage, etag string,
 ) (version string, err error) {
 	var versionInt int64
-	err = txn.Stmt(s.insertKeyBackupStmt).QueryRowContext(ctx, userID, algorithm, string(authData)).Scan(&versionInt)
+	err = txn.Stmt(s.insertKeyBackupStmt).QueryRowContext(ctx, userID, algorithm, string(authData), etag).Scan(&versionInt)
 	return strconv.FormatInt(versionInt, 10), err
 }
 
@@ -102,6 +111,17 @@ func (s *keyBackupVersionStatements) updateKeyBackupAuthData(
 	return err
 }
 
+func (s *keyBackupVersionStatements) updateKeyBackupETag(
+	ctx context.Context, txn *sql.Tx, userID, version, etag string,
+) error {
+	versionInt, err := strconv.ParseInt(version, 10, 64)
+	if err != nil {
+		return fmt.Errorf("invalid version")
+	}
+	_, err = txn.Stmt(s.updateKeyBackupETagStmt).ExecContext(ctx, etag, userID, versionInt)
+	return err
+}
+
 func (s *keyBackupVersionStatements) deleteKeyBackup(
 	ctx context.Context, txn *sql.Tx, userID, version string,
 ) (bool, error) {
@@ -122,7 +142,7 @@ func (s *keyBackupVersionStatements) deleteKeyBackup(
 
 func (s *keyBackupVersionStatements) selectKeyBackup(
 	ctx context.Context, txn *sql.Tx, userID, version string,
-) (versionResult, algorithm string, authData json.RawMessage, deleted bool, err error) {
+) (versionResult, algorithm string, authData json.RawMessage, etag string, deleted bool, err error) {
 	var versionInt int64
 	if version == "" {
 		err = txn.Stmt(s.selectLatestVersionStmt).QueryRowContext(ctx, userID).Scan(&versionInt)
@@ -135,7 +155,7 @@ func (s *keyBackupVersionStatements) selectKeyBackup(
 	versionResult = strconv.FormatInt(versionInt, 10)
 	var deletedInt int
 	var authDataStr string
-	err = txn.Stmt(s.selectKeyBackupStmt).QueryRowContext(ctx, userID, versionInt).Scan(&algorithm, &authDataStr, &deletedInt)
+	err = txn.Stmt(s.selectKeyBackupStmt).QueryRowContext(ctx, userID, versionInt).Scan(&algorithm, &authDataStr, &etag, &deletedInt)
 	deleted = deletedInt == 1
 	authData = json.RawMessage(authDataStr)
 	return
diff --git a/userapi/storage/accounts/sqlite3/storage.go b/userapi/storage/accounts/sqlite3/storage.go
index b10f25ad..4fae621f 100644
--- a/userapi/storage/accounts/sqlite3/storage.go
+++ b/userapi/storage/accounts/sqlite3/storage.go
@@ -19,6 +19,7 @@ import (
 	"database/sql"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"strconv"
 	"sync"
 	"time"
@@ -43,7 +44,8 @@ type Database struct {
 	accountDatas          accountDataStatements
 	threepids             threepidStatements
 	openIDTokens          tokenStatements
-	keyBackups            keyBackupVersionStatements
+	keyBackupVersions     keyBackupVersionStatements
+	keyBackups            keyBackupStatements
 	serverName            gomatrixserverlib.ServerName
 	bcryptCost            int
 	openIDTokenLifetimeMS int64
@@ -98,9 +100,13 @@ func NewDatabase(dbProperties *config.DatabaseOptions, serverName gomatrixserver
 	if err = d.openIDTokens.prepare(db, serverName); err != nil {
 		return nil, err
 	}
-	if err = d.keyBackups.prepare(db); err != nil {
-		return nil, err
-	}
+	/*
+		if err = d.keyBackupVersions.prepare(db); err != nil {
+			return nil, err
+		}
+		if err = d.keyBackups.prepare(db); err != nil {
+			return nil, err
+		} */
 
 	return d, nil
 }
@@ -418,7 +424,7 @@ func (d *Database) CreateKeyBackup(
 	ctx context.Context, userID, algorithm string, authData json.RawMessage,
 ) (version string, err error) {
 	err = d.writer.Do(d.db, nil, func(txn *sql.Tx) error {
-		version, err = d.keyBackups.insertKeyBackup(ctx, txn, userID, algorithm, authData)
+		version, err = d.keyBackupVersions.insertKeyBackup(ctx, txn, userID, algorithm, authData, "")
 		return err
 	})
 	return
@@ -428,7 +434,7 @@ func (d *Database) UpdateKeyBackupAuthData(
 	ctx context.Context, userID, version string, authData json.RawMessage,
 ) (err error) {
 	err = d.writer.Do(d.db, nil, func(txn *sql.Tx) error {
-		return d.keyBackups.updateKeyBackupAuthData(ctx, txn, userID, version, authData)
+		return d.keyBackupVersions.updateKeyBackupAuthData(ctx, txn, userID, version, authData)
 	})
 	return
 }
@@ -437,7 +443,7 @@ func (d *Database) DeleteKeyBackup(
 	ctx context.Context, userID, version string,
 ) (exists bool, err error) {
 	err = d.writer.Do(d.db, nil, func(txn *sql.Tx) error {
-		exists, err = d.keyBackups.deleteKeyBackup(ctx, txn, userID, version)
+		exists, err = d.keyBackupVersions.deleteKeyBackup(ctx, txn, userID, version)
 		return err
 	})
 	return
@@ -445,10 +451,102 @@ func (d *Database) DeleteKeyBackup(
 
 func (d *Database) GetKeyBackup(
 	ctx context.Context, userID, version string,
-) (versionResult, algorithm string, authData json.RawMessage, deleted bool, err error) {
+) (versionResult, algorithm string, authData json.RawMessage, etag string, deleted bool, err error) {
 	err = d.writer.Do(d.db, nil, func(txn *sql.Tx) error {
-		versionResult, algorithm, authData, deleted, err = d.keyBackups.selectKeyBackup(ctx, txn, userID, version)
+		versionResult, algorithm, authData, etag, deleted, err = d.keyBackupVersions.selectKeyBackup(ctx, txn, userID, version)
 		return err
 	})
 	return
 }
+
+// nolint:nakedret
+func (d *Database) UpsertBackupKeys(
+	ctx context.Context, version, userID string, uploads []api.InternalKeyBackupSession,
+) (count int64, etag string, err error) {
+	// wrap the following logic in a txn to ensure we atomically upload keys
+	err = d.writer.Do(d.db, nil, func(txn *sql.Tx) error {
+		_, _, _, oldETag, deleted, err := d.keyBackupVersions.selectKeyBackup(ctx, txn, userID, version)
+		if err != nil {
+			return err
+		}
+		if deleted {
+			return fmt.Errorf("backup was deleted")
+		}
+		// pull out all keys for this (user_id, version)
+		existingKeys, err := d.keyBackups.selectKeys(ctx, txn, userID, version)
+		if err != nil {
+			return err
+		}
+
+		changed := false
+		// loop over all the new keys (which should be smaller than the set of backed up keys)
+		for _, newKey := range uploads {
+			// if we have a matching (room_id, session_id), we may need to update the key if it meets some rules, check them.
+			existingRoom := existingKeys[newKey.RoomID]
+			if existingRoom != nil {
+				existingSession, ok := existingRoom[newKey.SessionID]
+				if ok {
+					if shouldReplaceRoomKey(existingSession, newKey.KeyBackupSession) {
+						err = d.keyBackups.updateBackupKey(ctx, txn, userID, version, newKey)
+						changed = true
+						if err != nil {
+							return err
+						}
+					}
+					// if we shouldn't replace the key we do nothing with it
+					continue
+				}
+			}
+			// if we're here, either the room or session are new, either way, we insert
+			err = d.keyBackups.insertBackupKey(ctx, txn, userID, version, newKey)
+			changed = true
+			if err != nil {
+				return err
+			}
+		}
+
+		count, err = d.keyBackups.countKeys(ctx, txn, userID, version)
+		if err != nil {
+			return err
+		}
+		if changed {
+			// update the etag
+			var newETag string
+			if oldETag == "" {
+				newETag = "1"
+			} else {
+				oldETagInt, err := strconv.ParseInt(oldETag, 10, 64)
+				if err != nil {
+					return fmt.Errorf("failed to parse old etag: %s", err)
+				}
+				newETag = strconv.FormatInt(oldETagInt+1, 10)
+			}
+			etag = newETag
+			return d.keyBackupVersions.updateKeyBackupETag(ctx, txn, userID, version, newETag)
+		} else {
+			etag = oldETag
+		}
+
+		return nil
+	})
+	return
+}
+
+// TODO FIXME XXX : This logic really shouldn't live in the storage layer, but I don't know where else is sensible which won't
+// create circular import loops
+func shouldReplaceRoomKey(existing, uploaded api.KeyBackupSession) bool {
+	// https://spec.matrix.org/unstable/client-server-api/#backup-algorithm-mmegolm_backupv1curve25519-aes-sha2
+	// "if the keys have different values for is_verified, then it will keep the key that has is_verified set to true"
+	if uploaded.IsVerified && !existing.IsVerified {
+		return true
+	}
+	// "if they have the same values for is_verified, then it will keep the key with a lower first_message_index"
+	if uploaded.FirstMessageIndex < existing.FirstMessageIndex {
+		return true
+	}
+	// "and finally, is is_verified and first_message_index are equal, then it will keep the key with a lower forwarded_count"
+	if uploaded.ForwardedCount < existing.ForwardedCount {
+		return true
+	}
+	return false
+}