security: encrypt Security activity journal (Closes #1118)

src/security_event_store.py

@@ -7,6 +7,11 @@ from pathlib import Path
 from typing import Callable
 
 from src.private_state import connect_private_sqlite
+from src.state_encryption import (
+    PrivateStateCipher,
+    PrivateStateEncryptionError,
+    private_state_encryption_key,
+)
 
 
 class SecurityEventStoreError(RuntimeError):
@@ -39,12 +44,22 @@ class SecurityEventStore:
         max_events: int = 10_000,
         retention_seconds: int = 90 * 24 * 60 * 60,
         lock_timeout_seconds: float = 0.1,
+        encryption_key: bytes | None = None,
     ) -> None:
         self.path = Path(path)
         self.clock = clock
         self.max_events = max(1, max_events)
         self.retention_seconds = max(1, retention_seconds)
         self.lock_timeout_seconds = lock_timeout_seconds
+        try:
+            self._cipher = PrivateStateCipher(
+                encryption_key if encryption_key is not None else private_state_encryption_key(),
+                store="security-events",
+            )
+        except PrivateStateEncryptionError as exc:
+            raise SecurityEventStoreError(
+                "Security activity is temporarily unavailable"
+            ) from exc
 
     @staticmethod
     def _bounded(value: str | None, limit: int) -> str | None:
@@ -60,10 +75,11 @@ class SecurityEventStore:
                 """
                 CREATE TABLE IF NOT EXISTS security_events (
                     id INTEGER PRIMARY KEY AUTOINCREMENT,
-                    kind TEXT NOT NULL,
+                    kind TEXT,
                     method TEXT,
                     device_label TEXT,
                     target TEXT,
+                    payload TEXT,
                     created_at INTEGER NOT NULL,
                     status TEXT NOT NULL DEFAULT 'completed',
                     operation_id TEXT
@@ -81,6 +97,8 @@ class SecurityEventStore:
                 connection.execute(
                     "ALTER TABLE security_events ADD COLUMN operation_id TEXT"
                 )
+            if "payload" not in columns:
+                self._migrate_plaintext(connection)
             connection.execute(
                 "CREATE INDEX IF NOT EXISTS security_events_created "
                 "ON security_events(created_at DESC, id DESC)"
@@ -95,6 +113,53 @@ class SecurityEventStore:
                 "Security activity is temporarily unavailable"
             ) from exc
 
+    def _migrate_plaintext(self, connection: sqlite3.Connection) -> None:
+        connection.execute("PRAGMA secure_delete = ON")
+        rows = connection.execute(
+            "SELECT id, kind, method, device_label, target, created_at, status, operation_id "
+            "FROM security_events ORDER BY id"
+        ).fetchall()
+        connection.execute(
+            """
+            CREATE TABLE security_events_encrypted (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                kind TEXT,
+                method TEXT,
+                device_label TEXT,
+                target TEXT,
+                payload TEXT,
+                created_at INTEGER NOT NULL,
+                status TEXT NOT NULL DEFAULT 'completed',
+                operation_id TEXT
+            )
+            """
+        )
+        for (
+            event_id,
+            kind,
+            method,
+            device_label,
+            target,
+            created_at,
+            status,
+            operation_id,
+        ) in rows:
+            connection.execute(
+                "INSERT INTO security_events_encrypted "
+                "(id, payload, created_at, status, operation_id) VALUES (?, ?, ?, ?, ?)",
+                (
+                    event_id,
+                    self._seal_event(event_id, kind, method, device_label, target),
+                    created_at,
+                    status,
+                    operation_id,
+                ),
+            )
+        connection.execute("DROP TABLE security_events")
+        connection.execute(
+            "ALTER TABLE security_events_encrypted RENAME TO security_events"
+        )
+
     def _prune(self, connection: sqlite3.Connection, now: int) -> None:
         connection.execute(
             "DELETE FROM security_events WHERE created_at < ?",
@@ -106,6 +171,24 @@ class SecurityEventStore:
             (self.max_events,),
         )
 
+    def _seal_event(
+        self,
+        event_id: int,
+        kind: str,
+        method: str | None,
+        device_label: str | None,
+        target: str | None,
+    ) -> str:
+        return self._cipher.seal(
+            {
+                "kind": self._bounded(kind, 48) or "security_event",
+                "method": self._bounded(method, 32),
+                "device_label": self._bounded(device_label, 64),
+                "target": self._bounded(target, 255),
+            },
+            binding=f"event:{event_id}",
+        )
+
     def record(
         self,
         kind: str,
@@ -117,16 +200,17 @@ class SecurityEventStore:
         now = int(self.clock())
         try:
             with self._connect() as connection:
+                cursor = connection.execute(
+                    "INSERT INTO security_events(created_at, status) VALUES (?, 'completed')",
+                    (now,),
+                )
+                event_id = cursor.lastrowid
+                payload = self._seal_event(
+                    event_id, kind, method, device_label, target
+                )
                 connection.execute(
-                    "INSERT INTO security_events(kind, method, device_label, target, created_at, status) "
-                    "VALUES (?, ?, ?, ?, ?, 'completed')",
-                    (
-                        self._bounded(kind, 48) or "security_event",
-                        self._bounded(method, 32),
-                        self._bounded(device_label, 64),
-                        self._bounded(target, 255),
-                        now,
-                    ),
+                    "UPDATE security_events SET payload = ? WHERE id = ?",
+                    (payload, event_id),
                 )
                 self._prune(connection, now)
         except (OSError, sqlite3.Error) as exc:
@@ -146,16 +230,19 @@ class SecurityEventStore:
         operation_id = secrets.token_urlsafe(24)
         try:
             with self._connect() as connection:
+                cursor = connection.execute(
+                    "INSERT INTO security_events(created_at, status, operation_id) "
+                    "VALUES (?, 'pending', ?)",
+                    (now, operation_id),
+                )
+                event_id = cursor.lastrowid
                 connection.execute(
-                    "INSERT INTO security_events(kind, method, device_label, target, created_at, status, operation_id) "
-                    "VALUES (?, ?, ?, ?, ?, 'pending', ?)",
+                    "UPDATE security_events SET payload = ? WHERE id = ?",
                     (
-                        self._bounded(kind, 48) or "security_event",
-                        self._bounded(method, 32),
-                        self._bounded(device_label, 64),
-                        self._bounded(target, 255),
-                        now,
-                        operation_id,
+                        self._seal_event(
+                            event_id, kind, method, device_label, target
+                        ),
+                        event_id,
                     ),
                 )
                 self._prune(connection, now)
@@ -204,7 +291,7 @@ class SecurityEventStore:
         try:
             with self._connect() as connection:
                 rows = connection.execute(
-                    "SELECT id, kind, method, device_label, target, created_at, status "
+                    "SELECT id, payload, created_at, status "
                     f"FROM security_events {where} ORDER BY id DESC LIMIT ?",
                     parameters,
                 ).fetchall()
@@ -214,7 +301,32 @@ class SecurityEventStore:
             ) from exc
         has_more = len(rows) > bounded_limit
         visible = rows[:bounded_limit]
+        events = []
+        try:
+            for event_id, payload, created_at, status in visible:
+                value, _legacy = self._cipher.open(
+                    payload, binding=f"event:{event_id}"
+                )
+                if not isinstance(value, dict) or not isinstance(value.get("kind"), str):
+                    raise PrivateStateEncryptionError(
+                        "private state could not be decrypted"
+                    )
+                events.append(
+                    SecurityEvent(
+                        event_id,
+                        value["kind"],
+                        value.get("method"),
+                        value.get("device_label"),
+                        value.get("target"),
+                        created_at,
+                        status,
+                    )
+                )
+        except PrivateStateEncryptionError as exc:
+            raise SecurityEventStoreError(
+                "Security activity is temporarily unavailable"
+            ) from exc
         return SecurityEventPage(
-            events=[SecurityEvent(*row) for row in visible],
+            events=events,
             next_cursor=visible[-1][0] if has_more else None,
         )