feat(storage): add the encrypted vault, PIN keys, lockout, session and migrations

Records are one ByteArray each: a readable TLV header plus an
encrypt-then-MAC box whose aad binds the entry ID and the header. The
device key seals unlocked entries and pending items; a random master key,
wrapped under a PBKDF2 PIN key, seals locked ones. Wrong PINs are counted
before the check, with delays on the trusted clock and an uptime fallback.
Bytes.toUtf8 validates UTF-8 first, because the native conversion crashes
on invalid input.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 89 insertions, 0 deletions

diff --git a/source/storage/Migration.mc b/source/storage/Migration.mc
new file mode 100644
index 0000000..e41d3fb
--- /dev/null
+++ b/source/storage/Migration.mc
@@ -0,0 +1,89 @@
+// Author:  cirakg & claude ai
+// Summary: Storage schema versions: create the metadata on first start, migrate old schemas, refuse newer ones.
+//
+// The metadata "m" is a dictionary:
+//     "schema"  data version (CURRENT)
+//     "ids"     entry IDs in display order
+//     "pending" IDs of pending locked entries (README 7.7)
+//
+// Rules (README 6.3):
+//   * Each migration is one small, idempotent function from version k to
+//     k + 1, run in order at start-up.
+//   * A migration that rewrites records writes each new record under a
+//     temporary key and switches the index to it before deleting the old
+//     one, so a crash or power loss mid-migration loses nothing. The only
+//     migration so far (0 to 1) changes just the metadata, in one write.
+//   * Data from a newer schema (after a downgrade) is never modified.
+//
+// Version 0 never shipped: it is a fixture layout ("m" = {"order" => ids})
+// that exists to test the migration machinery before a real migration is
+// needed.
+
+import Toybox.Application;
+import Toybox.Lang;
+
+module Migration {
+
+    const CURRENT = 1;
+    const META_KEY = "m";
+
+    // The metadata at the CURRENT schema, migrating or creating it as needed.
+    // Throws VaultError NEWER_SCHEMA or DAMAGED.
+    function run(store as Persist.Backend) as Dictionary<Application.Storage.KeyType, Application.Storage.ValueType> {
+        var stored = store.getValue(META_KEY);
+        if (stored == null) {
+            var fresh = {"schema" => CURRENT, "ids" => [], "pending" => []} as Dictionary<Application.Storage.KeyType, Application.Storage.ValueType>;
+            store.setValue(META_KEY, fresh);
+            return fresh;
+        }
+        if (!(stored instanceof Dictionary)) {
+            throw new VaultError(VaultError.DAMAGED, "metadata damaged");
+        }
+        var meta = stored as Dictionary<Application.Storage.KeyType, Application.Storage.ValueType>;
+        var schema = meta.hasKey("schema") ? meta["schema"] : 0;
+        if (!(schema instanceof Number) || schema < 0) {
+            throw new VaultError(VaultError.DAMAGED, "metadata damaged");
+        }
+        if (schema > CURRENT) {
+            throw new VaultError(VaultError.NEWER_SCHEMA, "data from a newer version");
+        }
+        if (schema == 0) {
+            meta = v0ToV1(meta);
+            store.setValue(META_KEY, meta);
+        }
+        if (!isValidV1(meta)) {
+            throw new VaultError(VaultError.DAMAGED, "metadata damaged");
+        }
+        return meta;
+    }
+
+    // Version 0 to 1: "order" becomes "ids", and "pending" is added.
+    function v0ToV1(meta as Dictionary<Application.Storage.KeyType, Application.Storage.ValueType>) as Dictionary<Application.Storage.KeyType, Application.Storage.ValueType> {
+        var order = meta["order"];
+        return {
+            "schema" => 1,
+            "ids" => order instanceof Array ? order : [],
+            "pending" => []
+        } as Dictionary<Application.Storage.KeyType, Application.Storage.ValueType>;
+    }
+
+    // True when "ids" and "pending" are arrays of distinct valid IDs.
+    function isValidV1(meta as Dictionary<Application.Storage.KeyType, Application.Storage.ValueType>) as Boolean {
+        var seen = {} as Dictionary<String, Boolean>;
+        var lists = [meta["ids"], meta["pending"]];
+        for (var l = 0; l < lists.size(); l++) {
+            var list = lists[l];
+            if (!(list instanceof Array)) {
+                return false;
+            }
+            for (var i = 0; i < list.size(); i++) {
+                var id = list[i];
+                if (!(id instanceof String) || !Entry.isValidId(id) || seen.hasKey(id)) {
+                    return false;
+                }
+                seen[id] = true;
+            }
+        }
+        return true;
+    }
+}