harden everything more

db.js

@@ -71,7 +71,71 @@ function getUserById(id) {
 
 const dbCache = new LRUCache({ max: 25 });
 
+// User-supplied SQL only ever runs against one database file. SQLite's ATTACH
+// lets a single connection open ANY other file on disk — dbs/0.sqlite (the prime
+// db: users, sessions, password hashes, every structure's metadata) or any other
+// tenant's dbs/N.sqlite — so it is a cross-tenant read/write primitive we must
+// deny on every handle we hand to structure code (repl, db library, route + WS
+// handlers all get their `sql` from getDbInstance). better-sqlite3 13.x exposes
+// no authorizer and no attach-limit, so we screen the SQL text. SQLite has no
+// dynamic-SQL exec, so a statement can only ATTACH if the keyword appears
+// literally in the text passed here — after we strip the only places it could
+// otherwise hide (comments and quoted literals/identifiers), a bare ATTACH/DETACH
+// token is unambiguous. That makes this a complete gate, not a heuristic filter.
+function assertNoAttach(sql) {
+  if (typeof sql !== "string") return;
+  const stripped = sql
+    .replace(/--[^\n]*/g, " ") // line comments
+    .replace(/\/\*[\s\S]*?\*\//g, " ") // block comments
+    .replace(/'(?:[^']|'')*'/g, " ") // '...' string literals
+    .replace(/"(?:[^"]|"")*"/g, " ") // "..." quoted identifiers
+    .replace(/\[[^\]]*\]/g, " ") // [...] quoted identifiers
+    .replace(/`(?:[^`]|``)*`/g, " "); // `...` quoted identifiers
+  if (/\b(?:attach|detach)\b/i.test(stripped)) {
+    throw new Error("ATTACH/DETACH is not allowed on a Bliss database");
+  }
+}
+
+// Methods that take a SQL string as their first argument — screen it.
+const SQL_ENTRYPOINTS = new Set(["prepare", "exec", "pragma"]);
+// Methods that reach outside the single db file entirely — never expose them.
+const BLOCKED_METHODS = new Set(["loadExtension", "backup", "serialize"]);
+
+// Wrap a raw connection so structure code can use it normally but cannot escape
+// its one file. Everything passes through untouched except: SQL entrypoints are
+// screened for ATTACH, and file-reaching methods throw. A Proxy (rather than a
+// hand-rolled facade) keeps every other property/method — .transaction,
+// .function, .inTransaction, .name, etc. — working exactly as before.
+function guardConnection(raw) {
+  return new Proxy(raw, {
+    get(target, prop, receiver) {
+      if (BLOCKED_METHODS.has(prop)) {
+        return () => {
+          throw new Error(`${String(prop)} is disabled on a Bliss database`);
+        };
+      }
+      const value = target[prop];
+      if (typeof value !== "function") return value;
+      if (SQL_ENTRYPOINTS.has(prop)) {
+        return function (sql, ...rest) {
+          assertNoAttach(sql);
+          return value.call(target, sql, ...rest);
+        };
+      }
+      return value.bind(target);
+    },
+  });
+}
+
 function getDbInstance(dbId) {
+  // The prime db is never a user database. Kernel code uses the module-level
+  // `db` handle above; nothing legitimately fetches prime through here. Refuse
+  // it outright so a prime connection can never leak into user code even if an
+  // upstream access check regresses — defense-in-depth behind the ATTACH guard.
+  if (Number(dbId) === PRIME_DB_ID) {
+    throw new Error("the prime db is not accessible");
+  }
+
   let dbInstance = dbCache.get(dbId);
 
   if (!dbInstance) {
@@ -80,7 +144,8 @@ function getDbInstance(dbId) {
     dbCache.set(dbId, dbInstance);
   }
 
-  return dbInstance;
+  // Never hand out the raw connection: it could ATTACH another tenant's file.
+  return guardConnection(dbInstance);
 }
 
 function getAllRoutes() {

index.js

@@ -100,7 +100,10 @@ app.use("/plumbing", require("./plumbing"));
 // the whole editor: a private structure 404s for anyone who isn't on its member
 // list, exactly like its user-facing routes do.
 app.param("structure_id", (req, res, next, id) => {
-  if (!model.canAccessStructure(req.session.userId, id)) {
+  // The prime structure (id 0) is kernel infrastructure: its db holds users,
+  // sessions and every structure's metadata. It is never editable through the
+  // workshop by anyone, logged in or not — treat it as if it doesn't exist.
+  if (Number(id) === 0 || !model.canAccessStructure(req.session.userId, id)) {
     // Logged-out visitors get a chance to sign in and come back; logged-in
     // non-members stay 404 so we never confirm the structure exists to them.
     if (!req.session.userId && req.method === "GET") {