fix: serialize @persist state for RPC returns

Clones state before returning from RPC to avoid RpcStub serialization.

Closes #99

Author: dmmulroy

packages/core/src/index.ts

@@ -2,7 +2,7 @@ import { env, DurableObject, WorkerEntrypoint } from "cloudflare:workers";
 import { Storage } from "../../storage/src/index";
 import { Alarms } from "../../alarms/src/index";
 import { Sockets } from "../../sockets/src/index";
-import { Persist, PERSISTED_VALUES, initializePersistedProperties, persistProperty } from "./persist";
+import { Persist, PERSISTED_VALUES, initializePersistedProperties, persistProperty, unwrapProxy } from "./persist";
 
 export { Persist };
 
@@ -183,8 +183,43 @@ export abstract class Actor<E> extends DurableObject<E> {
         if (!this.name) {
             this._name = DEFAULT_ACTOR_NAME;
         }
+
+        // Wrap RPC methods to unwrap proxy values for serialization
+        this._wrapMethodsForRpc();
     }
-    
+
+    /**
+     * Wraps all public methods to unwrap proxy return values for RPC serialization.
+     * @private
+     */
+    private _wrapMethodsForRpc(): void {
+        const skipMethods = new Set([
+            'constructor', '_wrapMethodsForRpc', '_initializePersistedProperties',
+            '_waitForSetName', '_persistProperty', 'setName'
+        ]);
+
+        let proto = Object.getPrototypeOf(this);
+        while (proto && proto !== Object.prototype) {
+            for (const name of Object.getOwnPropertyNames(proto)) {
+                if (skipMethods.has(name) || name.startsWith('_')) continue;
+
+                const descriptor = Object.getOwnPropertyDescriptor(proto, name);
+                if (!descriptor || typeof descriptor.value !== 'function') continue;
+
+                const original = descriptor.value;
+                const self = this;
+                (this as Record<string, unknown>)[name] = function(...args: unknown[]) {
+                    const result = original.apply(self, args);
+                    if (result instanceof Promise) {
+                        return result.then((v: unknown) => unwrapProxy(v));
+                    }
+                    return unwrapProxy(result);
+                };
+            }
+            proto = Object.getPrototypeOf(proto);
+        }
+    }
+
     /**
      * Initializes the persisted properties table and loads any stored values.
      * This is called during construction to ensure properties are loaded before any code uses them.

packages/core/src/persist.test.ts

@@ -0,0 +1,122 @@
+import { describe, expect, it } from "vitest";
+import { unwrapProxy } from "./persist";
+
+describe("unwrapProxy", () => {
+  describe("prototype pollution prevention", () => {
+    it("ignores __proto__ key in plain objects", () => {
+      const malicious = JSON.parse('{"__proto__": {"polluted": true}, "safe": 1}');
+      const result = unwrapProxy(malicious);
+
+      expect(result.safe).toBe(1);
+      expect(result.__proto__).toBeUndefined();
+      expect(({} as Record<string, unknown>).polluted).toBeUndefined();
+    });
+
+    it("ignores constructor key", () => {
+      const malicious = { constructor: { prototype: { polluted: true } }, safe: 1 };
+      const result = unwrapProxy(malicious);
+
+      expect(result.safe).toBe(1);
+      expect(result.constructor).toBeUndefined();
+    });
+
+    it("ignores prototype key", () => {
+      const malicious = { prototype: { polluted: true }, safe: 1 };
+      const result = unwrapProxy(malicious);
+
+      expect(result.safe).toBe(1);
+      expect(result.prototype).toBeUndefined();
+    });
+
+    it("filters dangerous keys in nested objects", () => {
+      const malicious = {
+        nested: JSON.parse('{"__proto__": {"polluted": true}, "valid": 2}'),
+        safe: 1,
+      };
+      const result = unwrapProxy(malicious);
+
+      expect(result.safe).toBe(1);
+      expect(result.nested.valid).toBe(2);
+      expect(result.nested.__proto__).toBeUndefined();
+    });
+
+    it("result object has null prototype", () => {
+      const input = { a: 1 };
+      const result = unwrapProxy(input);
+
+      expect(Object.getPrototypeOf(result)).toBeNull();
+    });
+  });
+
+  describe("basic functionality", () => {
+    it("handles primitives", () => {
+      expect(unwrapProxy(null)).toBeNull();
+      expect(unwrapProxy(undefined)).toBeUndefined();
+      expect(unwrapProxy(42)).toBe(42);
+      expect(unwrapProxy("str")).toBe("str");
+      expect(unwrapProxy(true)).toBe(true);
+    });
+
+    it("handles arrays", () => {
+      const input = [1, { a: 2 }, [3]];
+      const result = unwrapProxy(input);
+
+      expect(result).toEqual([1, { a: 2 }, [3]]);
+      expect(Array.isArray(result)).toBe(true);
+    });
+
+    it("handles nested objects", () => {
+      const input = { a: { b: { c: 1 } } };
+      const result = unwrapProxy(input);
+
+      expect(result.a.b.c).toBe(1);
+    });
+
+    it("handles circular references", () => {
+      const obj: Record<string, unknown> = { a: 1 };
+      obj.self = obj;
+
+      const result = unwrapProxy(obj);
+
+      expect(result.a).toBe(1);
+      expect(result.self).toBe(result);
+    });
+
+    it("handles Map", () => {
+      const input = new Map([["key", { value: 1 }]]);
+      const result = unwrapProxy(input);
+
+      expect(result instanceof Map).toBe(true);
+      expect(result.get("key")).toEqual({ value: 1 });
+    });
+
+    it("handles Set", () => {
+      const input = new Set([1, 2, { a: 3 }]);
+      const result = unwrapProxy(input);
+
+      expect(result instanceof Set).toBe(true);
+      expect(result.size).toBe(3);
+    });
+
+    it("preserves Date instances", () => {
+      const date = new Date("2024-01-01");
+      const result = unwrapProxy(date);
+
+      expect(result).toBe(date);
+    });
+
+    it("preserves RegExp instances", () => {
+      const regex = /test/gi;
+      const result = unwrapProxy(regex);
+
+      expect(result).toBe(regex);
+    });
+
+    it("preserves Error instances", () => {
+      const error = new Error("test");
+      const result = unwrapProxy(error);
+
+      expect(result).toBe(error);
+    });
+  });
+});

packages/core/src/persist.ts

@@ -15,6 +15,59 @@ export type Constructor<T = any> = {
     [PERSISTED_PROPERTIES]?: Set<string>;
 };
 
+/**
+ * Recursively unwraps proxy objects to get raw data for RPC serialization.
+ * Handles circular references by tracking visited objects.
+ * @internal
+ */
+export function unwrapProxy<T>(value: T, seen = new WeakMap<object, unknown>()): T {
+    if (value === null || value === undefined || typeof value !== 'object') {
+        return value;
+    }
+    if (value instanceof Date || value instanceof RegExp || value instanceof Error) {
+        return value;
+    }
+
+    // Handle circular references
+    const cached = seen.get(value);
+    if (cached !== undefined) {
+        return cached as T;
+    }
+
+    if (Array.isArray(value)) {
+        const result: unknown[] = [];
+        seen.set(value, result);
+        for (let i = 0; i < value.length; i++) {
+            result[i] = unwrapProxy(value[i], seen);
+        }
+        return result as T;
+    }
+    if (value instanceof Map) {
+        const result = new Map();
+        seen.set(value, result);
+        for (const [k, v] of value) {
+            result.set(k, unwrapProxy(v, seen));
+        }
+        return result as T;
+    }
+    if (value instanceof Set) {
+        const result = new Set();
+        seen.set(value, result);
+        for (const v of value) {
+            result.add(unwrapProxy(v, seen));
+        }
+        return result as T;
+    }
+
+    const result = Object.create(null) as Record<string, unknown>;
+    seen.set(value, result);
+    for (const key of Object.keys(value)) {
+        if (key === '__proto__' || key === 'constructor' || key === 'prototype') continue;
+        result[key] = unwrapProxy((value as Record<string, unknown>)[key], seen);
+    }
+    return result as T;
+}
+
 /**
  * Creates a deep proxy for objects to track nested property changes
  * @param value The value to potentially proxy
@@ -57,13 +110,19 @@ function createDeepProxy(value: any, instance: any, propertyKey: string, trigger
             if (key === IS_PROXIED) return true;
 
             // Handle special cases and built-in methods
-            if (typeof key === 'symbol' || 
-                key === 'toString' || 
-                key === 'valueOf' || 
+            if (typeof key === 'symbol' ||
+                key === 'toString' ||
+                key === 'valueOf' ||
                 key === 'constructor' ||
-                key === 'toJSON') {
+                key === '__proto__' ||
+                key === 'prototype') {
                 return Reflect.get(target, key);
             }
+
+            // Provide toJSON to enable RPC serialization
+            if (key === 'toJSON') {
+                return () => unwrapProxy(target);
+            }
 
             try {
                 // Check if the property exists
@@ -141,14 +200,17 @@ function createDeepProxy(value: any, instance: any, propertyKey: string, trigger
                 const currentValue = Reflect.get(target, key);
 
                 // Handle different type transition scenarios
-                if (currentValue !== null && 
-                    typeof currentValue === 'object' && 
-                    newValue !== null && 
-                    typeof newValue === 'object' && 
-                    !Array.isArray(currentValue) && 
+                if (currentValue !== null &&
+                    typeof currentValue === 'object' &&
+                    newValue !== null &&
+                    typeof newValue === 'object' &&
+                    !Array.isArray(currentValue) &&
                     !Array.isArray(newValue)) {
                     // Case 1: Both values are objects - merge them instead of replacing
-                    Object.assign(currentValue, newValue);
+                    for (const k of Object.keys(newValue)) {
+                        if (k === '__proto__' || k === 'constructor' || k === 'prototype') continue;
+                        (currentValue as Record<string, unknown>)[k] = (newValue as Record<string, unknown>)[k];
+                    }
                 } else if (newValue !== null && typeof newValue === 'object' && !Object.isFrozen(newValue)) {
                     // Case 2: New value is an object but current value is not (or doesn't exist)
                     // Create a new proxied object