![]() ![]() Since all JSActors are lazy-loaded we suggest to exercise the implemented functionality at least once, to ensure they are all present and allow for a smooth test and debug experience.Ĭode sample for a receiveMessage function in a JSActorĪs illustrated, the PromptParent has a receiveMessage handler (line 127) and is passing the message data to additional functions that will decide where and how to open a prompt from the parent process. There is a separate parent instance for every pair in order to closely and consistently associate a message with either a specific content window (JSWindowActors), or child process (JSProcessActors). JSActors always come in pairs – with one implementation living in the child process and the counterpart in the parent. #Sandboxie firefox code#Using a JSActor is the preferred method for JS code to communicate between processes. Let’s look at JSActors and MessageManager, the two most common patterns for using inter-process communication (IPC) from JavaScript: JSActors This level of privilege separation also requires receiving messages from content processes. Additionally, various control features like modal dialogs, form auto-fill or native user interface pieces (e.g., the element) are also implemented in the parent process. Some features, like our settings page at about:preferences are essentially web pages (using HTML and JavaScript) that are hosted in the parent process. The parent process acts as a broker and trusted user interface host. Right: Fission-enabled Firefox, separating each site in its own process Left: Current Firefox generally grouping a tab in its own process. Here, we will focus on the communication between the main process (also called “parent”) and a multitude of web processes (or “content” processes).įirefox is shifting towards a new security architecture to achieve Site Isolation, which moves from a “process per tab” to a “process per site” architecture. These types are web content processes, semi-privileged web content processes (for special websites like or ) and four kinds of utility processes for web extensions, GPU operations, networking or media decoding. Multi-Process Architecture Now and ThenĪs of April 2021, Firefox uses one privileged process to launch other process types and coordinate activities. Eventually, by finding more sandbox escapes you can help secure hundreds of millions of Firefox users as part of the Firefox Bug Bounty Program. We believe the bug provides a great case study and the underlying techniques will help identify similar issues. This 0day-bug has found extensive coverage in blog posts and publicly available exploits. Once equipped with this knowledge, we will revisit a sandbox escape bug that was used in a 0day attack against Coinbase in 2019 and reported as CVE-2019-11708. Using Firefox’s Developer Tools (DevTools), we will be able to debug the browser itself. We will then move on to examine two different JavaScript patterns for IPC and explain how to invoke them. First, we will briefly revisit the multi-process architecture and upcoming changes for Project Fission, Firefox’ implementation for Site Isolation. This blog post will look at IPC in JavaScript, which is used in various parts of the user interface. A previous blog post focused on fuzzing the C++ side of IPC. Firefox uses Inter-Process Communication (IPC) to implement privilege separation, which makes it an important cornerstone in our security architecture. ![]()
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