Browser Security Lessons from Google Chrome

The Web has become one of the primary ways people interact with their computers, connecting people with a diverse landscape of content, services, and applications. Users can find new and interesting content on the Web easily, but this presents a security challenge: malicious Web-site operators can attack users through their Web browsers. Browsers face the challenge of keeping their users safe while providing a rich platform for Web applications.

Browsers are an appealing target for attackers because they have a large and complex trusted computing base with a wide network-visible interface. Historically, every browser at some point has contained a bug that let a malicious Web-site operator circumvent the browser’s security policy and compromise the user’s computer. Even after these vulnerabilities are patched, many users continue to run older, vulnerable versions.5 When these users visit malicious Web sites, they run the risk of having their computers compromised.

Google Chrome uses a modular architecture that places the complex rendering engine in a low-
privilege sandbox, which we discuss in depth in a separate report.1 Google Chrome has two major components that run in different operating-system processes: a high-privilege browser kernel and a low-privilege rendering engine. The browser kernel acts with the user’s authority and is responsible for drawing the user interface, storing the cookie and history databases, and providing network access. The rendering engine acts on behalf of the Web principal and is not trusted to interact with the user’s fi le system. The rendering engine parses HTML, executes JavaScript, decodes images, paints to an off-screen buffer, and performs other tasks necessary for rendering Web pages.

Google Chrome also makes vulnerabilities harder to exploit by using several barriers recommended for Windows programs.8 These include DEP (data execution prevention), ASLR (address space layout randomization), SafeSEH (safe exception handlers), heap corruption detection, and stack overrun detection (GS). These are available in recent versions of Windows, and several browsers have adopted them to thwart exploits.

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