The Servo next-generation rendering engine was written using the Rust programming language in order to address potential security vulnerabilities. Developers can find the source code in Mozilla's GitHub repository and nightly in-development builds for MacOS and Linux on Servo Developer Preview Downloads. Windows and Android packages are expected shortly.
Jack Moffitt, Mozilla's Servo project lead, had previously said Servo "reimagines the architecture of the browser in the modern landscape of multicore computers, GPUs, and safer programming languages."
Servo is written in Rust, Mozilla's own C-like systems programming language, to ensure thread-safe concurrency and prevent common programming mistakes that can result in exploitable security flaws. Fewer security bugs in Rust code means fewer opportunities for exploitable flaws in the rendering engine, which is a crucial step toward overall web application security.
The Rust compiler won't build an application if it detects problematic code. For example, each variable in Rust has a specified owner and a lifetime, and another owner cannot use the variable when in use by the first owner, enforcing memory safety. Servo won't have the usual use-after-free flaws and buffer overflows prevalent in many applications because they aren't possible in Rust code.
Even so, Servo lays the groundwork for Mozilla to move forward with improvements to other browser components. With so many attacks using the web browser as the entry point, a secure rendering engine for the web browser is an important step toward giving users a more secure internet experience.
Mozilla said in its Servo road map back in March that the long-term plan is to "incrementally replace components in Gecko with ones written in Rust and shared with Servo." While Mozilla may not explicitly replace Gecko as the rendering engine for Firefox with Servo, it appears enough of Servo's code will eventually make its way to Gecko to make the two essentially the same thing.
Mozilla wil incorporate Rust code into components used by Gecko and Firefox as part of its Oxidation project, including the URL parser, MP4 metadata parser, and the WebM demuxer. Rust will also be used to replace
encoding-rs and in CSS style calculations, work which is already in progress in order to use Servo's style code in Gecko.
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