Every so often (okay, ALL THE TIME) someone (Linux users, of course 🙂 ) wonders why Mozilla doesn’t use platform libraries for things like networking code. One commonly-argued reason is that it gives us the flexibility to fix security problems without waiting on those upstream libraries to make the fix themselves — we control the code, and we can make the fixes ourselves.
Another reason not to use platform libraries occurred to me while reading Planet WebKit today, specifically the recent WebKit’s week – #7 post. Quoting from that post, added emphasis mine:
HttpOnly Cookie (38566)
An Internet Explorer extension (added in Firefox and Opera since) will soon be supported by WebKit based browsers. This restricts the access to certain cookies. They are only available for an HTTP request and so not from JavaScript. This is an important functionality to restrict the damages of an XSS vulnerability. This is not available in the nightlies because you need some updated Apple proprietary libraries (CFNetwork).
As noted, Firefox supports HTTPOnly cookies; after the patch to add this support was committed, you could download nightly builds which included the fix, and HTTPOnly would Just Work. No mess of upgrading platform libraries to make it happen, no separate-package updating, no waiting on Apple to update their platform libraries. (Incidentally, will Apple make those updates for 10.4 users as well, assuming they even decide to release a browser upgrade for a, er, “dying” OS release? Maybe, maybe not, who can say; “Apple does not comment on future products.”) Just download the build, build it from source yourself if you like building from source or if you’re a Gentoo ricer, and you have a working browser with the fix.
There are tradeoffs to be made rolling your own code when you could use something provided by the OS or by a third-party library. However, it should be equally clear that there are tradeoffs to be made going the other way, at least if you truly care about being cross-platform.
(On an almost entirely unrelated note, I was pleased to discover while writing this post that HTML5‘s outline-generation algorithm properly handles headings inside blockquote elements. Yay for specs anticipating my concerns! 😀 )