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Google Native Client Puts x86 On the Web
t3rmin4t0r writes "Google has announced its Google native client, which enables x86 native code to be run securely inside a browser. With Java applets already dead and buried, this could mean the end of the new war between browsers and the various JavaScript engines (V8, Squirrelfish, Tracemonkey). The only question remains whether it can be secured (ala ActiveX) and whether the advantages carry over onto non-x86 platforms. The package is available for download from its Google code site. Hopefully, I can finally write my web apps in asm." Note: the Google code page description points out that this is not ready for production use: "We've released this project at an early, research stage to get feedback from the security and broader open-source communities." Reader eldavojohn links to a technical paper linked from that Google code page [PDF] titled "Native Client: A Sandbox for Portable, Untrusted x86 Native Code," and suggests this in-browser Quake demo, which requires the Native Code plug-in.
Java is compiled Just-in-time, though I don't know about smaller, obscure or embedded platforms.
True confidence comes not from realising you are as good as your peers, but that your peers are as bad as you are.
x86 code runs natively on 90% of the processors out there. Java or .NET bytecode runs natively on about 0% of them (Sun did have a Java chip once but it is long dead). So it is hardly any worse than the alternatives. There are many x86 emulators and some of them have reasonable performance.
ARM Jazelle (in quite a number of the ARM revisions deployed all over the place) includes DBX for direct bytecode execution of Java. That includes the iphone and loads of other stuff.
From the article linked from the story, emphasis mine:
The release contains the experimental compilation tools and runtime so that you can write and run portable code modules that will work in Firefox, Safari, Opera, and Google Chrome on any modern Windows, Mac, or Linux system that has an x86 processor. We're working on supporting other CPU architectures (such as ARM and PPC) to make this technology work on the many types of devices that connect to the web today.
Reading Comprehension FTW!
For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...
Try Java6 update 10 and you'll be surprised. The plugin loads instantaneously and I believe applets load jars on demand as well.
This is a fascinating effort. Read the research paper.
This is really a little operating system, with 44 system calls. Those system calls are the same on Linux, MacOS (IA-32 version) and Windows. That could make this very useful - the same executable can run on all major platforms.
Note that you can't use existing executables. Code has to be recompiled for this environment. Among other things, the "ret" instruction has to be replaced with a different, safer sequence. Also, there's no access to the GPU, so games in the browser will be very limited. As a demo, they ported Quake, but the rendering is entirely on the main CPU. If they wanted to support graphics cross-platform, they could put in OpenGL support.
Executable code is pre-scanned by the loader, sort of like VMware. Unlike VMware, the hard cases are simply disallowed, rather than being interpreted. Most of the things that are disallowed you wouldn't want to do anyway except in an exploit.
This sandbox system makes heavy use of some protection machinery in IA-32 that's unused by existing operating systems. IA-32 has some elaborate segmentation hardware which allows constraining access at a fine-grained level. I once looked into using that hardware for an interprocess communication system with mutual mistrust, trying to figure out a way to lower the cost of secure IPC. There's a seldom-used "call gate" in IA-32 mechanism that almost, but not quite, does the right thing in doing segment switches at a call across a protection boundary. The Google people got cross-boundary calls to work with a "trampoline code" system that works more like a system call, transferring from untrusted to trusted code. This is more like classic "rings of protection" from Multics.
Note that this won't work for 64-bit code. When AMD came up with their extension to IA-32 to 64 bits, they decided to leave out all the classic x86 segmentation machinery because nobody was using it. (I got that info from the architecture designer when he spoke at Stanford.) 64-bit mode is flat address space only.
An interpreter compiles each instruction every time it gets executed.
JIT compiles blocks of code only on first execution. Next time, the compiled code is already in memory.
Why not? It just means that the permissible instruction sequences are limited to a subset that can be statically analyzed and verified to be safe. The Java VM has similar verification algorithms that are run whenever untrusted code is first loaded.
It's true that this does not allow all x86 code to run; it's at least practically (and probably theoretically) impossible to correctly determine whether or not a piece of code is safe, but as long as the VM errs on the side of caution, there shouldn't be any problems with this approach.
I will grant that this makes it unclear what the advantage is over (say) Java applets. What can this technology do that the Java VM couldn't? As far as I'm concerned, the failure of Java in the browser has more to do with the lack of a standard library for high-performance multimedia applications (think: Flash) than with shortcomings in the bytecode language.
All this means is that google have created a VM in which the "bytecodes" happen to be executable on real hardware, but some of these "bytecodes" have to be intercepted and replaced at runtime with substitute code... this aught to sound familiar; this is what a software hypervisor does (eg VMware).
In other words every man and his dog has jumped aboard the "I can write an x86-hypervisor" bandwagon, the difference being that google have decided to take theirs and embed it into the browser rather than run as a standalone app.
Interestingly enough it took the momentum that VMware created to get intel to correct some of the issues with its' ISA to make it much easier to virtualise, perhaps someone the size of google can prod intel into adding a third wave of virtualisation accelartion extensions to their ISA so as to make this idea safer* with low overhead
*I think virtualisation is a useful thing (I make a living from consulting on it), however I am unconvinced of it being possible, to truly secure it.
Andy Warhol got it right / Everybody gets the limelight
Andy Warhol got it wrong / Fifteen minutes is too long.
Holy crap. AKAImBatman I usually enjoy your posts, but it's painfully clear nobody on this thread - including you - has actually read the paper.
If you had, you'd see that this system is secure. It's simple yet clever at the same time. By using a combination of x86 segmentation (which ironically you say is never used anymore!), alignment rules, static analysis and - crucially - masked jumps, it's possible to ensure that native code cannot synthesize unverified code in memory and then jump into it. If you can prevent arbitrary code synthesis, you can control what the program does. It's as simple as that.
Even though the verifier for this system is microscopic (compared to, say, a JVM), and so much more likely to be correct, NativeClient also includes a ptrace sandbox to provide an additional redundant level of protection.
I don't blame you, because until I read the paper I also believed this. Once you read it you'll slap your forehead and say, my god, it's so simple. Why didn't I think of that?