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Is the x86 Architecture Less Secure?
An anonymous reader asks: "Paul Murphy at CIO Today reports that a specific Windows buffer overflow vulnerability ' depends on the rigid stack-order execution and limited page protection inherent in the x86 architecture. If Windows ran on Risc, that vulnerability would still exist, but it would be a non-issue because the exploit opportunity would be more theoretical than practical.' And implies that other Windows vulnerabilities are actually facilitated by having an x86 chip." How does the x86 processor compare with other architectures when it comes to processor based vulnerabilities? How well have newer additions, like the Execute Disable Bit, helped in practical situations?
Blame the machine or blame the programmer? You can write x86 code without buffer overflows, period. That you can be more sloppy on other architectures and not get overflows seems silly. Like "everyone should drive Volvos cause they are safer."
Lots of things can be laid at the feet of x86 architecture, but not that it seduces programmers into writing code with buffer overflows.
"Eve of Destruction", it's not just for old hippies anymore...
The real disadvantage of x86 over a RISC architecture like SPARC is that it doesn't have page protections (not to be confused with real mode segmentation which essentially disables the protected mode i386 MMU) where pages containing data and code are marked differently, so data pages are non-executable. sparcv9 implements a non-executable user stack per default, whereas it's a configurable option for sparcv8 binaries.
This has all changed with x86-64/AMD64/EM64T/x64/WHATEVER, which has brought a noexec bit to memory pages and allows hardware buffer overflow protection similar to SPARC. This still isn't a silver bullet for buffer overflows, but it's certainly better than nothing.
Linux, BSD, and other *nix systems are reasonably well protected through the design of the system and the widespread use of common server programs, which are checked and re-checked for these problems by a variety of people and organizations. Also, GCC provides ProPolice, which can help lock things down a bit more. I think this particular problem mostly applies to systems running Windows.
Microsoft's business problem in this regard is that they have no control over the applications running in Windows, and they provide a default Windows install that is quite open and vulnerable. Locking down the ports and getting rid of the most dain-bramaged policies in Windows is only one part of the solution. Vulnerabilities in application programs can still be used to break into these systems, and Microsoft will ultimately be blamed.
Perhaps the best thing Microsoft can do is integrate something like ProPolice into the C and C++ libraries used to compile programs for Windows. This would make a big difference in protecting the stack of running programs that are not designed with security as a priority.
If x86 really is less secure by nature, it probably wouldn't hurt if they'd put their virtualization engine (similar in function to VMware but not even half as good) right into the core OS. Under such a design, only the Windows kernel would run directly on the processor; the rest of the operating system and all of the application programs would run with the same x86 instruction set, but through the virtualization engine. There, checks could be made to prevent the most common vulnerabilities of the x86 processor from being utilized.
The stack direction has nothing to do with security. You can still have stack protection running up or down stacks. Once you have a reasonable MMU, all further problems are due to software design.
Engineering is the art of compromise.
But why I ask is the OS allowing one process to overwrite memory of another.
It doesn't--that's not what an overflow attack is.
An overflow attack causes a process to overwrite its _own_ memory, with instructions carefully chosen by the attacker. The attacker's code is executed by the attacked process itself.
Think of it like the old Bart Simpson gag of calling up Moe's and asking for "Mr. Butz, first name Seymour". If you can get Moe (the process under attack) to repeat what you say (the attack payload), he's as good as yours.
Xix.
"Everything is adjustable, provided you have the right tools"
http://cvs.openbsd.org/papers/auug04/
Theo talks about how OpenBSD uses various available processor features to increase system attack resilience, w/minimal performance impact. The design choices made for architectures with differing degrees of per-page protection are presented. The concepts are not at all OpenBSD-specific, although the implementation discussed is, of course, OpenBSD.