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On Fri, 2006-03-17 at 10:43 -0800, Linus Torvalds wrote: > > On Fri, 17 Mar 2006, Steven Rostedt wrote: > > > > So I guess if you need to debug a system binary, you need it readable. > > But I guess that can also be a security problem, and having system > > binaries not readable, might make you system a little more secure. > > NOTE! The kernel does not guarantee that you can't read execute-only > binaries. > > In particular, it's fairly easy to create a shared library that replaces a > system library (LD_LIBRARY_PATH) and then just dumps out the binary image. > > So anybody who thinks that 0111 permissions are somehow "more secure" than > 0755 is just setting himself up for disappointment. You're much better > off just having all binaries be 0755 and getting the security through > other means. > > Basically, you should think of the "executable" bit as a way to say "this > file is appropriate for execve(), and btw, that does imply that we'll need > to read it into memory too". You should _not_ depend on it for security, > although dropping the readability bits will mean that certain -trivial- > programs won't be able to read it. > > For example, making a binary unreadable is a perfectly good way to stop a > web browser or other interface from exporting it outside the machine: but > it's not so much about security as about _accidental_ leaking. > > So from a security standpoint, you're much better off thinking "executable > means readable", than lulling yourself into some false sense of security. Yep, I agree whole heartily. I should have stressed the "little" part in the above quote. "might make your system a __little__ more secure.". I didn't want to get into the details that you described, but you are entirely right. I just wanted to note that it does stop someone at some level. But it's more of an annoyance to someone with a little more experience in hacking into a computer. But since it does stop some amateur's does give it some weight to actually do it. But it is far from actually protecting yourself from a more devious cracker. But thanks for the critical disclaimer. -- Steve - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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