Linux Kernel 2.6 Local Root Exploit
aquatix writes "This local root exploit (Debian, Ubuntu) seems to work everywhere I try it, as long as it's a Linux kernel version 2.6.17 to 2.6.24.1. If you don't trust your users (which you shouldn't), better compile a new kernel without vmsplice." Here is millw0rm's proof-of-concept code.
I don't think I'm the first of us to say "Ah shit".
On the other hand though this is the beauty of open source. The problem is now known so I'm sure a fix is already on the way.
I never get used to these constant resurrections
And the next sound you shall hear are millions of nerds rushing into their offices to compile a new kernel on a sunday afternoon... along with the millions of cell phones ringing as the bosses read this...
Karma Whoring for Fun and Profit.
I strongly suspect this code doesn't do what it says on the tin.
Phew, lucky I run MS Windows then !!
This is not an universal problem. It only occurs for those kernels with a specific function compiled in that most installations won't need, and which halfway decent sysadmins won't have as part of the kernel anyhow when they don't need it.
Yet another good example of why you shouldn't hire the sysadmins who blindly use what the vendors ship, but security and performance minded sysadmins who reduce installations to what's actually needed.
"But see, Linux sucks! It has holes just like Windows does!"
The difference is that we know about this hole, and can now fix it - I'm just going to bed, and it will no doubt be fixed by the time I wake up. How many Windows security issues are known that haven't been fixed?
"Oh man, this is why Linux is great! We can find holes, and fix them, like, immediately!"
Yes, that's a strength of Linux. What I want to know is, what steps will be taken to ensure that bugs of this type - whatever they might be - don't crop up again? One advantage that a large paid organization can have is strict testing requirements - I'm honestly not sure if I believe the Linux kernel is held to the strong standards that a commercial kernel theoretically could be.
The existence of this bug is a failure on Linux's part. There's no way to get around that. Many mistakes were made, from the original code or design decision that caused this bug all the way up to it not being found until now. The bug will be fixed rapidly - but the process that let this bug be released needs to be looked at, casually at the very least, to figure out if there's a way to stop this class of error from ever happening again. (Whatever class of error it ends up being - I don't pretend to know.)
Breaking Into the Industry - A development log about starting a game studio.
Just tested on Suse x86_64 10.3, ran as local user and it dropped me into root.
Linux opteron 2.6.22.16-0.2-default #1 SMP 2008/02/01 19:36:55 UTC x86_64 x86_64 x86_64 GNU/Linux
Nope, all you need is remote access to a local user account via ssh or something. Many users use weak passwords. Now you won't have to guess the root password.
Yes, I just verified the exploit on Linux 2.6.17.13 (Slackware 11.0) and Linux 2.6.21.5 (Slackware 12.0) and it works as advertised.
The proof-of-concept code only supports x86 and x86_64. Does that mean other architectures are immune?
Inaccurate. It does require shell access, but it does not require it to be physically local.
A 'local root exploit' only means that you have to have a shell of some kind first. This can include an SSH shell account. This can also include any kind of non-root shell exploit.
Say that you can exploit some webapp to get a shell as wwwrun/apache/www. That combined with a local root exploit to get root. It doesn't even need to be a DIRECT shell exploit. Perhaps your hack/program opens up a port with telnet listening.
Thus all 'local root exploits' are potential remote exploits, if we allow for chaining. Chaining can be used by anyone who isn't just a script kiddie. Hell, you could probably make an auto-rooter that will chain the exploits.
There are some pretty funny comments in the source code, regrettably, most people won't understand them. Hell, as a Czech, I *am* probably supposed to understand them, if it were not for the obscure north-eastern dialect of Czech that all the rest of our country finds hilarious (and incomprehensible at the same time).
..." [last for four words utterly incomprehensible :)]
:)) makes me think that had drunk quite a bit before he wrote these gems. Pity that I don't have a good dictionary of spicy English. I'm just rolling on the floor and seriously laughing. :) Oh, and the exploit works, which is not that *funny*.
"Dovalim z knajpy a cumim ze Wojta zas nema co robit, kura." == something like "Just returned from the pub and saw that Wojta [a machine? Or a person? Unclear...] has nothing to do." [The last word might be a Czech expletive with a typo...?]
"Gizdi, tutaj mate cosyk na hrani, kym aj totok vykeca." == something like "Here's something for you to play with, boys,
"Stejnak je to stare jak cyp a aj jakesyk rozbite." == "Anyway, it's old as hell and somehow broken anyway"
The style (no way am I able to render *this* in English
Ezekiel 23:20
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=464953
The workaround posted in a follow-up in that thread works. I had a few vulnerable (tested) machines that I cannot reboot even if a patched kernel is released in the near future. I tried that fix, then tried the exploit again. The exploit no longer worked after using the fix (workaround).
Those machines were debian x64.
Ubuntu kernels do not appear to have vmsplice enabled by default.
Uh oh. There's another link, (not the one from the /. article) that worked on my machine:
http://www.milw0rm.com/exploits/5093
Notice the original article links to 5092.
FLR
Upstream patch for the vulnerability tickled by that specific exploit is here
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=712a30e63c8066ed84385b12edbfb804f49cbc44
Red Hat tracking bug (Enterprise Linux 5 is affected, but 4,3, and 2.1 are not)
https://bugzilla.redhat.com/show_bug.cgi?id=432251
Fedora tracking bug
https://bugzilla.redhat.com/show_bug.cgi?id=432229
Well, if you are running machines that are designed to be enterprise class, it isn't a problem. Remote console is standard on enterprise class hardware.
NTFS has had that for a while now.
Suggest you check out Windows System Resource Manager
The real problem here seems to be not Windows, but your ignorance about Windows.
Well, I can tell you that SELinux (enforcing, targeted) on Fedora 8 was no help in preventing this exploit. Does "strict" make a difference?
the growth in cynicism and rebellion has not been without cause
Pardon me for the rookie question - but can anyone tell us which kernel config option enables this so-called vmsplice? I'm no even clear on what its for... if its something I don't need can I disable it through menuconfig or is it something that I'll need a patch to disable?
The given exploit prints pointers using "%lx". That's wrong, and on x86-64 it will break (pointers are 8 bytes, longs are 4 bytes).
Every instance of "0x%lx" needs to be replaced by "%p".
The moral of this story is: Always use gcc -Wall and fraggin' pay attention to the warnings.
Ooh, moderator points! Five more idjits go to Minus One Hell!
Delendae sunt RIAA, MPAA et Windoze
No it doesn't.
You know, there is a difference between trolling and pointing out the flaws in your reasoning. Just saying.
It seems to me that slashdot's system for filtering submissions is doing a very poor job these days with stories about security bugs.
Within the last day or two, we've had the following:
This is really getting to be a Boy Who Cried Wolf thing.
Find free books.
I get the impression the 'custom kernel' brigade have never worked on a corporate environment.
Out there in the real world you use RHEL because it has paid support. You then use hardware certified by Redhat and use their packages (btw. RHEL doesn't appear to be vulnerable - you get an mmap failure trying to run the exploit).
If your oracle server goes titsup and oracle refuse to support you because although you're running on the supported RHEL your cowboy IT guy recompiled the kernel and broke it.. that costs money (potentially millions if the downtime is extended). And time. And stress. And the IT guy's job, and his job reference, and, we would hope, his career.
I did a "grep -i" on the term "splice" in my /usr/src/linux/.config and it came up empty.
I did not include KVM support in my kernel on purpose.
As this http://bugs.debian.org/cgi-bin/bugreport.cgi?msg=9;filename=patch;att=1;bug=464953 patch points out, it's in the general fs splice.c code, so I think it is more serious than I originally had thought.
For some reason, (if someone can substantiate this I would appreciate it) I could get neither code to work on a CentOS 4.6 machine setup as a server).
I'm buying into the idea that it may be based (a little) on kernel config options, but an official patch would be bet
FLR
The poster who said that Ubuntu kernels are not affected was incorrect, at least partially. The exploit code works as advertised on my Ubuntu machines, both of which are running 7.10 with the latest generic kernel image.
BTW: Has anyone figured out if there is an option you can disable in make menuconfig that removes vmsplice(), or is it integral to the kernel?
Vmsplice is part of the core kernel, it is not a configuration option. It is used all over the place.
Interested in open source engine management for your Subaru?
The problem is, even though you're the sole user, that if other exploits appear they could piggyback this to escalate from, say, access as www-user to access as root. Got any http services on that box for your own convenience, and any of those use PHP? Based on past experiences, this might hose you. Got SSH on there? Again, based on past experiences, this might hose you. Sendmail and some kind of mailscanning? Again, this might hose you.
It's not just a matter of whether or not you trust your users - it's also a matter of whether or not you trust anyone who attempts to exploit some other service your box offers to not try for root access once they get in. "Please, Mr Blackhat, you've gained access to my box, but please don't elevate that to root!" sounds more than a little naieve, and even a little stupid, but that's exactly what people who leave a whole lot of locally exploitable vulnerabilities on their boxes are saying. By not leaving this kind of thing laying around, you are making it a little bit more difficult for anyone who does manage to gain access to your box to gain full access to it.
Security is all about healthy paranoia, and a belt AND braces AND duct tape approach can pay dividends.
Am I personally worried about this? On my work machine and servers I administer, hell yeah - always on, always connected, running various things that in the past have had vulnerabilities - of course I am, I'd be stupid not to be. At home (dial-up, behind a firewall with NAT, nothing much in the way of services, turned off most of the time even though I don't usually bother turning off my WEP-protected wireless access point), not so much - and not just because the only accounts are held by me. I don't broadcast the SSID, I have a couple of neighbors with no security on their broadband-connected wireless access points, and I don't run an awful lot in the way of remote services when I do have my home machines running. If I had broadband at home and a machine that was running anything that was remotely accessible, or if I didn't have a vertiable smorgasbord of less security-conscious neighbours - I'd fix this at home in a heartbeat.
Thankfully, nobody runs Linux on enterprise-class hardware.
"Remember when the U.S. had a drug problem, and then we declared a War On Drugs, and now you can't buy drugs anymore?"
vmsplice exploit fix
Have you got your LWN subscription yet?
...I have a question for you. I 100% agree this is an advantage of open-source than closed-source software will never have, ever. You've got me on that one, but my immediate thought was "ok, how much would I like to change my own kernel in production systems? About 0% thank-you-very-much".
I mean, hacking stuff in and out of a production system kernel; surely that's a process that would require months of intensive regression testing, etc, etc? I mean, I doubt there are people that know the kernel well enough to do such changes for their own systems, but really, what percentage of you guys honestly and confidently can say "Yeah, let me just fix that for us" knowing your job is on the line if your systems crash around you.
This isn't a troll, this is an honest question.
throw new NoSignatureException();
This local root exploit is very likely to be the one used to infect servers reference in previous Slashdot article Mystery Malware Affecting Linux/Apache Web Servers.
It seems pretty clear that people are using other remote vulnerabilities to gain local user access and then using this local root exploit to install their "malware".
Get those boxes updated as quickly as possible, folks!