Slashdot Mirror
Wu-ftpd Remote Root Hole
Ademar writes: "A remote exploitable vulnerability was found in wu_ftp, which is distributed in all major distros. The CERT has a (private) list to coordinate this kind of disclosure so vendors can release updates together, but RH broke the schedule and released their advisory first. You can see the full advisory from securityfocus in bugtraq, but here is a quote: "This vulnerability was initially scheduled for public release on December 3, 2001. Red Hat pre-emptively released an advisory on November 27, 2001. As a result, other vendors may not yet have fixes available."" CNET has a story about this too.
Would have been nice to give the maintainers on a few other distro's time to close the hole before broadcasting this to the script kiddies
Until 5 mins ago I was a beleiver in complete disclosure,
But with 6 wu-ftpd boxes to admin I'm not so sure any more.
Hope I see a fix today.
'There is a Light that never goes out.'
You all bashed Microsoft the last time around for not immediately and publicly notifying users of an exploit, they, prefering instead to ready a fix before the exploit was common knowledge.
So, once again use an occasion such as this to resoundingly denounce the fact the CERT, and major Linux distros other than Red Hat, have chosen to do the essentially same.
I suspect that the complaints of this type of behavior will be much less in the case of CERT, since Microsoft's disclosure policies simply allow slashdotters to take pot shots at MS, but we'll see...The shoe's on the other foot this time.
I'm somewhat surprised--but either way it brings the unresolved question of disclosure bubbling to the froth again.
Plus, its pretty bad since whenever micorosoft gets something like this, people get pissed off if they take more then a weekend on it. Here, they took almost a week longer then RedHat, makes you wonder how long this sploit was in hacker circles, and how long the distros knew about it. Whatever happened to the claims of fast reaction in the opensource industry vs. old-skool business?
This isn't a troll, but an honest question - what tookem so long, and why didn't they just throw it open to end-users to protect themselves (like closing down ftps in worst-case) like is supposed to be standard practice?
item: the version of wu-ftpd that rh released was a pre-release from cvs. they changed the version number. this bug was fixed in cvs months ago.
item: the securityfocus vuln-help people are supposed to help coordinate vendors & the software maintainers. they sent notification of the bug to the wrong address, so the wu-ftpd developers weren't even aware that there was a bug present until the day the rh advisory went out.
item: there was supposed to be a coordinated advisory put out on dec. 3rd. rh preempted that, causing this nasty confusion.
greg lundberg posted a big explanation of what went on to several mailing lists... it should be on the wuftpd-questions archive, but i don't see it there yet.
also, see the news item at securityfocus about this.
Now you guys are criticizing Red Hat for releasing information too quickly?!
Make up your minds. Either it is a Good Thing to release this sort of information to the public or not. IMO, if CERT is withholding information to the public that just gives a wiley cracker that much extra lead time to perform exploits. Whereas if the info was just released in the first place, at least people could turn their FTP servers yet, or switch to something like pure-ftp, which has yet to be cracked.
I agree with Red Hat on this one. They did people a favor by releasing the information.
No, Thursday's out. How about never - is never good for you?
I looked through the source of Wu-FTPd some time ago, when I was interested in adding support for an encrypted form of FTP proposed in a recent RFC (the protocol never caught on). What I found scared me. Most of the server is one humungous 8000-line C source file which appears to do pretty much everything.
Having quite a bit of experience with the FTP protocol, I expected to immediately understand what was going on, but at first glance, this code baffled me. It's full of pointer arithmetic and chains of if-statements performing mysterious, undecipherable operations on fixed-length arrays. It's not divided into clear levels of abstraction and I had difficulty telling what most functions were supposed to do, let alone what they actually did.
Anyway, I immediately gave up any thought of adding any new features to this godawful mess. Considering all the weird cruft that goes on in that code, it's no surprise to me that people are constantly finding new security holes in it. There are other featureful FTP servers out there; it's hard to see why distributions continue to include a bug-ridden program like Wu-FTPd as default in their distributions.
Ok, so what level of security on someone's box makes them no longer a moron? Is there a canonical list of things I must do to secure a box so that I am no longer a moron? To be honest, I run my own box for personal use, and learning anything more than basic security takes more time than it's worth. Please let me know where I can go to learn what it takes to build a secure box as defined by non-moron security experts.
LS
There is a fine line between being a cultivated citizen and being someone else's crop. - A. J. Patrick Liszkie
This shows you what daemons are auto-started: /sbin/chkconfig --list | grep :on
/sbin/chkconfig --del THING_YOU_DONT_WANT
/etc/ssh2/ssh2d),
#
man NAME_OF_THING_YOU_DONT_KNOW_WHAT_IT_IS
#
get the latest nmap from freshmeat.net.
do this:
# nmap -sS -P0 YOURIPORHOSTNAME
do you see any ports you weren't expecting?
Turn off the services!
Install portsentry + ipchains on a firewall,
or if you don't have more than one box, your
own box! Set portsentry to listen on bind to
catch a lot of automated attackes from a RH6.2
bug. Move your ssh (2.X or greater!!) daemon
to a non-standard port (edit
then set the normal ssh port as a portsentry
tripwire.
Very active attacks right now:
Bind
ftp
finger
telnet
ssh
port 59 (anyone know wtf that is?)
wu-ftpd had an *earlier* vulnerability that
was causing increased scan activity too!
Subscribe to the cert.org mailing list, and
"grep for linux".
you have to take an active role and pay attention
to all security bulletins out there, because
you will literally be attacked within an hour
of bringing up a new DSL/T1 server anywhere in
the wild. I've seen portscans on newly installed
lines in less than 5 minutes!
Sure they put out this advisory before it became knowledge to the NEWS organizations, but the "bad guy" groups have known about this for quite some time. Case in point, my brother wanted to show me some large home-movie mpegs (much to large to email to me), so he gave me an account on his box to ftp them from. Somehow the password that he gave me wasn't right (he must typed it with the caps lock on), so I couldn't get into his machine. He was already asleep by that time, so I couldn't call him up to change it, so just for kicks, I thought it might be fun to see if there was any way to break in. Sure enough, a few well-formed google searches, and I had pages that not only "discussed" this vulnerability, but had tools and scripts (including compiled Windows 9x GUIs for the lazy script kiddie) for download. They were wonderfully useful, and they *worked*.
So, the root of the situation is: 1) Anyone who did NOT know about this hole had been vulnerable LONG before the posting. 2) When told about the hole, but without a patch, any of those admins could then take whatever steps would be needed to keep thier server secure (even shutting ftp down if it came to that).
RedHat was right.
"Your superior intellect is no match for our puny weapons!"
Now, RedHat maybe shouldn't have ever made this "agreement" to pospone patches. Maybe they noticed that people were already making use of this not-so-secret-to-black-hats bug. Or, maybe it was just a mistake... I don't know. I'm just glad I don't have a public wu-ftp server to deal with.
-- these are only opinions and they might not be mine.
HTTP really is all that.
HTTP/1.1 supports, among other things, file resuming via a standardized header (Range:) and pipelining (whereas FTP's control port+data port means n+1 TCP connections). HTTP can give you a file compressed the way you want it - and in the language you asked for - without filename hacks. HTTP's If-Modified-Since: header makes it more cacheable. In addition, most HTTP server implementations are more flexible - they can authenticate against things other than the local account database, and there is a widely implemented standard for HTTP over SSL - HTTPS. CGI is also more pervasive and useful than SITE EXEC.
Let FTP die the death it has so long deserved.
Learn more about security before offering advice:
k .h tml
d vi sory-1223.html
Breaking chroot jail:
http://www.bpfh.net/simes/computing/chroot-brea
Proftpd globbing bug:
http://www.linuxsecurity.com/advisories/other_a
maru
For uploads, FTP is still probably better, if only because nobody seems to use the HTTP PUT command.
For downloads, though ...
What are the advantages to FTP for downloads (especially anonymous, but also authenticated)? I honestly can't think of any ATM.
"How can you claim that you are anti-crack, while still writing a window manager?" — Metacity README
Check out this thread on the wuftpd-questions list:
m =100698257011540&w=2
http://marc.theaimsgroup.com/?l=wuftpd-questions&
/. is irrelevant.
I know that we sometimes live with legacy code; fair enough. But I claim that it is entirely inappropriate to write security-critical internet daemons in C!
There are lots of people here claiming that this is caused by sloppy or inexperienced programmers. I think that this is bullshit. Are the authors of wu_ftpd bad programmers? BIND? IIS? perl? telnetd? quake 3 arena? sshd? All of these have had remote overflow (or related) exploits. There are hundreds more... Have you personally ever written a multi-thousand-line network daemon that you know is buffer overflow free? How do you know?
Here is what I say: C the language makes it easy to make the kind of mistake that leads to a remotely exploitable buffer overflow. It is almost as if the language is designed to enable this behavior. According to CERT and others, buffer overflows (and related format-string vulnerabilities, also endemic to C) are the most common source of security holes in UNIX applications (On win32, they are second only to Outlook attachments).
There are only two reasons I can imagine that people would reasonably use C:
Low-level Hardware Access - Fair enough. There are not really any good alternatives now. However, network applications do not need to do low-level hardware access at all.
Raw Speed - Though I believe that other languages are very near to C in performance (http://www.bagley.org/~doug/shootout/craps.shtml) , conventional wisdom says that if you want ultimate speed, use C. However, network applications are not typically CPU-bound, they are network bound. ESPECIALLY FOR THE HOME USER, with a 1.5ghz PC and 5 users per day, this argument is totally silly. Outside the enterprise (where hopefully people can custom tune their software and have people devoted to keeping it secure), there's no reason to need C's speed in a network daemon.
IN A NETWORK APP, SECURITY (SAFETY) IS CRITICAL. That means that all network apps should be written in a language with machine-checked safety. This might mean Java for people who need it to feel like C. (Note that there are several good native code compilers for java, and it has reasonable network support.) In these kinds of languages, buffer overflows and format string vulnerabilities are automatically impossible. Personally, I prefer a more efficient language with stronger safety guarantees: SML. (Ocaml might suit the slashdot audience better) In fact, at the time of the last wu_ftpd remote root exploit, I decided that it was time for me to rewrite my ftp daemon in SML. It took me only 1 weekend to get it working, by myself. It does not support every feature of FTP (especially obsolete things and dubious "features" like SITE EXEC), though it supports plenty for say, the average linux desktop user. Writing code in a modern, high-level language has other benefits too: it is only about 3000 lines, including library code that I wrote to implement MD5 passwords and various other things that I plan to use in other daemons (the core ftp server is only 850 lines). Compare this to wu_ftpd (8000+ lines) and the PAM MD5 password implementation (200 lines). Most importantly, I know that by using a safe language that I have a 100% buffer overflow free daemon. Thus, I can spend more time looking over the code for more subtle security problems, such as possibilities for Denial of Service attacks. (I didn't do much of this, actually, though it is not vulnerable to the ls globbing attack, SITE EXEC, or PAM authentication bugs that have been in other ftp servers.)
If you think this sounds good, you can get my FTP server here and an ML compiler here . (It is just a proof of concept, so don't get too excited!) But what I would rather you do is just listen to my advice, and demand better from your software manufacturer! Linux distributions that want to be secure should be rewriting this kind of software in some modern safe language. It is easy to do, and the results are worthwhile.