January 3, 1999
Corruptio Optimi Pessima
"corruption of the best is worst of all"
Vulnerability: Automountd
Operating System: SUN Solaris
Versions affected: 2.5, 2.5.1, 2.6, 2.7 (X86 and SPARC architectures)
[ Rant ---------------------------------------------------------- ----
You pay for this? Why is it vendors can't get the hint? Network
users demand secure software, not poor attempts at patching
longstanding holes in the current revisions. Sun was warned about
this bug years ago, and over time all they could come up with is a
single broken patch that reminds us of the first Microsoft fix for
the port 139 OOB attack. Why does it take vendors like Sun over
three MONTHS to patch this kind of hole?
They claim that it takes that long because of the level of testing
they must put the software through. Right. So not only do they
supply a broken patch, they test it for three months and never
notice it is still vulnerable, then release it to their paying
customers.
You pay for this? How many security vendors knew about this and
said nothing? Why did CERT never report this? Why have hackers
been passing these exploits around for two years? Why didn't the
ueber-spies of the ICSA get their hands on this and report it?
Why didn't Sun's own "security analysis team" of 70 people find
this bug (or any others)? Could it be job security? We think so.
---- --------------------------------------------------------------- ]
[ Details ------------------------------------------------------- ----
Back in 1995, a vulnerability was discovered and a new world of
buggy software born. This particular bug, would be conceived when
Sun Microsystems made the foolish decision to ship Solaris 2.5 to
customers.
Since then, it has been a downhill roller coaster for the boys and
girls at SUN. Now, not only is 2.5 affected, but 2.5.1 stock, 2.5.1
patched, 2.6 and 2.7 are all affected as well.
This bug is particularly important, because it shows the
incompetence of Sun Microsystems. Not only do they sit on patching
bugs for months at a time, they cant even patch bugs right!
When exploit code for the local automountd problem was leaked a few
YEARS ago, SUN developed a patch and labeled it #104654-05.
However, intrestingly enough, even after the patch was released,
this bug could still be exploited quite trivially.
What SUN decided todo, was remove the 'popen' call and put in its
place an 'execve' call. Absolutely brilliant. Did they forget
that the variable holding the program and arguments to be execued
could still be set by issuing a AUTOFS_MOUNT call to automountd?
Or, is this a case of job security by one of Sun's engineers?
We certainly feel it is the latter.
Either way, not only is this bug local, but it is remote too!
And, not only is it remote, but it is started by default as well!
Yes, thats right boys and girls, you can now execute any program
you like on any default installation of SUN remotely! When
exploiting this vulnerability, be sure to send SUN your warmest
compliments.
Now, getting back to the bug at hand, a few things have to be
established before this can be exploited.
First of all, to remotely exploit this bug, it becomes two-pronged.
Meaning, we are now going to introduce another remote bug in the
SUN Solaris operating system that when combined with the previous,
create a lethal combination.
This new bug, located in rpc.statd which is also started by default
(imagine that!), allows for remote packets to be bounced to the
local Operating System.
Looking back at the details of automountd, we remember that it
cannot accept packets on UDP or TCP protocols. But, it can accept
packets on the TLI protocol, which rpc.statd happens to forward to,
allowing us to remotely execute commands by sending our packets to
rpc.statd.
So, with all this in mind, if we send two RPC packets to rpc.statd
on Solaris 2.5, 2.5.1 stock, 2.5.1 patched, 2.6, or 2.7, with the
SM_MON and SM_NOTIFY commands, rpc.statd will happily forward the
packet on to the local operating system's automountd daemon.
Variables we will have to setup will be the following:
struct mon monr;
struct status stat;
memset(&monr, 0, sizeof(struct mon));
monr.mon_id.my_id.my_name = cache;
monr.mon_id.my_id.my_prog = (unsigned long)AUTOFS_PROG;
monr.mon_id.my_id.my_proc = (unsigned long)AUTOFS_MOUNT;
mon_id.my_id.my_name will be our cache, which we will be using to
tell rpc.statd where to forward the packets to.
The cache of the remote system can be found by establishing a
connection to port 23, or port 21 of the system. The cache will
usually appear inside parentheseis, and will be the hostname of the
machine.
Another example of obtaining the cache, would be to lookup the ip
address of the machine and use the hostname that comes back.
For example, for pathetic.sun.com, you could try 'pathetic' or
'pathetic.sun.com', and it will be a pretty safe bet that you will
pick the correct hostname.
mon_id.my_id.my_prog will be the variable AUTOFS_PROG telling
rpc.statd which RPC service to connect to.
mon_id.my_id.my_proc will be the variable AUTOFS_MOUNT telling
rpc.statd to tell automountd that we want a AUTOFS_MOUNT request.
Further variables to setup:
monr.mon_id.my_id.my_vers = 1; /* For Solaris 2.5, 2.5.1 */
or
monr.mon_id.my_id.my_vers = 2; /* For Solaris 2.6, and 2.7 */
monr.mon_id.mon_name = command;
stat.mon_name = command;
monr.mon_id.mon_name and stat.mon_name will both contain the
program to execute on the remote system.
Now, with those variables setup, we can send off our RPC packets
to the remote system.
However, to complicate things more, we must modify our tekneeq of
exploiting this bug, for it to succeed on 2.6 and 2.7.
Because SUN implements a new function called SMHASH in rpc.statd on
Solaris 2.6 and 2.7, we will now have to involve DNS spoofing
to acomplish executing our command.
Because of the way SMHASH works and the way RPC arguments are
encoded, our command is what SMHASH attempts to lookup in its
address tables once rpc.statd receives our packet.
If SMHASH cannot detect if our command is a valid address, it will
not forward the packet. However, if we DNS spoof our command off
the Primary and Secondary nameservers of the remote system, SMHASH
will return true for finding the command as an address and our
packet will be forwarded.
If you wish to test this bug without DNS spoofing, you can also
modify the /etc/hosts file on the Solaris system and put in the
command you want to execute (without arguments) as a hostname
with an ip address, and it will accomplish the same affect.
For the actual exploit code to do this, I will let the reader go on
to the next section to find it.
Examples:
If pathetic.sun.com were a Solaris 2.7 machine with pathetic
as its hostname, and a vulnerable Primary name server,
an exploit attempt would look like this:
Execute commands to spoof reboot off Primary NS here
./amountdexp pathetic.sun.com pathetic reboot 1
If pathetic.sun.com were a Solaris 2.5.1 machine with pathetic
as its hostname, an exploit attempt would look like this:
./amountdexp pathetic.sun.com pathetic reboot 0
---- --------------------------------------------------------------- ]
[ Exploit ------------------------------------------------------- ----
Exploit code for this vulnerability can be easily obtained from the
following URL: http://www.attrition.org/hosted/cop/index.html
---- --------------------------------------------------------------- ]
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