NETWORKING - Hacking: The Art of Exploitation - page 212

reader@hacking:~/booksrc $ gcc -o host_lookup host_lookup.c
reader@hacking:~/booksrc $ ./host_lookup www.internic.net
www.internic.net has address 208.77.188.101
reader@hacking:~/booksrc $ ./host_lookup www.google.com
www.google.com has address 74.125.19.103
reader@hacking:~/booksrc $
Using socket functions to build on this, creating a webserver identification
program isn't that difficult.
webserver_id.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include "hacking.h"
#include "hacking-network.h"
int main(int argc, char *argv[]) {
int sockfd;
struct hostent *host_info;
struct sockaddr_in target_addr;
unsigned char buffer[4096];
if(argc < 2) {
printf("Usage: %s <hostname>\n", argv[0]);
exit(1);
}
if((host_info = gethostbyname(argv[1])) == NULL)
fatal("looking up hostname");
if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1)
fatal("in socket");
target_addr.sin_family = AF_INET;
target_addr.sin_port = htons(80);
target_addr.sin_addr = *((struct in_addr *)host_info->h_addr);
memset(&(target_addr.sin_zero), '\0', 8); // Zero the rest of the struct.
if (connect(sockfd, (struct sockaddr *)&target_addr, sizeof(struct sockaddr)) == -1)
fatal("connecting to target server");
send_string(sockfd, "HEAD / HTTP/1.0\r\n\r\n");