/* 
:: dynamicscan.c
:: DynamicScan Port Scanner v1.2.
:: Created by Dr4g, Founder of DynamicHell.
*/

#include <stdio.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <signal.h>
#include <netdb.h>
#include <sys/time.h>
#include <unistd.h>

struct sockaddr_in client; 
struct hostent *he; 
struct servent *se; 

int scan(int port);
int usage();
int banner();
void timeout(int);

int sockfd;

int main(int argc, char *argv[]) {

	int start_port,end_port;
        if(argc < 3) {  
                usage();
                exit(1);
        }
	else if (argc == 3 ) {
		banner();
		start_port=atoi(argv[2]);
		end_port=atoi(argv[2]);
	}			
	else {
		banner(); 
	        start_port=atoi(argv[2]);
	        end_port=atoi(argv[3]);
	        if(end_port<start_port) {
        	        printf("Error: End port cannot be less than start port");
                	exit(1);
		}
        }
 
        /* ----- Check Hostname is correct ----- */
	/* ------------------------------------- */
        if((he=gethostbyname(argv[1]))==NULL){
                printf("Can't Resolve Hostname\n\n");
                exit(1);
        }
        

	/* ------- Set signal SIGALRM --------------- */
	/* ----- Set Signal Handler to timeout() -----*/
	/* ------------------------------------------ */
	signal (SIGALRM, &timeout);
	

	/* -------- File Handling -------- */
	/* ------------------------------- */
	FILE *fp;
        fp = fopen("dslog.txt","a+");
	

        /* ------ Get Time ------- */
        /* ----------------------- */
        time_t curtime,fin_time;
        time(&curtime);
        printf("Scanning host on; %s\n",ctime(&curtime));
         

        fprintf(fp,"\nScanned Host; %s\n-------------------------\n",(argv[1]));   
	fprintf(fp,"Time of Scan %s\n",ctime(&curtime));

	for(start_port;start_port<=end_port;start_port++) {

                /* --------- Check if Scan() Returns 1; Port Open -------- */
		/* ------------------------------------------------------- */
                if(scan(start_port)) { 
                        se=getservbyport(htons(start_port),"tcp");
                        printf("Port %d is Open;  Running Service %s\n",start_port,(se == NULL)?"Unknown":se->s_name);
			fprintf(fp,"Port %d is Open;  Running Service %s\n",start_port,(se == NULL)?"Unknown":se->s_name);
                }
                else{
                        /* if you remove this commented out line,
                        it will print closed ports also, meaning you know what port its on.
                        (was used for debugging) */
      			//printf("Port %d is Closed",start_port);
                } 
	
        }

	time(&fin_time);
	printf("\nScan Finished at %s \n",ctime(&fin_time));
	fprintf(fp,"End of Scan at %s\n-------------------\n",ctime(&fin_time));
	fclose(fp);
        return 0;
}


int scan(port) {

	/* ---------- Creating Our Socket ---------- */
	/* ----------------------------------------- */
        if((sockfd=socket(AF_INET,SOCK_STREAM,0)) < 0) {
               printf("Error Creating Socket");
	       printf("port: %d\n",port);
               return 0;
	}
	else {
		client.sin_family=AF_INET; 
		client.sin_port=htons(port);
		client.sin_addr=*((struct in_addr *)he->h_addr); 
		memset(&(client.sin_zero), '\0', 8); 

	/* ------------ Init alarm for 2 secs and try to connect ------------ */
	/* ------------------------------------------------------------------ */
		alarm(2);
		if(connect(sockfd,(struct sockaddr *)&client, sizeof(client))==-1) {
			alarm(0);
			close(sockfd);
			return 0;
		}
		alarm(0);
		close(sockfd);

	return 1;
	}
}

void timeout (int signum)
{
	/* -------- Handler for Timeout. ---- */
	/* -------- Close the socket -------- */
        close(sockfd);
} 


int banner() {
	printf(" _____                              _       _____  \n");
	printf("|  __ \\                            (_)     / ____|\n");
	printf("| |  | |_   _ _ __   __ _ _ __ ___  _  ___| (___   ___ __  _ __  \n");
	printf("| |  | | | | | '_ \\ / _` | '_ ` _ \\| |/ __|\\___ \\ / __/ _` | '_ \\ \n");
	printf("| |__| | |_| | | | | (_| | | | | | | | (__ ____) | (_| (_| | | | |\n");
	printf("|_____/ \\__, |_| |_|\\__,_|_| |_| |_|_|\\___|_____/ \\___\\__,_|_| |_|\n");
	printf("         __/ |   Version 1.2 | DynamicHell.com\n");
	printf("        |___/\n\n");
	return 0;
}
int usage() {
        printf("Incorrect Parameters !\nUsage: ./dynamicscan <HOST> <START PORT> <END PORT> <-- Optional\n\nDynamicScan v1.2\n");
	return 0;
}