Create Simple Port Scanning Program Using C language

Posted by Suraj Singh on June 06, 2018 · 27 mins read
hii readers,




Today, In This Post I am going to share with you, a very simple port scanning program created in C language. To Run This Program, You Just Need Linux and GCC.

This Program is very easy to use and fast. But Please Keep In Mind, This Is only for Educational And Practise Purpose Only.

Basically, Guys To make this program more easy to understand, I had used lots of comments. so,
I am hoping that you all guys will manage to understand the basic concept behind this program.

Hmm, Let's me tell you a bit about the concept behind this program, as we know To make a two side connection, We required two entities. first client and second sever. so, here our basic agenda is to find, open port on the server. So, in simple words, our program will act like a client and will bruteforcelly try to connect to all given port. if the connection gets complete.. means the port is open, otherwise port is close.


Note:

1. These Scripts are Tested In Ubuntu Only.
2. For More Description About Syntax, Use Ubuntu man page.


Port Scanner In C.



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/*
*
* __author__: Suraj Singh Bisht
* surajsinghbisht054@gmail.com
* www.bitforestinfo.com
*
* ============================================================
* Created During C socket practise
* ============================================================
*
* Tested On :
* Linux parrot 4.14.0-parrot13-amd64 #1 SMP Parrot 4.14.13-1parrot13 (2018-01-21) x86_64 GNU/Linux
* gcc (Debian 7.3.0-5) 7.3.0
*
* */

// include header
#include <stdlib.h> // standard library
#include <stdio.h> // Standard Input Output Library
#include <sys/socket.h> // socket header
#include <sys/types.h> // Data types
#include <string.h> // String
#include <netinet/in.h>
#include <arpa/inet.h> //
#include <unistd.h>

#define PORT_EXPRESSION_ITER 11


// Error Report On Screen
void error(char *msg)
{
printf("[Error] %s\n", msg);
printf("[X] Terminating Program...\n");
exit(0);
}

// Data Type
typedef struct list{
int data;
int status;
struct list * next;
} plist;

// append nodes
void listappend(plist *head, int val){
/*
*
* To Append New Node Into Linked List Structure.
*/

plist *tmp;

// starting point
if(head->next == NULL){
tmp = malloc(sizeof(plist));
if (tmp==NULL){
error("Error During Allocating Node For Port Storing List");
}
tmp->data = val;
tmp->next = NULL;
tmp->status = 0;
head->next = tmp;
}
else{
while(head->next!=NULL){
//printf("Checking Node %i\n", head->data);
tmp = head->next;
head = tmp;


//exit(0);
}
tmp = malloc(sizeof(plist));
tmp->data = val;
tmp->next = NULL;
tmp->status = 0;
head->next = tmp;
}
}

void expandlist(plist *head){
/*
*
* This Function is dedicated To explore all node data value Into Terminal.
*
*/
plist *tmp;
while(head->next!=NULL){
printf("Node->Data %i\n", head->data);
tmp = head->next;
head = tmp;


//exit(0);
}
printf("Node->Data %i\n", head->data);

}
void checkport(int sockd, struct sockaddr_in client, int port, char *ip, plist *node){

client.sin_port = htons(port);
client.sin_addr.s_addr = inet_addr(ip);
if(connect(sockd, (struct sockaddr*)&client, sizeof (client))<0){
node->status=0;
printf("Close\n");
}else{
node->status=2;
printf("Open\n");
}


}


void portscanner(plist *p, char *ip){
/*
* This Function is Completely Dedicated To Perform Port scanning
* process and save result into linked list status block
*
*/
int sockd;
plist *tmp;
tmp = p->next;
p = tmp;

/*

struct sockaddr_in {
short sin_family;
u_short sin_port;
struct in_addr sin_addr;
char sin_zero[8];
};

*/
struct sockaddr_in victim;

sockd = socket(AF_INET, SOCK_STREAM, 0);

struct timeval timeout;
timeout.tv_sec = 1; // after 1 seconds connect() will timeout
timeout.tv_usec = 0;

setsockopt(sockd, SOL_SOCKET, SO_SNDTIMEO, &timeout, sizeof(timeout));

if (sockd<0){
error("[Error] During Creation Of Socket Handler");
}
victim.sin_family = AF_INET;
while (p->next!=NULL){
printf("Scanning IP :%s | Port : %i ---> ", ip, p->data);
checkport(sockd, victim, p->data, ip, p);
tmp = p->next;
p = tmp;

}
printf("Scanning IP :%s | Port : %i ---> ", ip, p->data);
checkport(sockd, victim, p->data, ip, p);
tmp = p->next;
p = tmp;

close(sockd);

}



void ranger(char *exp, plist *p){
/*
*
* This Function is completely Dedicated To Generate Port Integers From Provided
* Port Expression.
*
*/

char s[6], e[6], *n;
int sn, en, i;

// Get Tail
n = strpbrk(exp, "-");

// Store it In another variable
// surpass '-' char
n++;

// copy value in ending variable
strcpy(e, n);

// convert string into integers
en = atoi(e);

// get head
n = strtok(exp, "-");

// store in another variable
strcpy(s, n);

// convert string into integers
sn = atoi(s);

// check range
if (sn >= en)
{
//printf("Starting From : %s, End at : %s\n",s,e);
//printf("Starting From : %i, End at : %i\n",sn,en);
; error("Incorrect Range Found");
}

for (i = sn; i < en; i++)
{
listappend(p, i);
}
}



// Argument Parser And Processing Function
void argument_parse(char *ip, char *port){
/*
*
* This Function Is Completely Dedicated To Extract Port Integers From Port Expressions
* And Also Generate Port Integers From Provided Port Range Expression.
*
*/

plist *p; // Port List Object Define

p = malloc(sizeof(plist)); // Allocate Space For List Object
p->next = NULL;
p->data = 0;
p->status = -1;

int l = strlen(port); // length of characters in port expression
char c; // to handle every single character of port expression
char pnum[PORT_EXPRESSION_ITER];
int pn = 0, iport;

bzero(pnum, sizeof(pnum)); // make sure, space is clear


// iter all characters of port expresion
for (int i = 0; i < l; i++)
{
c = port[i];

// check if character is a valid expression
if ((c == ' ') |
(c == '1') |
(c == '2') |
(c == '3') |
(c == '4') |
(c == '5') |
(c == '6') |
(c == '7') |
(c == '8') |
(c == '9') |
(c == '0') |
(c == '-') |
(c == ','))
{
// Start Storing Characters
if (pn == 0)
{
bzero(pnum, sizeof(pnum));
pnum[pn] = c; // string starting
pnum[PORT_EXPRESSION_ITER] = '\0'; // string end
pn++;
}

// Split Expression And Save Into List
else if ((c == ',') & (pn != 0))
{
// check if range expression
if (strpbrk(pnum, "-"))
{
ranger(pnum, p);
}
else
{
iport = atoi(pnum);
listappend(p ,iport);
}

// Reset Input character collector
pn = 0;
bzero(pnum, sizeof(pnum));
}


else if ((pn == 5)&(!strpbrk(pnum, "-")))
{

// check if range expression
if (strpbrk(pnum, "-"))
{
ranger(pnum, p);
}
else
{

iport = atoi(pnum);
listappend(p ,iport);
}

// Reset Input character collector
pn = 0;
bzero(pnum, sizeof(pnum));
pnum[pn] = c; // string starting
pnum[PORT_EXPRESSION_ITER] = '\0'; // string end
pn++;
}
else if (pn < 5)
{

pnum[pn] = c;
pn++;

}
else if (strpbrk(pnum, "-"))
{

pnum[pn] = c;
pn++;

}
else
{

printf("[-] Port Expression Droped Characters : %i\n", pn);
}
}
else
{
//printf("%s", c);
error("Please Provide Valid Port Range Expressions");
}
}

iport = atoi(pnum);
listappend(p ,iport);
//expandlist(p);

// Reset Input character collector
pn = 0;
bzero(pnum, sizeof(pnum));
portscanner(p, ip);

}

// main function trigger
int main(int argc, char const *argv[]){
/*
* This Main Function Is Completely Dedicated To Verify And Filter User
* Provided Arguments.
*
*/

char ip[16]; // IP Address Expression
char port[100]; // Port Range expression

// if no arguments passed
if (argc < 2)
{
printf(" Please Provide Arguments To Perform Function\n\n \
:~$ %s IP_ADDRESS PORT-RANGE\n\nSupported Port Expression 1,2,3-80,5 \n\t\t\t[Note] Range Supported Only In Middle Of Expression \n\t\t\t\t like port1,(Range: Port2-9) ,port10\n",
argv[0]);

error("Program Terminating... \n\t\tCause :- No Input Provided.");
}

// If Only One Argument is Provided
else if (argc < 3)
{
printf("Please Provide Arguments To Perform Function\n\n \
:~$ %s IP_ADDRESS PORT-RANGE\n\n\n",
argv[0]);

error("Program Terminating... \n\t\tCause : Insuffecient Input Provided.");
}

// Check if Provided Arguments are valid to process
else if ((argc == 3) & (strlen(argv[1]) < 16) & (strlen(argv[1]) > 8))
{
printf("Starting CheckPort Program Design/Written By Surajsinghbisht054@gmail.com\n\n\n");

strcpy(ip, argv[1]); // Get IP address
strcpy(port, argv[2]); // Get Port Range Expression
argument_parse(ip, port); // Transfer Controls To Argument Parse Function
}

// Unformatted Arguments Provided
else
{
printf("Please Provide Correct Arguments To Perform Function\n\n \
:~$ %s IP_ADDRESS PORT-RANGE\n\n\n",
argv[0]);

error("Program Terminating... \n\t\tCause : Unformatted Input Provided.");
}
return 0;
}
♥Dcode♥