feature: send packets (reponse not working tho)

.gitignore

@@ -2,3 +2,4 @@ obj
 ft_nmap
 .cache
 compile_commands.json
+tags

include/packet.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <stdint.h>
+
+#include "scan.h"
+
+struct pshdr {
+	uint32_t src_addr;
+	uint32_t dst_addr;
+	uint8_t placeholder;
+	uint8_t protocol;
+	uint16_t tcp_length;
+};
+
+int send_packets(const struct scan *data, int sockfd);
+unsigned short checksum(void *data, int len);

src/checksum.c

@@ -0,0 +1,13 @@
+#include <stddef.h>
+
+unsigned short checksum(void *data, int len)
+{
+	unsigned short *cpy = data;
+	unsigned int sum = 0;
+
+	for (int i = 0; i < len; i += 2)
+		sum += *cpy++;
+	sum = (sum >> 16) + (sum & 0xFFFF);
+	sum += (sum >> 16);
+	return ~sum;
+}

src/main.c

@@ -34,9 +34,11 @@ int main(int ac, char **av)
 	struct thread *single_thread = malloc(sizeof(struct thread));
 	if (get_interface_name(&single_thread->host) < 0)
 		return 1;
-	single_thread->port_start = 1;
+	single_thread->dest_addr = ip_addr;
+	single_thread->port_start = 21;
 	single_thread->port_end = 1024;
 	single_thread->responses = responses;
+	single_thread->type = SCAN_SYN;
 	if (routine(single_thread) == NULL) {
 		dprintf(2, "ft_nmap: failed to scan ports\n");
 		return 1;

src/packet.c

@@ -0,0 +1,108 @@
+#include <arpa/inet.h>
+#include <netinet/ip.h>
+#include <netinet/tcp.h>
+#include <netinet/udp.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "packet.h"
+#include "scan.h"
+
+void create_udp_packet(struct udphdr *udphdr, const struct scan *data)
+{
+	udphdr->source = htons(1234);
+	udphdr->dest = htons(data->port);
+	udphdr->len = sizeof(struct udphdr);
+	udphdr->check = 0;
+	udphdr->check = checksum(udphdr, sizeof(struct udphdr));
+}
+
+int create_tcp_packet(struct tcphdr *tcphdr, const struct scan *data)
+{
+	tcphdr->source = htons(1234);
+	tcphdr->dest = htons(data->port);
+	tcphdr->seq = 0;
+	tcphdr->ack_seq = 0;
+	tcphdr->doff = sizeof(struct tcphdr) / sizeof(int);
+	tcphdr->fin = data->type == SCAN_XMAS || data->type == SCAN_FIN;
+	tcphdr->syn = data->type == SCAN_SYN;
+	tcphdr->rst = 0;
+	tcphdr->psh = data->type == SCAN_XMAS;
+	tcphdr->ack = data->type == SCAN_ACK;
+	tcphdr->urg = data->type == SCAN_XMAS;
+	tcphdr->window = htons(5840);
+	tcphdr->check = 0;
+	tcphdr->urg_ptr = 0;
+
+	struct pshdr pshdr;
+	pshdr.src_addr = inet_addr(data->host->ip);
+	pshdr.dst_addr = inet_addr(data->dest_addr);
+	pshdr.placeholder = 0;
+	pshdr.protocol = IPPROTO_TCP;
+	pshdr.tcp_length = htons(sizeof(struct tcphdr));
+
+	size_t pseudogram_size = sizeof(struct pshdr) + sizeof(struct tcphdr);
+	void *pseudogram = malloc(pseudogram_size);
+	if (!pseudogram)
+		return -1;
+	memcpy(pseudogram, &pshdr, sizeof(pshdr));
+	memcpy(pseudogram + sizeof(pshdr), tcphdr, sizeof(struct tcphdr));
+	tcphdr->check = checksum(pseudogram, pseudogram_size);
+	free(pseudogram);
+
+	return 0;
+}
+
+static void *create_packet(const struct scan *data, size_t packet_size)
+{
+	const bool isudp = data->type == SCAN_UDP;
+	void *packet = malloc(packet_size);
+	if (!packet) {
+		dprintf(2,
+		        "ft_nmap: allocation failed during packet creation\n");
+		return NULL;
+	}
+
+	struct iphdr *iphdr = packet;
+	iphdr->ihl = sizeof(struct iphdr) / sizeof(int);
+	iphdr->version = 4;
+	iphdr->tos = 0;
+	iphdr->tot_len = packet_size;
+	iphdr->id = htons(54321);
+	iphdr->frag_off = 0;
+	iphdr->ttl = 48;
+	iphdr->protocol = isudp ? IPPROTO_UDP : IPPROTO_TCP;
+	iphdr->check = 0;
+	iphdr->saddr = inet_addr(data->host->ip);
+	iphdr->daddr = inet_addr(data->dest_addr);
+
+	iphdr->check = checksum(packet, packet_size);
+
+	// this is starnakin stuff
+	switch ((int)isudp) {
+	case true:
+		create_udp_packet(packet + sizeof(struct iphdr), data);
+		break;
+	default:
+		create_tcp_packet(packet + sizeof(struct iphdr), data);
+	}
+
+	return packet;
+}
+
+int send_packets(const struct scan *data, int sockfd)
+{
+	struct sockaddr_in conn_addr;
+
+	size_t packet_size = sizeof(struct iphdr) +
+	                     (data->type == SCAN_UDP ? sizeof(struct udphdr)
+	                                             : sizeof(struct tcphdr));
+	void *packet = create_packet(data, packet_size);
+	sendto(sockfd, packet, packet_size, 0, (struct sockaddr *)&conn_addr,
+	       sizeof(struct sockaddr_in));
+	free(packet);
+
+	return 0;
+}

src/scan.c

@@ -8,6 +8,7 @@
 #include <stdio.h>
 #include <sys/socket.h>
 
+#include "packet.h"
 #include "response.h"
 #include "scan.h"
 
@@ -18,6 +19,8 @@ static void dispatch_callback(u_char *user, const struct pcap_pkthdr *h,
 	const struct iphdr *iphdr =
 	    (struct iphdr *)(bytes + sizeof(struct ether_header));
 
+	printf("uwu\n");
+
 	if (iphdr->protocol == IPPROTO_TCP &&
 	    h->caplen >= sizeof(struct ether_header) + sizeof(struct iphdr) +
 	                     sizeof(struct tcphdr)) {
@@ -43,8 +46,8 @@ static void dispatch_callback(u_char *user, const struct pcap_pkthdr *h,
 
 int scan(const struct scan *data)
 {
-	int sockfd = socket(
+	int sockfd = socket(AF_INET, SOCK_RAW,
-	    AF_INET, data->type == SCAN_UDP ? SOCK_DGRAM : SOCK_STREAM, 0);
+	                    data->type == SCAN_UDP ? IPPROTO_UDP : IPPROTO_TCP);
 	if (sockfd < 0) {
 		dprintf(2, "ft_nmap: failed to create socket");
 		return -1;
@@ -71,7 +74,7 @@ int scan(const struct scan *data)
 	        data->dest_addr, data->port, data->host->ip);
 
 	if (pcap_compile(handle, &fp, pcap_expr, 0, mask) < 0) {
-		dprintf(2, "ft_nmap: failed to lookup net/mask\n");
+		dprintf(2, "ft_nmap: failed to compile pcap expression\n");
 		pcap_close(handle);
 		return -1;
 	}
@@ -84,7 +87,7 @@ int scan(const struct scan *data)
 
 	pcap_freecode(&fp);
 
-	// send packets
+	send_packets(data, sockfd);
 
 	// TODO test with another cnt value
 	if (pcap_dispatch(handle, 10, dispatch_callback, (u_char *)data)) {

src/thread.c

@@ -21,6 +21,8 @@ void *routine(void *p_data)
 		scan_data.response =
 		    &thread_data->responses[thread_data->port_start - port];
 		scan(&scan_data);
+		printf("state of port %d: %d\n", port,
+		       scan_data.response->state);
 	}
 
 	return p_data;