ARP scan: get relevant network info

.gitignore

@@ -3,3 +3,4 @@
 simple_request
 arp_spoof
 arp_mitm
+arp_scan

Makefile

@@ -3,7 +3,7 @@ CFLAGS=-g -Wall
 
 .PHONY: clean all
 
-all: simple_request arp_spoof arp_mitm
+all: simple_request arp_spoof arp_mitm arp_scan
 
 simple_request: simple_request.o arp.o
 
@@ -11,6 +11,8 @@ arp_spoof: arp_spoof.o arp.o
 
 arp_mitm: arp_mitm.o arp.o
 
+arp_scan: arp_scan.o arp.o
+
 %.o: %.c %.h
 	$(CC) -c $< $(CFLAGS)
 

arp_scan.c

@@ -0,0 +1,144 @@
+/* arp-spoof/arp_scan.c */
+
+#include "arp.h"
+
+int main(int argc, char **argv)
+{
+
+  /* ARGUMENT PARSING
+     - network interface to use
+     - target IP address
+  */
+  
+  if (argc == 0) {
+    printf("[FAIL] Too few arguments\n"
+	   "Usage: %s <interface>\n", argv[0]);
+    exit(EXIT_FAILURE);
+  }
+
+  char *if_name = argv[1];
+
+
+  
+  /* ====================================================================== */
+
+  /* RAW SOCKET CREATION */
+  
+  /* We open the raw socket */
+  /* AF_PACKET: This is a raw Ethernet packet (Linux only, requires root)
+     SOCK_DGRAM: The link-layer header is constructed automatically
+     (to build it ourselves, we could have used SOCK_RAW)
+     ETH_P_ALL: We want to listen to every EtherType (here, we could 
+     also have chosen ETH_P_ARP) */
+  int sockfd = socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_ALL));
+  if (sockfd < 0) {
+    perror("[FAIL] socket()");
+    exit(EXIT_FAILURE);
+  }
+#ifdef DEBUG
+  printf("[OK] Raw Ethernet socket started successfully\n");
+#endif
+
+
+
+  /* ====================================================================== */
+
+  /* INFORMATION ON THE LOCAL COMPUTER:
+     - index number of the network interface
+     - local IP address
+     - local MAC address
+     - subnet mask
+  */
+
+  /* Since this is very low-level, we can't use the usual interface
+     name (e.g. "eth0"), so we need to get the index number of the
+     ethernet interface. */
+  //char *if_name = "wlp3s0"; /* Change this if needed */
+  struct ifreq ifrindex;
+  size_t if_name_len = strlen(if_name);
+  if (if_name_len < sizeof(ifrindex.ifr_name)) {
+    memcpy(ifrindex.ifr_name, if_name, if_name_len);
+    ifrindex.ifr_name[if_name_len] = 0;
+  }
+  else {
+    printf("[FAIL] Error: interface name is too long\n");
+  }
+  /* We use ioctl() with SIOCGIFINDEX */
+  if (ioctl(sockfd, SIOCGIFINDEX, &ifrindex) == -1) {
+    perror("[FAIL] ioctl()");
+    exit(EXIT_FAILURE);
+  }
+  int ifindex = ifrindex.ifr_ifindex;
+#ifdef DEBUG
+  printf("[OK] Index number of the Ethernet interface %s: %d\n", if_name, ifindex);
+#endif
+
+  /* We get our IP address using ioctl() and SIOCGIFADDR */
+  struct ifreq ifraddr;
+  if (if_name_len < sizeof(ifraddr.ifr_name)) {
+    memcpy(ifraddr.ifr_name, if_name, if_name_len);
+    ifraddr.ifr_name[if_name_len] = 0;
+  }
+  else {
+    printf("[FAIL] Error: interface name is too long\n");
+  }
+  if (ioctl(sockfd, SIOCGIFADDR, &ifraddr) == -1) {
+    perror("[FAIL] ioctl()");
+    exit(EXIT_FAILURE);
+  }
+  struct sockaddr_in *ipaddr = (struct sockaddr_in *) &ifraddr.ifr_addr;
+  char local_ip_string[16];
+  if (!inet_ntop(AF_INET, &ipaddr->sin_addr, local_ip_string, sizeof(local_ip_string))) {
+    perror("[FAIL] inet_ntop()");
+    exit(EXIT_FAILURE);
+  }
+#ifdef DEBUG
+  printf("[OK] Local IP address: %s\n", local_ip_string);
+#endif
+  
+  /* We get the MAC address using ioctl() (again) with SIOCGIFHWADDR */
+  struct ifreq ifrhwaddr;
+  if (if_name_len < sizeof(ifrhwaddr.ifr_name)) {
+    memcpy(ifrhwaddr.ifr_name, if_name, if_name_len);
+    ifrhwaddr.ifr_name[if_name_len] = 0;
+  }
+  else {
+    printf("[FAIL] Error: interface name is too long\n");
+  }
+  if (ioctl(sockfd, SIOCGIFHWADDR, &ifrhwaddr) == -1) {
+    perror("[FAIL] ioctl()");
+    exit(EXIT_FAILURE);
+  }
+  unsigned char *macaddr = (unsigned char *) &ifrhwaddr.ifr_hwaddr.sa_data;
+#ifdef DEBUG
+  printf("[OK] Local MAC address: %02x:%02x:%02x:%02x:%02x:%02x\n",
+	 macaddr[0], macaddr[1], macaddr[2], macaddr[3], macaddr[4], macaddr[5]);
+#endif
+
+  /* We get the subnet mask using ioctl() with SIOCGIFNETMASK */
+  struct ifreq ifrnetmask;
+  if (if_name_len < sizeof(ifrnetmask.ifr_name)) {
+    memcpy(ifrnetmask.ifr_name, if_name, if_name_len);
+    ifrnetmask.ifr_name[if_name_len] = 0;
+  }
+  else {
+    printf("[FAIL] Error: interface name is too long\n");
+  }
+  if (ioctl(sockfd, SIOCGIFNETMASK, &ifrnetmask) == -1) {
+    perror("[FAIL] ioctl()");
+    exit(EXIT_FAILURE);
+  }
+  struct sockaddr_in *netmask = (struct sockaddr_in *) &ifrnetmask.ifr_netmask;
+  char netmask_string[16];
+  if (!inet_ntop(AF_INET, &netmask->sin_addr, netmask_string, sizeof(netmask_string))) {
+    perror("[FAIL] inet_ntop()");
+    exit(EXIT_FAILURE);
+  }
+#ifdef DEBUG
+  printf("[OK] Local netmask: %s\n", netmask_string);
+#endif
+    
+
+  
+}
+