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/*
* Copyright (C) 2014-2019 Firejail Authors
*
* This file is part of firejail project
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "fnet.h"
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/if_ether.h> //TCP/IP Protocol Suite for Linux
#include <net/if.h>
#include <netinet/in.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/if_packet.h>
typedef struct arp_hdr_t {
uint16_t htype;
uint16_t ptype;
uint8_t hlen;
uint8_t plen;
uint16_t opcode;
uint8_t sender_mac[6];
uint8_t sender_ip[4];
uint8_t target_mac[6];
uint8_t target_ip[4];
} ArpHdr;
// scan interface (--scan option)
void arp_scan(const char *dev, uint32_t ifip, uint32_t ifmask) {
assert(dev);
assert(ifip);
// printf("Scanning interface %s (%d.%d.%d.%d/%d)\n",
// dev, PRINT_IP(ifip & ifmask), mask2bits(ifmask));
if (strlen(dev) > IFNAMSIZ) {
fprintf(stderr, "Error: invalid network device name %s\n", dev);
exit(1);
}
// find interface mac address
int sock;
if ((sock = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
errExit("socket");
struct ifreq ifr;
memset(&ifr, 0, sizeof (ifr));
strncpy(ifr.ifr_name, dev, IFNAMSIZ - 1);
if (ioctl(sock, SIOCGIFHWADDR, &ifr) < 0)
errExit("ioctl");
close(sock);
uint8_t mac[6];
memcpy (mac, ifr.ifr_hwaddr.sa_data, 6);
// open layer2 socket
if ((sock = socket(PF_PACKET, SOCK_RAW, htons (ETH_P_ALL))) < 0)
errExit("socket");
// try all possible ip addresses in ascending order
uint32_t range = ~ifmask + 1; // the number of potential addresses
// this software is not supported for /31 networks
if (range < 4) {
fprintf(stderr, "Warning: this option is not supported for /31 networks\n");
close(sock);
return;
}
uint32_t dest = (ifip & ifmask) + 1;
uint32_t last = dest + range - 1;
uint32_t src = htonl(ifip);
// wait not more than one second for an answer
int header_printed = 0;
uint32_t last_ip = 0;
struct timeval ts;
ts.tv_sec = 2; // 2 seconds receive timeout
ts.tv_usec = 0;
while (1) {
fd_set rfds;
FD_ZERO(&rfds);
FD_SET(sock, &rfds);
fd_set wfds;
FD_ZERO(&wfds);
FD_SET(sock, &wfds);
int maxfd = sock;
uint8_t frame[ETH_FRAME_LEN]; // includes eht header, vlan, and crc
memset(frame, 0, ETH_FRAME_LEN);
int nready;
if (dest < last)
nready = select(maxfd + 1, &rfds, &wfds, (fd_set *) 0, NULL);
else
nready = select(maxfd + 1, &rfds, (fd_set *) 0, (fd_set *) 0, &ts);
if (nready < 0)
errExit("select");
if (nready == 0) { // timeout
break;
}
if (FD_ISSET(sock, &wfds) && dest < last) {
// configure layer2 socket address information
struct sockaddr_ll addr;
memset(&addr, 0, sizeof(addr));
if ((addr.sll_ifindex = if_nametoindex(dev)) == 0)
errExit("if_nametoindex");
addr.sll_family = AF_PACKET;
memcpy (addr.sll_addr, mac, 6);
addr.sll_halen = ETH_ALEN;
// build the arp packet header
ArpHdr hdr;
memset(&hdr, 0, sizeof(hdr));
hdr.htype = htons(1);
hdr.ptype = htons(ETH_P_IP);
hdr.hlen = 6;
hdr.plen = 4;
hdr.opcode = htons(1); //ARPOP_REQUEST
memcpy(hdr.sender_mac, mac, 6);
memcpy(hdr.sender_ip, (uint8_t *)&src, 4);
uint32_t dst = htonl(dest);
memcpy(hdr.target_ip, (uint8_t *)&dst, 4);
// build ethernet frame
uint8_t frame[ETH_FRAME_LEN]; // includes eht header, vlan, and crc
memset(frame, 0, sizeof(frame));
frame[0] = frame[1] = frame[2] = frame[3] = frame[4] = frame[5] = 0xff;
memcpy(frame + 6, mac, 6);
frame[12] = ETH_P_ARP / 256;
frame[13] = ETH_P_ARP % 256;
memcpy (frame + 14, &hdr, sizeof(hdr));
// send packet
int len;
if ((len = sendto (sock, frame, 14 + sizeof(ArpHdr), 0, (struct sockaddr *) &addr, sizeof (addr))) <= 0)
errExit("send");
//printf("send %d bytes to %d.%d.%d.%d\n", len, PRINT_IP(dest));
fflush(0);
dest++;
}
if (FD_ISSET(sock, &rfds)) {
// read the incoming packet
int len = recvfrom(sock, frame, ETH_FRAME_LEN, 0, NULL, NULL);
if (len < 0) {
perror("recvfrom");
}
// parse the incoming packet
if ((unsigned int) len < 14 + sizeof(ArpHdr))
continue;
// look only at ARP packets
if (frame[12] != (ETH_P_ARP / 256) || frame[13] != (ETH_P_ARP % 256))
continue;
ArpHdr hdr;
memcpy(&hdr, frame + 14, sizeof(ArpHdr));
if (hdr.opcode == htons(2)) {
// check my mac and my address
if (memcmp(mac, hdr.target_mac, 6) != 0)
continue;
uint32_t ip;
memcpy(&ip, hdr.target_ip, 4);
if (ip != src)
continue;
memcpy(&ip, hdr.sender_ip, 4);
ip = ntohl(ip);
if (ip == last_ip) // filter duplicates
continue;
last_ip = ip;
// printing
if (header_printed == 0) {
fmessage(" Network scan:\n");
header_printed = 1;
}
fmessage(" %02x:%02x:%02x:%02x:%02x:%02x\t%d.%d.%d.%d\n",
PRINT_MAC(hdr.sender_mac), PRINT_IP(ip));
}
}
}
close(sock);
}
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