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/*
* Copyright (C) 2014-2017 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 "firejail.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;
// returns 0 if the address is not in use, -1 otherwise
int arp_check(const char *dev, uint32_t destaddr, uint32_t srcaddr) {
if (strlen(dev) > IFNAMSIZ) {
fprintf(stderr, "Error: invalid network device name %s\n", dev);
exit(1);
}
if (arg_debug)
printf("Trying %d.%d.%d.%d ...\n", PRINT_IP(destaddr));
// find interface address
int sock;
if ((sock = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
errExit("socket");
srcaddr = htonl(srcaddr);
destaddr = htonl(destaddr);
// Find interface MAC address
struct ifreq ifr;
memset(&ifr, 0, sizeof (ifr));
strncpy(ifr.ifr_name, dev, IFNAMSIZ);
if (ioctl(sock, SIOCGIFHWADDR, &ifr) < 0)
errExit("ioctl");
close(sock);
// 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, ifr.ifr_hwaddr.sa_data, 6);
addr.sll_halen = htons(6);
// 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, ifr.ifr_hwaddr.sa_data, 6);
memcpy(hdr.sender_ip, (uint8_t *)&srcaddr, 4);
memcpy(hdr.target_ip, (uint8_t *)&destaddr, 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, ifr.ifr_hwaddr.sa_data, 6);
frame[12] = ETH_P_ARP / 256;
frame[13] = ETH_P_ARP % 256;
memcpy (frame + 14, &hdr, sizeof(hdr));
// open layer2 socket
if ((sock = socket(PF_PACKET, SOCK_RAW, htons (ETH_P_ALL))) < 0)
errExit("socket");
int len;
if ((len = sendto (sock, frame, 14 + sizeof(ArpHdr), 0, (struct sockaddr *) &addr, sizeof (addr))) <= 0)
errExit("send");
fflush(0);
// wait not more than one second for an answer
fd_set fds;
FD_ZERO(&fds);
FD_SET(sock, &fds);
int maxfd = sock;
struct timeval ts;
ts.tv_sec = 1; // 1 second wait time
ts.tv_usec = 0;
while (1) {
int nready = select(maxfd + 1, &fds, (fd_set *) 0, (fd_set *) 0, &ts);
if (nready < 0)
errExit("select");
else if (nready == 0) { // timeout
close(sock);
return 0;
}
else {
// read the incoming packet
int len = recvfrom(sock, frame, ETH_FRAME_LEN, 0, NULL, NULL);
if (len < 0) {
perror("recvfrom");
close(sock);
return -1;
}
// parse the incoming packet
if ((unsigned int) len < 14 + sizeof(ArpHdr))
continue;
if (frame[12] != (ETH_P_ARP / 256) || frame[13] != (ETH_P_ARP % 256))
continue;
memcpy(&hdr, frame + 14, sizeof(ArpHdr));
if (hdr.opcode == htons(1))
continue;
if (hdr.opcode == htons(2)) {
// check my mac and my address
if (memcmp(ifr.ifr_hwaddr.sa_data, hdr.target_mac, 6) != 0)
continue;
uint32_t ip;
memcpy(&ip, hdr.target_ip, 4);
if (ip != srcaddr) {
continue;
}
close(sock);
return -1;
}
}
}
// it will never get here!
close(sock);
return -1;
}
// assign a random IP address and check it
// the address needs to be in the range if it --iprange was specified
static uint32_t arp_random(const char *dev, Bridge *br) {
assert(dev);
assert(br);
uint32_t ifip = br->ip;
uint32_t ifmask = br->mask;
assert(ifip);
assert(ifmask);
if (arg_debug)
printf("ARP-scan %s, %d.%d.%d.%d/%d\n",
dev, PRINT_IP(ifip), mask2bits(ifmask));
// determine the range based on network address
uint32_t range = ~ifmask + 1; // the number of potential addresses
// this software is not supported for /31 networks
if (range < 4)
return 0; // the user will have to set the IP address manually
range -= 2; // subtract the network address and the broadcast address
uint32_t start = (ifip & ifmask) + 1;
// adjust range based on --iprange params
if (br->iprange_start && br->iprange_end) {
start = br->iprange_start;
range = br->iprange_end - br->iprange_start;
}
if (arg_debug)
printf("IP address range from %d.%d.%d.%d to %d.%d.%d.%d\n",
PRINT_IP(start), PRINT_IP(start + range));
// generate a random address - 10 tries
uint32_t dest = 0;
int i = 0;
for (i = 0; i < 10; i++) {
dest = start + ((uint32_t) rand()) % range;
if (dest == ifip) // do not allow the interface address
continue; // try again
// if we've made it up to here, we have a valid address
break;
}
if (i == 10) // we failed 10 times
return 0;
// check address
uint32_t rv = arp_check(dev, dest, ifip);
if (!rv)
return dest;
return 0;
}
// go sequentially trough all IP addresses and assign the first one not in use
static uint32_t arp_sequential(const char *dev, Bridge *br) {
assert(dev);
assert(br);
uint32_t ifip = br->ip;
uint32_t ifmask = br->mask;
assert(ifip);
assert(ifmask);
// range based on network address
uint32_t range = ~ifmask + 1; // the number of potential addresses
// this software is not supported for /31 networks
if (range < 4)
return 0; // the user will have to set the IP address manually
range -= 2; // subtract the network address and the broadcast address
// try all possible ip addresses in ascending order
// start address
uint32_t dest = (ifip & ifmask) + 1;
if (br->iprange_start)
dest = br->iprange_start;
// end address
uint32_t last = dest + range - 1;
if (br->iprange_end)
last = br->iprange_end;
if (arg_debug)
printf("Trying IP address range from %d.%d.%d.%d to %d.%d.%d.%d\n",
PRINT_IP(dest), PRINT_IP(last));
// loop through addresses and stop as soon as you find an unused one
while (dest <= last) {
if (dest == ifip) {
dest++;
continue;
}
uint32_t rv = arp_check(dev, dest, ifip);
if (!rv)
return dest;
dest++;
}
return 0;
}
// assign an IP address first trying some random addresses, and if this fails
// by doing an arp scan.
//
// dev is the name of the device to use in scanning,
// br is bridge structure holding the ip address and mask to use in
// arp packets. It also holds values for for the range of addresses
// if --iprange was set by the user
uint32_t arp_assign(const char *dev, Bridge *br) {
assert(br);
uint32_t ip = 0;
// try two random IP addresses
ip = arp_random(dev, br);
if (!ip)
ip = arp_random(dev, br);
// try all possible IP addresses one by one
if (!ip)
ip = arp_sequential(dev, br);
// print result
if (!ip) {
fprintf(stderr, "Error: cannot assign an IP address; it looks like all of them are in use.\n");
logerr("Cannot assign an IP address; it looks like all of them are in use.");
exit(1);
}
return ip;
}
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