src/stun.c

   1 /*
   2  * transsip - the telephony network
   3  * By Daniel Borkmann <daniel@transsip.org>
   4  * Copyright 2011, 2012 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,
   5  * Swiss federal institute of technology (ETH Zurich)
   6  * Subject to the GPL, version 2.
   7  */
   8
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <stdint.h>
  12 #include <string.h>
  13 #include <errno.h>
  14 #include <time.h>
  15 #include <unistd.h>
  16 #include <netdb.h>
  17 #include <netinet/in.h>
  18 #include <sys/socket.h>
  19 #include <netinet/in.h>
  20 #include <arpa/inet.h>
  21 #include <sys/select.h>
  22
  23 #include "xmalloc.h"
  24 #include "xutils.h"
  25 #include "die.h"
  26
  27 #define BINDING_REQUEST               0x0001
  28 #define BINDING_RESPONSE              0x0101
  29
  30 #define MAPPED_ADDRESS                0x0001
  31
  32 #define TIMEOUT                       5000
  33 #define REQUEST_LEN                   20
  34
  35 #define ID_COOKIE_FIELD               htonl(((int) 'a' << 24) + \
  36                                             ((int) 'c' << 16) + \
  37                                             ((int) 'd' <<  8) + \
  38                                              (int) 'c')
  39
  40 struct stun_header {
  41         uint16_t type;
  42         uint16_t len;
  43         uint32_t magic_cookie;
  44         uint32_t transid[3];
  45 };
  46
  47 struct stun_attrib {
  48         uint16_t type;
  49         uint16_t len;
  50         uint8_t *value;
  51 };
  52
  53 struct stun_mapped_addr {
  54         uint8_t none;
  55         uint8_t family;
  56         uint16_t port;
  57         uint32_t ip;
  58 };
  59
  60 static int stun_test(const char *server_ip, int server_port,
  61                      int transsip_port)
  62 {
  63         int ret, sock, set = 1;
  64         uint8_t pkt[256];
  65         uint8_t rpkt[256];
  66         size_t len, off, max;
  67         struct in_addr in;
  68         struct timeval timeout;
  69         struct stun_header *hdr, *rhdr;
  70         struct stun_attrib *attr;
  71         struct stun_mapped_addr *addr;
  72         struct sockaddr_in saddr, daddr;
  73         fd_set fdset;
  74
  75         if (!server_ip)
  76                 return -EINVAL;
  77
  78         sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
  79         if (sock < 0)
  80                 panic("Cannot obtain socket!\n");
  81
  82         ret = setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &set, sizeof(set));
  83         if (ret)
  84                 panic("Cannot set socket option!\n");
  85
  86         saddr.sin_family = PF_INET;
  87         saddr.sin_port = htons(transsip_port);
  88         saddr.sin_addr.s_addr = INADDR_ANY;
  89
  90         ret = bind(sock, (struct sockaddr *) &saddr, sizeof(saddr));
  91         if (ret)
  92                 panic("Cannot bind udp socket!\n");
  93
  94         len = REQUEST_LEN;
  95         hdr = (struct stun_header *) pkt;
  96         hdr->type = htons(BINDING_REQUEST);
  97         hdr->len = 0;
  98         hdr->magic_cookie = ID_COOKIE_FIELD;
  99         hdr->transid[0] = htonl(rand());
 100         hdr->transid[1] = htonl(rand());
 101         hdr->transid[2] = htonl(rand());
 102
 103         daddr.sin_family = PF_INET;
 104         daddr.sin_port = htons(server_port);
 105         daddr.sin_addr.s_addr = inet_addr(server_ip);
 106
 107         ret = sendto(sock, pkt, len, 0, (struct sockaddr *) &daddr,
 108                      sizeof(daddr));
 109         if (ret != len) {
 110                 whine("Error sending request (%s)!\n", strerror(errno));
 111                 return -EIO;
 112         }
 113
 114         set_timeout(&timeout, TIMEOUT);
 115
 116         FD_ZERO(&fdset);
 117         FD_SET(sock, &fdset);
 118
 119         ret = select(sock + 1, &fdset, NULL, NULL, &timeout);
 120         if (ret <= 0) {
 121                 whine("STUN server timeout!\n");
 122                 return -EIO;
 123         }
 124
 125         memset(rpkt, 0, sizeof(rpkt));
 126         len = read(sock, rpkt, sizeof(rpkt));
 127
 128         close(sock);
 129
 130         if (len < REQUEST_LEN) {
 131                 whine("Bad STUN response (%s)!\n", strerror(errno));
 132                 return -EIO;
 133         }
 134
 135         rhdr = (struct stun_header *) rpkt;
 136         if (ntohs(rhdr->type) != BINDING_RESPONSE) {
 137                 whine("Wrong STUN response type!\n");
 138                 return -EIO;
 139         }
 140
 141         if (rhdr->len == 0) {
 142                 whine("No attributes in STUN response!\n");
 143                 return -EIO;
 144         }
 145
 146         if (rhdr->magic_cookie != hdr->magic_cookie ||
 147             rhdr->transid[0] != hdr->transid[0] ||
 148             rhdr->transid[1] != hdr->transid[1] ||
 149             rhdr->transid[2] != hdr->transid[2]) {
 150                 whine("Got wrong STUN transaction id!\n");
 151                 return -EIO;
 152         }
 153
 154         off = REQUEST_LEN;
 155         max = ntohs(rhdr->len) + REQUEST_LEN;
 156
 157         while (off + 8 < max) {
 158                 attr = (struct stun_attrib *) (rpkt + off);
 159                 if (ntohs(attr->type) != MAPPED_ADDRESS)
 160                         goto next;
 161
 162                 addr = (struct stun_mapped_addr *) (rpkt + off + 4);
 163                 if (addr->family != 0x1)
 164                         break;
 165
 166                 in.s_addr = addr->ip;
 167                 printf("Public mapping %s:%u!\n",
 168                        inet_ntoa(in), ntohs(addr->port));
 169                 break;
 170 next:
 171                 off += 4;
 172                 off += ntohs(attr->len);
 173         }
 174
 175         return 0;
 176 }
 177
 178 int print_stun_probe(char *server, int sport, int tport)
 179 {
 180         char *address;
 181         struct hostent *hp;
 182
 183         srand(time(NULL));
 184         hp = gethostbyname(server);
 185         if (!hp)
 186                 return -EIO;
 187         address = inet_ntoa(*(struct in_addr *) hp->h_addr_list[0]);
 188         return stun_test(address, sport, tport);
 189 }