stun.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <stdint.h>
   4 #include <string.h>
   5 #include <errno.h>
   6 #include <time.h>
   7 #include <unistd.h>
   8 #include <netdb.h>
   9 #include <netinet/in.h>
  10 #include <sys/socket.h>
  11 #include <netinet/in.h>
  12 #include <arpa/inet.h>
  13 #include <sys/select.h>
  14
  15 #include "xmalloc.h"
  16 #include "die.h"
  17 #include "sock.h"
  18 #include "stun.h"
  19
  20 #define BINDING_REQUEST               0x0001
  21 #define BINDING_RESPONSE              0x0101
  22
  23 #define MAPPED_ADDRESS                0x0001
  24
  25 #define TIMEOUT                       5000
  26 #define REQUEST_LEN                   20
  27
  28 #define ID_COOKIE_FIELD               htonl(((int) 'a' << 24) + \
  29                                             ((int) 'c' << 16) + \
  30                                             ((int) 'd' <<  8) + \
  31                                              (int) 'c')
  32
  33 struct stun_header {
  34         uint16_t type;
  35         uint16_t len;
  36         uint32_t magic_cookie;
  37         uint32_t transid[3];
  38 };
  39
  40 struct stun_attrib {
  41         uint16_t type;
  42         uint16_t len;
  43         uint8_t *value;
  44 };
  45
  46 struct stun_mapped_addr {
  47         uint8_t none;
  48         uint8_t family;
  49         uint16_t port;
  50         uint32_t ip;
  51 };
  52
  53 static int stun_test(const char *server_ip, int server_port,
  54                      int tun_port)
  55 {
  56         int ret, sock;
  57         uint8_t pkt[256];
  58         uint8_t rpkt[256];
  59         size_t len, off, max;
  60         struct in_addr in;
  61         struct timeval timeout;
  62         struct stun_header *hdr, *rhdr;
  63         struct stun_attrib *attr;
  64         struct stun_mapped_addr *addr;
  65         struct sockaddr_in saddr, daddr;
  66         fd_set fdset;
  67
  68         if (!server_ip)
  69                 return -EINVAL;
  70
  71         sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
  72         if (sock < 0)
  73                 panic("Cannot obtain socket!\n");
  74
  75         set_reuseaddr(sock);
  76
  77         saddr.sin_family = PF_INET;
  78         saddr.sin_port = htons(tun_port);
  79         saddr.sin_addr.s_addr = INADDR_ANY;
  80
  81         ret = bind(sock, (struct sockaddr *) &saddr, sizeof(saddr));
  82         if (ret)
  83                 panic("Cannot bind udp socket!\n");
  84
  85         len = REQUEST_LEN;
  86         hdr = (struct stun_header *) pkt;
  87         hdr->type = htons(BINDING_REQUEST);
  88         hdr->len = 0;
  89         hdr->magic_cookie = ID_COOKIE_FIELD;
  90         hdr->transid[0] = htonl(rand());
  91         hdr->transid[1] = htonl(rand());
  92         hdr->transid[2] = htonl(rand());
  93
  94         daddr.sin_family = PF_INET;
  95         daddr.sin_port = htons(server_port);
  96         daddr.sin_addr.s_addr = inet_addr(server_ip);
  97
  98         ret = sendto(sock, pkt, len, 0, (struct sockaddr *) &daddr,
  99                      sizeof(daddr));
 100         if (ret != len) {
 101                 printf("Error sending request (%s)!\n", strerror(errno));
 102                 return -EIO;
 103         }
 104
 105         timeout.tv_sec = TIMEOUT / 1000;
 106         timeout.tv_usec = (TIMEOUT % 1000) * 1000;
 107
 108         FD_ZERO(&fdset);
 109         FD_SET(sock, &fdset);
 110
 111         ret = select(sock + 1, &fdset, NULL, NULL, &timeout);
 112         if (ret <= 0) {
 113                 printf("STUN server timeout!\n");
 114                 return -EIO;
 115         }
 116
 117         memset(rpkt, 0, sizeof(rpkt));
 118         len = read(sock, rpkt, sizeof(rpkt));
 119
 120         close(sock);
 121
 122         if (len < REQUEST_LEN) {
 123                 printf("Bad STUN response (%s)!\n", strerror(errno));
 124                 return -EIO;
 125         }
 126
 127         rhdr = (struct stun_header *) rpkt;
 128         if (ntohs(rhdr->type) != BINDING_RESPONSE) {
 129                 printf("Wrong STUN response type!\n");
 130                 return -EIO;
 131         }
 132
 133         if (rhdr->len == 0) {
 134                 printf("No attributes in STUN response!\n");
 135                 return -EIO;
 136         }
 137
 138         if (rhdr->magic_cookie != hdr->magic_cookie ||
 139             rhdr->transid[0] != hdr->transid[0] ||
 140             rhdr->transid[1] != hdr->transid[1] ||
 141             rhdr->transid[2] != hdr->transid[2]) {
 142                 printf("Got wrong STUN transaction id!\n");
 143                 return -EIO;
 144         }
 145
 146         off = REQUEST_LEN;
 147         max = ntohs(rhdr->len) + REQUEST_LEN;
 148
 149         while (off + 8 < max) {
 150                 attr = (struct stun_attrib *) (rpkt + off);
 151                 if (ntohs(attr->type) != MAPPED_ADDRESS)
 152                         goto next;
 153
 154                 addr = (struct stun_mapped_addr *) (rpkt + off + 4);
 155                 if (addr->family != 0x1)
 156                         break;
 157
 158                 in.s_addr = addr->ip;
 159                 printf("Public mapping %s:%u!\n",
 160                        inet_ntoa(in), ntohs(addr->port));
 161                 break;
 162 next:
 163                 off += 4;
 164                 off += ntohs(attr->len);
 165         }
 166
 167         return 0;
 168 }
 169
 170 int print_stun_probe(char *server, int sport, int tport)
 171 {
 172         char *address;
 173         struct hostent *hp;
 174
 175         printf("STUN on %s:%u\n", server, sport);
 176
 177         srand(time(NULL));
 178         hp = gethostbyname(server);
 179         if (!hp)
 180                 return -EIO;
 181         address = inet_ntoa(*(struct in_addr *) hp->h_addr_list[0]);
 182         return stun_test(address, sport, tport);
 183 }