src/stun.c

   1 /*
   2  * transsip - the telephony network
   3  * By Daniel Borkmann <daniel@transsip.org>
   4  * Copyright 2011 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 <time.h>
  14 #include <unistd.h>
  15 #include <netdb.h>
  16 #include <netinet/in.h>
  17 #include <sys/socket.h>
  18 #include <netinet/in.h>
  19 #include <arpa/inet.h>
  20 #include <sys/select.h>
  21
  22 #include "xmalloc.h"
  23 #include "xutils.h"
  24 #include "stun.h"
  25
  26 /* Discovery type result */
  27 #define RESULT_NONE                   0
  28 #define RESULT_OPEN_INTERNET          1
  29 #define RESULT_FIREWALL_BLOCKS_UDP    2
  30 #define RESULT_SYMMETRIC_UDP_FIREWALL 3
  31 #define RESULT_FULL_CONE_NAT          4
  32 #define RESULT_SYMMETRIC_NAT          5
  33 #define RESULT_RESTRICTED_CONE_NAT    6
  34 #define RESULT_PORT_RESTR_CONE_NAT    7
  35
  36 /* Message types */
  37 #define BINDING_REQUEST               0x0001
  38 #define BINDING_RESPONSE              0x0101
  39 #define BINDING_ERROR_RESPONSE        0x0111
  40 #define SHARED_SECRET_REQUEST         0x0002
  41 #define SHARED_SECRET_RESPONSE        0x0102
  42 #define SHARED_SECRET_ERROR_RESPONSE  0x0112
  43
  44 /* Attribute types */
  45 #define MAPPED_ADDRESS                0x0001
  46 #define RESPONSE_ADDRESS              0x0002
  47 #define CHANGE_REQUEST                0x0003
  48 #define SOURCE_ADDRESS                0x0004
  49 #define CHANGED_ADDRESS               0x0005
  50 #define USERNAME                      0x0006
  51 #define PASSWORD                      0x0007
  52 #define MESSAGE_INTEGRITY             0x0008
  53 #define ERROR_CODE                    0x0009
  54 #define UNKNOWN_ATTRIBUTES            0x000a
  55 #define REFLECTED_FROM                0x000b
  56
  57 /* Error response codes */
  58 #define ERROR_BAD_REQUEST             400
  59 #define ERROR_UNAUTHORIZED            401
  60 #define ERROR_UNKNOWN_ATTRIBUTE       420
  61 #define ERROR_STALE_CREDENTIALS       430
  62 #define ERROR_INTEGRITY_CHECK_FAIL    431
  63 #define ERROR_MISSING_USERNAME        432
  64 #define ERROR_USE_TLS                 433
  65 #define ERROR_SERVER_ERROR            500
  66 #define ERROR_GLOBAL_FAILURE          600
  67
  68 #define TIMEOUT                       1000
  69 #define REQUEST_LEN                   20
  70
  71 #define ID_COOKIE_FIELD               htonl(((int) 'a' << 24) + \
  72                                             ((int) 'c' << 16) + \
  73                                             ((int) 'd' <<  8) + \
  74                                              (int) 'c')
  75
  76 struct stun_header {
  77         uint16_t type;
  78         /*
  79          * Message length is the count, in bytes, of the size of the
  80          * message, not including the 20 byte header. (RFC-3489)
  81          */
  82         uint16_t len;
  83         /*
  84          * transid also serves as salt to randomize the request and the
  85          * response. All responses carry the same identifier as
  86          * the request they correspond to.
  87          */
  88         /* For the new RFC this would be 0x2112A442 in network Byte order. */
  89         uint32_t magic_cookie;
  90         uint32_t transid[3];
  91 };
  92
  93 struct stun_attrib {
  94         uint16_t type;
  95         uint16_t len;
  96         uint8_t *value;
  97 };
  98
  99 struct stun_mapped_addr {
 100         uint8_t none;
 101         uint8_t family;
 102         uint16_t port;
 103         uint32_t ip;
 104 };
 105
 106 static int stun_test(const char *server_ip, int server_port,
 107                      int transsip_port)
 108 {
 109         int ret, sock, set = 1;
 110         uint8_t pkt[256];
 111         uint8_t rpkt[256];
 112         size_t len, off, max;
 113         struct in_addr in;
 114         struct timeval timeout;
 115         struct stun_header *hdr, *rhdr;
 116         struct stun_attrib *attr;
 117         struct stun_mapped_addr *addr;
 118         struct sockaddr_in saddr, daddr;
 119         fd_set fdset;
 120
 121         if (!server_ip)
 122                 return -EINVAL;
 123
 124         sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
 125         if (sock < 0)
 126                 panic("Cannot obtain socket!\n");
 127
 128         ret = setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &set, sizeof(set));
 129         if (ret)
 130                 panic("Cannot set socket option!\n");
 131
 132         saddr.sin_family = PF_INET;
 133         saddr.sin_port = htons(transsip_port);
 134         saddr.sin_addr.s_addr = INADDR_ANY;
 135
 136         ret = bind(sock, (struct sockaddr *) &saddr, sizeof(saddr));
 137         if (ret)
 138                 panic("Cannot bind udp socket!\n");
 139
 140         len = REQUEST_LEN;
 141         hdr = (struct stun_header *) pkt;
 142         hdr->type = htons(BINDING_REQUEST);
 143         hdr->len = 0;
 144         hdr->magic_cookie = ID_COOKIE_FIELD;
 145         hdr->transid[0] = htonl(rand());
 146         hdr->transid[1] = htonl(rand());
 147         hdr->transid[2] = htonl(rand());
 148
 149         daddr.sin_family = PF_INET;
 150         daddr.sin_port = htons(server_port);
 151         daddr.sin_addr.s_addr = inet_addr(server_ip);
 152
 153         ret = sendto(sock, pkt, len, 0, (struct sockaddr *) &daddr,
 154                      sizeof(daddr));
 155         if (ret != len) {
 156                 whine("Error sending request (%s)!\n", strerror(errno));
 157                 return -EIO;
 158         }
 159
 160         set_timeout(&timeout, TIMEOUT);
 161
 162         FD_ZERO(&fdset);
 163         FD_SET(sock, &fdset);
 164
 165         ret = select(sock + 1, &fdset, NULL, NULL, &timeout);
 166         if (ret <= 0) {
 167                 whine("STUN server timeout!\n");
 168                 return -EIO;
 169         }
 170
 171         memset(rpkt, 0, sizeof(rpkt));
 172         len = read(sock, rpkt, sizeof(rpkt));
 173
 174         close(sock);
 175
 176         if (len < REQUEST_LEN) {
 177                 whine("Bad STUN response (%s)!\n", strerror(errno));
 178                 return -EIO;
 179         }
 180
 181         rhdr = (struct stun_header *) rpkt;
 182         if (ntohs(rhdr->type) != BINDING_RESPONSE) {
 183                 whine("Wrong STUN response type!\n");
 184                 return -EIO;
 185         }
 186
 187         if (rhdr->len == 0) {
 188                 whine("No attributes in STUN response!\n");
 189                 return -EIO;
 190         }
 191
 192         if (rhdr->magic_cookie != hdr->magic_cookie ||
 193             rhdr->transid[0] != hdr->transid[0] ||
 194             rhdr->transid[1] != hdr->transid[1] ||
 195             rhdr->transid[2] != hdr->transid[2]) {
 196                 whine("Got wrong STUN transaction id!\n");
 197                 return -EIO;
 198         }
 199
 200         off = REQUEST_LEN;
 201         max = ntohs(rhdr->len) + REQUEST_LEN;
 202
 203         while (off + 8 < max) {
 204                 attr = (struct stun_attrib *) (rpkt + off);
 205                 if (ntohs(attr->type) != MAPPED_ADDRESS)
 206                         goto next;
 207
 208                 addr = (struct stun_mapped_addr *) (rpkt + off + 4);
 209                 if (addr->family != 0x1)
 210                         break;
 211
 212                 in.s_addr = addr->ip;
 213                 info("Public mapping %s:%u!\n", inet_ntoa(in), ntohs(addr->port));
 214                 break;
 215 next:
 216                 off += 4;
 217                 off += ntohs(attr->len);
 218         }
 219
 220         return 0;
 221 }
 222
 223 void print_stun_probe(char *server, int sport, int tport)
 224 {
 225         char *address;
 226         struct hostent *hp;
 227
 228 /*      printf("STUN on %s:%u\n", server, sport); */
 229         srand(time(NULL));
 230         hp = gethostbyname(server);
 231         if (!hp)
 232                 return;
 233         address = inet_ntoa(*(struct in_addr *) hp->h_addr_list[0]);
 234         stun_test(address, sport, tport);
 235 }