libpeer/src/stun.c

#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "stun.h"
#include "utils.h"

uint32_t CRC32_TABLE[256] = {
    0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535,
    0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd,
    0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d,
    0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
    0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
    0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
    0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac,
    0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
    0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab,
    0xb6662d3d, 0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
    0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb,
    0x086d3d2d, 0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
    0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea,
    0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, 0x4db26158, 0x3ab551ce,
    0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
    0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
    0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409,
    0xce61e49f, 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
    0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739,
    0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
    0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344, 0x8708a3d2, 0x1e01f268,
    0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0,
    0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8,
    0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
    0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
    0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703,
    0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7,
    0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
    0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae,
    0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
    0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777, 0x88085ae6,
    0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
    0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d,
    0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5,
    0x47b2cf7f, 0x30b5ffe9, 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
    0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
    0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d};

void stun_msg_create(StunMessage* msg, uint16_t type) {
  StunHeader* header = (StunHeader*)msg->buf;
  header->type = htons(type);
  header->length = 0;
  header->magic_cookie = htonl(MAGIC_COOKIE);
  header->transaction_id[0] = htonl(CRC32_TABLE[1]);
  header->transaction_id[1] = htonl(CRC32_TABLE[2]);
  header->transaction_id[2] = htonl(CRC32_TABLE[3]);
  msg->size = sizeof(StunHeader);
}

int stun_set_mapped_address(char* value, uint8_t* mask, Address* addr) {
  int ret, i;
  char addr_string[ADDRSTRLEN];
  uint8_t* family = (uint8_t*)(value + 1);
  uint16_t* port = (uint16_t*)(value + 2);
  uint32_t* val32 = (uint32_t*)(value + 4);
  uint16_t* val16 = (uint16_t*)(value + 4);
  uint32_t* addr32 = (uint32_t*)(&addr->sin.sin_addr);
  uint16_t* addr16 = (uint16_t*)(&addr->sin6.sin6_addr);

  switch (addr->family) {
    case AF_INET6:
      *family = STUN_FAMILY_IPV6;
      for (i = 0; i < 8; i++) {
        val16[i] = addr16[i] ^ *(uint16_t*)(mask + 2 * i);
      }
      ret = 20;
      break;
    case AF_INET:
    default:
      *family = STUN_FAMILY_IPV4;
      *val32 = *addr32 ^ *(uint32_t*)mask;
      ret = 8;
      break;
  }

  *port = htons(addr->port) ^ *(uint16_t*)mask;
  addr_to_string(addr, addr_string, sizeof(addr_string));

  LOGD("XOR Mapped Address Family: %d", *family);
  LOGD("XOR Mapped Address Port: %d (Port XOR: %04x)", addr->port, *port);
  LOGD("XOR Mapped Address IP: %s (IP XOR: %08" PRIu32 ")", addr_string, *addr32);
  return ret;
}

void stun_get_mapped_address(char* value, uint8_t* mask, Address* addr) {
  int i;
  char addr_string[ADDRSTRLEN];
  uint32_t* addr32 = (uint32_t*)&addr->sin.sin_addr;
  uint16_t* addr16 = (uint16_t*)&addr->sin6.sin6_addr;
  uint8_t family = value[1];
  uint16_t port;

  switch (family) {
    case STUN_FAMILY_IPV6:
      addr_set_family(addr, AF_INET6);
      for (i = 0; i < 8; i++) {
        addr16[i] = (*(uint16_t*)(value + 4 + 2 * i) ^ *(uint16_t*)(mask + 2 * i));
      }
      break;
    case STUN_FAMILY_IPV4:
    default:
      addr_set_family(addr, AF_INET);
      *addr32 = (*(uint32_t*)(value + 4) ^ *(uint32_t*)mask);
      break;
  }

  port = ntohs(*(uint16_t*)(value + 2) ^ *(uint16_t*)mask);
  addr_to_string(addr, addr_string, sizeof(addr_string));
  addr_set_port(addr, port);

  LOGD("XOR Mapped Address Family: %d", family);
  LOGD("XOR Mapped Address Port: %d (Port XOR: %04x)", addr->port, port);
  LOGD("XOR Mapped Address IP: %s (IP XOR: %08" PRIu32 ")", addr_string, *addr32);
}

void stun_parse_msg_buf(StunMessage* msg) {
  StunHeader* header = (StunHeader*)msg->buf;

  int length = ntohs(header->length) + sizeof(StunHeader);

  int pos = sizeof(StunHeader);

  uint8_t mask[16];

  msg->stunclass = ntohs(header->type);
  if ((msg->stunclass & STUN_CLASS_ERROR) == STUN_CLASS_ERROR) {
    msg->stunclass = STUN_CLASS_ERROR;
  } else if ((msg->stunclass & STUN_CLASS_INDICATION) == STUN_CLASS_INDICATION) {
    msg->stunclass = STUN_CLASS_INDICATION;
  } else if ((msg->stunclass & STUN_CLASS_RESPONSE) == STUN_CLASS_RESPONSE) {
    msg->stunclass = STUN_CLASS_RESPONSE;
  } else if ((msg->stunclass & STUN_CLASS_REQUEST) == STUN_CLASS_REQUEST) {
    msg->stunclass = STUN_CLASS_REQUEST;
  }

  msg->stunmethod = ntohs(header->type) & 0x0FFF;
  if ((msg->stunmethod & STUN_METHOD_ALLOCATE) == STUN_METHOD_ALLOCATE) {
    msg->stunmethod = STUN_METHOD_ALLOCATE;
  } else if ((msg->stunmethod & STUN_METHOD_BINDING) == STUN_METHOD_BINDING) {
    msg->stunmethod = STUN_METHOD_BINDING;
  }

  while (pos < length) {
    StunAttribute* attr = (StunAttribute*)(msg->buf + pos);
    memset(mask, 0, sizeof(mask));
    // LOGD("Attribute Type: 0x%04x", ntohs(attr->type));
    // LOGD("Attribute Length: %d", ntohs(attr->length));

    switch (ntohs(attr->type)) {
      case STUN_ATTR_TYPE_MAPPED_ADDRESS:
        stun_get_mapped_address(attr->value, mask, &msg->mapped_addr);
        break;
      case STUN_ATTR_TYPE_USERNAME:
        memset(msg->username, 0, sizeof(msg->username));
        memcpy(msg->username, attr->value, ntohs(attr->length));
        // LOGD("length = %d, Username %s", ntohs(attr->length), msg->username);
        break;
      case STUN_ATTR_TYPE_MESSAGE_INTEGRITY:
        memcpy(msg->message_integrity, attr->value, ntohs(attr->length));

        char message_integrity_hex[41];

        for (int i = 0; i < 20; i++) {
          sprintf(message_integrity_hex + 2 * i, "%02x", (uint8_t)msg->message_integrity[i]);
        }

        break;
      case STUN_ATTR_TYPE_LIFETIME:
        break;
      case STUN_ATTR_TYPE_REALM:
        memset(msg->realm, 0, sizeof(msg->realm));
        memcpy(msg->realm, attr->value, ntohs(attr->length));
        LOGD("Realm %s", msg->realm);
        break;
      case STUN_ATTR_TYPE_NONCE:
        memset(msg->nonce, 0, sizeof(msg->nonce));
        memcpy(msg->nonce, attr->value, ntohs(attr->length));
        LOGD("Nonce %s", msg->nonce);
        break;
      case STUN_ATTR_TYPE_XOR_RELAYED_ADDRESS:
        *((uint32_t*)mask) = htonl(MAGIC_COOKIE);
        memcpy(mask + 4, header->transaction_id, sizeof(header->transaction_id));
        LOGD("XOR Relayed Address");
        stun_get_mapped_address(attr->value, mask, &msg->relayed_addr);
        break;
      case STUN_ATTR_TYPE_XOR_MAPPED_ADDRESS:
        *((uint32_t*)mask) = htonl(MAGIC_COOKIE);
        memcpy(mask + 4, header->transaction_id, sizeof(header->transaction_id));
        stun_get_mapped_address(attr->value, mask, &msg->mapped_addr);
        break;
      case STUN_ATTR_TYPE_PRIORITY:
        break;
      case STUN_ATTR_TYPE_USE_CANDIDATE:
        // LOGD("Use Candidate");
        break;
      case STUN_ATTR_TYPE_FINGERPRINT:
        memcpy(&msg->fingerprint, attr->value, ntohs(attr->length));
        // LOGD("Fingerprint: 0x%.4x", msg->fingerprint);
        break;
      case STUN_ATTR_TYPE_ICE_CONTROLLED:
      case STUN_ATTR_TYPE_ICE_CONTROLLING:
      case STUN_ATTR_TYPE_NETWORK_COST:
        // Do nothing
        break;
      default:
        LOGE("Unknown Attribute Type: 0x%04x", ntohs(attr->type));
        break;
    }

    pos += 4 * ((ntohs(attr->length) + 3) / 4) + sizeof(StunAttribute);
  }
}

void stun_calculate_fingerprint(char* buf, size_t len, uint32_t* fingerprint) {
  uint32_t c = 0xFFFFFFFF;
  int i = 0;

  for (i = 0; i < len; ++i) {
    c = CRC32_TABLE[(c ^ buf[i]) & 0xFF] ^ (c >> 8);
  }

  *fingerprint = htonl((c ^ 0xFFFFFFFF) ^ STUN_FINGERPRINT_XOR);
}

int stun_msg_write_attr(StunMessage* msg, StunAttrType type, uint16_t length, char* value) {
  StunHeader* header = (StunHeader*)msg->buf;

  StunAttribute* stun_attr = (StunAttribute*)(msg->buf + msg->size);

  stun_attr->type = htons(type);
  stun_attr->length = htons(length);
  if (value)
    memcpy(stun_attr->value, value, length);

  length = 4 * ((length + 3) / 4);
  header->length = htons(ntohs(header->length) + sizeof(StunAttribute) + length);

  msg->size += length + sizeof(StunAttribute);

  switch (type) {
    case STUN_ATTR_TYPE_REALM:
      memcpy(msg->realm, value, length);
      break;
    case STUN_ATTR_TYPE_NONCE:
      memcpy(msg->nonce, value, length);
      break;
    case STUN_ATTR_TYPE_USERNAME:
      memcpy(msg->username, value, length);
      break;
    default:
      break;
  }

  return 0;
}

int stun_msg_finish(StunMessage* msg, StunCredential credential, const char* password, size_t password_len) {
  StunHeader* header = (StunHeader*)msg->buf;
  StunAttribute* stun_attr;

  uint16_t header_length = ntohs(header->length);
  char key[256];
  char hash_key[17];
  memset(key, 0, sizeof(key));
  memset(hash_key, 0, sizeof(hash_key));

  switch (credential) {
    case STUN_CREDENTIAL_LONG_TERM:
      snprintf(key, sizeof(key), "%s:%s:%s", msg->username, msg->realm, password);
      LOGD("key: %s", key);
      utils_get_md5(key, strlen(key), (unsigned char*)hash_key);
      password = hash_key;
      password_len = 16;
      break;
    default:
      break;
  }

  stun_attr = (StunAttribute*)(msg->buf + msg->size);
  header->length = htons(header_length + 24); /* HMAC-SHA1 */
  stun_attr->type = htons(STUN_ATTR_TYPE_MESSAGE_INTEGRITY);
  stun_attr->length = htons(20);
  utils_get_hmac_sha1((char*)msg->buf, msg->size, password, password_len, (unsigned char*)stun_attr->value);
  msg->size += sizeof(StunAttribute) + 20;
  // FINGERPRINT

  stun_attr = (StunAttribute*)(msg->buf + msg->size);
  header->length = htons(header_length + 24 /* HMAC-SHA1 */ + 8 /* FINGERPRINT */);
  stun_attr->type = htons(STUN_ATTR_TYPE_FINGERPRINT);
  stun_attr->length = htons(4);
  stun_calculate_fingerprint((char*)msg->buf, msg->size, (uint32_t*)stun_attr->value);
  msg->size += sizeof(StunAttribute) + 4;
  return 0;
}

int stun_probe(uint8_t* buf, size_t size) {
  StunHeader* header;
  if (size < sizeof(StunHeader)) {
    LOGE("STUN message is too short.");
    return -1;
  }

  header = (StunHeader*)buf;
  if (header->magic_cookie != htonl(MAGIC_COOKIE)) {
    return -1;
  }

  return 0;
}

#if 0
StunMsgType stun_is_stun_msg(uint8_t *buf, size_t size) {

  if (size < sizeof(StunHeader)) {
    //LOGE("STUN message is too short.");
    return STUN_MSG_TYPE_INVLID;
  }

  StunHeader *header = (StunHeader *)buf;
  if (header->magic_cookie != htonl(MAGIC_COOKIE)) {
    //LOGE("STUN magic cookie does not match.");
    return STUN_MSG_TYPE_INVLID;
  }

  if (ntohs(header->type) == STUN_BINDING_REQUEST) {

    return STUN_MSG_TYPE_BINDING_REQUEST;

  } else if (ntohs(header->type) == STUN_BINDING_RESPONSE) {

    return STUN_MSG_TYPE_BINDING_RESPONSE;

  } else if (ntohs(header->type) == STUN_BINDING_ERROR_RESPONSE) {

    return STUN_MSG_TYPE_BINDING_ERROR_RESPONSE;
  } else {

    return STUN_MSG_TYPE_INVLID;
  }

  return 0;
}
#endif
int stun_msg_is_valid(uint8_t* buf, size_t size, char* password) {
  StunMessage msg;

  memcpy(msg.buf, buf, size);

  stun_parse_msg_buf(&msg);

  StunHeader* header = (StunHeader*)msg.buf;

  // FINGERPRINT
  uint32_t fingerprint = 0;
  size_t length = size - 4 - sizeof(StunAttribute);
  stun_calculate_fingerprint((char*)msg.buf, length, &fingerprint);
  // LOGD("Fingerprint: 0x%08x", fingerprint);

  if (fingerprint != msg.fingerprint) {
    // LOGE("Fingerprint does not match.");
    return -1;
  } else {
    // LOGD("Fingerprint matches.");
  }

  // MESSAGE-INTEGRITY
  unsigned char message_integrity_hex[41];
  unsigned char message_integrity[20];
  header->length = htons(ntohs(header->length) - 4 - sizeof(StunAttribute));
  length = length - 20 - sizeof(StunAttribute);
  utils_get_hmac_sha1((char*)msg.buf, length, password, strlen(password), message_integrity);
  for (int i = 0; i < 20; i++) {
    sprintf((char*)&message_integrity_hex[2 * i], "%02x", (uint8_t)message_integrity[i]);
  }

  // LOGD("message_integrity: 0x%s", message_integrity_hex);

  if (memcmp(message_integrity, msg.message_integrity, 20) != 0) {
    // LOGE("Message Integrity does not match.");
    return -1;
  } else {
    // LOGD("Message Integrity matches.");
  }

  return 0;
}