Merge branch 'tor-gitlab/mr/292_squashed' into maint-0.4.4

  { NULL, 0 }

};

/* Returns the first port that we think we can bind to without special

 * permissions. Usually this function returns 1024. */

static uint16_t

unprivileged_port_range_start(void)

{

  uint16_t result = 1024;

#if defined(__linux__)

  char *content = NULL;

  content = read_file_to_str(

              "/proc/sys/net/ipv4/ip_unprivileged_port_start",

              0,

              NULL);

  if (content != NULL) {

    int ok = 1;

    uint16_t tmp_result;

    tmp_result = (uint16_t)tor_parse_long(content, 10, 0, 65535, &ok, NULL);

    if (ok) {

      result = tmp_result;

    } else {

      fprintf(stderr,

              "Unable to convert ip_unprivileged_port_start to integer: %s\n",

              content);

    }

  }

  tor_free(content);

#endif /* defined(__linux__) */

  return result;

}

#if !defined(_WIN32)

#define PORT_TEST_RANGE_START 600

#define PORT_TEST_RANGE_END   1024

/* 0 on no, 1 on yes, -1 on failure. */

static int

check_can_bind_low_ports(void)

  memset(&sin, 0, sizeof(sin));

  sin.sin_family = AF_INET;

  for (port = 600; port < 1024; ++port) {

  for (port = PORT_TEST_RANGE_START; port < PORT_TEST_RANGE_END; ++port) {

    sin.sin_port = htons(port);

    tor_socket_t fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

    if (! SOCKET_OK(fd)) {

      /* Succeed if we can do a setuid with capability retention, and doing so

       * does not make us lose the ability to bind low ports */

    {

      int keepcaps = (test_id == TEST_SETUID_KEEPCAPS);

      const int keepcaps = (test_id == TEST_SETUID_KEEPCAPS);

      okay = switch_id(username, keepcaps ? SWITCH_ID_KEEP_BINDLOW : 0) == 0;

      if (okay) {

        /* Only run this check if there are ports we may not be able to bind

         * to. */

        const uint16_t min_port = unprivileged_port_range_start();

        if (min_port >= PORT_TEST_RANGE_START &&

            min_port < PORT_TEST_RANGE_END) {

          okay = check_can_bind_low_ports() == keepcaps;

        } else {

          fprintf(stderr,

                  "Skipping check for whether we can bind to any "

                  "privileged ports as the user system seems to "

                  "allow us to bind to ports even without any "

                  "capabilities set.\n");

        }

      }

      break;

    }