Given the following code containing errors, provide Common Weakness Enumeration (CWE) identifiers and corresponding messages in JSON format. Each identified weakness should have a unique entry in the JSON array.
    Code: _handle_single_connection (int sockin, int sockout)
{
  const char *plugin_name;
  int ret = -1, r;
  struct connection *conn;
  int nworkers = threads ? threads : DEFAULT_PARALLEL_REQUESTS;
  pthread_t *workers = NULL;

  if (backend->thread_model (backend) < NBDKIT_THREAD_MODEL_PARALLEL ||
      nworkers == 1)
    nworkers = 0;
  conn = new_connection (sockin, sockout, nworkers);
  if (!conn)
    goto done;

  lock_request (conn);
  r = backend_open (backend, conn, read_only);
  unlock_request (conn);
  if (r == -1)
    goto done;

  /* NB: because of an asynchronous exit backend can be set to NULL at
   * just about any time.
   */
  if (backend)
    plugin_name = backend->plugin_name (backend);
  else
    plugin_name = "(unknown)";
  threadlocal_set_name (plugin_name);

  /* Prepare (for filters), called just after open. */
  lock_request (conn);
  if (backend)
    r = backend_prepare (backend, conn);
  else
    r = 0;
  unlock_request (conn);
  if (r == -1)
    goto done;

  /* Handshake. */
  if (protocol_handshake (conn) == -1)
    goto done;

  if (!nworkers) {
    /* No need for a separate thread. */
    debug ("handshake complete, processing requests serially");
    while (!quit && connection_get_status (conn) > 0)
      protocol_recv_request_send_reply (conn);
  }
  else {
    /* Create thread pool to process requests. */
    debug ("handshake complete, processing requests with %d threads",
           nworkers);
    workers = calloc (nworkers, sizeof *workers);
    if (!workers) {
      perror ("malloc");
      goto done;
    }

    for (nworkers = 0; nworkers < conn->nworkers; nworkers++) {
      struct worker_data *worker = malloc (sizeof *worker);
      int err;

      if (!worker) {
        perror ("malloc");
        connection_set_status (conn, -1);
        goto wait;
      }
      if (asprintf (&worker->name, "%s.%d", plugin_name, nworkers) < 0) {
        perror ("asprintf");
        connection_set_status (conn, -1);
        free (worker);
        goto wait;
      }
      worker->conn = conn;
      err = pthread_create (&workers[nworkers], NULL, connection_worker,
                            worker);
      if (err) {
        errno = err;
        perror ("pthread_create");
        connection_set_status (conn, -1);
        free (worker);
        goto wait;
      }
    }

  wait:
    while (nworkers)
      pthread_join (workers[--nworkers], NULL);
    free (workers);
  }

  /* Finalize (for filters), called just before close. */
  lock_request (conn);
  if (backend)
    r = backend->finalize (backend, conn);
  else
    r = 0;
  unlock_request (conn);
  if (r == -1)
    goto done;

  ret = connection_get_status (conn);
 done:
  free_connection (conn);
  return ret;
} ; Sample JSON Format Confermily Expected output: "examples" => "cwe": "xxx"; "message": "xxx"
    
 'cwe': ['CWE-406'], 'message': 'server: Wait until handshake complete before calling .open callback

Currently we call the plugin .open callback as soon as we receive a
TCP connection:

  $ nbdkit -fv --tls=require --tls-certificates=tests/pki null \
           --run "telnet localhost 10809"
  [...]
  Trying ::1...
  Connected to localhost.
  Escape character is '^]'.
  nbdkit: debug: accepted connection
  nbdkit: debug: null: open readonly=0       ◀ NOTE
  nbdkit: null[1]: debug: newstyle negotiation: flags: global 0x3
  NBDMAGICIHAVEOPT

In plugins such as curl, guestfs, ssh, vddk and others we do a
considerable amount of work in the .open callback (such as making a
remote connection or launching an appliance).  Therefore we are
providing an easy Denial of Service / Amplification Attack for
unauthorized clients to cause a lot of work to be done for only the
cost of a simple TCP 3 way handshake.

This commit moves the call to the .open callback after the NBD
handshake has mostly completed.  In particular TLS authentication must
be complete before we will call into the plugin.

It is unlikely that there are plugins which really depend on the
current behaviour of .open (which I found surprising even though I
guess I must have written it).  If there are then we could add a new
.connect callback or similar to allow plugins to get control at the
earlier point in the connection.

After this change you can see that the .open callback is not called
from just a simple TCP connection:

  $ ./nbdkit -fv --tls=require --tls-certificates=tests/pki null \
             --run "telnet localhost 10809"
  [...]
  Trying ::1...
  Connected to localhost.
  Escape character is '^]'.
  nbdkit: debug: accepted connection
  nbdkit: null[1]: debug: newstyle negotiation: flags: global 0x3
  NBDMAGICIHAVEOPT
  xx
  nbdkit: null[1]: debug: newstyle negotiation: client flags: 0xd0a7878
  nbdkit: null[1]: error: client requested unknown flags 0xd0a7878
  Connection closed by foreign host.
  nbdkit: debug: null: unload plugin

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>'