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/* An example showing how to connect to a server which is
* using TLS encryption.
*
* This requires nbdkit, and psktool from gnutls.
*
* Both libnbd and nbdkit support TLS-PSK which is a
* simpler-to-deploy form of encryption. (Of course
* certificate-based encryption is also supported, but
* it’s harder to make a self-contained example).
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <libnbd.h>
#define TMPDIR "/tmp/XXXXXX"
#define KEYS "keys.psk"
#define USERNAME "alice"
static char dir[] = TMPDIR;
static char keys[] = TMPDIR "/" KEYS;
static char cmd[] =
"psktool -u " USERNAME " -p " TMPDIR "/" KEYS;
/* Remove the temporary keys file when the program
* exits.
*/
static void
cleanup_keys (void)
{
unlink (keys);
rmdir (dir);
}
/* Create the temporary keys file to share with the
* server.
*/
static void
create_keys (void)
{
size_t i;
if (mkdtemp (dir) == NULL) {
perror ("mkdtemp");
exit (EXIT_FAILURE);
}
i = strlen (cmd) - strlen (TMPDIR) - strlen (KEYS) - 1;
memcpy (&cmd[i], dir, strlen (TMPDIR));
memcpy (keys, dir, strlen (TMPDIR));
if (system (cmd) != 0) {
fprintf (stderr, "psktool command failed\n");
exit (EXIT_FAILURE);
}
atexit (cleanup_keys);
}
int
main (int argc, char *argv[])
{
struct nbd_handle *nbd;
char buf[512];
create_keys ();
/* Create the libnbd handle. */
nbd = nbd_create ();
if (nbd == NULL) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* Enable TLS in the client. */
if (nbd_set_tls (nbd, LIBNBD_TLS_REQUIRE) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* Enable TLS-PSK and pass the keys filename. */
if (nbd_set_tls_psk_file (nbd, keys) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* Set the local username for authentication. */
if (nbd_set_tls_username (nbd, USERNAME) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* Run nbdkit as a subprocess, enabling and requiring
* TLS-PSK encryption.
*/
char *args[] = {
"nbdkit", "-s", "--exit-with-parent",
"--tls", "require", "--tls-psk", keys,
"pattern", "size=1M", NULL
};
if (nbd_connect_command (nbd, args) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* Read the first sector. */
if (nbd_pread (nbd, buf, sizeof buf, 0, 0) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* TLS connections must be shut down. */
if (nbd_shutdown (nbd, 0) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* Close the libnbd handle. */
nbd_close (nbd);
exit (EXIT_SUCCESS);
}
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