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.\" ========================================================================
.\"
.IX Title "nbd_set_tls_username 3"
.TH nbd_set_tls_username 3 "2021-02-09" "libnbd-1.6.1" "LIBNBD"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
nbd_set_tls_username \- set the TLS username
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <libnbd.h>
\&
\& int nbd_set_tls_username (struct nbd_handle *h,
\&                           const char *username);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Set the \s-1TLS\s0 client username.  This is used
if authenticating with \s-1PSK\s0 over \s-1TLS\s0 is enabled.
If not set then the local username is used.
.PP
This function may be called regardless of whether \s-1TLS\s0 is
supported, but will have no effect unless \fBnbd_set_tls\fR\|(3)
is also used to request or require \s-1TLS.\s0
.SH "RETURN VALUE"
.IX Header "RETURN VALUE"
If the call is successful the function returns \f(CW0\fR.
.SH "ERRORS"
.IX Header "ERRORS"
On error \f(CW\*(C`\-1\*(C'\fR is returned.
.PP
Refer to \*(L"\s-1ERROR HANDLING\*(R"\s0 in \fBlibnbd\fR\|(3)
for how to get further details of the error.
.SH "HANDLE STATE"
.IX Header "HANDLE STATE"
The handle must be
newly created,
otherwise this call will return an error.
.SH "VERSION"
.IX Header "VERSION"
This function first appeared in libnbd 1.0.
.PP
If you need to test if this function is available at compile time
check if the following macro is defined:
.PP
.Vb 1
\& #define LIBNBD_HAVE_NBD_SET_TLS_USERNAME 1
.Ve
.SH "EXAMPLE"
.IX Header "EXAMPLE"
This example is also available as \fIexamples/encryption.c\fR
in the libnbd source code.
.PP
.Vb 10
\& /* 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\en");
\&     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\en", nbd_get_error ());
\&     exit (EXIT_FAILURE);
\&   }
\& 
\&   /* Enable TLS in the client. */
\&   if (nbd_set_tls (nbd, LIBNBD_TLS_REQUIRE) == \-1) {
\&     fprintf (stderr, "%s\en", 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\en", nbd_get_error ());
\&     exit (EXIT_FAILURE);
\&   }
\& 
\&   /* Set the local username for authentication. */
\&   if (nbd_set_tls_username (nbd, USERNAME) == \-1) {
\&     fprintf (stderr, "%s\en", 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\en", nbd_get_error ());
\&     exit (EXIT_FAILURE);
\&   }
\& 
\&   /* Read the first sector. */
\&   if (nbd_pread (nbd, buf, sizeof buf, 0, 0) == \-1) {
\&     fprintf (stderr, "%s\en", nbd_get_error ());
\&     exit (EXIT_FAILURE);
\&   }
\& 
\&   /* TLS connections must be shut down. */
\&   if (nbd_shutdown (nbd, 0) == \-1) {
\&     fprintf (stderr, "%s\en", nbd_get_error ());
\&     exit (EXIT_FAILURE);
\&   }
\& 
\&   /* Close the libnbd handle. */
\&   nbd_close (nbd);
\& 
\&   exit (EXIT_SUCCESS);
\& }
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbd_create\fR\|(3),
\&\fBnbd_get_tls_username\fR\|(3),
\&\fBnbd_set_tls\fR\|(3),
\&\fBlibnbd\fR\|(3).
.SH "AUTHORS"
.IX Header "AUTHORS"
Eric Blake
.PP
Richard W.M. Jones
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (C) 2019\-2020 Red Hat Inc.
.SH "LICENSE"
.IX Header "LICENSE"
This library is free software; you can redistribute it and/or
modify it under the terms of the \s-1GNU\s0 Lesser General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
.PP
This library is distributed in the hope that it will be useful,
but \s-1WITHOUT ANY WARRANTY\s0; without even the implied warranty of
\&\s-1MERCHANTABILITY\s0 or \s-1FITNESS FOR A PARTICULAR PURPOSE.\s0  See the \s-1GNU\s0
Lesser General Public License for more details.
.PP
You should have received a copy of the \s-1GNU\s0 Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, \s-1MA 02110\-1301 USA\s0