1nbd_set_tls_username(3) LIBNBD nbd_set_tls_username(3)
2
6 nbd_set_tls_username - set the TLS username
7
9 #include <libnbd.h>
10 int nbd_set_tls_username (
12 struct nbd_handle *h, const char *username
13 );
14
16 Set the TLS client username. This is used if authenticating with PSK
17 over TLS is enabled. If not set then the local username is used.
18 This function may be called regardless of whether TLS is supported, but
20 will have no effect unless nbd_set_tls(3) is also used to request or
21 require TLS.
22
24 If the call is successful the function returns 0.
25
27 On error -1 is returned.
28 Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
30 of the error.
31 The following parameters must not be NULL: "h", "username". For more
33 information see "Non-NULL parameters" in libnbd(3).
34
36 The handle must be newly created, otherwise this call will return an
37 error.
38
40 This function first appeared in libnbd 1.0.
41 If you need to test if this function is available at compile time check
43 if the following macro is defined:
44 #define LIBNBD_HAVE_NBD_SET_TLS_USERNAME 1
46
48 This example is also available as examples/encryption.c in the libnbd
49 source code.
50 /* An example showing how to connect to a server which is
52 * using TLS encryption.
53 *
54 * This requires nbdkit, and psktool from gnutls.
55 *
56 * Both libnbd and nbdkit support TLS-PSK which is a
57 * simpler-to-deploy form of encryption. (Of course
58 * certificate-based encryption is also supported, but
59 * it’s harder to make a self-contained example).
60 */
61 #include <stdio.h>
63 #include <stdlib.h>
64 #include <string.h>
65 #include <unistd.h>
66 #include <libnbd.h>
68 #define TMPDIR "/tmp/XXXXXX"
70 #define KEYS "keys.psk"
71 #define USERNAME "alice"
72 static char dir[] = TMPDIR;
74 static char keys[] = TMPDIR "/" KEYS;
75 static char cmd[] =
76 "psktool -u " USERNAME " -p " TMPDIR "/" KEYS;
77 /* Remove the temporary keys file when the program
79 * exits.
80 */
81 static void
82 cleanup_keys (void)
83 {
84 unlink (keys);
85 rmdir (dir);
86 }
87 /* Create the temporary keys file to share with the
89 * server.
90 */
91 static void
92 create_keys (void)
93 {
94 size_t i;
95 if (mkdtemp (dir) == NULL) {
97 perror ("mkdtemp");
98 exit (EXIT_FAILURE);
99 }
100 i = strlen (cmd) - strlen (TMPDIR) - strlen (KEYS) - 1;
101 memcpy (&cmd[i], dir, strlen (TMPDIR));
102 memcpy (keys, dir, strlen (TMPDIR));
103 if (system (cmd) != 0) {
105 fprintf (stderr, "psktool command failed\n");
106 exit (EXIT_FAILURE);
107 }
108 atexit (cleanup_keys);
110 }
111 int
113 main (int argc, char *argv[])
114 {
115 struct nbd_handle *nbd;
116 char buf[512];
117 create_keys ();
119 /* Create the libnbd handle. */
121 nbd = nbd_create ();
122 if (nbd == NULL) {
123 fprintf (stderr, "%s\n", nbd_get_error ());
124 exit (EXIT_FAILURE);
125 }
126 /* Enable TLS in the client. */
128 if (nbd_set_tls (nbd, LIBNBD_TLS_REQUIRE) == -1) {
129 fprintf (stderr, "%s\n", nbd_get_error ());
130 exit (EXIT_FAILURE);
131 }
132 /* Enable TLS-PSK and pass the keys filename. */
134 if (nbd_set_tls_psk_file (nbd, keys) == -1) {
135 fprintf (stderr, "%s\n", nbd_get_error ());
136 exit (EXIT_FAILURE);
137 }
138 /* Set the local username for authentication. */
140 if (nbd_set_tls_username (nbd, USERNAME) == -1) {
141 fprintf (stderr, "%s\n", nbd_get_error ());
142 exit (EXIT_FAILURE);
143 }
144 /* Run nbdkit as a subprocess, enabling and requiring
146 * TLS-PSK encryption.
147 */
148 char *args[] = {
149 "nbdkit", "-s", "--exit-with-parent",
150 "--tls", "require", "--tls-psk", keys,
151 "pattern", "size=1M", NULL
152 };
153 if (nbd_connect_command (nbd, args) == -1) {
154 fprintf (stderr, "%s\n", nbd_get_error ());
155 exit (EXIT_FAILURE);
156 }
157 /* Read the first sector. */
159 if (nbd_pread (nbd, buf, sizeof buf, 0, 0) == -1) {
160 fprintf (stderr, "%s\n", nbd_get_error ());
161 exit (EXIT_FAILURE);
162 }
163 /* TLS connections must be shut down. */
165 if (nbd_shutdown (nbd, 0) == -1) {
166 fprintf (stderr, "%s\n", nbd_get_error ());
167 exit (EXIT_FAILURE);
168 }
169 /* Close the libnbd handle. */
171 nbd_close (nbd);
172 exit (EXIT_SUCCESS);
174 }
175
177 nbd_create(3), nbd_get_tls_username(3), nbd_set_tls(3), libnbd(3).
178
180 Eric Blake
181 Richard W.M. Jones
183
185 Copyright Red Hat
186
188 This library is free software; you can redistribute it and/or modify it
189 under the terms of the GNU Lesser General Public License as published
190 by the Free Software Foundation; either version 2 of the License, or
191 (at your option) any later version.
192 This library is distributed in the hope that it will be useful, but
194 WITHOUT ANY WARRANTY; without even the implied warranty of
195 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
196 Lesser General Public License for more details.
197 You should have received a copy of the GNU Lesser General Public
199 License along with this library; if not, write to the Free Software
200 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
201 02110-1301 USA
202libnbd-1.18.1 2023-10-31 nbd_set_tls_username(3)