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/* This example code is placed in the public domain. */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <gnutls/gnutls.h>
#include <gnutls/dtls.h>
/* A very basic Datagram TLS client, over UDP with X.509 authentication.
*/
#define MAX_BUF 1024
#define CAFILE "/etc/ssl/certs/ca-certificates.crt"
#define MSG "GET / HTTP/1.0\r\n\r\n"
extern int udp_connect(void);
extern void udp_close(int sd);
extern int verify_certificate_callback(gnutls_session_t session);
int main(void)
{
int ret, sd, ii;
gnutls_session_t session;
char buffer[MAX_BUF + 1];
const char *err;
gnutls_certificate_credentials_t xcred;
if (gnutls_check_version("3.1.4") == NULL) {
fprintf(stderr, "GnuTLS 3.1.4 is required for this example\n");
exit(1);
}
gnutls_global_init();
/* X509 stuff */
gnutls_certificate_allocate_credentials(&xcred);
/* sets the trusted cas file */
gnutls_certificate_set_x509_trust_file(xcred, CAFILE,
GNUTLS_X509_FMT_PEM);
gnutls_certificate_set_verify_function(xcred,
verify_certificate_callback);
/* Initialize TLS session */
gnutls_init(&session, GNUTLS_CLIENT | GNUTLS_DATAGRAM);
/* Use default priorities */
ret = gnutls_priority_set_direct(session,
"NORMAL", &err);
if (ret < 0) {
if (ret == GNUTLS_E_INVALID_REQUEST) {
fprintf(stderr, "Syntax error at: %s\n", err);
}
exit(1);
}
/* put the x509 credentials to the current session */
gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, xcred);
gnutls_server_name_set(session, GNUTLS_NAME_DNS, "my_host_name",
strlen("my_host_name"));
/* connect to the peer */
sd = udp_connect();
gnutls_transport_set_int(session, sd);
/* set the connection MTU */
gnutls_dtls_set_mtu(session, 1000);
gnutls_handshake_set_timeout(session,
GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT);
/* Perform the TLS handshake */
do {
ret = gnutls_handshake(session);
}
while (ret == GNUTLS_E_INTERRUPTED || ret == GNUTLS_E_AGAIN);
/* Note that DTLS may also receive GNUTLS_E_LARGE_PACKET */
if (ret < 0) {
fprintf(stderr, "*** Handshake failed\n");
gnutls_perror(ret);
goto end;
} else {
char *desc;
desc = gnutls_session_get_desc(session);
printf("- Session info: %s\n", desc);
gnutls_free(desc);
}
gnutls_record_send(session, MSG, strlen(MSG));
ret = gnutls_record_recv(session, buffer, MAX_BUF);
if (ret == 0) {
printf("- Peer has closed the TLS connection\n");
goto end;
} else if (ret < 0 && gnutls_error_is_fatal(ret) == 0) {
fprintf(stderr, "*** Warning: %s\n", gnutls_strerror(ret));
} else if (ret < 0) {
fprintf(stderr, "*** Error: %s\n", gnutls_strerror(ret));
goto end;
}
if (ret > 0) {
printf("- Received %d bytes: ", ret);
for (ii = 0; ii < ret; ii++) {
fputc(buffer[ii], stdout);
}
fputs("\n", stdout);
}
/* It is suggested not to use GNUTLS_SHUT_RDWR in DTLS
* connections because the peer's closure message might
* be lost */
gnutls_bye(session, GNUTLS_SHUT_WR);
end:
udp_close(sd);
gnutls_deinit(session);
gnutls_certificate_free_credentials(xcred);
gnutls_global_deinit();
return 0;
}
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