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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 <assert.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
#include "examples.h"
/* A very basic TLS client, with X.509 authentication and server certificate
* verification utilizing the GnuTLS 3.1.x API.
* Note that error recovery is minimal for simplicity.
*/
#define CHECK(x) assert((x) >= 0)
#define LOOP_CHECK(rval, cmd) \
do { \
rval = cmd; \
} while (rval == GNUTLS_E_AGAIN || rval == GNUTLS_E_INTERRUPTED); \
assert(rval >= 0)
#define MAX_BUF 1024
#define CAFILE "/etc/ssl/certs/ca-certificates.crt"
#define MSG "GET / HTTP/1.0\r\n\r\n"
extern int tcp_connect(void);
extern void tcp_close(int sd);
static int _verify_certificate_callback(gnutls_session_t session);
int main(void)
{
int ret, sd, ii;
gnutls_session_t session;
char buffer[MAX_BUF + 1];
gnutls_certificate_credentials_t xcred;
if (gnutls_check_version("3.1.4") == NULL) {
fprintf(stderr,
"GnuTLS 3.1.4 or later is required for this example\n");
exit(1);
}
CHECK(gnutls_global_init());
/* X509 stuff */
CHECK(gnutls_certificate_allocate_credentials(&xcred));
/* sets the trusted cas file
*/
CHECK(gnutls_certificate_set_x509_trust_file(xcred, CAFILE,
GNUTLS_X509_FMT_PEM));
gnutls_certificate_set_verify_function(xcred,
_verify_certificate_callback);
/* If client holds a certificate it can be set using the following:
*
gnutls_certificate_set_x509_key_file (xcred,
"cert.pem", "key.pem",
GNUTLS_X509_FMT_PEM);
*/
/* Initialize TLS session
*/
CHECK(gnutls_init(&session, GNUTLS_CLIENT));
gnutls_session_set_ptr(session, (void *)"www.example.com");
gnutls_server_name_set(session, GNUTLS_NAME_DNS, "www.example.com",
strlen("www.example.com"));
/* use default priorities */
CHECK(gnutls_set_default_priority(session));
#if 0
/* if more fine-graned control is required */
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);
}
#endif
/* put the x509 credentials to the current session
*/
CHECK(gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, xcred));
/* connect to the peer
*/
sd = tcp_connect();
gnutls_transport_set_int(session, sd);
gnutls_handshake_set_timeout(session, GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT);
/* Perform the TLS handshake
*/
do {
ret = gnutls_handshake(session);
} while (ret < 0 && gnutls_error_is_fatal(ret) == 0);
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);
}
LOOP_CHECK(ret, gnutls_record_send(session, MSG, strlen(MSG)));
LOOP_CHECK(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);
}
CHECK(gnutls_bye(session, GNUTLS_SHUT_RDWR));
end:
tcp_close(sd);
gnutls_deinit(session);
gnutls_certificate_free_credentials(xcred);
gnutls_global_deinit();
return 0;
}
/* This function will verify the peer's certificate, and check
* if the hostname matches, as well as the activation, expiration dates.
*/
static int _verify_certificate_callback(gnutls_session_t session)
{
unsigned int status;
int type;
const char *hostname;
gnutls_datum_t out;
/* read hostname */
hostname = gnutls_session_get_ptr(session);
/* This verification function uses the trusted CAs in the credentials
* structure. So you must have installed one or more CA certificates.
*/
CHECK(gnutls_certificate_verify_peers3(session, hostname, &status));
type = gnutls_certificate_type_get(session);
CHECK(gnutls_certificate_verification_status_print(status, type, &out,
0));
printf("%s", out.data);
gnutls_free(out.data);
if (status != 0) /* Certificate is not trusted */
return GNUTLS_E_CERTIFICATE_ERROR;
/* notify gnutls to continue handshake normally */
return 0;
}
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