1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
|
/* 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 <gnutls/gnutls.h>
#include <gnutls/x509.h>
#include "examples.h"
/* A very basic TLS client, with X.509 authentication and server certificate
* verification.
*/
#define MAX_BUF 1024
#define CAFILE "ca.pem"
#define MSG "GET / HTTP/1.0\r\n\r\n"
extern int tcp_connect (void);
extern void tcp_close (int sd);
/* This function will try to verify the peer's certificate, and
* also check if the hostname matches, and the activation, expiration dates.
*/
static int verify_certificate_callback (gnutls_session_t session)
{
unsigned int status;
const gnutls_datum_t *cert_list;
unsigned int cert_list_size;
int ret;
gnutls_x509_crt_t cert;
const char *hostname;
/* 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.
*/
ret = gnutls_certificate_verify_peers2 (session, &status);
if (ret < 0)
{
printf ("Error\n");
return GNUTLS_E_CERTIFICATE_ERROR;
}
if (status & GNUTLS_CERT_INVALID)
printf ("The certificate is not trusted.\n");
if (status & GNUTLS_CERT_SIGNER_NOT_FOUND)
printf ("The certificate hasn't got a known issuer.\n");
if (status & GNUTLS_CERT_REVOKED)
printf ("The certificate has been revoked.\n");
if (status & GNUTLS_CERT_EXPIRED)
printf ("The certificate has expired\n");
if (status & GNUTLS_CERT_NOT_ACTIVATED)
printf ("The certificate is not yet activated\n");
/* Up to here the process is the same for X.509 certificates and
* OpenPGP keys. From now on X.509 certificates are assumed. This can
* be easily extended to work with openpgp keys as well.
*/
if (gnutls_certificate_type_get (session) != GNUTLS_CRT_X509)
return GNUTLS_E_CERTIFICATE_ERROR;
if (gnutls_x509_crt_init (&cert) < 0)
{
printf ("error in initialization\n");
return GNUTLS_E_CERTIFICATE_ERROR;
}
cert_list = gnutls_certificate_get_peers (session, &cert_list_size);
if (cert_list == NULL)
{
printf ("No certificate was found!\n");
return GNUTLS_E_CERTIFICATE_ERROR;
}
/* This is not a real world example, since we only check the first
* certificate in the given chain.
*/
if (gnutls_x509_crt_import (cert, &cert_list[0], GNUTLS_X509_FMT_DER) < 0)
{
printf ("error parsing certificate\n");
return GNUTLS_E_CERTIFICATE_ERROR;
}
if (!gnutls_x509_crt_check_hostname (cert, hostname))
{
printf ("The certificate's owner does not match hostname '%s'\n",
hostname);
return GNUTLS_E_CERTIFICATE_ERROR;
}
gnutls_x509_crt_deinit (cert);
/* notify gnutls to continue handshake normally */
return 0;
}
int
main (void)
{
int ret, sd, ii;
gnutls_session_t session;
char buffer[MAX_BUF + 1];
const char *err;
gnutls_certificate_credentials_t xcred;
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);
gnutls_certificate_set_verify_flags(xcred, GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT);
/* Initialize TLS session
*/
gnutls_init (&session, GNUTLS_CLIENT);
gnutls_session_set_ptr(session, (void*)"my_host_name");
/* Use default priorities */
ret = gnutls_priority_set_direct (session, "PERFORMANCE", &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);
/* connect to the peer
*/
sd = tcp_connect ();
gnutls_transport_set_ptr (session, (gnutls_transport_ptr_t) sd);
/* Perform the TLS handshake
*/
ret = gnutls_handshake (session);
if (ret < 0)
{
fprintf (stderr, "*** Handshake failed\n");
gnutls_perror (ret);
goto end;
}
else
{
printf ("- Handshake was completed\n");
}
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)
{
fprintf (stderr, "*** Error: %s\n", gnutls_strerror (ret));
goto end;
}
printf ("- Received %d bytes: ", ret);
for (ii = 0; ii < ret; ii++)
{
fputc (buffer[ii], stdout);
}
fputs ("\n", stdout);
gnutls_bye (session, GNUTLS_SHUT_RDWR);
end:
tcp_close (sd);
gnutls_deinit (session);
gnutls_certificate_free_credentials (xcred);
gnutls_global_deinit ();
return 0;
}
|
