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
|
/* 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 <assert.h>
#include "examples.h"
#define CHECK(x) assert((x)>=0)
/* This function will verify the peer's certificate, check
* if the hostname matches. In addition it will perform an
* SSH-style authentication, where ultimately trusted keys
* are only the keys that have been seen before.
*/
int _ssh_verify_certificate_callback(gnutls_session_t session)
{
unsigned int status;
const gnutls_datum_t *cert_list;
unsigned int cert_list_size;
int ret, type;
gnutls_datum_t out;
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.
*/
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;
/* Do SSH verification */
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;
}
/* service may be obtained alternatively using getservbyport() */
ret = gnutls_verify_stored_pubkey(NULL, NULL, hostname, "https",
type, &cert_list[0], 0);
if (ret == GNUTLS_E_NO_CERTIFICATE_FOUND) {
printf("Host %s is not known.", hostname);
if (status == 0)
printf("Its certificate is valid for %s.\n",
hostname);
/* the certificate must be printed and user must be asked on
* whether it is trustworthy. --see gnutls_x509_crt_print() */
/* if not trusted */
return GNUTLS_E_CERTIFICATE_ERROR;
} else if (ret == GNUTLS_E_CERTIFICATE_KEY_MISMATCH) {
printf
("Warning: host %s is known but has another key associated.",
hostname);
printf
("It might be that the server has multiple keys, or you are under attack\n");
if (status == 0)
printf("Its certificate is valid for %s.\n",
hostname);
/* the certificate must be printed and user must be asked on
* whether it is trustworthy. --see gnutls_x509_crt_print() */
/* if not trusted */
return GNUTLS_E_CERTIFICATE_ERROR;
} else if (ret < 0) {
printf("gnutls_verify_stored_pubkey: %s\n",
gnutls_strerror(ret));
return ret;
}
/* user trusts the key -> store it */
if (ret != 0) {
CHECK(gnutls_store_pubkey(NULL, NULL, hostname, "https",
type, &cert_list[0], 0, 0));
}
/* notify gnutls to continue handshake normally */
return 0;
}
|
