This patch adds support for requesting and validating client certificates.
In effect the client certificates are being used as the authentication
mechansim, making VNC passwords unccessary, though using a combination of
both is also possible.
The verification of client certificates is enabled using the 'x509verify'
flag to VNC arg eg '-vnc :1,tls,x509verify'
diff -r f8cd8bd742ee vnc.c
--- a/vnc.c Tue Jul 31 11:45:22 2007 -0400
+++ b/vnc.c Tue Jul 31 11:45:30 2007 -0400
@@ -37,7 +37,7 @@
#include <gnutls/x509.h>
#endif /* CONFIG_VNC_TLS */
-// #define _VNC_DEBUG 1
+ #define _VNC_DEBUG 1
#if _VNC_DEBUG
#define VNC_DEBUG(fmt, ...) do { fprintf(stderr, fmt, ## __VA_ARGS__); } while
(0)
@@ -141,6 +141,7 @@ struct VncState
int auth;
#if CONFIG_VNC_TLS
int subauth;
+ int x509verify;
#endif
char challenge[VNC_AUTH_CHALLENGE_SIZE];
@@ -1418,6 +1419,85 @@ static gnutls_certificate_credentials_t
return x509_cred;
}
+static int vnc_validate_certificate(struct VncState *vs)
+{
+ int ret;
+ unsigned int status;
+ const gnutls_datum_t *certs;
+ unsigned int nCerts, i;
+ time_t now;
+
+ VNC_DEBUG("Validating client certificate\n");
+ if ((ret = gnutls_certificate_verify_peers2 (vs->tls_session, &status)) <
0) {
+ VNC_DEBUG("Verify failed %s\n", gnutls_strerror(ret));
+ return -1;
+ }
+
+ if ((now = time(NULL)) == ((time_t)-1)) {
+ return -1;
+ }
+
+ if (status != 0) {
+ if (status & GNUTLS_CERT_INVALID)
+ VNC_DEBUG("The certificate is not trusted.\n");
+
+ if (status & GNUTLS_CERT_SIGNER_NOT_FOUND)
+ VNC_DEBUG("The certificate hasn't got a known issuer.\n");
+
+ if (status & GNUTLS_CERT_REVOKED)
+ VNC_DEBUG("The certificate has been revoked.\n");
+
+ if (status & GNUTLS_CERT_INSECURE_ALGORITHM)
+ VNC_DEBUG("The certificate uses an insecure algorithm\n");
+
+ return -1;
+ } else {
+ VNC_DEBUG("Certificate is valid!\n");
+ }
+
+ /* Only support x509 for now */
+ if (gnutls_certificate_type_get(vs->tls_session) != GNUTLS_CRT_X509)
+ return -1;
+
+ if (!(certs = gnutls_certificate_get_peers(vs->tls_session, &nCerts)))
+ return -1;
+
+ for (i = 0 ; i < nCerts ; i++) {
+ gnutls_x509_crt_t cert;
+ VNC_DEBUG ("Checking certificate chain %d\n", i);
+ if (gnutls_x509_crt_init (&cert) < 0)
+ return -1;
+
+ if (gnutls_x509_crt_import(cert, &certs[i], GNUTLS_X509_FMT_DER) < 0) {
+ gnutls_x509_crt_deinit (cert);
+ return -1;
+ }
+
+ if (gnutls_x509_crt_get_expiration_time (cert) < now) {
+ VNC_DEBUG("The certificate has expired\n");
+ gnutls_x509_crt_deinit (cert);
+ return -1;
+ }
+
+ if (gnutls_x509_crt_get_activation_time (cert) > now) {
+ VNC_DEBUG("The certificate is not yet activated\n");
+ gnutls_x509_crt_deinit (cert);
+ return -1;
+ }
+
+ if (gnutls_x509_crt_get_activation_time (cert) > now) {
+ VNC_DEBUG("The certificate is not yet activated\n");
+ gnutls_x509_crt_deinit (cert);
+ return -1;
+ }
+
+ gnutls_x509_crt_deinit (cert);
+ }
+
+ return 0;
+}
+
+
static int start_auth_vencrypt_subauth(VncState *vs)
{
switch (vs->subauth) {
@@ -1464,6 +1544,16 @@ static int vnc_continue_handshake(struct
VNC_DEBUG("Handshake failed %s\n", gnutls_strerror(ret));
vnc_client_error(vs);
return -1;
+ }
+
+ if (vs->x509verify) {
+ if (vnc_validate_certificate(vs) < 0) {
+ VNC_DEBUG("Client verification failed\n");
+ vnc_client_error(vs);
+ return -1;
+ } else {
+ VNC_DEBUG("Client verification passed\n");
+ }
}
VNC_DEBUG("Handshake done, switching to TLS data mode\n");
@@ -1547,6 +1637,11 @@ static int vnc_start_tls(struct VncState
vnc_client_error(vs);
return -1;
}
+ if (vs->x509verify) {
+ VNC_DEBUG("Requesting a client certificate\n");
+ gnutls_certificate_server_set_request (vs->tls_session,
GNUTLS_CERT_REQUEST);
+ }
+
} else {
gnutls_anon_server_credentials anon_cred =
vnc_tls_initialize_anon_cred();
if (!anon_cred) {
@@ -1808,6 +1903,7 @@ void vnc_display_close(DisplayState *ds)
vs->auth = VNC_AUTH_INVALID;
#if CONFIG_VNC_TLS
vs->subauth = VNC_AUTH_INVALID;
+ vs->x509verify = 0;
#endif
if (vs->lsock != -1) {
close(vs->lsock);
@@ -1842,10 +1938,14 @@ int vnc_display_open(DisplayState *ds, c
options = display;
while ((options = strchr(options, ','))) {
options++;
- if (strncmp(options, "tls", 3) == 0)
+ if (strncmp(options, "tls", 3) == 0) {
tls = 1; /* Require TLS */
- else if (strncmp(options, "x509", 4) == 0)
+ } else if (strncmp(options, "x509verify", 10) == 0) {
+ x509 = 1;
+ vs->x509verify = 1; /* Require x509 certificates & verify client */
+ } else if (strncmp(options, "x509", 4) == 0) {
x509 = 1; /* Require x509 certificates */
+ }
}
#endif
--
|=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=|
|=- Perl modules: http://search.cpan.org/~danberr/ -=|
|=- Projects: http://freshmeat.net/~danielpb/ -=|
|=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|
