Re: [Qemu-devel] PATCH 5/8: x509 certificate for server

[Daniel P. Berrange]

This patch adds support for using x509 certificates on the server
end. The server needs a CA certificate, and its own certificate and
private key. A CA revocation list is optional. This this patch the
file names are hardcoded. The next-but-one patch will make them
configurable.

The use of x509 certificates is controlled by the 'x509' flag to
the VNC arg, eg '-vnc :1,tls,x509'. This only provides encryption
of the session, no authentication.

diff -r b5430bd9f883 vnc.c
--- a/vnc.c     Tue Jul 31 11:32:19 2007 -0400
+++ b/vnc.c     Tue Jul 31 11:43:59 2007 -0400
@@ -104,6 +104,14 @@ enum {
     VNC_AUTH_VENCRYPT_X509VNC = 261,
     VNC_AUTH_VENCRYPT_X509PLAIN = 262,
 };
+
+#if CONFIG_VNC_TLS
+#define CA_FILE "ca-cert.pem"
+#define CRL_FILE "ca-crl.pem"
+#define KEY_FILE "key.pem"
+#define CERT_FILE "cert.pem"
+#endif
+
 #endif /* CONFIG_VNC_TLS */
 
 struct VncState
@@ -1369,16 +1377,59 @@ static gnutls_anon_server_credentials vn
 }
 
 
+static gnutls_certificate_credentials_t vnc_tls_initialize_x509_cred(void)
+{
+    gnutls_certificate_credentials_t x509_cred;
+    int ret;
+    struct stat st;
+
+    if ((ret = gnutls_certificate_allocate_credentials(&x509_cred)) < 0) {
+       VNC_DEBUG("Cannot allocate credentials %s\n", gnutls_strerror(ret));
+       return NULL;
+    }
+    if ((ret = gnutls_certificate_set_x509_trust_file(x509_cred, CA_FILE, 
GNUTLS_X509_FMT_PEM)) < 0) {
+       VNC_DEBUG("Cannot load CA certificate %s\n", gnutls_strerror(ret));
+       gnutls_certificate_free_credentials(x509_cred);
+       return NULL;
+    }
+
+    if ((ret = gnutls_certificate_set_x509_key_file (x509_cred, CERT_FILE, 
KEY_FILE,
+                                                    GNUTLS_X509_FMT_PEM)) < 0) 
{
+       VNC_DEBUG("Cannot load certificate & key %s\n", gnutls_strerror(ret));
+       gnutls_certificate_free_credentials(x509_cred);
+       return NULL;
+    }
+
+    if (stat(CRL_FILE, &st) < 0) {
+       if (errno != ENOENT) {
+           gnutls_certificate_free_credentials(x509_cred);
+           return NULL;
+       }
+    } else {
+       if ((ret = gnutls_certificate_set_x509_crl_file(x509_cred, CRL_FILE, 
GNUTLS_X509_FMT_PEM)) < 0) {
+           VNC_DEBUG("Cannot load CRL %s\n", gnutls_strerror(ret));
+           gnutls_certificate_free_credentials(x509_cred);
+           return NULL;
+       }
+    }
+
+    gnutls_certificate_set_dh_params (x509_cred, dh_params);
+
+    return x509_cred;
+}
+
 static int start_auth_vencrypt_subauth(VncState *vs)
 {
     switch (vs->subauth) {
     case VNC_AUTH_VENCRYPT_TLSNONE:
+    case VNC_AUTH_VENCRYPT_X509NONE:
        VNC_DEBUG("Accept TLS auth none\n");
        vnc_write_u32(vs, 0); /* Accept auth completion */
        vnc_read_when(vs, protocol_client_init, 1);
        break;
 
     case VNC_AUTH_VENCRYPT_TLSVNC:
+    case VNC_AUTH_VENCRYPT_X509VNC:
        VNC_DEBUG("Start TLS auth VNC\n");
        return start_auth_vnc(vs);
 
@@ -1429,11 +1480,17 @@ static void vnc_handshake_io(void *opaqu
     vnc_continue_handshake(vs);
 }
 
+#define NEED_X509_AUTH(vs)                           \
+    ((vs)->subauth == VNC_AUTH_VENCRYPT_X509NONE ||   \
+     (vs)->subauth == VNC_AUTH_VENCRYPT_X509VNC ||    \
+     (vs)->subauth == VNC_AUTH_VENCRYPT_X509PLAIN)
+
+
 static int vnc_start_tls(struct VncState *vs) {
     static const int cert_type_priority[] = { GNUTLS_CRT_X509, 0 };
     static const int protocol_priority[]= { GNUTLS_TLS1_1, GNUTLS_TLS1_0, 
GNUTLS_SSL3, 0 };
     static const int kx_anon[] = {GNUTLS_KX_ANON_DH, 0};
-    gnutls_anon_server_credentials anon_cred = NULL;
+    static const int kx_x509[] = {GNUTLS_KX_DHE_DSS, GNUTLS_KX_RSA, 
GNUTLS_KX_DHE_RSA, GNUTLS_KX_SRP, 0};
 
     VNC_DEBUG("Do TLS setup\n");
     if (vnc_tls_initialize() < 0) {
@@ -1454,7 +1511,7 @@ static int vnc_start_tls(struct VncState
            return -1;
        }
 
-       if (gnutls_kx_set_priority(vs->tls_session, kx_anon) < 0) {
+       if (gnutls_kx_set_priority(vs->tls_session, NEED_X509_AUTH(vs) ? 
kx_x509 : kx_anon) < 0) {
            gnutls_deinit(vs->tls_session);
            vs->tls_session = NULL;
            vnc_client_error(vs);
@@ -1475,19 +1532,36 @@ static int vnc_start_tls(struct VncState
            return -1;
        }
 
-       anon_cred = vnc_tls_initialize_anon_cred();
-       if (!anon_cred) {
-           gnutls_deinit(vs->tls_session);
-           vs->tls_session = NULL;
-           vnc_client_error(vs);
-           return -1;
-       }
-       if (gnutls_credentials_set(vs->tls_session, GNUTLS_CRD_ANON, anon_cred) 
< 0) {
-           gnutls_deinit(vs->tls_session);
-           vs->tls_session = NULL;
-           gnutls_anon_free_server_credentials(anon_cred);
-           vnc_client_error(vs);
-           return -1;
+       if (NEED_X509_AUTH(vs)) {
+           gnutls_certificate_server_credentials x509_cred = 
vnc_tls_initialize_x509_cred();
+           if (!x509_cred) {
+               gnutls_deinit(vs->tls_session);
+               vs->tls_session = NULL;
+               vnc_client_error(vs);
+               return -1;
+           }
+           if (gnutls_credentials_set(vs->tls_session, GNUTLS_CRD_CERTIFICATE, 
x509_cred) < 0) {
+               gnutls_deinit(vs->tls_session);
+               vs->tls_session = NULL;
+               gnutls_certificate_free_credentials(x509_cred);
+               vnc_client_error(vs);
+               return -1;
+           }
+       } else {
+           gnutls_anon_server_credentials anon_cred = 
vnc_tls_initialize_anon_cred();
+           if (!anon_cred) {
+               gnutls_deinit(vs->tls_session);
+               vs->tls_session = NULL;
+               vnc_client_error(vs);
+               return -1;
+           }
+           if (gnutls_credentials_set(vs->tls_session, GNUTLS_CRD_ANON, 
anon_cred) < 0) {
+               gnutls_deinit(vs->tls_session);
+               vs->tls_session = NULL;
+               gnutls_anon_free_server_credentials(anon_cred);
+               vnc_client_error(vs);
+               return -1;
+           }
        }
 
        gnutls_transport_set_ptr(vs->tls_session, (gnutls_transport_ptr_t)vs);
@@ -1754,7 +1828,7 @@ int vnc_display_open(DisplayState *ds, c
     VncState *vs = ds ? (VncState *)ds->opaque : vnc_state;
 #if CONFIG_VNC_TLS
     const char *options;
-    int tls = 0;
+    int tls = 0, x509 = 0;
 #endif
 
     vnc_display_close(ds);
@@ -1770,6 +1844,8 @@ int vnc_display_open(DisplayState *ds, c
        options++;
        if (strncmp(options, "tls", 3) == 0)
            tls = 1; /* Require TLS */
+       else if (strncmp(options, "x509", 4) == 0)
+           x509 = 1; /* Require x509 certificates */
     }
 #endif
 
@@ -1781,9 +1857,14 @@ int vnc_display_open(DisplayState *ds, c
        }
 #if CONFIG_VNC_TLS
        if (tls) {
-           VNC_DEBUG("Initializing VNC server with TLS password auth\n");
            vs->auth = VNC_AUTH_VENCRYPT;
-           vs->subauth = VNC_AUTH_VENCRYPT_TLSVNC;
+           if (x509) {
+               VNC_DEBUG("Initializing VNC server with x509 password auth\n");
+               vs->subauth = VNC_AUTH_VENCRYPT_X509VNC;
+           } else {
+               VNC_DEBUG("Initializing VNC server with TLS password auth\n");
+               vs->subauth = VNC_AUTH_VENCRYPT_TLSVNC;
+           }
        } else {
 #endif
            VNC_DEBUG("Initializing VNC server with password auth\n");
@@ -1795,9 +1876,14 @@ int vnc_display_open(DisplayState *ds, c
     } else {
 #if CONFIG_VNC_TLS
        if (tls) {
-           VNC_DEBUG("Initializing VNC server with TLS no auth\n");
            vs->auth = VNC_AUTH_VENCRYPT;
-           vs->subauth = VNC_AUTH_VENCRYPT_TLSNONE;
+           if (x509) {
+               VNC_DEBUG("Initializing VNC server with x509 no auth\n");
+               vs->subauth = VNC_AUTH_VENCRYPT_X509NONE;
+           } else {
+               VNC_DEBUG("Initializing VNC server with TLS no auth\n");
+               vs->subauth = VNC_AUTH_VENCRYPT_TLSNONE;
+           }
        } else {
 #endif
            VNC_DEBUG("Initializing VNC server with no auth\n");

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