TLS support for VNC Websockets

Added TLS support to the VNC QEMU Websockets implementation.
VNC-TLS needs to be enabled for this feature to be used.

The required certificates are specified as in case of VNC-TLS
with the VNC parameter "x509=<path>".

If the server certificate isn't signed by a rooth authority it needs to
be manually imported in the browser because at least in case of Firefox
and Chrome there is no user dialog, the connection just gets canceled.

As a side note VEncrypt over Websocket doesn't work atm because TLS can't
be stacked in the current implementation. (It also didn't work before)
Nevertheless to my knowledge there is no HTML 5 VNC client which supports
it and the Websocket connection can be encrypted with regular TLS now so
it should be fine for most use cases.

Signed-off-by: Tim Hardeck <thardeck@suse.de>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Message-id: 1366727581-5772-1-git-send-email-thardeck@suse.de
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

5 files changed, 176 insertions, 42 deletions

diff --git a/ui/vnc-tls.c b/ui/vnc-tls.c
index 8d4cc8e47c..50275de64f 100644
--- a/ui/vnc-tls.c
+++ b/ui/vnc-tls.c
@@ -334,29 +334,38 @@ static int vnc_set_gnutls_priority(gnutls_session_t s, int x509)
 
 int vnc_tls_client_setup(struct VncState *vs,
                          int needX509Creds) {
+    VncStateTLS *tls;
 
     VNC_DEBUG("Do TLS setup\n");
+#ifdef CONFIG_VNC_WS
+    if (vs->websocket) {
+        tls = &vs->ws_tls;
+    } else
+#endif /* CONFIG_VNC_WS */
+    {
+        tls = &vs->tls;
+    }
     if (vnc_tls_initialize() < 0) {
         VNC_DEBUG("Failed to init TLS\n");
         vnc_client_error(vs);
         return -1;
     }
-    if (vs->tls.session == NULL) {
-        if (gnutls_init(&vs->tls.session, GNUTLS_SERVER) < 0) {
+    if (tls->session == NULL) {
+        if (gnutls_init(&tls->session, GNUTLS_SERVER) < 0) {
             vnc_client_error(vs);
             return -1;
         }
 
-        if (gnutls_set_default_priority(vs->tls.session) < 0) {
-            gnutls_deinit(vs->tls.session);
-            vs->tls.session = NULL;
+        if (gnutls_set_default_priority(tls->session) < 0) {
+            gnutls_deinit(tls->session);
+            tls->session = NULL;
             vnc_client_error(vs);
             return -1;
         }
 
-        if (vnc_set_gnutls_priority(vs->tls.session, needX509Creds) < 0) {
-            gnutls_deinit(vs->tls.session);
-            vs->tls.session = NULL;
+        if (vnc_set_gnutls_priority(tls->session, needX509Creds) < 0) {
+            gnutls_deinit(tls->session);
+            tls->session = NULL;
             vnc_client_error(vs);
             return -1;
         }
@@ -364,43 +373,43 @@ int vnc_tls_client_setup(struct VncState *vs,
         if (needX509Creds) {
             gnutls_certificate_server_credentials x509_cred = vnc_tls_initialize_x509_cred(vs->vd);
             if (!x509_cred) {
-                gnutls_deinit(vs->tls.session);
-                vs->tls.session = NULL;
+                gnutls_deinit(tls->session);
+                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;
+            if (gnutls_credentials_set(tls->session, GNUTLS_CRD_CERTIFICATE, x509_cred) < 0) {
+                gnutls_deinit(tls->session);
+                tls->session = NULL;
                 gnutls_certificate_free_credentials(x509_cred);
                 vnc_client_error(vs);
                 return -1;
             }
             if (vs->vd->tls.x509verify) {
                 VNC_DEBUG("Requesting a client certificate\n");
-                gnutls_certificate_server_set_request (vs->tls.session, GNUTLS_CERT_REQUEST);
+                gnutls_certificate_server_set_request (tls->session, GNUTLS_CERT_REQUEST);
             }
 
         } else {
             gnutls_anon_server_credentials_t anon_cred = vnc_tls_initialize_anon_cred();
             if (!anon_cred) {
-                gnutls_deinit(vs->tls.session);
-                vs->tls.session = NULL;
+                gnutls_deinit(tls->session);
+                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;
+            if (gnutls_credentials_set(tls->session, GNUTLS_CRD_ANON, anon_cred) < 0) {
+                gnutls_deinit(tls->session);
+                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);
-        gnutls_transport_set_push_function(vs->tls.session, vnc_tls_push);
-        gnutls_transport_set_pull_function(vs->tls.session, vnc_tls_pull);
+        gnutls_transport_set_ptr(tls->session, (gnutls_transport_ptr_t)vs);
+        gnutls_transport_set_push_function(tls->session, vnc_tls_push);
+        gnutls_transport_set_pull_function(tls->session, vnc_tls_pull);
     }
     return 0;
 }
@@ -414,6 +423,14 @@ void vnc_tls_client_cleanup(struct VncState *vs)
     }
     vs->tls.wiremode = VNC_WIREMODE_CLEAR;
     g_free(vs->tls.dname);
+#ifdef CONFIG_VNC_WS
+    if (vs->ws_tls.session) {
+        gnutls_deinit(vs->ws_tls.session);
+        vs->ws_tls.session = NULL;
+    }
+    vs->ws_tls.wiremode = VNC_WIREMODE_CLEAR;
+    g_free(vs->ws_tls.dname);
+#endif /* CONFIG_VNC_WS */
 }
 
 
diff --git a/ui/vnc-ws.c b/ui/vnc-ws.c
index 3e3020916c..df89315733 100644
--- a/ui/vnc-ws.c
+++ b/ui/vnc-ws.c
@@ -20,6 +20,69 @@
 
 #include "vnc.h"
 
+#ifdef CONFIG_VNC_TLS
+#include "qemu/sockets.h"
+
+static void vncws_tls_handshake_io(void *opaque);
+
+static int vncws_start_tls_handshake(struct VncState *vs)
+{
+    int ret = gnutls_handshake(vs->ws_tls.session);
+
+    if (ret < 0) {
+        if (!gnutls_error_is_fatal(ret)) {
+            VNC_DEBUG("Handshake interrupted (blocking)\n");
+            if (!gnutls_record_get_direction(vs->ws_tls.session)) {
+                qemu_set_fd_handler(vs->csock, vncws_tls_handshake_io,
+                                    NULL, vs);
+            } else {
+                qemu_set_fd_handler(vs->csock, NULL, vncws_tls_handshake_io,
+                                    vs);
+            }
+            return 0;
+        }
+        VNC_DEBUG("Handshake failed %s\n", gnutls_strerror(ret));
+        vnc_client_error(vs);
+        return -1;
+    }
+
+    VNC_DEBUG("Handshake done, switching to TLS data mode\n");
+    vs->ws_tls.wiremode = VNC_WIREMODE_TLS;
+    qemu_set_fd_handler2(vs->csock, NULL, vncws_handshake_read, NULL, vs);
+
+    return 0;
+}
+
+static void vncws_tls_handshake_io(void *opaque)
+{
+    struct VncState *vs = (struct VncState *)opaque;
+
+    VNC_DEBUG("Handshake IO continue\n");
+    vncws_start_tls_handshake(vs);
+}
+
+void vncws_tls_handshake_peek(void *opaque)
+{
+    VncState *vs = opaque;
+    long ret;
+
+    if (!vs->ws_tls.session) {
+        char peek[4];
+        ret = qemu_recv(vs->csock, peek, sizeof(peek), MSG_PEEK);
+        if (ret && (strncmp(peek, "\x16", 1) == 0
+                    || strncmp(peek, "\x80", 1) == 0)) {
+            VNC_DEBUG("TLS Websocket connection recognized");
+            vnc_tls_client_setup(vs, 1);
+            vncws_start_tls_handshake(vs);
+        } else {
+            vncws_handshake_read(vs);
+        }
+    } else {
+        qemu_set_fd_handler2(vs->csock, NULL, vncws_handshake_read, NULL, vs);
+    }
+}
+#endif /* CONFIG_VNC_TLS */
+
 void vncws_handshake_read(void *opaque)
 {
     VncState *vs = opaque;
diff --git a/ui/vnc-ws.h b/ui/vnc-ws.h
index 039a58765c..95c1b0aeae 100644
--- a/ui/vnc-ws.h
+++ b/ui/vnc-ws.h
@@ -74,6 +74,9 @@ enum {
     WS_OPCODE_PONG = 0xA
 };
 
+#ifdef CONFIG_VNC_TLS
+void vncws_tls_handshake_peek(void *opaque);
+#endif /* CONFIG_VNC_TLS */
 void vncws_handshake_read(void *opaque);
 long vnc_client_write_ws(VncState *vs);
 long vnc_client_read_ws(VncState *vs);
diff --git a/ui/vnc.c b/ui/vnc.c
index b90281b77b..89108de223 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -1111,6 +1111,23 @@ void vnc_client_error(VncState *vs)
     vnc_disconnect_start(vs);
 }
 
+#ifdef CONFIG_VNC_TLS
+static long vnc_client_write_tls(gnutls_session_t *session,
+                                 const uint8_t *data,
+                                 size_t datalen)
+{
+    long ret = gnutls_write(*session, data, datalen);
+    if (ret < 0) {
+        if (ret == GNUTLS_E_AGAIN) {
+            errno = EAGAIN;
+        } else {
+            errno = EIO;
+        }
+        ret = -1;
+    }
+    return ret;
+}
+#endif /* CONFIG_VNC_TLS */
 
 /*
  * Called to write a chunk of data to the client socket. The data may
@@ -1132,17 +1149,20 @@ long vnc_client_write_buf(VncState *vs, const uint8_t *data, size_t datalen)
     long ret;
 #ifdef CONFIG_VNC_TLS
     if (vs->tls.session) {
-        ret = gnutls_write(vs->tls.session, data, datalen);
-        if (ret < 0) {
-            if (ret == GNUTLS_E_AGAIN)
-                errno = EAGAIN;
-            else
-                errno = EIO;
-            ret = -1;
+        ret = vnc_client_write_tls(&vs->tls.session, data, datalen);
+    } else {
+#ifdef CONFIG_VNC_WS
+        if (vs->ws_tls.session) {
+            ret = vnc_client_write_tls(&vs->ws_tls.session, data, datalen);
+        } else
+#endif /* CONFIG_VNC_WS */
+#endif /* CONFIG_VNC_TLS */
+        {
+            ret = send(vs->csock, (const void *)data, datalen, 0);
         }
-    } else
+#ifdef CONFIG_VNC_TLS
+    }
 #endif /* CONFIG_VNC_TLS */
-        ret = send(vs->csock, (const void *)data, datalen, 0);
     VNC_DEBUG("Wrote wire %p %zd -> %ld\n", data, datalen, ret);
     return vnc_client_io_error(vs, ret, socket_error());
 }
@@ -1240,6 +1260,22 @@ void vnc_read_when(VncState *vs, VncReadEvent *func, size_t expecting)
     vs->read_handler_expect = expecting;
 }
 
+#ifdef CONFIG_VNC_TLS
+static long vnc_client_read_tls(gnutls_session_t *session, uint8_t *data,
+                                size_t datalen)
+{
+    long ret = gnutls_read(*session, data, datalen);
+    if (ret < 0) {
+        if (ret == GNUTLS_E_AGAIN) {
+            errno = EAGAIN;
+        } else {
+            errno = EIO;
+        }
+        ret = -1;
+    }
+    return ret;
+}
+#endif /* CONFIG_VNC_TLS */
 
 /*
  * Called to read a chunk of data from the client socket. The data may
@@ -1261,17 +1297,20 @@ long vnc_client_read_buf(VncState *vs, uint8_t *data, size_t datalen)
     long ret;
 #ifdef CONFIG_VNC_TLS
     if (vs->tls.session) {
-        ret = gnutls_read(vs->tls.session, data, datalen);
-        if (ret < 0) {
-            if (ret == GNUTLS_E_AGAIN)
-                errno = EAGAIN;
-            else
-                errno = EIO;
-            ret = -1;
+        ret = vnc_client_read_tls(&vs->tls.session, data, datalen);
+    } else {
+#ifdef CONFIG_VNC_WS
+        if (vs->ws_tls.session) {
+            ret = vnc_client_read_tls(&vs->ws_tls.session, data, datalen);
+        } else
+#endif /* CONFIG_VNC_WS */
+#endif /* CONFIG_VNC_TLS */
+        {
+            ret = qemu_recv(vs->csock, data, datalen, 0);
         }
-    } else
+#ifdef CONFIG_VNC_TLS
+    }
 #endif /* CONFIG_VNC_TLS */
-        ret = qemu_recv(vs->csock, data, datalen, 0);
     VNC_DEBUG("Read wire %p %zd -> %ld\n", data, datalen, ret);
     return vnc_client_io_error(vs, ret, socket_error());
 }
@@ -2761,7 +2800,16 @@ static void vnc_connect(VncDisplay *vd, int csock, int skipauth, bool websocket)
 #ifdef CONFIG_VNC_WS
     if (websocket) {
         vs->websocket = 1;
-        qemu_set_fd_handler2(vs->csock, NULL, vncws_handshake_read, NULL, vs);
+#ifdef CONFIG_VNC_TLS
+        if (vd->tls.x509cert) {
+            qemu_set_fd_handler2(vs->csock, NULL, vncws_tls_handshake_peek,
+                                 NULL, vs);
+        } else
+#endif /* CONFIG_VNC_TLS */
+        {
+            qemu_set_fd_handler2(vs->csock, NULL, vncws_handshake_read,
+                                 NULL, vs);
+        }
     } else
 #endif /* CONFIG_VNC_WS */
     {
diff --git a/ui/vnc.h b/ui/vnc.h
index fea39adcc7..6e9921387f 100644
--- a/ui/vnc.h
+++ b/ui/vnc.h
@@ -276,9 +276,12 @@ struct VncState
     VncStateSASL sasl;
 #endif
 #ifdef CONFIG_VNC_WS
+#ifdef CONFIG_VNC_TLS
+    VncStateTLS ws_tls;
+#endif /* CONFIG_VNC_TLS */
     bool encode_ws;
     bool websocket;
-#endif
+#endif /* CONFIG_VNC_WS */
 
     QObject *info;