vnc: support password expire

This patch adds support for expiring passwords to vnc.  It adds a new
vnc_display_pw_expire() function which specifies the time when the
password will expire.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

console.h

@@ -369,6 +369,7 @@ void vnc_display_init(DisplayState *ds);
 void vnc_display_close(DisplayState *ds);
 int vnc_display_open(DisplayState *ds, const char *display);
 int vnc_display_password(DisplayState *ds, const char *password);
+int vnc_display_pw_expire(DisplayState *ds, time_t expires);
 void do_info_vnc_print(Monitor *mon, const QObject *data);
 void do_info_vnc(Monitor *mon, QObject **ret_data);
 char *vnc_display_local_addr(DisplayState *ds);

qemu-common.h

@@ -50,6 +50,9 @@ typedef struct DeviceState DeviceState;
 #if !defined(ENOTSUP)
 #define ENOTSUP 4096
 #endif
+#ifndef TIME_MAX
+#define TIME_MAX LONG_MAX
+#endif
 
 #ifndef CONFIG_IOVEC
 #define CONFIG_IOVEC

ui/vnc.c

@@ -2082,11 +2082,16 @@ static int protocol_client_auth_vnc(VncState *vs, uint8_t *data, size_t len)
     unsigned char response[VNC_AUTH_CHALLENGE_SIZE];
     int i, j, pwlen;
     unsigned char key[8];
+    time_t now = time(NULL);
 
     if (!vs->vd->password || !vs->vd->password[0]) {
         VNC_DEBUG("No password configured on server");
         goto reject;
     }
+    if (vs->vd->expires < now) {
+        VNC_DEBUG("Password is expired");
+        goto reject;
+    }
 
     memcpy(response, vs->challenge, VNC_AUTH_CHALLENGE_SIZE);
 
@@ -2432,6 +2437,7 @@ void vnc_display_init(DisplayState *ds)
 
     vs->ds = ds;
     QTAILQ_INIT(&vs->clients);
+    vs->expires = TIME_MAX;
 
     if (keyboard_layout)
         vs->kbd_layout = init_keyboard_layout(name2keysym, keyboard_layout);
@@ -2503,6 +2509,14 @@ int vnc_display_password(DisplayState *ds, const char *password)
     return 0;
 }
 
+int vnc_display_pw_expire(DisplayState *ds, time_t expires)
+{
+    VncDisplay *vs = ds ? (VncDisplay *)ds->opaque : vnc_display;
+
+    vs->expires = expires;
+    return 0;
+}
+
 char *vnc_display_local_addr(DisplayState *ds)
 {
     VncDisplay *vs = ds ? (VncDisplay *)ds->opaque : vnc_display;

ui/vnc.h

@@ -120,6 +120,7 @@ struct VncDisplay
 
     char *display;
     char *password;
+    time_t expires;
     int auth;
     bool lossy;
 #ifdef CONFIG_VNC_TLS