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>
diff --git a/ui/vnc.c b/ui/vnc.c
index da70757..495d6d6 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -2082,11 +2082,16 @@
     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 @@
 
     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 @@
     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;
diff --git a/ui/vnc.h b/ui/vnc.h
index 9619b24..4f895be 100644
--- a/ui/vnc.h
+++ b/ui/vnc.h
@@ -120,6 +120,7 @@
 
     char *display;
     char *password;
+    time_t expires;
     int auth;
     bool lossy;
 #ifdef CONFIG_VNC_TLS