[vinagre] Improve FreeRDP authentication failure handling

[David King <davidk src gnome org>]

commit d7b4f88943e8615d252d27e1efc58cb64a9e1821
Author: Michał Kępień <michal kepien nask pl>
Date:   Wed Jul 27 13:19:52 2016 +0100

    Improve FreeRDP authentication failure handling
    
    The issue is caused by changes introduced by 60dea27. When the RDP
    server refuses TCP connections on the specified port, freerdp_connect()
    causes freerdp_get_last_error() to return 0x2000c.  Due to the way the
    do-while loop is constructed in open_freerdp(), this effectively causes
    freerdp_connect() to be called in an infinite loop, which quickly
    results in a SIGSEGV as FreeRDP does not seem to handle eventfd
    creation failures nicely (these are caused by exceeding the per-process
    limit of open file descriptors).
    
    As the error string for error 0x2000c is "protocol security negotiation
    or connection failure", to at least allow refused connections to be
    handled gracefully, some limit should be enforced on the number of loop
    iterations inside open_freerdp().
    
    https://bugzilla.gnome.org/show_bug.cgi?id=769217

 plugins/rdp/vinagre-rdp-tab.c |   10 ++++------
 1 files changed, 4 insertions(+), 6 deletions(-)
---
diff --git a/plugins/rdp/vinagre-rdp-tab.c b/plugins/rdp/vinagre-rdp-tab.c
index 5bbfca0..476071c 100644
--- a/plugins/rdp/vinagre-rdp-tab.c
+++ b/plugins/rdp/vinagre-rdp-tab.c
@@ -1187,8 +1187,8 @@ open_freerdp (VinagreRdpTab *rdp_tab)
   VinagreTab           *tab = VINAGRE_TAB (rdp_tab);
   GtkWindow            *window = GTK_WINDOW (vinagre_tab_get_window (tab));
   gboolean              success = TRUE;
-  gboolean              authentication_error = FALSE;
   gboolean              cancelled = FALSE;
+  guint                 authentication_errors = 0;
 
   priv->events = g_queue_new ();
 
@@ -1197,14 +1197,12 @@ open_freerdp (VinagreRdpTab *rdp_tab)
 
   do
     {
-      authentication_error = FALSE;
-
       /* Run FreeRDP session */
       success = freerdp_connect (priv->freerdp_session);
       if (!success)
         {
-          authentication_error = freerdp_get_last_error (priv->freerdp_session->context) == 0x20009 ||
-                                 freerdp_get_last_error (priv->freerdp_session->context) == 0x2000c;
+          authentication_errors += freerdp_get_last_error (priv->freerdp_session->context) == 0x20009 ||
+                                   freerdp_get_last_error (priv->freerdp_session->context) == 0x2000c;
 
           cancelled = freerdp_get_last_error (priv->freerdp_session->context) == 0x2000b;
 
@@ -1212,7 +1210,7 @@ open_freerdp (VinagreRdpTab *rdp_tab)
           init_freerdp (rdp_tab);
         }
     }
-  while (!success && authentication_error);
+  while (!success && authentication_errors < 3);
 
   if (!success)
     {