diff --git a/common/os/tls.h b/common/os/tls.h
new file mode 100644
index 0000000..a6d09da
--- /dev/null
+++ b/common/os/tls.h
@@ -0,0 +1,49 @@
+/* Copyright (C) 2011 TightVNC Team.  All Rights Reserved.
+ *
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this software; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+ * USA.
+ */
+
+#ifndef OS_TLS_H
+#define OS_TLS_H
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#ifdef HAVE_GNUTLS
+#include <gnutls/gnutls.h>
+
+#ifndef HAVE_GNUTLS_X509_CRT_PRINT
+#ifdef WIN32
+#error "Please install more recent GNUTLS with gnutls_x509_crt_print() function"
+#endif
+
+typedef enum {
+	GNUTLS_CRT_PRINT_ONELINE = 1
+} gnutls_certificate_print_formats_t;
+
+/*
+ * Prints certificate in human-readable form.
+ */
+int
+gnutls_x509_crt_print(gnutls_x509_crt_t cert,
+		      gnutls_certificate_print_formats_t format,
+		      gnutls_datum_t * out);
+#endif /* HAVE_GNUTLS_X509_CRT_PRINT */
+#endif /* HAVE_GNUTLS */
+
+#endif /* OS_TLS_H */
+