3 files changed, 12 insertions, 1 deletions
diff --git a/g10/gpg.c b/g10/gpg.c
index 28e0a9c64..c9ae28c61 100644
--- a/g10/gpg.c
+++ b/g10/gpg.c
@@ -2182,7 +2182,7 @@ set_compliance_option (enum cmd_and_opt_values option)
 static void
 gpg_init_default_ctrl (ctrl_t ctrl)
 {
-  (void)ctrl;
+  ctrl->magic = SERVER_CONTROL_MAGIC;
 }
 
 
diff --git a/g10/gpg.h b/g10/gpg.h
index 3bf023be6..c66358570 100644
--- a/g10/gpg.h
+++ b/g10/gpg.h
@@ -68,11 +68,20 @@ struct tofu_dbs_s;
 typedef struct tofu_dbs_s *tofu_dbs_t;
 
 
+#if SIZEOF_UNSIGNED_LONG == 8
+# define SERVER_CONTROL_MAGIC 0x53616c696e676572
+#else
+# define SERVER_CONTROL_MAGIC 0x53616c69
+#endif
+
 /* Session control object.  This object is passed to most functions to
    convey the status of a session.  Note that the defaults are set by
    gpg_init_default_ctrl(). */
 struct server_control_s
 {
+  /* Always has the value SERVER_CONTROL_MAGIC.  */
+  unsigned long magic;
+
   /* Local data for server.c  */
   struct server_local_s *server_local;
 
diff --git a/g10/import.c b/g10/import.c
index abc811d63..54d649b34 100644
--- a/g10/import.c
+++ b/g10/import.c
@@ -1182,6 +1182,8 @@ impex_filter_getval (void *cookie, const char *propname)
   static char numbuf[20];
   const char *result;
 
+  log_assert (ctrl && ctrl->magic == SERVER_CONTROL_MAGIC);
+
   if (node->pkt->pkttype == PKT_USER_ID
       || node->pkt->pkttype == PKT_ATTRIBUTE)
     {