replace strlen() calls with strnlen() and appropriate maximums

lib/fko_limits.h

@@ -35,6 +35,8 @@
 
 /* Define some limits (--DSS XXX: These sizes need to be reviewed)
 */
+#define MAX_SPA_ENCRYPTED_SIZE     1500
+#define MAX_SPA_CMD_LEN            1400
 #define MAX_SPA_USERNAME_SIZE        64
 #define MAX_SPA_MESSAGE_SIZE        256
 #define MAX_SPA_NAT_ACCESS_SIZE     128
@@ -44,6 +46,7 @@
 #define MAX_SPA_MESSAGE_TYPE_SIZE     2
 
 #define MIN_SPA_ENCODED_MSG_SIZE     36 /* Somewhat arbitrary */
+#define MAX_SPA_ENCODED_MSG_SIZE       MAX_SPA_ENCRYPTED_SIZE
 #define MIN_GNUPG_MSG_SIZE          400
 #define MIN_SPA_FIELDS                6
 #define MAX_SPA_FIELDS               10