Option to set DH key length

src/freedombone-addcert

 UNIT="Freedombone Unit"
 EXTENSIONS=""
 NODH=
+DH_KEYLENGTH=1024
 
 function show_help {
     echo ''
     echo '  -l --location [locn]       Optional location name'
     echo '  -o --organisation [name]   Optional organisation name'
     echo '  -u --unit [name]           Optional unit name'
+    echo '     --dhkey [bits]          DH key length in bits'
     echo '     --nodh ""               Do not calculate DH params'
     echo '     --ca ""                 Certificate authority cert'
     echo ''
     shift
     NODH="true"
     ;;
+    --dhkey)
+    shift
+    DH_KEYLENGTH=${1}
+    ;;
     *)
     # unknown option
     ;;
         -newkey rsa:4096 -keyout /etc/ssl/private/$CERTFILE.key \
         -out /etc/ssl/certs/$CERTFILE.crt
 if [ ! $NODH ]; then
-    openssl dhparam -check -text -5 1024 -out /etc/ssl/certs/$CERTFILE.dhparam
+    openssl dhparam -check -text -5 $DH_KEYLENGTH -out /etc/ssl/certs/$CERTFILE.dhparam
 fi
 chmod 400 /etc/ssl/private/$CERTFILE.key
 chmod 640 /etc/ssl/certs/$CERTFILE.crt