another small change to eval_patter. I will keep those two evals as i actually don't see any security impact and performance is good enough

app/config/storage.yml

@@ -58,7 +58,7 @@
       - 'organizationalRole'
       - 'MailAlias'
 
-    :dnPat: "cn=#{:user},o=#{:mail|:sub, /.*@/, ''}"
+    :dnPat: "cn=#{:user},o=#{:mail|/.*@/, ''}"
 
     :map:
       :cn: :user
@@ -72,7 +72,7 @@
       - 'person'
       - 'MailAlias'
 
-    :dnPat: "mail=#{:mail},o=#{:mail|:sub, /.*@/, ''}"
+    :dnPat: "mail=#{:mail},o=#{:mail|/.*@/, ''}"
 
     :map:
       :sn: :surname
@@ -87,7 +87,7 @@
       - 'person'
       - 'MailAccount'
 
-    :dnPat: "mail=#{:mail},o=#{:mail|:sub, /.*@/, ''}"
+    :dnPat: "mail=#{:mail},o=#{:mail|/.*@/, ''}"
 
     :map:
       :homedirectory: :home

app/storage/config.rb

@@ -19,30 +19,24 @@ class DsAdmin::Storage::Config
 
   ##
   # replace special patterns within config strings with data
-  # given by the data hash param. These patterns also allow to send
-  # a message to the actual substituted data to do any kind of
-  # conversion to it.
+  # given by the data hash param. These patterns also allow to 
+  # substitute part of the data giving the argument for a
+  # String#sub call after a | to it.
   #
   # actually this is used within the handling of the ldap specific
   # :dnPat config parameter to generate the dn entry for a given model
   # Data (create or replace)
   #
-  # TODO: I would like to get rid of the eval statements but i don't know
-  # a better way to build the correct objects from the config strings
-  #
   def eval_pattern(pattern, data = {})
     scan_exp = /([^#]*)(#\{(:[^}|]+)(\|([^}]*))?\})?/
 
     result = String.new
     pattern.scan(scan_exp) do |m|
-      key = (eval m[2]) if m[2]
-      val = data[key] if data[key]
+      key = eval m[2] if m[2]
+      msg = eval '[:sub, ' + m[4] + ']' if m[4]
 
-      args = m[4].split(',').map do |arg|
-        eval arg.strip
-      end if m[4]
-
-      val = val.send *args if args
+      val = data[key] if data[key]
+      val = val.send *msg if msg
 
       result += m[0] + (val || "")
     end