Custom Password validation on Drupal 7 form I am using the Drupal Form API for a customized Login System. It has the password field which needs to be validated. We have a custom criteria of Uppercase, Lowercase, numeric and special characters to validate the password. 

The one way I see is to write the RegEx inside the Validate function. Is there an alternate way in Drupal to do this via an existing function or module?

(I am aware that the Webform Validation Module can do this for the webforms.)

Thanks.
Please check Password Policy module. It will satisfy all your above requirements (Uppercase, Lowercase, numeric and special characters).