I suggest adding the following to portal.properties as a possible value.
# The third pattern ensures that passwords have at least 8 characters, including at least one each of an upper and lower case alphabetic, a digit, and a punctuation character, in any order.
...
#passwords.regexptoolkit.pattern=(?=.{8})(?=((.*\\p{Lower}.*\\p{Upper})|(.*\\p{Upper}.*\\p{Lower})))((.*\\p{Alpha}.*\\p{Digit}.*\\p{Punct})|(.*\\p{Alpha}.*\\p{Punct}.*\\p{Digit})|(.*\\p{Digit}.*\\p{Alpha}.*\\p{Punct})|(.*\\p{Digit}.*\\p{Punct}.*\\p{Alpha})|(.*\\p{Punct}.*\\p{Alpha}.*\\p{Digit})|(.*\\p{Punct}.*\\p{Digit}.*\\p{Alpha}))
See post "password regular expressions" in the Installation/Deployment/Setup forum for a java test file for this expression.
