password check with RegEx

neutcomp · January 6th, 2009, 10:56 AM

Is it possible the following:

Password must contain at least two of the following groups:
- Small letters (a-z)
- Capital letters (A-Z)
- Numbers (0-9)
- Strange charakters (!@#$%^&*_+-/)

I only can find regex's that do and, and, and ...
Hope to here from you all

Bjorn

Old Pedant · January 7th, 2009, 02:06 AM

I think you could do it, but it would be a LOOOONNNNG regexp.

Something like (in JavaScript syntax)

Code:

/((?=[A-Z])(?=[a-z])|(?=[A-Z])(?=\d)|(?=[a-z])(?=\d)|....)/

That is, you'd have to include every possible pair of your 4 sets of characters...so 6 possible pairs.

Unless you are dead set on doing this all in a single expresssion, it would be easier to just have an "or" of the 4 possibilities and then capture all the matches and ensure that you have at least 2 matches. Depending on what "outside" language you are using, this would be trivial.

Hmmm???

Old Pedant · January 7th, 2009, 02:24 AM

I couldn't get it to work right using "look ahead" (surely something silly I was doing wrong), but I got it to work by sheer brute force:

Code:

<script>
// there are no spaces or line breaks in the assignment here
// even if the forum software puts some in:
var re = 
/([A-Z][A-Z\d\!\@\#]*[a-z]|[a-z][a-z\d\!\@\#]*[A-Z]|[A-Z][A-Za-z\!\@\#\$\%]*\d|\d[A-Za-z\!\@\#\$\%]*[A-Z]|[a-z][A-Za-z\!\@
\#\$\%]*\d|\d[A-Za-z\!\@\#\$\%]*[a-z]|[a-z][A-Za-z\d]*[\!\@\@]|[\!\@\@][A-Za-z\d]*[a-z]|[A-Z][A-Za-z\d]*[\!\@\@]|[\!\@\@][A-Za-z\d]*[A-Z]|\d[A-Za-z\d]*[\!\@\@]|[\!\@\@][A-Za-z\d]*\d)/

function check(fld)
{
    alert( re.test(fld.value) );
}
</script>
<form>
<input name=foo onChange="check(this);">
<input name=bar onChange="check(this);">
</form>

I only show using 3 of your special characters, to keep it to reasonable size, but you can easily just expand the choices.

Seems to work like a charm.

neutcomp · January 7th, 2009, 03:52 AM

Wauw! You did a good job my friend!

Thanks for the excellent example.

neutcomp · January 7th, 2009, 07:10 AM

I have here the compleet regex with all strange charakters.

^(?=.*[A-Z])(?=.*[a-z])[a-zA-Z\d!@#$%^&_|\-=+?~(){}:;/.,<>*`']{6,}$|^(?=.*[A-Z])(?=.*\d)[a-zA-Z\d!@#$%^&_|\-=+?~(){}:;/.,<>*`']{6,}$|^(?=.*[a-z])(?=.*\d)[a-zA-Z\d!@#$%^&_|\-=+?~(){}:;/.,<>*`']{6,}$|^(?=.*[A-Z])(?=.*[!@#$%^&_|\-=+?~(){}:;/.,<>*`'])[a-zA-Z\d!@#$%^&_|\-=+?~(){}:;/.,<>*`']{6,}$|^(?=.*[!@#$%^&_|\-=+?~(){}:;/.,<>*`'])(?=.*\d)[a-zA-Z\d!@#$%^&_|\-=+?~(){}:;/.,<>*`']{6,}$|^(?=.*[a-z])(?=.*[!@#$%^&_|\-=+?~(){}:;/.,<>*`'])[a-zA-Z\d!@#$%^&_|\-=+?~(){}:;/.,<>*`']{6,}$

Old Pedant · January 7th, 2009, 05:26 PM

Just for anybody reading this:

Some RegEx engines will choke on the ( ) in the [...] list. JS or Perl will choke on the / in there. Possible a few other characters in there that could cause problems in various engines. The solution is easy: When in doubt just put \ in front of each possible problem character. Example:

Code:

[a-zA-Z\d!@#$%^&_|\-=+?~\(\)\{\}:;\/.,<>*`']