asked on

password validation - no repeating patternsmore than twice in succession

Hi experts:
I have a requirement to validate passwords using the usual criteria, but one interesting one. I must make sure the password does not contain characters repeating more than once in a succession. The password can only be 20 characters long. The requirement means the following:
Legal passwords may contain: abcabc, dd, !&!&, rere

Illegal passwords: abcabcabc, ddd, !&!&!&, rerere

I hope this makes sense. I am working in coldfusion 8. I am trying to use a regular expression, but I think I need to do some sort of recurssion.

Any ideas? Thanks in advance. If you could point me in the right direction, that would be a big help.

Pui_Yun

Hi snix,
Try this regex:
^(.+?)(\1)$
The adobe website has an example of capturing repeating words here:
https://www.adobe.com/livedocs/coldfusion/6/Developing_ColdFusion_MX_Applications_with_CFML/regexp4.htm#1099092

Read the section on using backreferences.

Hope this helps.
P.

kaufmed

I am a bit confused by your requirement, so I am posting two patterns--you can pick which applies to you :)

Both validate that the string is 20 characters.

// This will match if a series of characters
//  are found repeating twice anywhere in
//  the string (e.g. abchelloabcthereabc)
^(?=.*?(.+).*?\1.*?\1.*?).{1,20}$


// This will match if a series of characters
//  are found repeating twice immediately in
//  succession (e.g. abcabcabc)
^(?=.*?(.+)\1\1.*?).{1,20}$

Open in new window

snix123

ASKER

Thank you. I already have the 20 characters limit working. For the second pattern, I think I would just try to use this: ^(?=.*?(.+)\1\1.*?) since I don't need to test the length here. Can't seem to make it work without testing length, too.

I will play around with it. The backreferenceing doc is helping, too.

ASKER CERTIFIED SOLUTION

kaufmed

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

snix123

ASKER

Thanks to all: this is looking pretty good.

kaufmed

NP. Glad to help :)