What kind of regex does the Transform AttributeResolver use?

[Peter Schober]

* Ferenc Wágner <wferi at niif.hu> [2018-07-28 18:43]:
> While experimenting with transforming attributes under SP 2.6, I found
> that the following two transformations don't behave the same:
> 
> <AttributeResolver type="Transform" source="eppn">
>     <Regex match=".+" dest="fakeEntitlementPlus">viewers</Regex>
>     <Regex match=".*" dest="fakeEntitlementStar">viewers</Regex>
> </AttributeResolver>
> 
> When fed by an arbitrary eppn, the .+ rule creates
> fakeEntitlementPlus=viewers as expected, while the .* rule creates an
> empty fakeEntitlementStar and logs the message:
> 
> 2018-07-28 17:39:24 ERROR Shibboleth.AttributeResolver.Transform
> [6]: caught error applying regular expression: replace pattern
> cannot match zero-length string

".*" (with zero or more occurances of a single char) could also be a
zero-length string, seems there exists some code that doesn't like
that?

> (I was also got by the operation being applied repeatedly/globally:
> match="." resulted in viewersviewersviewersviewers... to my surprise.)

Always anchor your regexes.

-peter