CMS attributes question

[Julien Stern <julien.stern@xxxxxxxxxxxxx>]

Hi list,

We have a question related to CMS that was raised during an ETSI session 
around the CAdES standard:

we were wondering whether the behavior of an implementation encountering 
an unknown attribute was defined. One line of thinking is that an 
_unsigned_ attribute can be ignored by an implementation, but that the 
signature validation should fail if an unknown _signed_ attribute is 
encountered.

Is this behavior somehow defined in CMS (I did not see it, but I might 
have missed it)?
Otherwise, what do you think? What does your implementation do when it 
encounters an unknown signed attribute?

Regards,

--
Julien