Authentication according NAS

[ebrnospam at free.fr]

Hello,

I've got this infrastructure : 

FACTORY 1
  NAS1
  NAS2
  NAS3

FACTORY 2
  NAS1
  NAS2
  NAS3
  NAS4

I just want this : 

user admin with password toto could connect to NAS1/2/3/4 of Factory2
user admin with password coco could connect to NAS1/2/3 of Factory1

or if it's more simple :

user admin could connect to NAS1/2/3/4 of Factory2 and NAS1/2/3 of Factory1
user adm_f1 could connect to NAS1/2/3 of Factory1 but can't connect to NAS of Factory2
user adm_f2 could connect to NAS1/2/3/4 of Factory2 but can't connect to NAS of Factory1

How can I do that ?

Thanks

Eric