Espero que isso ajude.
# cat /etc/pam.d/su
auth sufficient pam_rootok.so
auth [default=1 success=ok ignore=ignore] pam_wheel.so trust use_uid group=group1
auth [success=2 default=die] pam_listfile.so item=user sense=allow onerr=fail file=/etc/security/su-group1-access
auth [default=die success=ok ignore=ignore] pam_wheel.so trust use_uid group=group2
auth requisite pam_listfile.so item=user sense=allow onerr=fail file=/etc/security/su-group2-access
auth include system-auth
account sufficient pam_succeed_if.so uid = 0 use_uid quiet
account include system-auth
password include system-auth
session include system-auth
session optional pam_xauth.so
# cat /etc/security/su-group1-access |egrep -v "^#|^$"
oracle
user
# cat /etc/security/su-group2-access |egrep -v "^#|^$"
root
Resposta original: use abaixo
# cat /etc/pam.d/su |egrep -v "^#|^$"
auth sufficient pam_rootok.so
auth [success=2 default=ignore] pam_succeed_if.so use_uid user notingroup group1
auth required pam_wheel.so use_uid group=group1
auth required pam_listfile.so item=user sense=allow onerr=fail file=/etc/security/su-group1-access
auth [success=2 default=ignore] pam_succeed_if.so use_uid user notingroup group2
auth required pam_wheel.so use_uid group=group2
auth required pam_listfile.so item=user sense=allow onerr=fail file=/etc/security/su-group2-access
auth include system-auth
account sufficient pam_succeed_if.so uid = 0 use_uid quiet
account include system-auth
password include system-auth
session include system-auth
session optional pam_xauth.so
# cat /etc/security/su-group1-access |egrep -v "^#|^$"
oracle
user
# cat /etc/security/su-group2-access |egrep -v "^#|^$"
root