Scp & sftp with no shell access or restricted access

[Massimo]

Hello,

I need to provide users with sftp and scp access to unix servers without 
the possibility to open a shell on the server.

It would also be useful to give user:
1) restricted shell
2) Chroot sftp/scp access

I need to do this kind of condiguration on HP-UX, Solaris, Linux & AIX.

How can I do? Can I do it with "standard & supported" software or do I 
need external software?

Do you have any ideas?

Best Regards,
                        Massimo