change session's login shell

List,

I'd like to change a user's shell based on group membership. The group
membership is no problem - that's what pam_listfile is for. Changing
the shell, however, seems non-obvious. I've looked at the source code
of pam_unix and it provides the path to the users login shell
according to /etc/passwd, so it should be possible for a pam module to
set the shell to an arbitrary value, right?

Still, there's no module like this. For those wondering "why", my use
case is users with only scp access on one server and full shell on
another.

-- 
Frank Van Damme
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