Add a new package radius-shell with a setcap radius_shell front end

Ticket: CM-19457
Reviewed By: nobody
Testing Done:  multiple logins, separately and simultaneously

Because we can't determine privilege level separately and up front with
the RADIUS protocol, unlike TACACS+, we wind up with all logins as the
same unprivileged radius uid.  But we can set the auid (accounting or
auditing uid) correctly, and a separate setcap radius_shell can be set as
the login shell, and can fixup the uid before running /bin/bash.

To set the auid correctly, we need to know the privileged radius user
account.  Added mapped_priv_user to the configuration file to handle
that.  mapped_priv_user has to match the account used by libnss-mapuser.
That's a bit ugly, but a common config file would be uglier.

The radius shell is in a new package, since it has binaries. The new
package is radius-shell.  In it's post actions, it changes the radius
users shell to radius_shell if they are present, and back to /bin/bash
on package removal.   It uses capabilities, tries to be very restrictive
in what it changes, and depends on being installed setcap cap_setuid

Make the existing libpam-radius-auth package depend on radius-shell, so
it will pull in the new package on upgrades.

Also fixed another issue with reparsing changed config file, have to
handle case where there were servers defined, but aren't any longer.

1 files changed, 11 insertions, 2 deletions

diff --git a/debian/control b/debian/control
index b70c948..b8022db 100644
--- a/debian/control
+++ b/debian/control
@@ -3,13 +3,22 @@ Maintainer: dev-support <dev-support@cumulusnetworks.com>
 Section: libs
 Priority: extra
 Standards-Version: 3.9.6
-Build-Depends: libpam0g-dev | libpam-dev, debhelper (>= 9~), libaudit-dev
+Build-Depends: libpam0g-dev | libpam-dev, debhelper (>= 9~), libaudit-dev, libcap-dev
 
 Package: libpam-radius-auth
 Architecture: any
-Depends: ${shlibs:Depends}, ${misc:Depends}, libaudit1
+Depends: ${shlibs:Depends}, ${misc:Depends}, libaudit1, radius-shell
 Description: PAM RADIUS client authentication module
  This is the PAM to RADIUS authentication module. It allows any PAM-capable
  machine to become a RADIUS client for authentication and accounting
  requests. You will, however, need to supply your own RADIUS server to
  perform the actual authentication
+
+Package: radius-shell
+Architecture: any
+Depends: ${shlibs:Depends}, ${misc:Depends}, libaudit1, libcap2-bin, libcap2, libnss-mapuser
+Description: Shell front-end used for radius users.
+ This provides a uid fixup program.  Due to the limitations of the
+ RADIUS protocol, we can't tell whether a user is privileged until
+ after authentication.  This packages provides a shell front-end that
+ sets the uid to the auid, if set and > 1000, and not already matching.