20230919.00

Cert based authentication (#116)

* test: align CXX Flags

* sshca: Make the implementation more C++ like

Introduce a oslogin_sshca namespace, remove the C de mangling extern.

* sshca: Add a SysLog wrapper

With this patch now we can have a global sys logger having the logging
points present whether the sys logger has been setup/initialized or not.

For unit tests for example we'll not have it initialized rendering into
no-op calls to SysLogErr().

* oslogin_utils: introduce AuthorizeUser() API

The AuthorizeUser() API merges together the authorization operations
for both login and adminLogin authorize policies. This API is meant
to be used in single points of Authorization - where both login &
adminLogin are attempted/processed.

* sshca: move it out of pam dir

As we are moving authorization out of pam modules it makes sense to
have oslogin_sshca.o in the root dir of src side-by-side with
oslogin_utils.o.

* pam: start disabling the use of oslogin_sshca

Start disaging the use of oslogin_sshca in the pam modules.

* sshca: consider sshca API to assume a cert only

In a model using AuthorizedPrincipalsCommand we can handle a ssh cert
only - not having to split and ignore method and algorithm tokens.

* authorized principals: introduce the new command

* authorize keys: update to use new APIs

Update both authorized_keys and authorized_keys_sk to use new sys logger
facilities as well as AuthorizeUser().

* pam modules: remove pam_*_admin and update pam_*_login

pam_oslogin_admin is not required anymore and pam_oslogin_login is
now only responsible to handle 2fa.

* cache_refresh: should be catching by reference.