are there "session IDs"?

[Seven Reeds]

Hi,

I am running Ubuntu.

I am writing an executable that pam_exec will call in "session" mode.
It will respond to session open/close events.  It is almost completely
working.  This morning I was testing it using "su" and it was doing
what i expected.  I then started ssh-ing to the machine.  That's when
things became puzzling.

if I "su" while on the machine the PAM_TTY environment variable is
indeed a TTY string and is unique to the "session".  However, if I
treat "ssh" like "su" and try to ssh to a different user on the same
machine, ex:

        $ ssh otherUser at this.machine.com

then the PAM_TTY variable just shows "ssh".  If I were logged in
multiple times then all would appear to be on the same "line", so to
speak.

This does make sense I suppose.  The "su" continues to use the tty of
the caller.  The "ssh" will eventually have a new tty.  I am calling
my PAM_EXEC's program very late in the session stack so I assumed that
a tty would be available.

Since the tty is not available, is there a unique session identifier
that I can use?  I have not seen mention of one.

Seven