doc: Update cockpit-transport diagram for recent changes

Closes: #502
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
web: Improve $cockpit.dbus()

* Only put 'release' on the client once.
* Don't put the reference count on the client at all.

Closes: #516
Reviewed-by: Stef Walter <stefw@redhat.com>
ws: Fix minor issue found by coverity

Because asserts can in theory be disabled, we should have a
break statement here.

Closes #515
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
web: Replace 'first_visit' argument with 'setup' method.

To make it clearer that 'setup' is about static
modifications/additions to the DOM, while 'enter' is about filling the
page according to the URL parameters.

A lot of code has been moved, but it has not been changed.

Closes #518
Review-by: Stef Walter <stefw@redhat.com>
ws: Fix race while closing in CockpitSshTransport

The exit-signal or exit-status SSH packets often race with the
close channel packets. We need to wait for them. Add a timeout
during which we wait for exit-signal or exit-status after both
the incoming and outgoing close packets have been received.

Caught by Valgrind and Travis CI

Closes #520
ws: Create CockpitCreds closer to pam_authenticate()

Create the PAM creds closer to pam_authenticate(), so we can use
the real user that PAM canonicalized, as well as return additional
information into the creds (later).

Remove the noop authorization check. We want to be respecting
system authorization, not inventing our own.
ws: Remove the cockpit_creds_take_password() function

It's not used, and not useful going forward.
ws: CockpitCreds with multi creds, remote host is a cred

As part of the build up to GSSAPI kerberos support we need to be
able to hold mulitple credentials in the aptly named CockpitCreds.

Move remote host credential to CockpitCreds. This is necessary
because we want to authenticate in cockpit-session and perform
that authentication from CockpitAuth
agent: Drop group privileges in cockpit-session

Correctly drop group privileges in cockpit session.

Fix #492
agent: Use err() and warn() in cockpit-session

Since cockpit-session is written without GLib, we can't use the
standard GLib logging, but we can use these stdlib functions for
handling printing our errors.
agent: Some minor cleanup in cockpit-session

Move global variables to top, and make some variables static rather
than global.
agent: Don't lookup the user twice in cockpit-session
agent: Return a proper error status if can't execute cockpit-agent

Fixes #498
agent: Set enviroment variables from PAM in cockpit-session

Don't let the cockpit-ws environment leak into cockpit-agent. Use
PAM to get the environment variable for the new process.

Fixes #497
common: Add 'problem' property to CockpitPipe

This can be used to retrieve the problem that the pipe closed
with, or NULL. But more importantly, it can be used to construct
a CockpitPipe for a failure.

Since CockpitPipe guarantees that it won't fire it's close
signals until the main loop, we follow that same guarantee
here with the "problem" property on construct.
ws: Allow CockpitCreds to be used as hash table key
ws: Run PAM authentication in cockpit-session process

The PAM modules are not necessarily thread-safe. In addition we
really want to run the 'auth' and 'session' stacks in the same
process, so later work with reauthorizing the agent can kick in.

This means sharing a cockpit-session process between the CockpitAuth
code and webservice code.

cockpit-session now accepts a '-p FD' argument, which tells it to
read a password from that FD, authenticate, and return the results
back on the same FD.

In the future we'll also want cockpit-session to return any kerberos
TGT it got during opening the session back to cockpit-ws, so we can
use store that TGT in the user's credentials, and use it to connect
to other servers.

Unfortunately we cannot use CockpitPipe to start the process in
CockpitAuth because of the way that CockpitWebServer runs handlers in
different threads (for now). So implement a simple work around and
create the CockpitPipe once in the websocket thread.

Closes #509