agent: Allow DBus calls without a proxy present

We allow DBus calls to arbitrary objects without a proxy in the
Object Managere.

Closes #523
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
common: Hold reference to CockpitPipe while emitting signals

While emitting CockpitPipe::read signal, hold a reference to
self, in case the signal handler unrefs the pipe, we can still
act in a coherent manner.

Caught by Travis and Valgrind.
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
common: Backport g_unix_fd_add() and friends

Backport the new g_unix_fd_add() and related functions which
define GSource's for unix fds. This prevents us from having to
define a custom GSource in CockpitPipe.

In addition we'd like to use these sources for the reauthorization
work.

Closes #529
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
ws: Suppress errors about unexpected TLS disconnects

Browsers seem to do this all the time. No use filling up the
server's logs.

Closes #531
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
Remove use of glib-mkenum and enum types

This is an (unfortunate) requirement of distributing code as a
library. However we're not distributing any of our GObject code
as libraries. So remove use of glib-mkenum and all the complexity
it entails.

Closes #532
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
cockpit: Make CockpitTransport an abstract base class

It doesn't need to be an interface. And as an abstract base
class we can have some implementation there.

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
common: Add new CockpitTransport::control signal

This signal is fired when a control message is received by the
transport, and no recv signal handler has processed it. We use it
in the agent, to have multiple handlers for control messages,
but still avoiding parsing and validating them multiple times.

In the case of the web service, since we're mainly forwarding
messages, we don't use this new signal.

Closes #530
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
ws: Fix use of Secure https only cookies

We now have various criteria on whether HTTPS is in use, not just
just whether a certificate is present or not. So make the 'Secure'
flag of cookies track those criteria, and just check if the
connection in use is a TLS connection or not.

In addition fail safe, so and don't use G_IS_TLS_CONNECTION() but
rather the inverse, and rename things, add tests, so if things
change in our TLS implementation this will be caught.

Closes #533
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
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