The test idles on the login page for more than the 60s authorize
timeout. When running cockpit-session via unix socket, this causes some
unsightly "session timed out during authentication" messages. This ought
to be handled better in cockpit-ws, but for the time being ignore these
messages.

Stop failing with "didn't receive expected authorize message", as that's
confusing -- the user did nothing wrong. Instead, silently exit
successfully, and let cockpit-ws handle the timeout.

This is mostly occurring when enabling Negotiate (kerberos)
authentication, and thus cockpit-ws always starts *two* cockpit-session
attempts (one for Negotiate, one for PAM), like in
TestIPA.testQualifiedUsers.

This makes it easier for callers to treat the reply as textual string.
The only remaining user is cockpit-session, where we will need this
behaviour in the following commit.

We want to parse more fields than just "response" from the authorize message in
the message. So remove the very rigidly harcoded parsing in
`read_authorize_response()` and let it return the whole JSON string instead.
Add a new `get_authorize_key()` function that parses a single value from that,
and adjust the callers accordingly.

This is a very restricted parser to keep things simple: No spaces in the
structure, and no escaping. We can assume all that as cockpit-ws sends
very controlled messages, and '"' isn't used in base64 values. In the
worst case we get a truncated value, which will just fail
authentication.

Localize some variables while we are at it.

Drop the duplicated (but not identical!) implementation of
`read_authorize_response()` and use the real implementation.

Run socket-activated cockpit-session with correct context. By default it
is `init_t`, but that will produce a memfd with the wrong permissions, which
the session cannot read.

Allow cockpit-ws to connect to /run/cockpit/session.

Allow restricted user_t and sysadm_t sessions to communicate (but not
connect) to cockpit-ws through the session unix socket. (Covered by
TestLogin.testSELinuxRestrictedUser)

…codes

cockpit-session directly exits with 5 on authentication failures,
including `authentication-unavailable`; or with 127 on authentication
timeouts. It also forwards the bridge child's non-zero exit status,
which is 1 in the common case of e.g. an unhandled exception.

None of these are a reason to mark the unit as failed.

The point of this is really to determine the cgroup of our caller, i.e.
the cockpit-ws process. With [email protected] this is different
than cockpit-session's own cgroup. Rename the variables to clarify this.

If cockpit-ws directly spawns cockpit-session, it can process the 127
exit code by itself. But there is no exit code if that happens via unix
socket. Check this condition explicitly and report `no-cockpit` via the
protocol.

This triggers a more specific error path in cockpit-ws and the login
page, adjust TestConnection.testBasic accordingly.

The various perform_*() functions all assume a non-NULL rhost, as
several functions such as `btmp_log()` do unchecked strncpy() on them.
Add assertions to (1) make them fail more gracefully and usefully), and
(2) document that requirement more explicitly.

This is currently guaranteed by having an explicit fallback to `""` if
`$COCKPIT_REMOTE_PEER` isn't set.

cockpit_session_launch() doesn't set this env if the remote host is
unknown. That is never the case in practice at least in our tests, but
callers should still be aware of it.

Passing the remote peer from ws to cockpit-session via the
`$COCKPIT_REMOTE_PEER` environment variable does not work in unix socket mode.
So make that part of the protocol instead and attach it to the authorize
response.

When cockpit-session's stdin is a Unix socket, it is being spawned
by cockpit-ws through [email protected]. In that case it doesn't
make sense to look at its own cgroup, but we need to check the cgroup of
the socket peer (i.e. cockpit-ws).

We must guard against PID recycling attacks:

1. Eve logs into cockpit, gets ws pid E, and hacks ws: connect to
   session, forks, keeps the session fd in a different process, and
   kills pid E.

3. Eve waits until Alice logs in again and happens to get ws pid E
   (which can happen with a sufficient number of forks, social
   engineering, and some luck). cockpit-session checks that pid E
   is in cgroup /cockpit/alice, and starts an alice session for Eve's
   ws. (Note: SO_PEERCRED gives you pid/uid/gid at the time connect()
   was made.)

Thus require that the peer (ws) must have started earlier than
cockpit-session. This is the same approach that polkit uses as a
fallback if pidfds are not available:
https://github.com/polkit-org/polkit/blob/main/src/polkit/polkitunixprocess.c

Note that pidfds don't help us: There is no API to directly get from a
pidfd to a cgroup, startup time, or /proc/<pid> dirfd, this has to
happen via `pidfd_getpid()` and opening /proc/pid. But that's exactly
what we want to avoid, and thus is pointless (they are also only
available since kernel 6.5).

ws times out the authorization attempt after one minute
(`cockpit_ws_auth_response_timeout`). Introduce a similar timeout on the
session side. This makes PID recycling attacks harder, as their victim
now has to log in within one minute.

Just like in cockpit-wsinstance-*.socket

Unless it's otherwise specified in the configuration file, we now spawn
cockpit-session by connecting to /run/cockpit/session if that exists.
Fall back to calling cockpit-session directly for custom setups.

We leave the cockpit_ws_session_program variable in place to allow the
tests to override things.

Update the unit files for cockpit-ws to ensure that the socket is
available when cockpit-ws is running.

Adjust TestConnection.testBasic accordingly: When running
cockpit-session via unix socket activation, its group permissions are
irrelevant. More thoroughly move the binary away and also disable the
socket, to fail both of cockpit-ws' session creation attempts.

Co-Authored-By: Martin Pitt <[email protected]>

systemd spawns this for us now, so we don't need the setuid bit anymore.
Clean up the statoverride in the Debian packaging on upgrades.

However, that means that cockpit-ws cannot be run as
`cockpit-wsinstance` user outside of the unit any more. Adjust our tests
to run it as root instead.