The start session method is reworked to pass a response back to the
client.
If the method was successful, a session list entry is created. This
is different to the provious behaviour, where we created the
session list entry unconditionally.
This new arrangement means that we need a different way to avoid
a race condition where two users may try to create a session at the
same time, and end up with the same display. We do this by keeping
track of newly allocated displays as part of the SCP connections. When
we allocate a display, the SCP connection displays are also taken
into account.
Revives the currently unused TerminalServerAdmins group.
Users in this group will eventually have special privileges for session
management. Currently, members of this group will be allowed to
list all sessions with the xrdp-sesadmin command.
Commit 80fab03198 introduced a way to
prevent waitforx going to the network when trying to open a display,
and hence potentially blocking.
This method turned out to be invalidated by libxcb version 1.16 and
1.17
This change adds an explicit check that the Unix socket for the display
in /tmp/.X11-unix/Xn is open before trying to connect to display ':n'.
This has the same effect.
The get_sorted_session_displays() is broken in that it
doesn't produce a sorted list of displays.
The problem is the qsort comparison function which has 2 errors in 4 lines:-
1) The test is the wrong way round (i.e. arg1 < arg2 produces a +ve
result instead of -ve)
2) Subtracting two unsigned ints in C will never return < 0
The broken function has been masked by other display checks which mean
that it is only visible in a few situations:-
1) Starting two sessions very closely to each other may allocate the
same display to both sessions.
2) If /tmp is namespaced, the other display checks do not work, and
more than two sessions cannot be started.
The top level socket directory is now called XRDP_SOCKET_ROOT_PATH.
Below that are user-specific directories referred to with the
XRDP_SOCKET_PATH macro - this name is hard-coded into xorgxrdp and
the audio modules as an environment variable.
XRDP_SOCKET_PATH now looks like $XRDP_SOCKET_ROOT_PATH/<uid>
XRDP_SOCKET_PATH is only writeable by the user, and readable by the user
and the xrdp process.
matt335672