X2Go Bug report logs - #678
File handles not closed properly in x2gocleansessions

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Message #5 received at submit@bugs.x2go.org (full text, mbox, reply):

From: "Matthew L. Dailey" <matthew.l.dailey@dartmouth.edu>

To: submit@bugs.x2go.org

Subject: File handles not closed properly in x2gocleansessions

Date: Thu, 20 Nov 2014 12:09:12 -0500

[Message part 1 (text/plain, inline)]

Package: x2goserver
Version: 4.0.1.18

Greetings,

When x2gocleansessions starts up and forks, it is not properly closing stdin and stdout. This can lead to problems with upstream programs/scripts. For example, if a script calls apt-get upgrade to upgrade the x2goserver package, the postinst script loads x2gocleansessions and since stdin/stdout are not closed, the call will not finish properly.

Looking through bug reports and commits, it looks like there was a bug #441 to fix a similar problem, but this fix looks like it wasn’t correct. Then, commit 336917af0dc087e4540fb3d55eb501d2fa4349be in 4.0.1.15 implemented a more comprehensive fix, but specifically excluded closing stdin and stout.

Attached is a patch to fix a couple of things in this bit of the code:
* Redirect stdin, stdout and stderr to /dev/null - as far as I know, this is best practice for perl daemons and what I have used for years in my own projects
* Test for the existence of the file descriptor before issuing the close - this fixes a race condition where glob opens its own file descriptor to get the list, so this descriptor is gone when the script attempts to close it
* Only capture the file descriptor backreference in the regex
* Send any close failures to syslog

I hope this all makes sense and that this can be incorporated into the code. Let me know if you have any questions or need any other information.

Thanks for all your great work on X2Go!!

-- 
Matthew L. Dailey
Senior Systems Engineer
Thayer School of Engineering
Dartmouth College

--- x2gocleansessions.orig	2014-10-07 00:05:56.000000000 -0400
+++ x2gocleansessions	2014-11-20 10:21:56.312590068 -0500
@@ -130,23 +130,21 @@
 	# close any open file descriptor left open by our parent before the fork
 	my $fd;
 	for (glob "/proc/$$/fd/*") {
-		if ($_ =~ m/\/proc\/(\d+)\/fd\/(\d+)/) {
-			$fd = $2;
-			if ( $fd == 0 ) { next; }
-			if ( $fd == 1 ) { next; }
-			if (POSIX::close($fd)) {
-				print "";
-				#print "Closed:II$_\n";
-			} else {
-				print "";
-				#print "Error Closing:I$_\n";
+		if ( ! -e $_ ) { next; }
+		if ($_ =~ m/\/proc\/\d+\/fd\/(\d+)/) {
+			$fd = $1;
+			if ( $fd < 3 ) { next; }
+			if (! POSIX::close($fd)) {
+				syslog('warning', "Error Closing $_: $!");
 			}
-		} else {
-			print "";
-			#print "ERROR: $_\n";
 		}
 	}

+	# redirect stdin, stdout and stderr
+	open *STDIN, q{<}, '/dev/null';
+	open *STDOUT, q{>>}, '/dev/null';
+	open *STDERR, q{>>}, '/dev/null';
+
 	$SIG{TERM}=\&catch_term;
 	$SIG{CHLD} = sub { wait };

[x2gocleansessions.patch (application/octet-stream, attachment)]

[Message part 3 (text/plain, inline)]

Message #10 received at 678@bugs.x2go.org (full text, mbox, reply):

From: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>

To: 678-submitter@bugs.x2go.org

Cc: control@bugs.x2go.org, 678@bugs.x2go.org

Subject: X2Go issue (in src:x2goserver) has been marked as pending for release

Date: Sat, 22 Nov 2014 15:25:02 +0100 (CET)

tag #678 pending
fixed #678 4.0.1.19
thanks

Hello,

X2Go issue #678 (src:x2goserver) reported by you has been
fixed in X2Go Git. You can see the changelog below, and you can
check the diff of the fix at:

    http://code.x2go.org/gitweb?p=x2goserver.git;a=commitdiff;h=93bcf85

The issue will most likely be fixed in src:x2goserver (4.0.1.19).

light+love
X2Go Git Admin (on behalf of the sender of this mail)

---
commit 93bcf8568a2b347bcc1e142e4315c9ba455c7e6f
Author: Matthew L. Dailey <matthew.l.dailey@dartmouth.edu>
Date:   Sat Nov 22 15:24:16 2014 +0100

    x2gocleansessions: Redirect stdin, stdout and stderr to /dev/null, test for the existence of the file descriptor before issuing the close, only capture the file descriptor backreference in the regex and send any close failures to syslog. (Fixes: #678).

diff --git a/debian/changelog b/debian/changelog
index c0e4300..31a351e 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -79,6 +79,13 @@ x2goserver (4.0.1.19-0x2go1) UNRELEASED; urgency=medium
       "x2gouser".
     + Add to BR: findutils.
 
+  [ Matthew L. Dailey ]
+  * New upstream version (4.0.1.19):
+    - x2gocleansessions: Redirect stdin, stdout and stderr to /dev/null, test
+      for the existence of the file descriptor before issuing the close,
+      only capture the file descriptor backreference in the regex and
+      send any close failures to syslog. (Fixes: #678).
+
  -- Mike Gabriel <mike.gabriel@das-netzwerkteam.de>  Tue, 07 Oct 2014 15:35:38 +0200
 
 x2goserver (4.0.1.18-0x2go1) unstable; urgency=medium

Message #22 received at 678@bugs.x2go.org (full text, mbox, reply):

From: X2Go Release Manager <git-admin@x2go.org>

To: 678-submitter@bugs.x2go.org

Cc: control@bugs.x2go.org, 678@bugs.x2go.org

Subject: X2Go issue (in src:x2goserver) has been marked as closed

Date: Tue, 24 Feb 2015 21:54:11 +0100 (CET)

close #678
thanks

Hello,

we are very hopeful that X2Go issue #678 reported by you
has been resolved in the new release (4.0.1.19) of the
X2Go source project »src:x2goserver«.

You can view the complete changelog entry of src:x2goserver (4.0.1.19)
below, and you can use the following link to view all the code changes
between this and the last release of src:x2goserver.

    http://code.x2go.org/gitweb?p=x2goserver.git;a=commitdiff;h=49c91751e560ad09ab4490cc3bd6687509c05755;hp=724d2eefe399485a71e79c705a0aad125e853230

If you feel that the issue has not been resolved satisfyingly, feel
free to reopen this bug report or submit a follow-up report with
further observations described based on the new released version
of src:x2goserver.

Thanks a lot for contributing to X2Go!!!

light+love
X2Go Git Admin (on behalf of the sender of this mail)

---
X2Go Component: src:x2goserver
Version: 4.0.1.19-0x2go1
Status: RELEASE
Date: Tue, 24 Feb 2015 21:49:22 +0100
Fixes: 405 632 633 638 644 664 668 671 672 675 676 678 697 698 700 712 715 727 728 770
Changes: 
 x2goserver (4.0.1.19-0x2go1) RELEASED; urgency=medium
 .
   [ Mike Gabriel ]
   * New upstream version (4.0.1.19):
     - Use File::Which to detect if sshfs command is available
       before trying to mount a client-side folder.
     - Be a bit more tolerant when trying to detect if a
       desktop icon is to be removed (using regexp, not
       eq).
     - Xsession script: Prevent bash failures when sourcing external bash
       scripts beyond our scope. (Fixes: #632, #675).
     - x2gogetapps: Support scanning of sub-directories when searching for
       .desktop files. We allow to dive down one level into subdirs, we on
       purpose do not recursively dive into the complete subtree. (Fixes: #633).
     - Make man2html an optional tool. Don't fail if it is missing on the
       build system (required for openSUSE/SLES builds).
     - Fix x2goserver-xsession/Makefile on SUSE. Detect SUSE distro and create
       Xsession related directory symlinks (xinitrc.d and Xclients.d).
     - Hack for x2goserver-xsession/Makefile during SUSE builds. If
       directoy /usr/share/doc/packages/brp-check-suse is present, the build env
       is also considered to be a SUSE system.
     - Trigger Xsession code for SUSE systems (look for /etc/SUSE-brand or
       /etc/SuSE-release for SUSE system recognition). (Fixes: #671).
     - x2gosqlitewrapper.c: Fix rpmlint error: no-return-in-nonvoid-function.
       Return the exitcode of execve().
     - Fix gramma in error message (in x2goresume-session).
     - x2gocleansessions: Call x2gormforward also on terminated sessions. This
       will make sure that re-assigned ports are really available on new session
       startup.
     - x2golistsessions(_root): Only update session state in session DB if
       x2goagent's state file really exists. This addresses a problem that occurs
       when x2golistsessions gets called via an x2gobroker-agent. The
       x2golistsessions script may show session states (--all-servers) of
       sessions on other servers that have session states files on their remote
       /tmp dirs. These files are not accessible for that x2golistsessions script
       and should simply be ignored. (Fixes: #638).
     - Provide pam_namespace support for has_agent_state_file() function.
     - Fix missing session list output if state file does not exist on the
       machine that runs x2golistsessions(_root).
     - Accept more verbose "DENY" output from x2godesktopsharing.
     - Make sure that all "su"-to-user-contexts use /bin/sh for wrapping around
       the executed command (in x2gocleansessions and x2golistsessions_root).
     - Also enforce /bin/sh as shell in su command in x2goprint.
     - README.i18n: Add file that explains the translation workflow for
       this package. Thanks to Mark Pedersen-Cook for drafting this file.
     - Make SSH agent forwarding work after having reconnected via SSH and
       having resumed a session. (Fixes: #672). Thanks to Robert Siemer for
       coming up with that idea.
     - Fix cross-user X2Go Desktop Sharing after being broken by implementing
       clipboard mode feature (and probably other code changes).
     - Document session startup / resumption failures (and their reasons) in
       server-side log output.
     - Handle AD domain users gracefully when X2Go is used with SQLite DB
       backend. (Fixes: #664).
     - Improve sanitizer, use 'x2gosid' sanitizer for session IDs everywhere.
       Drop unused 'pnixusername' sanitizer in 4.0.1.x release of X2Go Server.
     - Allow usernames in session IDs of length 48 chars.
     - Start sshfs with a timeout of 30 seconds (because it never finishes if
       something is wrong with the client-side TCP socket). Also remove/unmount
       mountpoints erroneously registered sshfs mountpoints if sshfs command
       times out. Furthermore, print errors to STDERR (not STDOUT). (Fixes:
       #405).
     - Handle execution of ss command from Perl script x2golistdesktops in a way
       that not only works on Debian, but also on Fedora et al. (Fixes: #727).
     - Provide legacy support for old File::Path packages in x2godbadmin.
       (Fixes: #715).
     - Fix wrong evocation of x2gosyslog ("error" -> "err").
     - Use "undef $dbh" instead of "$dbh->disconnect()". Fixes SQLite3 issues on
       SLE 11.x.
     - Only call $dbh->sqlite_busy_timeout() if the $dbh object is capable of
       that. Works around a too-old DBD::SQLite package on SLE 11.x.
     - Legacy for applications (and X2Go scripts) that expect $SSH_CLIENT to be
       set in the X2Go session's environment. (Fixes: #644).
     - Add man page for x2gogetapps. Weave into that a security / disclaimer
       message as proposed by Stefan Baur. (Fixes: #728).
   * debian/control:
     + Add D (x2goserver): libfile-which-perl.
     + Add C (x2goserver: x2godesktopsharing (<< 3.1.1.2-0~). (Fixes: #700).
     + Bump Standards: to 3.9.6. No changes needed.
     + Don't depend on libdb-pg-perl for armhf builds. (Fixes: #712). Thanks to
       Heinrich Schuchardt for providing information on this.
     + Upgrade to D again (bin:package x2goserver): xfonts-base (Fixes: #770).
   * debian/x2goserver.docs:
     + Install README.i18n file into bin:package x2goserver.
   * x2goserver.spec:
     + Add to R: perl(File::Which).
     + Additionally adapt to building on openSUSE/SLES.
     + No shell expansion possible in obs-build, detect perl version only for
       non-SUSE builds.
     + Add to R: x2goserver-xsession.
     + Don't mention /etc/x2go/x2gosql/sql twice (directly and with wildcard).
     + No %{_sysconfdir}/x2go/Xclients.d on SUSE systems.
     + Use %{_localstatedir} instead of %{_sharedstatedir}.
     + Use proper if... then... clauses.
     + For SUSE builds: Add to R: shadow (useradd, groupadd).
     + Replace historical "egrep" with "grep -E".
     + Systemd support for SUSE >= 12.10.
     + Set %defattr macro for every bin:package.
     + SUSE and Fedora/RHEL have different package group names.
     + Add x2goserver-rpmlintrc file to handle some rpmlint errors and warnings.
     + SUSE has openssh, but no openssh-server.
     + Add to R (x2goserver): perl-X2Go-Server.
     + Add to R (diverse): perl(Config::Simple), perl(Switch) and
       perl(Capture::Tiny).
     + Add to R (x2goserver): perl(File::BaseDir).
     + Don't hard-code /var/lib/ in $HOME path of to-be-created user
       "x2gouser".
     + Add to BR: findutils.
     + For Fedora-like systems, don't make x2goserver bin:package authoritative
       for non-X2Go directories. (Fixes: #676).
     + Remove macro call %systemd_pre for Fedora/EPEL-7 builds. No such macro in
       Fedora/RHEL7. (Fixes: 698).
     + Create system user x2gouser with $HOME in /var/lib/x2go. (Fixes: #697).
     + Always set BuildRoot: parameter.
     + BuildRequires: SUSE <= 11.3 has xorg-x11, not xinit.
     + Requires (x2goserver-xsession): SUSE <= 11.3 has xorg-x11, not xinit.
     + No Bashisms in scriptlets.
     + rpmlint requires shared-mime-info at build time on SLE <= 11.3.
     + "%set_permissions" / "%verify_permissions" macros are not know in SLE <=
       11.3. Using "%run permissions" and "%verify permissions" instead.
     + On SUSE, add permissions.d/x2goserver.
     + Fix SQLite wrapper permissions (02775 -> 02755)
     + Use if then clauses for creating user/group x2goprint.
 .
   [ Matthew L. Dailey ]
   * New upstream version (4.0.1.19):
     - x2gocleansessions: Redirect stdin, stdout and stderr to /dev/null, test
       for the existence of the file descriptor before issuing the close,
       only capture the file descriptor backreference in the regex and
       send any close failures to syslog. (Fixes: #678).
 .
   [ Lars Wendler ]
   * New upstream version (4.0.1.19):
     - Use "printf" instead of "echo -n". (Fixes: #668).

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