do not make PTY slave the controlling terminal

If we have no controlling terminal opening a terminal will make this
terminal our controller, which is a serious problem if this happens to
be the pseudo terminal we created to run dpkg in as we will close this
terminal at the end hanging ourself up in the process…

The offending open is the one we do to have at least one slave fd open
all the time, but for good measure, we apply the flag also to the slave
fd opening in the child process as we set the controlling terminal
explicitely here.

This is a regression from 150bdc9ca5d656f9fba94d37c5f4f183b02bd746 with
the slight twist that this usecase was silently broken before in that it
wasn't logging the output in term.log (as a pseudo terminal wasn't
created).

Closes: 772641

apt-pkg/deb/dpkgpm.cc

@@ -1127,7 +1127,7 @@ void pkgDPkgPM::StartPtyMagic()
 	       on kfreebsd we get an incorrect ("step like") output then while it has
 	       no problem with closing all references… so to avoid platform specific
 	       code here we combine both and be happy once more */
-	    d->protect_slave_from_dying = open(d->slave, O_RDWR | O_CLOEXEC);
+	    d->protect_slave_from_dying = open(d->slave, O_RDWR | O_CLOEXEC | O_NOCTTY);
 	 }
       }
    }
@@ -1159,7 +1159,7 @@ void pkgDPkgPM::SetupSlavePtyMagic()
    if (setsid() == -1)
       _error->FatalE("setsid", "Starting a new session for child failed!");
 
-   int const slaveFd = open(d->slave, O_RDWR);
+   int const slaveFd = open(d->slave, O_RDWR | O_NOCTTY);
    if (slaveFd == -1)
       _error->FatalE("open", _("Can not write log (%s)"), _("Is /dev/pts mounted?"));
    else if (ioctl(slaveFd, TIOCSCTTY, 0) < 0)

test/integration/test-no-fds-leaked-to-maintainer-scripts

@@ -26,20 +26,25 @@ setupaptarchive
 
 rm -f rootdir/var/log/dpkg.log rootdir/var/log/apt/term.log
 testsuccess aptget install -y fdleaks -qq < /dev/null
-msgtest 'Check if fds were not' 'leaked'
-if [ "$(grep 'root root' rootdir/tmp/testsuccess.output | wc -l)" = '8' ]; then
-	msgpass
-else
-	echo
-	cat rootdir/tmp/testsuccess.output
-	msgfail
-fi
 
-cp rootdir/tmp/testsuccess.output terminal.output
-tail -n +3 rootdir/var/log/apt/term.log | head -n -1 > terminal.log
-testfileequal 'terminal.log' "$(cat terminal.output)"
+checkfdleak() {
+	msgtest 'Check if fds were not' 'leaked'
+	if [ "$(grep 'root root' rootdir/tmp/testsuccess.output | wc -l)" = "$1" ]; then
+		msgpass
+	else
+		echo
+		cat rootdir/tmp/testsuccess.output
+		msgfail
+	fi
+}
+checkinstall() {
+	checkfdleak 8
+
+	cp rootdir/tmp/testsuccess.output terminal.output
+	tail -n +3 rootdir/var/log/apt/term.log | head -n -1 > terminal.log
+	testfileequal 'terminal.log' "$(cat terminal.output)"
 
-testequal "startup archives unpack
+	testequal "startup archives unpack
 install $PKGNAME <none> 1.0
 status half-installed $PKGNAME 1.0
 status unpacked $PKGNAME 1.0
@@ -50,22 +55,19 @@ status unpacked $PKGNAME 1.0
 status half-configured $PKGNAME 1.0
 status installed $PKGNAME 1.0
 startup packages configure" cut -f 3- -d' ' rootdir/var/log/dpkg.log
+}
+checkinstall
 
 rm -f rootdir/var/log/dpkg.log rootdir/var/log/apt/term.log
 testsuccess aptget purge -y fdleaks -qq
-msgtest 'Check if fds were not' 'leaked'
-if [ "$(grep 'root root' rootdir/tmp/testsuccess.output | wc -l)" = '12' ]; then
-	msgpass
-else
-	echo
-	cat rootdir/tmp/testsuccess.output
-	msgfail
-fi
-cp rootdir/tmp/testsuccess.output terminal.output
-tail -n +3 rootdir/var/log/apt/term.log | head -n -1 > terminal.log
-testfileequal 'terminal.log' "$(cat terminal.output)"
+checkpurge() {
+	checkfdleak 12
+
+	cp rootdir/tmp/testsuccess.output terminal.output
+	tail -n +3 rootdir/var/log/apt/term.log | head -n -1 > terminal.log
+	testfileequal 'terminal.log' "$(cat terminal.output)"
 
-testequal "startup packages purge
+	testequal "startup packages purge
 status installed $PKGNAME 1.0
 remove $PKGNAME 1.0 <none>
 status half-configured $PKGNAME 1.0
@@ -79,3 +81,13 @@ status config-files $PKGNAME 1.0
 status config-files $PKGNAME 1.0
 status not-installed $PKGNAME <none>
 startup packages configure" cut -f 3- -d' ' rootdir/var/log/dpkg.log
+}
+checkpurge
+
+rm -f rootdir/var/log/dpkg.log rootdir/var/log/apt/term.log
+testsuccess runapt command setsid -w "${BUILDDIRECTORY}/apt-get" install -y fdleaks -qq < /dev/null
+checkinstall
+
+rm -f rootdir/var/log/dpkg.log rootdir/var/log/apt/term.log
+testsuccess runapt command setsid -w "${BUILDDIRECTORY}/apt-get" purge -y fdleaks -qq
+checkpurge