fix PTY interaction on linux and kfreebsd

We run dpkg on its own pty, so we can log its output and have our own
output around it (like the progress bar), while also allowing debconf
and configfile prompts to happen.

In commit 223ae57d468fdcac451209a095047a07a5698212 we changed to
constantly reopening the slave for kfreebsd. This has the sideeffect
though that in some cases slave and master will lose their connection on
linux, so that no output is passed along anymore. We fix this by having
always an fd referencing the slave open (linux), but we don't use it
(kfreebsd).

Failing to get our PTY up and running has many (bad) consequences
including (not limited to, nor all at ones or in any case) garbled ouput,
no output, no logging, a (partial) mixture of the previous items, …
This commit is therefore also reshuffling quiet a bit of the creation
code to get especially the output part up and running on linux and the
logging for kfreebsd.

Note that the testcase tries to cover some cases, but this is an
interactivity issue so only interactive usage can really be a good test.

Closes: 765687

apt-pkg/deb/dpkgpm.cc

@@ -72,7 +72,8 @@ class pkgDPkgPMPrivate
 public:
    pkgDPkgPMPrivate() : stdin_is_dev_null(false), dpkgbuf_pos(0),
 			term_out(NULL), history_out(NULL),
-                        progress(NULL), master(-1), slave(NULL)
+			progress(NULL), tt_is_valid(false), master(-1),
+			slave(NULL), protect_slave_from_dying(-1)
    {
       dpkgbuf[0] = '\0';
    }
@@ -90,8 +91,10 @@ public:
 
    // pty stuff
    struct termios tt;
+   bool tt_is_valid;
    int master;
    char * slave;
+   int protect_slave_from_dying;
 
    // signals
    sigset_t sigmask;
@@ -1069,47 +1072,40 @@ void pkgDPkgPM::StartPtyMagic()
    }
 
    _error->PushToStack();
-   // if tcgetattr for both stdin/stdout returns 0 (no error)
-   // we do the pty magic
-   if (tcgetattr(STDOUT_FILENO, &d->tt) == 0 &&
-	 tcgetattr(STDIN_FILENO, &d->tt) == 0)
+
+   d->master = posix_openpt(O_RDWR | O_NOCTTY);
+   if (d->master == -1)
+      _error->Errno("posix_openpt", _("Can not write log (%s)"), _("Is /dev/pts mounted?"));
+   else if (unlockpt(d->master) == -1)
+      _error->Errno("unlockpt", "Unlocking the slave of master fd %d failed!", d->master);
+   else
    {
-      d->master = posix_openpt(O_RDWR | O_NOCTTY);
-      if (d->master == -1)
-	 _error->Errno("posix_openpt", _("Can not write log (%s)"), _("Is /dev/pts mounted?"));
-      else if (unlockpt(d->master) == -1)
-      {
-	 _error->Errno("unlockpt", "Unlocking the slave of master fd %d failed!", d->master);
-	 close(d->master);
-	 d->master = -1;
-      }
+      char const * const slave_name = ptsname(d->master);
+      if (slave_name == NULL)
+	 _error->Errno("ptsname", "Getting name for slave of master fd %d failed!", d->master);
       else
       {
-	 char const * const slave_name = ptsname(d->master);
-	 if (slave_name == NULL)
+	 d->slave = strdup(slave_name);
+	 if (d->slave == NULL)
+	    _error->Errno("strdup", "Copying name %s for slave of master fd %d failed!", slave_name, d->master);
+	 else if (grantpt(d->master) == -1)
+	    _error->Errno("grantpt", "Granting access to slave %s based on master fd %d failed!", slave_name, d->master);
+	 else if (tcgetattr(STDIN_FILENO, &d->tt) == 0)
 	 {
-	    _error->Errno("unlockpt", "Getting name for slave of master fd %d failed!", d->master);
-	    close(d->master);
-	    d->master = -1;
-	 }
-	 else
-	 {
-	    d->slave = strdup(slave_name);
-	    if (d->slave == NULL)
+	    d->tt_is_valid = true;
+	    struct termios raw_tt;
+	    // copy window size of stdout if its a 'good' terminal
+	    if (tcgetattr(STDOUT_FILENO, &raw_tt) == 0)
 	    {
-	       _error->Errno("strdup", "Copying name %s for slave of master fd %d failed!", slave_name, d->master);
-	       close(d->master);
-	       d->master = -1;
+	       struct winsize win;
+	       if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &win) < 0)
+		  _error->Errno("ioctl", "Getting TIOCGWINSZ from stdout failed!");
+	       if (ioctl(d->master, TIOCSWINSZ, &win) < 0)
+		  _error->Errno("ioctl", "Setting TIOCSWINSZ for master fd %d failed!", d->master);
 	    }
-	    struct winsize win;
-	    if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &win) < 0)
-	       _error->Errno("ioctl", "Getting TIOCGWINSZ from stdout failed!");
-	    if (ioctl(d->master, TIOCSWINSZ, &win) < 0)
-	       _error->Errno("ioctl", "Setting TIOCSWINSZ for master fd %d failed!", d->master);
 	    if (tcsetattr(d->master, TCSANOW, &d->tt) == -1)
 	       _error->Errno("tcsetattr", "Setting in Start via TCSANOW for master fd %d failed!", d->master);
 
-	    struct termios raw_tt;
 	    raw_tt = d->tt;
 	    cfmakeraw(&raw_tt);
 	    raw_tt.c_lflag &= ~ECHO;
@@ -1121,18 +1117,22 @@ void pkgDPkgPM::StartPtyMagic()
 	    sigaddset(&d->sigmask, SIGTTOU);
 	    sigprocmask(SIG_BLOCK,&d->sigmask, &d->original_sigmask);
 	    if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw_tt) == -1)
-	       _error->Errno("tcsetattr", "Setting in Start via TCSAFLUSH for stdout failed!");
+	       _error->Errno("tcsetattr", "Setting in Start via TCSAFLUSH for stdin failed!");
 	    sigprocmask(SIG_SETMASK, &d->original_sigmask, NULL);
+
+	 }
+	 if (d->slave != NULL)
+	 {
+	    /* on linux, closing (and later reopening) all references to the slave
+	       makes the slave a death end, so we open it here to have one open all
+	       the time. We could use this fd in SetupSlavePtyMagic() for linux, but
+	       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);
 	 }
       }
    }
-   else
-   {
-      // complain only if stdout is either a terminal (but still failed) or is an invalid
-      // descriptor otherwise we would complain about redirection to e.g. /dev/null as well.
-      if (isatty(STDOUT_FILENO) == 1 || errno == EBADF)
-	 _error->Errno("tcgetattr", _("Can not write log (%s)"), _("Is stdout a terminal?"));
-   }
 
    if (_error->PendingError() == true)
    {
@@ -1141,17 +1141,23 @@ void pkgDPkgPM::StartPtyMagic()
 	 close(d->master);
 	 d->master = -1;
       }
+      if (d->slave != NULL)
+      {
+	 free(d->slave);
+	 d->slave = NULL;
+      }
       _error->DumpErrors(std::cerr);
    }
    _error->RevertToStack();
 }
 void pkgDPkgPM::SetupSlavePtyMagic()
 {
-   if(d->master == -1)
+   if(d->master == -1 || d->slave == NULL)
       return;
 
    if (close(d->master) == -1)
       _error->FatalE("close", "Closing master %d in child failed!", d->master);
+   d->master = -1;
    if (setsid() == -1)
       _error->FatalE("setsid", "Starting a new session for child failed!");
 
@@ -1166,7 +1172,7 @@ void pkgDPkgPM::SetupSlavePtyMagic()
 	 if (dup2(slaveFd, i) == -1)
 	    _error->FatalE("dup2", "Dupping %d to %d in child failed!", slaveFd, i);
 
-      if (tcsetattr(0, TCSANOW, &d->tt) < 0)
+      if (d->tt_is_valid == true && tcsetattr(STDIN_FILENO, TCSANOW, &d->tt) < 0)
 	 _error->FatalE("tcsetattr", "Setting in Setup via TCSANOW for slave fd %d failed!", slaveFd);
    }
 
@@ -1178,9 +1184,14 @@ void pkgDPkgPM::StopPtyMagic()
    if (d->slave != NULL)
       free(d->slave);
    d->slave = NULL;
+   if (d->protect_slave_from_dying != -1)
+   {
+      close(d->protect_slave_from_dying);
+      d->protect_slave_from_dying = -1;
+   }
    if(d->master >= 0) 
    {
-      if (tcsetattr(0, TCSAFLUSH, &d->tt) == -1)
+      if (d->tt_is_valid == true && tcsetattr(STDIN_FILENO, TCSAFLUSH, &d->tt) == -1)
 	 _error->FatalE("tcsetattr", "Setting in Stop via TCSAFLUSH for stdin failed!");
       close(d->master);
       d->master = -1;

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

@@ -8,7 +8,7 @@ setupenvironment
 configarchitecture 'native'
 configdpkgnoopchroot
 
-setupsimplenativepackage "fdleaks" 'native' '1.0' 'unstable'
+setupsimplenativepackage "fdleaks" 'all' '1.0' 'unstable'
 BUILDDIR="incoming/fdleaks-1.0"
 for script in 'preinst' 'postinst' 'prerm' 'postrm'; do
 	echo '#!/bin/sh
@@ -19,7 +19,8 @@ rm -rf "$BUILDDIR"
 
 setupaptarchive
 
-testsuccess aptget install -y fdleaks
+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
@@ -29,7 +30,23 @@ else
 	msgfail
 fi
 
-testsuccess aptget purge -y fdleaks
+cp rootdir/tmp/testsuccess.output terminal.output
+tail -n +3 rootdir/var/log/apt/term.log | head -n -1 > terminal.log
+testfileequal 'terminal.log' "$(cat terminal.output)"
+
+testequal 'startup archives unpack
+install fdleaks:all <none> 1.0
+status half-installed fdleaks:all 1.0
+status unpacked fdleaks:all 1.0
+status unpacked fdleaks:all 1.0
+startup packages configure
+configure fdleaks:all 1.0 <none>
+status unpacked fdleaks:all 1.0
+status half-configured fdleaks:all 1.0
+status installed fdleaks:all 1.0' cut -f 3- -d' ' rootdir/var/log/dpkg.log
+
+rm -f rootdir/var/log/dpkg.log rootdir/var/log/apt/term.log
+testsuccess aptget purge -y fdleaks -qq
 msgtest 'Check if fds were not' 'leaked'
 if [ "$(grep 'root root' rootdir/tmp/testsuccess.output | wc -l)" = '12' ]; then
 	msgpass
@@ -38,3 +55,20 @@ else
 	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)"
+
+testequal 'startup packages purge
+status installed fdleaks:all 1.0
+remove fdleaks:all 1.0 <none>
+status half-configured fdleaks:all 1.0
+status half-installed fdleaks:all 1.0
+status config-files fdleaks:all 1.0
+purge fdleaks:all 1.0 <none>
+status config-files fdleaks:all 1.0
+status config-files fdleaks:all 1.0
+status config-files fdleaks:all 1.0
+status config-files fdleaks:all 1.0
+status config-files fdleaks:all 1.0
+status not-installed fdleaks:all <none>' cut -f 3- -d' ' rootdir/var/log/dpkg.log