Adding upstream version 4.9.1.upstream/4.9.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1117 insertions, 0 deletions

diff --git a/attacher.c b/attacher.c
new file mode 100644
index 0000000..c35ae7a
--- /dev/null
+++ b/attacher.c
@@ -0,0 +1,1117 @@
+/* Copyright (c) 2008, 2009
+ *      Juergen Weigert (jnweiger@immd4.informatik.uni-erlangen.de)
+ *      Michael Schroeder (mlschroe@immd4.informatik.uni-erlangen.de)
+ *      Micah Cowan (micah@cowan.name)
+ *      Sadrul Habib Chowdhury (sadrul@users.sourceforge.net)
+ * Copyright (c) 1993-2002, 2003, 2005, 2006, 2007
+ *      Juergen Weigert (jnweiger@immd4.informatik.uni-erlangen.de)
+ *      Michael Schroeder (mlschroe@immd4.informatik.uni-erlangen.de)
+ * Copyright (c) 1987 Oliver Laumann
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program (see the file COPYING); if not, see
+ * https://www.gnu.org/licenses/, or contact Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02111-1301  USA
+ *
+ ****************************************************************
+ */
+
+#include "config.h"
+#include <stdbool.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <signal.h>
+#include "screen.h"
+#include "extern.h"
+
+#include <pwd.h>
+
+static int WriteMessage __P((int, struct msg *));
+static sigret_t AttacherSigInt __P(SIGPROTOARG);
+#if defined(SIGWINCH) && defined(TIOCGWINSZ)
+static sigret_t AttacherWinch __P(SIGPROTOARG);
+#endif
+#ifdef LOCK
+static sigret_t DoLock __P(SIGPROTOARG);
+static void  LockTerminal __P((void));
+static sigret_t LockHup __P(SIGPROTOARG);
+static void  screen_builtin_lck __P((void));
+#endif
+#ifdef DEBUG
+static sigret_t AttacherChld __P(SIGPROTOARG);
+#endif
+static sigret_t AttachSigCont __P(SIGPROTOARG);
+
+extern int real_uid, real_gid, eff_uid, eff_gid;
+extern int ServerSocket;
+extern struct display *displays;
+extern char *SockName, *SockMatch, SockPath[];
+extern char HostName[];
+extern struct passwd *ppp;
+extern char *attach_tty, *attach_term, *LoginName, *preselect;
+/* Indicator whether the current tty exists in another namespace. */
+extern bool attach_tty_is_in_new_ns;
+/* Content of the tty symlink when attach_tty_is_in_new_ns == true. */
+extern char attach_tty_name_in_ns[];
+extern int xflag, dflag, rflag, quietflag, adaptflag;
+extern struct mode attach_Mode;
+extern struct NewWindow nwin_options;
+extern int MasterPid, attach_fd;
+
+#ifdef MULTIUSER
+extern char *multi;
+extern int multiattach, multi_uid, own_uid;
+extern int tty_mode, tty_oldmode;
+# ifndef USE_SETEUID
+static int multipipe[2];
+# endif
+#endif
+
+
+static int ContinuePlease;
+
+static sigret_t
+AttachSigCont SIGDEFARG
+{
+  debug("SigCont()\n");
+  ContinuePlease = 1;
+  SIGRETURN;
+}
+
+static int QueryResult;
+
+static sigret_t
+QueryResultSuccess SIGDEFARG
+{
+  QueryResult = 1;
+  SIGRETURN;
+}
+
+static sigret_t
+QueryResultFail SIGDEFARG
+{
+  QueryResult = 2;
+  SIGRETURN;
+}
+
+/*
+ *  Send message to a screen backend.
+ *  returns 1 if we could attach one, or 0 if none.
+ *  Understands  MSG_ATTACH, MSG_DETACH, MSG_POW_DETACH
+ *               MSG_CONT, MSG_WINCH and nothing else!
+ *
+ *  if type == MSG_ATTACH and sockets are used, attaches
+ *  tty file descriptor.
+ */
+
+static int
+WriteMessage(s, m)
+int s;
+struct msg *m;
+{
+  int r, l = sizeof(*m);
+  bool is_socket;
+
+  is_socket = IsSocket(SockPath);
+  if (is_socket && m->type == MSG_ATTACH)
+    return SendAttachMsg(s, m, attach_fd);
+
+  while(l > 0)
+    {
+      r = write(s, (char *)m + (sizeof(*m) - l), l);
+      if (r == -1 && errno == EINTR)
+	continue;
+      if (r == -1 || r == 0)
+	return -1;
+      l -= r;
+    }
+  return 0;
+}
+
+
+int
+Attach(how)
+int how;
+{
+  int n, lasts;
+  struct msg m;
+  struct stat st;
+  char *s;
+  bool is_socket;
+
+  debug2("Attach: how=%d, tty=%s\n", how, attach_tty);
+#ifdef MULTIUSER
+# ifndef USE_SETEUID
+  while ((how == MSG_ATTACH || how == MSG_CONT) && multiattach)
+    {
+      int ret;
+
+      if (pipe(multipipe))
+	Panic(errno, "pipe");
+      if (chmod(attach_tty, 0666))
+	Panic(errno, "chmod %s", attach_tty);
+      tty_oldmode = tty_mode;
+      eff_uid = -1;	/* make UserContext fork */
+      real_uid = multi_uid;
+      if ((ret = UserContext()) <= 0)
+	{
+	  char dummy;
+          eff_uid = 0;
+	  real_uid = own_uid;
+	  if (ret < 0)
+	    Panic(errno, "UserContext");
+	  close(multipipe[1]);
+	  read(multipipe[0], &dummy, 1);
+	  if (tty_oldmode >= 0)
+	    {
+	      chmod(attach_tty, tty_oldmode);
+	      tty_oldmode = -1;
+	    }
+	  ret = UserStatus();
+#ifdef LOCK
+	  if (ret == SIG_LOCK)
+	    LockTerminal();
+	  else
+#endif
+#ifdef SIGTSTP
+	  if (ret == SIG_STOP)
+	    kill(getpid(), SIGTSTP);
+	  else
+#endif
+	  if (ret == SIG_POWER_BYE)
+	    {
+	      int ppid;
+	      if (setgid(real_gid) || setuid(real_uid))
+		Panic(errno, "setuid/gid");
+	      if ((ppid = getppid()) > 1)
+		Kill(ppid, SIGHUP);
+	      exit(0);
+	    }
+	  else
+            exit(ret);
+	  dflag = 0;
+#ifdef MULTI
+	  xflag = 1;
+#endif
+	  how = MSG_ATTACH;
+	  continue;
+	}
+      close(multipipe[0]);
+      eff_uid  = real_uid;
+      break;
+    }
+# else /* USE_SETEUID */
+  if ((how == MSG_ATTACH || how == MSG_CONT) && multiattach)
+    {
+      real_uid = multi_uid;
+      eff_uid  = own_uid;
+#ifdef HAVE_SETRESUID
+      if (setresuid(multi_uid, own_uid, multi_uid))
+	Panic(errno, "setresuid");
+#else
+      xseteuid(multi_uid);
+      xseteuid(own_uid);
+#endif
+      if (chmod(attach_tty, 0666))
+	Panic(errno, "chmod %s", attach_tty);
+      tty_oldmode = tty_mode;
+    }
+# endif /* USE_SETEUID */
+#endif /* MULTIUSER */
+
+  bzero((char *) &m, sizeof(m));
+  m.type = how;
+  m.protocol_revision = MSG_REVISION;
+  strncpy(m.m_tty, attach_tty_is_in_new_ns ? attach_tty_name_in_ns : attach_tty, sizeof(m.m_tty) - 1);
+  m.m_tty[sizeof(m.m_tty) - 1] = 0;
+
+  is_socket = IsSocket(SockPath);
+  if (how == MSG_WINCH)
+    {
+      if ((lasts = MakeClientSocket(0, is_socket)) >= 0)
+	{
+	  WriteMessage(lasts, &m);
+          close(lasts);
+	}
+      return 0;
+    }
+
+  if (how == MSG_CONT)
+    {
+      if ((lasts = MakeClientSocket(0, is_socket)) < 0)
+        {
+          Panic(0, "Sorry, cannot contact session \"%s\" again.\r\n",
+                 SockName);
+        }
+    }
+  else
+    {
+      n = FindSocket(&lasts, (int *)0, (int *)0, SockMatch, &is_socket);
+      switch (n)
+	{
+	case 0:
+	  if (rflag && (rflag & 1) == 0)
+	    return 0;
+	  if (quietflag)
+	    eexit(10);
+	  if (SockMatch && *SockMatch) {
+	    Panic(0, "There is no screen to be %sed matching %s.",
+		xflag ? "attach" :
+		dflag ? "detach" :
+                        "resum", SockMatch);
+          } else {
+            Panic(0, "There is no screen to be %sed.",
+	        xflag ? "attach" :
+		dflag ? "detach" :
+                        "resum");
+          }
+	  /* NOTREACHED */
+	case 1:
+	  break;
+	default:
+	  if (rflag < 3)
+	    {
+	      if (quietflag)
+		eexit(10 + n);
+	      Panic(0, "Type \"screen [-d] -r [pid.]tty.host\" to resume one of them.");
+	    }
+	  /* NOTREACHED */
+	}
+    }
+  /*
+   * Go in UserContext. Advantage is, you can kill your attacher
+   * when things go wrong. Any disadvantages? jw.
+   * Do this before the attach to prevent races!
+   */
+#ifdef MULTIUSER
+  if (!multiattach)
+#endif
+    {
+      if (setuid(real_uid))
+        Panic(errno, "setuid");
+    }
+#if defined(MULTIUSER) && defined(USE_SETEUID)
+  else
+    {
+      /* This call to xsetuid should also set the saved uid */
+      xseteuid(real_uid); /* multi_uid, allow backend to send signals */
+    }
+#endif
+  eff_uid = real_uid;
+  if (setgid(real_gid))
+    Panic(errno, "setgid");
+  eff_gid = real_gid;
+
+  debug2("Attach: uid %d euid %d\n", (int)getuid(), (int)geteuid());
+  MasterPid = 0;
+  for (s = SockName; *s; s++)
+    {
+      if (*s > '9' || *s < '0')
+	break;
+      MasterPid = 10 * MasterPid + (*s - '0');
+    }
+  debug1("Attach decided, it is '%s'\n", SockPath);
+  debug1("Attach found MasterPid == %d\n", MasterPid);
+  if (stat(SockPath, &st) == -1)
+    Panic(errno, "stat %s", SockPath);
+  if ((st.st_mode & 0600) != 0600)
+    Panic(0, "Socket is in wrong mode (%03o)", (int)st.st_mode);
+
+  /*
+   * Change: if -x or -r ignore failing -d
+   */
+  if ((xflag || rflag) && dflag && (st.st_mode & 0700) == 0600)
+    dflag = 0;
+
+  /*
+   * Without -x, the mode must match. 
+   * With -x the mode is irrelevant unless -d.
+   */
+  if ((dflag || !xflag) && (st.st_mode & 0700) != (dflag ? 0700 : 0600))
+    Panic(0, "That screen is %sdetached.", dflag ? "already " : "not ");
+#ifdef REMOTE_DETACH
+  if (dflag &&
+      (how == MSG_DETACH || how == MSG_POW_DETACH))
+    {
+      m.m.detach.dpid = getpid();
+      strncpy(m.m.detach.duser, LoginName, sizeof(m.m.detach.duser) - 1); 
+      m.m.detach.duser[sizeof(m.m.detach.duser) - 1] = 0;
+# ifdef POW_DETACH
+      if (dflag == 2)
+	m.type = MSG_POW_DETACH;
+      else
+# endif
+	m.type = MSG_DETACH;
+      /* If there is no password for the session, or the user enters the correct
+       * password, then we get a SIGCONT. Otherwise we get a SIG_BYE */
+      signal(SIGCONT, AttachSigCont);
+      if (WriteMessage(lasts, &m))
+	Panic(errno, "WriteMessage");
+      close(lasts);
+      while (!ContinuePlease)
+        pause();	/* wait for SIGCONT */
+      signal(SIGCONT, SIG_DFL);
+      ContinuePlease = 0;
+      if (how != MSG_ATTACH)
+	return 0;	/* we detached it. jw. */
+      sleep(1);	/* we dont want to overrun our poor backend. jw. */
+      if ((lasts = MakeClientSocket(0, is_socket)) == -1)
+	Panic(0, "Cannot contact screen again. Sigh.");
+      m.type = how;
+    }
+#endif
+  ASSERT(how == MSG_ATTACH || how == MSG_CONT);
+  strncpy(m.m.attach.envterm, attach_term, MAXTERMLEN);
+  m.m.attach.envterm[MAXTERMLEN] = 0;
+  debug1("attach: sending %d bytes... ", (int)sizeof(m));
+
+  strncpy(m.m.attach.auser, LoginName, sizeof(m.m.attach.auser) - 1); 
+  m.m.attach.auser[sizeof(m.m.attach.auser) - 1] = 0;
+  m.m.attach.esc = DefaultEsc;
+  m.m.attach.meta_esc = DefaultMetaEsc;
+  strncpy(m.m.attach.preselect, preselect ? preselect : "", sizeof(m.m.attach.preselect) - 1);
+  m.m.attach.preselect[sizeof(m.m.attach.preselect) - 1] = 0;
+  m.m.attach.apid = getpid();
+  m.m.attach.adaptflag = adaptflag;
+  m.m.attach.lines = m.m.attach.columns = 0;
+  if ((s = getenv("LINES")))
+    m.m.attach.lines = atoi(s);
+  if ((s = getenv("COLUMNS")))
+    m.m.attach.columns = atoi(s);
+  m.m.attach.encoding = nwin_options.encoding > 0 ? nwin_options.encoding + 1 : 0;
+
+#ifdef REMOTE_DETACH
+#ifdef POW_DETACH
+  if (dflag == 2)
+    m.m.attach.detachfirst = MSG_POW_DETACH;
+  else
+#endif
+  if (dflag)
+    m.m.attach.detachfirst = MSG_DETACH;
+  else
+#endif
+    m.m.attach.detachfirst = MSG_ATTACH;
+
+#ifdef MULTIUSER
+  /* setup CONT signal handler to repair the terminal mode */
+  if (multi && (how == MSG_ATTACH || how == MSG_CONT))
+    signal(SIGCONT, AttachSigCont);
+#endif
+
+  if (WriteMessage(lasts, &m))
+    Panic(errno, "WriteMessage");
+  close(lasts);
+  debug1("Attach(%d): sent\n", m.type);
+#ifdef MULTIUSER
+  if (multi && (how == MSG_ATTACH || how == MSG_CONT))
+    {
+      while (!ContinuePlease)
+        pause();	/* wait for SIGCONT */
+      signal(SIGCONT, SIG_DFL);
+      ContinuePlease = 0;
+# ifndef USE_SETEUID
+      close(multipipe[1]);
+# else
+      xseteuid(own_uid);
+      if (tty_oldmode >= 0)
+        if (chmod(attach_tty, tty_oldmode))
+          Panic(errno, "chmod %s", attach_tty);
+      tty_oldmode = -1;
+      xseteuid(real_uid);
+# endif
+    }
+#endif
+  rflag = 0;
+  return 1;
+}
+
+
+static int AttacherPanic = 0;
+
+#ifdef DEBUG
+static sigret_t
+AttacherChld SIGDEFARG
+{
+  AttacherPanic = 1;
+  SIGRETURN;
+}
+#endif
+
+static sigret_t 
+AttacherSigAlarm SIGDEFARG
+{
+#ifdef DEBUG
+  static int tick_cnt = 0;
+  if ((tick_cnt = (tick_cnt + 1) % 4) == 0)
+    debug("tick\n");
+#endif
+  SIGRETURN;
+}
+
+/*
+ * the frontend's Interrupt handler
+ * we forward SIGINT to the poor backend
+ */
+static sigret_t 
+AttacherSigInt SIGDEFARG
+{
+  signal(SIGINT, AttacherSigInt);
+  Kill(MasterPid, SIGINT);
+  SIGRETURN;
+}
+
+/*
+ * Unfortunately this is also the SIGHUP handler, so we have to
+ * check if the backend is already detached.
+ */
+
+sigret_t
+AttacherFinit SIGDEFARG
+{
+  struct stat statb;
+  struct msg m;
+  int s;
+  bool is_socket;
+
+  debug("AttacherFinit();\n");
+  signal(SIGHUP, SIG_IGN);
+  /* Check if signal comes from backend */
+  if (stat(SockPath, &statb) == 0 && (statb.st_mode & 0777) != 0600)
+    {
+      debug("Detaching backend!\n");
+      bzero((char *) &m, sizeof(m));
+      strncpy(m.m_tty, attach_tty_is_in_new_ns ? attach_tty_name_in_ns : attach_tty, sizeof(m.m_tty) - 1);
+      m.m_tty[sizeof(m.m_tty) - 1] = 0;
+      debug1("attach_tty is %s\n", attach_tty);
+      m.m.detach.dpid = getpid();
+      m.type = MSG_HANGUP;
+      m.protocol_revision = MSG_REVISION;
+      is_socket = IsSocket(SockPath);
+      if ((s = MakeClientSocket(0, is_socket)) >= 0)
+	{
+          WriteMessage(s, &m);
+	  close(s);
+	}
+    }
+#ifdef MULTIUSER
+  if (tty_oldmode >= 0)
+    {
+      if (setuid(own_uid))
+        Panic(errno, "setuid");
+      chmod(attach_tty, tty_oldmode);
+    }
+#endif
+  exit(0);
+  SIGRETURN;
+}
+
+#ifdef POW_DETACH
+static sigret_t
+AttacherFinitBye SIGDEFARG
+{
+  int ppid;
+  debug("AttacherFintBye()\n");
+#if defined(MULTIUSER) && !defined(USE_SETEUID)
+  if (multiattach)
+    exit(SIG_POWER_BYE);
+#endif
+  if (setgid(real_gid))
+    Panic(errno, "setgid");
+#ifdef MULTIUSER
+  if (setuid(own_uid))
+    Panic(errno, "setuid");
+#else
+  if (setuid(real_uid))
+    Panic(errno, "setuid");
+#endif
+  /* we don't want to disturb init (even if we were root), eh? jw */
+  if ((ppid = getppid()) > 1)
+    Kill(ppid, SIGHUP);		/* carefully say good bye. jw. */
+  exit(0);
+  SIGRETURN;
+}
+#endif
+
+#if defined(DEBUG) && defined(SIG_NODEBUG)
+static sigret_t
+AttacherNoDebug SIGDEFARG
+{
+  debug("AttacherNoDebug()\n");
+  signal(SIG_NODEBUG, AttacherNoDebug);
+  if (dfp)
+    { 
+      debug("debug: closing debug file.\n");
+      fflush(dfp);
+      fclose(dfp);
+      dfp = NULL;
+    }
+  SIGRETURN;
+}
+#endif /* SIG_NODEBUG */
+
+static int SuspendPlease;
+
+static sigret_t
+SigStop SIGDEFARG
+{
+  debug("SigStop()\n");
+  SuspendPlease = 1;
+  SIGRETURN;
+}
+
+#ifdef LOCK
+static int LockPlease;
+
+static sigret_t
+DoLock SIGDEFARG
+{
+# ifdef SYSVSIGS
+  signal(SIG_LOCK, DoLock);
+# endif
+  debug("DoLock()\n");
+  LockPlease = 1;
+  SIGRETURN;
+}
+#endif
+
+#if defined(SIGWINCH) && defined(TIOCGWINSZ)
+static int SigWinchPlease;
+
+static sigret_t
+AttacherWinch SIGDEFARG
+{
+  debug("AttacherWinch()\n");
+  SigWinchPlease = 1;
+  SIGRETURN;
+}
+#endif
+
+
+/*
+ *  Attacher loop - no return
+ */
+
+void
+Attacher()
+{
+  signal(SIGHUP, AttacherFinit);
+  signal(SIG_BYE, AttacherFinit);
+#ifdef POW_DETACH
+  signal(SIG_POWER_BYE, AttacherFinitBye);
+#endif
+#if defined(DEBUG) && defined(SIG_NODEBUG)
+  signal(SIG_NODEBUG, AttacherNoDebug);
+#endif
+#ifdef LOCK
+  signal(SIG_LOCK, DoLock);
+#endif
+  signal(SIGINT, AttacherSigInt);
+#ifdef BSDJOBS
+  signal(SIG_STOP, SigStop);
+#endif
+#if defined(SIGWINCH) && defined(TIOCGWINSZ)
+  signal(SIGWINCH, AttacherWinch);
+#endif
+#ifdef DEBUG
+  signal(SIGCHLD, AttacherChld);
+#endif
+  debug("attacher: going for a nap.\n");
+  dflag = 0;
+#ifdef MULTI
+  xflag = 1;
+#endif
+  for (;;)
+    {
+      signal(SIGALRM, AttacherSigAlarm);
+      alarm(15);
+      pause();
+      alarm(0);
+      if (kill(MasterPid, 0) < 0 && errno != EPERM)
+        {
+	  debug1("attacher: Panic! MasterPid %d does not exist.\n", MasterPid);
+	  AttacherPanic++;
+	}
+      if (AttacherPanic)
+        {
+	  fcntl(0, F_SETFL, 0);
+	  SetTTY(0, &attach_Mode);
+	  printf("\nError: Cannot find master process to attach to!\n");
+	  eexit(1);
+        }
+#ifdef BSDJOBS
+      if (SuspendPlease)
+	{
+	  SuspendPlease = 0;
+#if defined(MULTIUSER) && !defined(USE_SETEUID)
+	  if (multiattach)
+	    exit(SIG_STOP);
+#endif
+	  signal(SIGTSTP, SIG_DFL);
+	  debug("attacher: killing myself SIGTSTP\n");
+	  kill(getpid(), SIGTSTP);
+	  debug("attacher: continuing from stop\n");
+	  signal(SIG_STOP, SigStop);
+	  (void) Attach(MSG_CONT);
+	}
+#endif
+#ifdef LOCK
+      if (LockPlease)
+	{
+	  LockPlease = 0;
+#if defined(MULTIUSER) && !defined(USE_SETEUID)
+	  if (multiattach)
+	    exit(SIG_LOCK);
+#endif
+	  LockTerminal();
+# ifdef SYSVSIGS
+	  signal(SIG_LOCK, DoLock);
+# endif
+	  (void) Attach(MSG_CONT);
+	}
+#endif	/* LOCK */
+#if defined(SIGWINCH) && defined(TIOCGWINSZ)
+      if (SigWinchPlease)
+	{
+	  SigWinchPlease = 0;
+# ifdef SYSVSIGS
+	  signal(SIGWINCH, AttacherWinch);
+# endif
+	  (void) Attach(MSG_WINCH);
+	}
+#endif	/* SIGWINCH */
+    }
+}
+
+#ifdef LOCK
+
+/* ADDED by Rainer Pruy 10/15/87 */
+/* POLISHED by mls. 03/10/91 */
+
+static char LockEnd[] = "Welcome back to screen !!\n";
+
+static sigret_t
+LockHup SIGDEFARG
+{
+  int ppid = getppid();
+  if (setgid(real_gid))
+    Panic(errno, "setgid");
+#ifdef MULTIUSER
+  if (setuid(own_uid))
+    Panic(errno, "setuid");
+#else
+  if (setuid(real_uid))
+    Panic(errno, "setuid");
+#endif
+  if (ppid > 1)
+    Kill(ppid, SIGHUP);
+  exit(0);
+}
+
+static void
+LockTerminal()
+{
+  char *prg;
+  int sig, pid;
+  sigret_t (*sigs[NSIG])__P(SIGPROTOARG);
+
+  for (sig = 1; sig < NSIG; sig++)
+    sigs[sig] = signal(sig, sig == SIGCHLD ? SIG_DFL : SIG_IGN);
+  signal(SIGHUP, LockHup);
+  printf("\n");
+
+  prg = getenv("LOCKPRG");
+  if (prg && strcmp(prg, "builtin") && !access(prg, X_OK))
+    {
+      signal(SIGCHLD, SIG_DFL);
+      debug1("lockterminal: '%s' seems executable, execl it!\n", prg);
+      if ((pid = fork()) == 0)
+        {
+          /* Child */
+          displays = 0;		/* beware of Panic() */
+          ServerSocket = -1;
+          if (setgid(real_gid))
+            Panic(errno, "setgid");
+#ifdef MULTIUSER
+          if (setuid(own_uid))
+            Panic(errno, "setuid");
+#else
+          if (setuid(real_uid))   /* this should be done already */
+            Panic(errno, "setuid");
+#endif
+          closeallfiles(0);	/* important: /etc/shadow may be open */
+          execl(prg, "SCREEN-LOCK", NULL);
+          exit(errno);
+        }
+      if (pid == -1)
+        Msg(errno, "Cannot lock terminal - fork failed");
+      else
+        {
+#ifdef BSDWAIT
+          union wait wstat;
+#else
+          int wstat;
+#endif
+          int wret;
+
+#ifdef hpux
+          signal(SIGCHLD, SIG_DFL);
+#endif
+          errno = 0;
+          while (((wret = wait(&wstat)) != pid) ||
+	         ((wret == -1) && (errno == EINTR))
+	         )
+	    errno = 0;
+    
+          if (errno)
+	    {
+	      Msg(errno, "Lock");
+	      sleep(2);
+	    }
+	  else if (WTERMSIG(wstat) != 0)
+	    {
+	      fprintf(stderr, "Lock: %s: Killed by signal: %d%s\n", prg,
+		      WTERMSIG(wstat), WIFCORESIG(wstat) ? " (Core dumped)" : "");
+	      sleep(2);
+	    }
+	  else if (WEXITSTATUS(wstat))
+	    {
+	      debug2("Lock: %s: return code %d\n", prg, WEXITSTATUS(wstat));
+	    }
+          else
+	    printf("%s", LockEnd);
+        }
+    }
+  else
+    {
+      if (prg)
+	{
+          debug1("lockterminal: '%s' seems NOT executable, we use our builtin\n", prg);
+	}
+      else
+	{
+	  debug("lockterminal: using buitin.\n");
+	}
+      screen_builtin_lck();
+    }
+  /* reset signals */
+  for (sig = 1; sig < NSIG; sig++)
+    {
+      if (sigs[sig] != (sigret_t(*)__P(SIGPROTOARG)) -1)
+	signal(sig, sigs[sig]);
+    }
+}				/* LockTerminal */
+
+#ifdef USE_PAM
+
+/*
+ *  PAM support by Pablo Averbuj <pablo@averbuj.com>
+ */
+
+#include <security/pam_appl.h>
+
+static int PAM_conv __P((int, const struct pam_message **, struct pam_response **, void *));
+
+static int
+PAM_conv(num_msg, msg, resp, appdata_ptr)
+int num_msg;
+const struct pam_message **msg;
+struct pam_response **resp;
+void *appdata_ptr;
+{
+  int replies = 0;
+  struct pam_response *reply = NULL;
+
+  reply = malloc(sizeof(struct pam_response)*num_msg);
+  if (!reply)
+    return PAM_CONV_ERR;
+  #define COPY_STRING(s) (s) ? strdup(s) : NULL
+
+  for (replies = 0; replies < num_msg; replies++)
+    {
+      switch (msg[replies]->msg_style)
+        {
+	case PAM_PROMPT_ECHO_OFF:
+	  /* wants password */
+	  reply[replies].resp_retcode = PAM_SUCCESS;
+	  reply[replies].resp = appdata_ptr ? strdup((char *)appdata_ptr) : 0;
+	  break;
+	case PAM_TEXT_INFO:
+	  /* ignore the informational mesage */
+	  /* but first clear out any drek left by malloc */
+	  reply[replies].resp = NULL;
+	  break;
+	case PAM_PROMPT_ECHO_ON:
+	  /* user name given to PAM already */
+	  /* fall through */
+	default:
+	  /* unknown or PAM_ERROR_MSG */
+	  free(reply);
+	  return PAM_CONV_ERR;
+	}
+    }
+  *resp = reply;
+  return PAM_SUCCESS;
+}
+
+static struct pam_conv PAM_conversation = {
+    &PAM_conv,
+    NULL
+};
+
+
+#endif
+
+/* -- original copyright by Luigi Cannelloni 1985 (luigi@faui70.UUCP) -- */
+static void
+screen_builtin_lck()
+{
+  char fullname[100], *cp1, message[100 + 100];
+#ifdef USE_PAM
+  pam_handle_t *pamh = 0;
+  int pam_error;
+  char *tty_name;
+#endif
+  char *pass = 0, mypass[16 + 1], salt[3];
+  int using_pam = 1;
+
+#ifdef USE_PAM
+  if (!ppp->pw_uid)
+    {
+#endif
+  using_pam = 0;
+  pass = ppp->pw_passwd;
+  if (pass == 0 || *pass == 0)
+    {
+      if ((pass = getpass("Key:   ")))
+        {
+          strncpy(mypass, pass, sizeof(mypass) - 1);
+          mypass[sizeof(mypass) - 1] = 0;
+          if (*mypass == 0)
+            return;
+          if ((pass = getpass("Again: ")))
+            {
+              if (strcmp(mypass, pass))
+                {
+                  fprintf(stderr, "Passwords don't match.\007\n");
+                  sleep(2);
+                  return;
+                }
+            }
+        }
+      if (pass == 0)
+        {
+          fprintf(stderr, "Getpass error.\007\n");
+          sleep(2);
+          return;
+        }
+
+      salt[0] = 'A' + (int)(time(0) % 26);
+      salt[1] = 'A' + (int)((time(0) >> 6) % 26);
+      salt[2] = 0;
+      pass = crypt(mypass, salt);
+      if (!pass)
+	{
+          fprintf(stderr, "crypt() error.\007\n");
+          sleep(2);
+          return;
+	}
+      pass = ppp->pw_passwd = SaveStr(pass);
+    }
+#ifdef USE_PAM
+    }
+#endif
+
+  debug("screen_builtin_lck looking in gcos field\n");
+  strncpy(fullname, ppp->pw_gecos, sizeof(fullname) - 9);
+  fullname[sizeof(fullname) - 9] = 0;
+
+  if ((cp1 = index(fullname, ',')) != NULL)
+    *cp1 = '\0';
+  if ((cp1 = index(fullname, '&')) != NULL)
+    {
+      strncpy(cp1, ppp->pw_name, 8);
+      cp1[8] = 0;
+      if (*cp1 >= 'a' && *cp1 <= 'z')
+	*cp1 -= 'a' - 'A';
+    }
+
+  sprintf(message, "Screen used by %s%s<%s> on %s.\nPassword:\007",
+          fullname, fullname[0] ? " " : "", ppp->pw_name, HostName);
+
+  /* loop here to wait for correct password */
+  for (;;)
+    {
+      debug("screen_builtin_lck awaiting password\n");
+      errno = 0;
+      if ((cp1 = getpass(message)) == NULL)
+        {
+          AttacherFinit(SIGARG);
+          /* NOTREACHED */
+        }
+      if (using_pam)
+        {
+#ifdef USE_PAM
+      PAM_conversation.appdata_ptr = cp1;
+      pam_error = pam_start("screen", ppp->pw_name, &PAM_conversation, &pamh);
+      if (pam_error != PAM_SUCCESS)
+	AttacherFinit(SIGARG);		/* goodbye */
+
+      if (strncmp(attach_tty, "/dev/", 5) == 0)
+	tty_name = attach_tty + 5;
+      else
+	tty_name = attach_tty;
+      pam_error = pam_set_item(pamh, PAM_TTY, tty_name);
+      if (pam_error != PAM_SUCCESS)
+	AttacherFinit(SIGARG);		/* goodbye */
+
+      pam_error = pam_authenticate(pamh, 0);
+      pam_end(pamh, pam_error);
+      PAM_conversation.appdata_ptr = 0;
+      if (pam_error == PAM_SUCCESS)
+	break;
+#endif
+        }
+      else
+	{
+          char *buf = crypt(cp1, pass);
+          if (buf && !strncmp(buf, pass, strlen(pass)))
+	    break;
+	}
+      debug("screen_builtin_lck: NO!!!!!\n");
+      bzero(cp1, strlen(cp1));
+    }
+  bzero(cp1, strlen(cp1));
+  debug("password ok.\n");
+}
+
+#endif	/* LOCK */
+
+
+void
+SendCmdMessage(sty, match, av, query)
+char *sty;
+char *match;
+char **av;
+int query;
+{
+  int i, s;
+  struct msg m;
+  char *p;
+  int len, n;
+  bool is_socket;
+
+  if (sty == 0)
+    {
+      i = FindSocket(&s, (int *)0, (int *)0, match, &is_socket);
+      if (i == 0)
+	Panic(0, "No screen session found.");
+      if (i != 1)
+	Panic(0, "Use -S to specify a session.");
+    }
+  else
+    {
+#ifdef NAME_MAX
+      if (strlen(sty) > NAME_MAX)
+	sty[NAME_MAX] = 0;
+#endif
+      if (strlen(sty) > 2 * MAXSTR - 1)
+	sty[2 * MAXSTR - 1] = 0;
+      sprintf(SockPath + strlen(SockPath), "/%s", sty);
+      is_socket = IsSocket(SockPath);
+      if ((s = MakeClientSocket(1, is_socket)) == -1)
+	exit(1);
+    }
+  bzero((char *)&m, sizeof(m));
+  m.type = query ? MSG_QUERY : MSG_COMMAND;
+  if (attach_tty)
+    {
+      strncpy(m.m_tty, attach_tty_is_in_new_ns ? attach_tty_name_in_ns : attach_tty, sizeof(m.m_tty) - 1);
+      m.m_tty[sizeof(m.m_tty) - 1] = 0;
+    }
+  p = m.m.command.cmd;
+  n = 0;
+  for (; *av && n < MAXARGS - 1; ++av, ++n)
+    {
+      len = strlen(*av) + 1;
+      if (p + len >= m.m.command.cmd + sizeof(m.m.command.cmd) - 1)
+	break;
+      strcpy(p, *av);
+      p += len;
+    }
+  *p = 0;
+  m.m.command.nargs = n;
+  strncpy(m.m.attach.auser, LoginName, sizeof(m.m.attach.auser) - 1);
+  m.m.command.auser[sizeof(m.m.command.auser) - 1] = 0;
+  m.protocol_revision = MSG_REVISION;
+  strncpy(m.m.command.preselect, preselect ? preselect : "", sizeof(m.m.command.preselect) - 1);
+  m.m.command.preselect[sizeof(m.m.command.preselect) - 1] = 0;
+  m.m.command.apid = getpid();
+  debug1("SendCommandMsg writing '%s'\n", m.m.command.cmd);
+  if (query)
+    {
+      /* Create a server socket so we can get back the result */
+      char *sp = SockPath + strlen(SockPath);
+      char query[] = "-queryX";
+      char c;
+      int r = -1;
+      for (c = 'A'; c <= 'Z'; c++)
+	{
+	  query[6] = c;
+	  strcpy(sp, query);	/* XXX: strncpy? */
+	  if ((r = MakeServerSocket(is_socket)) >= 0)
+	    break;
+	}
+      if (r < 0)
+	{
+	  for (c = '0'; c <= '9'; c++)
+	    {
+	      query[6] = c;
+	      strcpy(sp, query);
+	      if ((r = MakeServerSocket(is_socket)) >= 0)
+		break;
+	    }
+	}
+
+      if (r < 0)
+	Panic(0, "Could not create a listening socket to read the results.");
+
+      strncpy(m.m.command.writeback, SockPath, sizeof(m.m.command.writeback) - 1);
+      m.m.command.writeback[sizeof(m.m.command.writeback) - 1] = '\0';
+
+      /* Send the message, then wait for a response */
+      signal(SIGCONT, QueryResultSuccess);
+      signal(SIG_BYE, QueryResultFail);
+      if (WriteMessage(s, &m))
+	Msg(errno, "write");
+      close(s);
+      while (!QueryResult)
+	pause();
+      signal(SIGCONT, SIG_DFL);
+      signal(SIG_BYE, SIG_DFL);
+
+      /* Read the result and spit it out to stdout */
+      ReceiveRaw(r);
+      unlink(SockPath);
+      if (QueryResult == 2)	/* An error happened */
+	exit(1);
+    }
+  else
+    {
+      if (WriteMessage(s, &m))
+	Msg(errno, "write");
+      close(s);
+    }
+}
+