Adding upstream version 4.6.2.upstream/4.6.2upstream

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

1 files changed, 1930 insertions, 0 deletions

diff --git a/socket.c b/socket.c
new file mode 100644
index 0000000..88c3dd8
--- /dev/null
+++ b/socket.c
@@ -0,0 +1,1930 @@
+/* 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
+ * http://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 <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+# include <sys/socket.h>
+# ifdef _OpenBSD_
+#  include <sys/uio.h>
+# endif
+# include <sys/un.h>
+
+#ifndef SIGINT
+# include <signal.h>
+#endif
+
+#include "screen.h"
+
+#ifdef HAVE_DIRENT_H
+# include <dirent.h>
+#else
+# include <sys/dir.h>
+# define dirent direct
+#endif
+
+#ifndef CMSG_LEN
+#define CMSG_LEN(length) ((_CMSG_DATA_ALIGN(sizeof(struct cmsghdr))) + (length))
+#endif
+#ifndef CMSG_SPACE
+#define CMSG_SPACE(length) ((_CMSG_DATA_ALIGN(sizeof(struct cmsghdr))) + (_CMSG_DATA_ALIGN(length)))
+#endif
+
+#include "extern.h"
+#include "list_generic.h"
+
+static int   CheckPid __P((int));
+static void  ExecCreate __P((struct msg *));
+static void  DoCommandMsg __P((struct msg *));
+#if defined(_SEQUENT_)
+# define connect sconnect	/* _SEQUENT_ has braindamaged connect */
+static int   sconnect __P((int, struct sockaddr *, int));
+#endif
+static void  FinishAttach __P((struct msg *));
+static void  FinishDetach __P((struct msg *));
+static void  AskPassword __P((struct msg *));
+
+
+extern char *RcFileName, *extra_incap, *extra_outcap;
+extern int ServerSocket, real_uid, real_gid, eff_uid, eff_gid;
+extern int dflag, iflag, rflag, lsflag, quietflag, wipeflag, xflag;
+extern int queryflag;
+extern char *attach_tty, *LoginName, HostName[];
+extern struct display *display, *displays;
+extern struct win *fore, **wtab, *console_window, *windows;
+extern struct layer *flayer;
+extern struct layout *layout_attach, *layout_last, layout_last_marker;
+extern struct NewWindow nwin_undef;
+#ifdef MULTIUSER
+extern char *multi;
+#endif
+extern int maxwin;
+
+extern char *getenv();
+
+extern char SockPath[];
+extern struct event serv_read;
+extern char *rc_name;
+extern struct comm comms[];
+
+#ifdef MULTIUSER
+# define SOCKMODE (S_IWRITE | S_IREAD | (displays ? S_IEXEC : 0) | (multi ? 1 : 0))
+#else
+# define SOCKMODE (S_IWRITE | S_IREAD | (displays ? S_IEXEC : 0))
+#endif
+
+
+/*
+ *  Socket directory manager
+ *
+ *  fdp: pointer to store the first good socket.
+ *  nfoundp: pointer to store the number of sockets found matching.
+ *  notherp: pointer to store the number of sockets not matching.
+ *  match: string to match socket name.
+ *
+ *  The socket directory must be in SockPath!
+ *  The global variables LoginName, multi, rflag, xflag, dflag,
+ *  quietflag, SockPath are used.
+ *
+ *  The first good socket is stored in fdp and its name is
+ *  appended to SockPath.
+ *  If none exists or fdp is NULL SockPath is not changed.
+ *
+ *  Returns: number of good sockets.
+ *
+ */
+
+int
+FindSocket(fdp, nfoundp, notherp, match, is_sock)
+int *fdp;
+int *nfoundp, *notherp;
+char *match;
+bool *is_sock;
+{
+  DIR *dirp;
+  struct dirent *dp;
+  struct stat st;
+  int mode;
+  int sdirlen;
+  int  matchlen = 0;
+  char *name, *n;
+  int firsts = -1, sockfd;
+  char *firstn = NULL;
+  int nfound = 0, ngood = 0, ndead = 0, nwipe = 0, npriv = 0;
+  int nperfect = 0;
+  struct sent
+    {
+      struct sent *next;
+      int mode;
+      char *name;
+    } *slist, **slisttail, *sent, *nsent;
+
+  if (match)
+    {
+      matchlen = strlen(match);
+#ifdef NAME_MAX
+      if (matchlen > NAME_MAX)
+	matchlen = NAME_MAX;
+#endif
+    }
+
+  /*
+   * SockPath contains the socket directory.
+   * At the end of FindSocket the socket name will be appended to it.
+   * Thus FindSocket() can only be called once!
+   */
+  sdirlen = strlen(SockPath);
+
+#ifdef USE_SETEUID
+  xseteuid(real_uid);
+  xsetegid(real_gid);
+#endif
+
+  if ((dirp = opendir(SockPath)) == 0)
+    Panic(errno, "Cannot opendir %s", SockPath);
+
+  slist = 0;
+  slisttail = &slist;
+  while ((dp = readdir(dirp)))
+    {
+      int cmatch = 0;
+      name = dp->d_name;
+      debug1("- %s\n",  name);
+      if (*name == 0 || *name == '.' || strlen(name) > 2*MAXSTR)
+	continue;
+      if (matchlen)
+	{
+	  n = name;
+	  /* if we don't want to match digits. Skip them */
+	  if ((*match <= '0' || *match > '9') && (*n > '0' && *n <= '9'))
+	    {
+	      while (*n >= '0' && *n <= '9')
+		n++;
+	      if (*n == '.')
+		n++;
+	    }
+	  /* the tty prefix is optional */
+	  if (strncmp(match, "tty", 3) && strncmp(n, "tty", 3) == 0)
+	    n += 3;
+	  if (strncmp(match, n, matchlen))
+	    {
+	      if (n == name && *match > '0' && *match <= '9')
+		{
+		  while (*n >= '0' && *n <= '9')
+		    n++;
+		  if (*n == '.')
+		    n++;
+		  if (strncmp(match, n, matchlen))
+		    continue;
+		}
+	      else
+		continue;
+	    }
+	  else
+	    cmatch = (*(n + matchlen) == 0);
+	  debug1("  -> matched %s\n", match);
+	}
+      sprintf(SockPath + sdirlen, "/%s", name);
+
+      debug1("stat %s\n", SockPath);
+      errno = 0;
+      debug2("uid = %d, gid = %d\n", getuid(), getgid());
+      debug2("euid = %d, egid = %d\n", geteuid(), getegid());
+      if (stat(SockPath, &st))
+	{
+	  debug1("errno = %d\n", errno);
+	  continue;
+	}
+
+      *is_sock = S_ISSOCK(st.st_mode);
+      if (!(*is_sock) && !S_ISFIFO(st.st_mode))
+	continue;
+
+      debug2("st.st_uid = %d, real_uid = %d\n", st.st_uid, real_uid);
+#ifdef SOCKDIR /* if SOCKDIR is not defined, the socket is in $HOME.
+                  in that case it does not make sense to compare uids. */
+      if ((int)st.st_uid != real_uid)
+	continue;
+#endif
+      mode = (int)st.st_mode & 0777;
+      debug1("  has mode 0%03o\n", mode);
+#ifdef MULTIUSER
+      if (multi && ((mode & 0677) != 0601))
+        {
+	  debug("  is not a MULTI-USER session");
+	  if (strcmp(multi, LoginName))
+	    {
+	      debug(" and we are in a foreign directory.\n");
+	      mode = -4;
+	    }
+	  else
+	    {
+	      debug(", but it is our own session.\n");
+	    }
+	}
+#endif
+      debug("  store it.\n");
+      if ((sent = (struct sent *)malloc(sizeof(struct sent))) == 0)
+	continue;
+      sent->next = 0;
+      sent->name = SaveStr(name);
+      sent->mode = mode;
+      *slisttail = sent;
+      slisttail = &sent->next;
+      nfound++;
+      sockfd = MakeClientSocket(0, *is_sock);
+#ifdef USE_SETEUID
+      /* MakeClientSocket sets ids back to eff */
+      xseteuid(real_uid);
+      xsetegid(real_gid);
+#endif
+      if (sockfd == -1)
+	{
+	  debug2("  MakeClientSocket failed, unreachable? %d %d\n",
+	         matchlen, wipeflag);
+	  sent->mode = -3;
+#ifndef SOCKDIR_IS_LOCAL_TO_HOST
+	  /* Unreachable - it is dead if we detect that it's local
+           * or we specified a match
+           */
+	  n = name + strlen(name) - 1;
+	  while (n != name && *n != '.')
+	    n--;
+	  if (matchlen == 0  && !(*n == '.' && n[1] && strncmp(HostName, n + 1, strlen(n + 1)) == 0))
+	    {
+	      npriv++;		/* a good socket that was not for us */
+	      continue;
+	    }
+#endif
+	  ndead++;
+	  sent->mode = -1;
+	  if (wipeflag)
+	    {
+	      if (unlink(SockPath) == 0)
+		{
+		  sent->mode = -2;
+		  nwipe++;
+		}
+	    }
+	  continue;
+	}
+
+      mode &= 0776;
+      /* Shall we connect ? */
+      debug2("  connecting: mode=%03o, rflag=%d, ", mode, rflag);
+      debug2("xflag=%d, dflag=%d ?\n", xflag, dflag);
+
+      /*
+       * mode 600: socket is detached.
+       * mode 700: socket is attached.
+       * xflag implies rflag here.
+       *
+       * fail, when socket mode mode is not 600 or 700
+       * fail, when we want to detach w/o reattach, but it already is detached.
+       * fail, when we only want to attach, but mode 700 and not xflag.
+       * fail, if none of dflag, rflag, xflag is set.
+       */
+      if ((mode != 0700 && mode != 0600) ||
+          (dflag && !rflag && !xflag && mode == 0600) ||
+	  (!dflag && rflag && mode == 0700 && !xflag) ||
+	  (!dflag && !rflag && !xflag))
+	{
+	  close(sockfd);
+	  debug("  no!\n");
+	  npriv++;		/* a good socket that was not for us */
+	  continue;
+	}
+      ngood++;
+      if (cmatch)
+	nperfect++;
+      if (fdp && (firsts == -1 || (cmatch && nperfect == 1)))
+	{
+	  if (firsts != -1)
+	    close(firsts);
+	  firsts = sockfd;
+	  firstn = sent->name;
+	  debug("  taken.\n");
+	}
+      else
+        {
+	  debug("  discarded.\n");
+	  close(sockfd);
+	}
+    }
+  (void)closedir(dirp);
+  if (!lsflag && nperfect == 1)
+    ngood = nperfect;
+  if (nfound && (lsflag || ngood != 1) && !quietflag)
+    {
+      switch(ngood)
+	{
+	case 0:
+	  Msg(0, nfound > 1 ? "There are screens on:" : "There is a screen on:");
+	  break;
+	case 1:
+	  Msg(0, nfound > 1 ? "There are several screens on:" : "There is a suitable screen on:");
+	  break;
+	default:
+	  Msg(0, "There are several suitable screens on:");
+	  break;
+	}
+      for (sent = slist; sent; sent = sent->next)
+	{
+	  switch (sent->mode)
+	    {
+	    case 0700:
+	      printf("\t%s\t(Attached)\n", sent->name);
+	      break;
+	    case 0600:
+	      printf("\t%s\t(Detached)\n", sent->name);
+	      break;
+#ifdef MULTIUSER
+	    case 0701:
+	      printf("\t%s\t(Multi, attached)\n", sent->name);
+	      break;
+	    case 0601:
+	      printf("\t%s\t(Multi, detached)\n", sent->name);
+	      break;
+#endif
+	    case -1:
+	      /* No trigraphs here! */
+	      printf("\t%s\t(Dead ?%c?)\n", sent->name, '?');
+	      break;
+	    case -2:
+	      printf("\t%s\t(Removed)\n", sent->name);
+	      break;
+	    case -3:
+	      printf("\t%s\t(Remote or dead)\n", sent->name);
+	      break;
+	    case -4:
+	      printf("\t%s\t(Private)\n", sent->name);
+	      break;
+	    }
+	}
+    }
+  if (ndead && !quietflag)
+    {
+      char *m = "Remove dead screens with 'screen -wipe'.";
+      if (wipeflag)
+        Msg(0, "%d socket%s wiped out.", nwipe, nwipe > 1 ? "s" : "");
+      else
+        Msg(0, m, ndead > 1 ? "s" : "", ndead > 1 ? "" : "es");	/* other args for nethack */
+    }
+  if (firsts != -1)
+    {
+      sprintf(SockPath + sdirlen, "/%s", firstn);
+      *fdp = firsts;
+    }
+  else
+    SockPath[sdirlen] = 0;
+  for (sent = slist; sent; sent = nsent)
+    {
+      nsent = sent->next;
+      free(sent->name);
+      free((char *)sent);
+    }
+#ifdef USE_SETEUID
+  xseteuid(eff_uid);
+  xsetegid(eff_gid);
+#endif
+  if (notherp)
+    *notherp = npriv;
+  if (nfoundp)
+    *nfoundp = nfound - nwipe;
+  return ngood;
+}
+
+/* FIFO (legacy mode) */
+static int
+MakeServerFifo()
+{
+  register int s;
+  struct stat st;
+
+#ifdef USE_SETEUID
+  xseteuid(real_uid);
+  xsetegid(real_gid);
+#endif
+  s = open(SockPath, O_WRONLY | O_NONBLOCK);
+  if (s >= 0)
+    {
+      debug("huii, my fifo already exists??\n");
+      if (quietflag)
+        {
+          Kill(D_userpid, SIG_BYE);
+          eexit(11);
+        }
+
+      Msg(0, "There is already a screen running on %s.", Filename(SockPath));
+
+      if (stat(SockPath, &st) < 0)
+        Panic(errno, "stat");
+
+#ifdef SOCKDIR /* if SOCKDIR is not defined, the socket is in $HOME.           \
+                  in that case it does not make sense to compare uids. */
+      if ((int)st.st_uid != real_uid)
+        Panic(0, "Unfortunately you are not its owner.");
+#endif
+      if ((st.st_mode & 0700) == 0600)
+        Panic(0, "To resume it, use \"screen -r\"");
+      else
+        Panic(0, "It is not detached.");
+      /* NOTREACHED */
+    }
+# ifdef USE_SETEUID
+  (void) unlink(SockPath);
+  if (mkfifo(SockPath, SOCKMODE) < 0)
+    Panic(0, "mkfifo %s failed", SockPath);
+#  ifdef BROKEN_PIPE
+  s = open(SockPath, O_RDWR | O_NONBLOCK, 0);
+#  else
+  s = open(SockPath, O_RDONLY | O_NONBLOCK, 0);
+#  endif
+  if (s < 0)
+    Panic(errno, "open fifo %s", SockPath);
+
+  xseteuid(eff_uid);
+  xsetegid(eff_gid);
+
+  return s;
+
+# else /* !USE_SETEUID */
+  if (UserContext() > 0)
+    {
+      (void) unlink(SockPath);
+      UserReturn(mkfifo(SockPath, SOCKMODE));
+    }
+  if (UserStatus())
+    Panic(0, "mkfifo %s failed", SockPath);
+#  ifdef BROKEN_PIPE
+  s = secopen(SockPath, O_RDWR | O_NONBLOCK, 0);
+#  else
+  s = secopen(SockPath, O_RDONLY | O_NONBLOCK, 0);
+#  endif
+  if (s < 0)
+    Panic(errno, "open fifo %s", SockPath);
+
+  return s;
+# endif /* !USE_SETEUID */
+}
+
+static int
+MakeClientFifo(err)
+int err;
+{
+  register int s = 0;
+
+  s = secopen(SockPath, O_WRONLY | O_NONBLOCK, 0);
+  if (s >= 0)
+    {
+      (void) fcntl(s, F_SETFL, 0);
+      return s;
+    }
+
+  if (err)
+    Msg(errno, "%s", SockPath);
+  debug2("MakeClientSocket() open %s failed (%d)\n", SockPath, errno);
+
+  return -1;
+}
+
+/* Unix Domain Sockets */
+static int
+MakeServerUnixSocket()
+{
+  register int s;
+  struct sockaddr_un a;
+  struct stat st;
+
+  s = socket(AF_UNIX, SOCK_STREAM, 0);
+  if (s < 0)
+    Panic(errno, "socket");
+
+  a.sun_family = AF_UNIX;
+  strncpy(a.sun_path, SockPath, sizeof(a.sun_path));
+  a.sun_path[sizeof(a.sun_path) - 1] = 0;
+
+# ifdef USE_SETEUID
+  xseteuid(real_uid);
+  xsetegid(real_gid);
+# endif
+  if (connect(s, (struct sockaddr *) &a, strlen(SockPath) + 2) != -1)
+    {
+      debug("oooooh! socket already is alive!\n");
+      if (quietflag)
+        {
+          Kill(D_userpid, SIG_BYE);
+          /*
+           * oh, well. nobody receives that return code. papa
+           * dies by signal.
+           */
+          eexit(11);
+        }
+      Msg(0, "There is already a screen running on %s.", Filename(SockPath));
+
+      if (stat(SockPath, &st) < 0)
+        Panic(errno, "stat");
+
+#ifdef SOCKDIR /* if SOCKDIR is not defined, the socket is in $HOME.           \
+                  in that case it does not make sense to compare uids. */
+      if (st.st_uid != real_uid)
+        Panic(0, "Unfortunately you are not its owner.");
+#endif
+      if ((st.st_mode & 0700) == 0600)
+        Panic(0, "To resume it, use \"screen -r\"");
+      else
+        Panic(0, "It is not detached.");
+      /* NOTREACHED */
+    }
+
+#if defined(m88k) || defined(sysV68)
+  close(s); /* we get bind: Invalid argument if this is not done */
+  s = socket(AF_UNIX, SOCK_STREAM, 0);
+  if (s < 0)
+    Panic(errno, "reopen socket");
+#endif
+  (void) unlink(SockPath);
+  if (bind(s, (struct sockaddr *) & a, strlen(SockPath) + 2) == -1)
+    Panic(errno, "bind (%s)", SockPath);
+#ifdef SOCK_NOT_IN_FS
+  {
+    int f = secopen(SockPath, O_RDWR | O_CREAT, SOCKMODE);
+    if (f < 0)
+      Panic(errno, "shadow socket open");
+    close(f);
+  }
+#else
+  chmod(SockPath, SOCKMODE);
+#ifndef USE_SETEUID
+  chown(SockPath, real_uid, real_gid);
+#endif
+#endif /* SOCK_NOT_IN_FS */
+  if (listen(s, 5) == -1)
+    Panic(errno, "listen");
+#ifdef F_SETOWN
+  fcntl(s, F_SETOWN, getpid());
+  debug1("Serversocket owned by %d\n", fcntl(s, F_GETOWN, 0));
+#endif /* F_SETOWN */
+#ifdef USE_SETEUID
+  xseteuid(eff_uid);
+  xsetegid(eff_gid);
+#endif
+  return s;
+}
+
+static int
+MakeClientUnixSocket(err)
+int err;
+{
+  register int s;
+  struct sockaddr_un a;
+
+  s = socket(AF_UNIX, SOCK_STREAM, 0);
+  if (s < 0)
+    Panic(errno, "socket");
+
+  a.sun_family = AF_UNIX;
+  strncpy(a.sun_path, SockPath, sizeof(a.sun_path));
+  a.sun_path[sizeof(a.sun_path) - 1] = 0;
+#ifdef USE_SETEUID
+  xseteuid(real_uid);
+  xsetegid(real_gid);
+#else
+  if (access(SockPath, W_OK))
+    {
+      if (err)
+        Msg(errno, "%s", SockPath);
+      debug2("MakeClientSocket: access(%s): %d.\n", SockPath, errno);
+      close(s);
+      return -1;
+    }
+#endif
+  if (connect(s, (struct sockaddr *)&a, strlen(SockPath) + 2) == -1)
+    {
+      if (err)
+        Msg(errno, "%s: connect", SockPath);
+      debug("MakeClientSocket: connect failed.\n");
+      close(s);
+      s = -1;
+    }
+#ifdef USE_SETEUID
+  xseteuid(eff_uid);
+  xsetegid(eff_gid);
+#endif
+  return s;
+}
+
+int
+MakeServerSocket(socket)
+bool socket;
+{
+  if (socket)
+    return MakeServerUnixSocket();
+
+  return MakeServerFifo();
+}
+
+int
+MakeClientSocket(err, socket)
+int err;
+bool socket;
+{
+  if (socket)
+    return MakeClientUnixSocket(err);
+
+  return MakeClientFifo(err);
+}
+
+/*
+**
+**       Message send and receive routines
+**
+*/
+
+void
+SendCreateMsg(sty, nwin)
+char *sty;
+struct NewWindow *nwin;
+{
+  int s;
+  struct msg m;
+  register char *p;
+  register int len, n;
+  char **av;
+  bool is_socket;
+
+#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);
+  debug1("SendCreateMsg() to '%s'\n", SockPath);
+  bzero((char *)&m, sizeof(m));
+  m.type = MSG_CREATE;
+  strncpy(m.m_tty, attach_tty, sizeof(m.m_tty) - 1);
+  m.m_tty[sizeof(m.m_tty) - 1] = 0;
+  p = m.m.create.line;
+  n = 0;
+  if (nwin->args != nwin_undef.args)
+    for (av = nwin->args; *av && n < MAXARGS - 1; ++av, ++n)
+      {
+        len = strlen(*av) + 1;
+        if (p + len >= m.m.create.line + sizeof(m.m.create.line) - 1)
+	  break;
+        strcpy(p, *av);
+        p += len;
+      }
+  if (nwin->aka != nwin_undef.aka && p + strlen(nwin->aka) + 1 < m.m.create.line + sizeof(m.m.create.line))
+    strcpy(p, nwin->aka);
+  else
+    *p = '\0';
+  m.m.create.nargs = n;
+  m.m.create.aflag = nwin->aflag;
+  m.m.create.flowflag = nwin->flowflag;
+  m.m.create.lflag = nwin->lflag;
+  m.m.create.hheight = nwin->histheight;
+  if (getcwd(m.m.create.dir, sizeof(m.m.create.dir)) == 0)
+    {
+      Msg(errno, "getcwd");
+      return;
+    }
+  if (nwin->term != nwin_undef.term)
+    strncpy(m.m.create.screenterm, nwin->term, MAXTERMLEN);
+  m.m.create.screenterm[MAXTERMLEN] = '\0';
+  m.protocol_revision = MSG_REVISION;
+  debug1("SendCreateMsg writing '%s'\n", m.m.create.line);
+  if (write(s, (char *) &m, sizeof m) != sizeof m)
+    Msg(errno, "write");
+  close(s);
+}
+
+int
+SendErrorMsg(tty, buf)
+char *tty, *buf;
+{
+  int s;
+  struct msg m;
+  bool is_socket;
+
+  strncpy(m.m.message, buf, sizeof(m.m.message) - 1);
+  m.m.message[sizeof(m.m.message) - 1] = 0;
+  is_socket = IsSocket(SockPath);
+  s = MakeClientSocket(0, is_socket);
+  if (s < 0)
+    return -1;
+  m.type = MSG_ERROR;
+  strncpy(m.m_tty, tty, sizeof(m.m_tty) - 1);
+  m.m_tty[sizeof(m.m_tty) - 1] = 0;
+  m.protocol_revision = MSG_REVISION;
+  debug1("SendErrorMsg(): writing to '%s'\n", SockPath);
+  (void) write(s, (char *) &m, sizeof m);
+  close(s);
+  return 0;
+}
+
+static void
+ExecCreate(mp)
+struct msg *mp;
+{
+  struct NewWindow nwin;
+  char *args[MAXARGS];
+  register int n;
+  register char **pp = args, *p = mp->m.create.line;
+  char buf[20];
+
+  nwin = nwin_undef;
+  n = mp->m.create.nargs;
+  if (n > MAXARGS - 1)
+    n = MAXARGS - 1;
+  /* ugly hack alert... should be done by the frontend! */
+  if (n)
+    {
+      int l, num;
+
+      l = strlen(p);
+      if (IsNumColon(p, 10, buf, sizeof(buf)))
+	{
+	  if (*buf)
+	    nwin.aka = buf;
+	  num = atoi(p);
+	  if (num < 0 || num > maxwin - 1)
+	    num = 0;
+	  nwin.StartAt = num;
+	  p += l + 1;
+	  n--;
+	}
+    }
+  for (; n > 0; n--)
+    {
+      *pp++ = p;
+      p += strlen(p) + 1;
+    }
+  *pp = 0;
+  if (*p)
+    nwin.aka = p;
+  if (*args)
+    nwin.args = args;
+  nwin.aflag = mp->m.create.aflag;
+  nwin.flowflag = mp->m.create.flowflag;
+  if (*mp->m.create.dir)
+    nwin.dir = mp->m.create.dir;
+  nwin.lflag = mp->m.create.lflag;
+  nwin.histheight = mp->m.create.hheight;
+  if (*mp->m.create.screenterm)
+    nwin.term =  mp->m.create.screenterm;
+  MakeWindow(&nwin);
+}
+
+static int
+CheckPid(pid)
+int pid;
+{
+  debug1("Checking pid %d\n", pid);
+  if (pid < 2)
+    return -1;
+  if (eff_uid == real_uid)
+    return kill(pid, 0);
+  if (UserContext() > 0)
+    UserReturn(kill(pid, 0));
+  return UserStatus();
+}
+
+#ifdef hpux
+/*
+ * From: "F. K. Bruner" <napalm@ugcs.caltech.edu>
+ * From: "Dan Egnor" <egnor@oracorp.com> Tue Aug 10 06:56:45 1993
+ * The problem is that under HPUX (and possibly other systems too) there are
+ * two equivalent device files for each pty/tty device:
+ * /dev/ttyxx == /dev/pty/ttyxx
+ * /dev/ptyxx == /dev/ptym/ptyxx
+ * I didn't look into the exact specifics, but I've run across this problem
+ * before: Even if you open /dev/ttyxx as fds 0 1 & 2 for a process, if that
+ * process calls the system to determine its tty, it'll get /dev/pty/ttyxx.
+ *
+ * Earlier versions seemed to work -- wonder what they did.
+ */
+static int
+ttycmp(s1, s2)
+char *s1, *s2;
+{
+  if (strlen(s1) > 5) s1 += strlen(s1) - 5;
+  if (strlen(s2) > 5) s2 += strlen(s2) - 5;
+  return strcmp(s1, s2);
+}
+# define TTYCMP(a, b) ttycmp(a, b)
+#else
+# define TTYCMP(a, b) strcmp(a, b)
+#endif
+
+static int
+CreateTempDisplay(m, recvfd, wi)
+struct msg *m;
+int recvfd;
+struct win *wi;
+{
+  int pid;
+  int attach;
+  char *user;
+  int i;
+  struct mode Mode;
+  struct display *olddisplays = displays;
+
+  switch (m->type)
+    {
+      case MSG_CONT:
+      case MSG_ATTACH:
+	pid = m->m.attach.apid;
+	user = m->m.attach.auser;
+	attach = 1;
+	break;
+#ifdef REMOTE_DETACH
+      case MSG_DETACH:
+# ifdef POW_DETACH
+      case MSG_POW_DETACH:
+# endif				/* POW_DETACH */
+	pid = m->m.detach.dpid;
+	user = m->m.detach.duser;
+	attach = 0;
+	break;
+#endif
+      default:
+	return -1;
+    }
+
+  if (CheckPid(pid))
+    {
+      Msg(0, "Attach attempt with bad pid(%d)!", pid);
+      return -1;
+    }
+  if (recvfd != -1)
+    {
+      int ret;
+      char ttyname_in_ns[MAXPATHLEN];
+      char *myttyname;
+
+      i = recvfd;
+      recvfd = -1;
+      memset(&ttyname_in_ns, 0, sizeof(ttyname_in_ns));
+      errno = 0;
+      myttyname = GetPtsPathOrSymlink(i);
+      if (myttyname && errno == ENODEV)
+        {
+          ret = readlink(myttyname, ttyname_in_ns, sizeof(ttyname_in_ns));
+          if (ret < 0 || (size_t)ret >= sizeof(ttyname_in_ns))
+            {
+	      Msg(errno, "Could not perform necessary sanity checks on pts device.");
+	      close(i);
+	      Kill(pid, SIG_BYE);
+	      return -1;
+            }
+          if (strcmp(ttyname_in_ns, m->m_tty))
+            {
+	      Msg(errno, "Attach: passed fd does not match tty: %s - %s!", ttyname_in_ns, m->m_tty[0] != '\0' ? m->m_tty : "(null)");
+	      close(i);
+	      Kill(pid, SIG_BYE);
+	      return -1;
+	    }
+	  /* m->m_tty so far contains the actual name of the pts device in the
+	   * its (e.g. /dev/pts/0). This name however is not valid in the
+	   * current namespace. So after we verified that the symlink returned
+	   * by GetPtsPathOrSymlink() refers to the same pts device in this
+	   * namespace we need to update m->m_tty to use that symlink for all
+	   * future operations.
+	   */
+          strncpy(m->m_tty, myttyname, sizeof(m->m_tty) - 1);
+          m->m_tty[sizeof(m->m_tty) - 1] = 0;
+        }
+      else if (myttyname == 0 || strcmp(myttyname, m->m_tty))
+	{
+	  Msg(errno, "Attach: passed fd does not match tty: %s - %s!", m->m_tty, myttyname ? myttyname : "NULL");
+	  close(i);
+	  Kill(pid, SIG_BYE);
+	  return -1;
+	}
+    }
+  else if ((i = secopen(m->m_tty, O_RDWR | O_NONBLOCK, 0)) < 0)
+    {
+      Msg(errno, "Attach: Could not open %s!", m->m_tty);
+      Kill(pid, SIG_BYE);
+      return -1;
+    }
+#ifdef MULTIUSER
+  if (attach)
+    Kill(pid, SIGCONT);
+#endif
+
+#if defined(ultrix) || defined(pyr) || defined(NeXT)
+  brktty(i);	/* for some strange reason this must be done */
+#endif
+
+  if (attach)
+    {
+      if (display || wi)
+	{
+	  write(i, "Attaching from inside of screen?\n", 33);
+	  close(i);
+	  Kill(pid, SIG_BYE);
+	  Msg(0, "Attach msg ignored: coming from inside.");
+	  return -1;
+	}
+
+#ifdef MULTIUSER
+      if (strcmp(user, LoginName))
+	if (*FindUserPtr(user) == 0)
+	  {
+	      write(i, "Access to session denied.\n", 26);
+	      close(i);
+	      Kill(pid, SIG_BYE);
+	      Msg(0, "Attach: access denied for user %s.", user);
+	      return -1;
+	  }
+#endif
+
+      debug2("RecMsg: apid %d is o.k. and we just opened '%s'\n", pid, m->m_tty);
+#ifndef MULTI
+      if (displays)
+	{
+	  write(i, "Screen session in use.\n", 23);
+	  close(i);
+	  Kill(pid, SIG_BYE);
+	  return -1;
+	}
+#endif
+    }
+
+  /* create new display */
+  GetTTY(i, &Mode);
+  if (MakeDisplay(user, m->m_tty, attach ? m->m.attach.envterm : "", i, pid, &Mode) == 0)
+    {
+      write(i, "Could not make display.\n", 24);
+      close(i);
+      Msg(0, "Attach: could not make display for user %s", user);
+      Kill(pid, SIG_BYE);
+      return -1;
+    }
+#ifdef ENCODINGS
+  if (attach)
+    {
+# ifdef UTF8
+      D_encoding = m->m.attach.encoding == 1 ? UTF8 : m->m.attach.encoding ? m->m.attach.encoding - 1 : 0;
+# else
+      D_encoding = m->m.attach.encoding ? m->m.attach.encoding - 1 : 0;
+# endif
+      if (D_encoding < 0 || !EncodingName(D_encoding))
+	D_encoding = 0;
+    }
+#endif
+
+  if (iflag && olddisplays)
+    {
+      iflag = 0;
+#if defined(TERMIO) || defined(POSIX)
+      olddisplays->d_NewMode.tio.c_cc[VINTR] = VDISABLE;
+      olddisplays->d_NewMode.tio.c_lflag &= ~ISIG;
+#else /* TERMIO || POSIX */
+      olddisplays->d_NewMode.m_tchars.t_intrc = -1;
+#endif /* TERMIO || POSIX */
+      SetTTY(olddisplays->d_userfd, &olddisplays->d_NewMode);
+    }
+  SetMode(&D_OldMode, &D_NewMode, D_flow, iflag);
+  SetTTY(D_userfd, &D_NewMode);
+  if (fcntl(D_userfd, F_SETFL, FNBLOCK))
+    Msg(errno, "Warning: NBLOCK fcntl failed");
+  return 0;
+}
+
+void
+ReceiveMsg()
+{
+  int left, len;
+  static struct msg m;
+  char *p;
+  int ns = ServerSocket;
+  struct win *wi;
+  int recvfd = -1;
+  struct acluser *user;
+  bool is_socket;
+
+  /* Socket specific variables. */
+  struct sockaddr_un a;
+  struct msghdr msg;
+  struct iovec iov;
+  char control[1024];
+
+  is_socket = IsSocket(SockPath);
+  if (!is_socket)
+    {
+      debug("Ha, there was someone knocking on my fifo??\n");
+      if (fcntl(ServerSocket, F_SETFL, 0) == -1)
+        Panic(errno, "BLOCK fcntl");
+      p = (char *)&m;
+      left = sizeof(m);
+    }
+  else
+    {
+      len = sizeof(a);
+      debug("Ha, there was someone knocking on my socket??\n");
+      if ((ns = accept(ns, (struct sockaddr *)&a, (void *)&len)) < 0)
+        {
+          Msg(errno, "accept");
+          return;
+        }
+
+      p = (char *)&m;
+      left = sizeof(m);
+      bzero(&msg, sizeof(msg));
+      iov.iov_base = &m;
+      iov.iov_len = left;
+      msg.msg_iov = &iov;
+      msg.msg_iovlen = 1;
+      msg.msg_controllen = sizeof(control);
+      msg.msg_control = &control;
+      while (left > 0)
+        {
+          len = recvmsg(ns, &msg, 0);
+          if (len < 0 && errno == EINTR)
+            continue;
+          if (len < 0)
+            {
+              close(ns);
+              Msg(errno, "read");
+              return;
+            }
+          if (msg.msg_controllen)
+            {
+              struct cmsghdr *cmsg;
+              for (cmsg = CMSG_FIRSTHDR(&msg); cmsg;
+                   cmsg = CMSG_NXTHDR(&msg, cmsg))
+                {
+                  int cl;
+                  char *cp;
+                  if (cmsg->cmsg_level != SOL_SOCKET ||
+                      cmsg->cmsg_type != SCM_RIGHTS)
+                    continue;
+                  cp = (char *)CMSG_DATA(cmsg);
+                  cl = cmsg->cmsg_len;
+                  while (cl >= CMSG_LEN(sizeof(int)))
+                    {
+                      int passedfd;
+                      bcopy(cp, &passedfd, sizeof(int));
+                      if (recvfd >= 0 && passedfd != recvfd)
+                        close(recvfd);
+                      recvfd = passedfd;
+                      cl -= CMSG_LEN(sizeof(int));
+                    }
+                }
+            }
+          p += len;
+          left -= len;
+          break;
+        }
+    }
+
+  while (left > 0)
+    {
+      len = read(ns, p, left);
+      if (len < 0 && errno == EINTR)
+        continue;
+      if (len <= 0)
+        break;
+      p += len;
+      left -= len;
+    }
+
+  if (!is_socket)
+    {
+#ifndef BROKEN_PIPE
+      /* Reopen pipe to prevent EOFs at the select() call */
+      close(ServerSocket);
+      if ((ServerSocket = secopen(SockPath, O_RDONLY | O_NONBLOCK, 0)) < 0)
+        Panic(errno, "reopen fifo %s", SockPath);
+      evdeq(&serv_read);
+      serv_read.fd = ServerSocket;
+      evenq(&serv_read);
+#endif
+    }
+  else
+    {
+      close(ns);
+    }
+
+  if (len < 0)
+    {
+      Msg(errno, "read");
+      if (recvfd != -1)
+        close(recvfd);
+      return;
+    }
+  if (left > 0)
+    {
+      if (left != sizeof(m))
+        Msg(0, "Message %d of %d bytes too small", left, (int)sizeof(m));
+      else
+        debug("No data on socket.\n");
+      return;
+    }
+  if (m.protocol_revision != MSG_REVISION)
+    {
+      if (recvfd != -1)
+        close(recvfd);
+      Msg(0, "Invalid message (magic 0x%08x).", m.protocol_revision);
+      return;
+    }
+
+  debug2("*** RecMsg: type %d tty %s\n", m.type, m.m_tty);
+  if (m.type != MSG_ATTACH && recvfd != -1)
+    {
+      close(recvfd);
+      recvfd = -1;
+    }
+
+  for (display = displays; display; display = display->d_next)
+    if (TTYCMP(D_usertty, m.m_tty) == 0)
+      break;
+  debug2("display: %s display %sfound\n", m.m_tty, display ? "" : "not ");
+  wi = 0;
+  if (!display)
+    {
+      for (wi = windows; wi; wi = wi->w_next)
+        if (!TTYCMP(m.m_tty, wi->w_tty))
+          {
+            /* XXX: hmmm, rework this? */
+            display =
+                wi->w_layer.l_cvlist ? wi->w_layer.l_cvlist->c_display : 0;
+            debug2("but window %s %sfound.\n", m.m_tty,
+                   display ? "" : "(backfacing)");
+            break;
+          }
+    }
+
+  /* Remove the status to prevent garbage on the screen */
+  if (display && D_status)
+    RemoveStatus();
+
+  if (display && !D_tcinited && m.type != MSG_HANGUP)
+    {
+      if (recvfd != -1)
+        close(recvfd);
+      return; /* ignore messages for bad displays */
+    }
+
+  switch (m.type)
+    {
+      case MSG_WINCH:
+        if (display)
+          CheckScreenSize(1); /* Change fore */
+        break;
+      case MSG_CREATE:
+        /*
+         * the window that issued the create message need not be an
+         * active
+         * window. Then we create the window without having a display.
+         * Resulting in another inactive window.
+         */
+        ExecCreate(&m);
+        break;
+      case MSG_CONT:
+        if (display && D_userpid != 0 && kill(D_userpid, 0) == 0)
+          break; /* Intruder Alert */
+        debug2("RecMsg: apid=%d,was %d\n", m.m.attach.apid,
+               display ? D_userpid : 0);
+      /* FALLTHROUGH */
+
+      case MSG_ATTACH:
+        if (CreateTempDisplay(&m, recvfd, wi))
+          break;
+#ifdef PASSWORD
+        if (D_user->u_password && *D_user->u_password)
+          AskPassword(&m);
+        else
+#endif
+          FinishAttach(&m);
+        break;
+      case MSG_ERROR:
+        Msg(0, "%s", m.m.message);
+        break;
+      case MSG_HANGUP:
+        if (!wi) /* ignore hangups from inside */
+          Hangup();
+        break;
+#ifdef REMOTE_DETACH
+      case MSG_DETACH:
+#ifdef POW_DETACH
+      case MSG_POW_DETACH:
+#endif /* POW_DETACH */
+#ifdef PASSWORD
+        user = *FindUserPtr(m.m.detach.duser);
+        if (user && user->u_password && *user->u_password)
+          {
+            if (CreateTempDisplay(&m, recvfd, 0))
+              break;
+            AskPassword(&m);
+          }
+        else
+#endif /* PASSWORD */
+          FinishDetach(&m);
+        break;
+#endif
+      case MSG_QUERY:
+        {
+          char *oldSockPath = SaveStr(SockPath);
+          strcpy(SockPath, m.m.command.writeback);
+          bool is_socket = IsSocket(SockPath);
+          int s = MakeClientSocket(0, is_socket);
+          strcpy(SockPath, oldSockPath);
+          Free(oldSockPath);
+          if (s >= 0)
+            {
+              queryflag = s;
+              DoCommandMsg(&m);
+              close(s);
+            }
+          else
+            queryflag = -1;
+
+          Kill(m.m.command.apid,
+               (queryflag >= 0)
+                   ? SIGCONT
+                   : SIG_BYE); /* Send SIG_BYE if an error happened */
+          queryflag = -1;
+        }
+        break;
+      case MSG_COMMAND:
+        DoCommandMsg(&m);
+        break;
+      default:
+        Msg(0, "Invalid message (type %d).", m.type);
+    }
+}
+
+void
+ReceiveRaw(s)
+int s;
+{
+  char rd[256];
+  int len = 0;
+  struct sockaddr_un a;
+  bool is_socket;
+
+  is_socket = IsSocket(SockPath);
+  if (!is_socket)
+    {
+      if (fcntl(s, F_SETFL, 0) < 0)
+        Panic(errno, "BLOCK fcntl");
+    }
+  else
+    {
+      len = sizeof(a);
+      s = accept(s, (struct sockaddr *)&a, (void *)&len);
+      if (s < 0)
+        {
+          Msg(errno, "accept");
+          return;
+        }
+    }
+
+  while ((len = read(s, rd, 255)) > 0)
+    {
+      rd[len] = 0;
+      printf("%s", rd);
+    }
+  close(s);
+}
+
+#if defined(_SEQUENT_)
+#undef connect
+/*
+ *  sequent_ptx socket emulation must have mode 000 on the socket!
+ */
+static int
+sconnect(s, sapp, len)
+int s, len;
+struct sockaddr *sapp;
+{
+  register struct sockaddr_un *sap;
+  struct stat st;
+  int x;
+
+  sap = (struct sockaddr_un *)sapp;
+  if (stat(sap->sun_path, &st))
+    return -1;
+  chmod(sap->sun_path, 0);
+  x = connect(s, (struct sockaddr *) sap, len);
+  chmod(sap->sun_path, st.st_mode);
+  return x;
+}
+#endif
+
+
+/*
+ * Set the mode bits of the socket to the current status
+ */
+int
+chsock()
+{
+  int r, euid = geteuid();
+  if (euid != real_uid)
+    {
+      if (UserContext() <= 0)
+        return UserStatus();
+    }
+  r = chmod(SockPath, SOCKMODE);
+  /*
+   * Sockets usually reside in the /tmp/ area, where sysadmin scripts
+   * may be happy to remove old files. We manually prevent the socket
+   * from becoming old. (chmod does not touch mtime).
+   */
+  (void)utimes(SockPath, NULL);
+
+  if (euid != real_uid)
+    UserReturn(r);
+  return r;
+}
+
+/*
+ * Try to recreate the socket/pipe
+ */
+int
+RecoverSocket()
+{
+  bool is_socket;
+
+  close(ServerSocket);
+  if ((int)geteuid() != real_uid)
+    {
+      if (UserContext() > 0)
+	UserReturn(unlink(SockPath));
+      (void)UserStatus();
+    }
+  else
+    (void) unlink(SockPath);
+
+  is_socket = IsSocket(SockPath);
+  if ((ServerSocket = MakeServerSocket(is_socket)) < 0)
+    return 0;
+  evdeq(&serv_read);
+  serv_read.fd = ServerSocket;
+  evenq(&serv_read);
+  return 1;
+}
+
+
+static void
+FinishAttach(m)
+struct msg *m;
+{
+  char *p;
+  int pid;
+  int noshowwin;
+  struct win *wi;
+
+  ASSERT(display);
+  pid = D_userpid;
+
+#ifdef REMOTE_DETACH
+  if (m->m.attach.detachfirst == MSG_DETACH
+# ifdef POW_DETACH
+      || m->m.attach.detachfirst == MSG_POW_DETACH
+# endif
+     )
+    FinishDetach(m);
+#endif
+
+#if defined(pyr) || defined(xelos) || defined(sequent)
+  /*
+   * Kludge for systems with braindamaged termcap routines,
+   * which evaluate $TERMCAP, regardless whether it describes
+   * the correct terminal type or not.
+   */
+  debug("unsetenv(TERMCAP) in case of a different terminal");
+  unsetenv("TERMCAP");
+#endif
+
+  /*
+   * We reboot our Terminal Emulator. Forget all we knew about
+   * the old terminal, reread the termcap entries in .screenrc
+   * (and nothing more from .screenrc is read. Mainly because
+   * I did not check, whether a full reinit is safe. jw)
+   * and /etc/screenrc, and initialise anew.
+   */
+  if (extra_outcap)
+    free(extra_outcap);
+  if (extra_incap)
+    free(extra_incap);
+  extra_incap = extra_outcap = 0;
+  debug2("Message says size (%dx%d)\n", m->m.attach.columns, m->m.attach.lines);
+#ifdef ETCSCREENRC
+# ifdef ALLOW_SYSSCREENRC
+  if ((p = getenv("SYSSCREENRC")))
+    StartRc(p, 1);
+  else
+# endif
+    StartRc(ETCSCREENRC, 1);
+#endif
+  StartRc(RcFileName, 1);
+  if (InitTermcap(m->m.attach.columns, m->m.attach.lines))
+    {
+      FreeDisplay();
+      Kill(pid, SIG_BYE);
+      return;
+    }
+  MakeDefaultCanvas();
+  InitTerm(m->m.attach.adaptflag);	/* write init string on fd */
+  if (displays->d_next == 0)
+    (void) chsock();
+  signal(SIGHUP, SigHup);
+  if (m->m.attach.esc != -1 && m->m.attach.meta_esc != -1)
+    {
+      D_user->u_Esc = m->m.attach.esc;
+      D_user->u_MetaEsc = m->m.attach.meta_esc;
+    }
+
+#ifdef UTMPOK
+  /*
+   * we set the Utmp slots again, if we were detached normally
+   * and if we were detached by ^Z.
+   * don't log zomies back in!
+   */
+  RemoveLoginSlot();
+  if (displays->d_next == 0)
+    for (wi = windows; wi; wi = wi->w_next)
+      if (wi->w_ptyfd >= 0 && wi->w_slot != (slot_t) -1)
+	SetUtmp(wi);
+#endif
+
+  D_fore = NULL;
+  if (layout_attach)
+    {
+      struct layout *lay = layout_attach;
+      if (lay == &layout_last_marker)
+	lay = layout_last;
+      if (lay)
+	{
+	  LoadLayout(lay, &D_canvas);
+	  SetCanvasWindow(D_forecv, 0);
+	}
+    }
+  /*
+   * there may be a window that we remember from last detach:
+   */
+  debug1("D_user->u_detachwin = %d\n", D_user->u_detachwin);
+  if (D_user->u_detachwin >= 0)
+    fore = wtab[D_user->u_detachwin];
+  else
+    fore = 0;
+
+  /* Wayne wants us to restore the other window too. */
+  if (D_user->u_detachotherwin >= 0)
+    D_other = wtab[D_user->u_detachotherwin];
+
+  noshowwin = 0;
+  if (*m->m.attach.preselect)
+    {
+      if (!strcmp(m->m.attach.preselect, "="))
+        fore = 0;
+      else if (!strcmp(m->m.attach.preselect, "-"))
+	{
+          fore = 0;
+	  noshowwin = 1;
+	}
+      else if (!strcmp(m->m.attach.preselect, "+"))
+	{
+	  struct action newscreen;
+	  char *na = 0;
+	  newscreen.nr = RC_SCREEN;
+	  newscreen.args = &na;
+	  newscreen.quiet = 0;
+	  DoAction(&newscreen, -1);
+	}
+      else
+        fore = FindNiceWindow(fore, m->m.attach.preselect);
+    }
+  else
+    fore = FindNiceWindow(fore, 0);
+  if (fore)
+    SetForeWindow(fore);
+  else if (!noshowwin)
+    {
+#ifdef MULTIUSER
+      if (!AclCheckPermCmd(D_user, ACL_EXEC, &comms[RC_WINDOWLIST]))
+#endif
+	{
+	  struct display *olddisplay = display;
+	  flayer = D_forecv->c_layer;
+	  display_windows(1, WLIST_NUM, (struct win *)0);
+	  noshowwin = 1;
+	  display = olddisplay;	/* display_windows can change display */
+	}
+    }
+  Activate(0);
+  ResetIdle();
+  if (!D_fore && !noshowwin)
+    ShowWindows(-1);
+  if (displays->d_next == 0 && console_window)
+    {
+      if (TtyGrabConsole(console_window->w_ptyfd, 1, "reattach") == 0)
+	Msg(0, "console %s is on window %d", HostName, console_window->w_number);
+    }
+  debug("activated...\n");
+
+# if defined(DEBUG) && defined(SIG_NODEBUG)
+  if (!dfp)
+    {
+      sleep(1);
+      debug1("Attacher %d must not debug, as we have debug off.\n", pid);
+      kill(pid, SIG_NODEBUG);
+    }
+# endif /* SIG_NODEBUG */
+}
+
+static void
+FinishDetach(m)
+struct msg *m;
+{
+  struct display *next, **d, *det;
+  int pid;
+
+  if (m->type == MSG_ATTACH)
+    pid = D_userpid;
+  else
+    pid = m->m.detach.dpid;
+
+  /* Remove the temporary display prompting for the password from the list */
+  for (d = &displays; (det = *d); d = &det->d_next)
+    {
+      if (det->d_userpid == pid)
+	break;
+    }
+  if (det)
+    {
+      *d = det->d_next;
+      det->d_next = 0;
+    }
+
+  for (display = displays; display; display = next)
+    {
+      next = display->d_next;
+# ifdef POW_DETACH
+      if (m->type == MSG_POW_DETACH)
+	Detach(D_REMOTE_POWER);
+      else
+# endif				/* POW_DETACH */
+      if (m->type == MSG_DETACH)
+	Detach(D_REMOTE);
+      else if (m->type == MSG_ATTACH)
+	{
+#ifdef POW_DETACH
+	  if (m->m.attach.detachfirst == MSG_POW_DETACH)
+	    Detach(D_REMOTE_POWER);
+	  else
+#endif
+	  if (m->m.attach.detachfirst == MSG_DETACH)
+	    Detach(D_REMOTE);
+	}
+    }
+  display = displays = det;
+  if (m->type != MSG_ATTACH)
+    {
+      if (display)
+	FreeDisplay();
+      Kill(pid, SIGCONT);
+    }
+}
+
+#ifdef PASSWORD
+static void PasswordProcessInput __P((char *, int));
+
+struct pwdata {
+  int l;
+  char buf[MAXLOGINLEN + 1];
+  struct msg m;
+};
+
+static void
+AskPassword(m)
+struct msg *m;
+{
+  struct pwdata *pwdata;
+  ASSERT(display);
+  pwdata = (struct pwdata *)malloc(sizeof(struct pwdata));
+  if (!pwdata)
+    Panic(0, "%s", strnomem);
+  pwdata->l = 0;
+  pwdata->m = *m;
+  D_processinputdata = (char *)pwdata;
+  D_processinput = PasswordProcessInput;
+  AddStr("Screen password: ");
+}
+
+static void
+PasswordProcessInput(ibuf, ilen)
+char *ibuf;
+int ilen;
+{
+  struct pwdata *pwdata;
+  int c, l;
+  char *up;
+  int pid = D_userpid;
+
+  pwdata = (struct pwdata *)D_processinputdata;
+  l = pwdata->l;
+  while (ilen-- > 0)
+    {
+      c = *(unsigned char *)ibuf++;
+      if (c == '\r' || c == '\n')
+	{
+	  char *buf = NULL;
+	  up = D_user->u_password;
+	  pwdata->buf[l] = 0;
+	  buf = crypt(pwdata->buf, up);
+	  if (!buf || strncmp(buf, up, strlen(up)))
+	    {
+	      /* uh oh, user failed */
+	      bzero(pwdata->buf, sizeof(pwdata->buf));
+	      if (!buf)
+		AddStr("\r\ncrypt() failed.\r\n");
+	      else
+		AddStr("\r\nPassword incorrect.\r\n");
+	      D_processinputdata = 0;	/* otherwise freed by FreeDis */
+	      FreeDisplay();
+	      Msg(0, "Illegal reattach attempt from terminal %s.", pwdata->m.m_tty);
+	      free(pwdata);
+	      Kill(pid, SIG_BYE);
+	      return;
+	    }
+	  /* great, pw matched, all is fine */
+	  bzero(pwdata->buf, sizeof(pwdata->buf));
+	  AddStr("\r\n");
+	  D_processinputdata = 0;
+	  D_processinput = ProcessInput;
+#ifdef REMOTE_DETACH
+	  if (pwdata->m.type == MSG_DETACH
+# ifdef POW_DETACH
+	      || pwdata->m.type == MSG_POW_DETACH
+# endif
+	     )
+	    FinishDetach(&pwdata->m);
+	  else
+#endif
+	    FinishAttach(&pwdata->m);
+	  free(pwdata);
+	  return;
+	}
+      if (c == Ctrl('c'))
+	{
+	  AddStr("\r\n");
+	  FreeDisplay();
+	  Kill(pid, SIG_BYE);
+	  return;
+	}
+      if (c == '\b' || c == 0177)
+	{
+	  if (l > 0)
+	    l--;
+	  continue;
+	}
+      if (c == Ctrl('u'))
+	{
+	  l = 0;
+	  continue;
+	}
+      if (l < (int)sizeof(pwdata->buf) - 1)
+	pwdata->buf[l++] = c;
+    }
+  pwdata->l = l;
+}
+#endif
+
+/* 'end' is exclusive, i.e. you should *not* write in *end */
+static char *
+strncpy_escape_quote(dst, src, end)
+char *dst;
+const char *src, *end;
+{
+  while (*src && dst < end)
+    {
+      if (*src == '"')
+	{
+	  if (dst + 2 < end)	/* \\ \" \0 */
+	    *dst++ = '\\';
+	  else
+	    return NULL;
+	}
+      *dst++ = *src++;
+    }
+  if (dst >= end)
+    return NULL;
+
+  *dst = '\0';
+  return dst;
+}
+
+static void
+DoCommandMsg(mp)
+struct msg *mp;
+{
+  char *args[MAXARGS];
+  int argl[MAXARGS];
+  char fullcmd[MAXSTR];
+  register char *fc;
+  int n;
+  register char *p = mp->m.command.cmd;
+  struct acluser *user;
+#ifdef MULTIUSER
+  extern struct acluser *EffectiveAclUser;	/* acls.c */
+#else
+  extern struct acluser *users;			/* acls.c */
+#endif
+
+  n = mp->m.command.nargs;
+  if (n > MAXARGS - 1)
+    n = MAXARGS - 1;
+  for (fc = fullcmd; n > 0; n--)
+    {
+      int len = strlen(p);
+      *fc++ = '"';
+      if (!(fc = strncpy_escape_quote(fc, p, fullcmd + sizeof(fullcmd) - 2)))	/* '"' ' ' */
+	{
+	  Msg(0, "Remote command too long.");
+	  queryflag = -1;
+	  return;
+	}
+      p += len + 1;
+      *fc++ = '"';
+      *fc++ = ' ';
+    }
+  if (fc != fullcmd)
+    *--fc = 0;
+  if (Parse(fullcmd, sizeof fullcmd, args, argl) <= 0)
+    {
+      queryflag = -1;
+      return;
+    }
+#ifdef MULTIUSER
+  user = *FindUserPtr(mp->m.attach.auser);
+  if (user == 0)
+    {
+      Msg(0, "Unknown user %s tried to send a command!", mp->m.attach.auser);
+      queryflag = -1;
+      return;
+    }
+#else
+  user = users;
+#endif
+#ifdef PASSWORD
+  if (user->u_password && *user->u_password)
+    {
+      Msg(0, "User %s has a password, cannot use remote commands (using -Q or -X option).", mp->m.attach.auser);
+      queryflag = -1;
+      return;
+    }
+#endif
+  if (!display)
+    for (display = displays; display; display = display->d_next)
+      if (D_user == user)
+	break;
+  for (fore = windows; fore; fore = fore->w_next)
+    if (!TTYCMP(mp->m_tty, fore->w_tty))
+      {
+	if (!display)
+	  display = fore->w_layer.l_cvlist ? fore->w_layer.l_cvlist->c_display : 0;
+
+	/* If the window is not visibile in any display, then do not use the originating window as
+	 * the foreground window for the command. This way, if there is an existing display, then
+	 * the command will execute from the foreground window of that display. This is necessary so
+	 * that commands that are relative to the window (e.g. 'next' etc.) do the right thing. */
+	if (!fore->w_layer.l_cvlist || !fore->w_layer.l_cvlist->c_display)
+	  fore = NULL;
+	break;
+      }
+  if (!display)
+    display = displays;		/* sigh */
+  if (*mp->m.command.preselect)
+    {
+      int i = -1;
+      if (strcmp(mp->m.command.preselect, "-"))
+	{
+	  i = WindowByNoN(mp->m.command.preselect);
+	  if (i < 0 || !wtab[i])
+	    {
+	      Msg(0, "Could not find pre-select window.");
+	      queryflag = -1;
+	      return;
+	    }
+	}
+      fore = i >= 0 ? wtab[i] : 0;
+    }
+  else if (!fore)
+    {
+      if (display && D_user == user)
+	fore = Layer2Window(display->d_forecv->c_layer);
+      if (!fore)
+	{
+	  fore = user->u_detachwin >= 0 ? wtab[user->u_detachwin] : 0;
+	  fore = FindNiceWindow(fore, 0);
+	}
+    }
+  if (!fore)
+    fore = windows;		/* sigh */
+#ifdef MULTIUSER
+  EffectiveAclUser = user;
+#endif
+  if (*args)
+    {
+      char *oldrcname = rc_name;
+      rc_name = "-X";
+      debug3("Running command on display %x window %x (%d)\n", display, fore, fore ? fore->w_number : -1);
+      flayer = fore ? &fore->w_layer : 0;
+      if (fore && fore->w_savelayer && (fore->w_blocked || fore->w_savelayer->l_cvlist == 0))
+	flayer = fore->w_savelayer;
+      DoCommand(args, argl);
+      rc_name = oldrcname;
+    }
+#ifdef MULTIUSER
+  EffectiveAclUser = 0;
+#endif
+}
+
+int
+SendAttachMsg(s, m, fd)
+int s;
+struct msg *m;
+int fd;
+{
+  int r;
+  struct msghdr msg;
+  struct iovec iov;
+  char buf[CMSG_SPACE(sizeof(int))];
+  struct cmsghdr *cmsg;
+
+  iov.iov_base = (char *)m;
+  iov.iov_len = sizeof(*m);
+  bzero(&msg, sizeof(msg));
+  msg.msg_name = 0;
+  msg.msg_namelen = 0;
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+  msg.msg_control = buf;
+  msg.msg_controllen = sizeof(buf);
+  cmsg = CMSG_FIRSTHDR(&msg);
+  cmsg->cmsg_level = SOL_SOCKET;
+  cmsg->cmsg_type = SCM_RIGHTS;
+  cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+  bcopy(&fd, CMSG_DATA(cmsg), sizeof(int));
+  msg.msg_controllen = cmsg->cmsg_len;
+  while(1)
+    {
+      r = sendmsg(s, &msg, 0);
+      if (r == -1 && errno == EINTR)
+	continue;
+      if (r == -1)
+	return -1;
+      return 0;
+    }
+}
+
+bool
+IsSocket(path)
+const char *path;
+{
+  struct stat st;
+
+  if (stat(path, &st) < 0)
+    return false;
+
+  return S_ISSOCK(st.st_mode);
+}