rxvt-unicode/src/ptytty.C

// This file is part of libptytty. Do not make local modifications.
// http://software.schmorp.de/pkg/libptytty

/*----------------------------------------------------------------------*
 * File:        ptytty.C
 *----------------------------------------------------------------------*
 *
 * All portions of code are copyright by their respective author/s.
 * Copyright (c) 1999-2001 Geoff Wing <gcw@pobox.com>
 * Copyright (c) 2004-2006 Marc Lehmann <pcg@goof.com>
 * Copyright (c) 2006      Emanuele Giaquinta <e.giaquinta@glauco.it>
 *
 * 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 2 of the License, 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; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *---------------------------------------------------------------------*/

#include "../config.h"

#include "ptytty.h"

#include <cstdlib>
#include <cstring>
#include <csignal>

#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <fcntl.h>

#ifdef HAVE_SYS_IOCTL_H
# include <sys/ioctl.h>
#endif
#if defined(HAVE_DEV_PTMX) && defined(HAVE_SYS_STROPTS_H)
# include <sys/stropts.h>      /* for I_PUSH */
#endif
#ifdef HAVE_ISASTREAM
# include <stropts.h>
#endif
#if defined(HAVE_PTY_H)
# include <pty.h>
#elif defined(HAVE_LIBUTIL_H)
# include <libutil.h>
#elif defined(HAVE_UTIL_H)
# include <util.h>
#endif
#ifdef TTY_GID_SUPPORT
#include <grp.h>
#endif

#include <cstdio>

/////////////////////////////////////////////////////////////////////////////

/* ------------------------------------------------------------------------- *
 *                  GET PSEUDO TELETYPE - MASTER AND SLAVE                   *
 * ------------------------------------------------------------------------- */
/*
 * Returns pty file descriptor, or -1 on failure 
 * If successful, ttydev is set to the name of the slave device.
 * fd_tty _may_ also be set to an open fd to the slave device
 */
#if defined(UNIX98_PTY)
static int
get_pty (int *fd_tty, char **ttydev)
{
  int pfd;

# if defined(HAVE_GETPT)
  pfd = getpt();
# elif defined(HAVE_POSIX_OPENPT)
  pfd = posix_openpt (O_RDWR);
# else
  pfd = open (CLONE_DEVICE, O_RDWR | O_NOCTTY, 0);
# endif
  if (pfd >= 0)
    {
      if (grantpt (pfd) == 0    /* change slave permissions */
          && unlockpt (pfd) == 0)
        {       /* slave now unlocked */
          *ttydev = strdup (ptsname (pfd));     /* get slave's name */
          return pfd;
        }

      close (pfd);
    }

  return -1;
}
#elif defined(HAVE_OPENPTY)
static int
get_pty (int *fd_tty, char **ttydev)
{
  int pfd;
  int res;
  char tty_name[32];
  
  res = openpty (&pfd, fd_tty, tty_name, NULL, NULL);
  if (res != -1)
    {
      *ttydev = strdup (tty_name);
      return pfd;
    }

  return -1;
}
#elif defined(HAVE__GETPTY)
static int
get_pty (int *fd_tty, char **ttydev)
{
  int pfd;

  *ttydev = _getpty (&pfd, O_RDWR | O_NONBLOCK | O_NOCTTY, 0622, 0);
  if (*ttydev != NULL)
    return pfd;

  return -1;
}
#elif defined(HAVE_DEV_PTC)
static int
get_pty (int *fd_tty, char **ttydev)
{
  int pfd;

  if ((pfd = open ("/dev/ptc", O_RDWR | O_NOCTTY, 0)) >= 0)
    {
      *ttydev = strdup (ttyname (pfd));
      return pfd;
    }

  return -1;
}
#elif defined(HAVE_DEV_CLONE)
static int
get_pty (int *fd_tty, char **ttydev)
{
  int pfd;

  if ((pfd = open ("/dev/ptym/clone", O_RDWR | O_NOCTTY, 0)) >= 0)
    {
      *ttydev = strdup (ptsname (pfd));
      return pfd;
    }

  return -1;
}
#else
/* Based on the code in openssh/openbsd-compat/bsd-openpty.c */
static int
get_pty (int *fd_tty, char **ttydev)
{
  int pfd;
  int i;
  char pty_name[32];
  char tty_name[32];
  const char *majors = "pqrstuvwxyzabcde";
  const char *minors = "0123456789abcdef";
  for (i = 0; i < 256; i++)
    {
      snprintf(pty_name, 32, "/dev/pty%c%c", majors[i / 16], minors[i % 16]);
      snprintf(tty_name, 32, "/dev/tty%c%c", majors[i / 16], minors[i % 16]);
      if ((pfd = open (pty_name, O_RDWR | O_NOCTTY, 0)) == -1)
        {
          snprintf(pty_name, 32, "/dev/ptyp%d", i);
          snprintf(tty_name, 32, "/dev/ttyp%d", i);
          if ((pfd = open (pty_name, O_RDWR | O_NOCTTY, 0)) == -1)
            continue;
        }
      if (access (tty_name, R_OK | W_OK) == 0)
        {
          *ttydev = strdup (tty_name);
          return pfd;
        }

      close (pfd);
    }
}
#endif

/*----------------------------------------------------------------------*/
/*
 * Returns tty file descriptor, or -1 on failure 
 */
static int
get_tty (char *ttydev)
{
  return open (ttydev, O_RDWR | O_NOCTTY, 0);
}

/*----------------------------------------------------------------------*/
/*
 * Make our tty a controlling tty so that /dev/tty points to us
 */
static int
control_tty (int fd_tty)
{
  setsid ();

#if defined(HAVE_DEV_PTMX) && defined(I_PUSH)
  /*
   * Push STREAMS modules:
   *    ptem: pseudo-terminal hardware emulation module.
   *    ldterm: standard terminal line discipline.
   *    ttcompat: V7, 4BSD and XENIX STREAMS compatibility module.
   *
   * After we push the STREAMS modules, the first open () on the slave side
   * (i.e. the next section between the dashes giving us "tty opened OK")
   * should make the "ptem" (or "ldterm" depending upon either which OS
   * version or which set of manual pages you have) module give us a
   * controlling terminal.  We must already have close ()d the master side
   * fd in this child process before we push STREAMS modules on because the
   * documentation is really unclear about whether it is any close () on
   * the master side or the last close () - i.e. a proper STREAMS dismantling
   * close () - on the master side which causes a hang up to be sent
   * through - Geoff Wing
   */
# ifdef HAVE_ISASTREAM
  if (isastream (fd_tty) == 1)
# endif
    {
      ioctl (fd_tty, I_PUSH, "ptem");
      ioctl (fd_tty, I_PUSH, "ldterm");
      ioctl (fd_tty, I_PUSH, "ttcompat");
    }
#endif

  ioctl (fd_tty, TIOCSCTTY, NULL);

  int fd = open ("/dev/tty", O_WRONLY);
  if (fd < 0)
    return -1; /* fatal */

  close (fd);

  return 0;
}

void
ptytty::close_tty ()
{
  if (tty < 0)
    return;

  close (tty);
  tty = -1;
}

bool
ptytty::make_controlling_tty ()
{
  return control_tty (tty) >= 0;
}

void
ptytty::set_utf8_mode (bool on)
{
#ifdef IUTF8
  if (pty < 0)
    return;

  struct termios tio;

  if (tcgetattr (pty, &tio) != -1)
    {
      tcflag_t new_cflag = tio.c_iflag;

      if (on)
        new_cflag |= IUTF8;
      else
        new_cflag &= ~IUTF8;

      if (new_cflag != tio.c_iflag)
        {
          tio.c_iflag = new_cflag;
          tcsetattr (pty, TCSANOW, &tio);
        }
    }
#endif
}

static struct ttyconf {
  gid_t gid;
  mode_t mode;

  ttyconf ()
    {
#ifdef TTY_GID_SUPPORT
      struct group *gr = getgrnam ("tty");

      if (gr)
        {           /* change group ownership of tty to "tty" */
          mode = S_IRUSR | S_IWUSR | S_IWGRP;
          gid = gr->gr_gid;
        }
      else
#endif                          /* TTY_GID_SUPPORT */
        {
          mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
          gid = 0;
        }
    }
} ttyconf;

ptytty_unix::ptytty_unix ()
{
  name = 0;
#if UTMP_SUPPORT
  cmd_pid = 0;
#endif
}

ptytty_unix::~ptytty_unix ()
{
#if UTMP_SUPPORT
  logout ();
#endif
  put ();
}

void
ptytty_unix::put ()
{
  chmod (name, RESTORE_TTY_MODE);
  chown (name, 0, ttyconf.gid);

  close_tty ();

  if (pty >= 0)
    close (pty);

  free (name);

  pty = tty = -1;
  name = 0;
}

bool
ptytty_unix::get ()
{
  /* get master (pty) */
  if ((pty = get_pty (&tty, &name)) < 0)
    return false;

  fcntl (pty, F_SETFL, O_NONBLOCK);

  /* get slave (tty) */
  if (tty < 0)
    {
#ifndef NO_SETOWNER_TTYDEV
      chown (name, getuid (), ttyconf.gid);      /* fail silently */
      chmod (name, ttyconf.mode);
# ifdef HAVE_REVOKE
      revoke (name);
# endif
#endif

      if ((tty = get_tty (name)) < 0)
        {
          put ();
          return false;
        }
    }

  return true;
}

/////////////////////////////////////////////////////////////////////////////
// helper/proxy support

#if PTYTTY_HELPER

static int sock_fd = -1, lock_fd = -1;
static int helper_pid, owner_pid;

struct command
{
  enum { get, login, destroy } type;

  ptytty *id;

  bool login_shell;
  int cmd_pid;
  char hostname[512]; // arbitrary, but should be plenty
};

struct ptytty_proxy : ptytty
{
  ptytty *id;

  ptytty_proxy ()
  : id(0)
  {
  }

  ~ptytty_proxy ();

  bool get ();
  void login (int cmd_pid, bool login_shell, const char *hostname);
};

#if PTYTTY_REENTRANT
# define NEED_TOKEN do { char ch; read  (lock_fd, &ch, 1); } while (0)
# define GIVE_TOKEN do { char ch; write (lock_fd, &ch, 1); } while (0)
#else
# define NEED_TOKEN (void)0
# define GIVE_TOKEN (void)0
#endif

bool
ptytty_proxy::get ()
{
  NEED_TOKEN;

  command cmd;

  cmd.type = command::get;

  write (sock_fd, &cmd, sizeof (cmd));

  if (read (sock_fd, &id, sizeof (id)) != sizeof (id))
    ptytty_fatal ("protocol error while creating pty using helper process, aborting.\n");

  if (!id)
    {
      GIVE_TOKEN;
      return false;
    }

  if ((pty = recv_fd (sock_fd)) < 0
      || (tty = recv_fd (sock_fd)) < 0)
    ptytty_fatal ("protocol error while reading pty/tty fds from helper process, aborting.\n");

  GIVE_TOKEN;
  return true;
}

void
ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname)
{
  NEED_TOKEN;

  command cmd;

  cmd.type = command::login;
  cmd.id = id;
  cmd.cmd_pid = cmd_pid;
  cmd.login_shell = login_shell;
  strncpy (cmd.hostname, hostname, sizeof (cmd.hostname));

  write (sock_fd, &cmd, sizeof (cmd));

  GIVE_TOKEN;
}

ptytty_proxy::~ptytty_proxy ()
{
  if (id)
    {
      NEED_TOKEN;

      command cmd;

      cmd.type = command::destroy;
      cmd.id = id;

      write (sock_fd, &cmd, sizeof (cmd));

      GIVE_TOKEN;
    }
}

static
void serve ()
{
  command cmd;
  vector<ptytty *> ptys;

  for (;;)
    {
      GIVE_TOKEN;

      if (read (sock_fd, &cmd, sizeof (command)) != sizeof (command))
        break;

      if (cmd.type == command::get)
        {
          // -> id ptyfd ttyfd
          cmd.id = new ptytty_unix;

          if (cmd.id->get ())
            {
              write (sock_fd, &cmd.id, sizeof (cmd.id));
              ptys.push_back (cmd.id);

              ptytty::send_fd (sock_fd, cmd.id->pty);
              ptytty::send_fd (sock_fd, cmd.id->tty);
            }
          else
            {
              delete cmd.id;
              cmd.id = 0;
              write (sock_fd, &cmd.id, sizeof (cmd.id));
            }
        }
      else if (cmd.type == command::login)
        {
#if UTMP_SUPPORT
          if (find (ptys.begin (), ptys.end (), cmd.id) != ptys.end ())
            {
              cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
              cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
            }
#endif
        }
      else if (cmd.type == command::destroy)
        {
          vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);

          if (pty != ptys.end ())
            {
              delete *pty;
              ptys.erase (pty);
            }
        }
      else
        break;

      NEED_TOKEN;
    }

  // destroy all ptys
  for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
    delete *i;
}

void
ptytty::use_helper ()
{
#ifndef PTYTTY_NO_PID_CHECK
  int pid = getpid ();
#endif

  if (sock_fd >= 0
#ifndef PTYTTY_NO_PID_CHECK
      && pid == owner_pid
#endif
      )
    return;

#ifndef PTYTTY_NO_PID_CHECK
  owner_pid = pid;
#endif

  int sv[2];

  if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
    ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");

#ifdef PTYTTY_REENTRANT
  int lv[2];

  if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
    ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
#endif

  helper_pid = fork ();

  if (helper_pid < 0)
    ptytty_fatal ("could not create pty/sessiondb helper process, aborting.\n");

  if (helper_pid)
    {
      // client, process
      sock_fd = sv[0];
      close (sv[1]);
      fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
#ifdef PTYTTY_REENTRANT
      lock_fd = lv[0];
      close (lv[1]);
      fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
#endif
    }
  else
    {
      // server, pty-helper
      sock_fd = sv[1];
#ifdef PTYTTY_REENTRANT
      lock_fd = lv[1];
#endif

      chdir ("/");

      signal (SIGHUP,  SIG_IGN);
      signal (SIGTERM, SIG_IGN);
      signal (SIGINT,  SIG_IGN);
      signal (SIGPIPE, SIG_IGN);

      for (int fd = 0; fd < 1023; fd++)
        if (fd != sock_fd && fd != lock_fd)
          close (fd);

      serve ();
      _exit (EXIT_SUCCESS);
    }
}

#endif

ptytty *
ptytty::create ()
{
#if PTYTTY_HELPER
  if (helper_pid
# ifndef PTYTTY_NO_PID_CHECK
      && getpid () == owner_pid
# endif
      )
    // use helper process
    return new ptytty_proxy;
  else
#endif
    return new ptytty_unix;
}

void
ptytty::init ()
{
  uid_t uid = getuid ();
  gid_t gid = getgid ();
      
  // before doing anything else, check for setuid/setgid operation,
  // start the helper process and drop privileges
  if (uid != geteuid ()
      || gid != getegid ())
    {
#if PTYTTY_HELPER
      use_helper ();
#else
      ptytty_warn ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n");
#endif

      drop_privileges ();
    }
}

void
ptytty::drop_privileges ()
{
  uid_t uid = getuid ();
  gid_t gid = getgid ();

  // drop privileges
#if HAVE_SETRESUID
  setresgid (gid, gid, gid);
  setresuid (uid, uid, uid);
#elif HAVE_SETREUID
  setregid (gid, gid);
  setreuid (uid, uid);
#elif HAVE_SETUID
  setgid (gid);
  setuid (uid);
#endif

  if (uid != geteuid ()
      || gid != getegid ())
    ptytty_fatal ("unable to drop privileges, aborting.\n");
}

/////////////////////////////////////////////////////////////////////////////
// C API

#ifndef PTYTTY_NO_C_API

#define DEFINE_METHOD(retval, name, args1, args2) \
extern "C" retval ptytty_ ## name args1           \
{ return ((struct ptytty *)ptytty)->name args2; }

DEFINE_METHOD(int,pty,(void *ptytty),)
DEFINE_METHOD(int,tty,(void *ptytty),)
DEFINE_METHOD(int,get,(void *ptytty),())
DEFINE_METHOD(void,login,(void *ptytty, int cmd_pid, bool login_shell, const char *hostname),(cmd_pid,login_shell,hostname))

DEFINE_METHOD(void,close_tty,(void *ptytty),())
DEFINE_METHOD(int,make_controlling_tty,(void *ptytty),())
DEFINE_METHOD(void,set_utf8_mode,(void *ptytty, int on),(on))

#define DEFINE_STATIC(retval, name, args) \
extern "C" retval ptytty_ ## name args           \
{ return ptytty::name args; }

DEFINE_STATIC(void,drop_privileges,())
DEFINE_STATIC(void,use_helper,())
DEFINE_STATIC(void,init,())

DEFINE_STATIC(void *,create,())

void ptytty_delete (void *ptytty)
{
  delete (struct ptytty *)ptytty;
}

// send_fd, recv_fd not exposed

#endif
Revision:	1.59
Committed:	Mon Jan 23 12:05:12 2006 UTC (18 years, 4 months ago) by root
Content type:	text/plain
Branch:	MAIN
Changes since 1.58:	+108 -7 lines
Log Message:	* empty log message *
#	Content
1	// This file is part of libptytty. Do not make local modifications.
2	// http://software.schmorp.de/pkg/libptytty
3
4	/----------------------------------------------------------------------
5	* File: ptytty.C
6	----------------------------------------------------------------------
7	*
8	* All portions of code are copyright by their respective author/s.
9	* Copyright (c) 1999-2001 Geoff Wing <gcw@pobox.com>
10	* Copyright (c) 2004-2006 Marc Lehmann <pcg@goof.com>
11	* Copyright (c) 2006 Emanuele Giaquinta <e.giaquinta@glauco.it>
12	*
13	* This program is free software; you can redistribute it and/or modify
14	* it under the terms of the GNU General Public License as published by
15	* the Free Software Foundation; either version 2 of the License, or
16	* (at your option) any later version.
17	*
18	* This program is distributed in the hope that it will be useful,
19	* but WITHOUT ANY WARRANTY; without even the implied warranty of
20	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21	* GNU General Public License for more details.
22	*
23	* You should have received a copy of the GNU General Public License
24	* along with this program; if not, write to the Free Software
25	* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
26	---------------------------------------------------------------------/
27
28	#include "../config.h"
29
30	#include "ptytty.h"
31
32	#include <cstdlib>
33	#include <cstring>
34	#include <csignal>
35
36	#include <sys/types.h>
37	#include <sys/socket.h>
38	#include <unistd.h>
39	#include <fcntl.h>
40
41	#ifdef HAVE_SYS_IOCTL_H
42	# include <sys/ioctl.h>
43	#endif
44	#if defined(HAVE_DEV_PTMX) && defined(HAVE_SYS_STROPTS_H)
45	# include <sys/stropts.h> /* for I_PUSH */
46	#endif
47	#ifdef HAVE_ISASTREAM
48	# include <stropts.h>
49	#endif
50	#if defined(HAVE_PTY_H)
51	# include <pty.h>
52	#elif defined(HAVE_LIBUTIL_H)
53	# include <libutil.h>
54	#elif defined(HAVE_UTIL_H)
55	# include <util.h>
56	#endif
57	#ifdef TTY_GID_SUPPORT
58	#include <grp.h>
59	#endif
60
61	#include <cstdio>
62
63	/////////////////////////////////////////////////////////////////////////////
64
65	/* ------------------------------------------------------------------------- *
66	* GET PSEUDO TELETYPE - MASTER AND SLAVE *
67	* ------------------------------------------------------------------------- */
68	/*
69	* Returns pty file descriptor, or -1 on failure
70	* If successful, ttydev is set to the name of the slave device.
71	* fd_tty _may_ also be set to an open fd to the slave device
72	*/
73	#if defined(UNIX98_PTY)
74	static int
75	get_pty (int fd_tty, char *ttydev)
76	{
77	int pfd;
78
79	# if defined(HAVE_GETPT)
80	pfd = getpt();
81	# elif defined(HAVE_POSIX_OPENPT)
82	pfd = posix_openpt (O_RDWR);
83	# else
84	pfd = open (CLONE_DEVICE, O_RDWR \| O_NOCTTY, 0);
85	# endif
86	if (pfd >= 0)
87	{
88	if (grantpt (pfd) == 0 /* change slave permissions */
89	&& unlockpt (pfd) == 0)
90	{ /* slave now unlocked */
91	ttydev = strdup (ptsname (pfd)); / get slave's name */
92	return pfd;
93	}
94
95	close (pfd);
96	}
97
98	return -1;
99	}
100	#elif defined(HAVE_OPENPTY)
101	static int
102	get_pty (int fd_tty, char *ttydev)
103	{
104	int pfd;
105	int res;
106	char tty_name[32];
107
108	res = openpty (&pfd, fd_tty, tty_name, NULL, NULL);
109	if (res != -1)
110	{
111	*ttydev = strdup (tty_name);
112	return pfd;
113	}
114
115	return -1;
116	}
117	#elif defined(HAVE__GETPTY)
118	static int
119	get_pty (int fd_tty, char *ttydev)
120	{
121	int pfd;
122
123	*ttydev = _getpty (&pfd, O_RDWR \| O_NONBLOCK \| O_NOCTTY, 0622, 0);
124	if (*ttydev != NULL)
125	return pfd;
126
127	return -1;
128	}
129	#elif defined(HAVE_DEV_PTC)
130	static int
131	get_pty (int fd_tty, char *ttydev)
132	{
133	int pfd;
134
135	if ((pfd = open ("/dev/ptc", O_RDWR \| O_NOCTTY, 0)) >= 0)
136	{
137	*ttydev = strdup (ttyname (pfd));
138	return pfd;
139	}
140
141	return -1;
142	}
143	#elif defined(HAVE_DEV_CLONE)
144	static int
145	get_pty (int fd_tty, char *ttydev)
146	{
147	int pfd;
148
149	if ((pfd = open ("/dev/ptym/clone", O_RDWR \| O_NOCTTY, 0)) >= 0)
150	{
151	*ttydev = strdup (ptsname (pfd));
152	return pfd;
153	}
154
155	return -1;
156	}
157	#else
158	/* Based on the code in openssh/openbsd-compat/bsd-openpty.c */
159	static int
160	get_pty (int fd_tty, char *ttydev)
161	{
162	int pfd;
163	int i;
164	char pty_name[32];
165	char tty_name[32];
166	const char *majors = "pqrstuvwxyzabcde";
167	const char *minors = "0123456789abcdef";
168	for (i = 0; i < 256; i++)
169	{
170	snprintf(pty_name, 32, "/dev/pty%c%c", majors[i / 16], minors[i % 16]);
171	snprintf(tty_name, 32, "/dev/tty%c%c", majors[i / 16], minors[i % 16]);
172	if ((pfd = open (pty_name, O_RDWR \| O_NOCTTY, 0)) == -1)
173	{
174	snprintf(pty_name, 32, "/dev/ptyp%d", i);
175	snprintf(tty_name, 32, "/dev/ttyp%d", i);
176	if ((pfd = open (pty_name, O_RDWR \| O_NOCTTY, 0)) == -1)
177	continue;
178	}
179	if (access (tty_name, R_OK \| W_OK) == 0)
180	{
181	*ttydev = strdup (tty_name);
182	return pfd;
183	}
184
185	close (pfd);
186	}
187	}
188	#endif
189
190	/----------------------------------------------------------------------/
191	/*
192	* Returns tty file descriptor, or -1 on failure
193	*/
194	static int
195	get_tty (char *ttydev)
196	{
197	return open (ttydev, O_RDWR \| O_NOCTTY, 0);
198	}
199
200	/----------------------------------------------------------------------/
201	/*
202	* Make our tty a controlling tty so that /dev/tty points to us
203	*/
204	static int
205	control_tty (int fd_tty)
206	{
207	setsid ();
208
209	#if defined(HAVE_DEV_PTMX) && defined(I_PUSH)
210	/*
211	* Push STREAMS modules:
212	* ptem: pseudo-terminal hardware emulation module.
213	* ldterm: standard terminal line discipline.
214	* ttcompat: V7, 4BSD and XENIX STREAMS compatibility module.
215	*
216	* After we push the STREAMS modules, the first open () on the slave side
217	* (i.e. the next section between the dashes giving us "tty opened OK")
218	* should make the "ptem" (or "ldterm" depending upon either which OS
219	* version or which set of manual pages you have) module give us a
220	* controlling terminal. We must already have close ()d the master side
221	* fd in this child process before we push STREAMS modules on because the
222	* documentation is really unclear about whether it is any close () on
223	* the master side or the last close () - i.e. a proper STREAMS dismantling
224	* close () - on the master side which causes a hang up to be sent
225	* through - Geoff Wing
226	*/
227	# ifdef HAVE_ISASTREAM
228	if (isastream (fd_tty) == 1)
229	# endif
230	{
231	ioctl (fd_tty, I_PUSH, "ptem");
232	ioctl (fd_tty, I_PUSH, "ldterm");
233	ioctl (fd_tty, I_PUSH, "ttcompat");
234	}
235	#endif
236
237	ioctl (fd_tty, TIOCSCTTY, NULL);
238
239	int fd = open ("/dev/tty", O_WRONLY);
240	if (fd < 0)
241	return -1; /* fatal */
242
243	close (fd);
244
245	return 0;
246	}
247
248	void
249	ptytty::close_tty ()
250	{
251	if (tty < 0)
252	return;
253
254	close (tty);
255	tty = -1;
256	}
257
258	bool
259	ptytty::make_controlling_tty ()
260	{
261	return control_tty (tty) >= 0;
262	}
263
264	void
265	ptytty::set_utf8_mode (bool on)
266	{
267	#ifdef IUTF8
268	if (pty < 0)
269	return;
270
271	struct termios tio;
272
273	if (tcgetattr (pty, &tio) != -1)
274	{
275	tcflag_t new_cflag = tio.c_iflag;
276
277	if (on)
278	new_cflag \|= IUTF8;
279	else
280	new_cflag &= ~IUTF8;
281
282	if (new_cflag != tio.c_iflag)
283	{
284	tio.c_iflag = new_cflag;
285	tcsetattr (pty, TCSANOW, &tio);
286	}
287	}
288	#endif
289	}
290
291	static struct ttyconf {
292	gid_t gid;
293	mode_t mode;
294
295	ttyconf ()
296	{
297	#ifdef TTY_GID_SUPPORT
298	struct group *gr = getgrnam ("tty");
299
300	if (gr)
301	{ /* change group ownership of tty to "tty" */
302	mode = S_IRUSR \| S_IWUSR \| S_IWGRP;
303	gid = gr->gr_gid;
304	}
305	else
306	#endif /* TTY_GID_SUPPORT */
307	{
308	mode = S_IRUSR \| S_IWUSR \| S_IWGRP \| S_IWOTH;
309	gid = 0;
310	}
311	}
312	} ttyconf;
313
314	ptytty_unix::ptytty_unix ()
315	{
316	name = 0;
317	#if UTMP_SUPPORT
318	cmd_pid = 0;
319	#endif
320	}
321
322	ptytty_unix::~ptytty_unix ()
323	{
324	#if UTMP_SUPPORT
325	logout ();
326	#endif
327	put ();
328	}
329
330	void
331	ptytty_unix::put ()
332	{
333	chmod (name, RESTORE_TTY_MODE);
334	chown (name, 0, ttyconf.gid);
335
336	close_tty ();
337
338	if (pty >= 0)
339	close (pty);
340
341	free (name);
342
343	pty = tty = -1;
344	name = 0;
345	}
346
347	bool
348	ptytty_unix::get ()
349	{
350	/* get master (pty) */
351	if ((pty = get_pty (&tty, &name)) < 0)
352	return false;
353
354	fcntl (pty, F_SETFL, O_NONBLOCK);
355
356	/* get slave (tty) */
357	if (tty < 0)
358	{
359	#ifndef NO_SETOWNER_TTYDEV
360	chown (name, getuid (), ttyconf.gid); /* fail silently */
361	chmod (name, ttyconf.mode);
362	# ifdef HAVE_REVOKE
363	revoke (name);
364	# endif
365	#endif
366
367	if ((tty = get_tty (name)) < 0)
368	{
369	put ();
370	return false;
371	}
372	}
373
374	return true;
375	}
376
377	/////////////////////////////////////////////////////////////////////////////
378	// helper/proxy support
379
380	#if PTYTTY_HELPER
381
382	static int sock_fd = -1, lock_fd = -1;
383	static int helper_pid, owner_pid;
384
385	struct command
386	{
387	enum { get, login, destroy } type;
388
389	ptytty *id;
390
391	bool login_shell;
392	int cmd_pid;
393	char hostname[512]; // arbitrary, but should be plenty
394	};
395
396	struct ptytty_proxy : ptytty
397	{
398	ptytty *id;
399
400	ptytty_proxy ()
401	: id(0)
402	{
403	}
404
405	~ptytty_proxy ();
406
407	bool get ();
408	void login (int cmd_pid, bool login_shell, const char *hostname);
409	};
410
411	#if PTYTTY_REENTRANT
412	# define NEED_TOKEN do { char ch; read (lock_fd, &ch, 1); } while (0)
413	# define GIVE_TOKEN do { char ch; write (lock_fd, &ch, 1); } while (0)
414	#else
415	# define NEED_TOKEN (void)0
416	# define GIVE_TOKEN (void)0
417	#endif
418
419	bool
420	ptytty_proxy::get ()
421	{
422	NEED_TOKEN;
423
424	command cmd;
425
426	cmd.type = command::get;
427
428	write (sock_fd, &cmd, sizeof (cmd));
429
430	if (read (sock_fd, &id, sizeof (id)) != sizeof (id))
431	ptytty_fatal ("protocol error while creating pty using helper process, aborting.\n");
432
433	if (!id)
434	{
435	GIVE_TOKEN;
436	return false;
437	}
438
439	if ((pty = recv_fd (sock_fd)) < 0
440	\|\| (tty = recv_fd (sock_fd)) < 0)
441	ptytty_fatal ("protocol error while reading pty/tty fds from helper process, aborting.\n");
442
443	GIVE_TOKEN;
444	return true;
445	}
446
447	void
448	ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname)
449	{
450	NEED_TOKEN;
451
452	command cmd;
453
454	cmd.type = command::login;
455	cmd.id = id;
456	cmd.cmd_pid = cmd_pid;
457	cmd.login_shell = login_shell;
458	strncpy (cmd.hostname, hostname, sizeof (cmd.hostname));
459
460	write (sock_fd, &cmd, sizeof (cmd));
461
462	GIVE_TOKEN;
463	}
464
465	ptytty_proxy::~ptytty_proxy ()
466	{
467	if (id)
468	{
469	NEED_TOKEN;
470
471	command cmd;
472
473	cmd.type = command::destroy;
474	cmd.id = id;
475
476	write (sock_fd, &cmd, sizeof (cmd));
477
478	GIVE_TOKEN;
479	}
480	}
481
482	static
483	void serve ()
484	{
485	command cmd;
486	vector<ptytty *> ptys;
487
488	for (;;)
489	{
490	GIVE_TOKEN;
491
492	if (read (sock_fd, &cmd, sizeof (command)) != sizeof (command))
493	break;
494
495	if (cmd.type == command::get)
496	{
497	// -> id ptyfd ttyfd
498	cmd.id = new ptytty_unix;
499
500	if (cmd.id->get ())
501	{
502	write (sock_fd, &cmd.id, sizeof (cmd.id));
503	ptys.push_back (cmd.id);
504
505	ptytty::send_fd (sock_fd, cmd.id->pty);
506	ptytty::send_fd (sock_fd, cmd.id->tty);
507	}
508	else
509	{
510	delete cmd.id;
511	cmd.id = 0;
512	write (sock_fd, &cmd.id, sizeof (cmd.id));
513	}
514	}
515	else if (cmd.type == command::login)
516	{
517	#if UTMP_SUPPORT
518	if (find (ptys.begin (), ptys.end (), cmd.id) != ptys.end ())
519	{
520	cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
521	cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
522	}
523	#endif
524	}
525	else if (cmd.type == command::destroy)
526	{
527	vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);
528
529	if (pty != ptys.end ())
530	{
531	delete *pty;
532	ptys.erase (pty);
533	}
534	}
535	else
536	break;
537
538	NEED_TOKEN;
539	}
540
541	// destroy all ptys
542	for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
543	delete *i;
544	}
545
546	void
547	ptytty::use_helper ()
548	{
549	#ifndef PTYTTY_NO_PID_CHECK
550	int pid = getpid ();
551	#endif
552
553	if (sock_fd >= 0
554	#ifndef PTYTTY_NO_PID_CHECK
555	&& pid == owner_pid
556	#endif
557	)
558	return;
559
560	#ifndef PTYTTY_NO_PID_CHECK
561	owner_pid = pid;
562	#endif
563
564	int sv[2];
565
566	if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
567	ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
568
569	#ifdef PTYTTY_REENTRANT
570	int lv[2];
571
572	if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
573	ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
574	#endif
575
576	helper_pid = fork ();
577
578	if (helper_pid < 0)
579	ptytty_fatal ("could not create pty/sessiondb helper process, aborting.\n");
580
581	if (helper_pid)
582	{
583	// client, process
584	sock_fd = sv[0];
585	close (sv[1]);
586	fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
587	#ifdef PTYTTY_REENTRANT
588	lock_fd = lv[0];
589	close (lv[1]);
590	fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
591	#endif
592	}
593	else
594	{
595	// server, pty-helper
596	sock_fd = sv[1];
597	#ifdef PTYTTY_REENTRANT
598	lock_fd = lv[1];
599	#endif
600
601	chdir ("/");
602
603	signal (SIGHUP, SIG_IGN);
604	signal (SIGTERM, SIG_IGN);
605	signal (SIGINT, SIG_IGN);
606	signal (SIGPIPE, SIG_IGN);
607
608	for (int fd = 0; fd < 1023; fd++)
609	if (fd != sock_fd && fd != lock_fd)
610	close (fd);
611
612	serve ();
613	_exit (EXIT_SUCCESS);
614	}
615	}
616
617	#endif
618
619	ptytty *
620	ptytty::create ()
621	{
622	#if PTYTTY_HELPER
623	if (helper_pid
624	# ifndef PTYTTY_NO_PID_CHECK
625	&& getpid () == owner_pid
626	# endif
627	)
628	// use helper process
629	return new ptytty_proxy;
630	else
631	#endif
632	return new ptytty_unix;
633	}
634
635	void
636	ptytty::init ()
637	{
638	uid_t uid = getuid ();
639	gid_t gid = getgid ();
640
641	// before doing anything else, check for setuid/setgid operation,
642	// start the helper process and drop privileges
643	if (uid != geteuid ()
644	\|\| gid != getegid ())
645	{
646	#if PTYTTY_HELPER
647	use_helper ();
648	#else
649	ptytty_warn ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n");
650	#endif
651
652	drop_privileges ();
653	}
654	}
655
656	void
657	ptytty::drop_privileges ()
658	{
659	uid_t uid = getuid ();
660	gid_t gid = getgid ();
661
662	// drop privileges
663	#if HAVE_SETRESUID
664	setresgid (gid, gid, gid);
665	setresuid (uid, uid, uid);
666	#elif HAVE_SETREUID
667	setregid (gid, gid);
668	setreuid (uid, uid);
669	#elif HAVE_SETUID
670	setgid (gid);
671	setuid (uid);
672	#endif
673
674	if (uid != geteuid ()
675	\|\| gid != getegid ())
676	ptytty_fatal ("unable to drop privileges, aborting.\n");
677	}
678
679	/////////////////////////////////////////////////////////////////////////////
680	// C API
681
682	#ifndef PTYTTY_NO_C_API
683
684	#define DEFINE_METHOD(retval, name, args1, args2) \
685	extern "C" retval ptytty_ ## name args1 \
686	{ return ((struct ptytty *)ptytty)->name args2; }
687
688	DEFINE_METHOD(int,pty,(void *ptytty),)
689	DEFINE_METHOD(int,tty,(void *ptytty),)
690	DEFINE_METHOD(int,get,(void *ptytty),())
691	DEFINE_METHOD(void,login,(void ptytty, int cmd_pid, bool login_shell, const char hostname),(cmd_pid,login_shell,hostname))
692
693	DEFINE_METHOD(void,close_tty,(void *ptytty),())
694	DEFINE_METHOD(int,make_controlling_tty,(void *ptytty),())
695	DEFINE_METHOD(void,set_utf8_mode,(void *ptytty, int on),(on))
696
697	#define DEFINE_STATIC(retval, name, args) \
698	extern "C" retval ptytty_ ## name args \
699	{ return ptytty::name args; }
700
701	DEFINE_STATIC(void,drop_privileges,())
702	DEFINE_STATIC(void,use_helper,())
703	DEFINE_STATIC(void,init,())
704
705	DEFINE_STATIC(void *,create,())
706
707	void ptytty_delete (void *ptytty)
708	{
709	delete (struct ptytty *)ptytty;
710	}
711
712	// send_fd, recv_fd not exposed
713
714	#endif