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>
 *
 * 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 <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;
}

#if PTYTTY_HELPER

static int sock_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);
};

bool
ptytty_proxy::get ()
{
  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)
    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");

  return true;
}

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

ptytty_proxy::~ptytty_proxy ()
{
  if (id)
    {
      command cmd;

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

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

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

  while (read (sock_fd, &cmd, sizeof (command)) == sizeof (command))
    {
      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))
            {
              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;
    }

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

void
ptytty::use_helper ()
{
  int pid = getpid ();

  if (sock_fd >= 0 && pid == owner_pid)
    return;

  owner_pid = pid;

  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");

  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);
    }
  else
    {
      // server, pty-helper
      sock_fd = sv[1];

      chdir ("/");

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

      serve ();
      _exit (EXIT_SUCCESS);
    }
}

#endif

ptytty *
ptytty::create ()
{
#if PTYTTY_HELPER
  if (helper_pid && getpid () == owner_pid)
    // 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");
}

Revision:	1.56
Committed:	Sun Jan 22 04:01:52 2006 UTC (18 years, 4 months ago) by root
Content type:	text/plain
Branch:	MAIN
Changes since 1.55:	+73 -23 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	*
12	* This program is free software; you can redistribute it and/or modify
13	* it under the terms of the GNU General Public License as published by
14	* the Free Software Foundation; either version 2 of the License, or
15	* (at your option) any later version.
16	*
17	* This program is distributed in the hope that it will be useful,
18	* but WITHOUT ANY WARRANTY; without even the implied warranty of
19	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20	* GNU General Public License for more details.
21	*
22	* You should have received a copy of the GNU General Public License
23	* along with this program; if not, write to the Free Software
24	* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
25	---------------------------------------------------------------------/
26
27	#include "../config.h"
28
29	#include "ptytty.h"
30
31	#include <cstdlib>
32	#include <cstring>
33
34	#include <sys/types.h>
35	#include <sys/socket.h>
36	#include <unistd.h>
37	#include <fcntl.h>
38
39	#ifdef HAVE_SYS_IOCTL_H
40	# include <sys/ioctl.h>
41	#endif
42	#if defined(HAVE_DEV_PTMX) && defined(HAVE_SYS_STROPTS_H)
43	# include <sys/stropts.h> /* for I_PUSH */
44	#endif
45	#ifdef HAVE_ISASTREAM
46	# include <stropts.h>
47	#endif
48	#if defined(HAVE_PTY_H)
49	# include <pty.h>
50	#elif defined(HAVE_LIBUTIL_H)
51	# include <libutil.h>
52	#elif defined(HAVE_UTIL_H)
53	# include <util.h>
54	#endif
55	#ifdef TTY_GID_SUPPORT
56	#include <grp.h>
57	#endif
58
59	#include <cstdio>
60
61	/////////////////////////////////////////////////////////////////////////////
62
63	/* ------------------------------------------------------------------------- *
64	* GET PSEUDO TELETYPE - MASTER AND SLAVE *
65	* ------------------------------------------------------------------------- */
66	/*
67	* Returns pty file descriptor, or -1 on failure
68	* If successful, ttydev is set to the name of the slave device.
69	* fd_tty _may_ also be set to an open fd to the slave device
70	*/
71	#if defined(UNIX98_PTY)
72	static int
73	get_pty (int fd_tty, char *ttydev)
74	{
75	int pfd;
76
77	# if defined(HAVE_GETPT)
78	pfd = getpt();
79	# elif defined(HAVE_POSIX_OPENPT)
80	pfd = posix_openpt (O_RDWR);
81	# else
82	pfd = open (CLONE_DEVICE, O_RDWR \| O_NOCTTY, 0);
83	# endif
84	if (pfd >= 0)
85	{
86	if (grantpt (pfd) == 0 /* change slave permissions */
87	&& unlockpt (pfd) == 0)
88	{ /* slave now unlocked */
89	ttydev = strdup (ptsname (pfd)); / get slave's name */
90	return pfd;
91	}
92
93	close (pfd);
94	}
95
96	return -1;
97	}
98	#elif defined(HAVE_OPENPTY)
99	static int
100	get_pty (int fd_tty, char *ttydev)
101	{
102	int pfd;
103	int res;
104	char tty_name[32];
105
106	res = openpty (&pfd, fd_tty, tty_name, NULL, NULL);
107	if (res != -1)
108	{
109	*ttydev = strdup (tty_name);
110	return pfd;
111	}
112
113	return -1;
114	}
115	#elif defined(HAVE__GETPTY)
116	static int
117	get_pty (int fd_tty, char *ttydev)
118	{
119	int pfd;
120
121	*ttydev = _getpty (&pfd, O_RDWR \| O_NONBLOCK \| O_NOCTTY, 0622, 0);
122	if (*ttydev != NULL)
123	return pfd;
124
125	return -1;
126	}
127	#elif defined(HAVE_DEV_PTC)
128	static int
129	get_pty (int fd_tty, char *ttydev)
130	{
131	int pfd;
132
133	if ((pfd = open ("/dev/ptc", O_RDWR \| O_NOCTTY, 0)) >= 0)
134	{
135	*ttydev = strdup (ttyname (pfd));
136	return pfd;
137	}
138
139	return -1;
140	}
141	#elif defined(HAVE_DEV_CLONE)
142	static int
143	get_pty (int fd_tty, char *ttydev)
144	{
145	int pfd;
146
147	if ((pfd = open ("/dev/ptym/clone", O_RDWR \| O_NOCTTY, 0)) >= 0)
148	{
149	*ttydev = strdup (ptsname (pfd));
150	return pfd;
151	}
152
153	return -1;
154	}
155	#else
156	/* Based on the code in openssh/openbsd-compat/bsd-openpty.c */
157	static int
158	get_pty (int fd_tty, char *ttydev)
159	{
160	int pfd;
161	int i;
162	char pty_name[32];
163	char tty_name[32];
164	const char *majors = "pqrstuvwxyzabcde";
165	const char *minors = "0123456789abcdef";
166	for (i = 0; i < 256; i++)
167	{
168	snprintf(pty_name, 32, "/dev/pty%c%c", majors[i / 16], minors[i % 16]);
169	snprintf(tty_name, 32, "/dev/tty%c%c", majors[i / 16], minors[i % 16]);
170	if ((pfd = open (pty_name, O_RDWR \| O_NOCTTY, 0)) == -1)
171	{
172	snprintf(pty_name, 32, "/dev/ptyp%d", i);
173	snprintf(tty_name, 32, "/dev/ttyp%d", i);
174	if ((pfd = open (pty_name, O_RDWR \| O_NOCTTY, 0)) == -1)
175	continue;
176	}
177	if (access (tty_name, R_OK \| W_OK) == 0)
178	{
179	*ttydev = strdup (tty_name);
180	return pfd;
181	}
182
183	close (pfd);
184	}
185	}
186	#endif
187
188	/----------------------------------------------------------------------/
189	/*
190	* Returns tty file descriptor, or -1 on failure
191	*/
192	static int
193	get_tty (char *ttydev)
194	{
195	return open (ttydev, O_RDWR \| O_NOCTTY, 0);
196	}
197
198	/----------------------------------------------------------------------/
199	/*
200	* Make our tty a controlling tty so that /dev/tty points to us
201	*/
202	static int
203	control_tty (int fd_tty)
204	{
205	setsid ();
206
207	#if defined(HAVE_DEV_PTMX) && defined(I_PUSH)
208	/*
209	* Push STREAMS modules:
210	* ptem: pseudo-terminal hardware emulation module.
211	* ldterm: standard terminal line discipline.
212	* ttcompat: V7, 4BSD and XENIX STREAMS compatibility module.
213	*
214	* After we push the STREAMS modules, the first open () on the slave side
215	* (i.e. the next section between the dashes giving us "tty opened OK")
216	* should make the "ptem" (or "ldterm" depending upon either which OS
217	* version or which set of manual pages you have) module give us a
218	* controlling terminal. We must already have close ()d the master side
219	* fd in this child process before we push STREAMS modules on because the
220	* documentation is really unclear about whether it is any close () on
221	* the master side or the last close () - i.e. a proper STREAMS dismantling
222	* close () - on the master side which causes a hang up to be sent
223	* through - Geoff Wing
224	*/
225	# ifdef HAVE_ISASTREAM
226	if (isastream (fd_tty) == 1)
227	# endif
228	{
229	ioctl (fd_tty, I_PUSH, "ptem");
230	ioctl (fd_tty, I_PUSH, "ldterm");
231	ioctl (fd_tty, I_PUSH, "ttcompat");
232	}
233	#endif
234
235	ioctl (fd_tty, TIOCSCTTY, NULL);
236
237	int fd = open ("/dev/tty", O_WRONLY);
238	if (fd < 0)
239	return -1; /* fatal */
240
241	close (fd);
242
243	return 0;
244	}
245
246	void
247	ptytty::close_tty ()
248	{
249	if (tty < 0)
250	return;
251
252	close (tty);
253	tty = -1;
254	}
255
256	bool
257	ptytty::make_controlling_tty ()
258	{
259	return control_tty (tty) >= 0;
260	}
261
262	void
263	ptytty::set_utf8_mode (bool on)
264	{
265	#ifdef IUTF8
266	if (pty < 0)
267	return;
268
269	struct termios tio;
270
271	if (tcgetattr (pty, &tio) != -1)
272	{
273	tcflag_t new_cflag = tio.c_iflag;
274
275	if (on)
276	new_cflag \|= IUTF8;
277	else
278	new_cflag &= ~IUTF8;
279
280	if (new_cflag != tio.c_iflag)
281	{
282	tio.c_iflag = new_cflag;
283	tcsetattr (pty, TCSANOW, &tio);
284	}
285	}
286	#endif
287	}
288
289	static struct ttyconf {
290	gid_t gid;
291	mode_t mode;
292
293	ttyconf ()
294	{
295	#ifdef TTY_GID_SUPPORT
296	struct group *gr = getgrnam ("tty");
297
298	if (gr)
299	{ /* change group ownership of tty to "tty" */
300	mode = S_IRUSR \| S_IWUSR \| S_IWGRP;
301	gid = gr->gr_gid;
302	}
303	else
304	#endif /* TTY_GID_SUPPORT */
305	{
306	mode = S_IRUSR \| S_IWUSR \| S_IWGRP \| S_IWOTH;
307	gid = 0;
308	}
309	}
310	} ttyconf;
311
312	ptytty_unix::ptytty_unix ()
313	{
314	name = 0;
315	#if UTMP_SUPPORT
316	cmd_pid = 0;
317	#endif
318	}
319
320	ptytty_unix::~ptytty_unix ()
321	{
322	#if UTMP_SUPPORT
323	logout ();
324	#endif
325	put ();
326	}
327
328	void
329	ptytty_unix::put ()
330	{
331	chmod (name, RESTORE_TTY_MODE);
332	chown (name, 0, ttyconf.gid);
333
334	close_tty ();
335
336	if (pty >= 0)
337	close (pty);
338
339	free (name);
340
341	pty = tty = -1;
342	name = 0;
343	}
344
345	bool
346	ptytty_unix::get ()
347	{
348	/* get master (pty) */
349	if ((pty = get_pty (&tty, &name)) < 0)
350	return false;
351
352	fcntl (pty, F_SETFL, O_NONBLOCK);
353
354	/* get slave (tty) */
355	if (tty < 0)
356	{
357	#ifndef NO_SETOWNER_TTYDEV
358	chown (name, getuid (), ttyconf.gid); /* fail silently */
359	chmod (name, ttyconf.mode);
360	# ifdef HAVE_REVOKE
361	revoke (name);
362	# endif
363	#endif
364
365	if ((tty = get_tty (name)) < 0)
366	{
367	put ();
368	return false;
369	}
370	}
371
372	return true;
373	}
374
375	#if PTYTTY_HELPER
376
377	static int sock_fd = -1;
378	static int helper_pid, owner_pid;
379
380	struct command
381	{
382	enum { get, login, destroy } type;
383
384	ptytty *id;
385
386	bool login_shell;
387	int cmd_pid;
388	char hostname[512]; // arbitrary, but should be plenty
389	};
390
391	struct ptytty_proxy : ptytty
392	{
393	ptytty *id;
394
395	ptytty_proxy ()
396	: id(0)
397	{
398	}
399
400	~ptytty_proxy ();
401
402	bool get ();
403	void login (int cmd_pid, bool login_shell, const char *hostname);
404	};
405
406	bool
407	ptytty_proxy::get ()
408	{
409	command cmd;
410
411	cmd.type = command::get;
412
413	write (sock_fd, &cmd, sizeof (cmd));
414
415	if (read (sock_fd, &id, sizeof (id)) != sizeof (id))
416	ptytty_fatal ("protocol error while creating pty using helper process, aborting.\n");
417
418	if (!id)
419	return false;
420
421	if ((pty = recv_fd (sock_fd)) < 0
422	\|\| (tty = recv_fd (sock_fd)) < 0)
423	ptytty_fatal ("protocol error while reading pty/tty fds from helper process, aborting.\n");
424
425	return true;
426	}
427
428	void
429	ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname)
430	{
431	command cmd;
432
433	cmd.type = command::login;
434	cmd.id = id;
435	cmd.cmd_pid = cmd_pid;
436	cmd.login_shell = login_shell;
437	strncpy (cmd.hostname, hostname, sizeof (cmd.hostname));
438
439	write (sock_fd, &cmd, sizeof (cmd));
440	}
441
442	ptytty_proxy::~ptytty_proxy ()
443	{
444	if (id)
445	{
446	command cmd;
447
448	cmd.type = command::destroy;
449	cmd.id = id;
450
451	write (sock_fd, &cmd, sizeof (cmd));
452	}
453	}
454
455	static
456	void serve ()
457	{
458	command cmd;
459	vector<ptytty *> ptys;
460
461	while (read (sock_fd, &cmd, sizeof (command)) == sizeof (command))
462	{
463	if (cmd.type == command::get)
464	{
465	// -> id ptyfd ttyfd
466	cmd.id = new ptytty_unix;
467
468	if (cmd.id->get ())
469	{
470	write (sock_fd, &cmd.id, sizeof (cmd.id));
471	ptys.push_back (cmd.id);
472
473	ptytty::send_fd (sock_fd, cmd.id->pty);
474	ptytty::send_fd (sock_fd, cmd.id->tty);
475	}
476	else
477	{
478	delete cmd.id;
479	cmd.id = 0;
480	write (sock_fd, &cmd.id, sizeof (cmd.id));
481	}
482	}
483	else if (cmd.type == command::login)
484	{
485	#if UTMP_SUPPORT
486	if (find (ptys.begin (), ptys.end (), cmd.id))
487	{
488	cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
489	cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
490	}
491	#endif
492	}
493	else if (cmd.type == command::destroy)
494	{
495	vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);
496
497	if (pty != ptys.end ())
498	{
499	delete *pty;
500	ptys.erase (pty);
501	}
502	}
503	else
504	break;
505	}
506
507	// destroy all ptys
508	for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
509	delete *i;
510	}
511
512	void
513	ptytty::use_helper ()
514	{
515	int pid = getpid ();
516
517	if (sock_fd >= 0 && pid == owner_pid)
518	return;
519
520	owner_pid = pid;
521
522	int sv[2];
523
524	if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
525	ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
526
527	helper_pid = fork ();
528
529	if (helper_pid < 0)
530	ptytty_fatal ("could not create pty/sessiondb helper process, aborting.\n");
531
532	if (helper_pid)
533	{
534	// client, process
535	sock_fd = sv[0];
536	close (sv[1]);
537	fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
538	}
539	else
540	{
541	// server, pty-helper
542	sock_fd = sv[1];
543
544	chdir ("/");
545
546	for (int fd = 0; fd < 1023; fd++)
547	if (fd != sock_fd)
548	close (fd);
549
550	serve ();
551	_exit (EXIT_SUCCESS);
552	}
553	}
554
555	#endif
556
557	ptytty *
558	ptytty::create ()
559	{
560	#if PTYTTY_HELPER
561	if (helper_pid && getpid () == owner_pid)
562	// use helper process
563	return new ptytty_proxy;
564	else
565	#endif
566	return new ptytty_unix;
567	}
568
569	void
570	ptytty::init ()
571	{
572	uid_t uid = getuid ();
573	gid_t gid = getgid ();
574
575	// before doing anything else, check for setuid/setgid operation,
576	// start the helper process and drop privileges
577	if (uid != geteuid ()
578	\|\| gid != getegid ())
579	{
580	#if PTYTTY_HELPER
581	use_helper ();
582	#else
583	ptytty_warn ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n");
584	#endif
585
586	drop_privileges ();
587	}
588	}
589
590	void
591	ptytty::drop_privileges ()
592	{
593	uid_t uid = getuid ();
594	gid_t gid = getgid ();
595
596	// drop privileges
597	#if HAVE_SETRESUID
598	setresgid (gid, gid, gid);
599	setresuid (uid, uid, uid);
600	#elif HAVE_SETREUID
601	setregid (gid, gid);
602	setreuid (uid, uid);
603	#elif HAVE_SETUID
604	setgid (gid);
605	setuid (uid);
606	#endif
607
608	if (uid != geteuid ()
609	\|\| gid != getegid ())
610	ptytty_fatal ("unable to drop privileges, aborting.\n");
611	}
612