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 <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:	1.57
Committed:	Sun Jan 22 12:21:47 2006 UTC (18 years, 4 months ago) by root
Content type:	text/plain
Branch:	MAIN
Changes since 1.56:	+1 -0 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
35	#include <sys/types.h>
36	#include <sys/socket.h>
37	#include <unistd.h>
38	#include <fcntl.h>
39
40	#ifdef HAVE_SYS_IOCTL_H
41	# include <sys/ioctl.h>
42	#endif
43	#if defined(HAVE_DEV_PTMX) && defined(HAVE_SYS_STROPTS_H)
44	# include <sys/stropts.h> /* for I_PUSH */
45	#endif
46	#ifdef HAVE_ISASTREAM
47	# include <stropts.h>
48	#endif
49	#if defined(HAVE_PTY_H)
50	# include <pty.h>
51	#elif defined(HAVE_LIBUTIL_H)
52	# include <libutil.h>
53	#elif defined(HAVE_UTIL_H)
54	# include <util.h>
55	#endif
56	#ifdef TTY_GID_SUPPORT
57	#include <grp.h>
58	#endif
59
60	#include <cstdio>
61
62	/////////////////////////////////////////////////////////////////////////////
63
64	/* ------------------------------------------------------------------------- *
65	* GET PSEUDO TELETYPE - MASTER AND SLAVE *
66	* ------------------------------------------------------------------------- */
67	/*
68	* Returns pty file descriptor, or -1 on failure
69	* If successful, ttydev is set to the name of the slave device.
70	* fd_tty _may_ also be set to an open fd to the slave device
71	*/
72	#if defined(UNIX98_PTY)
73	static int
74	get_pty (int fd_tty, char *ttydev)
75	{
76	int pfd;
77
78	# if defined(HAVE_GETPT)
79	pfd = getpt();
80	# elif defined(HAVE_POSIX_OPENPT)
81	pfd = posix_openpt (O_RDWR);
82	# else
83	pfd = open (CLONE_DEVICE, O_RDWR \| O_NOCTTY, 0);
84	# endif
85	if (pfd >= 0)
86	{
87	if (grantpt (pfd) == 0 /* change slave permissions */
88	&& unlockpt (pfd) == 0)
89	{ /* slave now unlocked */
90	ttydev = strdup (ptsname (pfd)); / get slave's name */
91	return pfd;
92	}
93
94	close (pfd);
95	}
96
97	return -1;
98	}
99	#elif defined(HAVE_OPENPTY)
100	static int
101	get_pty (int fd_tty, char *ttydev)
102	{
103	int pfd;
104	int res;
105	char tty_name[32];
106
107	res = openpty (&pfd, fd_tty, tty_name, NULL, NULL);
108	if (res != -1)
109	{
110	*ttydev = strdup (tty_name);
111	return pfd;
112	}
113
114	return -1;
115	}
116	#elif defined(HAVE__GETPTY)
117	static int
118	get_pty (int fd_tty, char *ttydev)
119	{
120	int pfd;
121
122	*ttydev = _getpty (&pfd, O_RDWR \| O_NONBLOCK \| O_NOCTTY, 0622, 0);
123	if (*ttydev != NULL)
124	return pfd;
125
126	return -1;
127	}
128	#elif defined(HAVE_DEV_PTC)
129	static int
130	get_pty (int fd_tty, char *ttydev)
131	{
132	int pfd;
133
134	if ((pfd = open ("/dev/ptc", O_RDWR \| O_NOCTTY, 0)) >= 0)
135	{
136	*ttydev = strdup (ttyname (pfd));
137	return pfd;
138	}
139
140	return -1;
141	}
142	#elif defined(HAVE_DEV_CLONE)
143	static int
144	get_pty (int fd_tty, char *ttydev)
145	{
146	int pfd;
147
148	if ((pfd = open ("/dev/ptym/clone", O_RDWR \| O_NOCTTY, 0)) >= 0)
149	{
150	*ttydev = strdup (ptsname (pfd));
151	return pfd;
152	}
153
154	return -1;
155	}
156	#else
157	/* Based on the code in openssh/openbsd-compat/bsd-openpty.c */
158	static int
159	get_pty (int fd_tty, char *ttydev)
160	{
161	int pfd;
162	int i;
163	char pty_name[32];
164	char tty_name[32];
165	const char *majors = "pqrstuvwxyzabcde";
166	const char *minors = "0123456789abcdef";
167	for (i = 0; i < 256; i++)
168	{
169	snprintf(pty_name, 32, "/dev/pty%c%c", majors[i / 16], minors[i % 16]);
170	snprintf(tty_name, 32, "/dev/tty%c%c", majors[i / 16], minors[i % 16]);
171	if ((pfd = open (pty_name, O_RDWR \| O_NOCTTY, 0)) == -1)
172	{
173	snprintf(pty_name, 32, "/dev/ptyp%d", i);
174	snprintf(tty_name, 32, "/dev/ttyp%d", i);
175	if ((pfd = open (pty_name, O_RDWR \| O_NOCTTY, 0)) == -1)
176	continue;
177	}
178	if (access (tty_name, R_OK \| W_OK) == 0)
179	{
180	*ttydev = strdup (tty_name);
181	return pfd;
182	}
183
184	close (pfd);
185	}
186	}
187	#endif
188
189	/----------------------------------------------------------------------/
190	/*
191	* Returns tty file descriptor, or -1 on failure
192	*/
193	static int
194	get_tty (char *ttydev)
195	{
196	return open (ttydev, O_RDWR \| O_NOCTTY, 0);
197	}
198
199	/----------------------------------------------------------------------/
200	/*
201	* Make our tty a controlling tty so that /dev/tty points to us
202	*/
203	static int
204	control_tty (int fd_tty)
205	{
206	setsid ();
207
208	#if defined(HAVE_DEV_PTMX) && defined(I_PUSH)
209	/*
210	* Push STREAMS modules:
211	* ptem: pseudo-terminal hardware emulation module.
212	* ldterm: standard terminal line discipline.
213	* ttcompat: V7, 4BSD and XENIX STREAMS compatibility module.
214	*
215	* After we push the STREAMS modules, the first open () on the slave side
216	* (i.e. the next section between the dashes giving us "tty opened OK")
217	* should make the "ptem" (or "ldterm" depending upon either which OS
218	* version or which set of manual pages you have) module give us a
219	* controlling terminal. We must already have close ()d the master side
220	* fd in this child process before we push STREAMS modules on because the
221	* documentation is really unclear about whether it is any close () on
222	* the master side or the last close () - i.e. a proper STREAMS dismantling
223	* close () - on the master side which causes a hang up to be sent
224	* through - Geoff Wing
225	*/
226	# ifdef HAVE_ISASTREAM
227	if (isastream (fd_tty) == 1)
228	# endif
229	{
230	ioctl (fd_tty, I_PUSH, "ptem");
231	ioctl (fd_tty, I_PUSH, "ldterm");
232	ioctl (fd_tty, I_PUSH, "ttcompat");
233	}
234	#endif
235
236	ioctl (fd_tty, TIOCSCTTY, NULL);
237
238	int fd = open ("/dev/tty", O_WRONLY);
239	if (fd < 0)
240	return -1; /* fatal */
241
242	close (fd);
243
244	return 0;
245	}
246
247	void
248	ptytty::close_tty ()
249	{
250	if (tty < 0)
251	return;
252
253	close (tty);
254	tty = -1;
255	}
256
257	bool
258	ptytty::make_controlling_tty ()
259	{
260	return control_tty (tty) >= 0;
261	}
262
263	void
264	ptytty::set_utf8_mode (bool on)
265	{
266	#ifdef IUTF8
267	if (pty < 0)
268	return;
269
270	struct termios tio;
271
272	if (tcgetattr (pty, &tio) != -1)
273	{
274	tcflag_t new_cflag = tio.c_iflag;
275
276	if (on)
277	new_cflag \|= IUTF8;
278	else
279	new_cflag &= ~IUTF8;
280
281	if (new_cflag != tio.c_iflag)
282	{
283	tio.c_iflag = new_cflag;
284	tcsetattr (pty, TCSANOW, &tio);
285	}
286	}
287	#endif
288	}
289
290	static struct ttyconf {
291	gid_t gid;
292	mode_t mode;
293
294	ttyconf ()
295	{
296	#ifdef TTY_GID_SUPPORT
297	struct group *gr = getgrnam ("tty");
298
299	if (gr)
300	{ /* change group ownership of tty to "tty" */
301	mode = S_IRUSR \| S_IWUSR \| S_IWGRP;
302	gid = gr->gr_gid;
303	}
304	else
305	#endif /* TTY_GID_SUPPORT */
306	{
307	mode = S_IRUSR \| S_IWUSR \| S_IWGRP \| S_IWOTH;
308	gid = 0;
309	}
310	}
311	} ttyconf;
312
313	ptytty_unix::ptytty_unix ()
314	{
315	name = 0;
316	#if UTMP_SUPPORT
317	cmd_pid = 0;
318	#endif
319	}
320
321	ptytty_unix::~ptytty_unix ()
322	{
323	#if UTMP_SUPPORT
324	logout ();
325	#endif
326	put ();
327	}
328
329	void
330	ptytty_unix::put ()
331	{
332	chmod (name, RESTORE_TTY_MODE);
333	chown (name, 0, ttyconf.gid);
334
335	close_tty ();
336
337	if (pty >= 0)
338	close (pty);
339
340	free (name);
341
342	pty = tty = -1;
343	name = 0;
344	}
345
346	bool
347	ptytty_unix::get ()
348	{
349	/* get master (pty) */
350	if ((pty = get_pty (&tty, &name)) < 0)
351	return false;
352
353	fcntl (pty, F_SETFL, O_NONBLOCK);
354
355	/* get slave (tty) */
356	if (tty < 0)
357	{
358	#ifndef NO_SETOWNER_TTYDEV
359	chown (name, getuid (), ttyconf.gid); /* fail silently */
360	chmod (name, ttyconf.mode);
361	# ifdef HAVE_REVOKE
362	revoke (name);
363	# endif
364	#endif
365
366	if ((tty = get_tty (name)) < 0)
367	{
368	put ();
369	return false;
370	}
371	}
372
373	return true;
374	}
375
376	#if PTYTTY_HELPER
377
378	static int sock_fd = -1;
379	static int helper_pid, owner_pid;
380
381	struct command
382	{
383	enum { get, login, destroy } type;
384
385	ptytty *id;
386
387	bool login_shell;
388	int cmd_pid;
389	char hostname[512]; // arbitrary, but should be plenty
390	};
391
392	struct ptytty_proxy : ptytty
393	{
394	ptytty *id;
395
396	ptytty_proxy ()
397	: id(0)
398	{
399	}
400
401	~ptytty_proxy ();
402
403	bool get ();
404	void login (int cmd_pid, bool login_shell, const char *hostname);
405	};
406
407	bool
408	ptytty_proxy::get ()
409	{
410	command cmd;
411
412	cmd.type = command::get;
413
414	write (sock_fd, &cmd, sizeof (cmd));
415
416	if (read (sock_fd, &id, sizeof (id)) != sizeof (id))
417	ptytty_fatal ("protocol error while creating pty using helper process, aborting.\n");
418
419	if (!id)
420	return false;
421
422	if ((pty = recv_fd (sock_fd)) < 0
423	\|\| (tty = recv_fd (sock_fd)) < 0)
424	ptytty_fatal ("protocol error while reading pty/tty fds from helper process, aborting.\n");
425
426	return true;
427	}
428
429	void
430	ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname)
431	{
432	command cmd;
433
434	cmd.type = command::login;
435	cmd.id = id;
436	cmd.cmd_pid = cmd_pid;
437	cmd.login_shell = login_shell;
438	strncpy (cmd.hostname, hostname, sizeof (cmd.hostname));
439
440	write (sock_fd, &cmd, sizeof (cmd));
441	}
442
443	ptytty_proxy::~ptytty_proxy ()
444	{
445	if (id)
446	{
447	command cmd;
448
449	cmd.type = command::destroy;
450	cmd.id = id;
451
452	write (sock_fd, &cmd, sizeof (cmd));
453	}
454	}
455
456	static
457	void serve ()
458	{
459	command cmd;
460	vector<ptytty *> ptys;
461
462	while (read (sock_fd, &cmd, sizeof (command)) == sizeof (command))
463	{
464	if (cmd.type == command::get)
465	{
466	// -> id ptyfd ttyfd
467	cmd.id = new ptytty_unix;
468
469	if (cmd.id->get ())
470	{
471	write (sock_fd, &cmd.id, sizeof (cmd.id));
472	ptys.push_back (cmd.id);
473
474	ptytty::send_fd (sock_fd, cmd.id->pty);
475	ptytty::send_fd (sock_fd, cmd.id->tty);
476	}
477	else
478	{
479	delete cmd.id;
480	cmd.id = 0;
481	write (sock_fd, &cmd.id, sizeof (cmd.id));
482	}
483	}
484	else if (cmd.type == command::login)
485	{
486	#if UTMP_SUPPORT
487	if (find (ptys.begin (), ptys.end (), cmd.id))
488	{
489	cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
490	cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
491	}
492	#endif
493	}
494	else if (cmd.type == command::destroy)
495	{
496	vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);
497
498	if (pty != ptys.end ())
499	{
500	delete *pty;
501	ptys.erase (pty);
502	}
503	}
504	else
505	break;
506	}
507
508	// destroy all ptys
509	for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
510	delete *i;
511	}
512
513	void
514	ptytty::use_helper ()
515	{
516	int pid = getpid ();
517
518	if (sock_fd >= 0 && pid == owner_pid)
519	return;
520
521	owner_pid = pid;
522
523	int sv[2];
524
525	if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
526	ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
527
528	helper_pid = fork ();
529
530	if (helper_pid < 0)
531	ptytty_fatal ("could not create pty/sessiondb helper process, aborting.\n");
532
533	if (helper_pid)
534	{
535	// client, process
536	sock_fd = sv[0];
537	close (sv[1]);
538	fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
539	}
540	else
541	{
542	// server, pty-helper
543	sock_fd = sv[1];
544
545	chdir ("/");
546
547	for (int fd = 0; fd < 1023; fd++)
548	if (fd != sock_fd)
549	close (fd);
550
551	serve ();
552	_exit (EXIT_SUCCESS);
553	}
554	}
555
556	#endif
557
558	ptytty *
559	ptytty::create ()
560	{
561	#if PTYTTY_HELPER
562	if (helper_pid && getpid () == owner_pid)
563	// use helper process
564	return new ptytty_proxy;
565	else
566	#endif
567	return new ptytty_unix;
568	}
569
570	void
571	ptytty::init ()
572	{
573	uid_t uid = getuid ();
574	gid_t gid = getgid ();
575
576	// before doing anything else, check for setuid/setgid operation,
577	// start the helper process and drop privileges
578	if (uid != geteuid ()
579	\|\| gid != getegid ())
580	{
581	#if PTYTTY_HELPER
582	use_helper ();
583	#else
584	ptytty_warn ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n");
585	#endif
586
587	drop_privileges ();
588	}
589	}
590
591	void
592	ptytty::drop_privileges ()
593	{
594	uid_t uid = getuid ();
595	gid_t gid = getgid ();
596
597	// drop privileges
598	#if HAVE_SETRESUID
599	setresgid (gid, gid, gid);
600	setresuid (uid, uid, uid);
601	#elif HAVE_SETREUID
602	setregid (gid, gid);
603	setreuid (uid, uid);
604	#elif HAVE_SETUID
605	setgid (gid);
606	setuid (uid);
607	#endif
608
609	if (uid != geteuid ()
610	\|\| gid != getegid ())
611	ptytty_fatal ("unable to drop privileges, aborting.\n");
612	}
613