rxvt-unicode/src/proxy.C

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

/*----------------------------------------------------------------------*
 * File:        proxy.C
 *----------------------------------------------------------------------*
 *
 * All portions of code are copyright by their respective author/s.
 * Copyright (c) 2006      Marc Lehmann <schmorp@schmorp.de>
 *
 * 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 <cstdio>
#include <cstring>
#include <csignal>

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

// 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)
    {
      close_tty ();

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

      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::sanitise_stdfd ()
{
  // sanitise stdin/stdout/stderr to point to *something*.
  for (int fd = 0; fd <= 2; ++fd)
    if (fcntl (fd, F_GETFL) < 0 && errno == EBADF)
      {
        int fd2 = open ("/dev/tty", fd ? O_WRONLY : O_RDONLY);

        if (fd2 < 0)
          fd2 = open ("/dev/null", fd ? O_WRONLY : O_RDONLY);

        if (fd2 != fd)
          abort ();
      }
}

void
ptytty::init ()
{
  sanitise_stdfd ();

  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", 0);
#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);
#else
# error no way to drop privileges, configure failed?
#endif

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

Revision:	1.12
Committed:	Mon May 30 21:24:42 2011 UTC (12 years, 11 months ago) by sf-exg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.11:	+0 -0 lines
State:	*FILE REMOVED*
Log Message:	Embed libptytty.
#	User	Rev	Content
1	root	1.1	// This file is part of libptytty. Do not make local modifications.
2			// http://software.schmorp.de/pkg/libptytty
3
4			/----------------------------------------------------------------------
5			* File: proxy.C
6			----------------------------------------------------------------------
7			*
8			* All portions of code are copyright by their respective author/s.
9	root	1.11	* Copyright (c) 2006 Marc Lehmann <schmorp@schmorp.de>
10	root	1.1	*
11			* This program is free software; you can redistribute it and/or modify
12			* it under the terms of the GNU General Public License as published by
13			* the Free Software Foundation; either version 2 of the License, or
14			* (at your option) any later version.
15			*
16			* This program is distributed in the hope that it will be useful,
17			* but WITHOUT ANY WARRANTY; without even the implied warranty of
18			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19			* GNU General Public License for more details.
20			*
21			* You should have received a copy of the GNU General Public License
22			* along with this program; if not, write to the Free Software
23			* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24			---------------------------------------------------------------------/
25
26	sf-exg	1.10	#include "config.h"
27	root	1.1
28			#include "ptytty.h"
29
30	root	1.9	#include <cstdio>
31			#include <cstring>
32	root	1.1	#include <csignal>
33
34			#include <sys/types.h>
35			#include <sys/socket.h>
36			#include <unistd.h>
37			#include <fcntl.h>
38	root	1.7	#include <errno.h>
39	root	1.1
40	root	1.4	// helper/proxy support
41
42			#if PTYTTY_HELPER
43
44	root	1.1	static int sock_fd = -1, lock_fd = -1;
45			static int helper_pid, owner_pid;
46
47			struct command
48			{
49			enum { get, login, destroy } type;
50
51			ptytty *id;
52
53			bool login_shell;
54			int cmd_pid;
55			char hostname[512]; // arbitrary, but should be plenty
56			};
57
58			struct ptytty_proxy : ptytty
59			{
60			ptytty *id;
61
62			ptytty_proxy ()
63			: id(0)
64			{
65			}
66
67			~ptytty_proxy ();
68
69			bool get ();
70			void login (int cmd_pid, bool login_shell, const char *hostname);
71			};
72
73			#if PTYTTY_REENTRANT
74			# define NEED_TOKEN do { char ch; read (lock_fd, &ch, 1); } while (0)
75			# define GIVE_TOKEN do { char ch; write (lock_fd, &ch, 1); } while (0)
76			#else
77			# define NEED_TOKEN (void)0
78			# define GIVE_TOKEN (void)0
79			#endif
80
81			bool
82			ptytty_proxy::get ()
83			{
84			NEED_TOKEN;
85
86			command cmd;
87
88			cmd.type = command::get;
89
90			write (sock_fd, &cmd, sizeof (cmd));
91
92			if (read (sock_fd, &id, sizeof (id)) != sizeof (id))
93			ptytty_fatal ("protocol error while creating pty using helper process, aborting.\n");
94
95			if (!id)
96			{
97			GIVE_TOKEN;
98			return false;
99			}
100
101			if ((pty = recv_fd (sock_fd)) < 0
102			\|\| (tty = recv_fd (sock_fd)) < 0)
103			ptytty_fatal ("protocol error while reading pty/tty fds from helper process, aborting.\n");
104
105			GIVE_TOKEN;
106			return true;
107			}
108
109			void
110			ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname)
111			{
112			NEED_TOKEN;
113
114			command cmd;
115
116			cmd.type = command::login;
117			cmd.id = id;
118			cmd.cmd_pid = cmd_pid;
119			cmd.login_shell = login_shell;
120			strncpy (cmd.hostname, hostname, sizeof (cmd.hostname));
121
122			write (sock_fd, &cmd, sizeof (cmd));
123
124			GIVE_TOKEN;
125			}
126
127			ptytty_proxy::~ptytty_proxy ()
128			{
129			if (id)
130			{
131	root	1.6	close_tty ();
132
133			if (pty >= 0)
134			close (pty);
135	ayin	1.5
136	root	1.1	NEED_TOKEN;
137
138			command cmd;
139
140			cmd.type = command::destroy;
141			cmd.id = id;
142
143			write (sock_fd, &cmd, sizeof (cmd));
144
145			GIVE_TOKEN;
146			}
147			}
148
149			static
150			void serve ()
151			{
152			command cmd;
153			vector<ptytty *> ptys;
154
155			for (;;)
156			{
157			GIVE_TOKEN;
158
159			if (read (sock_fd, &cmd, sizeof (command)) != sizeof (command))
160			break;
161
162			if (cmd.type == command::get)
163			{
164			// -> id ptyfd ttyfd
165			cmd.id = new ptytty_unix;
166
167			if (cmd.id->get ())
168			{
169			write (sock_fd, &cmd.id, sizeof (cmd.id));
170			ptys.push_back (cmd.id);
171
172			ptytty::send_fd (sock_fd, cmd.id->pty);
173			ptytty::send_fd (sock_fd, cmd.id->tty);
174			}
175			else
176			{
177			delete cmd.id;
178			cmd.id = 0;
179			write (sock_fd, &cmd.id, sizeof (cmd.id));
180			}
181			}
182			else if (cmd.type == command::login)
183			{
184			#if UTMP_SUPPORT
185			if (find (ptys.begin (), ptys.end (), cmd.id) != ptys.end ())
186			{
187			cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
188			cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
189			}
190			#endif
191			}
192			else if (cmd.type == command::destroy)
193			{
194			vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);
195
196			if (pty != ptys.end ())
197			{
198			delete *pty;
199			ptys.erase (pty);
200			}
201			}
202			else
203			break;
204
205			NEED_TOKEN;
206			}
207
208			// destroy all ptys
209			for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
210			delete *i;
211			}
212
213			void
214			ptytty::use_helper ()
215			{
216			#ifndef PTYTTY_NO_PID_CHECK
217			int pid = getpid ();
218			#endif
219
220			if (sock_fd >= 0
221			#ifndef PTYTTY_NO_PID_CHECK
222			&& pid == owner_pid
223			#endif
224			)
225			return;
226
227			#ifndef PTYTTY_NO_PID_CHECK
228			owner_pid = pid;
229			#endif
230
231			int sv[2];
232
233			if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
234			ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
235
236			#ifdef PTYTTY_REENTRANT
237			int lv[2];
238
239			if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
240			ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
241			#endif
242
243			helper_pid = fork ();
244
245			if (helper_pid < 0)
246			ptytty_fatal ("could not create pty/sessiondb helper process, aborting.\n");
247
248			if (helper_pid)
249			{
250			// client, process
251			sock_fd = sv[0];
252			close (sv[1]);
253			fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
254			#ifdef PTYTTY_REENTRANT
255			lock_fd = lv[0];
256			close (lv[1]);
257			fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
258			#endif
259			}
260			else
261			{
262			// server, pty-helper
263			sock_fd = sv[1];
264			#ifdef PTYTTY_REENTRANT
265			lock_fd = lv[1];
266			#endif
267
268			chdir ("/");
269
270			signal (SIGHUP, SIG_IGN);
271			signal (SIGTERM, SIG_IGN);
272			signal (SIGINT, SIG_IGN);
273			signal (SIGPIPE, SIG_IGN);
274
275			for (int fd = 0; fd < 1023; fd++)
276			if (fd != sock_fd && fd != lock_fd)
277			close (fd);
278
279			serve ();
280			_exit (EXIT_SUCCESS);
281			}
282			}
283
284			#endif
285
286			ptytty *
287			ptytty::create ()
288			{
289			#if PTYTTY_HELPER
290			if (helper_pid
291			# ifndef PTYTTY_NO_PID_CHECK
292			&& getpid () == owner_pid
293			# endif
294			)
295			// use helper process
296			return new ptytty_proxy;
297			else
298			#endif
299			return new ptytty_unix;
300			}
301
302			void
303	root	1.7	ptytty::sanitise_stdfd ()
304			{
305			// sanitise stdin/stdout/stderr to point to something.
306			for (int fd = 0; fd <= 2; ++fd)
307			if (fcntl (fd, F_GETFL) < 0 && errno == EBADF)
308			{
309			int fd2 = open ("/dev/tty", fd ? O_WRONLY : O_RDONLY);
310
311			if (fd2 < 0)
312			fd2 = open ("/dev/null", fd ? O_WRONLY : O_RDONLY);
313
314			if (fd2 != fd)
315			abort ();
316			}
317			}
318
319			void
320	root	1.1	ptytty::init ()
321			{
322	root	1.7	sanitise_stdfd ();
323
324	root	1.1	uid_t uid = getuid ();
325			gid_t gid = getgid ();
326	root	1.8
327	root	1.1	// before doing anything else, check for setuid/setgid operation,
328			// start the helper process and drop privileges
329			if (uid != geteuid ()
330			\|\| gid != getegid ())
331			{
332			#if PTYTTY_HELPER
333			use_helper ();
334			#else
335	root	1.2	ptytty_warn ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n", 0);
336	root	1.1	#endif
337
338			drop_privileges ();
339			}
340			}
341
342			void
343			ptytty::drop_privileges ()
344			{
345			uid_t uid = getuid ();
346			gid_t gid = getgid ();
347
348			// drop privileges
349			#if HAVE_SETRESUID
350			setresgid (gid, gid, gid);
351			setresuid (uid, uid, uid);
352			#elif HAVE_SETREUID
353			setregid (gid, gid);
354			setreuid (uid, uid);
355			#elif HAVE_SETUID
356			setgid (gid);
357			setuid (uid);
358	root	1.3	#else
359			# error no way to drop privileges, configure failed?
360	root	1.1	#endif
361
362			if (uid != geteuid ()
363			\|\| gid != getegid ())
364			ptytty_fatal ("unable to drop privileges, aborting.\n");
365			}
366