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 <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 <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:	1.7
Committed:	Mon Feb 12 17:34:58 2007 UTC (17 years, 3 months ago) by root
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rel-8_2, rel-8_3
Changes since 1.6:	+20 -0 lines
Log Message:	* empty log message *
#	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			* Copyright (c) 2006 Marc Lehmann <pcg@goof.com>
10			*
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			#include "../config.h"
27
28			#include "ptytty.h"
29
30			#include <csignal>
31
32			#include <sys/types.h>
33			#include <sys/socket.h>
34			#include <unistd.h>
35			#include <fcntl.h>
36	root	1.7	#include <errno.h>
37	root	1.1
38	root	1.4	// helper/proxy support
39
40			#if PTYTTY_HELPER
41
42	root	1.1	static int sock_fd = -1, lock_fd = -1;
43			static int helper_pid, owner_pid;
44
45			struct command
46			{
47			enum { get, login, destroy } type;
48
49			ptytty *id;
50
51			bool login_shell;
52			int cmd_pid;
53			char hostname[512]; // arbitrary, but should be plenty
54			};
55
56			struct ptytty_proxy : ptytty
57			{
58			ptytty *id;
59
60			ptytty_proxy ()
61			: id(0)
62			{
63			}
64
65			~ptytty_proxy ();
66
67			bool get ();
68			void login (int cmd_pid, bool login_shell, const char *hostname);
69			};
70
71			#if PTYTTY_REENTRANT
72			# define NEED_TOKEN do { char ch; read (lock_fd, &ch, 1); } while (0)
73			# define GIVE_TOKEN do { char ch; write (lock_fd, &ch, 1); } while (0)
74			#else
75			# define NEED_TOKEN (void)0
76			# define GIVE_TOKEN (void)0
77			#endif
78
79			bool
80			ptytty_proxy::get ()
81			{
82			NEED_TOKEN;
83
84			command cmd;
85
86			cmd.type = command::get;
87
88			write (sock_fd, &cmd, sizeof (cmd));
89
90			if (read (sock_fd, &id, sizeof (id)) != sizeof (id))
91			ptytty_fatal ("protocol error while creating pty using helper process, aborting.\n");
92
93			if (!id)
94			{
95			GIVE_TOKEN;
96			return false;
97			}
98
99			if ((pty = recv_fd (sock_fd)) < 0
100			\|\| (tty = recv_fd (sock_fd)) < 0)
101			ptytty_fatal ("protocol error while reading pty/tty fds from helper process, aborting.\n");
102
103			GIVE_TOKEN;
104			return true;
105			}
106
107			void
108			ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname)
109			{
110			NEED_TOKEN;
111
112			command cmd;
113
114			cmd.type = command::login;
115			cmd.id = id;
116			cmd.cmd_pid = cmd_pid;
117			cmd.login_shell = login_shell;
118			strncpy (cmd.hostname, hostname, sizeof (cmd.hostname));
119
120			write (sock_fd, &cmd, sizeof (cmd));
121
122			GIVE_TOKEN;
123			}
124
125			ptytty_proxy::~ptytty_proxy ()
126			{
127			if (id)
128			{
129	root	1.6	close_tty ();
130
131			if (pty >= 0)
132			close (pty);
133	ayin	1.5
134	root	1.1	NEED_TOKEN;
135
136			command cmd;
137
138			cmd.type = command::destroy;
139			cmd.id = id;
140
141			write (sock_fd, &cmd, sizeof (cmd));
142
143			GIVE_TOKEN;
144			}
145			}
146
147			static
148			void serve ()
149			{
150			command cmd;
151			vector<ptytty *> ptys;
152
153			for (;;)
154			{
155			GIVE_TOKEN;
156
157			if (read (sock_fd, &cmd, sizeof (command)) != sizeof (command))
158			break;
159
160			if (cmd.type == command::get)
161			{
162			// -> id ptyfd ttyfd
163			cmd.id = new ptytty_unix;
164
165			if (cmd.id->get ())
166			{
167			write (sock_fd, &cmd.id, sizeof (cmd.id));
168			ptys.push_back (cmd.id);
169
170			ptytty::send_fd (sock_fd, cmd.id->pty);
171			ptytty::send_fd (sock_fd, cmd.id->tty);
172			}
173			else
174			{
175			delete cmd.id;
176			cmd.id = 0;
177			write (sock_fd, &cmd.id, sizeof (cmd.id));
178			}
179			}
180			else if (cmd.type == command::login)
181			{
182			#if UTMP_SUPPORT
183			if (find (ptys.begin (), ptys.end (), cmd.id) != ptys.end ())
184			{
185			cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
186			cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
187			}
188			#endif
189			}
190			else if (cmd.type == command::destroy)
191			{
192			vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);
193
194			if (pty != ptys.end ())
195			{
196			delete *pty;
197			ptys.erase (pty);
198			}
199			}
200			else
201			break;
202
203			NEED_TOKEN;
204			}
205
206			// destroy all ptys
207			for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
208			delete *i;
209			}
210
211			void
212			ptytty::use_helper ()
213			{
214			#ifndef PTYTTY_NO_PID_CHECK
215			int pid = getpid ();
216			#endif
217
218			if (sock_fd >= 0
219			#ifndef PTYTTY_NO_PID_CHECK
220			&& pid == owner_pid
221			#endif
222			)
223			return;
224
225			#ifndef PTYTTY_NO_PID_CHECK
226			owner_pid = pid;
227			#endif
228
229			int sv[2];
230
231			if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
232			ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
233
234			#ifdef PTYTTY_REENTRANT
235			int lv[2];
236
237			if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
238			ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
239			#endif
240
241			helper_pid = fork ();
242
243			if (helper_pid < 0)
244			ptytty_fatal ("could not create pty/sessiondb helper process, aborting.\n");
245
246			if (helper_pid)
247			{
248			// client, process
249			sock_fd = sv[0];
250			close (sv[1]);
251			fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
252			#ifdef PTYTTY_REENTRANT
253			lock_fd = lv[0];
254			close (lv[1]);
255			fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
256			#endif
257			}
258			else
259			{
260			// server, pty-helper
261			sock_fd = sv[1];
262			#ifdef PTYTTY_REENTRANT
263			lock_fd = lv[1];
264			#endif
265
266			chdir ("/");
267
268			signal (SIGHUP, SIG_IGN);
269			signal (SIGTERM, SIG_IGN);
270			signal (SIGINT, SIG_IGN);
271			signal (SIGPIPE, SIG_IGN);
272
273			for (int fd = 0; fd < 1023; fd++)
274			if (fd != sock_fd && fd != lock_fd)
275			close (fd);
276
277			serve ();
278			_exit (EXIT_SUCCESS);
279			}
280			}
281
282			#endif
283
284			ptytty *
285			ptytty::create ()
286			{
287			#if PTYTTY_HELPER
288			if (helper_pid
289			# ifndef PTYTTY_NO_PID_CHECK
290			&& getpid () == owner_pid
291			# endif
292			)
293			// use helper process
294			return new ptytty_proxy;
295			else
296			#endif
297			return new ptytty_unix;
298			}
299
300			void
301	root	1.7	ptytty::sanitise_stdfd ()
302			{
303			// sanitise stdin/stdout/stderr to point to something.
304			for (int fd = 0; fd <= 2; ++fd)
305			if (fcntl (fd, F_GETFL) < 0 && errno == EBADF)
306			{
307			int fd2 = open ("/dev/tty", fd ? O_WRONLY : O_RDONLY);
308
309			if (fd2 < 0)
310			fd2 = open ("/dev/null", fd ? O_WRONLY : O_RDONLY);
311
312			if (fd2 != fd)
313			abort ();
314			}
315			}
316
317			void
318	root	1.1	ptytty::init ()
319			{
320	root	1.7	sanitise_stdfd ();
321
322	root	1.1	uid_t uid = getuid ();
323			gid_t gid = getgid ();
324
325			// before doing anything else, check for setuid/setgid operation,
326			// start the helper process and drop privileges
327			if (uid != geteuid ()
328			\|\| gid != getegid ())
329			{
330			#if PTYTTY_HELPER
331			use_helper ();
332			#else
333	root	1.2	ptytty_warn ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n", 0);
334	root	1.1	#endif
335
336			drop_privileges ();
337			}
338			}
339
340			void
341			ptytty::drop_privileges ()
342			{
343			uid_t uid = getuid ();
344			gid_t gid = getgid ();
345
346			// drop privileges
347			#if HAVE_SETRESUID
348			setresgid (gid, gid, gid);
349			setresuid (uid, uid, uid);
350			#elif HAVE_SETREUID
351			setregid (gid, gid);
352			setreuid (uid, uid);
353			#elif HAVE_SETUID
354			setgid (gid);
355			setuid (uid);
356	root	1.3	#else
357			# error no way to drop privileges, configure failed?
358	root	1.1	#endif
359
360			if (uid != geteuid ()
361			\|\| gid != getegid ())
362			ptytty_fatal ("unable to drop privileges, aborting.\n");
363			}
364