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>

// 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::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", 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:	1.6
Committed:	Sat Jan 20 00:55:01 2007 UTC (17 years, 4 months ago) by root
Content type:	text/plain
Branch:	MAIN
Changes since 1.5:	+4 -1 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
37	root	1.4	// helper/proxy support
38
39			#if PTYTTY_HELPER
40
41	root	1.1	static int sock_fd = -1, lock_fd = -1;
42			static int helper_pid, owner_pid;
43
44			struct command
45			{
46			enum { get, login, destroy } type;
47
48			ptytty *id;
49
50			bool login_shell;
51			int cmd_pid;
52			char hostname[512]; // arbitrary, but should be plenty
53			};
54
55			struct ptytty_proxy : ptytty
56			{
57			ptytty *id;
58
59			ptytty_proxy ()
60			: id(0)
61			{
62			}
63
64			~ptytty_proxy ();
65
66			bool get ();
67			void login (int cmd_pid, bool login_shell, const char *hostname);
68			};
69
70			#if PTYTTY_REENTRANT
71			# define NEED_TOKEN do { char ch; read (lock_fd, &ch, 1); } while (0)
72			# define GIVE_TOKEN do { char ch; write (lock_fd, &ch, 1); } while (0)
73			#else
74			# define NEED_TOKEN (void)0
75			# define GIVE_TOKEN (void)0
76			#endif
77
78			bool
79			ptytty_proxy::get ()
80			{
81			NEED_TOKEN;
82
83			command cmd;
84
85			cmd.type = command::get;
86
87			write (sock_fd, &cmd, sizeof (cmd));
88
89			if (read (sock_fd, &id, sizeof (id)) != sizeof (id))
90			ptytty_fatal ("protocol error while creating pty using helper process, aborting.\n");
91
92			if (!id)
93			{
94			GIVE_TOKEN;
95			return false;
96			}
97
98			if ((pty = recv_fd (sock_fd)) < 0
99			\|\| (tty = recv_fd (sock_fd)) < 0)
100			ptytty_fatal ("protocol error while reading pty/tty fds from helper process, aborting.\n");
101
102			GIVE_TOKEN;
103			return true;
104			}
105
106			void
107			ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname)
108			{
109			NEED_TOKEN;
110
111			command cmd;
112
113			cmd.type = command::login;
114			cmd.id = id;
115			cmd.cmd_pid = cmd_pid;
116			cmd.login_shell = login_shell;
117			strncpy (cmd.hostname, hostname, sizeof (cmd.hostname));
118
119			write (sock_fd, &cmd, sizeof (cmd));
120
121			GIVE_TOKEN;
122			}
123
124			ptytty_proxy::~ptytty_proxy ()
125			{
126			if (id)
127			{
128	root	1.6	close_tty ();
129
130			if (pty >= 0)
131			close (pty);
132	ayin	1.5
133	root	1.1	NEED_TOKEN;
134
135			command cmd;
136
137			cmd.type = command::destroy;
138			cmd.id = id;
139
140			write (sock_fd, &cmd, sizeof (cmd));
141
142			GIVE_TOKEN;
143			}
144			}
145
146			static
147			void serve ()
148			{
149			command cmd;
150			vector<ptytty *> ptys;
151
152			for (;;)
153			{
154			GIVE_TOKEN;
155
156			if (read (sock_fd, &cmd, sizeof (command)) != sizeof (command))
157			break;
158
159			if (cmd.type == command::get)
160			{
161			// -> id ptyfd ttyfd
162			cmd.id = new ptytty_unix;
163
164			if (cmd.id->get ())
165			{
166			write (sock_fd, &cmd.id, sizeof (cmd.id));
167			ptys.push_back (cmd.id);
168
169			ptytty::send_fd (sock_fd, cmd.id->pty);
170			ptytty::send_fd (sock_fd, cmd.id->tty);
171			}
172			else
173			{
174			delete cmd.id;
175			cmd.id = 0;
176			write (sock_fd, &cmd.id, sizeof (cmd.id));
177			}
178			}
179			else if (cmd.type == command::login)
180			{
181			#if UTMP_SUPPORT
182			if (find (ptys.begin (), ptys.end (), cmd.id) != ptys.end ())
183			{
184			cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
185			cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
186			}
187			#endif
188			}
189			else if (cmd.type == command::destroy)
190			{
191			vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);
192
193			if (pty != ptys.end ())
194			{
195			delete *pty;
196			ptys.erase (pty);
197			}
198			}
199			else
200			break;
201
202			NEED_TOKEN;
203			}
204
205			// destroy all ptys
206			for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
207			delete *i;
208			}
209
210			void
211			ptytty::use_helper ()
212			{
213			#ifndef PTYTTY_NO_PID_CHECK
214			int pid = getpid ();
215			#endif
216
217			if (sock_fd >= 0
218			#ifndef PTYTTY_NO_PID_CHECK
219			&& pid == owner_pid
220			#endif
221			)
222			return;
223
224			#ifndef PTYTTY_NO_PID_CHECK
225			owner_pid = pid;
226			#endif
227
228			int sv[2];
229
230			if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
231			ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
232
233			#ifdef PTYTTY_REENTRANT
234			int lv[2];
235
236			if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
237			ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
238			#endif
239
240			helper_pid = fork ();
241
242			if (helper_pid < 0)
243			ptytty_fatal ("could not create pty/sessiondb helper process, aborting.\n");
244
245			if (helper_pid)
246			{
247			// client, process
248			sock_fd = sv[0];
249			close (sv[1]);
250			fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
251			#ifdef PTYTTY_REENTRANT
252			lock_fd = lv[0];
253			close (lv[1]);
254			fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
255			#endif
256			}
257			else
258			{
259			// server, pty-helper
260			sock_fd = sv[1];
261			#ifdef PTYTTY_REENTRANT
262			lock_fd = lv[1];
263			#endif
264
265			chdir ("/");
266
267			signal (SIGHUP, SIG_IGN);
268			signal (SIGTERM, SIG_IGN);
269			signal (SIGINT, SIG_IGN);
270			signal (SIGPIPE, SIG_IGN);
271
272			for (int fd = 0; fd < 1023; fd++)
273			if (fd != sock_fd && fd != lock_fd)
274			close (fd);
275
276			serve ();
277			_exit (EXIT_SUCCESS);
278			}
279			}
280
281			#endif
282
283			ptytty *
284			ptytty::create ()
285			{
286			#if PTYTTY_HELPER
287			if (helper_pid
288			# ifndef PTYTTY_NO_PID_CHECK
289			&& getpid () == owner_pid
290			# endif
291			)
292			// use helper process
293			return new ptytty_proxy;
294			else
295			#endif
296			return new ptytty_unix;
297			}
298
299			void
300			ptytty::init ()
301			{
302			uid_t uid = getuid ();
303			gid_t gid = getgid ();
304
305			// before doing anything else, check for setuid/setgid operation,
306			// start the helper process and drop privileges
307			if (uid != geteuid ()
308			\|\| gid != getegid ())
309			{
310			#if PTYTTY_HELPER
311			use_helper ();
312			#else
313	root	1.2	ptytty_warn ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n", 0);
314	root	1.1	#endif
315
316			drop_privileges ();
317			}
318			}
319
320			void
321			ptytty::drop_privileges ()
322			{
323			uid_t uid = getuid ();
324			gid_t gid = getgid ();
325
326			// drop privileges
327			#if HAVE_SETRESUID
328			setresgid (gid, gid, gid);
329			setresuid (uid, uid, uid);
330			#elif HAVE_SETREUID
331			setregid (gid, gid);
332			setreuid (uid, uid);
333			#elif HAVE_SETUID
334			setgid (gid);
335			setuid (uid);
336	root	1.3	#else
337			# error no way to drop privileges, configure failed?
338	root	1.1	#endif
339
340			if (uid != geteuid ()
341			\|\| gid != getegid ())
342			ptytty_fatal ("unable to drop privileges, aborting.\n");
343			}
344