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"

// helper/proxy support

#if PTYTTY_HELPER

#include <csignal>

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

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)
    {
      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");
#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:	1.1
Committed:	Wed Jan 25 10:51:26 2006 UTC (18 years, 4 months ago) by root
Content type:	text/plain
Branch:	MAIN
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			// helper/proxy support
31
32			#if PTYTTY_HELPER
33
34			#include <csignal>
35
36			#include <sys/types.h>
37			#include <sys/socket.h>
38			#include <unistd.h>
39			#include <fcntl.h>
40
41			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			NEED_TOKEN;
129
130			command cmd;
131
132			cmd.type = command::destroy;
133			cmd.id = id;
134
135			write (sock_fd, &cmd, sizeof (cmd));
136
137			GIVE_TOKEN;
138			}
139			}
140
141			static
142			void serve ()
143			{
144			command cmd;
145			vector<ptytty *> ptys;
146
147			for (;;)
148			{
149			GIVE_TOKEN;
150
151			if (read (sock_fd, &cmd, sizeof (command)) != sizeof (command))
152			break;
153
154			if (cmd.type == command::get)
155			{
156			// -> id ptyfd ttyfd
157			cmd.id = new ptytty_unix;
158
159			if (cmd.id->get ())
160			{
161			write (sock_fd, &cmd.id, sizeof (cmd.id));
162			ptys.push_back (cmd.id);
163
164			ptytty::send_fd (sock_fd, cmd.id->pty);
165			ptytty::send_fd (sock_fd, cmd.id->tty);
166			}
167			else
168			{
169			delete cmd.id;
170			cmd.id = 0;
171			write (sock_fd, &cmd.id, sizeof (cmd.id));
172			}
173			}
174			else if (cmd.type == command::login)
175			{
176			#if UTMP_SUPPORT
177			if (find (ptys.begin (), ptys.end (), cmd.id) != ptys.end ())
178			{
179			cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
180			cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
181			}
182			#endif
183			}
184			else if (cmd.type == command::destroy)
185			{
186			vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);
187
188			if (pty != ptys.end ())
189			{
190			delete *pty;
191			ptys.erase (pty);
192			}
193			}
194			else
195			break;
196
197			NEED_TOKEN;
198			}
199
200			// destroy all ptys
201			for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
202			delete *i;
203			}
204
205			void
206			ptytty::use_helper ()
207			{
208			#ifndef PTYTTY_NO_PID_CHECK
209			int pid = getpid ();
210			#endif
211
212			if (sock_fd >= 0
213			#ifndef PTYTTY_NO_PID_CHECK
214			&& pid == owner_pid
215			#endif
216			)
217			return;
218
219			#ifndef PTYTTY_NO_PID_CHECK
220			owner_pid = pid;
221			#endif
222
223			int sv[2];
224
225			if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
226			ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
227
228			#ifdef PTYTTY_REENTRANT
229			int lv[2];
230
231			if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
232			ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
233			#endif
234
235			helper_pid = fork ();
236
237			if (helper_pid < 0)
238			ptytty_fatal ("could not create pty/sessiondb helper process, aborting.\n");
239
240			if (helper_pid)
241			{
242			// client, process
243			sock_fd = sv[0];
244			close (sv[1]);
245			fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
246			#ifdef PTYTTY_REENTRANT
247			lock_fd = lv[0];
248			close (lv[1]);
249			fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
250			#endif
251			}
252			else
253			{
254			// server, pty-helper
255			sock_fd = sv[1];
256			#ifdef PTYTTY_REENTRANT
257			lock_fd = lv[1];
258			#endif
259
260			chdir ("/");
261
262			signal (SIGHUP, SIG_IGN);
263			signal (SIGTERM, SIG_IGN);
264			signal (SIGINT, SIG_IGN);
265			signal (SIGPIPE, SIG_IGN);
266
267			for (int fd = 0; fd < 1023; fd++)
268			if (fd != sock_fd && fd != lock_fd)
269			close (fd);
270
271			serve ();
272			_exit (EXIT_SUCCESS);
273			}
274			}
275
276			#endif
277
278			ptytty *
279			ptytty::create ()
280			{
281			#if PTYTTY_HELPER
282			if (helper_pid
283			# ifndef PTYTTY_NO_PID_CHECK
284			&& getpid () == owner_pid
285			# endif
286			)
287			// use helper process
288			return new ptytty_proxy;
289			else
290			#endif
291			return new ptytty_unix;
292			}
293
294			void
295			ptytty::init ()
296			{
297			uid_t uid = getuid ();
298			gid_t gid = getgid ();
299
300			// before doing anything else, check for setuid/setgid operation,
301			// start the helper process and drop privileges
302			if (uid != geteuid ()
303			\|\| gid != getegid ())
304			{
305			#if PTYTTY_HELPER
306			use_helper ();
307			#else
308			ptytty_warn ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n");
309			#endif
310
311			drop_privileges ();
312			}
313			}
314
315			void
316			ptytty::drop_privileges ()
317			{
318			uid_t uid = getuid ();
319			gid_t gid = getgid ();
320
321			// drop privileges
322			#if HAVE_SETRESUID
323			setresgid (gid, gid, gid);
324			setresuid (uid, uid, uid);
325			#elif HAVE_SETREUID
326			setregid (gid, gid);
327			setreuid (uid, uid);
328			#elif HAVE_SETUID
329			setgid (gid);
330			setuid (uid);
331			#endif
332
333			if (uid != geteuid ()
334			\|\| gid != getegid ())
335			ptytty_fatal ("unable to drop privileges, aborting.\n");
336			}
337