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 *
#	Content
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	// helper/proxy support
38
39	#if PTYTTY_HELPER
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	close_tty ();
129
130	if (pty >= 0)
131	close (pty);
132
133	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	ptytty_warn ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n", 0);
314	#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	#else
337	# error no way to drop privileges, configure failed?
338	#endif
339
340	if (uid != geteuid ()
341	\|\| gid != getegid ())
342	ptytty_fatal ("unable to drop privileges, aborting.\n");
343	}
344