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:	1.8
Committed:	Thu Aug 2 13:54:17 2007 UTC (16 years, 9 months ago) by root
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rel-9_0, rel-8_5a, rel-8_9, rel-8_8, rel-8_4, rel-8_6, rel-8_7, rel-9_02, rel-9_01, rel-9_06, rel-9_05
Changes since 1.7:	+1 -1 lines
Log Message:	inconsequential changes
#	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	#include <errno.h>
37
38	// helper/proxy support
39
40	#if PTYTTY_HELPER
41
42	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	close_tty ();
130
131	if (pty >= 0)
132	close (pty);
133
134	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	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	ptytty::init ()
319	{
320	sanitise_stdfd ();
321
322	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	ptytty_warn ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n", 0);
334	#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	#else
357	# error no way to drop privileges, configure failed?
358	#endif
359
360	if (uid != geteuid ()
361	\|\| gid != getegid ())
362	ptytty_fatal ("unable to drop privileges, aborting.\n");
363	}
364