libptytty/src/proxy.C

/*----------------------------------------------------------------------*
 * File:        proxy.C
 *----------------------------------------------------------------------*
 *
 * All portions of code are copyright by their respective author/s.
 * Copyright (c) 2006      Marc Lehmann <schmorp@schmorp.de>
 *
 * 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"

#if !PTYTTY_NO_LIBCPP
#include <vector>
#include <algorithm>
using namespace std;
#endif

#include <cstdio>
#include <cstring>
#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 read  (lock_fd, &lock_fd, 1)
# define GIVE_TOKEN write (lock_fd, &lock_fd, 1)
#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");

#if 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);
#if 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];
#if 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:	1.14
Committed:	Wed Jan 18 12:19:31 2012 UTC (14 years, 9 months ago) by root
Content type:	text/plain
Branch:	MAIN
Changes since 1.13:	+0 -3 lines
Log Message:	* empty log message *
#	Content
1	/----------------------------------------------------------------------
2	* File: proxy.C
3	----------------------------------------------------------------------
4	*
5	* All portions of code are copyright by their respective author/s.
6	* Copyright (c) 2006 Marc Lehmann <schmorp@schmorp.de>
7	*
8	* This program is free software; you can redistribute it and/or modify
9	* it under the terms of the GNU General Public License as published by
10	* the Free Software Foundation; either version 2 of the License, or
11	* (at your option) any later version.
12	*
13	* This program is distributed in the hope that it will be useful,
14	* but WITHOUT ANY WARRANTY; without even the implied warranty of
15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16	* GNU General Public License for more details.
17	*
18	* You should have received a copy of the GNU General Public License
19	* along with this program; if not, write to the Free Software
20	* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21	---------------------------------------------------------------------/
22
23	#include "config.h"
24
25	#include "ptytty.h"
26
27	#if !PTYTTY_NO_LIBCPP
28	#include <vector>
29	#include <algorithm>
30	using namespace std;
31	#endif
32
33	#include <cstdio>
34	#include <cstring>
35	#include <csignal>
36
37	#include <sys/types.h>
38	#include <sys/socket.h>
39	#include <unistd.h>
40	#include <fcntl.h>
41	#include <errno.h>
42
43	// helper/proxy support
44
45	#if PTYTTY_HELPER
46
47	static int sock_fd = -1, lock_fd = -1;
48	static int helper_pid, owner_pid;
49
50	struct command
51	{
52	enum { get, login, destroy } type;
53
54	ptytty *id;
55
56	bool login_shell;
57	int cmd_pid;
58	char hostname[512]; // arbitrary, but should be plenty
59	};
60
61	struct ptytty_proxy : ptytty
62	{
63	ptytty *id;
64
65	ptytty_proxy ()
66	: id(0)
67	{
68	}
69
70	~ptytty_proxy ();
71
72	bool get ();
73	void login (int cmd_pid, bool login_shell, const char *hostname);
74	};
75
76	#if PTYTTY_REENTRANT
77	# define NEED_TOKEN read (lock_fd, &lock_fd, 1)
78	# define GIVE_TOKEN write (lock_fd, &lock_fd, 1)
79	#else
80	# define NEED_TOKEN (void)0
81	# define GIVE_TOKEN (void)0
82	#endif
83
84	bool
85	ptytty_proxy::get ()
86	{
87	NEED_TOKEN;
88
89	command cmd;
90
91	cmd.type = command::get;
92
93	write (sock_fd, &cmd, sizeof (cmd));
94
95	if (read (sock_fd, &id, sizeof (id)) != sizeof (id))
96	PTYTTY_FATAL ("protocol error while creating pty using helper process, aborting.\n");
97
98	if (!id)
99	{
100	GIVE_TOKEN;
101	return false;
102	}
103
104	if ((pty = recv_fd (sock_fd)) < 0
105	\|\| (tty = recv_fd (sock_fd)) < 0)
106	PTYTTY_FATAL ("protocol error while reading pty/tty fds from helper process, aborting.\n");
107
108	GIVE_TOKEN;
109	return true;
110	}
111
112	void
113	ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname)
114	{
115	NEED_TOKEN;
116
117	command cmd;
118
119	cmd.type = command::login;
120	cmd.id = id;
121	cmd.cmd_pid = cmd_pid;
122	cmd.login_shell = login_shell;
123	strncpy (cmd.hostname, hostname, sizeof (cmd.hostname));
124
125	write (sock_fd, &cmd, sizeof (cmd));
126
127	GIVE_TOKEN;
128	}
129
130	ptytty_proxy::~ptytty_proxy ()
131	{
132	if (id)
133	{
134	close_tty ();
135
136	if (pty >= 0)
137	close (pty);
138
139	NEED_TOKEN;
140
141	command cmd;
142
143	cmd.type = command::destroy;
144	cmd.id = id;
145
146	write (sock_fd, &cmd, sizeof (cmd));
147
148	GIVE_TOKEN;
149	}
150	}
151
152	static
153	void serve ()
154	{
155	command cmd;
156	vector<ptytty *> ptys;
157
158	for (;;)
159	{
160	GIVE_TOKEN;
161
162	if (read (sock_fd, &cmd, sizeof (command)) != sizeof (command))
163	break;
164
165	if (cmd.type == command::get)
166	{
167	// -> id ptyfd ttyfd
168	cmd.id = new ptytty_unix;
169
170	if (cmd.id->get ())
171	{
172	write (sock_fd, &cmd.id, sizeof (cmd.id));
173	ptys.push_back (cmd.id);
174
175	ptytty::send_fd (sock_fd, cmd.id->pty);
176	ptytty::send_fd (sock_fd, cmd.id->tty);
177	}
178	else
179	{
180	delete cmd.id;
181	cmd.id = 0;
182	write (sock_fd, &cmd.id, sizeof (cmd.id));
183	}
184	}
185	else if (cmd.type == command::login)
186	{
187	#if UTMP_SUPPORT
188	if (find (ptys.begin (), ptys.end (), cmd.id) != ptys.end ())
189	{
190	cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
191	cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
192	}
193	#endif
194	}
195	else if (cmd.type == command::destroy)
196	{
197	vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);
198
199	if (pty != ptys.end ())
200	{
201	delete *pty;
202	ptys.erase (pty);
203	}
204	}
205	else
206	break;
207
208	NEED_TOKEN;
209	}
210
211	// destroy all ptys
212	for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
213	delete *i;
214	}
215
216	void
217	ptytty::use_helper ()
218	{
219	#ifndef PTYTTY_NO_PID_CHECK
220	int pid = getpid ();
221	#endif
222
223	if (sock_fd >= 0
224	#ifndef PTYTTY_NO_PID_CHECK
225	&& pid == owner_pid
226	#endif
227	)
228	return;
229
230	#ifndef PTYTTY_NO_PID_CHECK
231	owner_pid = pid;
232	#endif
233
234	int sv[2];
235
236	if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
237	PTYTTY_FATAL ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
238
239	#if PTYTTY_REENTRANT
240	int lv[2];
241
242	if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
243	PTYTTY_FATAL ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
244	#endif
245
246	helper_pid = fork ();
247
248	if (helper_pid < 0)
249	PTYTTY_FATAL ("could not create pty/sessiondb helper process, aborting.\n");
250
251	if (helper_pid)
252	{
253	// client, process
254	sock_fd = sv[0];
255	close (sv[1]);
256	fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
257	#if PTYTTY_REENTRANT
258	lock_fd = lv[0];
259	close (lv[1]);
260	fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
261	#endif
262	}
263	else
264	{
265	// server, pty-helper
266	sock_fd = sv[1];
267	#if PTYTTY_REENTRANT
268	lock_fd = lv[1];
269	#endif
270
271	chdir ("/");
272
273	signal (SIGHUP, SIG_IGN);
274	signal (SIGTERM, SIG_IGN);
275	signal (SIGINT, SIG_IGN);
276	signal (SIGPIPE, SIG_IGN);
277
278	for (int fd = 0; fd < 1023; fd++)
279	if (fd != sock_fd && fd != lock_fd)
280	close (fd);
281
282	serve ();
283	_exit (EXIT_SUCCESS);
284	}
285	}
286
287	#endif
288
289	ptytty *
290	ptytty::create ()
291	{
292	#if PTYTTY_HELPER
293	if (helper_pid
294	# ifndef PTYTTY_NO_PID_CHECK
295	&& getpid () == owner_pid
296	# endif
297	)
298	// use helper process
299	return new ptytty_proxy;
300	else
301	#endif
302	return new ptytty_unix;
303	}
304
305	void
306	ptytty::sanitise_stdfd ()
307	{
308	// sanitise stdin/stdout/stderr to point to something.
309	for (int fd = 0; fd <= 2; ++fd)
310	if (fcntl (fd, F_GETFL) < 0 && errno == EBADF)
311	{
312	int fd2 = open ("/dev/tty", fd ? O_WRONLY : O_RDONLY);
313
314	if (fd2 < 0)
315	fd2 = open ("/dev/null", fd ? O_WRONLY : O_RDONLY);
316
317	if (fd2 != fd)
318	abort ();
319	}
320	}
321
322	void
323	ptytty::init ()
324	{
325	sanitise_stdfd ();
326
327	uid_t uid = getuid ();
328	gid_t gid = getgid ();
329
330	// before doing anything else, check for setuid/setgid operation,
331	// start the helper process and drop privileges
332	if (uid != geteuid ()
333	\|\| gid != getegid ())
334	{
335	#if PTYTTY_HELPER
336	use_helper ();
337	#else
338	PTYTTY_WARN ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n", 0);
339	#endif
340
341	drop_privileges ();
342	}
343	}
344
345	void
346	ptytty::drop_privileges ()
347	{
348	uid_t uid = getuid ();
349	gid_t gid = getgid ();
350
351	// drop privileges
352	#if HAVE_SETRESUID
353	setresgid (gid, gid, gid);
354	setresuid (uid, uid, uid);
355	#elif HAVE_SETREUID
356	setregid (gid, gid);
357	setreuid (uid, uid);
358	#elif HAVE_SETUID
359	setgid (gid);
360	setuid (uid);
361	#else
362	# error no way to drop privileges, configure failed?
363	#endif
364
365	if (uid != geteuid ()
366	\|\| gid != getegid ())
367	PTYTTY_FATAL ("unable to drop privileges, aborting.\n");
368	}
369