libptytty/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 <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:	1.13
Committed:	Tue Dec 20 13:46:05 2011 UTC (14 years, 8 months ago) by sf-exg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rel-9_14, rel-1_5
Changes since 1.12:	+6 -0 lines
Log Message:	change the semantic of PTYTTY_NO_LIBCPP from undef/def to 0/1 and move the associated includes in proxy.C.
#	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 <schmorp@schmorp.de>
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	#if !PTYTTY_NO_LIBCPP
31	#include <vector>
32	#include <algorithm>
33	using namespace std;
34	#endif
35
36	#include <cstdio>
37	#include <cstring>
38	#include <csignal>
39
40	#include <sys/types.h>
41	#include <sys/socket.h>
42	#include <unistd.h>
43	#include <fcntl.h>
44	#include <errno.h>
45
46	// helper/proxy support
47
48	#if PTYTTY_HELPER
49
50	static int sock_fd = -1, lock_fd = -1;
51	static int helper_pid, owner_pid;
52
53	struct command
54	{
55	enum { get, login, destroy } type;
56
57	ptytty *id;
58
59	bool login_shell;
60	int cmd_pid;
61	char hostname[512]; // arbitrary, but should be plenty
62	};
63
64	struct ptytty_proxy : ptytty
65	{
66	ptytty *id;
67
68	ptytty_proxy ()
69	: id(0)
70	{
71	}
72
73	~ptytty_proxy ();
74
75	bool get ();
76	void login (int cmd_pid, bool login_shell, const char *hostname);
77	};
78
79	#if PTYTTY_REENTRANT
80	# define NEED_TOKEN read (lock_fd, &lock_fd, 1)
81	# define GIVE_TOKEN write (lock_fd, &lock_fd, 1)
82	#else
83	# define NEED_TOKEN (void)0
84	# define GIVE_TOKEN (void)0
85	#endif
86
87	bool
88	ptytty_proxy::get ()
89	{
90	NEED_TOKEN;
91
92	command cmd;
93
94	cmd.type = command::get;
95
96	write (sock_fd, &cmd, sizeof (cmd));
97
98	if (read (sock_fd, &id, sizeof (id)) != sizeof (id))
99	PTYTTY_FATAL ("protocol error while creating pty using helper process, aborting.\n");
100
101	if (!id)
102	{
103	GIVE_TOKEN;
104	return false;
105	}
106
107	if ((pty = recv_fd (sock_fd)) < 0
108	\|\| (tty = recv_fd (sock_fd)) < 0)
109	PTYTTY_FATAL ("protocol error while reading pty/tty fds from helper process, aborting.\n");
110
111	GIVE_TOKEN;
112	return true;
113	}
114
115	void
116	ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname)
117	{
118	NEED_TOKEN;
119
120	command cmd;
121
122	cmd.type = command::login;
123	cmd.id = id;
124	cmd.cmd_pid = cmd_pid;
125	cmd.login_shell = login_shell;
126	strncpy (cmd.hostname, hostname, sizeof (cmd.hostname));
127
128	write (sock_fd, &cmd, sizeof (cmd));
129
130	GIVE_TOKEN;
131	}
132
133	ptytty_proxy::~ptytty_proxy ()
134	{
135	if (id)
136	{
137	close_tty ();
138
139	if (pty >= 0)
140	close (pty);
141
142	NEED_TOKEN;
143
144	command cmd;
145
146	cmd.type = command::destroy;
147	cmd.id = id;
148
149	write (sock_fd, &cmd, sizeof (cmd));
150
151	GIVE_TOKEN;
152	}
153	}
154
155	static
156	void serve ()
157	{
158	command cmd;
159	vector<ptytty *> ptys;
160
161	for (;;)
162	{
163	GIVE_TOKEN;
164
165	if (read (sock_fd, &cmd, sizeof (command)) != sizeof (command))
166	break;
167
168	if (cmd.type == command::get)
169	{
170	// -> id ptyfd ttyfd
171	cmd.id = new ptytty_unix;
172
173	if (cmd.id->get ())
174	{
175	write (sock_fd, &cmd.id, sizeof (cmd.id));
176	ptys.push_back (cmd.id);
177
178	ptytty::send_fd (sock_fd, cmd.id->pty);
179	ptytty::send_fd (sock_fd, cmd.id->tty);
180	}
181	else
182	{
183	delete cmd.id;
184	cmd.id = 0;
185	write (sock_fd, &cmd.id, sizeof (cmd.id));
186	}
187	}
188	else if (cmd.type == command::login)
189	{
190	#if UTMP_SUPPORT
191	if (find (ptys.begin (), ptys.end (), cmd.id) != ptys.end ())
192	{
193	cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
194	cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
195	}
196	#endif
197	}
198	else if (cmd.type == command::destroy)
199	{
200	vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);
201
202	if (pty != ptys.end ())
203	{
204	delete *pty;
205	ptys.erase (pty);
206	}
207	}
208	else
209	break;
210
211	NEED_TOKEN;
212	}
213
214	// destroy all ptys
215	for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
216	delete *i;
217	}
218
219	void
220	ptytty::use_helper ()
221	{
222	#ifndef PTYTTY_NO_PID_CHECK
223	int pid = getpid ();
224	#endif
225
226	if (sock_fd >= 0
227	#ifndef PTYTTY_NO_PID_CHECK
228	&& pid == owner_pid
229	#endif
230	)
231	return;
232
233	#ifndef PTYTTY_NO_PID_CHECK
234	owner_pid = pid;
235	#endif
236
237	int sv[2];
238
239	if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
240	PTYTTY_FATAL ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
241
242	#if PTYTTY_REENTRANT
243	int lv[2];
244
245	if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
246	PTYTTY_FATAL ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
247	#endif
248
249	helper_pid = fork ();
250
251	if (helper_pid < 0)
252	PTYTTY_FATAL ("could not create pty/sessiondb helper process, aborting.\n");
253
254	if (helper_pid)
255	{
256	// client, process
257	sock_fd = sv[0];
258	close (sv[1]);
259	fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
260	#if PTYTTY_REENTRANT
261	lock_fd = lv[0];
262	close (lv[1]);
263	fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
264	#endif
265	}
266	else
267	{
268	// server, pty-helper
269	sock_fd = sv[1];
270	#if PTYTTY_REENTRANT
271	lock_fd = lv[1];
272	#endif
273
274	chdir ("/");
275
276	signal (SIGHUP, SIG_IGN);
277	signal (SIGTERM, SIG_IGN);
278	signal (SIGINT, SIG_IGN);
279	signal (SIGPIPE, SIG_IGN);
280
281	for (int fd = 0; fd < 1023; fd++)
282	if (fd != sock_fd && fd != lock_fd)
283	close (fd);
284
285	serve ();
286	_exit (EXIT_SUCCESS);
287	}
288	}
289
290	#endif
291
292	ptytty *
293	ptytty::create ()
294	{
295	#if PTYTTY_HELPER
296	if (helper_pid
297	# ifndef PTYTTY_NO_PID_CHECK
298	&& getpid () == owner_pid
299	# endif
300	)
301	// use helper process
302	return new ptytty_proxy;
303	else
304	#endif
305	return new ptytty_unix;
306	}
307
308	void
309	ptytty::sanitise_stdfd ()
310	{
311	// sanitise stdin/stdout/stderr to point to something.
312	for (int fd = 0; fd <= 2; ++fd)
313	if (fcntl (fd, F_GETFL) < 0 && errno == EBADF)
314	{
315	int fd2 = open ("/dev/tty", fd ? O_WRONLY : O_RDONLY);
316
317	if (fd2 < 0)
318	fd2 = open ("/dev/null", fd ? O_WRONLY : O_RDONLY);
319
320	if (fd2 != fd)
321	abort ();
322	}
323	}
324
325	void
326	ptytty::init ()
327	{
328	sanitise_stdfd ();
329
330	uid_t uid = getuid ();
331	gid_t gid = getgid ();
332
333	// before doing anything else, check for setuid/setgid operation,
334	// start the helper process and drop privileges
335	if (uid != geteuid ()
336	\|\| gid != getegid ())
337	{
338	#if PTYTTY_HELPER
339	use_helper ();
340	#else
341	PTYTTY_WARN ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n", 0);
342	#endif
343
344	drop_privileges ();
345	}
346	}
347
348	void
349	ptytty::drop_privileges ()
350	{
351	uid_t uid = getuid ();
352	gid_t gid = getgid ();
353
354	// drop privileges
355	#if HAVE_SETRESUID
356	setresgid (gid, gid, gid);
357	setresuid (uid, uid, uid);
358	#elif HAVE_SETREUID
359	setregid (gid, gid);
360	setreuid (uid, uid);
361	#elif HAVE_SETUID
362	setgid (gid);
363	setuid (uid);
364	#else
365	# error no way to drop privileges, configure failed?
366	#endif
367
368	if (uid != geteuid ()
369	\|\| gid != getegid ())
370	PTYTTY_FATAL ("unable to drop privileges, aborting.\n");
371	}
372