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"

#include "estl.h"

#include <stdio.h>
#include <string.h>
#include <signal.h>

#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;

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               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);

              cmd.id->close_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 ()
{
  if (sock_fd >= 0)
    return;

  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)
    // 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");
#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:	1.23
Committed:	Sat Nov 1 18:17:44 2014 UTC (11 years, 10 months ago) by root
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rxvt-unicode-rel-9_21, rel-1_7
Changes since 1.22:	+2 -2 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	#include "estl.h"
28
29	#include <stdio.h>
30	#include <string.h>
31	#include <signal.h>
32
33	#include <sys/types.h>
34	#include <sys/socket.h>
35	#include <unistd.h>
36	#include <fcntl.h>
37	#include <errno.h>
38
39	// helper/proxy support
40
41	#if PTYTTY_HELPER
42
43	static int sock_fd = -1, lock_fd = -1;
44	static int helper_pid;
45
46	struct command
47	{
48	enum { get, login, destroy } type;
49
50	ptytty *id;
51
52	bool login_shell;
53	int cmd_pid;
54	char hostname[512]; // arbitrary, but should be plenty
55	};
56
57	struct ptytty_proxy : ptytty
58	{
59	ptytty *id;
60
61	ptytty_proxy ()
62	: id(0)
63	{
64	}
65
66	~ptytty_proxy ();
67
68	bool get ();
69	void login (int cmd_pid, bool login_shell, const char *hostname);
70	};
71
72	#if PTYTTY_REENTRANT
73	# define NEED_TOKEN do { char ch; read (lock_fd, &ch , 1); } while (0)
74	# define GIVE_TOKEN write (lock_fd, &lock_fd, 1)
75	#else
76	# define NEED_TOKEN (void)0
77	# define GIVE_TOKEN (void)0
78	#endif
79
80	bool
81	ptytty_proxy::get ()
82	{
83	NEED_TOKEN;
84
85	command cmd;
86
87	cmd.type = command::get;
88
89	write (sock_fd, &cmd, sizeof (cmd));
90
91	if (read (sock_fd, &id, sizeof (id)) != sizeof (id))
92	PTYTTY_FATAL ("protocol error while creating pty using helper process, aborting.\n");
93
94	if (!id)
95	{
96	GIVE_TOKEN;
97	return false;
98	}
99
100	if ((pty = recv_fd (sock_fd)) < 0
101	\|\| (tty = recv_fd (sock_fd)) < 0)
102	PTYTTY_FATAL ("protocol error while reading pty/tty fds from helper process, aborting.\n");
103
104	GIVE_TOKEN;
105	return true;
106	}
107
108	void
109	ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname)
110	{
111	NEED_TOKEN;
112
113	command cmd;
114
115	cmd.type = command::login;
116	cmd.id = id;
117	cmd.cmd_pid = cmd_pid;
118	cmd.login_shell = login_shell;
119	strncpy (cmd.hostname, hostname, sizeof (cmd.hostname));
120
121	write (sock_fd, &cmd, sizeof (cmd));
122
123	GIVE_TOKEN;
124	}
125
126	ptytty_proxy::~ptytty_proxy ()
127	{
128	if (id)
129	{
130	close_tty ();
131
132	if (pty >= 0)
133	close (pty);
134
135	NEED_TOKEN;
136
137	command cmd;
138
139	cmd.type = command::destroy;
140	cmd.id = id;
141
142	write (sock_fd, &cmd, sizeof (cmd));
143
144	GIVE_TOKEN;
145	}
146	}
147
148	static
149	void serve ()
150	{
151	command cmd;
152	vector<ptytty *> ptys;
153
154	for (;;)
155	{
156	GIVE_TOKEN;
157
158	if (read (sock_fd, &cmd, sizeof (command)) != sizeof (command))
159	break;
160
161	if (cmd.type == command::get)
162	{
163	// -> id ptyfd ttyfd
164	cmd.id = new ptytty_unix;
165
166	if (cmd.id->get ())
167	{
168	write (sock_fd, &cmd.id, sizeof (cmd.id));
169	ptys.push_back (cmd.id);
170
171	ptytty::send_fd (sock_fd, cmd.id->pty);
172	ptytty::send_fd (sock_fd, cmd.id->tty);
173
174	cmd.id->close_tty ();
175	}
176	else
177	{
178	delete cmd.id;
179	cmd.id = 0;
180	write (sock_fd, &cmd.id, sizeof (cmd.id));
181	}
182	}
183	else if (cmd.type == command::login)
184	{
185	#if UTMP_SUPPORT
186	if (find (ptys.begin (), ptys.end (), cmd.id) != ptys.end ())
187	{
188	cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
189	cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
190	}
191	#endif
192	}
193	else if (cmd.type == command::destroy)
194	{
195	vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);
196
197	if (pty != ptys.end ())
198	{
199	delete *pty;
200	ptys.erase (pty);
201	}
202	}
203	else
204	break;
205
206	NEED_TOKEN;
207	}
208
209	// destroy all ptys
210	for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
211	delete *i;
212	}
213
214	void
215	ptytty::use_helper ()
216	{
217	if (sock_fd >= 0)
218	return;
219
220	int sv[2];
221
222	if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
223	PTYTTY_FATAL ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
224
225	#if PTYTTY_REENTRANT
226	int lv[2];
227
228	if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
229	PTYTTY_FATAL ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
230	#endif
231
232	helper_pid = fork ();
233
234	if (helper_pid < 0)
235	PTYTTY_FATAL ("could not create pty/sessiondb helper process, aborting.\n");
236
237	if (helper_pid)
238	{
239	// client, process
240	sock_fd = sv[0];
241	close (sv[1]);
242	fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
243	#if PTYTTY_REENTRANT
244	lock_fd = lv[0];
245	close (lv[1]);
246	fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
247	#endif
248	}
249	else
250	{
251	// server, pty-helper
252	sock_fd = sv[1];
253	#if PTYTTY_REENTRANT
254	lock_fd = lv[1];
255	#endif
256
257	chdir ("/");
258
259	signal (SIGHUP, SIG_IGN);
260	signal (SIGTERM, SIG_IGN);
261	signal (SIGINT, SIG_IGN);
262	signal (SIGPIPE, SIG_IGN);
263
264	for (int fd = 0; fd < 1023; fd++)
265	if (fd != sock_fd && fd != lock_fd)
266	close (fd);
267
268	serve ();
269	_exit (EXIT_SUCCESS);
270	}
271	}
272
273	#endif
274
275	ptytty *
276	ptytty::create ()
277	{
278	#if PTYTTY_HELPER
279	if (helper_pid)
280	// use helper process
281	return new ptytty_proxy;
282	else
283	#endif
284	return new ptytty_unix;
285	}
286
287	void
288	ptytty::sanitise_stdfd ()
289	{
290	// sanitise stdin/stdout/stderr to point to something.
291	for (int fd = 0; fd <= 2; ++fd)
292	if (fcntl (fd, F_GETFL) < 0 && errno == EBADF)
293	{
294	int fd2 = open ("/dev/tty", fd ? O_WRONLY : O_RDONLY);
295
296	if (fd2 < 0)
297	fd2 = open ("/dev/null", fd ? O_WRONLY : O_RDONLY);
298
299	if (fd2 != fd)
300	abort ();
301	}
302	}
303
304	void
305	ptytty::init ()
306	{
307	sanitise_stdfd ();
308
309	uid_t uid = getuid ();
310	gid_t gid = getgid ();
311
312	// before doing anything else, check for setuid/setgid operation,
313	// start the helper process and drop privileges
314	if (uid != geteuid ()
315	\|\| gid != getegid ())
316	{
317	#if PTYTTY_HELPER
318	use_helper ();
319	#else
320	PTYTTY_WARN ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n");
321	#endif
322
323	drop_privileges ();
324	}
325	}
326
327	void
328	ptytty::drop_privileges ()
329	{
330	uid_t uid = getuid ();
331	gid_t gid = getgid ();
332
333	// drop privileges
334	#if HAVE_SETRESUID
335	setresgid (gid, gid, gid);
336	setresuid (uid, uid, uid);
337	#elif HAVE_SETREUID
338	setregid (gid, gid);
339	setreuid (uid, uid);
340	#elif HAVE_SETUID
341	setgid (gid);
342	setuid (uid);
343	#else
344	# error no way to drop privileges, configure failed?
345	#endif
346
347	if (uid != geteuid ()
348	\|\| gid != getegid ())
349	PTYTTY_FATAL ("unable to drop privileges, aborting.\n");
350	}
351