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, 7 months ago) by root
Content type:	text/plain
Branch:	MAIN
Changes since 1.13:	+0 -3 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	/----------------------------------------------------------------------
2			* File: proxy.C
3			----------------------------------------------------------------------
4			*
5			* All portions of code are copyright by their respective author/s.
6	sf-exg	1.9	* Copyright (c) 2006 Marc Lehmann <schmorp@schmorp.de>
7	root	1.1	*
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	sf-exg	1.8	#include "config.h"
24	root	1.1
25			#include "ptytty.h"
26
27	sf-exg	1.13	#if !PTYTTY_NO_LIBCPP
28			#include <vector>
29			#include <algorithm>
30			using namespace std;
31			#endif
32
33	root	1.7	#include <cstdio>
34			#include <cstring>
35	root	1.1	#include <csignal>
36
37			#include <sys/types.h>
38			#include <sys/socket.h>
39			#include <unistd.h>
40			#include <fcntl.h>
41	root	1.4	#include <errno.h>
42	root	1.1
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	root	1.11	# define NEED_TOKEN read (lock_fd, &lock_fd, 1)
78			# define GIVE_TOKEN write (lock_fd, &lock_fd, 1)
79	root	1.1	#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	sf-exg	1.10	PTYTTY_FATAL ("protocol error while creating pty using helper process, aborting.\n");
97	root	1.1
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	sf-exg	1.10	PTYTTY_FATAL ("protocol error while reading pty/tty fds from helper process, aborting.\n");
107	root	1.1
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	ayin	1.3	close_tty ();
135
136			if (pty >= 0)
137			close (pty);
138	ayin	1.2
139	root	1.1	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	sf-exg	1.10	PTYTTY_FATAL ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
238	root	1.1
239	sf-exg	1.12	#if PTYTTY_REENTRANT
240	root	1.1	int lv[2];
241
242			if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
243	sf-exg	1.10	PTYTTY_FATAL ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
244	root	1.1	#endif
245
246			helper_pid = fork ();
247
248			if (helper_pid < 0)
249	sf-exg	1.10	PTYTTY_FATAL ("could not create pty/sessiondb helper process, aborting.\n");
250	root	1.1
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	sf-exg	1.12	#if PTYTTY_REENTRANT
258	root	1.1	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	sf-exg	1.12	#if PTYTTY_REENTRANT
268	root	1.1	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	root	1.4	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	root	1.5	fd2 = open ("/dev/null", fd ? O_WRONLY : O_RDONLY);
316	root	1.4
317			if (fd2 != fd)
318	root	1.5	abort ();
319	root	1.4	}
320			}
321
322			void
323	root	1.1	ptytty::init ()
324			{
325	root	1.4	sanitise_stdfd ();
326
327	root	1.1	uid_t uid = getuid ();
328			gid_t gid = getgid ();
329	ayin	1.6
330	root	1.1	// 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	sf-exg	1.10	PTYTTY_WARN ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n", 0);
339	root	1.1	#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	sf-exg	1.10	PTYTTY_FATAL ("unable to drop privileges, aborting.\n");
368	root	1.1	}
369