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.
#	User	Rev	Content
1	root	1.1	// 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	sf-exg	1.9	* Copyright (c) 2006 Marc Lehmann <schmorp@schmorp.de>
10	root	1.1	*
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	sf-exg	1.8	#include "config.h"
27	root	1.1
28			#include "ptytty.h"
29
30	sf-exg	1.13	#if !PTYTTY_NO_LIBCPP
31			#include <vector>
32			#include <algorithm>
33			using namespace std;
34			#endif
35
36	root	1.7	#include <cstdio>
37			#include <cstring>
38	root	1.1	#include <csignal>
39
40			#include <sys/types.h>
41			#include <sys/socket.h>
42			#include <unistd.h>
43			#include <fcntl.h>
44	root	1.4	#include <errno.h>
45	root	1.1
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	root	1.11	# define NEED_TOKEN read (lock_fd, &lock_fd, 1)
81			# define GIVE_TOKEN write (lock_fd, &lock_fd, 1)
82	root	1.1	#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	sf-exg	1.10	PTYTTY_FATAL ("protocol error while creating pty using helper process, aborting.\n");
100	root	1.1
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	sf-exg	1.10	PTYTTY_FATAL ("protocol error while reading pty/tty fds from helper process, aborting.\n");
110	root	1.1
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	ayin	1.3	close_tty ();
138
139			if (pty >= 0)
140			close (pty);
141	ayin	1.2
142	root	1.1	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	sf-exg	1.10	PTYTTY_FATAL ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
241	root	1.1
242	sf-exg	1.12	#if PTYTTY_REENTRANT
243	root	1.1	int lv[2];
244
245			if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
246	sf-exg	1.10	PTYTTY_FATAL ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
247	root	1.1	#endif
248
249			helper_pid = fork ();
250
251			if (helper_pid < 0)
252	sf-exg	1.10	PTYTTY_FATAL ("could not create pty/sessiondb helper process, aborting.\n");
253	root	1.1
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	sf-exg	1.12	#if PTYTTY_REENTRANT
261	root	1.1	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	sf-exg	1.12	#if PTYTTY_REENTRANT
271	root	1.1	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	root	1.4	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	root	1.5	fd2 = open ("/dev/null", fd ? O_WRONLY : O_RDONLY);
319	root	1.4
320			if (fd2 != fd)
321	root	1.5	abort ();
322	root	1.4	}
323			}
324
325			void
326	root	1.1	ptytty::init ()
327			{
328	root	1.4	sanitise_stdfd ();
329
330	root	1.1	uid_t uid = getuid ();
331			gid_t gid = getgid ();
332	ayin	1.6
333	root	1.1	// 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	sf-exg	1.10	PTYTTY_WARN ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n", 0);
342	root	1.1	#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	sf-exg	1.10	PTYTTY_FATAL ("unable to drop privileges, aborting.\n");
371	root	1.1	}
372