rxvt-unicode/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 <pcg@goof.com>
 *
 * 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 <csignal>

#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <fcntl.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 do { char ch; read  (lock_fd, &ch, 1); } while (0)
# define GIVE_TOKEN do { char ch; write (lock_fd, &ch, 1); } while (0)
#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 (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");

#ifdef 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);
#ifdef 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];
#ifdef 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::init ()
{
  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:	1.5
Committed:	Tue Jan 16 18:25:51 2007 UTC (17 years, 5 months ago) by ayin
Content type:	text/plain
Branch:	MAIN
Changes since 1.4:	+2 -0 lines
Log Message:	* empty log message *
#	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			* Copyright (c) 2006 Marc Lehmann <pcg@goof.com>
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			#include <csignal>
31
32			#include <sys/types.h>
33			#include <sys/socket.h>
34			#include <unistd.h>
35			#include <fcntl.h>
36
37	root	1.4	// helper/proxy support
38
39			#if PTYTTY_HELPER
40
41	root	1.1	static int sock_fd = -1, lock_fd = -1;
42			static int helper_pid, owner_pid;
43
44			struct command
45			{
46			enum { get, login, destroy } type;
47
48			ptytty *id;
49
50			bool login_shell;
51			int cmd_pid;
52			char hostname[512]; // arbitrary, but should be plenty
53			};
54
55			struct ptytty_proxy : ptytty
56			{
57			ptytty *id;
58
59			ptytty_proxy ()
60			: id(0)
61			{
62			}
63
64			~ptytty_proxy ();
65
66			bool get ();
67			void login (int cmd_pid, bool login_shell, const char *hostname);
68			};
69
70			#if PTYTTY_REENTRANT
71			# define NEED_TOKEN do { char ch; read (lock_fd, &ch, 1); } while (0)
72			# define GIVE_TOKEN do { char ch; write (lock_fd, &ch, 1); } while (0)
73			#else
74			# define NEED_TOKEN (void)0
75			# define GIVE_TOKEN (void)0
76			#endif
77
78			bool
79			ptytty_proxy::get ()
80			{
81			NEED_TOKEN;
82
83			command cmd;
84
85			cmd.type = command::get;
86
87			write (sock_fd, &cmd, sizeof (cmd));
88
89			if (read (sock_fd, &id, sizeof (id)) != sizeof (id))
90			ptytty_fatal ("protocol error while creating pty using helper process, aborting.\n");
91
92			if (!id)
93			{
94			GIVE_TOKEN;
95			return false;
96			}
97
98			if ((pty = recv_fd (sock_fd)) < 0
99			\|\| (tty = recv_fd (sock_fd)) < 0)
100			ptytty_fatal ("protocol error while reading pty/tty fds from helper process, aborting.\n");
101
102			GIVE_TOKEN;
103			return true;
104			}
105
106			void
107			ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname)
108			{
109			NEED_TOKEN;
110
111			command cmd;
112
113			cmd.type = command::login;
114			cmd.id = id;
115			cmd.cmd_pid = cmd_pid;
116			cmd.login_shell = login_shell;
117			strncpy (cmd.hostname, hostname, sizeof (cmd.hostname));
118
119			write (sock_fd, &cmd, sizeof (cmd));
120
121			GIVE_TOKEN;
122			}
123
124			ptytty_proxy::~ptytty_proxy ()
125			{
126			if (id)
127			{
128	ayin	1.5	close (pty);
129
130	root	1.1	NEED_TOKEN;
131
132			command cmd;
133
134			cmd.type = command::destroy;
135			cmd.id = id;
136
137			write (sock_fd, &cmd, sizeof (cmd));
138
139			GIVE_TOKEN;
140			}
141			}
142
143			static
144			void serve ()
145			{
146			command cmd;
147			vector<ptytty *> ptys;
148
149			for (;;)
150			{
151			GIVE_TOKEN;
152
153			if (read (sock_fd, &cmd, sizeof (command)) != sizeof (command))
154			break;
155
156			if (cmd.type == command::get)
157			{
158			// -> id ptyfd ttyfd
159			cmd.id = new ptytty_unix;
160
161			if (cmd.id->get ())
162			{
163			write (sock_fd, &cmd.id, sizeof (cmd.id));
164			ptys.push_back (cmd.id);
165
166			ptytty::send_fd (sock_fd, cmd.id->pty);
167			ptytty::send_fd (sock_fd, cmd.id->tty);
168			}
169			else
170			{
171			delete cmd.id;
172			cmd.id = 0;
173			write (sock_fd, &cmd.id, sizeof (cmd.id));
174			}
175			}
176			else if (cmd.type == command::login)
177			{
178			#if UTMP_SUPPORT
179			if (find (ptys.begin (), ptys.end (), cmd.id) != ptys.end ())
180			{
181			cmd.hostname[sizeof (cmd.hostname) - 1] = 0;
182			cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname);
183			}
184			#endif
185			}
186			else if (cmd.type == command::destroy)
187			{
188			vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id);
189
190			if (pty != ptys.end ())
191			{
192			delete *pty;
193			ptys.erase (pty);
194			}
195			}
196			else
197			break;
198
199			NEED_TOKEN;
200			}
201
202			// destroy all ptys
203			for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); )
204			delete *i;
205			}
206
207			void
208			ptytty::use_helper ()
209			{
210			#ifndef PTYTTY_NO_PID_CHECK
211			int pid = getpid ();
212			#endif
213
214			if (sock_fd >= 0
215			#ifndef PTYTTY_NO_PID_CHECK
216			&& pid == owner_pid
217			#endif
218			)
219			return;
220
221			#ifndef PTYTTY_NO_PID_CHECK
222			owner_pid = pid;
223			#endif
224
225			int sv[2];
226
227			if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv))
228			ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
229
230			#ifdef PTYTTY_REENTRANT
231			int lv[2];
232
233			if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv))
234			ptytty_fatal ("could not create socket to communicate with pty/sessiondb helper, aborting.\n");
235			#endif
236
237			helper_pid = fork ();
238
239			if (helper_pid < 0)
240			ptytty_fatal ("could not create pty/sessiondb helper process, aborting.\n");
241
242			if (helper_pid)
243			{
244			// client, process
245			sock_fd = sv[0];
246			close (sv[1]);
247			fcntl (sock_fd, F_SETFD, FD_CLOEXEC);
248			#ifdef PTYTTY_REENTRANT
249			lock_fd = lv[0];
250			close (lv[1]);
251			fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
252			#endif
253			}
254			else
255			{
256			// server, pty-helper
257			sock_fd = sv[1];
258			#ifdef PTYTTY_REENTRANT
259			lock_fd = lv[1];
260			#endif
261
262			chdir ("/");
263
264			signal (SIGHUP, SIG_IGN);
265			signal (SIGTERM, SIG_IGN);
266			signal (SIGINT, SIG_IGN);
267			signal (SIGPIPE, SIG_IGN);
268
269			for (int fd = 0; fd < 1023; fd++)
270			if (fd != sock_fd && fd != lock_fd)
271			close (fd);
272
273			serve ();
274			_exit (EXIT_SUCCESS);
275			}
276			}
277
278			#endif
279
280			ptytty *
281			ptytty::create ()
282			{
283			#if PTYTTY_HELPER
284			if (helper_pid
285			# ifndef PTYTTY_NO_PID_CHECK
286			&& getpid () == owner_pid
287			# endif
288			)
289			// use helper process
290			return new ptytty_proxy;
291			else
292			#endif
293			return new ptytty_unix;
294			}
295
296			void
297			ptytty::init ()
298			{
299			uid_t uid = getuid ();
300			gid_t gid = getgid ();
301
302			// before doing anything else, check for setuid/setgid operation,
303			// start the helper process and drop privileges
304			if (uid != geteuid ()
305			\|\| gid != getegid ())
306			{
307			#if PTYTTY_HELPER
308			use_helper ();
309			#else
310	root	1.2	ptytty_warn ("running setuid/setgid without pty helper compiled in, continuing unprivileged.\n", 0);
311	root	1.1	#endif
312
313			drop_privileges ();
314			}
315			}
316
317			void
318			ptytty::drop_privileges ()
319			{
320			uid_t uid = getuid ();
321			gid_t gid = getgid ();
322
323			// drop privileges
324			#if HAVE_SETRESUID
325			setresgid (gid, gid, gid);
326			setresuid (uid, uid, uid);
327			#elif HAVE_SETREUID
328			setregid (gid, gid);
329			setreuid (uid, uid);
330			#elif HAVE_SETUID
331			setgid (gid);
332			setuid (uid);
333	root	1.3	#else
334			# error no way to drop privileges, configure failed?
335	root	1.1	#endif
336
337			if (uid != geteuid ()
338			\|\| gid != getegid ())
339			ptytty_fatal ("unable to drop privileges, aborting.\n");
340			}
341