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/*----------------------------------------------------------------------* |
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* File: proxy.C |
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*----------------------------------------------------------------------* |
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* |
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* All portions of code are copyright by their respective author/s. |
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* Copyright (c) 2006 Marc Lehmann <schmorp@schmorp.de> |
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* |
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* This program is free software; you can redistribute it and/or modify |
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* it under the terms of the GNU General Public License as published by |
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* the Free Software Foundation; either version 2 of the License, or |
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* (at your option) any later version. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU General Public License for more details. |
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* |
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* You should have received a copy of the GNU General Public License |
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* along with this program; if not, write to the Free Software |
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
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*---------------------------------------------------------------------*/ |
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|
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#include "config.h" |
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|
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#include "ptytty.h" |
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|
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#include "estl.h" |
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|
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#include <stdio.h> |
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#include <string.h> |
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#include <signal.h> |
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|
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#include <sys/types.h> |
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#include <sys/socket.h> |
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#include <unistd.h> |
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#include <fcntl.h> |
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#include <errno.h> |
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|
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// helper/proxy support |
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|
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#if PTYTTY_HELPER |
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|
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static int sock_fd = -1, lock_fd = -1; |
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static int helper_pid; |
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|
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struct command |
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{ |
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enum { get, login, destroy } type; |
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|
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ptytty *id; |
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|
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bool login_shell; |
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int cmd_pid; |
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char hostname[512]; // arbitrary, but should be plenty |
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}; |
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|
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struct ptytty_proxy : ptytty |
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{ |
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private: |
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|
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ptytty *id; |
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|
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public: |
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|
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ptytty_proxy () |
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: id(0) |
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{ |
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} |
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|
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~ptytty_proxy (); |
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|
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bool get (); |
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void login (int cmd_pid, bool login_shell, const char *hostname); |
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}; |
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|
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#if PTYTTY_REENTRANT |
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# define NEED_TOKEN do { char ch; read (lock_fd, &ch , 1); } while (0) |
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# define GIVE_TOKEN write (lock_fd, &lock_fd, 1) |
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#else |
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# define NEED_TOKEN (void)0 |
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# define GIVE_TOKEN (void)0 |
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#endif |
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|
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bool |
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ptytty_proxy::get () |
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{ |
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NEED_TOKEN; |
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|
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command cmd; |
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|
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cmd.type = command::get; |
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|
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write (sock_fd, &cmd, sizeof (cmd)); |
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|
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if (read (sock_fd, &id, sizeof (id)) != sizeof (id)) |
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throw ptytty_error ("protocol error while creating pty using helper process.\n"); |
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|
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if (!id) |
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{ |
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GIVE_TOKEN; |
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return false; |
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} |
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|
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if ((pty = recv_fd (sock_fd)) < 0 |
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|| (tty = recv_fd (sock_fd)) < 0) |
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throw ptytty_error ("protocol error while reading pty/tty fds from helper process.\n"); |
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|
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GIVE_TOKEN; |
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return true; |
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} |
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|
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void |
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ptytty_proxy::login (int cmd_pid, bool login_shell, const char *hostname) |
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{ |
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NEED_TOKEN; |
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|
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command cmd; |
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|
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cmd.type = command::login; |
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cmd.id = id; |
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cmd.cmd_pid = cmd_pid; |
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cmd.login_shell = login_shell; |
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strncpy (cmd.hostname, hostname, sizeof (cmd.hostname)); |
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|
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write (sock_fd, &cmd, sizeof (cmd)); |
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|
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GIVE_TOKEN; |
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} |
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|
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ptytty_proxy::~ptytty_proxy () |
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{ |
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if (id) |
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{ |
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close_tty (); |
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|
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if (pty >= 0) |
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close (pty); |
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|
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NEED_TOKEN; |
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|
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command cmd; |
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|
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cmd.type = command::destroy; |
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cmd.id = id; |
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|
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write (sock_fd, &cmd, sizeof (cmd)); |
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|
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GIVE_TOKEN; |
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} |
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} |
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|
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static void |
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serve () |
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{ |
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command cmd; |
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vector<ptytty *> ptys; |
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|
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for (;;) |
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{ |
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GIVE_TOKEN; |
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|
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if (read (sock_fd, &cmd, sizeof (command)) != sizeof (command)) |
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break; |
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|
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if (cmd.type == command::get) |
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{ |
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// -> id ptyfd ttyfd |
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cmd.id = new ptytty_unix; |
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|
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if (cmd.id->get ()) |
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{ |
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write (sock_fd, &cmd.id, sizeof (cmd.id)); |
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ptys.push_back (cmd.id); |
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|
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ptytty::send_fd (sock_fd, cmd.id->pty); |
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ptytty::send_fd (sock_fd, cmd.id->tty); |
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|
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cmd.id->close_tty (); |
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} |
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else |
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{ |
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delete cmd.id; |
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cmd.id = 0; |
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write (sock_fd, &cmd.id, sizeof (cmd.id)); |
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} |
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} |
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else if (cmd.type == command::login) |
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{ |
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#if UTMP_SUPPORT |
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if (find (ptys.begin (), ptys.end (), cmd.id) != ptys.end ()) |
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{ |
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cmd.hostname[sizeof (cmd.hostname) - 1] = 0; |
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cmd.id->login (cmd.cmd_pid, cmd.login_shell, cmd.hostname); |
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} |
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#endif |
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} |
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else if (cmd.type == command::destroy) |
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{ |
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vector<ptytty *>::iterator pty = find (ptys.begin (), ptys.end (), cmd.id); |
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|
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if (pty != ptys.end ()) |
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{ |
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delete *pty; |
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ptys.erase (pty); |
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} |
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} |
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else |
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break; |
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|
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NEED_TOKEN; |
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} |
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|
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// destroy all ptys |
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for (vector<ptytty *>::iterator i = ptys.end (); i-- > ptys.begin (); ) |
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delete *i; |
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} |
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|
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void |
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ptytty::use_helper () |
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{ |
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if (sock_fd >= 0) |
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return; |
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|
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int sv[2]; |
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|
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if (socketpair (AF_UNIX, SOCK_STREAM, 0, sv)) |
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throw ptytty_error ("could not create socket to communicate with pty/sessiondb helper.\n"); |
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|
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#if PTYTTY_REENTRANT |
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int lv[2]; |
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|
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if (socketpair (AF_UNIX, SOCK_STREAM, 0, lv)) |
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throw ptytty_error ("could not create socket to communicate with pty/sessiondb helper.\n"); |
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#endif |
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|
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helper_pid = fork (); |
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|
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if (helper_pid < 0) |
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throw ptytty_error ("could not create pty/sessiondb helper process.\n"); |
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|
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if (helper_pid) |
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{ |
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// client, process |
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sock_fd = sv[0]; |
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close (sv[1]); |
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fcntl (sock_fd, F_SETFD, FD_CLOEXEC); |
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#if PTYTTY_REENTRANT |
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lock_fd = lv[0]; |
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close (lv[1]); |
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fcntl (lock_fd, F_SETFD, FD_CLOEXEC); |
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#endif |
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} |
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else |
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{ |
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// server, pty-helper |
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sock_fd = sv[1]; |
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#if PTYTTY_REENTRANT |
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lock_fd = lv[1]; |
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#endif |
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|
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chdir ("/"); |
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|
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signal (SIGHUP, SIG_IGN); |
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signal (SIGTERM, SIG_IGN); |
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signal (SIGINT, SIG_IGN); |
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signal (SIGPIPE, SIG_IGN); |
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|
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for (int fd = 0; fd < 1023; fd++) |
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if (fd != sock_fd && fd != lock_fd) |
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close (fd); |
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|
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serve (); |
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_exit (EXIT_SUCCESS); |
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} |
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} |
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|
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#endif |
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|
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ptytty * |
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ptytty::create () |
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{ |
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#if PTYTTY_HELPER |
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if (helper_pid) |
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// use helper process |
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return new ptytty_proxy; |
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else |
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#endif |
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return new ptytty_unix; |
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} |
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|
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void |
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ptytty::sanitise_stdfd () |
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{ |
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// sanitise stdin/stdout/stderr to point to *something*. |
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for (int fd = 0; fd <= 2; ++fd) |
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if (fcntl (fd, F_GETFL) < 0 && errno == EBADF) |
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{ |
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int fd2 = open ("/dev/tty", fd ? O_WRONLY : O_RDONLY); |
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|
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if (fd2 < 0) |
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fd2 = open ("/dev/null", fd ? O_WRONLY : O_RDONLY); |
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|
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if (fd2 != fd) |
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throw ptytty_error ("unable to sanitise fds.\n"); |
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} |
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} |
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|
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void |
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ptytty::init () |
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{ |
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sanitise_stdfd (); |
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|
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uid_t uid = getuid (); |
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gid_t gid = getgid (); |
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|
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// before doing anything else, check for setuid/setgid operation, |
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// start the helper process and drop privileges |
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if (uid != geteuid () |
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|| gid != getegid ()) |
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{ |
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#if PTYTTY_HELPER |
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use_helper (); |
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#endif |
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|
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drop_privileges (); |
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} |
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} |
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|
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void |
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ptytty::drop_privileges () |
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{ |
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uid_t uid = getuid (); |
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gid_t gid = getgid (); |
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|
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// drop privileges |
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#if HAVE_SETRESUID |
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setresgid (gid, gid, gid); |
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setresuid (uid, uid, uid); |
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#elif HAVE_SETREUID |
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setregid (gid, gid); |
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setreuid (uid, uid); |
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#elif HAVE_SETUID |
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setgid (gid); |
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setuid (uid); |
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#else |
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# error no way to drop privileges, configure failed? |
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#endif |
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|
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if (uid != geteuid () |
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|| gid != getegid ()) |
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throw ptytty_error ("unable to drop privileges.\n"); |
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} |
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|
