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<head> |
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<title>libptytty - OS independent and secure pty/tty and utmp/wtmp/lastlog handling</title> |
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<link rev="made" href="mailto:perl-binary@plan9.de" /> |
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</head> |
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<body style="background-color: white"> |
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<p><a name="__index__"></a></p> |
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<!-- INDEX BEGIN --> |
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<ul> |
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|
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<li><a href="#name">NAME</a></li> |
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<li><a href="#synopsis">SYNOPSIS</a></li> |
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<li><a href="#description">DESCRIPTION</a></li> |
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<li><a href="#security_considerations">SECURITY CONSIDERATIONS</a></li> |
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<li><a href="#c___interface__the_ptytty_class">C++ INTERFACE: THE ptytty CLASS</a></li> |
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<ul> |
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|
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<li><a href="#static_methods">STATIC METHODS</a></li> |
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<li><a href="#dynamic_sessionrelated_data_members_and_methods">DYNAMIC/SESSION-RELATED DATA MEMBERS AND METHODS</a></li> |
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</ul> |
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|
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<li><a href="#c_interface__the_ptytty_family_of_functions">C INTERFACE: THE ptytty FAMILY OF FUNCTIONS</a></li> |
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<li><a href="#bugs">BUGS</a></li> |
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<li><a href="#authors">AUTHORS</a></li> |
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</ul> |
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<!-- INDEX END --> |
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<hr /> |
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<p> |
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</p> |
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<h1><a name="name">NAME</a></h1> |
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<p>libptytty - OS independent and secure pty/tty and utmp/wtmp/lastlog handling</p> |
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<p> |
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</p> |
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<hr /> |
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<h1><a name="synopsis">SYNOPSIS</a></h1> |
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<pre> |
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cc ... -lptytty</pre> |
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<pre> |
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#include <libptytty.h></pre> |
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<pre> |
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// C++ |
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ptytty *pty = ptytty::create ();</pre> |
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<pre> |
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if (!pty->get ()) |
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// error allocating pty</pre> |
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<pre> |
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if (we want utmp) |
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pty->login (process_pid, 0, "remote.host"); |
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else if (we want utmp AND wtmp/lastlog) |
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pty->login (process_pid, 1, "remote.host");</pre> |
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<pre> |
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// we are done with it |
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delete pty;</pre> |
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<pre> |
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// C |
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PTYTTY pty = ptytty_create ();</pre> |
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<pre> |
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if (!ptytty_get (pty)) |
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// error allocating pty</pre> |
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<pre> |
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if (we want utmp) |
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ptytty_login (pty, process_pid, 0, "remote.host"); |
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else if (we want utmp AND wtmp/lastlog) |
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ptytty_login (pty, process_pid, 1, "remote.host");</pre> |
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<pre> |
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// we are done with it |
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ptytty_delete (pty);</pre> |
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<p> |
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</p> |
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<hr /> |
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<h1><a name="description">DESCRIPTION</a></h1> |
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<p>Libptytty is a small library that offers pseudo-tty management in an |
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OS-independent way. It was created out of frustration over the many |
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differences of pty/tty handling in different operating systems for the use |
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inside <code>rxvt-unicode</code>.</p> |
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<p>In addition to offering mere pty/tty management, it also offers session |
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database support (utmp and optional wtmp/lastlog updates for login |
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shells).</p> |
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<p>It also supports fork'ing after startup and dropping privileges in the |
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calling process, so in case the calling process gets compromised by the |
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user starting the program there is less to gain, as only the helper |
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process runs with privileges (e.g. setuid/setgid), which reduces the area |
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of attack immensely.</p> |
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<p>Libptytty is written in C++, but it also offers a C-only API.</p> |
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<p> |
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</p> |
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<hr /> |
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<h1><a name="security_considerations">SECURITY CONSIDERATIONS</a></h1> |
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<p><em><strong>It is of paramount importance that you at least read the following |
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paragraph!</strong> </em>></p> |
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<p>If you are a typical terminal-like program that just wants one or more |
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ptys, you should call the <a href="#item_init"><code>ptytty::init ()</code></a> method (C: <a href="#item_ptytty_init"><code>ptytty_init ()</code></a> |
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function) as the very first thing in your program:</p> |
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<pre> |
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int main (int argc, char *argv[]) |
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{ |
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// do nothing here |
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ptytty::init (); |
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// in C: ptytty_init ();</pre> |
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<pre> |
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// initialise, parse arguments, etc. |
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}</pre> |
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<p>This checks wether the program runs setuid or setgid. If yes then it will |
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fork a helper process and drop privileges.</p> |
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<p>Some programs need finer control over if and when this helper process |
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is started, and if and how to drop privileges. For those programs, the |
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methods <code>ptytty::use_helper</code> and <code>ptytty::drop_privileges</code> are more |
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useful.</p> |
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<p> |
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</p> |
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<hr /> |
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<h1><a name="c___interface__the_ptytty_class">C++ INTERFACE: THE ptytty CLASS</a></h1> |
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<p> |
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</p> |
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<h2><a name="static_methods">STATIC METHODS</a></h2> |
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<dl> |
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<dt><strong><a name="item_init">ptytty::init ()</a></strong><br /> |
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</dt> |
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<dd> |
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The default way to initialise libptytty. Must be called imemdiately as |
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the first thing in the <code>main</code> function, or earlier e.g. during static |
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construction time. The earlier, the better. |
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</dd> |
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<dd> |
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<p>This method checks wether the program runs with setuid/setgid permissions |
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and, if yes, spawns a helper process for pty/tty management. IT then |
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drops the privileges completely, so the actual program runs without |
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setuid/setgid privileges.</p> |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_use_helper">ptytty::use_helper ()</a></strong><br /> |
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</dt> |
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<dd> |
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Tries to start a helper process that retains privileges even when the |
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calling process does not. This is usually called from <code>ptytty::init</code> when |
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it detects that the program is running setuid or setgid, but can be called |
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manually if it is inconvinient to drop privileges at startup, or when |
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you are not running setuid/setgid but want to drop privileges (e.g. when |
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running as a root-started daemon). |
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</dd> |
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<dd> |
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<p>This method will try not to start more than one helper process. The same |
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helper process cna usually be used form the process starting it an all its |
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fork'ed (not exec'ed) children</p> |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_drop_privileges">ptytty::drop_privileges ()</a></strong><br /> |
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</dt> |
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<dd> |
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Drops privileges completely, i.e. sets real, effective and saved user id |
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to the real user id. Also aborts if this cnanot be achieved. Useful to |
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make sure that the process doesn't run with special privileges. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_send_fd">bool success = ptytty::send_fd (int socket, int fd)</a></strong><br /> |
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</dt> |
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<dd> |
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Utility method to send a file descriptor over a unix domain |
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socket. Returns true if successful, false otherwise. This method is only |
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exposed for your convinience and is not required for normal operation. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_recv_fd">int fd = ptytty::recv_fd (int socket)</a></strong><br /> |
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</dt> |
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<dd> |
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Utility method to receive a file descriptor over a unix domain |
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socket. Returns the fd if sucecssful and <code>-1</code> otherwise. This method |
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is only exposed for your convinience and is not required for normal |
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operation. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_create">ptytty *pty = ptytty::create ()</a></strong><br /> |
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</dt> |
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<dd> |
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Creates new ptytty object. Creation does not yet do anything besides |
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allocating the structure. |
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</dd> |
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<dd> |
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<p>A static method is used because the actual ptytty implementation can |
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differ at runtime, so you need a dynamic object creation facility.</p> |
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</dd> |
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<p></p></dl> |
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<p> |
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</p> |
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<h2><a name="dynamic_sessionrelated_data_members_and_methods">DYNAMIC/SESSION-RELATED DATA MEMBERS AND METHODS</a></h2> |
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<dl> |
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<dt><strong><a name="item_pty">int pty_fd = pty->pty</a></strong><br /> |
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</dt> |
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<dt><strong><a name="item_tty">int tty_fd = pty->tty</a></strong><br /> |
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</dt> |
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<dd> |
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These members contain the pty and tty file descriptors, respectively. They |
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initially contain <code>-1</code> until a successful to <code>ptytty::get</code>. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_get">bool success = pty->get ()</a></strong><br /> |
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</dt> |
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<dd> |
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Tries to find, allocate and initialise a new pty/tty pair. Returns <code>true</code> |
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when successful. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_login">pty->login (int cmd_pid, bool login_shell, const char *hostname)</a></strong><br /> |
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</dt> |
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<dd> |
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Creates an entry in the systems session <code>database(s)</code> (utmp, wtmp, lastlog). |
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<code>cmd_pid</code> must be the pid of the process representing the session |
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(such as the login shell), <code>login_shell</code> defines wether the session is |
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associated with a login, which influences wether wtmp and lastlog entries |
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are created, and <code>hostname</code> should identify the ``hostname'' the user logs |
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in from, which often is the value of the <code>DISPLAY</code> variable or tty line |
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in case of local logins. |
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</dd> |
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<dd> |
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<p>Calling this method is optional. A session starts at the time of the login |
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call and extends until the ptytty object is destroyed.</p> |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_close_tty">pty->close_tty ()</a></strong><br /> |
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</dt> |
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<dd> |
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Closes the tty. Useful after forking in the parent/pty process. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_make_controlling_tty">bool success = pty->make_controlling_tty ()</a></strong><br /> |
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</dt> |
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<dd> |
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Tries to make the pty/tty pair the controlling terminal of the current |
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process. Useful after forking in the child/tty process. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_set_utf8_mode">pty->set_utf8_mode (bool on)</a></strong><br /> |
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</dt> |
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<dd> |
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On systems supporting special UTF-8 line disciplines (e.g. Linux), tries |
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to enable it for the given pty. Can be called at any time to change the |
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mode. |
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</dd> |
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<p></p></dl> |
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<p> |
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</p> |
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<hr /> |
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<h1><a name="c_interface__the_ptytty_family_of_functions">C INTERFACE: THE ptytty FAMILY OF FUNCTIONS</a></h1> |
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<dl> |
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<dt><strong><a name="item_ptytty_init">ptytty_init ()</a></strong><br /> |
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</dt> |
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<dd> |
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See <a href="#item_init"><code>ptytty::init ()</code></a>. |
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|
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</dd> |
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<dd> |
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<pre> |
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|
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=item PTYTTY ptytty_create ()</pre> |
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</dd> |
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<dd> |
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<p>Creates a new opaque PTYTTY object and returns it. Do not try to access it |
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in any way excecp by testing it for truthness (e.g. <code>if (pty) ....</code>). See |
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<a href="#item_create"><code>ptytty::create ()</code></a>.</p> |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_ptytty_pty">int ptytty_pty (PTYTTY ptytty)</a></strong><br /> |
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</dt> |
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<dd> |
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Return the pty file descriptor. See <a href="#item_pty"><code>pty->pty</code></a>. |
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|
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</dd> |
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<dd> |
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<pre> |
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|
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=item int ptytty_tty (PTYTTY ptytty)</pre> |
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</dd> |
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<dd> |
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<p>Return the tty file descriptor. See <a href="#item_tty"><code>pty->tty</code></a>. |
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</p> |
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</dd> |
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<dd> |
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<pre> |
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|
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=item void ptytty_delete (PTYTTY ptytty)</pre> |
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</dd> |
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<dd> |
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<p>Destroys the PTYTTY object, freeing the pty/tty pair and cleaning up the |
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utmp/wtmp/lastlog databases, if initialised/used. Same as <code>delete pty</code> in |
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C++.</p> |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_ptytty_get">int ptytty_get (PTYTTY ptytty)</a></strong><br /> |
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</dt> |
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<dd> |
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See <a href="#item_get"><code>pty->get</code></a>, returns 0 in case of an error, non-zero otherwise. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_ptytty_login">void ptytty_login (PTYTTY ptytty, int cmd_pid, bool login_shell, const char *hostname)</a></strong><br /> |
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</dt> |
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<dd> |
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See <a href="#item_login"><code>pty->login</code></a>. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_ptytty_close_tty">void ptytty_close_tty (PTYTTY ptytty)</a></strong><br /> |
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</dt> |
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<dd> |
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See <a href="#item_close_tty"><code>pty->close_tty</code></a>. |
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|
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</dd> |
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<dd> |
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<pre> |
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|
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=item int ptytty_make_controlling_tty (PTYTTY ptytty)</pre> |
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</dd> |
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<dd> |
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<p>See <a href="#item_make_controlling_tty"><code>pty->make_controlling_tty</code></a>. |
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</p> |
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</dd> |
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<dd> |
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<pre> |
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|
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=item void ptytty_set_utf8_mode (PTYTTY ptytty, int on)</pre> |
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</dd> |
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<dd> |
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<p>See <a href="#item_set_utf8_mode"><code>pty->set_utf8_mode</code></a>.</p> |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_ptytty_drop_privileges">void ptytty_drop_privileges ()</a></strong><br /> |
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</dt> |
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<dd> |
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See <code>ptytty::drop_privileges</code>. |
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|
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</dd> |
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<dd> |
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<pre> |
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|
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=item void ptytty_use_helper ()</pre> |
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</dd> |
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<dd> |
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<p>See <code>ptytty::use_helper</code>. |
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|
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</p> |
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</dd> |
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<p></p></dl> |
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<p> |
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</p> |
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<hr /> |
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<h1><a name="bugs">BUGS</a></h1> |
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<p>You kiddin'? |
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|
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</p> |
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<p> |
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</p> |
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<hr /> |
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<h1><a name="authors">AUTHORS</a></h1> |
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<p>Emanuele Giaquinta <em><a href="mailto:<e.giaquinta@glauco.it"><e.giaquinta@glauco.it</a></em>>, Marc Alexander Lehmann |
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<em><a href="mailto:<rxvt-unicode@schmorp.de"><rxvt-unicode@schmorp.de</a></em>>. |
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</p> |
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|
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</body> |
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</html> |
