libptytty/doc/libptytty.3.pod

=head1 NAME

libptytty - OS independent and secure pty/tty and utmp/wtmp/lastlog handling

=head1 SYNOPSIS

   -lptytty

=head1 DESCRIPTION

TODO

=head1 SECURITY CONSIDERATIONS

I<< B<It is of paramount importance that you at least read the following
paragraph!> >>

If you are a typical terminal-like program that just wants one or more
ptys, you should call the C<ptytty::init ()> method (C: C<ptytty_init ()
function) as the very first thing in your program:

   int main (int argc, char *argv[])
   {
      // do nothing here
      ptytty::init ();
      // in C: ptytty_init ();

      // initialise, parse arguments, etc.
   }

This checks wether the program runs setuid or setgid. If yes then it will
fork a helper process and drop privileges.

Some programs need finer control over if and when this helper process
is started, and if and how to drop privileges. For those programs, the
methods C<ptytty::use_helper> and C<ptytty::drop_privileges> are more
useful.

=head1 C++ INTERFACE: THE ptytty CLASS

=head2 STATIC METHODS

=over 4

=item ptytty::init ()

The default way to initialise libptytty. Must be called imemdiately as
the first thing in the C<main> function, or earlier e.g. during static
construction time. The earlier, the better.

This method checks wether the program runs with setuid/setgid permissions
and, if yes, spawns a helper process for pty/tty management. IT then
drops the privileges completely, so the actual program runs without
setuid/setgid privileges.

=item ptytty::use_helper ()

Tries to start a helper process that retains privileges even when the
calling process does not. This is usually called from C<ptytty::init> when
it detects that the program is running setuid or setgid, but can be called
manually if it is inconvinient to drop privileges at startup, or when
you are not running setuid/setgid but want to drop privileges (e.g. when
running as a root-started daemon).

This method will try not to start more than one helper process. The same
helper process cna usually be used form the process starting it an all its
fork'ed (not exec'ed) children

=item ptytty::drop_privileges ()

Drops privileges completely, i.e. sets real, effective and saved user id
to the real user id. Also aborts if this cnanot be achieved. Useful to
make sure that the process doesn't run with special privileges.

=item bool success = ptytty::send_fd (int socket, int fd)

Utility method to send a file descriptor over a unix domain
socket. Returns true if successful, false otherwise. This method is only
exposed for your convinience and is not required for normal operation.

=item int fd = ptytty::recv_fd (int socket)

Utility method to receive a file descriptor over a unix domain
socket. Returns the fd if sucecssful and C<-1> otherwise. This method
is only exposed for your convinience and is not required for normal
operation.

=item ptytty *pty = ptytty::create ()

Creates new ptytty object. Creation does not yet do anything besides
allocating the structure.

A static method is used because the actual ptytty implementation can
differ at runtime, so you need a dynamic object creation facility.

=back


=head2 DYNAMIC/SESSION-RELATED DATA MEMBERS AND METHODS

=over 4

=item int pty_fd = pty->pty

=item int tty_fd = pty->tty

These members contain the pty and tty file descriptors, respectively. They
initially contain C<-1> until a successful to C<ptytty::get>.

=item bool success = pty->get ()

Tries to find, allocate and initialise a new pty/tty pair. Returns C<true>
when successful.

=item pty->login (int cmd_pid, bool login_shell, const char *hostname)

Creates an entry in the systems session database(s) (utmp, wtmp, lastlog).
C<cmd_pid> must be the pid of the process representing the session
(such as the login shell), C<login_shell> defines wether the session is
associated with a login, which influences wether wtmp and lastlog entries
are created, and C<hostname> should identify the "hostname" the user logs
in from, which often is the value of the C<DISPLAY> variable or tty line
in case of local logins.

Calling this method is optional. A session starts at the time of the login
call and extends until the ptytty object is destroyed.

=item pty->close_tty ()

Closes the tty. Useful after forking in the parent/pty process.

=item bool success = pty->make_controlling_tty ()

Tries to make the pty/tty pair the controlling terminal of the current
process. Useful after forking in the child/tty process.

=item pty->set_utf8_mode (bool on)

On systems supporting special UTF-8 line disciplines (e.g. Linux), tries
to enable it for the given pty. Can be called at any time to change the
mode.

=back


=head1 C INTERFACE: THE ptytty FAMILY OF FUNCTIONS

=over 4

=item ptytty_init ()

See C<ptytty::init ()>.
   
=item PTYTTY ptytty_create ()

Creates a new opaque PTYTTY object and returns it. Do not try to access it
in any way excecp by testing it for truthness (e.g. C<if (pty) ....>). See
C<ptytty::create ()>.

=item int ptytty_pty (PTYTTY ptytty)

Return the pty file descriptor. See C<< pty->pty >>.
   
=item int ptytty_tty (PTYTTY ptytty)

Return the tty file descriptor. See C<< pty->tty >>.
   
=item void ptytty_delete (PTYTTY ptytty)

Destroys the PTYTTY object, freeing the pty/tty pair and cleaning up the
utmp/wtmp/lastlog databases, if initialised/used. Same as C<delete pty> in
C++.

=item int ptytty_get (PTYTTY ptytty)

See C<< pty->get >>, returns 0 in case of an error, non-zero otherwise.

=item void ptytty_login (PTYTTY ptytty, int cmd_pid, bool login_shell, const char *hostname)

See C<< pty->login >>.

=item void ptytty_close_tty (PTYTTY ptytty)

See C<< pty->close_tty >>.
   
=item int ptytty_make_controlling_tty (PTYTTY ptytty)

See C<< pty->make_controlling_tty >>.
   
=item void ptytty_set_utf8_mode (PTYTTY ptytty, int on)

See C<< pty->set_utf8_mode >>.

=item void ptytty_drop_privileges ()

See C<< ptytty::drop_privileges >>.
   
=item void ptytty_use_helper ()

See C<< ptytty::use_helper >>.

=back


=head1 BUGS

You kiddin'?

=head1 AUTHORS

Emanuele Giaquinta L<< <e.giaquinta@glauco.it> >>, Marc Alexander Lehmann
L<< <rxvt-unicode@schmorp.de> >>.
Revision:	1.7
Committed:	Mon Jan 23 12:27:13 2006 UTC (20 years, 7 months ago) by root
Branch:	MAIN
Changes since 1.6:	+75 -4 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.2	libptytty - OS independent and secure pty/tty and utmp/wtmp/lastlog handling
4	root	1.1
5			=head1 SYNOPSIS
6
7	root	1.2	-lptytty
8	root	1.1
9			=head1 DESCRIPTION
10
11	root	1.6	TODO
12
13	root	1.4	=head1 SECURITY CONSIDERATIONS
14	root	1.3
15	ayin	1.5	I<< B<It is of paramount importance that you at least read the following
16	root	1.4	paragraph!> >>
17
18			If you are a typical terminal-like program that just wants one or more
19	root	1.7	ptys, you should call the C<ptytty::init ()> method (C: C<ptytty_init ()
20			function) as the very first thing in your program:
21	root	1.4
22			int main (int argc, char *argv[])
23			{
24			// do nothing here
25			ptytty::init ();
26	root	1.7	// in C: ptytty_init ();
27	root	1.4
28			// initialise, parse arguments, etc.
29			}
30
31			This checks wether the program runs setuid or setgid. If yes then it will
32			fork a helper process and drop privileges.
33
34	root	1.6	Some programs need finer control over if and when this helper process
35			is started, and if and how to drop privileges. For those programs, the
36			methods C<ptytty::use_helper> and C<ptytty::drop_privileges> are more
37			useful.
38
39	root	1.7	=head1 C++ INTERFACE: THE ptytty CLASS
40	root	1.6
41			=head2 STATIC METHODS
42
43			=over 4
44
45			=item ptytty::init ()
46
47			The default way to initialise libptytty. Must be called imemdiately as
48			the first thing in the C<main> function, or earlier e.g. during static
49			construction time. The earlier, the better.
50
51			This method checks wether the program runs with setuid/setgid permissions
52			and, if yes, spawns a helper process for pty/tty management. IT then
53			drops the privileges completely, so the actual program runs without
54			setuid/setgid privileges.
55
56			=item ptytty::use_helper ()
57
58	root	1.7	Tries to start a helper process that retains privileges even when the
59			calling process does not. This is usually called from C<ptytty::init> when
60			it detects that the program is running setuid or setgid, but can be called
61			manually if it is inconvinient to drop privileges at startup, or when
62			you are not running setuid/setgid but want to drop privileges (e.g. when
63			running as a root-started daemon).
64
65			This method will try not to start more than one helper process. The same
66			helper process cna usually be used form the process starting it an all its
67			fork'ed (not exec'ed) children
68	root	1.6
69			=item ptytty::drop_privileges ()
70
71			Drops privileges completely, i.e. sets real, effective and saved user id
72			to the real user id. Also aborts if this cnanot be achieved. Useful to
73			make sure that the process doesn't run with special privileges.
74
75			=item bool success = ptytty::send_fd (int socket, int fd)
76
77			Utility method to send a file descriptor over a unix domain
78			socket. Returns true if successful, false otherwise. This method is only
79			exposed for your convinience and is not required for normal operation.
80
81			=item int fd = ptytty::recv_fd (int socket)
82
83			Utility method to receive a file descriptor over a unix domain
84			socket. Returns the fd if sucecssful and C<-1> otherwise. This method
85			is only exposed for your convinience and is not required for normal
86			operation.
87	root	1.4
88	root	1.6	=item ptytty *pty = ptytty::create ()
89	root	1.3
90	root	1.6	Creates new ptytty object. Creation does not yet do anything besides
91			allocating the structure.
92
93			A static method is used because the actual ptytty implementation can
94			differ at runtime, so you need a dynamic object creation facility.
95
96			=back
97
98	root	1.7
99	root	1.6	=head2 DYNAMIC/SESSION-RELATED DATA MEMBERS AND METHODS
100	root	1.1
101			=over 4
102
103	root	1.6	=item int pty_fd = pty->pty
104
105			=item int tty_fd = pty->tty
106
107			These members contain the pty and tty file descriptors, respectively. They
108			initially contain C<-1> until a successful to C<ptytty::get>.
109
110			=item bool success = pty->get ()
111
112			Tries to find, allocate and initialise a new pty/tty pair. Returns C<true>
113			when successful.
114
115			=item pty->login (int cmd_pid, bool login_shell, const char *hostname)
116
117			Creates an entry in the systems session database(s) (utmp, wtmp, lastlog).
118			C<cmd_pid> must be the pid of the process representing the session
119			(such as the login shell), C<login_shell> defines wether the session is
120			associated with a login, which influences wether wtmp and lastlog entries
121			are created, and C<hostname> should identify the "hostname" the user logs
122			in from, which often is the value of the C<DISPLAY> variable or tty line
123			in case of local logins.
124
125			Calling this method is optional. A session starts at the time of the login
126			call and extends until the ptytty object is destroyed.
127
128			=item pty->close_tty ()
129
130			Closes the tty. Useful after forking in the parent/pty process.
131
132			=item bool success = pty->make_controlling_tty ()
133
134			Tries to make the pty/tty pair the controlling terminal of the current
135			process. Useful after forking in the child/tty process.
136
137			=item pty->set_utf8_mode (bool on)
138	root	1.1
139	root	1.6	On systems supporting special UTF-8 line disciplines (e.g. Linux), tries
140			to enable it for the given pty. Can be called at any time to change the
141			mode.
142	root	1.1
143			=back
144
145	root	1.7
146			=head1 C INTERFACE: THE ptytty FAMILY OF FUNCTIONS
147
148			=over 4
149
150			=item ptytty_init ()
151
152			See C<ptytty::init ()>.
153
154			=item PTYTTY ptytty_create ()
155
156			Creates a new opaque PTYTTY object and returns it. Do not try to access it
157			in any way excecp by testing it for truthness (e.g. C<if (pty) ....>). See
158			C<ptytty::create ()>.
159
160			=item int ptytty_pty (PTYTTY ptytty)
161
162			Return the pty file descriptor. See C<< pty->pty >>.
163
164			=item int ptytty_tty (PTYTTY ptytty)
165
166			Return the tty file descriptor. See C<< pty->tty >>.
167
168			=item void ptytty_delete (PTYTTY ptytty)
169
170			Destroys the PTYTTY object, freeing the pty/tty pair and cleaning up the
171			utmp/wtmp/lastlog databases, if initialised/used. Same as C<delete pty> in
172			C++.
173
174			=item int ptytty_get (PTYTTY ptytty)
175
176			See C<< pty->get >>, returns 0 in case of an error, non-zero otherwise.
177
178			=item void ptytty_login (PTYTTY ptytty, int cmd_pid, bool login_shell, const char *hostname)
179
180			See C<< pty->login >>.
181
182			=item void ptytty_close_tty (PTYTTY ptytty)
183
184			See C<< pty->close_tty >>.
185
186			=item int ptytty_make_controlling_tty (PTYTTY ptytty)
187
188			See C<< pty->make_controlling_tty >>.
189
190			=item void ptytty_set_utf8_mode (PTYTTY ptytty, int on)
191
192			See C<< pty->set_utf8_mode >>.
193
194			=item void ptytty_drop_privileges ()
195
196			See C<< ptytty::drop_privileges >>.
197
198			=item void ptytty_use_helper ()
199
200			See C<< ptytty::use_helper >>.
201
202			=back
203
204
205	root	1.1	=head1 BUGS
206
207			You kiddin'?
208
209			=head1 AUTHORS
210
211			Emanuele Giaquinta L<< <e.giaquinta@glauco.it> >>, Marc Alexander Lehmann
212			L<< <rxvt-unicode@schmorp.de> >>.