[ViewVC] Annotation of: cvs/libptytty/README

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

SYNOPSIS
       -lptytty

DESCRIPTION
    TODO

SECURITY CONSIDERATIONS
    *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 "ptytty::init ()" method (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 "ptytty::use_helper" and "ptytty::drop_privileges" are more
    useful.

C++ INTERFACE: THE ptytty CLASS
  STATIC METHODS
    ptytty::init ()
        The default way to initialise libptytty. Must be called imemdiately
        as the first thing in the "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.

    ptytty::use_helper ()
        Tries to start a helper process that retains privileges even when
        the calling process does not. This is usually called from
        "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

    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.

    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.

    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 -1 otherwise. This method
        is only exposed for your convinience and is not required for normal
        operation.

    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.

  DYNAMIC/SESSION-RELATED DATA MEMBERS AND METHODS
    int pty_fd = pty->pty
    int tty_fd = pty->tty
        These members contain the pty and tty file descriptors,
        respectively. They initially contain -1 until a successful to
        "ptytty::get".

    bool success = pty->get ()
        Tries to find, allocate and initialise a new pty/tty pair. Returns
        "true" when successful.

    pty->login (int cmd_pid, bool login_shell, const char *hostname)
        Creates an entry in the systems session database(s) (utmp, wtmp,
        lastlog). "cmd_pid" must be the pid of the process representing the
        session (such as the login shell), "login_shell" defines wether the
        session is associated with a login, which influences wether wtmp and
        lastlog entries are created, and "hostname" should identify the
        "hostname" the user logs in from, which often is the value of the
        "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.

    pty->close_tty ()
        Closes the tty. Useful after forking in the parent/pty process.

    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.

    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.

C INTERFACE: THE ptytty FAMILY OF FUNCTIONS
    ptytty_init ()
        See "ptytty::init ()".

    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. "if
        (pty) ...."). See "ptytty::create ()".

    int ptytty_pty (PTYTTY ptytty)
        Return the pty file descriptor. See "pty->pty".

    int ptytty_tty (PTYTTY ptytty)
        Return the tty file descriptor. See "pty->tty".

    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
        "delete pty" in C++.

    int ptytty_get (PTYTTY ptytty)
        See "pty->get", returns 0 in case of an error, non-zero otherwise.

    void ptytty_login (PTYTTY ptytty, int cmd_pid, bool login_shell, const
    char *hostname)
        See "pty->login".

    void ptytty_close_tty (PTYTTY ptytty)
        See "pty->close_tty".

    int ptytty_make_controlling_tty (PTYTTY ptytty)
        See "pty->make_controlling_tty".

    void ptytty_set_utf8_mode (PTYTTY ptytty, int on)
        See "pty->set_utf8_mode".

    void ptytty_drop_privileges ()
        See "ptytty::drop_privileges".

    void ptytty_use_helper ()
        See "ptytty::use_helper".

BUGS
    You kiddin'?

AUTHORS
    Emanuele Giaquinta <e.giaquinta@glauco.it>, Marc Alexander Lehmann
    <rxvt-unicode@schmorp.de>.

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