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* cons.saver.c: Eliminate some global variables. Further
cleanup. Make sure that console_fd is always closed.
This commit is contained in:
Pavel Roskin
parent
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commit
7bab33656b
@ -1,3 +1,8 @@
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2002-07-29 Pavel Roskin <proski@gnu.org>
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* cons.saver.c: Eliminate some global variables. Further
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cleanup. Make sure that console_fd is always closed.
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2002-07-28 Pavel Roskin <proski@gnu.org>
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* cons.saver.c: Remove support for Linux kernels before 2.0.
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@ -4,8 +4,6 @@
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Copyright (C) 1994 Janne Kukonlehto <jtklehto@stekt.oulu.fi>
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Original idea from Unix Interactive Tools version 3.2b (tty.c)
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This code requires root privileges.
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You may want to make the cons.saver setuid root.
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The code should be safe even if it is setuid but who knows?
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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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@ -21,13 +19,15 @@
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
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/* This code does _not_ need to be setuid root. However, it needs
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read/write access to /dev/vcsa* (which is priviledged
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operation). You should create user vcsa, make cons.saver setuid
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user vcsa, and make all vcsa's owned by user vcsa.
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Seeing other peoples consoles is bad thing, but believe me, full
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root is even worse. */
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/* cons.saver is run by MC to save and restore screen contents on Linux
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virtual console. This is done by using file /dev/vcsaN or /dev/vcc/aN,
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where N is the number of the virtual console.
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In a properly set up system, /dev/vcsaN should become accessible
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by the user when the user logs in on the corresponding console
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/dev/ttyN or /dev/vc/N. In this case, cons.saver doesn't need to be
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suid root. However, if /dev/vcsaN is not accessible by the user,
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cons.saver can be made setuid root - this program is designed to be
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safe even in this case. */
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#include <config.h>
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#include <sys/types.h>
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@ -50,15 +50,6 @@
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#define cmd_input 0
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#define cmd_output 1
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/* Meaning of console_flag:
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-1 == to be detected,
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0 == not a console or Linux < 1.1.92
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1 == obsolete, not used
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2 == obsolete, not used
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3 == is a console, Linux >= 1.1.92 (color, use /dev/vcsa$num
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*/
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static signed char console_flag = -1;
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static char *tty_name;
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static int console_minor = 0;
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static char *buffer = NULL;
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static int buffer_size = 0;
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@ -66,23 +57,31 @@ static int columns, rows;
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static int vcs_fd;
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static void tty_getsize (int console_fd)
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/*
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* Get window size for the given terminal.
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* Return 0 for success, -1 otherwise.
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*/
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static int tty_getsize (int console_fd)
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{
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struct winsize winsz;
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winsz.ws_col = winsz.ws_row = 0;
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ioctl (console_fd, TIOCGWINSZ, &winsz);
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if (winsz.ws_col && winsz.ws_row){
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if (winsz.ws_col && winsz.ws_row) {
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columns = winsz.ws_col;
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rows = winsz.ws_row;
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} else {
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/* Never happens (I think) */
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columns = 80;
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rows = 25;
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console_flag = 0;
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return 0;
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}
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return -1;
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}
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/*
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* Do various checks to make sure that the supplied filename is
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* a suitable tty device. If check_console is set, check that we
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* are dealing with a Linux virtual console.
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* Return 0 for success, -1 otherwise.
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*/
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static int check_file (char *filename, int check_console)
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{
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int fd;
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@ -129,11 +128,14 @@ static int check_file (char *filename, int check_console)
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return -1;
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}
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/* Detect console. Return 0 if successful, -1 otherwise. */
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/* Because the name of the tty is supplied by the user and this
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can be a setuid program a lot of checks has to done to avoid
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creating a security hole */
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static int detect_console (void)
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/*
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* Check if the supplied filename is a Linux virtual console.
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* Return 0 if successful, -1 otherwise.
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* Since the tty name is supplied by the user and cons.saver can be
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* a setuid program, many checks have to be done to prevent possible
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* security compromise.
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*/
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static int detect_console (char *tty_name)
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{
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char console_name [16];
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static char vcs_name [16];
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@ -144,6 +146,13 @@ static int detect_console (void)
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if (console_fd == -1)
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return -1;
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if (tty_getsize (console_fd) == -1) {
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close (console_fd);
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return -1;
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}
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close (console_fd);
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/*
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* Only allow /dev/ttyMINOR and /dev/vc/MINOR where MINOR is the minor
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* device number of the console, set in check_file()
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@ -175,15 +184,10 @@ static int detect_console (void)
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vcs_fd = check_file (vcs_name, 0);
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}
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if (vcs_fd != -1){
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console_flag = 3;
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tty_getsize (console_fd);
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close (console_fd);
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return 0;
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}
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if (vcs_fd == -1)
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return -1;
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close (console_fd);
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return -1;
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return 0;
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}
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static void save_console (void)
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@ -235,7 +239,10 @@ int main (int argc, char **argv)
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{
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unsigned char action = 0;
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int stderr_fd;
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/* 0 - not a console, 3 - supported Linux console */
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signed char console_flag = 0;
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/*
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* Make sure stderr points to a valid place
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*/
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@ -256,7 +263,6 @@ int main (int argc, char **argv)
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if (argc != 2){
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/* Wrong number of arguments */
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console_flag = 0;
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write (cmd_output, &console_flag, 1);
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return 3;
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}
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@ -264,14 +270,12 @@ int main (int argc, char **argv)
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/* Lose the control terminal */
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setsid ();
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/* Check that the argument is a legal console */
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tty_name = argv [1];
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if (detect_console () == -1){
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/* Check that the argument is a Linux console */
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if (detect_console (argv [1]) == -1) {
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/* Not a console -> no need for privileges */
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setuid (getuid ());
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console_flag = 0;
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} else {
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console_flag = 3;
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/* Allocate buffer for screen image */
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buffer_size = 4 + 2 * columns * rows;
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buffer = (char*) malloc (buffer_size);
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@ -298,7 +302,7 @@ int main (int argc, char **argv)
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break;
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} /* switch (action) */
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/* Inform the invoker that command is handled */
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/* Inform the invoker that command has been handled */
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write (cmd_output, &console_flag, 1);
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} /* while (read ...) */
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