1 /* This program should be setuid vcsa and /dev/vcsa* should be
2 owned by the same user too.
3 Partly rewritten by Jakub Jelinek <jakub@redhat.com>. */
5 /* General purpose Linux console screen save/restore server
6 Copyright (C) 1994, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
7 2006, 2007 Free Software Foundation, Inc.
8 Original idea from Unix Interactive Tools version 3.2b (tty.c)
9 This code requires root privileges.
10 You may want to make the cons.saver setuid root.
11 The code should be safe even if it is setuid but who knows?
13 This program is free software; you can redistribute it and/or modify
14 it under the terms of the GNU General Public License as published by
15 the Free Software Foundation; either version 2 of the License, or
16 (at your option) any later version.
18 This program is distributed in the hope that it will be useful,
19 but WITHOUT ANY WARRANTY; without even the implied warranty of
20 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21 GNU General Public License for more details.
23 You should have received a copy of the GNU General Public License
24 along with this program; if not, write to the Free Software
25 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
27 /* This code does _not_ need to be setuid root. However, it needs
28 read/write access to /dev/vcsa* (which is priviledged
29 operation). You should create user vcsa, make cons.saver setuid
30 user vcsa, and make all vcsa's owned by user vcsa.
32 Seeing other peoples consoles is bad thing, but believe me, full
33 root is even worse. */
47 #include <sys/types.h>
49 #include <sys/ioctl.h>
56 #define LINUX_CONS_SAVER_C
57 #include "cons.saver.h"
60 send_contents (char *buffer
, unsigned int columns
, unsigned int rows
)
62 unsigned char begin_line
= 0, end_line
= 0;
63 unsigned int lastline
, index
, x
;
64 unsigned char message
, outbuf
[1024], *p
;
67 index
= 2 * rows
* columns
;
68 for (lastline
= rows
; lastline
> 0; lastline
--)
69 for (x
= 0; x
< columns
; x
++)
72 if (buffer
[index
] != ' ')
77 message
= CONSOLE_CONTENTS
;
78 write (1, &message
, 1);
80 read (0, &begin_line
, 1);
81 read (0, &end_line
, 1);
82 if (begin_line
> lastline
)
83 begin_line
= lastline
;
84 if (end_line
> lastline
)
87 index
= (end_line
- begin_line
) * columns
;
96 for (index
= 2 * begin_line
* columns
;
97 index
< 2 * end_line
* columns
;
100 *p
++ = buffer
[index
];
101 if (p
== outbuf
+ sizeof (outbuf
))
103 write (1, outbuf
, sizeof (outbuf
));
109 write (1, outbuf
, p
- outbuf
);
112 static void __attribute__ ((noreturn
))
115 unsigned char zero
= 0;
121 main (int argc
, char **argv
)
123 unsigned char action
= 0, console_flag
= 3;
124 int console_fd
, vcsa_fd
, console_minor
, buffer_size
;
127 char *buffer
, *tty_name
, console_name
[16], vcsa_name
[16], *p
, *q
;
128 struct winsize winsz
;
136 if (strnlen (tty_name
, 15) == 15
137 || strncmp (tty_name
, "/dev/", 5))
144 if (seteuid (uid
) < 0)
146 console_fd
= open (tty_name
, O_RDONLY
);
149 if (fstat (console_fd
, &st
) < 0 || ! S_ISCHR (st
.st_mode
))
151 if ((st
.st_rdev
& 0xff00) != 0x0400)
153 console_minor
= (int) (st
.st_rdev
& 0x00ff);
154 if (console_minor
< 1 || console_minor
> 63)
156 if (st
.st_uid
!= uid
)
159 switch (tty_name
[5])
162 case 'v': p
= "/dev/vc/%d"; q
= "/dev/vcc/a%d"; break;
164 case 't': p
= "/dev/tty%d"; q
= "/dev/vcsa%d"; break;
165 default: die (); break;
168 snprintf (console_name
, sizeof (console_name
), p
, console_minor
);
169 if (strncmp (console_name
, tty_name
, sizeof (console_name
)) != 0)
172 if (seteuid (euid
) < 0)
175 snprintf (vcsa_name
, sizeof (vcsa_name
), q
, console_minor
);
176 vcsa_fd
= open (vcsa_name
, O_RDWR
);
179 if (fstat (vcsa_fd
, &st
) < 0 || ! S_ISCHR (st
.st_mode
))
182 if (seteuid (uid
) < 0)
185 winsz
.ws_col
= winsz
.ws_row
= 0;
186 if (ioctl (console_fd
, TIOCGWINSZ
, &winsz
) < 0
187 || winsz
.ws_col
<= 0 || winsz
.ws_row
<= 0
188 || winsz
.ws_col
>= 256 || winsz
.ws_row
>= 256)
191 buffer_size
= 4 + 2 * winsz
.ws_col
* winsz
.ws_row
;
192 buffer
= calloc (buffer_size
, 1);
196 write (1, &console_flag
, 1);
198 while (console_flag
&& read (0, &action
, 1) == 1)
206 if (seteuid (euid
) < 0
207 || lseek (vcsa_fd
, 0, 0) != 0
208 || fstat (console_fd
, &st
) < 0 || st
.st_uid
!= uid
209 || read (vcsa_fd
, buffer
, buffer_size
) != buffer_size
210 || fstat (console_fd
, &st
) < 0 || st
.st_uid
!= uid
)
211 memset (buffer
, 0, buffer_size
);
212 if (seteuid (uid
) < 0)
215 case CONSOLE_RESTORE
:
216 if (seteuid (euid
) >= 0
217 && lseek (vcsa_fd
, 0, 0) == 0
218 && fstat (console_fd
, &st
) >= 0 && st
.st_uid
== uid
)
219 write (vcsa_fd
, buffer
, buffer_size
);
220 if (seteuid (uid
) < 0)
223 case CONSOLE_CONTENTS
:
224 send_contents (buffer
+ 4, winsz
.ws_col
, winsz
.ws_row
);
228 write (1, &console_flag
, 1);