Adding upstream version 3:4.8.29.upstream/3%4.8.29upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 286 insertions, 0 deletions

diff --git a/src/consaver/cons.saver.c b/src/consaver/cons.saver.c
new file mode 100644
index 0000000..05dbb25
--- /dev/null
+++ b/src/consaver/cons.saver.c
@@ -0,0 +1,286 @@
+/*
+   General purpose Linux console screen save/restore server
+
+   This program should be setuid vcsa and /dev/vcsa* should be
+   owned by the same user too.
+
+   Original idea from Unix Interactive Tools version 3.2b (tty.c)
+   This code requires root privileges.
+   You may want to make the cons.saver setuid root.
+   The code should be safe even if it is setuid but who knows?
+
+   Partly rewritten by Jakub Jelinek <jakub@redhat.com>.
+
+   Copyright (C) 1994-2022
+   Free Software Foundation, Inc.
+
+   This file is part of the Midnight Commander.
+
+   The Midnight Commander is free software: you can redistribute it
+   and/or modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation, either version 3 of the License,
+   or (at your option) any later version.
+
+   The Midnight Commander is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* This code does _not_ need to be setuid root. However, it needs
+   read/write access to /dev/vcsa* (which is priviledged
+   operation). You should create user vcsa, make cons.saver setuid
+   user vcsa, and make all vcsa's owned by user vcsa.
+
+   Seeing other peoples consoles is bad thing, but believe me, full
+   root is even worse. */
+
+/** \file cons.saver.c
+ *  \brief Source: general purpose Linux console screen save/restore server
+ *
+ *  This code does _not_ need to be setuid root. However, it needs
+ *  read/write access to /dev/vcsa* (which is priviledged
+ *  operation). You should create user vcsa, make cons.saver setuid
+ *  user vcsa, and make all vcsa's owned by user vcsa.
+ *  Seeing other peoples consoles is bad thing, but believe me, full
+ *  root is even worse.
+ */
+
+#include <config.h>
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#ifdef HAVE_SYS_IOCTL_H
+#include <sys/ioctl.h>
+#endif
+#ifdef HAVE_FCNTL_H
+#include <fcntl.h>
+#endif
+#include <termios.h>
+
+#include "lib/unixcompat.h"     /* STDERR_FILENO */
+
+#define LINUX_CONS_SAVER_C
+#include "cons.saver.h"
+
+/*** global variables ****************************************************************************/
+
+/*** file scope macro definitions ****************************************************************/
+
+/*** file scope type declarations ****************************************************************/
+
+/*** file scope variables ************************************************************************/
+
+/*** file scope functions ************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+static void
+send_contents (char *buffer, unsigned int columns, unsigned int rows)
+{
+    unsigned char begin_line = 0, end_line = 0;
+    unsigned int lastline, lc_index, x;
+    unsigned char message, outbuf[1024], *p;
+    unsigned short bytes;
+
+    lc_index = 2 * rows * columns;
+    for (lastline = rows; lastline > 0; lastline--)
+        for (x = 0; x < columns; x++)
+        {
+            lc_index -= 2;
+            if (buffer[lc_index] != ' ')
+                goto out;
+        }
+  out:
+
+    message = CONSOLE_CONTENTS;
+    if (write (1, &message, 1) != 1)
+        return;
+    if (read (0, &begin_line, 1) != 1)
+        return;
+    if (read (0, &end_line, 1) != 1)
+        return;
+    if (begin_line > lastline)
+        begin_line = lastline;
+    if (end_line > lastline)
+        end_line = lastline;
+
+    lc_index = (end_line - begin_line) * columns;
+    bytes = lc_index;
+
+    if (write (1, &bytes, 2) != 2)
+        return;
+    if (bytes == 0)
+        return;
+
+    p = outbuf;
+    for (lc_index = 2 * begin_line * columns; lc_index < 2 * end_line * columns; lc_index += 2)
+    {
+        *p++ = buffer[lc_index];
+        if (p == outbuf + sizeof (outbuf))
+        {
+            if (write (1, outbuf, sizeof (outbuf)) != sizeof (outbuf))
+                return;
+            p = outbuf;
+        }
+    }
+
+    if (p != outbuf)
+        if (write (1, outbuf, p - outbuf) < (p - outbuf))
+            return;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+static void __attribute__ ((noreturn)) die (void)
+{
+    unsigned char zero = 0;
+    ssize_t ret;
+    ret = write (1, &zero, 1);
+    (void) ret;
+    exit (3);
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/*** public functions ****************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+int
+main (int argc, char **argv)
+{
+    unsigned char action = 0, console_flag = 3;
+    int console_fd, vcsa_fd, console_minor, buffer_size;
+    struct stat st;
+    uid_t uid, euid;
+    char *buffer, *tty_name, console_name[16], vcsa_name[16];
+    const char *p, *q;
+    struct winsize winsz;
+
+    close (STDERR_FILENO);
+
+    if (argc != 2)
+        die ();
+
+    tty_name = argv[1];
+    if (strnlen (tty_name, 15) == 15 || strncmp (tty_name, "/dev/", 5))
+        die ();
+
+    setsid ();
+    uid = getuid ();
+    euid = geteuid ();
+
+    if (seteuid (uid) < 0)
+        die ();
+    console_fd = open (tty_name, O_RDONLY);
+    if (console_fd < 0)
+        die ();
+    if (fstat (console_fd, &st) < 0 || !S_ISCHR (st.st_mode))
+        die ();
+#ifdef HAVE_STRUCT_STAT_ST_RDEV
+    if ((st.st_rdev & 0xff00) != 0x0400)
+        die ();
+    console_minor = (int) (st.st_rdev & 0x00ff);
+#else
+    console_minor = 1;          /* FIXME */
+#endif
+    if (console_minor < 1 || console_minor > 63)
+        die ();
+    if (st.st_uid != uid)
+        die ();
+
+    switch (tty_name[5])
+    {
+        /* devfs */
+    case 'v':
+        p = "/dev/vc/%d";
+        q = "/dev/vcc/a%d";
+        break;
+        /* /dev/ttyN */
+    case 't':
+        p = "/dev/tty%d";
+        q = "/dev/vcsa%d";
+        break;
+    default:
+        die ();
+    }
+
+    snprintf (console_name, sizeof (console_name), p, console_minor);
+    if (strncmp (console_name, tty_name, sizeof (console_name)) != 0)
+        die ();
+
+    if (seteuid (euid) < 0)
+        die ();
+
+    snprintf (vcsa_name, sizeof (vcsa_name), q, console_minor);
+    vcsa_fd = open (vcsa_name, O_RDWR);
+    if (vcsa_fd < 0)
+        die ();
+    if (fstat (vcsa_fd, &st) < 0 || !S_ISCHR (st.st_mode))
+        die ();
+
+    if (seteuid (uid) < 0)
+        die ();
+
+    winsz.ws_col = winsz.ws_row = 0;
+    if (ioctl (console_fd, TIOCGWINSZ, &winsz) < 0
+        || winsz.ws_col <= 0 || winsz.ws_row <= 0 || winsz.ws_col >= 256 || winsz.ws_row >= 256)
+        die ();
+
+    buffer_size = 4 + 2 * winsz.ws_col * winsz.ws_row;
+    buffer = calloc (buffer_size, 1);
+    if (buffer == NULL)
+        die ();
+
+    if (write (1, &console_flag, 1) != 1)
+        die ();
+
+    while (console_flag && read (0, &action, 1) == 1)
+    {
+        switch (action)
+        {
+        case CONSOLE_DONE:
+            console_flag = 0;
+            continue;
+        case CONSOLE_SAVE:
+            if (seteuid (euid) < 0
+                || lseek (vcsa_fd, 0, 0) != 0
+                || fstat (console_fd, &st) < 0 || st.st_uid != uid
+                || read (vcsa_fd, buffer, buffer_size) != buffer_size
+                || fstat (console_fd, &st) < 0 || st.st_uid != uid)
+                memset (buffer, 0, buffer_size);
+            if (seteuid (uid) < 0)
+                die ();
+            break;
+        case CONSOLE_RESTORE:
+            if (seteuid (euid) >= 0
+                && lseek (vcsa_fd, 0, 0) == 0 && fstat (console_fd, &st) >= 0 && st.st_uid == uid)
+                if (write (vcsa_fd, buffer, buffer_size) != buffer_size)
+                    die ();
+            if (seteuid (uid) < 0)
+                die ();
+            break;
+        case CONSOLE_CONTENTS:
+            send_contents (buffer + 4, winsz.ws_col, winsz.ws_row);
+            break;
+        default:
+            break;
+        }
+
+        if (write (1, &console_flag, 1) != 1)
+            die ();
+    }
+
+    exit (0);
+}
+
+/* --------------------------------------------------------------------------------------------- */