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/* pt_chmod - helper program for `grantpt'.
Copyright (C) 1998-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by C. Scott Ananian <cananian@alumni.princeton.edu>, 1998.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <argp.h>
#include <errno.h>
#include <error.h>
#include <grp.h>
#include <libintl.h>
#include <locale.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
#ifdef HAVE_LIBCAP
# include <sys/capability.h>
# include <sys/prctl.h>
#endif
#include "pty-private.h"
/* Get libc version number. */
#include "../version.h"
#define PACKAGE _libc_intl_domainname
/* Name and version of program. */
static void print_version (FILE *stream, struct argp_state *state);
void (*argp_program_version_hook) (FILE *, struct argp_state *) = print_version;
/* Function to print some extra text in the help message. */
static char *more_help (int key, const char *text, void *input);
/* Data structure to communicate with argp functions. */
static struct argp argp =
{
NULL, NULL, NULL, NULL, NULL, more_help
};
/* Print the version information. */
static void
print_version (FILE *stream, struct argp_state *state)
{
fprintf (stream, "pt_chown %s%s\n", PKGVERSION, VERSION);
fprintf (stream, gettext ("\
Copyright (C) %s Free Software Foundation, Inc.\n\
This is free software; see the source for copying conditions. There is NO\n\
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\
"), "2021");
}
static char *
more_help (int key, const char *text, void *input)
{
char *cp;
char *tp;
switch (key)
{
case ARGP_KEY_HELP_PRE_DOC:
asprintf (&cp, gettext ("\
Set the owner, group and access permission of the slave pseudo\
terminal corresponding to the master pseudo terminal passed on\
file descriptor `%d'. This is the helper program for the\
`grantpt' function. It is not intended to be run directly from\
the command line.\n"),
PTY_FILENO);
return cp;
case ARGP_KEY_HELP_EXTRA:
/* We print some extra information. */
if (asprintf (&tp, gettext ("\
For bug reporting instructions, please see:\n\
%s.\n"), REPORT_BUGS_TO) < 0)
return NULL;
if (asprintf (&cp, gettext ("\
The owner is set to the current user, the group is set to `%s',\
and the access permission is set to `%o'.\n\n\
%s"),
TTY_GROUP, S_IRUSR|S_IWUSR|S_IWGRP, tp) < 0)
{
free (tp);
return NULL;
}
return cp;
default:
break;
}
return (char *) text;
}
static int
do_pt_chown (void)
{
char *pty;
struct stat64 st;
struct group *p;
gid_t gid;
/* Check that PTY_FILENO is a valid master pseudo terminal. */
pty = ptsname (PTY_FILENO);
if (pty == NULL)
return errno == EBADF ? FAIL_EBADF : FAIL_EINVAL;
/* Check that the returned slave pseudo terminal is a
character device. */
if (stat64 (pty, &st) < 0 || !S_ISCHR (st.st_mode))
return FAIL_EINVAL;
/* Get the group ID of the special `tty' group. */
p = getgrnam (TTY_GROUP);
gid = p ? p->gr_gid : getgid ();
/* Set the owner to the real user ID, and the group to that special
group ID. */
if (chown (pty, getuid (), gid) < 0)
return FAIL_EACCES;
/* Set the permission mode to readable and writable by the owner,
and writable by the group. */
if ((st.st_mode & ACCESSPERMS) != (S_IRUSR|S_IWUSR|S_IWGRP)
&& chmod (pty, S_IRUSR|S_IWUSR|S_IWGRP) < 0)
return FAIL_EACCES;
return 0;
}
int
main (int argc, char *argv[])
{
uid_t euid = geteuid ();
uid_t uid = getuid ();
int remaining;
sigset_t signalset;
/* Clear any signal mask from the parent process. */
sigemptyset (&signalset);
sigprocmask (SIG_SETMASK, &signalset, NULL);
if (argc == 1 && euid == 0)
{
#ifdef HAVE_LIBCAP
/* Drop privileges. */
if (uid != euid)
{
static const cap_value_t cap_list[] =
{ CAP_CHOWN, CAP_FOWNER };
# define ncap_list (sizeof (cap_list) / sizeof (cap_list[0]))
cap_t caps = cap_init ();
if (caps == NULL)
return FAIL_ENOMEM;
/* There is no reason why these should not work. */
cap_set_flag (caps, CAP_PERMITTED, ncap_list, cap_list, CAP_SET);
cap_set_flag (caps, CAP_EFFECTIVE, ncap_list, cap_list, CAP_SET);
int res = cap_set_proc (caps);
cap_free (caps);
if (__glibc_unlikely (res != 0))
return FAIL_EXEC;
}
#endif
/* Normal invocation of this program is with no arguments and
with privileges. */
return do_pt_chown ();
}
/* We aren't going to be using privileges, so drop them right now. */
setuid (uid);
/* Set locale via LC_ALL. */
setlocale (LC_ALL, "");
/* Set the text message domain. */
textdomain (PACKAGE);
/* parse and process arguments. */
argp_parse (&argp, argc, argv, 0, &remaining, NULL);
if (remaining < argc)
{
/* We should not be called with any non-option parameters. */
error (0, 0, gettext ("too many arguments"));
argp_help (&argp, stdout, ARGP_HELP_SEE | ARGP_HELP_EXIT_ERR,
program_invocation_short_name);
return EXIT_FAILURE;
}
/* Check if we are properly installed. */
if (euid != 0)
error (FAIL_EXEC, 0, gettext ("needs to be installed setuid `root'"));
return EXIT_SUCCESS;
}
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