| /* pt_chown - helper program for 'grantpt'. |
| Copyright (C) 1998-1999, 2009-2020 Free Software Foundation, Inc. |
| Contributed by C. Scott Ananian <cananian@alumni.princeton.edu>, 1998. |
| |
| This program 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. |
| |
| This program 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 <https://www.gnu.org/licenses/>. */ |
| |
| #include <config.h> |
| |
| #include <errno.h> |
| #include <grp.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <sys/stat.h> |
| #include <unistd.h> |
| |
| #include "root-uid.h" |
| |
| #include "pty-private.h" |
| |
| /* For security reasons, we try to minimize the dependencies on libraries |
| outside libc. This means, in particular: |
| - No use of gettext(), since it's usually implemented in libintl. |
| - No use of error() or argp, since they rely on gettext by default. */ |
| |
| |
| static int |
| do_pt_chown (void) |
| { |
| char *pty; |
| struct stat 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 (stat (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 (st.st_gid != gid && 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 & (S_IRWXU|S_IRWXG|S_IRWXO)) != (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 (); |
| |
| if (argc == 1 && euid == ROOT_UID) |
| { |
| /* Normal invocation of this program is with no arguments and |
| with privileges. */ |
| return do_pt_chown (); |
| } |
| |
| /* It would be possible to drop setuid/setgid privileges here. But it is not |
| really needed, since the code below only calls strcmp and [f]printf. */ |
| |
| { |
| int do_help = 0; |
| int do_version = 0; |
| int remaining; |
| |
| for (remaining = 1; remaining < argc; remaining++) |
| { |
| const char *arg = argv[remaining]; |
| |
| if (arg[0] == '-') |
| { |
| if (strcmp (arg, "--") == 0) |
| { |
| remaining++; |
| break; |
| } |
| else if (strcmp (arg, "--help") == 0) |
| do_help = 1; |
| else if (strcmp (arg, "--version") == 0) |
| do_version = 1; |
| else |
| { |
| fprintf (stderr, "pt_chown: invalid option: %s\n", arg); |
| return EXIT_FAILURE; |
| } |
| } |
| else |
| break; |
| } |
| |
| if (remaining < argc) |
| { |
| fprintf (stderr, "pt_chown: too many arguments\n"); |
| return EXIT_FAILURE; |
| } |
| |
| if (do_help) |
| { |
| printf ("Usage: pt_chown [OPTION...]\n"); |
| printf ("Set the owner, group and access permission of the slave pseudo terminal\n" |
| "corresponding to the master pseudo terminal passed on file descriptor %d.\n" |
| "This is the helper program for the 'grantpt' function. It is not intended\n" |
| "to be run directly from the command line.\n", |
| PTY_FILENO); |
| printf ("\n"); |
| printf (" --help Give this help list\n"); |
| printf (" --version Print program version\n"); |
| printf ("\n"); |
| printf ("The owner is set to the current user, the group is set to '%s', and the\n" |
| "access permission is set to '%o'.\n", |
| TTY_GROUP, S_IRUSR|S_IWUSR|S_IWGRP); |
| printf ("Please report bugs to <bug-gnulib@gnu.org>.\n"); |
| return EXIT_SUCCESS; |
| } |
| |
| if (do_version) |
| { |
| printf ("pt_chown (GNU %s) %s\n", "libc", "2.11"); |
| printf ("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", |
| "1999"); |
| return EXIT_SUCCESS; |
| } |
| } |
| |
| /* Check if we are properly installed. */ |
| if (euid != ROOT_UID) |
| { |
| fprintf (stderr, "pt_chown: needs to be installed setuid 'root'\n"); |
| return FAIL_EXEC; |
| } |
| |
| return EXIT_SUCCESS; |
| } |