1 | /* Copyright (C) 2000-2022 Free Software Foundation, Inc. |
2 | This file is part of the GNU C Library. |
3 | |
4 | The GNU C Library is free software; you can redistribute it and/or |
5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either |
7 | version 2.1 of the License, or (at your option) any later version. |
8 | |
9 | The GNU C Library is distributed in the hope that it will be useful, |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
12 | Lesser General Public License for more details. |
13 | |
14 | You should have received a copy of the GNU Lesser General Public |
15 | License along with the GNU C Library; if not, see |
16 | <https://www.gnu.org/licenses/>. */ |
17 | |
18 | #include <fcntl.h> |
19 | #include <paths.h> |
20 | #include <unistd.h> |
21 | |
22 | #include <hurd.h> |
23 | #include <hurd/fd.h> |
24 | |
25 | #include <set-hooks.h> |
26 | |
27 | /* Try to get a machine dependent instruction which will make the |
28 | program crash. This is used in case everything else fails. */ |
29 | #include <abort-instr.h> |
30 | #ifndef ABORT_INSTRUCTION |
31 | /* No such instruction is available. */ |
32 | # define ABORT_INSTRUCTION |
33 | #endif |
34 | |
35 | static void |
36 | check_one_fd (int fd, int mode) |
37 | { |
38 | struct hurd_fd *d; |
39 | |
40 | d = _hurd_fd_get (fd); |
41 | if (d == NULL) |
42 | { |
43 | /* This descriptor hasn't been opened. We try to allocate the |
44 | descriptor and open /dev/null on it so that the SUID program |
45 | we are about to start does not accidentally use this |
46 | descriptor. */ |
47 | d = _hurd_alloc_fd (NULL, fd); |
48 | if (d != NULL) |
49 | { |
50 | mach_port_t port; |
51 | |
52 | port = __file_name_lookup (_PATH_DEVNULL, mode, 0); |
53 | if (port) |
54 | { |
55 | /* Since /dev/null isn't supposed to be a terminal, we |
56 | avoid any ctty magic. */ |
57 | d->port.port = port; |
58 | d->flags = 0; |
59 | |
60 | __spin_unlock (&d->port.lock); |
61 | return; |
62 | } |
63 | } |
64 | |
65 | /* We cannot even give an error message here since it would run |
66 | into the same problems. */ |
67 | while (1) |
68 | /* Try for ever and ever. */ |
69 | ABORT_INSTRUCTION; |
70 | } |
71 | } |
72 | |
73 | static void |
74 | check_standard_fds (void) |
75 | { |
76 | /* Check all three standard file descriptors. */ |
77 | check_one_fd (STDIN_FILENO, O_RDONLY); |
78 | check_one_fd (STDOUT_FILENO, O_RDWR); |
79 | check_one_fd (STDERR_FILENO, O_RDWR); |
80 | } |
81 | |
82 | static void attribute_used_retain |
83 | init_standard_fds (void) |
84 | { |
85 | /* Now that we have FDs, make sure that, if this is a SUID program, |
86 | FDs 0, 1 and 2 are allocated. If necessary we'll set them up |
87 | ourselves. If that's not possible we stop the program. */ |
88 | if (__builtin_expect (__libc_enable_secure, 0)) |
89 | check_standard_fds (); |
90 | } |
91 | SET_RELHOOK (_hurd_fd_subinit, init_standard_fds); |
92 | |
93 | |
94 | #ifndef SHARED |
95 | void |
96 | __libc_check_standard_fds (void) |
97 | { |
98 | /* We don't check the standard file descriptors here. They will be |
99 | checked when we initialize the file descriptor table, as part of |
100 | the _hurd_fd_subinit hook. |
101 | |
102 | This function is only present to make sure that this module gets |
103 | linked in when part of the static libc. */ |
104 | } |
105 | #endif |
106 | |