2 97799ccd 2022-02-06 thomas * Copyright (c) 2021 Omar Polo <op@openbsd.org>
4 97799ccd 2022-02-06 thomas * Permission to use, copy, modify, and distribute this software for any
5 97799ccd 2022-02-06 thomas * purpose with or without fee is hereby granted, provided that the above
6 97799ccd 2022-02-06 thomas * copyright notice and this permission notice appear in all copies.
8 97799ccd 2022-02-06 thomas * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 97799ccd 2022-02-06 thomas * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 97799ccd 2022-02-06 thomas * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 97799ccd 2022-02-06 thomas * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 97799ccd 2022-02-06 thomas * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 97799ccd 2022-02-06 thomas * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 97799ccd 2022-02-06 thomas * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 97799ccd 2022-02-06 thomas #include <linux/landlock.h>
19 97799ccd 2022-02-06 thomas #include <sys/prctl.h>
20 97799ccd 2022-02-06 thomas #include <sys/syscall.h>
22 97799ccd 2022-02-06 thomas #include <errno.h>
23 97799ccd 2022-02-06 thomas #include <unistd.h>
25 97799ccd 2022-02-06 thomas #include "got_compat.h"
28 97799ccd 2022-02-06 thomas * What's the deal with landlock? While distro with linux >= 5.13
29 97799ccd 2022-02-06 thomas * have the struct declarations, libc wrappers are missing. The
30 97799ccd 2022-02-06 thomas * sample landlock code provided by the authors includes these "shims"
31 97799ccd 2022-02-06 thomas * in their example for the landlock API until libc provides them.
34 97799ccd 2022-02-06 thomas #ifndef landlock_create_ruleset
35 97799ccd 2022-02-06 thomas static inline int
36 97799ccd 2022-02-06 thomas landlock_create_ruleset(const struct landlock_ruleset_attr *attr, size_t size,
37 97799ccd 2022-02-06 thomas __u32 flags)
39 97799ccd 2022-02-06 thomas return syscall(__NR_landlock_create_ruleset, attr, size, flags);
43 97799ccd 2022-02-06 thomas #ifndef landlock_add_rule
44 97799ccd 2022-02-06 thomas static inline int
45 97799ccd 2022-02-06 thomas landlock_add_rule(int ruleset_fd, enum landlock_rule_type type,
46 97799ccd 2022-02-06 thomas const void *attr, __u32 flags)
48 97799ccd 2022-02-06 thomas return syscall(__NR_landlock_add_rule, ruleset_fd, type, attr, flags);
52 97799ccd 2022-02-06 thomas #ifndef landlock_restrict_self
53 97799ccd 2022-02-06 thomas static inline int
54 97799ccd 2022-02-06 thomas landlock_restrict_self(int ruleset_fd, __u32 flags)
56 97799ccd 2022-02-06 thomas return syscall(__NR_landlock_restrict_self, ruleset_fd, flags);
61 97799ccd 2022-02-06 thomas * Revoke any fs access.
64 97799ccd 2022-02-06 thomas landlock_no_fs(void)
66 97799ccd 2022-02-06 thomas struct landlock_ruleset_attr rattr = {
68 9cefc4c1 2022-02-11 op * List all capabilities currently defined by landlock.
69 9cefc4c1 2022-02-11 op * Failure in doing so will implicitly allow those actions
70 9cefc4c1 2022-02-11 op * (i.e. omitting READ_FILE will allow to read _any_ file.)
72 9cefc4c1 2022-02-11 op .handled_access_fs = LANDLOCK_ACCESS_FS_EXECUTE | \
73 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_READ_FILE | \
74 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_READ_DIR | \
75 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_WRITE_FILE | \
76 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_REMOVE_DIR | \
77 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_REMOVE_FILE | \
78 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_MAKE_CHAR | \
79 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_MAKE_DIR | \
80 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_MAKE_REG | \
81 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_MAKE_SOCK | \
82 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_MAKE_FIFO | \
83 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_MAKE_BLOCK | \
84 9cefc4c1 2022-02-11 op LANDLOCK_ACCESS_FS_MAKE_SYM,
86 97799ccd 2022-02-06 thomas int fd, saved_errno;
88 97799ccd 2022-02-06 thomas if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1)
89 97799ccd 2022-02-06 thomas return -1;
91 97799ccd 2022-02-06 thomas fd = landlock_create_ruleset(&rattr, sizeof(rattr), 0);
92 97799ccd 2022-02-06 thomas if (fd == -1) {
93 97799ccd 2022-02-06 thomas /* this kernel doesn't have landlock built in */
94 5e997b01 2022-02-11 op if (errno == ENOSYS || errno == EOPNOTSUPP)
96 97799ccd 2022-02-06 thomas return -1;
99 97799ccd 2022-02-06 thomas if (landlock_restrict_self(fd, 0)) {
100 97799ccd 2022-02-06 thomas saved_errno = errno;
101 97799ccd 2022-02-06 thomas close(fd);
102 97799ccd 2022-02-06 thomas errno = saved_errno;
103 97799ccd 2022-02-06 thomas return -1;
106 97799ccd 2022-02-06 thomas close(fd);
107 97799ccd 2022-02-06 thomas return 0;
