1 /*
2  * Copyright (c) 2021 Omar Polo <op@omarpolo.com>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include "compat.h"
18 
19 #include "fs.h"
20 #include "telescope.h"
21 
22 #ifdef __OpenBSD__
23 
24 # include <errno.h>
25 # include <limits.h>
26 # include <stdlib.h>
27 # include <string.h>
28 # include <unistd.h>
29 
30 void
31 sandbox_net_process(void)
32 {
33 	if (pledge("stdio inet dns", NULL) == -1)
34 		err(1, "pledge");
35 }
36 
37 void
38 sandbox_ui_process(void)
39 {
40 	if (pledge("stdio tty recvfd", NULL) == -1)
41 		err(1, "pledge");
42 }
43 
44 void
45 sandbox_fs_process(void)
46 {
47 	char path[PATH_MAX];
48 
49 	if (unveil("/tmp", "rwc") == -1)
50 		err(1, "unveil(/tmp)");
51 
52 	strlcpy(path, getenv("HOME"), sizeof(path));
53 	strlcat(path, "/Downloads", sizeof(path));
54 	if (unveil(path, "rwc") == -1 && errno != ENOENT)
55 		err(1, "unveil(%s)", path);
56 
57 	if (unveil(config_path_base, "rwc") == -1)
58 		err(1, "unveil(%s)", config_path_base);
59 
60 	if (unveil(data_path_base, "rwc") == -1)
61 		err(1, "unveil(%s)", data_path_base);
62 
63 	if (unveil(cache_path_base, "rwc") == -1)
64 		err(1, "unveil(%s)", cache_path_base);
65 
66 	if (pledge("stdio rpath wpath cpath sendfd", NULL) == -1)
67 		err(1, "pledge");
68 }
69 
70 #elif HAVE_LINUX_LANDLOCK_H
71 
72 #include <linux/landlock.h>
73 #include <linux/prctl.h>
74 
75 #include <sys/prctl.h>
76 #include <sys/stat.h>
77 #include <sys/syscall.h>
78 
79 #include <errno.h>
80 #include <fcntl.h>
81 #include <stdlib.h>
82 #include <string.h>
83 #include <unistd.h>
84 
85 /*
86  * What's the deal with landlock?  While distro with linux >= 5.13
87  * have the struct declarations, libc wrappers are missing.  The
88  * sample landlock code provided by the authors includes these "shims"
89  * in their example for the landlock API until libc provides them.
90  *
91  * Linux is such a mess sometimes.  /rant
92  */
93 
94 #ifndef landlock_create_ruleset
95 static inline int
96 landlock_create_ruleset(const struct landlock_ruleset_attr *attr, size_t size,
97     __u32 flags)
98 {
99 	return syscall(__NR_landlock_create_ruleset, attr, size, flags);
100 }
101 #endif
102 
103 #ifndef landlock_add_rule
104 static inline int
105 landlock_add_rule(int ruleset_fd, enum landlock_rule_type type,
106     const void *attr, __u32 flags)
107 {
108 	return syscall(__NR_landlock_add_rule, ruleset_fd, type, attr, flags);
109 }
110 #endif
111 
112 #ifndef landlock_restrict_self
113 static inline int
114 landlock_restrict_self(int ruleset_fd, __u32 flags)
115 {
116 	return syscall(__NR_landlock_restrict_self, ruleset_fd, flags);
117 }
118 #endif
119 
120 static int
121 open_landlock(void)
122 {
123 	int fd;
124 	struct landlock_ruleset_attr attr = {
125 		.handled_access_fs =	LANDLOCK_ACCESS_FS_READ_FILE	|
126 					LANDLOCK_ACCESS_FS_READ_DIR	|
127 					LANDLOCK_ACCESS_FS_WRITE_FILE	|
128 					LANDLOCK_ACCESS_FS_MAKE_DIR	|
129 					LANDLOCK_ACCESS_FS_MAKE_REG,
130 	};
131 
132 	fd = landlock_create_ruleset(&attr, sizeof(attr), 0);
133 	if (fd == -1) {
134 		switch (errno) {
135 		case ENOSYS:
136 		case EOPNOTSUPP:
137 			return -1;
138 		default:
139 			err(1, "can't create landlock ruleset");
140 		}
141 	}
142 	return fd;
143 }
144 
145 static int
146 landlock_unveil(int landlock_fd, const char *path, int perms)
147 {
148 	struct landlock_path_beneath_attr pb;
149 	int err, saved_errno;
150 
151 	pb.allowed_access = perms;
152 
153 	if ((pb.parent_fd = open(path, O_PATH)) == -1)
154 		return -1;
155 
156 	err = landlock_add_rule(landlock_fd, LANDLOCK_RULE_PATH_BENEATH,
157 	    &pb, 0);
158 	saved_errno = errno;
159 	close(pb.parent_fd);
160 	errno = saved_errno;
161 	return err ? -1 : 0;
162 }
163 
164 static int
165 landlock_apply(int fd)
166 {
167 	int r, saved_errno;
168 
169 	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1)
170 		err(1, "%s: prctl(PR_SET_NO_NEW_PRIVS)", __func__);
171 
172 	r = landlock_restrict_self(fd, 0);
173 	saved_errno = errno;
174 	close(fd);
175 	errno = saved_errno;
176 	return r ? -1 : 0;
177 }
178 
179 static int
180 landlock_no_fs(void)
181 {
182 	int fd;
183 
184 	/*
185 	 * XXX: landlock disabled at runtime, pretend everything's
186 	 * good.
187 	 */
188 	if ((fd = open_landlock()) == -1)
189 		return 0;
190 
191 	return landlock_apply(fd);
192 }
193 
194 void
195 sandbox_net_process(void)
196 {
197 	/*
198 	 * We don't know what paths are required for the TLS stack.
199 	 * Yes, it sucks.
200 	 */
201 	return;
202 }
203 
204 void
205 sandbox_ui_process(void)
206 {
207 	if (landlock_no_fs() == -1)
208 		err(1, "landlock");
209 }
210 
211 void
212 sandbox_fs_process(void)
213 {
214 	int fd, rwc;
215 	char path[PATH_MAX];
216 
217 	/*
218 	 * XXX: at build-time we found landlock.h but we've just
219 	 * realized it's not available on this kernel, so do nothing.
220 	 */
221 	if ((fd = open_landlock()) == -1)
222 		return;
223 
224 	rwc =	LANDLOCK_ACCESS_FS_READ_FILE	|
225 		LANDLOCK_ACCESS_FS_READ_DIR	|
226 		LANDLOCK_ACCESS_FS_WRITE_FILE	|
227 		LANDLOCK_ACCESS_FS_MAKE_DIR	|
228 		LANDLOCK_ACCESS_FS_MAKE_REG;
229 
230 	if (landlock_unveil(fd, "/tmp", rwc) == -1)
231 		err(1, "landlock_unveil(/tmp)");
232 
233 	strlcpy(path, getenv("HOME"), sizeof(path));
234 	strlcat(path, "/Downloads", sizeof(path));
235 	if (landlock_unveil(fd, path, rwc) == -1 && errno != ENOENT)
236 		err(1, "landlock_unveil(%s)", path);
237 
238 	if (landlock_unveil(fd, config_path_base, rwc) == -1)
239 		err(1, "landlock_unveil(%s)", config_path_base);
240 
241 	if (landlock_unveil(fd, data_path_base, rwc) == -1)
242 		err(1, "landlock_unveil(%s)", data_path_base);
243 
244 	if (landlock_unveil(fd, cache_path_base, rwc) == -1)
245 		err(1, "landlock_unveil(%s)", cache_path_base);
246 }
247 
248 #else
249 
250 #warning "No sandbox for this OS"
251 
252 void
253 sandbox_net_process(void)
254 {
255 	return;
256 }
257 
258 void
259 sandbox_ui_process(void)
260 {
261 	return;
262 }
263 
264 void
265 sandbox_fs_process(void)
266 {
267 	return;
268 }
269 
270 #endif