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 	struct landlock_ruleset_attr attr = {
124 		.handled_access_fs =	LANDLOCK_ACCESS_FS_READ_FILE	|
125 					LANDLOCK_ACCESS_FS_READ_DIR	|
126 					LANDLOCK_ACCESS_FS_WRITE_FILE	|
127 					LANDLOCK_ACCESS_FS_MAKE_DIR	|
128 					LANDLOCK_ACCESS_FS_MAKE_REG,
129 	};
130 
131 	return landlock_create_ruleset(&attr, sizeof(attr), 0);
132 }
133 
134 static int
135 landlock_unveil(int landlock_fd, const char *path, int perms)
136 {
137 	struct landlock_path_beneath_attr pb;
138 	int err, saved_errno;
139 
140 	pb.allowed_access = perms;
141 
142 	if ((pb.parent_fd = open(path, O_PATH)) == -1)
143 		return -1;
144 
145 	err = landlock_add_rule(landlock_fd, LANDLOCK_RULE_PATH_BENEATH,
146 	    &pb, 0);
147 	saved_errno = errno;
148 	close(pb.parent_fd);
149 	errno = saved_errno;
150 	return err ? -1 : 0;
151 }
152 
153 static int
154 landlock_apply(int fd)
155 {
156 	int r, saved_errno;
157 
158 	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1)
159 		err(1, "%s: prctl(PR_SET_NO_NEW_PRIVS)", __func__);
160 
161 	r = landlock_restrict_self(fd, 0);
162 	saved_errno = errno;
163 	close(fd);
164 	errno = saved_errno;
165 	return r ? -1 : 0;
166 }
167 
168 static int
169 landlock_no_fs(void)
170 {
171 	int fd;
172 
173 	if ((fd = open_landlock()) == -1)
174 		return -1;
175 
176 	return landlock_apply(fd);
177 }
178 
179 void
180 sandbox_net_process(void)
181 {
182 	/*
183 	 * We don't know what paths are required for the TLS stack.
184 	 * Yes, it sucks.
185 	 */
186 	return;
187 }
188 
189 void
190 sandbox_ui_process(void)
191 {
192 	if (landlock_no_fs() == -1)
193 		err(1, "landlock");
194 }
195 
196 void
197 sandbox_fs_process(void)
198 {
199 	int fd, rwc;
200 	char path[PATH_MAX];
201 
202 	if ((fd = open_landlock()) == -1)
203 		err(1, "can't create landlock ruleset");
204 
205 	rwc =	LANDLOCK_ACCESS_FS_READ_FILE	|
206 		LANDLOCK_ACCESS_FS_READ_DIR	|
207 		LANDLOCK_ACCESS_FS_WRITE_FILE	|
208 		LANDLOCK_ACCESS_FS_MAKE_DIR	|
209 		LANDLOCK_ACCESS_FS_MAKE_REG;
210 
211 	if (landlock_unveil(fd, "/tmp", rwc) == -1)
212 		err(1, "landlock_unveil(/tmp)");
213 
214 	strlcpy(path, getenv("HOME"), sizeof(path));
215 	strlcat(path, "/Downloads", sizeof(path));
216 	if (landlock_unveil(fd, path, rwc) == -1 && errno != ENOENT)
217 		err(1, "landlock_unveil(%s)", path);
218 
219 	if (landlock_unveil(fd, config_path_base, rwc) == -1)
220 		err(1, "landlock_unveil(%s)", config_path_base);
221 
222 	if (landlock_unveil(fd, data_path_base, rwc) == -1)
223 		err(1, "landlock_unveil(%s)", data_path_base);
224 
225 	if (landlock_unveil(fd, cache_path_base, rwc) == -1)
226 		err(1, "landlock_unveil(%s)", cache_path_base);
227 }
228 
229 #else
230 
231 #warning "No sandbox for this OS"
232 
233 void
234 sandbox_net_process(void)
235 {
236 	return;
237 }
238 
239 void
240 sandbox_ui_process(void)
241 {
242 	return;
243 }
244 
245 void
246 sandbox_fs_process(void)
247 {
248 	return;
249 }
250 
251 #endif