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Date:: Fri Oct 8 17:07:09 2021 UTC
Message:: add landlock support on linux landlock is applied only to the ui process to drop fs access and in the fs process to limit where telescope can read/write files. The network process is more difficult to landlock because while in theory it doesn't need *any* fs access, in practice it needs to read (at least) files inside /etc/ for DNS to work.
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  1 677d90f7 2021-03-12 op /*
  2 677d90f7 2021-03-12 op  * Copyright (c) 2021 Omar Polo <op@omarpolo.com>
  3 677d90f7 2021-03-12 op  *
  4 677d90f7 2021-03-12 op  * Permission to use, copy, modify, and distribute this software for any
  5 677d90f7 2021-03-12 op  * purpose with or without fee is hereby granted, provided that the above
  6 677d90f7 2021-03-12 op  * copyright notice and this permission notice appear in all copies.
  7 677d90f7 2021-03-12 op  *
  8 677d90f7 2021-03-12 op  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  9 677d90f7 2021-03-12 op  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 10 677d90f7 2021-03-12 op  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 11 677d90f7 2021-03-12 op  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 12 677d90f7 2021-03-12 op  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 13 677d90f7 2021-03-12 op  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 14 677d90f7 2021-03-12 op  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 15 677d90f7 2021-03-12 op  */
 16 677d90f7 2021-03-12 op 
 17 a9d11f81 2021-10-08 op #include "compat.h"
 18 a9d11f81 2021-10-08 op 
 19 4b877649 2021-10-07 op #include "fs.h"
 20 754622a2 2021-03-15 op #include "telescope.h"
 21 677d90f7 2021-03-12 op 
 22 677d90f7 2021-03-12 op #ifdef __OpenBSD__
 23 677d90f7 2021-03-12 op 
 24 35e1f40a 2021-03-14 op # include <limits.h>
 25 35e1f40a 2021-03-14 op # include <stdlib.h>
 26 35e1f40a 2021-03-14 op # include <string.h>
 27 2b1f38ab 2021-03-13 op # include <unistd.h>
 28 2b1f38ab 2021-03-13 op 
 29 677d90f7 2021-03-12 op void
 30 17c10c65 2021-07-12 op sandbox_net_process(void)
 31 677d90f7 2021-03-12 op {
 32 677d90f7 2021-03-12 op 	if (pledge("stdio inet dns", NULL) == -1)
 33 677d90f7 2021-03-12 op 		err(1, "pledge");
 34 677d90f7 2021-03-12 op }
 35 677d90f7 2021-03-12 op 
 36 b1d4d01b 2021-03-14 op void
 37 b1d4d01b 2021-03-14 op sandbox_ui_process(void)
 38 b1d4d01b 2021-03-14 op {
 39 de2a69bb 2021-05-17 op 	if (pledge("stdio tty recvfd", NULL) == -1)
 40 b1d4d01b 2021-03-14 op 		err(1, "pledge");
 41 b1d4d01b 2021-03-14 op }
 42 b1d4d01b 2021-03-14 op 
 43 35e1f40a 2021-03-14 op void
 44 35e1f40a 2021-03-14 op sandbox_fs_process(void)
 45 35e1f40a 2021-03-14 op {
 46 35e1f40a 2021-03-14 op 	char path[PATH_MAX];
 47 35e1f40a 2021-03-14 op 
 48 de2a69bb 2021-05-17 op 	if (unveil("/tmp", "rwc") == -1)
 49 35e1f40a 2021-03-14 op 		err(1, "unveil");
 50 35e1f40a 2021-03-14 op 
 51 35e1f40a 2021-03-14 op 	strlcpy(path, getenv("HOME"), sizeof(path));
 52 35e1f40a 2021-03-14 op 	strlcat(path, "/Downloads", sizeof(path));
 53 6845bee7 2021-09-13 op 	if (unveil(path, "rwc") == -1)
 54 fd0beb53 2021-10-07 op 		err(1, "unveil(%s)", path);
 55 35e1f40a 2021-03-14 op 
 56 4b877649 2021-10-07 op 	if (unveil(config_path_base, "rwc") == -1)
 57 fd0beb53 2021-10-07 op 		err(1, "unveil(%s)", config_path_base);
 58 35e1f40a 2021-03-14 op 
 59 4b877649 2021-10-07 op 	if (unveil(data_path_base, "rwc") == -1)
 60 fd0beb53 2021-10-07 op 		err(1, "unveil(%s)", data_path_base);
 61 4b877649 2021-10-07 op 
 62 4b877649 2021-10-07 op 	if (unveil(cache_path_base, "rwc") == -1)
 63 fd0beb53 2021-10-07 op 		err(1, "unveil(%s)", cache_path_base);
 64 4b877649 2021-10-07 op 
 65 de2a69bb 2021-05-17 op 	if (pledge("stdio rpath wpath cpath sendfd", NULL) == -1)
 66 35e1f40a 2021-03-14 op 		err(1, "pledge");
 67 35e1f40a 2021-03-14 op }
 68 35e1f40a 2021-03-14 op 
 69 a9d11f81 2021-10-08 op #elif HAVE_LINUX_LANDLOCK_H
 70 a9d11f81 2021-10-08 op 
 71 a9d11f81 2021-10-08 op #include <linux/landlock.h>
 72 a9d11f81 2021-10-08 op #include <linux/prctl.h>
 73 a9d11f81 2021-10-08 op 
 74 a9d11f81 2021-10-08 op #include <sys/prctl.h>
 75 a9d11f81 2021-10-08 op #include <sys/stat.h>
 76 a9d11f81 2021-10-08 op #include <sys/syscall.h>
 77 a9d11f81 2021-10-08 op 
 78 a9d11f81 2021-10-08 op #include <fcntl.h>
 79 a9d11f81 2021-10-08 op #include <stdlib.h>
 80 a9d11f81 2021-10-08 op #include <string.h>
 81 a9d11f81 2021-10-08 op #include <unistd.h>
 82 a9d11f81 2021-10-08 op 
 83 a9d11f81 2021-10-08 op /*
 84 a9d11f81 2021-10-08 op  * What's the deal with landlock?  While distro with linux >= 5.13
 85 a9d11f81 2021-10-08 op  * have the struct declarations, libc wrappers are missing.  The
 86 a9d11f81 2021-10-08 op  * sample landlock code provided by the authors includes these "shims"
 87 a9d11f81 2021-10-08 op  * in their example for the landlock API until libc provides them.
 88 a9d11f81 2021-10-08 op  *
 89 a9d11f81 2021-10-08 op  * Linux is such a mess sometimes.  /rant
 90 a9d11f81 2021-10-08 op  */
 91 a9d11f81 2021-10-08 op 
 92 a9d11f81 2021-10-08 op #ifndef landlock_create_ruleset
 93 a9d11f81 2021-10-08 op static inline int
 94 a9d11f81 2021-10-08 op landlock_create_ruleset(const struct landlock_ruleset_attr *attr, size_t size,
 95 a9d11f81 2021-10-08 op     __u32 flags)
 96 a9d11f81 2021-10-08 op {
 97 a9d11f81 2021-10-08 op 	return syscall(__NR_landlock_create_ruleset, attr, size, flags);
 98 a9d11f81 2021-10-08 op }
 99 a9d11f81 2021-10-08 op #endif
100 a9d11f81 2021-10-08 op 
101 a9d11f81 2021-10-08 op #ifndef landlock_add_rule
102 a9d11f81 2021-10-08 op static inline int
103 a9d11f81 2021-10-08 op landlock_add_rule(int ruleset_fd, enum landlock_rule_type type,
104 a9d11f81 2021-10-08 op     const void *attr, __u32 flags)
105 a9d11f81 2021-10-08 op {
106 a9d11f81 2021-10-08 op 	return syscall(__NR_landlock_add_rule, ruleset_fd, type, attr, flags);
107 a9d11f81 2021-10-08 op }
108 a9d11f81 2021-10-08 op #endif
109 a9d11f81 2021-10-08 op 
110 a9d11f81 2021-10-08 op #ifndef landlock_restrict_self
111 a9d11f81 2021-10-08 op static inline int
112 a9d11f81 2021-10-08 op landlock_restrict_self(int ruleset_fd, __u32 flags)
113 a9d11f81 2021-10-08 op {
114 a9d11f81 2021-10-08 op 	return syscall(__NR_landlock_restrict_self, ruleset_fd, flags);
115 a9d11f81 2021-10-08 op }
116 a9d11f81 2021-10-08 op #endif
117 a9d11f81 2021-10-08 op 
118 a9d11f81 2021-10-08 op static int
119 a9d11f81 2021-10-08 op open_landlock(void)
120 a9d11f81 2021-10-08 op {
121 a9d11f81 2021-10-08 op 	struct landlock_ruleset_attr attr = {
122 a9d11f81 2021-10-08 op 		.handled_access_fs =	LANDLOCK_ACCESS_FS_READ_FILE	|
123 a9d11f81 2021-10-08 op 					LANDLOCK_ACCESS_FS_READ_DIR	|
124 a9d11f81 2021-10-08 op 					LANDLOCK_ACCESS_FS_WRITE_FILE	|
125 a9d11f81 2021-10-08 op 					LANDLOCK_ACCESS_FS_MAKE_DIR	|
126 a9d11f81 2021-10-08 op 					LANDLOCK_ACCESS_FS_MAKE_REG,
127 a9d11f81 2021-10-08 op 	};
128 a9d11f81 2021-10-08 op 
129 a9d11f81 2021-10-08 op 	return landlock_create_ruleset(&attr, sizeof(attr), 0);
130 a9d11f81 2021-10-08 op }
131 a9d11f81 2021-10-08 op 
132 a9d11f81 2021-10-08 op static int
133 a9d11f81 2021-10-08 op landlock_unveil(int landlock_fd, const char *path, int perms)
134 a9d11f81 2021-10-08 op {
135 a9d11f81 2021-10-08 op 	struct landlock_path_beneath_attr pb;
136 a9d11f81 2021-10-08 op 	int err, saved_errno;
137 a9d11f81 2021-10-08 op 
138 a9d11f81 2021-10-08 op 	pb.allowed_access = perms;
139 a9d11f81 2021-10-08 op 
140 a9d11f81 2021-10-08 op 	if ((pb.parent_fd = open(path, O_PATH)) == -1)
141 a9d11f81 2021-10-08 op 		return -1;
142 a9d11f81 2021-10-08 op 
143 a9d11f81 2021-10-08 op 	err = landlock_add_rule(landlock_fd, LANDLOCK_RULE_PATH_BENEATH,
144 a9d11f81 2021-10-08 op 	    &pb, 0);
145 a9d11f81 2021-10-08 op 	saved_errno = errno;
146 a9d11f81 2021-10-08 op 	close(pb.parent_fd);
147 a9d11f81 2021-10-08 op 	errno = saved_errno;
148 a9d11f81 2021-10-08 op 	return err ? -1 : 0;
149 a9d11f81 2021-10-08 op }
150 a9d11f81 2021-10-08 op 
151 a9d11f81 2021-10-08 op static int
152 a9d11f81 2021-10-08 op landlock_apply(int fd)
153 a9d11f81 2021-10-08 op {
154 a9d11f81 2021-10-08 op 	int r, saved_errno;
155 a9d11f81 2021-10-08 op 
156 a9d11f81 2021-10-08 op 	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1)
157 a9d11f81 2021-10-08 op 		err(1, "%s: prctl(PR_SET_NO_NEW_PRIVS)", __func__);
158 a9d11f81 2021-10-08 op 
159 a9d11f81 2021-10-08 op 	r = landlock_restrict_self(fd, 0);
160 a9d11f81 2021-10-08 op 	saved_errno = errno;
161 a9d11f81 2021-10-08 op 	close(fd);
162 a9d11f81 2021-10-08 op 	errno = saved_errno;
163 a9d11f81 2021-10-08 op 	return r ? -1 : 0;
164 a9d11f81 2021-10-08 op }
165 a9d11f81 2021-10-08 op 
166 a9d11f81 2021-10-08 op static int
167 a9d11f81 2021-10-08 op landlock_no_fs(void)
168 a9d11f81 2021-10-08 op {
169 a9d11f81 2021-10-08 op 	int fd;
170 a9d11f81 2021-10-08 op 
171 a9d11f81 2021-10-08 op 	if ((fd = open_landlock()) == -1)
172 a9d11f81 2021-10-08 op 		return -1;
173 a9d11f81 2021-10-08 op 
174 a9d11f81 2021-10-08 op 	return landlock_apply(fd);
175 a9d11f81 2021-10-08 op }
176 a9d11f81 2021-10-08 op 
177 a9d11f81 2021-10-08 op void
178 a9d11f81 2021-10-08 op sandbox_net_process(void)
179 a9d11f81 2021-10-08 op {
180 a9d11f81 2021-10-08 op 	return;
181 a9d11f81 2021-10-08 op }
182 a9d11f81 2021-10-08 op 
183 a9d11f81 2021-10-08 op void
184 a9d11f81 2021-10-08 op sandbox_ui_process(void)
185 a9d11f81 2021-10-08 op {
186 a9d11f81 2021-10-08 op 	if (landlock_no_fs() == -1)
187 a9d11f81 2021-10-08 op 		err(1, "landlock");
188 a9d11f81 2021-10-08 op }
189 a9d11f81 2021-10-08 op 
190 a9d11f81 2021-10-08 op void
191 a9d11f81 2021-10-08 op sandbox_fs_process(void)
192 a9d11f81 2021-10-08 op {
193 a9d11f81 2021-10-08 op 	int fd, rwc;
194 a9d11f81 2021-10-08 op         char path[PATH_MAX];
195 a9d11f81 2021-10-08 op 
196 a9d11f81 2021-10-08 op 	if ((fd = open_landlock()) == -1)
197 a9d11f81 2021-10-08 op 		err(1, "can't create landlock ruleset");
198 a9d11f81 2021-10-08 op 
199 a9d11f81 2021-10-08 op 	rwc =	LANDLOCK_ACCESS_FS_READ_FILE	|
200 a9d11f81 2021-10-08 op 		LANDLOCK_ACCESS_FS_READ_DIR	|
201 a9d11f81 2021-10-08 op 		LANDLOCK_ACCESS_FS_WRITE_FILE	|
202 a9d11f81 2021-10-08 op 		LANDLOCK_ACCESS_FS_MAKE_DIR	|
203 a9d11f81 2021-10-08 op 		LANDLOCK_ACCESS_FS_MAKE_REG;
204 a9d11f81 2021-10-08 op 
205 a9d11f81 2021-10-08 op 	if (landlock_unveil(fd, "/tmp", rwc) == -1)
206 a9d11f81 2021-10-08 op 		err(1, "landlock_unveil(/tmp)");
207 a9d11f81 2021-10-08 op 
208 a9d11f81 2021-10-08 op 	strlcpy(path, getenv("HOME"), sizeof(path));
209 a9d11f81 2021-10-08 op 	strlcat(path, "/Downloads", sizeof(path));
210 a9d11f81 2021-10-08 op 	if (landlock_unveil(fd, path, rwc) == -1)
211 a9d11f81 2021-10-08 op 		err(1, "landlock_unveil(%s)", path);
212 a9d11f81 2021-10-08 op 
213 a9d11f81 2021-10-08 op 	if (landlock_unveil(fd, config_path_base, rwc) == -1)
214 a9d11f81 2021-10-08 op 		err(1, "landlock_unveil(%s)", config_path_base);
215 a9d11f81 2021-10-08 op 
216 a9d11f81 2021-10-08 op 	if (landlock_unveil(fd, data_path_base, rwc) == -1)
217 a9d11f81 2021-10-08 op 		err(1, "landlock_unveil(%s)", data_path_base);
218 a9d11f81 2021-10-08 op 
219 a9d11f81 2021-10-08 op 	if (landlock_unveil(fd, cache_path_base, rwc) == -1)
220 a9d11f81 2021-10-08 op 		err(1, "landlock_unveil(%s)", cache_path_base);
221 a9d11f81 2021-10-08 op }
222 a9d11f81 2021-10-08 op 
223 68a9b7d2 2021-03-13 op #else
224 68a9b7d2 2021-03-13 op 
225 68a9b7d2 2021-03-13 op #warning "No sandbox for this OS"
226 68a9b7d2 2021-03-13 op 
227 68a9b7d2 2021-03-13 op void
228 17c10c65 2021-07-12 op sandbox_net_process(void)
229 68a9b7d2 2021-03-13 op {
230 68a9b7d2 2021-03-13 op 	return;
231 68a9b7d2 2021-03-13 op }
232 68a9b7d2 2021-03-13 op 
233 35e1f40a 2021-03-14 op void
234 35e1f40a 2021-03-14 op sandbox_ui_process(void)
235 35e1f40a 2021-03-14 op {
236 35e1f40a 2021-03-14 op 	return;
237 35e1f40a 2021-03-14 op }
238 35e1f40a 2021-03-14 op 
239 35e1f40a 2021-03-14 op void
240 35e1f40a 2021-03-14 op sandbox_fs_process(void)
241 35e1f40a 2021-03-14 op {
242 35e1f40a 2021-03-14 op 	return;
243 35e1f40a 2021-03-14 op }
244 35e1f40a 2021-03-14 op 
245 677d90f7 2021-03-12 op #endif