Update version for v4.2.0 release
[qemu.git] / qemu-seccomp.c
1 /*
2 * QEMU seccomp mode 2 support with libseccomp
3 *
4 * Copyright IBM, Corp. 2012
5 *
6 * Authors:
7 * Eduardo Otubo <eotubo@br.ibm.com>
8 *
9 * This work is licensed under the terms of the GNU GPL, version 2. See
10 * the COPYING file in the top-level directory.
11 *
12 * Contributions after 2012-01-13 are licensed under the terms of the
13 * GNU GPL, version 2 or (at your option) any later version.
14 */
15
16 #include "qemu/osdep.h"
17 #include "qapi/error.h"
18 #include "qemu/config-file.h"
19 #include "qemu/option.h"
20 #include "qemu/module.h"
21 #include <sys/prctl.h>
22 #include <seccomp.h>
23 #include "sysemu/seccomp.h"
24 #include <linux/seccomp.h>
25
26 /* For some architectures (notably ARM) cacheflush is not supported until
27 * libseccomp 2.2.3, but configure enforces that we are using a more recent
28 * version on those hosts, so it is OK for this check to be less strict.
29 */
30 #if SCMP_VER_MAJOR >= 3
31 #define HAVE_CACHEFLUSH
32 #elif SCMP_VER_MAJOR == 2 && SCMP_VER_MINOR >= 2
33 #define HAVE_CACHEFLUSH
34 #endif
35
36 struct QemuSeccompSyscall {
37 int32_t num;
38 uint8_t set;
39 uint8_t narg;
40 const struct scmp_arg_cmp *arg_cmp;
41 };
42
43 const struct scmp_arg_cmp sched_setscheduler_arg[] = {
44 /* was SCMP_A1(SCMP_CMP_NE, SCHED_IDLE), but expanded due to GCC 4.x bug */
45 { .arg = 1, .op = SCMP_CMP_NE, .datum_a = SCHED_IDLE }
46 };
47
48 static const struct QemuSeccompSyscall blacklist[] = {
49 /* default set of syscalls to blacklist */
50 { SCMP_SYS(reboot), QEMU_SECCOMP_SET_DEFAULT },
51 { SCMP_SYS(swapon), QEMU_SECCOMP_SET_DEFAULT },
52 { SCMP_SYS(swapoff), QEMU_SECCOMP_SET_DEFAULT },
53 { SCMP_SYS(syslog), QEMU_SECCOMP_SET_DEFAULT },
54 { SCMP_SYS(mount), QEMU_SECCOMP_SET_DEFAULT },
55 { SCMP_SYS(umount), QEMU_SECCOMP_SET_DEFAULT },
56 { SCMP_SYS(kexec_load), QEMU_SECCOMP_SET_DEFAULT },
57 { SCMP_SYS(afs_syscall), QEMU_SECCOMP_SET_DEFAULT },
58 { SCMP_SYS(break), QEMU_SECCOMP_SET_DEFAULT },
59 { SCMP_SYS(ftime), QEMU_SECCOMP_SET_DEFAULT },
60 { SCMP_SYS(getpmsg), QEMU_SECCOMP_SET_DEFAULT },
61 { SCMP_SYS(gtty), QEMU_SECCOMP_SET_DEFAULT },
62 { SCMP_SYS(lock), QEMU_SECCOMP_SET_DEFAULT },
63 { SCMP_SYS(mpx), QEMU_SECCOMP_SET_DEFAULT },
64 { SCMP_SYS(prof), QEMU_SECCOMP_SET_DEFAULT },
65 { SCMP_SYS(profil), QEMU_SECCOMP_SET_DEFAULT },
66 { SCMP_SYS(putpmsg), QEMU_SECCOMP_SET_DEFAULT },
67 { SCMP_SYS(security), QEMU_SECCOMP_SET_DEFAULT },
68 { SCMP_SYS(stty), QEMU_SECCOMP_SET_DEFAULT },
69 { SCMP_SYS(tuxcall), QEMU_SECCOMP_SET_DEFAULT },
70 { SCMP_SYS(ulimit), QEMU_SECCOMP_SET_DEFAULT },
71 { SCMP_SYS(vserver), QEMU_SECCOMP_SET_DEFAULT },
72 /* obsolete */
73 { SCMP_SYS(readdir), QEMU_SECCOMP_SET_OBSOLETE },
74 { SCMP_SYS(_sysctl), QEMU_SECCOMP_SET_OBSOLETE },
75 { SCMP_SYS(bdflush), QEMU_SECCOMP_SET_OBSOLETE },
76 { SCMP_SYS(create_module), QEMU_SECCOMP_SET_OBSOLETE },
77 { SCMP_SYS(get_kernel_syms), QEMU_SECCOMP_SET_OBSOLETE },
78 { SCMP_SYS(query_module), QEMU_SECCOMP_SET_OBSOLETE },
79 { SCMP_SYS(sgetmask), QEMU_SECCOMP_SET_OBSOLETE },
80 { SCMP_SYS(ssetmask), QEMU_SECCOMP_SET_OBSOLETE },
81 { SCMP_SYS(sysfs), QEMU_SECCOMP_SET_OBSOLETE },
82 { SCMP_SYS(uselib), QEMU_SECCOMP_SET_OBSOLETE },
83 { SCMP_SYS(ustat), QEMU_SECCOMP_SET_OBSOLETE },
84 /* privileged */
85 { SCMP_SYS(setuid), QEMU_SECCOMP_SET_PRIVILEGED },
86 { SCMP_SYS(setgid), QEMU_SECCOMP_SET_PRIVILEGED },
87 { SCMP_SYS(setpgid), QEMU_SECCOMP_SET_PRIVILEGED },
88 { SCMP_SYS(setsid), QEMU_SECCOMP_SET_PRIVILEGED },
89 { SCMP_SYS(setreuid), QEMU_SECCOMP_SET_PRIVILEGED },
90 { SCMP_SYS(setregid), QEMU_SECCOMP_SET_PRIVILEGED },
91 { SCMP_SYS(setresuid), QEMU_SECCOMP_SET_PRIVILEGED },
92 { SCMP_SYS(setresgid), QEMU_SECCOMP_SET_PRIVILEGED },
93 { SCMP_SYS(setfsuid), QEMU_SECCOMP_SET_PRIVILEGED },
94 { SCMP_SYS(setfsgid), QEMU_SECCOMP_SET_PRIVILEGED },
95 /* spawn */
96 { SCMP_SYS(fork), QEMU_SECCOMP_SET_SPAWN },
97 { SCMP_SYS(vfork), QEMU_SECCOMP_SET_SPAWN },
98 { SCMP_SYS(execve), QEMU_SECCOMP_SET_SPAWN },
99 /* resource control */
100 { SCMP_SYS(getpriority), QEMU_SECCOMP_SET_RESOURCECTL },
101 { SCMP_SYS(setpriority), QEMU_SECCOMP_SET_RESOURCECTL },
102 { SCMP_SYS(sched_setparam), QEMU_SECCOMP_SET_RESOURCECTL },
103 { SCMP_SYS(sched_getparam), QEMU_SECCOMP_SET_RESOURCECTL },
104 { SCMP_SYS(sched_setscheduler), QEMU_SECCOMP_SET_RESOURCECTL,
105 ARRAY_SIZE(sched_setscheduler_arg), sched_setscheduler_arg },
106 { SCMP_SYS(sched_getscheduler), QEMU_SECCOMP_SET_RESOURCECTL },
107 { SCMP_SYS(sched_setaffinity), QEMU_SECCOMP_SET_RESOURCECTL },
108 { SCMP_SYS(sched_getaffinity), QEMU_SECCOMP_SET_RESOURCECTL },
109 { SCMP_SYS(sched_get_priority_max), QEMU_SECCOMP_SET_RESOURCECTL },
110 { SCMP_SYS(sched_get_priority_min), QEMU_SECCOMP_SET_RESOURCECTL },
111 };
112
113 static inline __attribute__((unused)) int
114 qemu_seccomp(unsigned int operation, unsigned int flags, void *args)
115 {
116 #ifdef __NR_seccomp
117 return syscall(__NR_seccomp, operation, flags, args);
118 #else
119 errno = ENOSYS;
120 return -1;
121 #endif
122 }
123
124 static uint32_t qemu_seccomp_get_action(int set)
125 {
126 switch (set) {
127 case QEMU_SECCOMP_SET_DEFAULT:
128 case QEMU_SECCOMP_SET_OBSOLETE:
129 case QEMU_SECCOMP_SET_PRIVILEGED:
130 case QEMU_SECCOMP_SET_SPAWN: {
131 #if defined(SECCOMP_GET_ACTION_AVAIL) && defined(SCMP_ACT_KILL_PROCESS) && \
132 defined(SECCOMP_RET_KILL_PROCESS)
133 static int kill_process = -1;
134 if (kill_process == -1) {
135 uint32_t action = SECCOMP_RET_KILL_PROCESS;
136
137 if (qemu_seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &action) == 0) {
138 kill_process = 1;
139 }
140 kill_process = 0;
141 }
142 if (kill_process == 1) {
143 return SCMP_ACT_KILL_PROCESS;
144 }
145 #endif
146 return SCMP_ACT_TRAP;
147 }
148
149 case QEMU_SECCOMP_SET_RESOURCECTL:
150 return SCMP_ACT_ERRNO(EPERM);
151
152 default:
153 g_assert_not_reached();
154 }
155 }
156
157
158 static int seccomp_start(uint32_t seccomp_opts, Error **errp)
159 {
160 int rc = -1;
161 unsigned int i = 0;
162 scmp_filter_ctx ctx;
163
164 ctx = seccomp_init(SCMP_ACT_ALLOW);
165 if (ctx == NULL) {
166 error_setg(errp, "failed to initialize seccomp context");
167 goto seccomp_return;
168 }
169
170 rc = seccomp_attr_set(ctx, SCMP_FLTATR_CTL_TSYNC, 1);
171 if (rc != 0) {
172 error_setg_errno(errp, -rc,
173 "failed to set seccomp thread synchronization");
174 goto seccomp_return;
175 }
176
177 for (i = 0; i < ARRAY_SIZE(blacklist); i++) {
178 uint32_t action;
179 if (!(seccomp_opts & blacklist[i].set)) {
180 continue;
181 }
182
183 action = qemu_seccomp_get_action(blacklist[i].set);
184 rc = seccomp_rule_add_array(ctx, action, blacklist[i].num,
185 blacklist[i].narg, blacklist[i].arg_cmp);
186 if (rc < 0) {
187 error_setg_errno(errp, -rc,
188 "failed to add seccomp blacklist rules");
189 goto seccomp_return;
190 }
191 }
192
193 rc = seccomp_load(ctx);
194 if (rc < 0) {
195 error_setg_errno(errp, -rc,
196 "failed to load seccomp syscall filter in kernel");
197 }
198
199 seccomp_return:
200 seccomp_release(ctx);
201 return rc < 0 ? -1 : 0;
202 }
203
204 #ifdef CONFIG_SECCOMP
205 int parse_sandbox(void *opaque, QemuOpts *opts, Error **errp)
206 {
207 if (qemu_opt_get_bool(opts, "enable", false)) {
208 uint32_t seccomp_opts = QEMU_SECCOMP_SET_DEFAULT
209 | QEMU_SECCOMP_SET_OBSOLETE;
210 const char *value = NULL;
211
212 value = qemu_opt_get(opts, "obsolete");
213 if (value) {
214 if (g_str_equal(value, "allow")) {
215 seccomp_opts &= ~QEMU_SECCOMP_SET_OBSOLETE;
216 } else if (g_str_equal(value, "deny")) {
217 /* this is the default option, this if is here
218 * to provide a little bit of consistency for
219 * the command line */
220 } else {
221 error_setg(errp, "invalid argument for obsolete");
222 return -1;
223 }
224 }
225
226 value = qemu_opt_get(opts, "elevateprivileges");
227 if (value) {
228 if (g_str_equal(value, "deny")) {
229 seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED;
230 } else if (g_str_equal(value, "children")) {
231 seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED;
232
233 /* calling prctl directly because we're
234 * not sure if host has CAP_SYS_ADMIN set*/
235 if (prctl(PR_SET_NO_NEW_PRIVS, 1)) {
236 error_setg(errp, "failed to set no_new_privs aborting");
237 return -1;
238 }
239 } else if (g_str_equal(value, "allow")) {
240 /* default value */
241 } else {
242 error_setg(errp, "invalid argument for elevateprivileges");
243 return -1;
244 }
245 }
246
247 value = qemu_opt_get(opts, "spawn");
248 if (value) {
249 if (g_str_equal(value, "deny")) {
250 seccomp_opts |= QEMU_SECCOMP_SET_SPAWN;
251 } else if (g_str_equal(value, "allow")) {
252 /* default value */
253 } else {
254 error_setg(errp, "invalid argument for spawn");
255 return -1;
256 }
257 }
258
259 value = qemu_opt_get(opts, "resourcecontrol");
260 if (value) {
261 if (g_str_equal(value, "deny")) {
262 seccomp_opts |= QEMU_SECCOMP_SET_RESOURCECTL;
263 } else if (g_str_equal(value, "allow")) {
264 /* default value */
265 } else {
266 error_setg(errp, "invalid argument for resourcecontrol");
267 return -1;
268 }
269 }
270
271 if (seccomp_start(seccomp_opts, errp) < 0) {
272 return -1;
273 }
274 }
275
276 return 0;
277 }
278
279 static QemuOptsList qemu_sandbox_opts = {
280 .name = "sandbox",
281 .implied_opt_name = "enable",
282 .head = QTAILQ_HEAD_INITIALIZER(qemu_sandbox_opts.head),
283 .desc = {
284 {
285 .name = "enable",
286 .type = QEMU_OPT_BOOL,
287 },
288 {
289 .name = "obsolete",
290 .type = QEMU_OPT_STRING,
291 },
292 {
293 .name = "elevateprivileges",
294 .type = QEMU_OPT_STRING,
295 },
296 {
297 .name = "spawn",
298 .type = QEMU_OPT_STRING,
299 },
300 {
301 .name = "resourcecontrol",
302 .type = QEMU_OPT_STRING,
303 },
304 { /* end of list */ }
305 },
306 };
307
308 static void seccomp_register(void)
309 {
310 bool add = false;
311
312 /* FIXME: use seccomp_api_get() >= 2 check when released */
313
314 #if defined(SECCOMP_FILTER_FLAG_TSYNC)
315 int check;
316
317 /* check host TSYNC capability, it returns errno == ENOSYS if unavailable */
318 check = qemu_seccomp(SECCOMP_SET_MODE_FILTER,
319 SECCOMP_FILTER_FLAG_TSYNC, NULL);
320 if (check < 0 && errno == EFAULT) {
321 add = true;
322 }
323 #endif
324
325 if (add) {
326 qemu_add_opts(&qemu_sandbox_opts);
327 }
328 }
329 opts_init(seccomp_register);
330 #endif