Merge remote-tracking branch 'remotes/rth/tags/pull-tcg-20210921' into staging
[qemu.git] / softmmu / 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 denylist[] = {
49 /* default set of syscalls that should get blocked */
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(setpriority), QEMU_SECCOMP_SET_RESOURCECTL },
101 { SCMP_SYS(sched_setparam), QEMU_SECCOMP_SET_RESOURCECTL },
102 { SCMP_SYS(sched_setscheduler), QEMU_SECCOMP_SET_RESOURCECTL,
103 ARRAY_SIZE(sched_setscheduler_arg), sched_setscheduler_arg },
104 { SCMP_SYS(sched_setaffinity), QEMU_SECCOMP_SET_RESOURCECTL },
105 };
106
107 static inline __attribute__((unused)) int
108 qemu_seccomp(unsigned int operation, unsigned int flags, void *args)
109 {
110 #ifdef __NR_seccomp
111 return syscall(__NR_seccomp, operation, flags, args);
112 #else
113 errno = ENOSYS;
114 return -1;
115 #endif
116 }
117
118 static uint32_t qemu_seccomp_get_action(int set)
119 {
120 switch (set) {
121 case QEMU_SECCOMP_SET_DEFAULT:
122 case QEMU_SECCOMP_SET_OBSOLETE:
123 case QEMU_SECCOMP_SET_PRIVILEGED:
124 case QEMU_SECCOMP_SET_SPAWN: {
125 #if defined(SECCOMP_GET_ACTION_AVAIL) && defined(SCMP_ACT_KILL_PROCESS) && \
126 defined(SECCOMP_RET_KILL_PROCESS)
127 static int kill_process = -1;
128 if (kill_process == -1) {
129 uint32_t action = SECCOMP_RET_KILL_PROCESS;
130
131 if (qemu_seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &action) == 0) {
132 kill_process = 1;
133 } else {
134 kill_process = 0;
135 }
136 }
137 if (kill_process == 1) {
138 return SCMP_ACT_KILL_PROCESS;
139 }
140 #endif
141 return SCMP_ACT_TRAP;
142 }
143
144 case QEMU_SECCOMP_SET_RESOURCECTL:
145 return SCMP_ACT_ERRNO(EPERM);
146
147 default:
148 g_assert_not_reached();
149 }
150 }
151
152
153 static int seccomp_start(uint32_t seccomp_opts, Error **errp)
154 {
155 int rc = -1;
156 unsigned int i = 0;
157 scmp_filter_ctx ctx;
158
159 ctx = seccomp_init(SCMP_ACT_ALLOW);
160 if (ctx == NULL) {
161 error_setg(errp, "failed to initialize seccomp context");
162 goto seccomp_return;
163 }
164
165 rc = seccomp_attr_set(ctx, SCMP_FLTATR_CTL_TSYNC, 1);
166 if (rc != 0) {
167 error_setg_errno(errp, -rc,
168 "failed to set seccomp thread synchronization");
169 goto seccomp_return;
170 }
171
172 for (i = 0; i < ARRAY_SIZE(denylist); i++) {
173 uint32_t action;
174 if (!(seccomp_opts & denylist[i].set)) {
175 continue;
176 }
177
178 action = qemu_seccomp_get_action(denylist[i].set);
179 rc = seccomp_rule_add_array(ctx, action, denylist[i].num,
180 denylist[i].narg, denylist[i].arg_cmp);
181 if (rc < 0) {
182 error_setg_errno(errp, -rc,
183 "failed to add seccomp denylist rules");
184 goto seccomp_return;
185 }
186 }
187
188 rc = seccomp_load(ctx);
189 if (rc < 0) {
190 error_setg_errno(errp, -rc,
191 "failed to load seccomp syscall filter in kernel");
192 }
193
194 seccomp_return:
195 seccomp_release(ctx);
196 return rc < 0 ? -1 : 0;
197 }
198
199 int parse_sandbox(void *opaque, QemuOpts *opts, Error **errp)
200 {
201 if (qemu_opt_get_bool(opts, "enable", false)) {
202 uint32_t seccomp_opts = QEMU_SECCOMP_SET_DEFAULT
203 | QEMU_SECCOMP_SET_OBSOLETE;
204 const char *value = NULL;
205
206 value = qemu_opt_get(opts, "obsolete");
207 if (value) {
208 if (g_str_equal(value, "allow")) {
209 seccomp_opts &= ~QEMU_SECCOMP_SET_OBSOLETE;
210 } else if (g_str_equal(value, "deny")) {
211 /* this is the default option, this if is here
212 * to provide a little bit of consistency for
213 * the command line */
214 } else {
215 error_setg(errp, "invalid argument for obsolete");
216 return -1;
217 }
218 }
219
220 value = qemu_opt_get(opts, "elevateprivileges");
221 if (value) {
222 if (g_str_equal(value, "deny")) {
223 seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED;
224 } else if (g_str_equal(value, "children")) {
225 seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED;
226
227 /* calling prctl directly because we're
228 * not sure if host has CAP_SYS_ADMIN set*/
229 if (prctl(PR_SET_NO_NEW_PRIVS, 1)) {
230 error_setg(errp, "failed to set no_new_privs aborting");
231 return -1;
232 }
233 } else if (g_str_equal(value, "allow")) {
234 /* default value */
235 } else {
236 error_setg(errp, "invalid argument for elevateprivileges");
237 return -1;
238 }
239 }
240
241 value = qemu_opt_get(opts, "spawn");
242 if (value) {
243 if (g_str_equal(value, "deny")) {
244 seccomp_opts |= QEMU_SECCOMP_SET_SPAWN;
245 } else if (g_str_equal(value, "allow")) {
246 /* default value */
247 } else {
248 error_setg(errp, "invalid argument for spawn");
249 return -1;
250 }
251 }
252
253 value = qemu_opt_get(opts, "resourcecontrol");
254 if (value) {
255 if (g_str_equal(value, "deny")) {
256 seccomp_opts |= QEMU_SECCOMP_SET_RESOURCECTL;
257 } else if (g_str_equal(value, "allow")) {
258 /* default value */
259 } else {
260 error_setg(errp, "invalid argument for resourcecontrol");
261 return -1;
262 }
263 }
264
265 if (seccomp_start(seccomp_opts, errp) < 0) {
266 return -1;
267 }
268 }
269
270 return 0;
271 }
272
273 static QemuOptsList qemu_sandbox_opts = {
274 .name = "sandbox",
275 .implied_opt_name = "enable",
276 .head = QTAILQ_HEAD_INITIALIZER(qemu_sandbox_opts.head),
277 .desc = {
278 {
279 .name = "enable",
280 .type = QEMU_OPT_BOOL,
281 },
282 {
283 .name = "obsolete",
284 .type = QEMU_OPT_STRING,
285 },
286 {
287 .name = "elevateprivileges",
288 .type = QEMU_OPT_STRING,
289 },
290 {
291 .name = "spawn",
292 .type = QEMU_OPT_STRING,
293 },
294 {
295 .name = "resourcecontrol",
296 .type = QEMU_OPT_STRING,
297 },
298 { /* end of list */ }
299 },
300 };
301
302 static void seccomp_register(void)
303 {
304 bool add = false;
305
306 /* FIXME: use seccomp_api_get() >= 2 check when released */
307
308 #if defined(SECCOMP_FILTER_FLAG_TSYNC)
309 int check;
310
311 /* check host TSYNC capability, it returns errno == ENOSYS if unavailable */
312 check = qemu_seccomp(SECCOMP_SET_MODE_FILTER,
313 SECCOMP_FILTER_FLAG_TSYNC, NULL);
314 if (check < 0 && errno == EFAULT) {
315 add = true;
316 }
317 #endif
318
319 if (add) {
320 qemu_add_opts(&qemu_sandbox_opts);
321 }
322 }
323 opts_init(seccomp_register);