1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
|
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <linux/netlink.h>
#include <sys/capability.h>
#include <sys/socket.h>
#include <sys/types.h>
#if HAVE_SECCOMP
#include <seccomp.h>
#endif
#include "alloc-util.h"
#include "log.h"
#include "nspawn-seccomp.h"
#if HAVE_SECCOMP
#include "seccomp-util.h"
#endif
#include "string-util.h"
#include "strv.h"
#if HAVE_SECCOMP
static int add_syscall_filters(
scmp_filter_ctx ctx,
uint32_t arch,
uint64_t cap_list_retain,
char **syscall_allow_list,
char **syscall_deny_list) {
static const struct {
uint64_t capability;
const char* name;
} allow_list[] = {
/* Let's use set names where we can */
{ 0, "@aio" },
{ 0, "@basic-io" },
{ 0, "@chown" },
{ 0, "@default" },
{ 0, "@file-system" },
{ 0, "@io-event" },
{ 0, "@ipc" },
{ 0, "@mount" },
{ 0, "@network-io" },
{ 0, "@process" },
{ 0, "@resources" },
{ 0, "@setuid" },
{ 0, "@signal" },
{ 0, "@sync" },
{ 0, "@timer" },
/* The following four are sets we optionally enable, in case the caps have been configured for it */
{ CAP_SYS_TIME, "@clock" },
{ CAP_SYS_MODULE, "@module" },
{ CAP_SYS_RAWIO, "@raw-io" },
{ CAP_IPC_LOCK, "@memlock" },
/* Plus a good set of additional syscalls which are not part of any of the groups above */
{ 0, "brk" },
{ 0, "capget" },
{ 0, "capset" },
{ 0, "copy_file_range" },
{ 0, "fadvise64" },
{ 0, "fadvise64_64" },
{ 0, "flock" },
{ 0, "get_mempolicy" },
{ 0, "getcpu" },
{ 0, "getpriority" },
{ 0, "getrandom" },
{ 0, "ioctl" },
{ 0, "ioprio_get" },
{ 0, "kcmp" },
{ 0, "madvise" },
{ 0, "mincore" },
{ 0, "mprotect" },
{ 0, "mremap" },
{ 0, "name_to_handle_at" },
{ 0, "oldolduname" },
{ 0, "olduname" },
{ 0, "personality" },
{ 0, "readahead" },
{ 0, "readdir" },
{ 0, "remap_file_pages" },
{ 0, "sched_get_priority_max" },
{ 0, "sched_get_priority_min" },
{ 0, "sched_getaffinity" },
{ 0, "sched_getattr" },
{ 0, "sched_getparam" },
{ 0, "sched_getscheduler" },
{ 0, "sched_rr_get_interval" },
{ 0, "sched_rr_get_interval_time64" },
{ 0, "sched_yield" },
{ 0, "seccomp" },
{ 0, "sendfile" },
{ 0, "sendfile64" },
{ 0, "setdomainname" },
{ 0, "setfsgid" },
{ 0, "setfsgid32" },
{ 0, "setfsuid" },
{ 0, "setfsuid32" },
{ 0, "sethostname" },
{ 0, "setpgid" },
{ 0, "setsid" },
{ 0, "splice" },
{ 0, "sysinfo" },
{ 0, "tee" },
{ 0, "umask" },
{ 0, "uname" },
{ 0, "userfaultfd" },
{ 0, "vmsplice" },
/* The following individual syscalls are added depending on specified caps */
{ CAP_SYS_PACCT, "acct" },
{ CAP_SYS_PTRACE, "process_vm_readv" },
{ CAP_SYS_PTRACE, "process_vm_writev" },
{ CAP_SYS_PTRACE, "ptrace" },
{ CAP_SYS_BOOT, "reboot" },
{ CAP_SYSLOG, "syslog" },
{ CAP_SYS_TTY_CONFIG, "vhangup" },
/*
* The following syscalls and groups are knowingly excluded:
*
* @cpu-emulation
* @keyring (NB: keyring is not namespaced!)
* @obsolete
* @pkey
* @swap
*
* bpf
* fanotify_init
* fanotify_mark
* kexec_file_load
* kexec_load
* lookup_dcookie
* nfsservctl
* open_by_handle_at
* perf_event_open
* quotactl
*/
};
_cleanup_strv_free_ char **added = NULL;
int r;
for (size_t i = 0; i < ELEMENTSOF(allow_list); i++) {
if (allow_list[i].capability != 0 && (cap_list_retain & (1ULL << allow_list[i].capability)) == 0)
continue;
r = seccomp_add_syscall_filter_item(ctx,
allow_list[i].name,
SCMP_ACT_ALLOW,
syscall_deny_list,
false,
&added);
if (r < 0)
return log_error_errno(r, "Failed to add syscall filter item %s: %m", allow_list[i].name);
}
STRV_FOREACH(p, syscall_allow_list) {
r = seccomp_add_syscall_filter_item(ctx, *p, SCMP_ACT_ALLOW, syscall_deny_list, true, &added);
if (r < 0)
log_warning_errno(r, "Failed to add rule for system call %s on %s, ignoring: %m",
*p, seccomp_arch_to_string(arch));
}
/* The default action is ENOSYS. Respond with EPERM to all other "known" but not allow-listed
* syscalls. */
r = seccomp_add_syscall_filter_item(ctx, "@known", SCMP_ACT_ERRNO(EPERM), added, true, NULL);
if (r < 0)
log_warning_errno(r, "Failed to add rule for @known set on %s, ignoring: %m",
seccomp_arch_to_string(arch));
#if (SCMP_VER_MAJOR == 2 && SCMP_VER_MINOR >= 5) || SCMP_VER_MAJOR > 2
/* We have a large filter here, so let's turn on the binary tree mode if possible. */
r = seccomp_attr_set(ctx, SCMP_FLTATR_CTL_OPTIMIZE, 2);
if (r < 0)
return r;
#endif
return 0;
}
int setup_seccomp(uint64_t cap_list_retain, char **syscall_allow_list, char **syscall_deny_list) {
uint32_t arch;
int r;
if (!is_seccomp_available()) {
log_debug("SECCOMP features not detected in the kernel or disabled at runtime, disabling SECCOMP filtering");
return 0;
}
SECCOMP_FOREACH_LOCAL_ARCH(arch) {
_cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
log_debug("Applying allow list on architecture: %s", seccomp_arch_to_string(arch));
/* We install ENOSYS as the default action, but it will only apply to syscalls which are not
* in the @known set, see above. */
r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ERRNO(ENOSYS));
if (r < 0)
return log_error_errno(r, "Failed to allocate seccomp object: %m");
r = add_syscall_filters(seccomp, arch, cap_list_retain, syscall_allow_list, syscall_deny_list);
if (r < 0)
return r;
r = seccomp_load(seccomp);
if (ERRNO_IS_SECCOMP_FATAL(r))
return log_error_errno(r, "Failed to install seccomp filter: %m");
if (r < 0)
log_debug_errno(r, "Failed to install filter set for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
}
SECCOMP_FOREACH_LOCAL_ARCH(arch) {
_cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
log_debug("Applying NETLINK_AUDIT mask on architecture: %s", seccomp_arch_to_string(arch));
r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ALLOW);
if (r < 0)
return log_error_errno(r, "Failed to allocate seccomp object: %m");
/*
Audit is broken in containers, much of the userspace audit hookup will fail if running inside a
container. We don't care and just turn off creation of audit sockets.
This will make socket(AF_NETLINK, *, NETLINK_AUDIT) fail with EAFNOSUPPORT which audit userspace uses
as indication that audit is disabled in the kernel.
*/
r = seccomp_rule_add_exact(
seccomp,
SCMP_ACT_ERRNO(EAFNOSUPPORT),
SCMP_SYS(socket),
2,
SCMP_A0(SCMP_CMP_EQ, AF_NETLINK),
SCMP_A2(SCMP_CMP_EQ, NETLINK_AUDIT));
if (r < 0) {
log_debug_errno(r, "Failed to add audit seccomp rule, ignoring: %m");
continue;
}
r = seccomp_load(seccomp);
if (ERRNO_IS_SECCOMP_FATAL(r))
return log_error_errno(r, "Failed to install seccomp audit filter: %m");
if (r < 0)
log_debug_errno(r, "Failed to install filter set for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
}
return 0;
}
#else
int setup_seccomp(uint64_t cap_list_retain, char **syscall_allow_list, char **syscall_deny_list) {
return 0;
}
#endif
|
