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
|
#include "config.h"
#include <seccomp.h>
#include <termios.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <signal.h>
#include <string.h>
#include "memcached.h"
static char *kill_msg;
// Make sure to preserve the ??? position in the string, or correct the offsets
// in the syssig handler.
#define KILL_MSG_STR "Seccomp policy failure. Caught syscall ???. This is " \
"either an exploit attempt, or your system is not supported yet.\n"
static void handle_syssig(int signum, siginfo_t *si, void *thread_context) {
#if defined(si_syscall)
int syscall_no = si->si_syscall;
#else
// If system has no support for si_syscal, the information may not be
// precise.
int syscall_no = si->si_value.sival_int;
#endif
// Replace the characters in the kill message with the syscall number. We
// can't safely printf (even write is not really valid, but we're crashing
// anyway).
kill_msg[39] = (syscall_no / 100) % 10 + '0';
kill_msg[40] = (syscall_no / 10) % 10 + '0';
kill_msg[41] = syscall_no % 10 + '0';
if (write(2, kill_msg, strlen(kill_msg)) == -1) {
// An error occurred, but we can't do anything about it here. This check
// is mostly to avoid the "ignoring return value of 'write'" error on
// distributions with broken gcc (no "ignore via cast to void" support).
}
// We can't use the nice exit() version because it causes at_exit handlers
// to be looked up and run. We can't take any locks while handling the
// signal, so _exit() is the only thing to do safely.
_exit(EXIT_FAILURE);
}
static const struct sigaction act = {
.sa_sigaction = handle_syssig,
.sa_flags = SA_SIGINFO,
};
void setup_privilege_violations_handler(void) {
kill_msg = malloc(strlen(KILL_MSG_STR)+1);
strncpy(kill_msg, KILL_MSG_STR, strlen(KILL_MSG_STR)+1);
sigaction(SIGSYS, &act, NULL);
}
// If anything crosses the policy, kill the process.
#define DENY_ACTION SCMP_ACT_TRAP
void drop_privileges(void) {
scmp_filter_ctx ctx = seccomp_init(DENY_ACTION);
if (ctx == NULL) {
return;
}
int rc = 0;
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sigreturn), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigreturn), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigprocmask), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigaction), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(futex), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_wait), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_pwait), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_ctl), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(accept4), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(accept), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(writev), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fstat), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(close), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(munmap), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(shmctl), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(exit), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(exit_group), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(brk), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(ioctl), 1, SCMP_A1(SCMP_CMP_EQ, TIOCGWINSZ));
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(ioctl), 1, SCMP_A1(SCMP_CMP_EQ, TCGETS));
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(msync), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(umask), 0);
#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_MONOTONIC)
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(clock_gettime), 0);
#endif
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(gettimeofday), 0);
#ifdef MEMCACHED_DEBUG
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(read), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(readv), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(lseek), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getpid), 0);
if (settings.relaxed_privileges) {
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(openat), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mkdir), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(access), 0);
}
#endif
if (rc != 0) {
goto fail;
}
rc = seccomp_load(ctx);
if (rc < 0) {
goto fail;
}
seccomp_release(ctx);
return;
fail:
seccomp_release(ctx);
fprintf(stderr, "Failed to set a seccomp profile on the main thread\n");
exit(EXIT_FAILURE);
}
void drop_worker_privileges(void) {
scmp_filter_ctx ctx = seccomp_init(DENY_ACTION);
if (ctx == NULL) {
return;
}
int rc = 0;
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sigreturn), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigreturn), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigprocmask), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(rt_sigaction), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(futex), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_wait), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_pwait), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(epoll_ctl), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(poll), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(read), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(readv), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mprotect), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getpeername), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(close), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(sendmsg), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getrusage), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mmap), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mremap), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(munmap), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(recvfrom), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(brk), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(ioctl), 1, SCMP_A1(SCMP_CMP_EQ, TIOCGWINSZ));
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(msync), 0);
// for spawning the LRU crawler
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(clone), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(set_robust_list), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(madvise), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(exit), 0);
// stat
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getsockname), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getpid), 0);
if (settings.shutdown_command) {
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(tgkill), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(tkill), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(exit_group), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fstat), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(getpid), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(gettid), 0);
}
if (settings.relaxed_privileges) {
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(openat), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(mkdir), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(access), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(open), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(fcntl), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(lseek), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(writev), 0);
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(socket), 0);
} else {
// stdout
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 1, SCMP_A0(SCMP_CMP_EQ, 1));
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(writev), 1, SCMP_A0(SCMP_CMP_EQ, 1));
// stderr
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 1, SCMP_A0(SCMP_CMP_EQ, 2));
rc |= seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(writev), 1, SCMP_A0(SCMP_CMP_EQ, 2));
}
if (rc != 0) {
goto fail;
}
rc = seccomp_load(ctx);
if (rc < 0) {
goto fail;
}
seccomp_release(ctx);
return;
fail:
seccomp_release(ctx);
fprintf(stderr, "Failed to set a seccomp profile on a worker thread\n");
exit(EXIT_FAILURE);
}
|
