2 1a49166d 2021-01-23 op * Copyright (c) 2021 Omar Polo <op@omarpolo.com>
4 e29dbd72 2021-01-23 op * Permission to use, copy, modify, and distribute this software for any
5 e29dbd72 2021-01-23 op * purpose with or without fee is hereby granted, provided that the above
6 e29dbd72 2021-01-23 op * copyright notice and this permission notice appear in all copies.
8 e29dbd72 2021-01-23 op * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9 e29dbd72 2021-01-23 op * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 e29dbd72 2021-01-23 op * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 e29dbd72 2021-01-23 op * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 e29dbd72 2021-01-23 op * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 e29dbd72 2021-01-23 op * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 e29dbd72 2021-01-23 op * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 dafb57b8 2021-01-15 op #include "gmid.h"
19 dafb57b8 2021-01-15 op #if defined(__FreeBSD__)
21 dafb57b8 2021-01-15 op #include <sys/capsicum.h>
22 dafb57b8 2021-01-15 op #include <err.h>
27 dafb57b8 2021-01-15 op if (cap_enter() == -1)
28 dafb57b8 2021-01-15 op err(1, "cap_enter");
31 dafb57b8 2021-01-15 op #elif defined(__linux__)
33 71b7eb2f 2021-01-17 op #include <sys/prctl.h>
34 71b7eb2f 2021-01-17 op #include <sys/syscall.h>
35 71b7eb2f 2021-01-17 op #include <sys/syscall.h>
36 71b7eb2f 2021-01-17 op #include <sys/types.h>
38 71b7eb2f 2021-01-17 op #include <linux/audit.h>
39 71b7eb2f 2021-01-17 op #include <linux/filter.h>
40 71b7eb2f 2021-01-17 op #include <linux/seccomp.h>
42 71b7eb2f 2021-01-17 op #include <errno.h>
43 3c0375e4 2021-01-20 op #include <fcntl.h>
44 71b7eb2f 2021-01-17 op #include <stddef.h>
45 71b7eb2f 2021-01-17 op #include <stdio.h>
46 71b7eb2f 2021-01-17 op #include <string.h>
48 71b7eb2f 2021-01-17 op /* thanks chromium' src/seccomp.c */
49 71b7eb2f 2021-01-17 op #if defined(__i386__)
50 71b7eb2f 2021-01-17 op # define SECCOMP_AUDIT_ARCH AUDIT_ARCH_I386
51 71b7eb2f 2021-01-17 op #elif defined(__x86_64__)
52 71b7eb2f 2021-01-17 op # define SECCOMP_AUDIT_ARCH AUDIT_ARCH_X86_64
53 71b7eb2f 2021-01-17 op #elif defined(__arm__)
54 71b7eb2f 2021-01-17 op # define SECCOMP_AUDIT_ARCH AUDIT_ARCH_ARM
55 71b7eb2f 2021-01-17 op #elif defined(__aarch64__)
56 71b7eb2f 2021-01-17 op # define SECCOMP_AUDIT_ARCH AUDIT_ARCH_AARCH64
57 71b7eb2f 2021-01-17 op #elif defined(__mips__)
58 71b7eb2f 2021-01-17 op # if defined(__mips64)
59 71b7eb2f 2021-01-17 op # if defined(__MIPSEB__)
60 71b7eb2f 2021-01-17 op # define SECCOMP_AUDIT_ARCH AUDIT_ARCH_MIPS64
62 71b7eb2f 2021-01-17 op # define SECCOMP_AUDIT_ARCH AUDIT_ARCH_MIPSEL64
65 71b7eb2f 2021-01-17 op # if defined(__MIPSEB__)
66 71b7eb2f 2021-01-17 op # define SECCOMP_AUDIT_ARCH AUDIT_ARCH_MIPS
68 71b7eb2f 2021-01-17 op # define SECCOMP_AUDIT_ARCH AUDIT_ARCH_MIPSEL
72 71b7eb2f 2021-01-17 op # error "Platform does not support seccomp filter yet"
75 71b7eb2f 2021-01-17 op /* uncomment to enable debugging. ONLY FOR DEVELOPMENT */
76 71b7eb2f 2021-01-17 op /* #define SC_DEBUG */
78 71b7eb2f 2021-01-17 op #ifdef SC_DEBUG
79 71b7eb2f 2021-01-17 op # define SC_FAIL SECCOMP_RET_TRAP
81 71b7eb2f 2021-01-17 op # define SC_FAIL SECCOMP_RET_KILL
84 71b7eb2f 2021-01-17 op /* make the filter more readable */
85 71b7eb2f 2021-01-17 op #define SC_ALLOW(nr) \
86 71b7eb2f 2021-01-17 op BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_##nr, 0, 1), \
87 71b7eb2f 2021-01-17 op BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW)
89 71b7eb2f 2021-01-17 op #ifdef SC_DEBUG
91 71b7eb2f 2021-01-17 op #include <signal.h>
92 71b7eb2f 2021-01-17 op #include <unistd.h>
95 71b7eb2f 2021-01-17 op sandbox_seccomp_violation(int signum, siginfo_t *info, void *ctx)
100 71b7eb2f 2021-01-17 op fprintf(stderr, "%s: unexpected system call (arch:0x%x,syscall:%d @ %p)\n",
101 71b7eb2f 2021-01-17 op __func__, info->si_arch, info->si_syscall, info->si_call_addr);
106 71b7eb2f 2021-01-17 op sandbox_seccomp_catch_sigsys(void)
108 71b7eb2f 2021-01-17 op struct sigaction act;
109 71b7eb2f 2021-01-17 op sigset_t mask;
111 71b7eb2f 2021-01-17 op memset(&act, 0, sizeof(act));
112 71b7eb2f 2021-01-17 op sigemptyset(&mask);
113 71b7eb2f 2021-01-17 op sigaddset(&mask, SIGSYS);
115 71b7eb2f 2021-01-17 op act.sa_sigaction = &sandbox_seccomp_violation;
116 71b7eb2f 2021-01-17 op act.sa_flags = SA_SIGINFO;
117 71b7eb2f 2021-01-17 op if (sigaction(SIGSYS, &act, NULL) == -1) {
118 71b7eb2f 2021-01-17 op fprintf(stderr, "%s: sigaction(SIGSYS): %s\n",
119 71b7eb2f 2021-01-17 op __func__, strerror(errno));
122 71b7eb2f 2021-01-17 op if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1) {
123 71b7eb2f 2021-01-17 op fprintf(stderr, "%s: sigprocmask(SIGSYS): %s\n",
124 71b7eb2f 2021-01-17 op __func__, strerror(errno));
128 71b7eb2f 2021-01-17 op #endif /* SC_DEBUG */
133 71b7eb2f 2021-01-17 op struct sock_filter filter[] = {
134 71b7eb2f 2021-01-17 op /* load the *current* architecture */
135 71b7eb2f 2021-01-17 op BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
136 71b7eb2f 2021-01-17 op (offsetof(struct seccomp_data, arch))),
137 71b7eb2f 2021-01-17 op /* ensure it's the same that we've been compiled on */
138 71b7eb2f 2021-01-17 op BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K,
139 71b7eb2f 2021-01-17 op SECCOMP_AUDIT_ARCH, 1, 0),
140 71b7eb2f 2021-01-17 op /* if not, kill the program */
141 71b7eb2f 2021-01-17 op BPF_STMT(BPF_RET | BPF_K, SC_FAIL),
143 71b7eb2f 2021-01-17 op /* load the syscall number */
144 71b7eb2f 2021-01-17 op BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
145 71b7eb2f 2021-01-17 op (offsetof(struct seccomp_data, nr))),
147 71b7eb2f 2021-01-17 op /* allow logging on stdout */
148 71b7eb2f 2021-01-17 op SC_ALLOW(write),
149 71b7eb2f 2021-01-17 op SC_ALLOW(writev),
150 71b7eb2f 2021-01-17 op SC_ALLOW(readv),
152 71b7eb2f 2021-01-17 op /* these are used to serve the files. note how we
153 71b7eb2f 2021-01-17 op * allow openat but not open. */
155 298e4b96 2021-01-20 op #ifdef __aarch64__
156 298e4b96 2021-01-20 op /* it seems that on aarch64 there isn't a poll(2)
157 298e4b96 2021-01-20 op * syscall, but instead it's implemented on top of
158 298e4b96 2021-01-20 op * ppoll(2). */
159 298e4b96 2021-01-20 op SC_ALLOW(ppoll),
161 65fba1d5 2021-01-17 op SC_ALLOW(poll),
163 71b7eb2f 2021-01-17 op SC_ALLOW(accept),
164 71b7eb2f 2021-01-17 op SC_ALLOW(read),
165 71b7eb2f 2021-01-17 op SC_ALLOW(openat),
166 71b7eb2f 2021-01-17 op SC_ALLOW(fstat),
167 71b7eb2f 2021-01-17 op SC_ALLOW(close),
168 71b7eb2f 2021-01-17 op SC_ALLOW(lseek),
169 71b7eb2f 2021-01-17 op SC_ALLOW(brk),
170 71b7eb2f 2021-01-17 op SC_ALLOW(mmap),
171 71b7eb2f 2021-01-17 op SC_ALLOW(munmap),
173 71b7eb2f 2021-01-17 op /* we need recvmsg to receive fd */
174 71b7eb2f 2021-01-17 op SC_ALLOW(recvmsg),
176 71b7eb2f 2021-01-17 op /* XXX: ??? */
177 71b7eb2f 2021-01-17 op SC_ALLOW(getpid),
179 f2b3a519 2021-01-20 op /* alpine on amd64 does a clock_gettime(2) */
180 f2b3a519 2021-01-20 op SC_ALLOW(clock_gettime),
182 71b7eb2f 2021-01-17 op SC_ALLOW(exit),
183 71b7eb2f 2021-01-17 op SC_ALLOW(exit_group),
185 f2b3a519 2021-01-20 op /* allow only F_GETFL and F_SETFL fcntl */
186 3c0375e4 2021-01-20 op BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_fcntl, 0, 6),
187 de4f7131 2021-01-20 op BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
188 3c0375e4 2021-01-20 op (offsetof(struct seccomp_data, args[1]))),
189 3c0375e4 2021-01-20 op BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, F_GETFL, 0, 1),
190 3c0375e4 2021-01-20 op BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
191 3c0375e4 2021-01-20 op BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, F_SETFL, 0, 1),
192 3c0375e4 2021-01-20 op BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
193 3c0375e4 2021-01-20 op BPF_STMT(BPF_RET | BPF_K, SC_FAIL),
195 f2b3a519 2021-01-20 op /* re-load the syscall number */
196 de4f7131 2021-01-20 op BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
197 de4f7131 2021-01-20 op (offsetof(struct seccomp_data, nr))),
199 71b7eb2f 2021-01-17 op /* allow ioctl but only on fd 1, glibc doing stuff? */
200 71b7eb2f 2021-01-17 op BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_ioctl, 0, 3),
201 71b7eb2f 2021-01-17 op BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
202 71b7eb2f 2021-01-17 op (offsetof(struct seccomp_data, args[0]))),
203 71b7eb2f 2021-01-17 op BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 1, 0, 1),
204 71b7eb2f 2021-01-17 op BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
206 71b7eb2f 2021-01-17 op /* disallow enything else */
207 71b7eb2f 2021-01-17 op BPF_STMT(BPF_RET | BPF_K, SC_FAIL),
210 71b7eb2f 2021-01-17 op struct sock_fprog prog = {
211 71b7eb2f 2021-01-17 op .len = (unsigned short) (sizeof(filter) / sizeof(filter[0])),
212 71b7eb2f 2021-01-17 op .filter = filter,
215 71b7eb2f 2021-01-17 op #ifdef SC_DEBUG
216 71b7eb2f 2021-01-17 op sandbox_seccomp_catch_sigsys();
219 71b7eb2f 2021-01-17 op if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) {
220 71b7eb2f 2021-01-17 op fprintf(stderr, "%s: prctl(PR_SET_NO_NEW_PRIVS): %s\n",
221 71b7eb2f 2021-01-17 op __func__, strerror(errno));
225 71b7eb2f 2021-01-17 op if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog) == -1) {
226 71b7eb2f 2021-01-17 op fprintf(stderr, "%s: prctl(PR_SET_SECCOMP): %s\n",
227 71b7eb2f 2021-01-17 op __func__, strerror(errno));
232 dafb57b8 2021-01-15 op #elif defined(__OpenBSD__)
234 dafb57b8 2021-01-15 op #include <err.h>
235 dafb57b8 2021-01-15 op #include <unistd.h>
240 dafb57b8 2021-01-15 op struct vhost *h;
242 dafb57b8 2021-01-15 op for (h = hosts; h->domain != NULL; ++h) {
243 dafb57b8 2021-01-15 op if (unveil(h->dir, "rx") == -1)
244 dafb57b8 2021-01-15 op err(1, "unveil %s for domain %s", h->dir, h->domain);
247 881a9dd9 2021-01-16 op if (pledge("stdio recvfd rpath inet", NULL) == -1)
248 dafb57b8 2021-01-15 op err(1, "pledge");
256 dafb57b8 2021-01-15 op LOGN(NULL, "%s", "no sandbox method known for this OS");