OpenCoverage

sandbox-seccomp-filter.c

Absolute File Name:/home/opencoverage/opencoverage/guest-scripts/openssh/src/sandbox-seccomp-filter.c
Source codeSwitch to Preprocessed file
LineSourceCount
1/*-
2 * Copyright (c) 2012 Will Drewry <wad@dataspill.org>-
3 *-
4 * Permission to use, copy, modify, and distribute this software for any-
5 * purpose with or without fee is hereby granted, provided that the above-
6 * copyright notice and this permission notice appear in all copies.-
7 *-
8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES-
9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF-
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR-
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES-
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN-
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF-
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.-
15 */-
16-
17/*-
18 * Uncomment the SANDBOX_SECCOMP_FILTER_DEBUG macro below to help diagnose-
19 * filter breakage during development. *Do not* use this in production,-
20 * as it relies on making library calls that are unsafe in signal context.-
21 *-
22 * Instead, live systems the auditctl(8) may be used to monitor failures.-
23 * E.g.-
24 * auditctl -a task,always -F uid=<privsep uid>-
25 */-
26/* #define SANDBOX_SECCOMP_FILTER_DEBUG 1 */-
27-
28/* XXX it should be possible to do logging via the log socket safely */-
29-
30#ifdef SANDBOX_SECCOMP_FILTER_DEBUG-
31/* Use the kernel headers in case of an older toolchain. */-
32# include <asm/siginfo.h>-
33# define __have_siginfo_t 1-
34# define __have_sigval_t 1-
35# define __have_sigevent_t 1-
36#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */-
37-
38#include "includes.h"-
39-
40#ifdef SANDBOX_SECCOMP_FILTER-
41-
42#include <sys/types.h>-
43#include <sys/resource.h>-
44#include <sys/prctl.h>-
45-
46#include <linux/net.h>-
47#include <linux/audit.h>-
48#include <linux/filter.h>-
49#include <linux/seccomp.h>-
50#include <elf.h>-
51-
52#include <asm/unistd.h>-
53#ifdef __s390__-
54#include <asm/zcrypt.h>-
55#endif-
56-
57#include <errno.h>-
58#include <signal.h>-
59#include <stdarg.h>-
60#include <stddef.h> /* for offsetof */-
61#include <stdio.h>-
62#include <stdlib.h>-
63#include <string.h>-
64#include <unistd.h>-
65-
66#include "log.h"-
67#include "ssh-sandbox.h"-
68#include "xmalloc.h"-
69-
70/* Linux seccomp_filter sandbox */-
71#define SECCOMP_FILTER_FAIL SECCOMP_RET_KILL-
72-
73/* Use a signal handler to emit violations when debugging */-
74#ifdef SANDBOX_SECCOMP_FILTER_DEBUG-
75# undef SECCOMP_FILTER_FAIL-
76# define SECCOMP_FILTER_FAIL SECCOMP_RET_TRAP-
77#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */-
78-
79#if __BYTE_ORDER == __LITTLE_ENDIAN-
80# define ARG_LO_OFFSET 0-
81# define ARG_HI_OFFSET sizeof(uint32_t)-
82#elif __BYTE_ORDER == __BIG_ENDIAN-
83# define ARG_LO_OFFSET sizeof(uint32_t)-
84# define ARG_HI_OFFSET 0-
85#else-
86#error "Unknown endianness"-
87#endif-
88-
89/* Simple helpers to avoid manual errors (but larger BPF programs). */-
90#define SC_DENY(_nr, _errno) \-
91 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 1), \-
92 BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ERRNO|(_errno))-
93#define SC_ALLOW(_nr) \-
94 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 1), \-
95 BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW)-
96#define SC_ALLOW_ARG(_nr, _arg_nr, _arg_val) \-
97 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 6), \-
98 /* load and test first syscall argument, low word */ \-
99 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \-
100 offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_LO_OFFSET), \-
101 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, \-
102 ((_arg_val) & 0xFFFFFFFF), 0, 3), \-
103 /* load and test first syscall argument, high word */ \-
104 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \-
105 offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_HI_OFFSET), \-
106 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, \-
107 (((uint32_t)((uint64_t)(_arg_val) >> 32)) & 0xFFFFFFFF), 0, 1), \-
108 BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), \-
109 /* reload syscall number; all rules expect it in accumulator */ \-
110 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \-
111 offsetof(struct seccomp_data, nr))-
112-
113/* Syscall filtering set for preauth. */-
114static const struct sock_filter preauth_insns[] = {-
115 /* Ensure the syscall arch convention is as expected. */-
116 BPF_STMT(BPF_LD+BPF_W+BPF_ABS,-
117 offsetof(struct seccomp_data, arch)),-
118 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, SECCOMP_AUDIT_ARCH, 1, 0),-
119 BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),-
120 /* Load the syscall number for checking. */-
121 BPF_STMT(BPF_LD+BPF_W+BPF_ABS,-
122 offsetof(struct seccomp_data, nr)),-
123-
124 /* Syscalls to non-fatally deny */-
125#ifdef __NR_lstat-
126 SC_DENY(__NR_lstat, EACCES),-
127#endif-
128#ifdef __NR_lstat64-
129 SC_DENY(__NR_lstat64, EACCES),-
130#endif-
131#ifdef __NR_fstat-
132 SC_DENY(__NR_fstat, EACCES),-
133#endif-
134#ifdef __NR_fstat64-
135 SC_DENY(__NR_fstat64, EACCES),-
136#endif-
137#ifdef __NR_open-
138 SC_DENY(__NR_open, EACCES),-
139#endif-
140#ifdef __NR_openat-
141 SC_DENY(__NR_openat, EACCES),-
142#endif-
143#ifdef __NR_newfstatat-
144 SC_DENY(__NR_newfstatat, EACCES),-
145#endif-
146#ifdef __NR_stat-
147 SC_DENY(__NR_stat, EACCES),-
148#endif-
149#ifdef __NR_stat64-
150 SC_DENY(__NR_stat64, EACCES),-
151#endif-
152-
153 /* Syscalls to permit */-
154#ifdef __NR_brk-
155 SC_ALLOW(__NR_brk),-
156#endif-
157#ifdef __NR_clock_gettime-
158 SC_ALLOW(__NR_clock_gettime),-
159#endif-
160#ifdef __NR_close-
161 SC_ALLOW(__NR_close),-
162#endif-
163#ifdef __NR_exit-
164 SC_ALLOW(__NR_exit),-
165#endif-
166#ifdef __NR_exit_group-
167 SC_ALLOW(__NR_exit_group),-
168#endif-
169#ifdef __NR_futex-
170 SC_ALLOW(__NR_futex),-
171#endif-
172#ifdef __NR_geteuid-
173 SC_ALLOW(__NR_geteuid),-
174#endif-
175#ifdef __NR_geteuid32-
176 SC_ALLOW(__NR_geteuid32),-
177#endif-
178#ifdef __NR_getpgid-
179 SC_ALLOW(__NR_getpgid),-
180#endif-
181#ifdef __NR_getpid-
182 SC_ALLOW(__NR_getpid),-
183#endif-
184#ifdef __NR_getrandom-
185 SC_ALLOW(__NR_getrandom),-
186#endif-
187#ifdef __NR_gettimeofday-
188 SC_ALLOW(__NR_gettimeofday),-
189#endif-
190#ifdef __NR_getuid-
191 SC_ALLOW(__NR_getuid),-
192#endif-
193#ifdef __NR_getuid32-
194 SC_ALLOW(__NR_getuid32),-
195#endif-
196#ifdef __NR_madvise-
197 SC_ALLOW(__NR_madvise),-
198#endif-
199#ifdef __NR_mmap-
200 SC_ALLOW(__NR_mmap),-
201#endif-
202#ifdef __NR_mmap2-
203 SC_ALLOW(__NR_mmap2),-
204#endif-
205#ifdef __NR_mremap-
206 SC_ALLOW(__NR_mremap),-
207#endif-
208#ifdef __NR_munmap-
209 SC_ALLOW(__NR_munmap),-
210#endif-
211#ifdef __NR_nanosleep-
212 SC_ALLOW(__NR_nanosleep),-
213#endif-
214#ifdef __NR__newselect-
215 SC_ALLOW(__NR__newselect),-
216#endif-
217#ifdef __NR_poll-
218 SC_ALLOW(__NR_poll),-
219#endif-
220#ifdef __NR_pselect6-
221 SC_ALLOW(__NR_pselect6),-
222#endif-
223#ifdef __NR_read-
224 SC_ALLOW(__NR_read),-
225#endif-
226#ifdef __NR_rt_sigprocmask-
227 SC_ALLOW(__NR_rt_sigprocmask),-
228#endif-
229#ifdef __NR_select-
230 SC_ALLOW(__NR_select),-
231#endif-
232#ifdef __NR_shutdown-
233 SC_ALLOW(__NR_shutdown),-
234#endif-
235#ifdef __NR_sigprocmask-
236 SC_ALLOW(__NR_sigprocmask),-
237#endif-
238#ifdef __NR_time-
239 SC_ALLOW(__NR_time),-
240#endif-
241#ifdef __NR_write-
242 SC_ALLOW(__NR_write),-
243#endif-
244#ifdef __NR_socketcall-
245 SC_ALLOW_ARG(__NR_socketcall, 0, SYS_SHUTDOWN),-
246 SC_DENY(__NR_socketcall, EACCES),-
247#endif-
248#if defined(__NR_ioctl) && defined(__s390__)-
249 /* Allow ioctls for ICA crypto card on s390 */-
250 SC_ALLOW_ARG(__NR_ioctl, 1, Z90STAT_STATUS_MASK),-
251 SC_ALLOW_ARG(__NR_ioctl, 1, ICARSAMODEXPO),-
252 SC_ALLOW_ARG(__NR_ioctl, 1, ICARSACRT),-
253#endif-
254#if defined(__x86_64__) && defined(__ILP32__) && defined(__X32_SYSCALL_BIT)-
255 /*-
256 * On Linux x32, the clock_gettime VDSO falls back to the-
257 * x86-64 syscall under some circumstances, e.g.-
258 * https://bugs.debian.org/849923-
259 */-
260 SC_ALLOW(__NR_clock_gettime & ~__X32_SYSCALL_BIT),-
261#endif-
262-
263 /* Default deny */-
264 BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),-
265};-
266-
267static const struct sock_fprog preauth_program = {-
268 .len = (unsigned short)(sizeof(preauth_insns)/sizeof(preauth_insns[0])),-
269 .filter = (struct sock_filter *)preauth_insns,-
270};-
271-
272struct ssh_sandbox {-
273 pid_t child_pid;-
274};-
275-
276struct ssh_sandbox *-
277ssh_sandbox_init(struct monitor *monitor)-
278{-
279 struct ssh_sandbox *box;-
280-
281 /*-
282 * Strictly, we don't need to maintain any state here but we need-
283 * to return non-NULL to satisfy the API.-
284 */-
285 debug3("%s: preparing seccomp filter sandbox", __func__);-
286 box = xcalloc(1, sizeof(*box));-
287 box->child_pid = 0;-
288-
289 return box;
never executed: return box;
0
290}-
291-
292#ifdef SANDBOX_SECCOMP_FILTER_DEBUG-
293extern struct monitor *pmonitor;-
294void mm_log_handler(LogLevel level, const char *msg, void *ctx);-
295-
296static void-
297ssh_sandbox_violation(int signum, siginfo_t *info, void *void_context)-
298{-
299 char msg[256];-
300-
301 snprintf(msg, sizeof(msg),-
302 "%s: unexpected system call (arch:0x%x,syscall:%d @ %p)",-
303 __func__, info->si_arch, info->si_syscall, info->si_call_addr);-
304 mm_log_handler(SYSLOG_LEVEL_FATAL, msg, pmonitor);-
305 _exit(1);-
306}-
307-
308static void-
309ssh_sandbox_child_debugging(void)-
310{-
311 struct sigaction act;-
312 sigset_t mask;-
313-
314 debug3("%s: installing SIGSYS handler", __func__);-
315 memset(&act, 0, sizeof(act));-
316 sigemptyset(&mask);-
317 sigaddset(&mask, SIGSYS);-
318-
319 act.sa_sigaction = &ssh_sandbox_violation;-
320 act.sa_flags = SA_SIGINFO;-
321 if (sigaction(SIGSYS, &act, NULL) == -1)-
322 fatal("%s: sigaction(SIGSYS): %s", __func__, strerror(errno));-
323 if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1)-
324 fatal("%s: sigprocmask(SIGSYS): %s",-
325 __func__, strerror(errno));-
326}-
327#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */-
328-
329void-
330ssh_sandbox_child(struct ssh_sandbox *box)-
331{-
332 struct rlimit rl_zero;-
333 int nnp_failed = 0;-
334-
335 /* Set rlimits for completeness if possible. */-
336 rl_zero.rlim_cur = rl_zero.rlim_max = 0;-
337 if (setrlimit(RLIMIT_FSIZE, &rl_zero) == -1)
setrlimit( RLI...rl_zero) == -1Description
TRUEnever evaluated
FALSEnever evaluated
0
338 fatal("%s: setrlimit(RLIMIT_FSIZE, { 0, 0 }): %s",
never executed: fatal("%s: setrlimit(RLIMIT_FSIZE, { 0, 0 }): %s", __func__, strerror( (*__errno_location ()) ));
0
339 __func__, strerror(errno));
never executed: fatal("%s: setrlimit(RLIMIT_FSIZE, { 0, 0 }): %s", __func__, strerror( (*__errno_location ()) ));
0
340 if (setrlimit(RLIMIT_NOFILE, &rl_zero) == -1)
setrlimit( RLI...rl_zero) == -1Description
TRUEnever evaluated
FALSEnever evaluated
0
341 fatal("%s: setrlimit(RLIMIT_NOFILE, { 0, 0 }): %s",
never executed: fatal("%s: setrlimit(RLIMIT_NOFILE, { 0, 0 }): %s", __func__, strerror( (*__errno_location ()) ));
0
342 __func__, strerror(errno));
never executed: fatal("%s: setrlimit(RLIMIT_NOFILE, { 0, 0 }): %s", __func__, strerror( (*__errno_location ()) ));
0
343 if (setrlimit(RLIMIT_NPROC, &rl_zero) == -1)
setrlimit( __R...rl_zero) == -1Description
TRUEnever evaluated
FALSEnever evaluated
0
344 fatal("%s: setrlimit(RLIMIT_NPROC, { 0, 0 }): %s",
never executed: fatal("%s: setrlimit(RLIMIT_NPROC, { 0, 0 }): %s", __func__, strerror( (*__errno_location ()) ));
0
345 __func__, strerror(errno));
never executed: fatal("%s: setrlimit(RLIMIT_NPROC, { 0, 0 }): %s", __func__, strerror( (*__errno_location ()) ));
0
346-
347#ifdef SANDBOX_SECCOMP_FILTER_DEBUG-
348 ssh_sandbox_child_debugging();-
349#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */-
350-
351 debug3("%s: setting PR_SET_NO_NEW_PRIVS", __func__);-
352 if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) {
prctl( 38 , 1, 0, 0, 0) == -1Description
TRUEnever evaluated
FALSEnever evaluated
0
353 debug("%s: prctl(PR_SET_NO_NEW_PRIVS): %s",-
354 __func__, strerror(errno));-
355 nnp_failed = 1;-
356 }
never executed: end of block
0
357 debug3("%s: attaching seccomp filter program", __func__);-
358 if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &preauth_program) == -1)
prctl( 22 , 2 ...program) == -1Description
TRUEnever evaluated
FALSEnever evaluated
0
359 debug("%s: prctl(PR_SET_SECCOMP): %s",
never executed: debug("%s: prctl(PR_SET_SECCOMP): %s", __func__, strerror( (*__errno_location ()) ));
0
360 __func__, strerror(errno));
never executed: debug("%s: prctl(PR_SET_SECCOMP): %s", __func__, strerror( (*__errno_location ()) ));
0
361 else if (nnp_failed)
nnp_failedDescription
TRUEnever evaluated
FALSEnever evaluated
0
362 fatal("%s: SECCOMP_MODE_FILTER activated but "
never executed: fatal("%s: SECCOMP_MODE_FILTER activated but " "PR_SET_NO_NEW_PRIVS failed", __func__);
0
363 "PR_SET_NO_NEW_PRIVS failed", __func__);
never executed: fatal("%s: SECCOMP_MODE_FILTER activated but " "PR_SET_NO_NEW_PRIVS failed", __func__);
0
364}
never executed: end of block
0
365-
366void-
367ssh_sandbox_parent_finish(struct ssh_sandbox *box)-
368{-
369 free(box);-
370 debug3("%s: finished", __func__);-
371}
never executed: end of block
0
372-
373void-
374ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)-
375{-
376 box->child_pid = child_pid;-
377}
never executed: end of block
0
378-
379#endif /* SANDBOX_SECCOMP_FILTER */-
Source codeSwitch to Preprocessed file
Generated by Squish Coco 4.2.2