1 /* $OpenBSD: sandbox-systrace.c,v 1.18 2015/10/02 01:39:26 deraadt Exp $ */
3 * Copyright (c) 2011 Damien Miller <djm@mindrot.org>
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
20 #ifdef SANDBOX_SYSTRACE
22 #include <sys/types.h>
23 #include <sys/ioctl.h>
24 #include <sys/syscall.h>
25 #include <sys/socket.h>
28 #include <dev/systrace.h>
43 #include "ssh-sandbox.h"
46 struct sandbox_policy {
51 /* Permitted syscalls in preauth. Unlisted syscalls get SYSTR_POLICY_KILL */
52 static const struct sandbox_policy preauth_policy[] = {
53 { SYS_exit, SYSTR_POLICY_PERMIT },
55 { SYS_kbind, SYSTR_POLICY_PERMIT },
58 { SYS_getpid, SYSTR_POLICY_PERMIT },
59 { SYS_getpgid, SYSTR_POLICY_PERMIT },
60 { SYS_clock_gettime, SYSTR_POLICY_PERMIT },
61 { SYS_gettimeofday, SYSTR_POLICY_PERMIT },
62 { SYS_nanosleep, SYSTR_POLICY_PERMIT },
63 { SYS_sigprocmask, SYSTR_POLICY_PERMIT },
66 /* OpenBSD 5.6 and newer use getentropy(2) to seed arc4random(3). */
67 { SYS_getentropy, SYSTR_POLICY_PERMIT },
69 /* Previous releases used sysctl(3)'s kern.arnd variable. */
70 { SYS___sysctl, SYSTR_POLICY_PERMIT },
73 { SYS_sendsyslog, SYSTR_POLICY_PERMIT },
76 { SYS_madvise, SYSTR_POLICY_PERMIT },
77 { SYS_mmap, SYSTR_POLICY_PERMIT },
78 { SYS_mprotect, SYSTR_POLICY_PERMIT },
79 { SYS_mquery, SYSTR_POLICY_PERMIT },
80 { SYS_munmap, SYSTR_POLICY_PERMIT },
82 { SYS_poll, SYSTR_POLICY_PERMIT },
83 { SYS_select, SYSTR_POLICY_PERMIT },
84 { SYS_read, SYSTR_POLICY_PERMIT },
85 { SYS_write, SYSTR_POLICY_PERMIT },
86 { SYS_shutdown, SYSTR_POLICY_PERMIT },
87 { SYS_close, SYSTR_POLICY_PERMIT },
89 { SYS_open, SYSTR_POLICY_NEVER },
97 void (*osigchld)(int);
101 ssh_sandbox_init(struct monitor *monitor)
103 struct ssh_sandbox *box;
105 debug3("%s: preparing systrace sandbox", __func__);
106 box = xcalloc(1, sizeof(*box));
107 box->systrace_fd = -1;
109 box->osigchld = signal(SIGCHLD, SIG_IGN);
115 ssh_sandbox_child(struct ssh_sandbox *box)
117 debug3("%s: ready", __func__);
118 signal(SIGCHLD, box->osigchld);
119 if (kill(getpid(), SIGSTOP) != 0)
120 fatal("%s: kill(%d, SIGSTOP)", __func__, getpid());
121 debug3("%s: started", __func__);
125 ssh_sandbox_parent(struct ssh_sandbox *box, pid_t child_pid,
126 const struct sandbox_policy *allowed_syscalls)
128 int dev_systrace, i, j, found, status;
130 struct systrace_policy policy;
132 /* Wait for the child to send itself a SIGSTOP */
133 debug3("%s: wait for child %ld", __func__, (long)child_pid);
135 pid = waitpid(child_pid, &status, WUNTRACED);
136 } while (pid == -1 && errno == EINTR);
137 signal(SIGCHLD, box->osigchld);
138 if (!WIFSTOPPED(status)) {
139 if (WIFSIGNALED(status))
140 fatal("%s: child terminated with signal %d",
141 __func__, WTERMSIG(status));
142 if (WIFEXITED(status))
143 fatal("%s: child exited with status %d",
144 __func__, WEXITSTATUS(status));
145 fatal("%s: child not stopped", __func__);
147 debug3("%s: child %ld stopped", __func__, (long)child_pid);
148 box->child_pid = child_pid;
150 /* Set up systracing of child */
151 if ((dev_systrace = open("/dev/systrace", O_RDONLY)) == -1)
152 fatal("%s: open(\"/dev/systrace\"): %s", __func__,
154 if (ioctl(dev_systrace, STRIOCCLONE, &box->systrace_fd) == -1)
155 fatal("%s: ioctl(STRIOCCLONE, %d): %s", __func__,
156 dev_systrace, strerror(errno));
158 debug3("%s: systrace attach, fd=%d", __func__, box->systrace_fd);
159 if (ioctl(box->systrace_fd, STRIOCATTACH, &child_pid) == -1)
160 fatal("%s: ioctl(%d, STRIOCATTACH, %d): %s", __func__,
161 box->systrace_fd, child_pid, strerror(errno));
163 /* Allocate and assign policy */
164 memset(&policy, 0, sizeof(policy));
165 policy.strp_op = SYSTR_POLICY_NEW;
166 policy.strp_maxents = SYS_MAXSYSCALL;
167 if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
168 fatal("%s: ioctl(%d, STRIOCPOLICY (new)): %s", __func__,
169 box->systrace_fd, strerror(errno));
171 policy.strp_op = SYSTR_POLICY_ASSIGN;
172 policy.strp_pid = box->child_pid;
173 if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
174 fatal("%s: ioctl(%d, STRIOCPOLICY (assign)): %s",
175 __func__, box->systrace_fd, strerror(errno));
177 /* Set per-syscall policy */
178 for (i = 0; i < SYS_MAXSYSCALL; i++) {
180 for (j = 0; allowed_syscalls[j].syscall != -1; j++) {
181 if (allowed_syscalls[j].syscall == i) {
186 policy.strp_op = SYSTR_POLICY_MODIFY;
187 policy.strp_code = i;
188 policy.strp_policy = found ?
189 allowed_syscalls[j].action : SYSTR_POLICY_KILL;
191 debug3("%s: policy: enable syscall %d", __func__, i);
192 if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
193 fatal("%s: ioctl(%d, STRIOCPOLICY (modify)): %s",
194 __func__, box->systrace_fd, strerror(errno));
197 /* Signal the child to start running */
198 debug3("%s: start child %ld", __func__, (long)child_pid);
199 if (kill(box->child_pid, SIGCONT) != 0)
200 fatal("%s: kill(%d, SIGCONT)", __func__, box->child_pid);
204 ssh_sandbox_parent_finish(struct ssh_sandbox *box)
206 /* Closing this before the child exits will terminate it */
207 close(box->systrace_fd);
210 debug3("%s: finished", __func__);
214 ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
216 ssh_sandbox_parent(box, child_pid, preauth_policy);
219 #endif /* SANDBOX_SYSTRACE */