219 lines
6.2 KiB
C
219 lines
6.2 KiB
C
/* $OpenBSD: sandbox-systrace.c,v 1.18 2015/10/02 01:39:26 deraadt Exp $ */
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/*
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* Copyright (c) 2011 Damien Miller <djm@mindrot.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include "includes.h"
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#ifdef SANDBOX_SYSTRACE
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#include <sys/types.h>
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#include <sys/ioctl.h>
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#include <sys/syscall.h>
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#include <sys/socket.h>
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#include <sys/wait.h>
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#include <dev/systrace.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <signal.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <limits.h>
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#include "atomicio.h"
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#include "log.h"
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#include "ssh-sandbox.h"
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#include "xmalloc.h"
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struct sandbox_policy {
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int syscall;
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int action;
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};
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/* Permitted syscalls in preauth. Unlisted syscalls get SYSTR_POLICY_KILL */
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static const struct sandbox_policy preauth_policy[] = {
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{ SYS_exit, SYSTR_POLICY_PERMIT },
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#ifdef SYS_kbind
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{ SYS_kbind, SYSTR_POLICY_PERMIT },
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#endif
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{ SYS_getpid, SYSTR_POLICY_PERMIT },
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{ SYS_getpgid, SYSTR_POLICY_PERMIT },
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{ SYS_clock_gettime, SYSTR_POLICY_PERMIT },
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{ SYS_gettimeofday, SYSTR_POLICY_PERMIT },
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{ SYS_sigprocmask, SYSTR_POLICY_PERMIT },
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#ifdef SYS_getentropy
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/* OpenBSD 5.6 and newer use getentropy(2) to seed arc4random(3). */
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{ SYS_getentropy, SYSTR_POLICY_PERMIT },
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#else
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/* Previous releases used sysctl(3)'s kern.arnd variable. */
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{ SYS___sysctl, SYSTR_POLICY_PERMIT },
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#endif
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#ifdef SYS_sendsyslog
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{ SYS_sendsyslog, SYSTR_POLICY_PERMIT },
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#endif
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{ SYS_madvise, SYSTR_POLICY_PERMIT },
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{ SYS_mmap, SYSTR_POLICY_PERMIT },
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{ SYS_mprotect, SYSTR_POLICY_PERMIT },
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{ SYS_mquery, SYSTR_POLICY_PERMIT },
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{ SYS_munmap, SYSTR_POLICY_PERMIT },
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{ SYS_poll, SYSTR_POLICY_PERMIT },
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{ SYS_select, SYSTR_POLICY_PERMIT },
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{ SYS_read, SYSTR_POLICY_PERMIT },
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{ SYS_write, SYSTR_POLICY_PERMIT },
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{ SYS_shutdown, SYSTR_POLICY_PERMIT },
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{ SYS_close, SYSTR_POLICY_PERMIT },
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{ SYS_open, SYSTR_POLICY_NEVER },
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{ -1, -1 }
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};
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struct ssh_sandbox {
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int systrace_fd;
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pid_t child_pid;
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void (*osigchld)(int);
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};
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struct ssh_sandbox *
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ssh_sandbox_init(struct monitor *monitor)
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{
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struct ssh_sandbox *box;
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debug3("%s: preparing systrace sandbox", __func__);
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box = xcalloc(1, sizeof(*box));
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box->systrace_fd = -1;
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box->child_pid = 0;
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box->osigchld = signal(SIGCHLD, SIG_IGN);
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return box;
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}
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void
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ssh_sandbox_child(struct ssh_sandbox *box)
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{
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debug3("%s: ready", __func__);
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signal(SIGCHLD, box->osigchld);
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if (kill(getpid(), SIGSTOP) != 0)
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fatal("%s: kill(%d, SIGSTOP)", __func__, getpid());
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debug3("%s: started", __func__);
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}
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static void
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ssh_sandbox_parent(struct ssh_sandbox *box, pid_t child_pid,
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const struct sandbox_policy *allowed_syscalls)
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{
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int dev_systrace, i, j, found, status;
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pid_t pid;
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struct systrace_policy policy;
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/* Wait for the child to send itself a SIGSTOP */
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debug3("%s: wait for child %ld", __func__, (long)child_pid);
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do {
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pid = waitpid(child_pid, &status, WUNTRACED);
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} while (pid == -1 && errno == EINTR);
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signal(SIGCHLD, box->osigchld);
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if (!WIFSTOPPED(status)) {
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if (WIFSIGNALED(status))
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fatal("%s: child terminated with signal %d",
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__func__, WTERMSIG(status));
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if (WIFEXITED(status))
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fatal("%s: child exited with status %d",
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__func__, WEXITSTATUS(status));
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fatal("%s: child not stopped", __func__);
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}
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debug3("%s: child %ld stopped", __func__, (long)child_pid);
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box->child_pid = child_pid;
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/* Set up systracing of child */
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if ((dev_systrace = open("/dev/systrace", O_RDONLY)) == -1)
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fatal("%s: open(\"/dev/systrace\"): %s", __func__,
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strerror(errno));
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if (ioctl(dev_systrace, STRIOCCLONE, &box->systrace_fd) == -1)
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fatal("%s: ioctl(STRIOCCLONE, %d): %s", __func__,
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dev_systrace, strerror(errno));
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close(dev_systrace);
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debug3("%s: systrace attach, fd=%d", __func__, box->systrace_fd);
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if (ioctl(box->systrace_fd, STRIOCATTACH, &child_pid) == -1)
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fatal("%s: ioctl(%d, STRIOCATTACH, %d): %s", __func__,
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box->systrace_fd, child_pid, strerror(errno));
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/* Allocate and assign policy */
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memset(&policy, 0, sizeof(policy));
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policy.strp_op = SYSTR_POLICY_NEW;
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policy.strp_maxents = SYS_MAXSYSCALL;
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if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
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fatal("%s: ioctl(%d, STRIOCPOLICY (new)): %s", __func__,
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box->systrace_fd, strerror(errno));
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policy.strp_op = SYSTR_POLICY_ASSIGN;
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policy.strp_pid = box->child_pid;
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if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
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fatal("%s: ioctl(%d, STRIOCPOLICY (assign)): %s",
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__func__, box->systrace_fd, strerror(errno));
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/* Set per-syscall policy */
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for (i = 0; i < SYS_MAXSYSCALL; i++) {
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found = 0;
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for (j = 0; allowed_syscalls[j].syscall != -1; j++) {
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if (allowed_syscalls[j].syscall == i) {
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found = 1;
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break;
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}
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}
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policy.strp_op = SYSTR_POLICY_MODIFY;
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policy.strp_code = i;
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policy.strp_policy = found ?
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allowed_syscalls[j].action : SYSTR_POLICY_KILL;
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if (found)
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debug3("%s: policy: enable syscall %d", __func__, i);
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if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
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fatal("%s: ioctl(%d, STRIOCPOLICY (modify)): %s",
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__func__, box->systrace_fd, strerror(errno));
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}
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/* Signal the child to start running */
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debug3("%s: start child %ld", __func__, (long)child_pid);
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if (kill(box->child_pid, SIGCONT) != 0)
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fatal("%s: kill(%d, SIGCONT)", __func__, box->child_pid);
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}
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void
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ssh_sandbox_parent_finish(struct ssh_sandbox *box)
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{
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/* Closing this before the child exits will terminate it */
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close(box->systrace_fd);
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free(box);
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debug3("%s: finished", __func__);
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}
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void
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ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
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{
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ssh_sandbox_parent(box, child_pid, preauth_policy);
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}
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#endif /* SANDBOX_SYSTRACE */
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