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218 lines
6.2 KiB
218 lines
6.2 KiB
/* $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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