sandbox-seccomp-filter.c - third_party/openssh-portable - Git at Google

 /*
  * Copyright (c) 2012 Will Drewry <wad@dataspill.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
  * copyright notice and this permission notice appear in all copies.
  *
  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */

 /*
  * Uncomment the SANDBOX_SECCOMP_FILTER_DEBUG macro below to help diagnose
  * filter breakage during development. *Do not* use this in production,
  * as it relies on making library calls that are unsafe in signal context.
  *
  * Instead, live systems the auditctl(8) may be used to monitor failures.
  * E.g.
  *   auditctl -a task,always -F uid=<privsep uid>
  */
 /* #define SANDBOX_SECCOMP_FILTER_DEBUG 1 */

 /* XXX it should be possible to do logging via the log socket safely */

 #ifdef SANDBOX_SECCOMP_FILTER_DEBUG
 /* Use the kernel headers in case of an older toolchain. */
 # include <asm/siginfo.h>
 # define __have_siginfo_t 1
 # define __have_sigval_t 1
 # define __have_sigevent_t 1
 #endif /* SANDBOX_SECCOMP_FILTER_DEBUG */

 #include "includes.h"

 #ifdef SANDBOX_SECCOMP_FILTER

 #include <sys/types.h>
 #include <sys/resource.h>
 #include <sys/prctl.h>

 #include <linux/net.h>
 #include <linux/audit.h>
 #include <linux/filter.h>
 #include <linux/seccomp.h>
 #include <elf.h>

 #include <asm/unistd.h>

 #include <errno.h>
 #include <signal.h>
 #include <stdarg.h>
 #include <stddef.h>  /* for offsetof */
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>

 #include "log.h"
 #include "ssh-sandbox.h"
 #include "xmalloc.h"

 /* Linux seccomp_filter sandbox */
 #define SECCOMP_FILTER_FAIL SECCOMP_RET_KILL

 /* Use a signal handler to emit violations when debugging */
 #ifdef SANDBOX_SECCOMP_FILTER_DEBUG
 # undef SECCOMP_FILTER_FAIL
 # define SECCOMP_FILTER_FAIL SECCOMP_RET_TRAP
 #endif /* SANDBOX_SECCOMP_FILTER_DEBUG */

 /* Simple helpers to avoid manual errors (but larger BPF programs). */
 #define SC_DENY(_nr, _errno) \
 	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_ ## _nr, 0, 1), \
 	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ERRNO|(_errno))
 #define SC_ALLOW(_nr) \
 	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_ ## _nr, 0, 1), \
 	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW)
 #define SC_ALLOW_ARG(_nr, _arg_nr, _arg_val) \
 	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_ ## _nr, 0, 4), \
 	/* load first syscall argument */ \
 	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
 	    offsetof(struct seccomp_data, args[(_arg_nr)])), \
 	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_arg_val), 0, 1), \
 	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), \
 	/* reload syscall number; all rules expect it in accumulator */ \
 	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
 		offsetof(struct seccomp_data, nr))

 /* Syscall filtering set for preauth. */
 static const struct sock_filter preauth_insns[] = {
 	/* Ensure the syscall arch convention is as expected. */
 	BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
 		offsetof(struct seccomp_data, arch)),
 	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, SECCOMP_AUDIT_ARCH, 1, 0),
 	BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),
 	/* Load the syscall number for checking. */
 	BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
 		offsetof(struct seccomp_data, nr)),

 	/* Syscalls to non-fatally deny */
 #ifdef __NR_lstat
 	SC_DENY(lstat, EACCES),
 #endif
 #ifdef __NR_lstat64
 	SC_DENY(lstat64, EACCES),
 #endif
 #ifdef __NR_fstat
 	SC_DENY(fstat, EACCES),
 #endif
 #ifdef __NR_fstat64
 	SC_DENY(fstat64, EACCES),
 #endif
 #ifdef __NR_open
 	SC_DENY(open, EACCES),
 #endif
 #ifdef __NR_openat
 	SC_DENY(openat, EACCES),
 #endif
 #ifdef __NR_newfstatat
 	SC_DENY(newfstatat, EACCES),
 #endif
 #ifdef __NR_stat
 	SC_DENY(stat, EACCES),
 #endif
 #ifdef __NR_stat64
 	SC_DENY(stat64, EACCES),
 #endif

 	/* Syscalls to permit */
 #ifdef __NR_brk
 	SC_ALLOW(brk),
 #endif
 #ifdef __NR_clock_gettime
 	SC_ALLOW(clock_gettime),
 #endif
 #ifdef __NR_close
 	SC_ALLOW(close),
 #endif
 #ifdef __NR_exit
 	SC_ALLOW(exit),
 #endif
 #ifdef __NR_exit_group
 	SC_ALLOW(exit_group),
 #endif
 #ifdef __NR_getpgid
 	SC_ALLOW(getpgid),
 #endif
 #ifdef __NR_getpid
 	SC_ALLOW(getpid),
 #endif
 #ifdef __NR_getrandom
 	SC_ALLOW(getrandom),
 #endif
 #ifdef __NR_gettimeofday
 	SC_ALLOW(gettimeofday),
 #endif
 #ifdef __NR_madvise
 	SC_ALLOW(madvise),
 #endif
 #ifdef __NR_mmap
 	SC_ALLOW(mmap),
 #endif
 #ifdef __NR_mmap2
 	SC_ALLOW(mmap2),
 #endif
 #ifdef __NR_mremap
 	SC_ALLOW(mremap),
 #endif
 #ifdef __NR_munmap
 	SC_ALLOW(munmap),
 #endif
 #ifdef __NR__newselect
 	SC_ALLOW(_newselect),
 #endif
 #ifdef __NR_poll
 	SC_ALLOW(poll),
 #endif
 #ifdef __NR_pselect6
 	SC_ALLOW(pselect6),
 #endif
 #ifdef __NR_read
 	SC_ALLOW(read),
 #endif
 #ifdef __NR_rt_sigprocmask
 	SC_ALLOW(rt_sigprocmask),
 #endif
 #ifdef __NR_select
 	SC_ALLOW(select),
 #endif
 #ifdef __NR_shutdown
 	SC_ALLOW(shutdown),
 #endif
 #ifdef __NR_sigprocmask
 	SC_ALLOW(sigprocmask),
 #endif
 #ifdef __NR_time
 	SC_ALLOW(time),
 #endif
 #ifdef __NR_write
 	SC_ALLOW(write),
 #endif
 #ifdef __NR_socketcall
 	SC_ALLOW_ARG(socketcall, 0, SYS_SHUTDOWN),
 #endif

 	/* Default deny */
 	BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),
 };

 static const struct sock_fprog preauth_program = {
 	.len = (unsigned short)(sizeof(preauth_insns)/sizeof(preauth_insns[0])),
 	.filter = (struct sock_filter *)preauth_insns,
 };

 struct ssh_sandbox {
 	pid_t child_pid;
 };

 struct ssh_sandbox *
 ssh_sandbox_init(struct monitor *monitor)
 {
 	struct ssh_sandbox *box;

 	/*
 	 * Strictly, we don't need to maintain any state here but we need
 	 * to return non-NULL to satisfy the API.
 	 */
 	debug3("%s: preparing seccomp filter sandbox", __func__);
 	box = xcalloc(1, sizeof(*box));
 	box->child_pid = 0;

 	return box;
 }

 #ifdef SANDBOX_SECCOMP_FILTER_DEBUG
 extern struct monitor *pmonitor;
 void mm_log_handler(LogLevel level, const char *msg, void *ctx);

 static void
 ssh_sandbox_violation(int signum, siginfo_t *info, void *void_context)
 {
 	char msg[256];

 	snprintf(msg, sizeof(msg),
 	    "%s: unexpected system call (arch:0x%x,syscall:%d @ %p)",
 	    __func__, info->si_arch, info->si_syscall, info->si_call_addr);
 	mm_log_handler(SYSLOG_LEVEL_FATAL, msg, pmonitor);
 	_exit(1);
 }

 static void
 ssh_sandbox_child_debugging(void)
 {
 	struct sigaction act;
 	sigset_t mask;

 	debug3("%s: installing SIGSYS handler", __func__);
 	memset(&act, 0, sizeof(act));
 	sigemptyset(&mask);
 	sigaddset(&mask, SIGSYS);

 	act.sa_sigaction = &ssh_sandbox_violation;
 	act.sa_flags = SA_SIGINFO;
 	if (sigaction(SIGSYS, &act, NULL) == -1)
 		fatal("%s: sigaction(SIGSYS): %s", __func__, strerror(errno));
 	if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1)
 		fatal("%s: sigprocmask(SIGSYS): %s",
 		      __func__, strerror(errno));
 }
 #endif /* SANDBOX_SECCOMP_FILTER_DEBUG */

 void
 ssh_sandbox_child(struct ssh_sandbox *box)
 {
 	struct rlimit rl_zero;
 	int nnp_failed = 0;

 	/* Set rlimits for completeness if possible. */
 	rl_zero.rlim_cur = rl_zero.rlim_max = 0;
 	if (setrlimit(RLIMIT_FSIZE, &rl_zero) == -1)
 		fatal("%s: setrlimit(RLIMIT_FSIZE, { 0, 0 }): %s",
 			__func__, strerror(errno));
 	if (setrlimit(RLIMIT_NOFILE, &rl_zero) == -1)
 		fatal("%s: setrlimit(RLIMIT_NOFILE, { 0, 0 }): %s",
 			__func__, strerror(errno));
 	if (setrlimit(RLIMIT_NPROC, &rl_zero) == -1)
 		fatal("%s: setrlimit(RLIMIT_NPROC, { 0, 0 }): %s",
 			__func__, strerror(errno));

 #ifdef SANDBOX_SECCOMP_FILTER_DEBUG
 	ssh_sandbox_child_debugging();
 #endif /* SANDBOX_SECCOMP_FILTER_DEBUG */

 	debug3("%s: setting PR_SET_NO_NEW_PRIVS", __func__);
 	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) {
 		debug("%s: prctl(PR_SET_NO_NEW_PRIVS): %s",
 		      __func__, strerror(errno));
 		nnp_failed = 1;
 	}
 	debug3("%s: attaching seccomp filter program", __func__);
 	if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &preauth_program) == -1)
 		debug("%s: prctl(PR_SET_SECCOMP): %s",
 		      __func__, strerror(errno));
 	else if (nnp_failed)
 		fatal("%s: SECCOMP_MODE_FILTER activated but "
 		    "PR_SET_NO_NEW_PRIVS failed", __func__);
 }

 void
 ssh_sandbox_parent_finish(struct ssh_sandbox *box)
 {
 	free(box);
 	debug3("%s: finished", __func__);
 }

 void
 ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
 {
 	box->child_pid = child_pid;
 }

 #endif /* SANDBOX_SECCOMP_FILTER */
	/*
	* Copyright (c) 2012 Will Drewry <wad@dataspill.org>
	*
	* Permission to use, copy, modify, and distribute this software for any
	* purpose with or without fee is hereby granted, provided that the above
	* copyright notice and this permission notice appear in all copies.
	*
	* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
	* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
	*/

	/*
	* Uncomment the SANDBOX_SECCOMP_FILTER_DEBUG macro below to help diagnose
	* filter breakage during development. Do not use this in production,
	* as it relies on making library calls that are unsafe in signal context.
	*
	* Instead, live systems the auditctl(8) may be used to monitor failures.
	* E.g.
	* auditctl -a task,always -F uid=<privsep uid>
	*/
	/* #define SANDBOX_SECCOMP_FILTER_DEBUG 1 */

	/* XXX it should be possible to do logging via the log socket safely */

	#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
	/* Use the kernel headers in case of an older toolchain. */
	# include <asm/siginfo.h>
	# define __have_siginfo_t 1
	# define __have_sigval_t 1
	# define __have_sigevent_t 1
	#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */

	#include "includes.h"

	#ifdef SANDBOX_SECCOMP_FILTER

	#include <sys/types.h>
	#include <sys/resource.h>
	#include <sys/prctl.h>

	#include <linux/net.h>
	#include <linux/audit.h>
	#include <linux/filter.h>
	#include <linux/seccomp.h>
	#include <elf.h>

	#include <asm/unistd.h>

	#include <errno.h>
	#include <signal.h>
	#include <stdarg.h>
	#include <stddef.h> /* for offsetof */
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>

	#include "log.h"
	#include "ssh-sandbox.h"
	#include "xmalloc.h"

	/* Linux seccomp_filter sandbox */
	#define SECCOMP_FILTER_FAIL SECCOMP_RET_KILL

	/* Use a signal handler to emit violations when debugging */
	#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
	# undef SECCOMP_FILTER_FAIL
	# define SECCOMP_FILTER_FAIL SECCOMP_RET_TRAP
	#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */

	/* Simple helpers to avoid manual errors (but larger BPF programs). */
	#define SC_DENY(_nr, _errno) \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_ ## _nr, 0, 1), \
	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ERRNO\|(_errno))
	#define SC_ALLOW(_nr) \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_ ## _nr, 0, 1), \
	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW)
	#define SC_ALLOW_ARG(_nr, _arg_nr, _arg_val) \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, __NR_ ## _nr, 0, 4), \
	/* load first syscall argument */ \
	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
	offsetof(struct seccomp_data, args[(_arg_nr)])), \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_arg_val), 0, 1), \
	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), \
	/* reload syscall number; all rules expect it in accumulator */ \
	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
	offsetof(struct seccomp_data, nr))

	/* Syscall filtering set for preauth. */
	static const struct sock_filter preauth_insns[] = {
	/* Ensure the syscall arch convention is as expected. */
	BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
	offsetof(struct seccomp_data, arch)),
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, SECCOMP_AUDIT_ARCH, 1, 0),
	BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),
	/* Load the syscall number for checking. */
	BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
	offsetof(struct seccomp_data, nr)),

	/* Syscalls to non-fatally deny */
	#ifdef __NR_lstat
	SC_DENY(lstat, EACCES),
	#endif
	#ifdef __NR_lstat64
	SC_DENY(lstat64, EACCES),
	#endif
	#ifdef __NR_fstat
	SC_DENY(fstat, EACCES),
	#endif
	#ifdef __NR_fstat64
	SC_DENY(fstat64, EACCES),
	#endif
	#ifdef __NR_open
	SC_DENY(open, EACCES),
	#endif
	#ifdef __NR_openat
	SC_DENY(openat, EACCES),
	#endif
	#ifdef __NR_newfstatat
	SC_DENY(newfstatat, EACCES),
	#endif
	#ifdef __NR_stat
	SC_DENY(stat, EACCES),
	#endif
	#ifdef __NR_stat64
	SC_DENY(stat64, EACCES),
	#endif

	/* Syscalls to permit */
	#ifdef __NR_brk
	SC_ALLOW(brk),
	#endif
	#ifdef __NR_clock_gettime
	SC_ALLOW(clock_gettime),
	#endif
	#ifdef __NR_close
	SC_ALLOW(close),
	#endif
	#ifdef __NR_exit
	SC_ALLOW(exit),
	#endif
	#ifdef __NR_exit_group
	SC_ALLOW(exit_group),
	#endif
	#ifdef __NR_getpgid
	SC_ALLOW(getpgid),
	#endif
	#ifdef __NR_getpid
	SC_ALLOW(getpid),
	#endif
	#ifdef __NR_getrandom
	SC_ALLOW(getrandom),
	#endif
	#ifdef __NR_gettimeofday
	SC_ALLOW(gettimeofday),
	#endif
	#ifdef __NR_madvise
	SC_ALLOW(madvise),
	#endif
	#ifdef __NR_mmap
	SC_ALLOW(mmap),
	#endif
	#ifdef __NR_mmap2
	SC_ALLOW(mmap2),
	#endif
	#ifdef __NR_mremap
	SC_ALLOW(mremap),
	#endif
	#ifdef __NR_munmap
	SC_ALLOW(munmap),
	#endif
	#ifdef __NR__newselect
	SC_ALLOW(_newselect),
	#endif
	#ifdef __NR_poll
	SC_ALLOW(poll),
	#endif
	#ifdef __NR_pselect6
	SC_ALLOW(pselect6),
	#endif
	#ifdef __NR_read
	SC_ALLOW(read),
	#endif
	#ifdef __NR_rt_sigprocmask
	SC_ALLOW(rt_sigprocmask),
	#endif
	#ifdef __NR_select
	SC_ALLOW(select),
	#endif
	#ifdef __NR_shutdown
	SC_ALLOW(shutdown),
	#endif
	#ifdef __NR_sigprocmask
	SC_ALLOW(sigprocmask),
	#endif
	#ifdef __NR_time
	SC_ALLOW(time),
	#endif
	#ifdef __NR_write
	SC_ALLOW(write),
	#endif
	#ifdef __NR_socketcall
	SC_ALLOW_ARG(socketcall, 0, SYS_SHUTDOWN),
	#endif

	/* Default deny */
	BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),
	};

	static const struct sock_fprog preauth_program = {
	.len = (unsigned short)(sizeof(preauth_insns)/sizeof(preauth_insns[0])),
	.filter = (struct sock_filter *)preauth_insns,
	};

	struct ssh_sandbox {
	pid_t child_pid;
	};

	struct ssh_sandbox *
	ssh_sandbox_init(struct monitor *monitor)
	{
	struct ssh_sandbox *box;

	/*
	* Strictly, we don't need to maintain any state here but we need
	* to return non-NULL to satisfy the API.
	*/
	debug3("%s: preparing seccomp filter sandbox", __func__);
	box = xcalloc(1, sizeof(*box));
	box->child_pid = 0;

	return box;
	}

	#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
	extern struct monitor *pmonitor;
	void mm_log_handler(LogLevel level, const char msg, void ctx);

	static void
	ssh_sandbox_violation(int signum, siginfo_t info, void void_context)
	{
	char msg[256];

	snprintf(msg, sizeof(msg),
	"%s: unexpected system call (arch:0x%x,syscall:%d @ %p)",
	__func__, info->si_arch, info->si_syscall, info->si_call_addr);
	mm_log_handler(SYSLOG_LEVEL_FATAL, msg, pmonitor);
	_exit(1);
	}

	static void
	ssh_sandbox_child_debugging(void)
	{
	struct sigaction act;
	sigset_t mask;

	debug3("%s: installing SIGSYS handler", __func__);
	memset(&act, 0, sizeof(act));
	sigemptyset(&mask);
	sigaddset(&mask, SIGSYS);

	act.sa_sigaction = &ssh_sandbox_violation;
	act.sa_flags = SA_SIGINFO;
	if (sigaction(SIGSYS, &act, NULL) == -1)
	fatal("%s: sigaction(SIGSYS): %s", __func__, strerror(errno));
	if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1)
	fatal("%s: sigprocmask(SIGSYS): %s",
	__func__, strerror(errno));
	}
	#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */

	void
	ssh_sandbox_child(struct ssh_sandbox *box)
	{
	struct rlimit rl_zero;
	int nnp_failed = 0;

	/* Set rlimits for completeness if possible. */
	rl_zero.rlim_cur = rl_zero.rlim_max = 0;
	if (setrlimit(RLIMIT_FSIZE, &rl_zero) == -1)
	fatal("%s: setrlimit(RLIMIT_FSIZE, { 0, 0 }): %s",
	__func__, strerror(errno));
	if (setrlimit(RLIMIT_NOFILE, &rl_zero) == -1)
	fatal("%s: setrlimit(RLIMIT_NOFILE, { 0, 0 }): %s",
	__func__, strerror(errno));
	if (setrlimit(RLIMIT_NPROC, &rl_zero) == -1)
	fatal("%s: setrlimit(RLIMIT_NPROC, { 0, 0 }): %s",
	__func__, strerror(errno));

	#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
	ssh_sandbox_child_debugging();
	#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */

	debug3("%s: setting PR_SET_NO_NEW_PRIVS", __func__);
	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) {
	debug("%s: prctl(PR_SET_NO_NEW_PRIVS): %s",
	__func__, strerror(errno));
	nnp_failed = 1;
	}
	debug3("%s: attaching seccomp filter program", __func__);
	if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &preauth_program) == -1)
	debug("%s: prctl(PR_SET_SECCOMP): %s",
	__func__, strerror(errno));
	else if (nnp_failed)
	fatal("%s: SECCOMP_MODE_FILTER activated but "
	"PR_SET_NO_NEW_PRIVS failed", __func__);
	}

	void
	ssh_sandbox_parent_finish(struct ssh_sandbox *box)
	{
	free(box);
	debug3("%s: finished", __func__);
	}

	void
	ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
	{
	box->child_pid = child_pid;
	}

	#endif /* SANDBOX_SECCOMP_FILTER */