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/* $OpenBSD: sandbox-systrace.c,v 1.4 2011/07/29 14:42:45 djm Exp $ */
/*
* Copyright (c) 2011 Damien Miller <djm@mindrot.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.
*/
#include "includes.h"
#ifdef SANDBOX_SYSTRACE
#include <sys/types.h>
#include <sys/param.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <sys/socket.h>
#include <dev/systrace.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "atomicio.h"
#include "log.h"
#include "ssh-sandbox.h"
#include "xmalloc.h"
struct sandbox_policy {
int syscall;
int action;
};
/* Permitted syscalls in preauth. Unlisted syscalls get SYSTR_POLICY_KILL */
static const struct sandbox_policy preauth_policy[] = {
{ SYS_open, SYSTR_POLICY_NEVER },
{ SYS___sysctl, SYSTR_POLICY_PERMIT },
{ SYS_close, SYSTR_POLICY_PERMIT },
{ SYS_exit, SYSTR_POLICY_PERMIT },
{ SYS_getpid, SYSTR_POLICY_PERMIT },
{ SYS_gettimeofday, SYSTR_POLICY_PERMIT },
{ SYS_madvise, SYSTR_POLICY_PERMIT },
{ SYS_mmap, SYSTR_POLICY_PERMIT },
{ SYS_mprotect, SYSTR_POLICY_PERMIT },
{ SYS_poll, SYSTR_POLICY_PERMIT },
{ SYS_munmap, SYSTR_POLICY_PERMIT },
{ SYS_read, SYSTR_POLICY_PERMIT },
{ SYS_select, SYSTR_POLICY_PERMIT },
{ SYS_sigprocmask, SYSTR_POLICY_PERMIT },
{ SYS_write, SYSTR_POLICY_PERMIT },
{ -1, -1 }
};
struct ssh_sandbox {
int child_sock;
int parent_sock;
int systrace_fd;
pid_t child_pid;
};
struct ssh_sandbox *
ssh_sandbox_init(void)
{
struct ssh_sandbox *box;
int s[2];
debug3("%s: preparing systrace sandbox", __func__);
box = xcalloc(1, sizeof(*box));
if (socketpair(AF_UNIX, SOCK_STREAM, 0, s) == -1)
fatal("%s: socketpair: %s", __func__, strerror(errno));
box->child_sock = s[0];
box->parent_sock = s[1];
box->systrace_fd = -1;
box->child_pid = 0;
return box;
}
void
ssh_sandbox_child(struct ssh_sandbox *box)
{
char whatever = 0;
close(box->parent_sock);
/* Signal parent that we are ready */
debug3("%s: ready", __func__);
if (atomicio(vwrite, box->child_sock, &whatever, 1) != 1)
fatal("%s: write: %s", __func__, strerror(errno));
/* Wait for parent to signal for us to go */
if (atomicio(read, box->child_sock, &whatever, 1) != 1)
fatal("%s: read: %s", __func__, strerror(errno));
debug3("%s: started", __func__);
close(box->child_sock);
}
static void
ssh_sandbox_parent(struct ssh_sandbox *box, pid_t child_pid,
const struct sandbox_policy *allowed_syscalls)
{
int dev_systrace, i, j, found;
char whatever = 0;
struct systrace_policy policy;
debug3("%s: wait for child %ld", __func__, (long)child_pid);
box->child_pid = child_pid;
close(box->child_sock);
/* Wait for child to signal that it is ready */
if (atomicio(read, box->parent_sock, &whatever, 1) != 1)
fatal("%s: read: %s", __func__, strerror(errno));
debug3("%s: child %ld ready", __func__, (long)child_pid);
/* Set up systracing of child */
if ((dev_systrace = open("/dev/systrace", O_RDONLY)) == -1)
fatal("%s: open(\"/dev/systrace\"): %s", __func__,
strerror(errno));
if (ioctl(dev_systrace, STRIOCCLONE, &box->systrace_fd) == -1)
fatal("%s: ioctl(STRIOCCLONE, %d): %s", __func__,
dev_systrace, strerror(errno));
close(dev_systrace);
debug3("%s: systrace attach, fd=%d", __func__, box->systrace_fd);
if (ioctl(box->systrace_fd, STRIOCATTACH, &child_pid) == -1)
fatal("%s: ioctl(%d, STRIOCATTACH, %d): %s", __func__,
box->systrace_fd, child_pid, strerror(errno));
/* Allocate and assign policy */
bzero(&policy, sizeof(policy));
policy.strp_op = SYSTR_POLICY_NEW;
policy.strp_maxents = SYS_MAXSYSCALL;
if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
fatal("%s: ioctl(%d, STRIOCPOLICY (new)): %s", __func__,
box->systrace_fd, strerror(errno));
policy.strp_op = SYSTR_POLICY_ASSIGN;
policy.strp_pid = box->child_pid;
if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
fatal("%s: ioctl(%d, STRIOCPOLICY (assign)): %s",
__func__, box->systrace_fd, strerror(errno));
/* Set per-syscall policy */
for (i = 0; i < SYS_MAXSYSCALL; i++) {
found = 0;
for (j = 0; allowed_syscalls[j].syscall != -1; j++) {
if (allowed_syscalls[j].syscall == i) {
found = 1;
break;
}
}
policy.strp_op = SYSTR_POLICY_MODIFY;
policy.strp_code = i;
policy.strp_policy = found ?
allowed_syscalls[j].action : SYSTR_POLICY_KILL;
if (found)
debug3("%s: policy: enable syscall %d", __func__, i);
if (ioctl(box->systrace_fd, STRIOCPOLICY, &policy) == -1)
fatal("%s: ioctl(%d, STRIOCPOLICY (modify)): %s",
__func__, box->systrace_fd, strerror(errno));
}
/* Signal the child to start running */
debug3("%s: start child %ld", __func__, (long)child_pid);
if (atomicio(vwrite, box->parent_sock, &whatever, 1) != 1)
fatal("%s: write: %s", __func__, strerror(errno));
close(box->parent_sock);
}
void
ssh_sandbox_parent_finish(struct ssh_sandbox *box)
{
/* Closing this before the child exits will terminate it */
close(box->systrace_fd);
free(box);
debug3("%s: finished", __func__);
}
void
ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
{
ssh_sandbox_parent(box, child_pid, preauth_policy);
}
#endif /* SANDBOX_SYSTRACE */