220 lines
6.3 KiB
C
220 lines
6.3 KiB
C
/* $OpenBSD: sandbox-systrace.c,v 1.18 2015/10/02 01:39:26 deraadt 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/ioctl.h>
|
|
#include <sys/syscall.h>
|
|
#include <sys/socket.h>
|
|
#include <sys/wait.h>
|
|
|
|
#include <dev/systrace.h>
|
|
|
|
#include <errno.h>
|
|
#include <fcntl.h>
|
|
#include <limits.h>
|
|
#include <signal.h>
|
|
#include <stdarg.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <unistd.h>
|
|
#include <limits.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_exit, SYSTR_POLICY_PERMIT },
|
|
#ifdef SYS_kbind
|
|
{ SYS_kbind, SYSTR_POLICY_PERMIT },
|
|
#endif
|
|
|
|
{ SYS_getpid, SYSTR_POLICY_PERMIT },
|
|
{ SYS_getpgid, SYSTR_POLICY_PERMIT },
|
|
{ SYS_clock_gettime, SYSTR_POLICY_PERMIT },
|
|
{ SYS_gettimeofday, SYSTR_POLICY_PERMIT },
|
|
{ SYS_nanosleep, SYSTR_POLICY_PERMIT },
|
|
{ SYS_sigprocmask, SYSTR_POLICY_PERMIT },
|
|
|
|
#ifdef SYS_getentropy
|
|
/* OpenBSD 5.6 and newer use getentropy(2) to seed arc4random(3). */
|
|
{ SYS_getentropy, SYSTR_POLICY_PERMIT },
|
|
#else
|
|
/* Previous releases used sysctl(3)'s kern.arnd variable. */
|
|
{ SYS___sysctl, SYSTR_POLICY_PERMIT },
|
|
#endif
|
|
#ifdef SYS_sendsyslog
|
|
{ SYS_sendsyslog, SYSTR_POLICY_PERMIT },
|
|
#endif
|
|
|
|
{ SYS_madvise, SYSTR_POLICY_PERMIT },
|
|
{ SYS_mmap, SYSTR_POLICY_PERMIT },
|
|
{ SYS_mprotect, SYSTR_POLICY_PERMIT },
|
|
{ SYS_mquery, SYSTR_POLICY_PERMIT },
|
|
{ SYS_munmap, SYSTR_POLICY_PERMIT },
|
|
|
|
{ SYS_poll, SYSTR_POLICY_PERMIT },
|
|
{ SYS_select, SYSTR_POLICY_PERMIT },
|
|
{ SYS_read, SYSTR_POLICY_PERMIT },
|
|
{ SYS_write, SYSTR_POLICY_PERMIT },
|
|
{ SYS_shutdown, SYSTR_POLICY_PERMIT },
|
|
{ SYS_close, SYSTR_POLICY_PERMIT },
|
|
|
|
{ SYS_open, SYSTR_POLICY_NEVER },
|
|
|
|
{ -1, -1 }
|
|
};
|
|
|
|
struct ssh_sandbox {
|
|
int systrace_fd;
|
|
pid_t child_pid;
|
|
void (*osigchld)(int);
|
|
};
|
|
|
|
struct ssh_sandbox *
|
|
ssh_sandbox_init(struct monitor *monitor)
|
|
{
|
|
struct ssh_sandbox *box;
|
|
|
|
debug3("%s: preparing systrace sandbox", __func__);
|
|
box = xcalloc(1, sizeof(*box));
|
|
box->systrace_fd = -1;
|
|
box->child_pid = 0;
|
|
box->osigchld = signal(SIGCHLD, SIG_IGN);
|
|
|
|
return box;
|
|
}
|
|
|
|
void
|
|
ssh_sandbox_child(struct ssh_sandbox *box)
|
|
{
|
|
debug3("%s: ready", __func__);
|
|
signal(SIGCHLD, box->osigchld);
|
|
if (kill(getpid(), SIGSTOP) != 0)
|
|
fatal("%s: kill(%d, SIGSTOP)", __func__, getpid());
|
|
debug3("%s: started", __func__);
|
|
}
|
|
|
|
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, status;
|
|
pid_t pid;
|
|
struct systrace_policy policy;
|
|
|
|
/* Wait for the child to send itself a SIGSTOP */
|
|
debug3("%s: wait for child %ld", __func__, (long)child_pid);
|
|
do {
|
|
pid = waitpid(child_pid, &status, WUNTRACED);
|
|
} while (pid == -1 && errno == EINTR);
|
|
signal(SIGCHLD, box->osigchld);
|
|
if (!WIFSTOPPED(status)) {
|
|
if (WIFSIGNALED(status))
|
|
fatal("%s: child terminated with signal %d",
|
|
__func__, WTERMSIG(status));
|
|
if (WIFEXITED(status))
|
|
fatal("%s: child exited with status %d",
|
|
__func__, WEXITSTATUS(status));
|
|
fatal("%s: child not stopped", __func__);
|
|
}
|
|
debug3("%s: child %ld stopped", __func__, (long)child_pid);
|
|
box->child_pid = 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 */
|
|
memset(&policy, 0, 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 (kill(box->child_pid, SIGCONT) != 0)
|
|
fatal("%s: kill(%d, SIGCONT)", __func__, box->child_pid);
|
|
}
|
|
|
|
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 */
|