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/* Seccomp rules, originally from xdg-app, which looks clearly influenced
* by sandstorm-io/sandstorm/src/standstorm/supervisor.c++
*
* Copyright (C) 2014 Alexander Larsson
* Copyright (C) 2015 Colin Walters <walters@verbum.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include "config.h"
/* Core libc/linux-headers stuff */
#define _GNU_SOURCE
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <stdarg.h>
#include <string.h>
#include <assert.h>
#include <stdlib.h>
#include <stdarg.h>
#include <sys/types.h>
#include <sys/prctl.h>
#include <sys/fsuid.h>
#include <sys/mount.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/utsname.h>
#include <sched.h>
/* Seccomp */
#include <seccomp.h>
#define N_ELEMENTS(arr) (sizeof (arr) / sizeof ((arr)[0]))
#include "setup-seccomp.h"
static void
die_with_error (const char *format, ...)
{
va_list args;
int errsv;
errsv = errno;
va_start (args, format);
vfprintf (stderr, format, args);
va_end (args);
fprintf (stderr, ": %s\n", strerror (errsv));
exit (1);
}
static void
die (const char *format, ...)
{
va_list args;
va_start (args, format);
vfprintf (stderr, format, args);
va_end (args);
fprintf (stderr, "\n");
exit (1);
}
static void
die_oom (void)
{
die ("Out of memory");
}
/*
* We're calling this filter "v0" - any future additions or changes
* should become new versions. This helps ensure backwards
* compatibility for build systems.
*/
void
setup_seccomp_v0 (void)
{
scmp_filter_ctx seccomp;
/**** BEGIN NOTE ON CODE SHARING
*
* There are today a number of different Linux container
* implementations. That will likely continue for long into the
* future. But we can still try to share code, and it's important
* to do so because it affects what library and application writers
* can do, and we should support code portability between different
* container tools.
*
* This syscall blacklist is copied from xdg-app, which was in turn
* clearly influenced by the Sandstorm.io blacklist.
*
* If you make any changes here, I suggest sending the changes along
* to other sandbox maintainers. Using the libseccomp list is also
* an appropriate venue:
* https://groups.google.com/forum/#!topic/libseccomp
*
* A non-exhaustive list of links to container tooling that might
* want to share this blacklist:
*
* https://github.com/sandstorm-io/sandstorm
* in src/sandstorm/supervisor.c++
* http://cgit.freedesktop.org/xdg-app/xdg-app/
* in lib/xdg-app-helper.c
* https://git.gnome.org/browse/linux-user-chroot
* in src/setup-seccomp.c
*
**** END NOTE ON CODE SHARING
*/
struct {
int scall;
struct scmp_arg_cmp *arg;
} syscall_blacklist[] = {
/* Block dmesg */
{SCMP_SYS(syslog)},
/* Useless old syscall */
{SCMP_SYS(uselib)},
/* Don't allow you to switch to bsd emulation or whatnot */
{SCMP_SYS(personality)},
/* Don't allow disabling accounting */
{SCMP_SYS(acct)},
/* 16-bit code is unnecessary in the sandbox, and modify_ldt is a
historic source of interesting information leaks. */
{SCMP_SYS(modify_ldt)},
/* Don't allow reading current quota use */
{SCMP_SYS(quotactl)},
/* Scary VM/NUMA ops */
{SCMP_SYS(move_pages)},
{SCMP_SYS(mbind)},
{SCMP_SYS(get_mempolicy)},
{SCMP_SYS(set_mempolicy)},
{SCMP_SYS(migrate_pages)},
/* Don't allow subnamespace setups: */
{SCMP_SYS(unshare)},
{SCMP_SYS(mount)},
{SCMP_SYS(pivot_root)},
{SCMP_SYS(clone), &SCMP_A0(SCMP_CMP_MASKED_EQ, CLONE_NEWUSER, CLONE_NEWUSER)},
/* Profiling operations; we expect these to be done by tools from outside
* the sandbox. In particular perf has been the source of many CVEs.
*/
{SCMP_SYS(perf_event_open)},
{SCMP_SYS(ptrace)}
};
/* Blacklist all but unix, inet, inet6 and netlink */
int socket_family_blacklist[] = {
AF_AX25,
AF_IPX,
AF_APPLETALK,
AF_NETROM,
AF_BRIDGE,
AF_ATMPVC,
AF_X25,
AF_ROSE,
AF_DECnet,
AF_NETBEUI,
AF_SECURITY,
AF_KEY,
AF_NETLINK + 1, /* Last gets CMP_GE, so order is important */
};
int i, r;
struct utsname uts;
seccomp = seccomp_init(SCMP_ACT_ALLOW);
if (!seccomp)
return die_oom ();
/* Add in all possible secondary archs we are aware of that
* this kernel might support. */
#if defined(__i386__) || defined(__x86_64__)
r = seccomp_arch_add (seccomp, SCMP_ARCH_X86);
if (r < 0 && r != -EEXIST)
die_with_error ("Failed to add x86 architecture to seccomp filter");
r = seccomp_arch_add (seccomp, SCMP_ARCH_X86_64);
if (r < 0 && r != -EEXIST)
die_with_error ("Failed to add x86_64 architecture to seccomp filter");
r = seccomp_arch_add (seccomp, SCMP_ARCH_X32);
if (r < 0 && r != -EEXIST)
die_with_error ("Failed to add x32 architecture to seccomp filter");
#endif
/* TODO: Should we filter the kernel keyring syscalls in some way?
* We do want them to be used by desktop apps, but they could also perhaps
* leak system stuff or secrets from other apps.
*/
for (i = 0; i < N_ELEMENTS (syscall_blacklist); i++)
{
int scall = syscall_blacklist[i].scall;
if (syscall_blacklist[i].arg)
r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO(EPERM), scall, 1, *syscall_blacklist[i].arg);
else
r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO(EPERM), scall, 0);
if (r < 0 && r == -EFAULT /* unknown syscall */)
die_with_error ("Failed to block syscall %d", scall);
}
/* Socket filtering doesn't work on x86 */
if (uname (&uts) == 0 && strcmp (uts.machine, "i686") != 0)
{
for (i = 0; i < N_ELEMENTS (socket_family_blacklist); i++)
{
int family = socket_family_blacklist[i];
if (i == N_ELEMENTS (socket_family_blacklist) - 1)
r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO(EAFNOSUPPORT), SCMP_SYS(socket), 1, SCMP_A0(SCMP_CMP_GE, family));
else
r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO(EAFNOSUPPORT), SCMP_SYS(socket), 1, SCMP_A0(SCMP_CMP_EQ, family));
if (r < 0)
die_with_error ("Failed to block socket family %d", family);
}
}
r = seccomp_load (seccomp);
if (r < 0)
die_with_error ("Failed to install seccomp audit filter: ");
seccomp_release (seccomp);
}
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