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/***
This file is part of systemd.
Copyright 2016 Lennart Poettering
systemd 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 2.1 of the License, or
(at your option) any later version.
systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <linux/netlink.h>
#include <sys/capability.h>
#include <sys/types.h>
#ifdef HAVE_SECCOMP
#include <seccomp.h>
#endif
#include "alloc-util.h"
#include "log.h"
#include "nspawn-seccomp.h"
#ifdef HAVE_SECCOMP
#include "seccomp-util.h"
#endif
#include "string-util.h"
#ifdef HAVE_SECCOMP
static int seccomp_add_default_syscall_filter(
scmp_filter_ctx ctx,
uint32_t arch,
uint64_t cap_list_retain) {
static const struct {
uint64_t capability;
int syscall_num;
} blacklist[] = {
{ 0, SCMP_SYS(_sysctl) }, /* obsolete syscall */
{ 0, SCMP_SYS(add_key) }, /* keyring is not namespaced */
{ 0, SCMP_SYS(afs_syscall) }, /* obsolete syscall */
{ 0, SCMP_SYS(bdflush) },
#ifdef __NR_bpf
{ 0, SCMP_SYS(bpf) },
#endif
{ 0, SCMP_SYS(break) }, /* obsolete syscall */
{ 0, SCMP_SYS(create_module) }, /* obsolete syscall */
{ 0, SCMP_SYS(ftime) }, /* obsolete syscall */
{ 0, SCMP_SYS(get_kernel_syms) }, /* obsolete syscall */
{ 0, SCMP_SYS(getpmsg) }, /* obsolete syscall */
{ 0, SCMP_SYS(gtty) }, /* obsolete syscall */
#ifdef __NR_kexec_file_load
{ 0, SCMP_SYS(kexec_file_load) },
#endif
{ 0, SCMP_SYS(kexec_load) },
{ 0, SCMP_SYS(keyctl) }, /* keyring is not namespaced */
{ 0, SCMP_SYS(lock) }, /* obsolete syscall */
{ 0, SCMP_SYS(lookup_dcookie) },
{ 0, SCMP_SYS(mpx) }, /* obsolete syscall */
{ 0, SCMP_SYS(nfsservctl) }, /* obsolete syscall */
{ 0, SCMP_SYS(open_by_handle_at) },
{ 0, SCMP_SYS(perf_event_open) },
{ 0, SCMP_SYS(prof) }, /* obsolete syscall */
{ 0, SCMP_SYS(profil) }, /* obsolete syscall */
{ 0, SCMP_SYS(putpmsg) }, /* obsolete syscall */
{ 0, SCMP_SYS(query_module) }, /* obsolete syscall */
{ 0, SCMP_SYS(quotactl) },
{ 0, SCMP_SYS(request_key) }, /* keyring is not namespaced */
{ 0, SCMP_SYS(security) }, /* obsolete syscall */
{ 0, SCMP_SYS(sgetmask) }, /* obsolete syscall */
{ 0, SCMP_SYS(ssetmask) }, /* obsolete syscall */
{ 0, SCMP_SYS(stty) }, /* obsolete syscall */
{ 0, SCMP_SYS(swapoff) },
{ 0, SCMP_SYS(swapon) },
{ 0, SCMP_SYS(sysfs) }, /* obsolete syscall */
{ 0, SCMP_SYS(tuxcall) }, /* obsolete syscall */
{ 0, SCMP_SYS(ulimit) }, /* obsolete syscall */
{ 0, SCMP_SYS(uselib) }, /* obsolete syscall */
{ 0, SCMP_SYS(ustat) }, /* obsolete syscall */
{ 0, SCMP_SYS(vserver) }, /* obsolete syscall */
{ CAP_SYSLOG, SCMP_SYS(syslog) },
{ CAP_SYS_MODULE, SCMP_SYS(delete_module) },
{ CAP_SYS_MODULE, SCMP_SYS(finit_module) },
{ CAP_SYS_MODULE, SCMP_SYS(init_module) },
{ CAP_SYS_PACCT, SCMP_SYS(acct) },
{ CAP_SYS_PTRACE, SCMP_SYS(process_vm_readv) },
{ CAP_SYS_PTRACE, SCMP_SYS(process_vm_writev) },
{ CAP_SYS_PTRACE, SCMP_SYS(ptrace) },
{ CAP_SYS_RAWIO, SCMP_SYS(ioperm) },
{ CAP_SYS_RAWIO, SCMP_SYS(iopl) },
{ CAP_SYS_RAWIO, SCMP_SYS(pciconfig_iobase) },
{ CAP_SYS_RAWIO, SCMP_SYS(pciconfig_read) },
{ CAP_SYS_RAWIO, SCMP_SYS(pciconfig_write) },
#ifdef __NR_s390_pci_mmio_read
{ CAP_SYS_RAWIO, SCMP_SYS(s390_pci_mmio_read) },
#endif
#ifdef __NR_s390_pci_mmio_write
{ CAP_SYS_RAWIO, SCMP_SYS(s390_pci_mmio_write) },
#endif
{ CAP_SYS_TIME, SCMP_SYS(adjtimex) },
{ CAP_SYS_TIME, SCMP_SYS(clock_adjtime) },
{ CAP_SYS_TIME, SCMP_SYS(clock_settime) },
{ CAP_SYS_TIME, SCMP_SYS(settimeofday) },
{ CAP_SYS_TIME, SCMP_SYS(stime) },
};
unsigned i;
int r, c = 0;
for (i = 0; i < ELEMENTSOF(blacklist); i++) {
if (blacklist[i].capability != 0 && (cap_list_retain & (1ULL << blacklist[i].capability)))
continue;
r = seccomp_rule_add_exact(ctx, SCMP_ACT_ERRNO(EPERM), blacklist[i].syscall_num, 0);
if (r < 0) {
/* If the system call is not known on this architecture, then that's fine, let's ignore it */
_cleanup_free_ char *n = NULL;
n = seccomp_syscall_resolve_num_arch(arch, blacklist[i].syscall_num);
log_debug_errno(r, "Failed to add rule for system call %s, ignoring: %m", strna(n));
} else
c++;
}
return c;
}
int setup_seccomp(uint64_t cap_list_retain) {
uint32_t arch;
int r;
if (!is_seccomp_available()) {
log_debug("SECCOMP features not detected in the kernel, disabling SECCOMP audit filter");
return 0;
}
SECCOMP_FOREACH_LOCAL_ARCH(arch) {
_cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
int n;
log_debug("Operating on architecture: %s", seccomp_arch_to_string(arch));
r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ALLOW);
if (r < 0)
return log_error_errno(r, "Failed to allocate seccomp object: %m");
n = seccomp_add_default_syscall_filter(seccomp, arch, cap_list_retain);
if (n < 0)
return n;
/*
Audit is broken in containers, much of the userspace audit hookup will fail if running inside a
container. We don't care and just turn off creation of audit sockets.
This will make socket(AF_NETLINK, *, NETLINK_AUDIT) fail with EAFNOSUPPORT which audit userspace uses
as indication that audit is disabled in the kernel.
*/
r = seccomp_rule_add_exact(
seccomp,
SCMP_ACT_ERRNO(EAFNOSUPPORT),
SCMP_SYS(socket),
2,
SCMP_A0(SCMP_CMP_EQ, AF_NETLINK),
SCMP_A2(SCMP_CMP_EQ, NETLINK_AUDIT));
if (r < 0)
log_debug_errno(r, "Failed to add audit seccomp rule, ignoring: %m");
else
n++;
if (n <= 0) /* no rule added? then skip this architecture */
continue;
r = seccomp_load(seccomp);
if (IN_SET(r, -EPERM, -EACCES))
return log_error_errno(r, "Failed to install seccomp audit filter: %m");
if (r < 0)
log_debug_errno(r, "Failed to install filter set for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
}
return 0;
}
#else
int setup_seccomp(uint64_t cap_list_retain) {
return 0;
}
#endif
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