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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 "log.h"
#ifdef HAVE_SECCOMP
#include "seccomp-util.h"
#endif
#include "nspawn-seccomp.h"
#ifdef HAVE_SECCOMP
static int seccomp_add_default_syscall_filter(scmp_filter_ctx ctx,
uint64_t cap_list_retain) {
unsigned i;
int r;
static const struct {
uint64_t capability;
int syscall_num;
} blacklist[] = {
{ CAP_SYS_RAWIO, SCMP_SYS(iopl) },
{ CAP_SYS_RAWIO, SCMP_SYS(ioperm) },
{ CAP_SYS_BOOT, SCMP_SYS(kexec_load) },
{ CAP_SYS_ADMIN, SCMP_SYS(swapon) },
{ CAP_SYS_ADMIN, SCMP_SYS(swapoff) },
{ CAP_SYS_ADMIN, SCMP_SYS(open_by_handle_at) },
{ CAP_SYS_MODULE, SCMP_SYS(init_module) },
{ CAP_SYS_MODULE, SCMP_SYS(finit_module) },
{ CAP_SYS_MODULE, SCMP_SYS(delete_module) },
{ CAP_SYSLOG, SCMP_SYS(syslog) },
};
for (i = 0; i < ELEMENTSOF(blacklist); i++) {
if (cap_list_retain & (1ULL << blacklist[i].capability))
continue;
r = seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), blacklist[i].syscall_num, 0);
if (r == -EFAULT)
continue; /* unknown syscall */
if (r < 0) {
log_error_errno(r, "Failed to block syscall: %m");
return r;
}
}
return 0;
}
int setup_seccomp(uint64_t cap_list_retain) {
scmp_filter_ctx seccomp;
int r;
seccomp = seccomp_init(SCMP_ACT_ALLOW);
if (!seccomp)
return log_oom();
r = seccomp_add_secondary_archs(seccomp);
if (r < 0) {
log_error_errno(r, "Failed to add secondary archs to seccomp filter: %m");
goto finish;
}
r = seccomp_add_default_syscall_filter(seccomp, cap_list_retain);
if (r < 0)
goto finish;
/*
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(
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_error_errno(r, "Failed to add audit seccomp rule: %m");
goto finish;
}
r = seccomp_attr_set(seccomp, SCMP_FLTATR_CTL_NNP, 0);
if (r < 0) {
log_error_errno(r, "Failed to unset NO_NEW_PRIVS: %m");
goto finish;
}
r = seccomp_load(seccomp);
if (r == -EINVAL) {
log_debug_errno(r, "Kernel is probably not configured with CONFIG_SECCOMP. Disabling seccomp audit filter: %m");
r = 0;
goto finish;
}
if (r < 0) {
log_error_errno(r, "Failed to install seccomp audit filter: %m");
goto finish;
}
finish:
seccomp_release(seccomp);
return r;
}
#else
int setup_seccomp(uint64_t cap_list_retain) {
return 0;
}
#endif
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