280 lines
13 KiB
C
280 lines
13 KiB
C
/***
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This file is part of systemd.
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Copyright 2016 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <errno.h>
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#include <linux/netlink.h>
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#include <sys/capability.h>
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#include <sys/types.h>
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#if HAVE_SECCOMP
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#include <seccomp.h>
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#endif
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#include "alloc-util.h"
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#include "log.h"
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#include "nspawn-seccomp.h"
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#if HAVE_SECCOMP
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#include "seccomp-util.h"
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#endif
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#include "string-util.h"
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#include "strv.h"
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#if HAVE_SECCOMP
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static int seccomp_add_default_syscall_filter(
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scmp_filter_ctx ctx,
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uint32_t arch,
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uint64_t cap_list_retain,
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char **syscall_whitelist,
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char **syscall_blacklist) {
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static const struct {
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uint64_t capability;
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const char* name;
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} whitelist[] = {
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/* Let's use set names where we can */
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{ 0, "@basic-io" },
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{ 0, "@default" },
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{ 0, "@file-system" },
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{ 0, "@io-event" },
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{ 0, "@ipc" },
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{ 0, "@mount" },
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{ 0, "@network-io" },
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{ 0, "@process" },
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{ 0, "@resources" },
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{ 0, "@setuid" },
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{ 0, "@signal" },
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{ 0, "@timer" },
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/* The following four are sets we optionally enable, in case the caps have been configured for it */
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{ CAP_SYS_TIME, "@clock" },
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{ CAP_SYS_MODULE, "@module" },
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{ CAP_SYS_RAWIO, "@raw-io" },
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{ CAP_IPC_LOCK, "@memlock" },
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/* Plus a good set of additional syscalls which are not part of any of the groups above */
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{ 0, "brk" },
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{ 0, "capget" },
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{ 0, "capset" },
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{ 0, "chown" },
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{ 0, "chown32" },
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{ 0, "copy_file_range" },
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{ 0, "fadvise64" },
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{ 0, "fadvise64_64" },
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{ 0, "fchown" },
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{ 0, "fchown32" },
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{ 0, "fchownat" },
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{ 0, "fdatasync" },
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{ 0, "flock" },
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{ 0, "fsync" },
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{ 0, "get_mempolicy" },
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{ 0, "getcpu" },
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{ 0, "getpriority" },
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{ 0, "getrandom" },
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{ 0, "io_cancel" },
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{ 0, "io_destroy" },
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{ 0, "io_getevents" },
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{ 0, "io_setup" },
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{ 0, "io_submit" },
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{ 0, "ioctl" },
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{ 0, "ioprio_get" },
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{ 0, "kcmp" },
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{ 0, "lchown" },
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{ 0, "lchown32" },
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{ 0, "madvise" },
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{ 0, "mincore" },
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{ 0, "mprotect" },
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{ 0, "mremap" },
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{ 0, "msync" },
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{ 0, "name_to_handle_at" },
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{ 0, "oldolduname" },
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{ 0, "olduname" },
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{ 0, "personality" },
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{ 0, "preadv2" },
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{ 0, "pwritev2" },
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{ 0, "readahead" },
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{ 0, "readdir" },
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{ 0, "remap_file_pages" },
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{ 0, "sched_get_priority_max" },
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{ 0, "sched_get_priority_min" },
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{ 0, "sched_getaffinity" },
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{ 0, "sched_getattr" },
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{ 0, "sched_getparam" },
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{ 0, "sched_getscheduler" },
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{ 0, "sched_rr_get_interval" },
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{ 0, "sched_yield" },
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{ 0, "seccomp" },
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{ 0, "sendfile" },
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{ 0, "sendfile64" },
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{ 0, "setdomainname" },
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{ 0, "setfsgid" },
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{ 0, "setfsgid32" },
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{ 0, "setfsuid" },
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{ 0, "setfsuid32" },
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{ 0, "sethostname" },
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{ 0, "setpgid" },
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{ 0, "setsid" },
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{ 0, "splice" },
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{ 0, "sync" },
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{ 0, "sync_file_range" },
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{ 0, "syncfs" },
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{ 0, "sysinfo" },
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{ 0, "tee" },
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{ 0, "ugetrlimit" },
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{ 0, "umask" },
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{ 0, "uname" },
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{ 0, "userfaultfd" },
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{ 0, "vmsplice" },
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/* The following individual syscalls are added depending on specified caps */
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{ CAP_SYS_PACCT, "acct" },
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{ CAP_SYS_PTRACE, "process_vm_readv" },
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{ CAP_SYS_PTRACE, "process_vm_writev" },
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{ CAP_SYS_PTRACE, "ptrace" },
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{ CAP_SYS_BOOT, "reboot" },
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{ CAP_SYSLOG, "syslog" },
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{ CAP_SYS_TTY_CONFIG, "vhangup" },
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/*
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* The following syscalls and groups are knowingly excluded:
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*
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* @cpu-emulation
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* @keyring (NB: keyring is not namespaced!)
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* @obsolete
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* @swap
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*
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* bpf (NB: bpffs is not namespaced!)
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* fanotify_init
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* fanotify_mark
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* kexec_file_load
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* kexec_load
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* lookup_dcookie
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* nfsservctl
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* open_by_handle_at
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* perf_event_open
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* pkey_alloc
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* pkey_free
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* pkey_mprotect
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* quotactl
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*/
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};
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int r, c = 0;
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size_t i;
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char **p;
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for (i = 0; i < ELEMENTSOF(whitelist); i++) {
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if (whitelist[i].capability != 0 && (cap_list_retain & (1ULL << whitelist[i].capability)) == 0)
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continue;
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r = seccomp_add_syscall_filter_item(ctx, whitelist[i].name, SCMP_ACT_ALLOW, syscall_blacklist);
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if (r < 0)
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/* If the system call is not known on this architecture, then that's fine, let's ignore it */
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log_debug_errno(r, "Failed to add rule for system call %s on %s, ignoring: %m", whitelist[i].name, seccomp_arch_to_string(arch));
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else
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c++;
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}
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STRV_FOREACH(p, syscall_whitelist) {
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r = seccomp_add_syscall_filter_item(ctx, *p, SCMP_ACT_ALLOW, syscall_blacklist);
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if (r < 0)
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log_debug_errno(r, "Failed to add rule for system call %s on %s, ignoring: %m", *p, seccomp_arch_to_string(arch));
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else
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c++;
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}
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return c;
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}
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int setup_seccomp(uint64_t cap_list_retain, char **syscall_whitelist, char **syscall_blacklist) {
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uint32_t arch;
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int r;
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if (!is_seccomp_available()) {
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log_debug("SECCOMP features not detected in the kernel, disabling SECCOMP filterering");
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return 0;
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}
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SECCOMP_FOREACH_LOCAL_ARCH(arch) {
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_cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
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log_debug("Applying whitelist on architecture: %s", seccomp_arch_to_string(arch));
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r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ERRNO(EPERM));
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if (r < 0)
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return log_error_errno(r, "Failed to allocate seccomp object: %m");
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r = seccomp_add_default_syscall_filter(seccomp, arch, cap_list_retain, syscall_whitelist, syscall_blacklist);
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if (r < 0)
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return r;
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r = seccomp_load(seccomp);
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if (IN_SET(r, -EPERM, -EACCES))
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return log_error_errno(r, "Failed to install seccomp filter: %m");
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if (r < 0)
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log_debug_errno(r, "Failed to install filter set for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
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}
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SECCOMP_FOREACH_LOCAL_ARCH(arch) {
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_cleanup_(seccomp_releasep) scmp_filter_ctx seccomp = NULL;
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log_debug("Applying NETLINK_AUDIT mask on architecture: %s", seccomp_arch_to_string(arch));
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r = seccomp_init_for_arch(&seccomp, arch, SCMP_ACT_ALLOW);
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if (r < 0)
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return log_error_errno(r, "Failed to allocate seccomp object: %m");
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/*
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Audit is broken in containers, much of the userspace audit hookup will fail if running inside a
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container. We don't care and just turn off creation of audit sockets.
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This will make socket(AF_NETLINK, *, NETLINK_AUDIT) fail with EAFNOSUPPORT which audit userspace uses
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as indication that audit is disabled in the kernel.
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*/
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r = seccomp_rule_add_exact(
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seccomp,
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SCMP_ACT_ERRNO(EAFNOSUPPORT),
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SCMP_SYS(socket),
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2,
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SCMP_A0(SCMP_CMP_EQ, AF_NETLINK),
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SCMP_A2(SCMP_CMP_EQ, NETLINK_AUDIT));
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if (r < 0) {
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log_debug_errno(r, "Failed to add audit seccomp rule, ignoring: %m");
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continue;
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}
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r = seccomp_load(seccomp);
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if (IN_SET(r, -EPERM, -EACCES))
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return log_error_errno(r, "Failed to install seccomp audit filter: %m");
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if (r < 0)
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log_debug_errno(r, "Failed to install filter set for architecture %s, skipping: %m", seccomp_arch_to_string(arch));
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}
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return 0;
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}
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#else
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int setup_seccomp(uint64_t cap_list_retain, char **syscall_whitelist, char **syscall_blacklist) {
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return 0;
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}
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#endif
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