| /* |
| * QEMU seccomp mode 2 support with libseccomp |
| * |
| * Copyright IBM, Corp. 2012 |
| * |
| * Authors: |
| * Eduardo Otubo <eotubo@br.ibm.com> |
| * |
| * This work is licensed under the terms of the GNU GPL, version 2. See |
| * the COPYING file in the top-level directory. |
| * |
| * Contributions after 2012-01-13 are licensed under the terms of the |
| * GNU GPL, version 2 or (at your option) any later version. |
| */ |
| |
| #include "qemu/osdep.h" |
| #include "qapi/error.h" |
| #include "qemu/config-file.h" |
| #include "qemu/option.h" |
| #include "qemu/module.h" |
| #include <sys/prctl.h> |
| #include <seccomp.h> |
| #include "sysemu/seccomp.h" |
| #include <linux/seccomp.h> |
| |
| /* For some architectures (notably ARM) cacheflush is not supported until |
| * libseccomp 2.2.3, but configure enforces that we are using a more recent |
| * version on those hosts, so it is OK for this check to be less strict. |
| */ |
| #if SCMP_VER_MAJOR >= 3 |
| #define HAVE_CACHEFLUSH |
| #elif SCMP_VER_MAJOR == 2 && SCMP_VER_MINOR >= 2 |
| #define HAVE_CACHEFLUSH |
| #endif |
| |
| struct QemuSeccompSyscall { |
| int32_t num; |
| uint8_t set; |
| uint8_t narg; |
| const struct scmp_arg_cmp *arg_cmp; |
| }; |
| |
| const struct scmp_arg_cmp sched_setscheduler_arg[] = { |
| /* was SCMP_A1(SCMP_CMP_NE, SCHED_IDLE), but expanded due to GCC 4.x bug */ |
| { .arg = 1, .op = SCMP_CMP_NE, .datum_a = SCHED_IDLE } |
| }; |
| |
| static const struct QemuSeccompSyscall denylist[] = { |
| /* default set of syscalls that should get blocked */ |
| { SCMP_SYS(reboot), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(swapon), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(swapoff), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(syslog), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(mount), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(umount), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(kexec_load), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(afs_syscall), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(break), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(ftime), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(getpmsg), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(gtty), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(lock), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(mpx), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(prof), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(profil), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(putpmsg), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(security), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(stty), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(tuxcall), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(ulimit), QEMU_SECCOMP_SET_DEFAULT }, |
| { SCMP_SYS(vserver), QEMU_SECCOMP_SET_DEFAULT }, |
| /* obsolete */ |
| { SCMP_SYS(readdir), QEMU_SECCOMP_SET_OBSOLETE }, |
| { SCMP_SYS(_sysctl), QEMU_SECCOMP_SET_OBSOLETE }, |
| { SCMP_SYS(bdflush), QEMU_SECCOMP_SET_OBSOLETE }, |
| { SCMP_SYS(create_module), QEMU_SECCOMP_SET_OBSOLETE }, |
| { SCMP_SYS(get_kernel_syms), QEMU_SECCOMP_SET_OBSOLETE }, |
| { SCMP_SYS(query_module), QEMU_SECCOMP_SET_OBSOLETE }, |
| { SCMP_SYS(sgetmask), QEMU_SECCOMP_SET_OBSOLETE }, |
| { SCMP_SYS(ssetmask), QEMU_SECCOMP_SET_OBSOLETE }, |
| { SCMP_SYS(sysfs), QEMU_SECCOMP_SET_OBSOLETE }, |
| { SCMP_SYS(uselib), QEMU_SECCOMP_SET_OBSOLETE }, |
| { SCMP_SYS(ustat), QEMU_SECCOMP_SET_OBSOLETE }, |
| /* privileged */ |
| { SCMP_SYS(setuid), QEMU_SECCOMP_SET_PRIVILEGED }, |
| { SCMP_SYS(setgid), QEMU_SECCOMP_SET_PRIVILEGED }, |
| { SCMP_SYS(setpgid), QEMU_SECCOMP_SET_PRIVILEGED }, |
| { SCMP_SYS(setsid), QEMU_SECCOMP_SET_PRIVILEGED }, |
| { SCMP_SYS(setreuid), QEMU_SECCOMP_SET_PRIVILEGED }, |
| { SCMP_SYS(setregid), QEMU_SECCOMP_SET_PRIVILEGED }, |
| { SCMP_SYS(setresuid), QEMU_SECCOMP_SET_PRIVILEGED }, |
| { SCMP_SYS(setresgid), QEMU_SECCOMP_SET_PRIVILEGED }, |
| { SCMP_SYS(setfsuid), QEMU_SECCOMP_SET_PRIVILEGED }, |
| { SCMP_SYS(setfsgid), QEMU_SECCOMP_SET_PRIVILEGED }, |
| /* spawn */ |
| { SCMP_SYS(fork), QEMU_SECCOMP_SET_SPAWN }, |
| { SCMP_SYS(vfork), QEMU_SECCOMP_SET_SPAWN }, |
| { SCMP_SYS(execve), QEMU_SECCOMP_SET_SPAWN }, |
| /* resource control */ |
| { SCMP_SYS(getpriority), QEMU_SECCOMP_SET_RESOURCECTL }, |
| { SCMP_SYS(setpriority), QEMU_SECCOMP_SET_RESOURCECTL }, |
| { SCMP_SYS(sched_setparam), QEMU_SECCOMP_SET_RESOURCECTL }, |
| { SCMP_SYS(sched_getparam), QEMU_SECCOMP_SET_RESOURCECTL }, |
| { SCMP_SYS(sched_setscheduler), QEMU_SECCOMP_SET_RESOURCECTL, |
| ARRAY_SIZE(sched_setscheduler_arg), sched_setscheduler_arg }, |
| { SCMP_SYS(sched_getscheduler), QEMU_SECCOMP_SET_RESOURCECTL }, |
| { SCMP_SYS(sched_setaffinity), QEMU_SECCOMP_SET_RESOURCECTL }, |
| { SCMP_SYS(sched_getaffinity), QEMU_SECCOMP_SET_RESOURCECTL }, |
| { SCMP_SYS(sched_get_priority_max), QEMU_SECCOMP_SET_RESOURCECTL }, |
| { SCMP_SYS(sched_get_priority_min), QEMU_SECCOMP_SET_RESOURCECTL }, |
| }; |
| |
| static inline __attribute__((unused)) int |
| qemu_seccomp(unsigned int operation, unsigned int flags, void *args) |
| { |
| #ifdef __NR_seccomp |
| return syscall(__NR_seccomp, operation, flags, args); |
| #else |
| errno = ENOSYS; |
| return -1; |
| #endif |
| } |
| |
| static uint32_t qemu_seccomp_get_action(int set) |
| { |
| switch (set) { |
| case QEMU_SECCOMP_SET_DEFAULT: |
| case QEMU_SECCOMP_SET_OBSOLETE: |
| case QEMU_SECCOMP_SET_PRIVILEGED: |
| case QEMU_SECCOMP_SET_SPAWN: { |
| #if defined(SECCOMP_GET_ACTION_AVAIL) && defined(SCMP_ACT_KILL_PROCESS) && \ |
| defined(SECCOMP_RET_KILL_PROCESS) |
| static int kill_process = -1; |
| if (kill_process == -1) { |
| uint32_t action = SECCOMP_RET_KILL_PROCESS; |
| |
| if (qemu_seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &action) == 0) { |
| kill_process = 1; |
| } else { |
| kill_process = 0; |
| } |
| } |
| if (kill_process == 1) { |
| return SCMP_ACT_KILL_PROCESS; |
| } |
| #endif |
| return SCMP_ACT_TRAP; |
| } |
| |
| case QEMU_SECCOMP_SET_RESOURCECTL: |
| return SCMP_ACT_ERRNO(EPERM); |
| |
| default: |
| g_assert_not_reached(); |
| } |
| } |
| |
| |
| static int seccomp_start(uint32_t seccomp_opts, Error **errp) |
| { |
| int rc = -1; |
| unsigned int i = 0; |
| scmp_filter_ctx ctx; |
| |
| ctx = seccomp_init(SCMP_ACT_ALLOW); |
| if (ctx == NULL) { |
| error_setg(errp, "failed to initialize seccomp context"); |
| goto seccomp_return; |
| } |
| |
| rc = seccomp_attr_set(ctx, SCMP_FLTATR_CTL_TSYNC, 1); |
| if (rc != 0) { |
| error_setg_errno(errp, -rc, |
| "failed to set seccomp thread synchronization"); |
| goto seccomp_return; |
| } |
| |
| for (i = 0; i < ARRAY_SIZE(denylist); i++) { |
| uint32_t action; |
| if (!(seccomp_opts & denylist[i].set)) { |
| continue; |
| } |
| |
| action = qemu_seccomp_get_action(denylist[i].set); |
| rc = seccomp_rule_add_array(ctx, action, denylist[i].num, |
| denylist[i].narg, denylist[i].arg_cmp); |
| if (rc < 0) { |
| error_setg_errno(errp, -rc, |
| "failed to add seccomp denylist rules"); |
| goto seccomp_return; |
| } |
| } |
| |
| rc = seccomp_load(ctx); |
| if (rc < 0) { |
| error_setg_errno(errp, -rc, |
| "failed to load seccomp syscall filter in kernel"); |
| } |
| |
| seccomp_return: |
| seccomp_release(ctx); |
| return rc < 0 ? -1 : 0; |
| } |
| |
| int parse_sandbox(void *opaque, QemuOpts *opts, Error **errp) |
| { |
| if (qemu_opt_get_bool(opts, "enable", false)) { |
| uint32_t seccomp_opts = QEMU_SECCOMP_SET_DEFAULT |
| | QEMU_SECCOMP_SET_OBSOLETE; |
| const char *value = NULL; |
| |
| value = qemu_opt_get(opts, "obsolete"); |
| if (value) { |
| if (g_str_equal(value, "allow")) { |
| seccomp_opts &= ~QEMU_SECCOMP_SET_OBSOLETE; |
| } else if (g_str_equal(value, "deny")) { |
| /* this is the default option, this if is here |
| * to provide a little bit of consistency for |
| * the command line */ |
| } else { |
| error_setg(errp, "invalid argument for obsolete"); |
| return -1; |
| } |
| } |
| |
| value = qemu_opt_get(opts, "elevateprivileges"); |
| if (value) { |
| if (g_str_equal(value, "deny")) { |
| seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED; |
| } else if (g_str_equal(value, "children")) { |
| seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED; |
| |
| /* calling prctl directly because we're |
| * not sure if host has CAP_SYS_ADMIN set*/ |
| if (prctl(PR_SET_NO_NEW_PRIVS, 1)) { |
| error_setg(errp, "failed to set no_new_privs aborting"); |
| return -1; |
| } |
| } else if (g_str_equal(value, "allow")) { |
| /* default value */ |
| } else { |
| error_setg(errp, "invalid argument for elevateprivileges"); |
| return -1; |
| } |
| } |
| |
| value = qemu_opt_get(opts, "spawn"); |
| if (value) { |
| if (g_str_equal(value, "deny")) { |
| seccomp_opts |= QEMU_SECCOMP_SET_SPAWN; |
| } else if (g_str_equal(value, "allow")) { |
| /* default value */ |
| } else { |
| error_setg(errp, "invalid argument for spawn"); |
| return -1; |
| } |
| } |
| |
| value = qemu_opt_get(opts, "resourcecontrol"); |
| if (value) { |
| if (g_str_equal(value, "deny")) { |
| seccomp_opts |= QEMU_SECCOMP_SET_RESOURCECTL; |
| } else if (g_str_equal(value, "allow")) { |
| /* default value */ |
| } else { |
| error_setg(errp, "invalid argument for resourcecontrol"); |
| return -1; |
| } |
| } |
| |
| if (seccomp_start(seccomp_opts, errp) < 0) { |
| return -1; |
| } |
| } |
| |
| return 0; |
| } |
| |
| static QemuOptsList qemu_sandbox_opts = { |
| .name = "sandbox", |
| .implied_opt_name = "enable", |
| .head = QTAILQ_HEAD_INITIALIZER(qemu_sandbox_opts.head), |
| .desc = { |
| { |
| .name = "enable", |
| .type = QEMU_OPT_BOOL, |
| }, |
| { |
| .name = "obsolete", |
| .type = QEMU_OPT_STRING, |
| }, |
| { |
| .name = "elevateprivileges", |
| .type = QEMU_OPT_STRING, |
| }, |
| { |
| .name = "spawn", |
| .type = QEMU_OPT_STRING, |
| }, |
| { |
| .name = "resourcecontrol", |
| .type = QEMU_OPT_STRING, |
| }, |
| { /* end of list */ } |
| }, |
| }; |
| |
| static void seccomp_register(void) |
| { |
| bool add = false; |
| |
| /* FIXME: use seccomp_api_get() >= 2 check when released */ |
| |
| #if defined(SECCOMP_FILTER_FLAG_TSYNC) |
| int check; |
| |
| /* check host TSYNC capability, it returns errno == ENOSYS if unavailable */ |
| check = qemu_seccomp(SECCOMP_SET_MODE_FILTER, |
| SECCOMP_FILTER_FLAG_TSYNC, NULL); |
| if (check < 0 && errno == EFAULT) { |
| add = true; |
| } |
| #endif |
| |
| if (add) { |
| qemu_add_opts(&qemu_sandbox_opts); |
| } |
| } |
| opts_init(seccomp_register); |
