/* * 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 blacklist[] = { /* default set of syscalls to blacklist */ { 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; } 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(blacklist); i++) { uint32_t action; if (!(seccomp_opts & blacklist[i].set)) { continue; } action = qemu_seccomp_get_action(blacklist[i].set); rc = seccomp_rule_add_array(ctx, action, blacklist[i].num, blacklist[i].narg, blacklist[i].arg_cmp); if (rc < 0) { error_setg_errno(errp, -rc, "failed to add seccomp blacklist 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; } #ifdef CONFIG_SECCOMP 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); #endif