diff options
Diffstat (limited to 'system/qemu-seccomp.c')
| -rw-r--r-- | system/qemu-seccomp.c | 486 |
1 files changed, 486 insertions, 0 deletions
diff --git a/system/qemu-seccomp.c b/system/qemu-seccomp.c new file mode 100644 index 0000000..4d7439e --- /dev/null +++ b/system/qemu-seccomp.c @@ -0,0 +1,486 @@ +/* + * 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; + uint32_t action; +}; + +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 } +}; + +/* + * See 'NOTES' in 'man 2 clone' - s390 & cross have 'flags' in + * different position to other architectures + */ +#if defined(HOST_S390X) || defined(HOST_S390) || defined(HOST_CRIS) +#define CLONE_FLAGS_ARG 1 +#else +#define CLONE_FLAGS_ARG 0 +#endif + +#ifndef CLONE_PIDFD +# define CLONE_PIDFD 0x00001000 +#endif + +#define REQUIRE_CLONE_FLAG(flag) \ + const struct scmp_arg_cmp clone_arg ## flag[] = { \ + { .arg = CLONE_FLAGS_ARG, \ + .op = SCMP_CMP_MASKED_EQ, \ + .datum_a = flag, .datum_b = 0 } } + +#define FORBID_CLONE_FLAG(flag) \ + const struct scmp_arg_cmp clone_arg ## flag[] = { \ + { .arg = CLONE_FLAGS_ARG, \ + .op = SCMP_CMP_MASKED_EQ, \ + .datum_a = flag, .datum_b = flag } } + +#define RULE_CLONE_FLAG(flag) \ + { SCMP_SYS(clone), QEMU_SECCOMP_SET_SPAWN, \ + ARRAY_SIZE(clone_arg ## flag), clone_arg ## flag, SCMP_ACT_TRAP } + +/* If no CLONE_* flags are set, except CSIGNAL, deny */ +const struct scmp_arg_cmp clone_arg_none[] = { + { .arg = CLONE_FLAGS_ARG, + .op = SCMP_CMP_MASKED_EQ, + .datum_a = ~(CSIGNAL), .datum_b = 0 } +}; + +/* + * pthread_create should always set all of these. + */ +REQUIRE_CLONE_FLAG(CLONE_VM); +REQUIRE_CLONE_FLAG(CLONE_FS); +REQUIRE_CLONE_FLAG(CLONE_FILES); +REQUIRE_CLONE_FLAG(CLONE_SIGHAND); +REQUIRE_CLONE_FLAG(CLONE_THREAD); +REQUIRE_CLONE_FLAG(CLONE_SYSVSEM); +REQUIRE_CLONE_FLAG(CLONE_SETTLS); +REQUIRE_CLONE_FLAG(CLONE_PARENT_SETTID); +REQUIRE_CLONE_FLAG(CLONE_CHILD_CLEARTID); +/* + * Musl sets this in pthread_create too, but it is + * obsolete and harmless since its behaviour is + * subsumed under CLONE_THREAD + */ +/*REQUIRE_CLONE_FLAG(CLONE_DETACHED);*/ + + +/* + * These all indicate an attempt to spawn a process + * instead of a thread, or other undesirable scenarios + */ +FORBID_CLONE_FLAG(CLONE_PIDFD); +FORBID_CLONE_FLAG(CLONE_PTRACE); +FORBID_CLONE_FLAG(CLONE_VFORK); +FORBID_CLONE_FLAG(CLONE_PARENT); +FORBID_CLONE_FLAG(CLONE_NEWNS); +FORBID_CLONE_FLAG(CLONE_UNTRACED); +FORBID_CLONE_FLAG(CLONE_NEWCGROUP); +FORBID_CLONE_FLAG(CLONE_NEWUTS); +FORBID_CLONE_FLAG(CLONE_NEWIPC); +FORBID_CLONE_FLAG(CLONE_NEWUSER); +FORBID_CLONE_FLAG(CLONE_NEWPID); +FORBID_CLONE_FLAG(CLONE_NEWNET); +FORBID_CLONE_FLAG(CLONE_IO); + + +static const struct QemuSeccompSyscall denylist[] = { + /* default set of syscalls that should get blocked */ + { SCMP_SYS(reboot), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(swapon), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(swapoff), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(syslog), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(mount), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(umount), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(kexec_load), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(afs_syscall), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(break), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(ftime), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(getpmsg), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(gtty), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(lock), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(mpx), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(prof), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(profil), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(putpmsg), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(security), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(stty), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(tuxcall), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(ulimit), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(vserver), QEMU_SECCOMP_SET_DEFAULT, + 0, NULL, SCMP_ACT_TRAP }, + /* obsolete */ + { SCMP_SYS(readdir), QEMU_SECCOMP_SET_OBSOLETE, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(_sysctl), QEMU_SECCOMP_SET_OBSOLETE, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(bdflush), QEMU_SECCOMP_SET_OBSOLETE, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(create_module), QEMU_SECCOMP_SET_OBSOLETE, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(get_kernel_syms), QEMU_SECCOMP_SET_OBSOLETE, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(query_module), QEMU_SECCOMP_SET_OBSOLETE, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(sgetmask), QEMU_SECCOMP_SET_OBSOLETE, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(ssetmask), QEMU_SECCOMP_SET_OBSOLETE, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(sysfs), QEMU_SECCOMP_SET_OBSOLETE, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(uselib), QEMU_SECCOMP_SET_OBSOLETE, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(ustat), QEMU_SECCOMP_SET_OBSOLETE, + 0, NULL, SCMP_ACT_TRAP }, + /* privileged */ + { SCMP_SYS(setuid), QEMU_SECCOMP_SET_PRIVILEGED, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(setgid), QEMU_SECCOMP_SET_PRIVILEGED, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(setpgid), QEMU_SECCOMP_SET_PRIVILEGED, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(setsid), QEMU_SECCOMP_SET_PRIVILEGED, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(setreuid), QEMU_SECCOMP_SET_PRIVILEGED, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(setregid), QEMU_SECCOMP_SET_PRIVILEGED, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(setresuid), QEMU_SECCOMP_SET_PRIVILEGED, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(setresgid), QEMU_SECCOMP_SET_PRIVILEGED, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(setfsuid), QEMU_SECCOMP_SET_PRIVILEGED, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(setfsgid), QEMU_SECCOMP_SET_PRIVILEGED, + 0, NULL, SCMP_ACT_TRAP }, + /* spawn */ + { SCMP_SYS(fork), QEMU_SECCOMP_SET_SPAWN, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(vfork), QEMU_SECCOMP_SET_SPAWN, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(execve), QEMU_SECCOMP_SET_SPAWN, + 0, NULL, SCMP_ACT_TRAP }, + { SCMP_SYS(clone), QEMU_SECCOMP_SET_SPAWN, + ARRAY_SIZE(clone_arg_none), clone_arg_none, SCMP_ACT_TRAP }, + RULE_CLONE_FLAG(CLONE_VM), + RULE_CLONE_FLAG(CLONE_FS), + RULE_CLONE_FLAG(CLONE_FILES), + RULE_CLONE_FLAG(CLONE_SIGHAND), + RULE_CLONE_FLAG(CLONE_THREAD), + RULE_CLONE_FLAG(CLONE_SYSVSEM), + RULE_CLONE_FLAG(CLONE_SETTLS), + RULE_CLONE_FLAG(CLONE_PARENT_SETTID), + RULE_CLONE_FLAG(CLONE_CHILD_CLEARTID), + /*RULE_CLONE_FLAG(CLONE_DETACHED),*/ + RULE_CLONE_FLAG(CLONE_PIDFD), + RULE_CLONE_FLAG(CLONE_PTRACE), + RULE_CLONE_FLAG(CLONE_VFORK), + RULE_CLONE_FLAG(CLONE_PARENT), + RULE_CLONE_FLAG(CLONE_NEWNS), + RULE_CLONE_FLAG(CLONE_UNTRACED), + RULE_CLONE_FLAG(CLONE_NEWCGROUP), + RULE_CLONE_FLAG(CLONE_NEWUTS), + RULE_CLONE_FLAG(CLONE_NEWIPC), + RULE_CLONE_FLAG(CLONE_NEWUSER), + RULE_CLONE_FLAG(CLONE_NEWPID), + RULE_CLONE_FLAG(CLONE_NEWNET), + RULE_CLONE_FLAG(CLONE_IO), +#ifdef __SNR_clone3 + { SCMP_SYS(clone3), QEMU_SECCOMP_SET_SPAWN, + 0, NULL, SCMP_ACT_ERRNO(ENOSYS) }, +#endif +#ifdef __SNR_execveat + { SCMP_SYS(execveat), QEMU_SECCOMP_SET_SPAWN }, +#endif + { SCMP_SYS(setns), QEMU_SECCOMP_SET_SPAWN }, + { SCMP_SYS(unshare), QEMU_SECCOMP_SET_SPAWN }, + /* resource control */ + { SCMP_SYS(setpriority), QEMU_SECCOMP_SET_RESOURCECTL, + 0, NULL, SCMP_ACT_ERRNO(EPERM) }, + { SCMP_SYS(sched_setparam), QEMU_SECCOMP_SET_RESOURCECTL, + 0, NULL, SCMP_ACT_ERRNO(EPERM) }, + { SCMP_SYS(sched_setscheduler), QEMU_SECCOMP_SET_RESOURCECTL, + ARRAY_SIZE(sched_setscheduler_arg), sched_setscheduler_arg, + SCMP_ACT_ERRNO(EPERM) }, + { SCMP_SYS(sched_setaffinity), QEMU_SECCOMP_SET_RESOURCECTL, + 0, NULL, SCMP_ACT_ERRNO(EPERM) }, +}; + +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_update_action(uint32_t action) +{ +#if defined(SECCOMP_GET_ACTION_AVAIL) && defined(SCMP_ACT_KILL_PROCESS) && \ + defined(SECCOMP_RET_KILL_PROCESS) + if (action == SCMP_ACT_TRAP) { + static int kill_process = -1; + if (kill_process == -1) { + uint32_t testaction = SECCOMP_RET_KILL_PROCESS; + + if (qemu_seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &testaction) == 0) { + kill_process = 1; + } else { + kill_process = 0; + } + } + if (kill_process == 1) { + return SCMP_ACT_KILL_PROCESS; + } + } +#endif + return action; +} + + +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; + } + +#if defined(CONFIG_SECCOMP_SYSRAWRC) + /* + * This must be the first seccomp_attr_set() call to have full + * error propagation from subsequent seccomp APIs. + */ + rc = seccomp_attr_set(ctx, SCMP_FLTATR_API_SYSRAWRC, 1); + if (rc != 0) { + error_setg_errno(errp, -rc, + "failed to set seccomp rawrc attribute"); + goto seccomp_return; + } +#endif + + 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_update_action(denylist[i].action); + 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); |