seccomp: add unit test for seccomp filtering
The handling of some syscalls / libc function is quite subtle. For example, 'fork' at a libc level doesn't always correspond to 'fork' at a syscall level, since the 'clone' syscall is preferred usually. The unit test will help to detect these kind of problems. A point of difficulty in writing a test though is that the QEMU build process may already be confined by seccomp. For example, if running inside a container. Since we can't predict what filtering might have been applied already, we are quite conservative and skip all tests if we see any kind of seccomp filter active. Acked-by: Eduardo Otubo <otubo@redhat.com> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrangé
parent
8f46f56260
commit
d2ea8dac70
@ -2982,6 +2982,7 @@ M: Eduardo Otubo <otubo@redhat.com>
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S: Supported
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F: softmmu/qemu-seccomp.c
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F: include/sysemu/seccomp.h
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F: tests/unit/test-seccomp.c
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Cryptography
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M: Daniel P. Berrange <berrange@redhat.com>
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@ -53,6 +53,10 @@ if have_system or have_tools
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tests += {
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'test-qmp-event': [testqapi],
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}
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if seccomp.found()
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tests += {'test-seccomp': ['../../softmmu/qemu-seccomp.c', seccomp]}
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endif
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endif
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if have_block
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270
tests/unit/test-seccomp.c
Normal file
270
tests/unit/test-seccomp.c
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@ -0,0 +1,270 @@
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/*
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* QEMU seccomp test suite
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*
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* Copyright (c) 2021 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but 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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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include "qemu/osdep.h"
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#include "qemu/config-file.h"
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#include "qemu/option.h"
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#include "sysemu/seccomp.h"
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#include "qapi/error.h"
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#include "qemu/module.h"
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#include <unistd.h>
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#include <sys/syscall.h>
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static void test_seccomp_helper(const char *args, bool killed,
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int errnum, int (*doit)(void))
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{
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if (g_test_subprocess()) {
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QemuOptsList *olist;
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QemuOpts *opts;
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int ret;
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module_call_init(MODULE_INIT_OPTS);
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olist = qemu_find_opts("sandbox");
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g_assert(olist != NULL);
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opts = qemu_opts_parse_noisily(olist, args, true);
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g_assert(opts != NULL);
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parse_sandbox(NULL, opts, &error_abort);
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/* Running in a child process */
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ret = doit();
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if (errnum != 0) {
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g_assert(ret != 0);
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g_assert(errno == errnum);
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} else {
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g_assert(ret == 0);
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}
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_exit(0);
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} else {
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/* Running in main test process, spawning the child */
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g_test_trap_subprocess(NULL, 0, 0);
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if (killed) {
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g_test_trap_assert_failed();
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} else {
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g_test_trap_assert_passed();
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}
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}
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}
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static void test_seccomp_killed(const char *args, int (*doit)(void))
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{
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test_seccomp_helper(args, true, 0, doit);
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}
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static void test_seccomp_errno(const char *args, int errnum, int (*doit)(void))
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{
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test_seccomp_helper(args, false, errnum, doit);
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}
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static void test_seccomp_passed(const char *args, int (*doit)(void))
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{
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test_seccomp_helper(args, false, 0, doit);
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}
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#ifdef SYS_fork
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static int doit_sys_fork(void)
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{
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int ret = syscall(SYS_fork);
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if (ret < 0) {
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return ret;
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}
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if (ret == 0) {
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_exit(0);
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}
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return 0;
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}
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static void test_seccomp_sys_fork_on_nospawn(void)
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{
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test_seccomp_killed("on,spawn=deny", doit_sys_fork);
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}
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static void test_seccomp_sys_fork_on(void)
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{
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test_seccomp_passed("on", doit_sys_fork);
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}
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static void test_seccomp_sys_fork_off(void)
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{
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test_seccomp_passed("off", doit_sys_fork);
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}
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#endif
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static int doit_fork(void)
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{
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int ret = fork();
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if (ret < 0) {
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return ret;
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}
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if (ret == 0) {
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_exit(0);
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}
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return 0;
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}
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static void test_seccomp_fork_on_nospawn(void)
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{
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/* XXX fixme - should be killed */
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test_seccomp_passed("on,spawn=deny", doit_fork);
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}
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static void test_seccomp_fork_on(void)
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{
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test_seccomp_passed("on", doit_fork);
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}
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static void test_seccomp_fork_off(void)
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{
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test_seccomp_passed("off", doit_fork);
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}
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static void *noop(void *arg)
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{
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return arg;
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}
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static int doit_thread(void)
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{
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pthread_t th;
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int ret = pthread_create(&th, NULL, noop, NULL);
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if (ret != 0) {
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errno = ret;
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return -1;
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} else {
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pthread_join(th, NULL);
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return 0;
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}
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}
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static void test_seccomp_thread_on(void)
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{
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test_seccomp_passed("on", doit_thread);
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}
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static void test_seccomp_thread_on_nospawn(void)
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{
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test_seccomp_passed("on,spawn=deny", doit_thread);
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}
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static void test_seccomp_thread_off(void)
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{
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test_seccomp_passed("off", doit_thread);
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}
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static int doit_sched(void)
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{
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struct sched_param param = { .sched_priority = 0 };
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return sched_setscheduler(getpid(), SCHED_OTHER, ¶m);
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}
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static void test_seccomp_sched_on_nores(void)
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{
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test_seccomp_errno("on,resourcecontrol=deny", EPERM, doit_sched);
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}
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static void test_seccomp_sched_on(void)
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{
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test_seccomp_passed("on", doit_sched);
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}
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static void test_seccomp_sched_off(void)
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{
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test_seccomp_passed("off", doit_sched);
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}
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static bool can_play_with_seccomp(void)
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{
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g_autofree char *status = NULL;
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g_auto(GStrv) lines = NULL;
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size_t i;
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if (!g_file_get_contents("/proc/self/status", &status, NULL, NULL)) {
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return false;
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}
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lines = g_strsplit(status, "\n", 0);
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for (i = 0; lines[i] != NULL; i++) {
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if (g_str_has_prefix(lines[i], "Seccomp:")) {
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/*
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* "Seccomp: 1" or "Seccomp: 2" indicate we're already
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* confined, probably as we're inside a container. In
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* this case our tests might get unexpected results,
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* so we can't run reliably
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*/
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if (!strchr(lines[i], '0')) {
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return false;
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}
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return true;
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}
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}
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/* Doesn't look like seccomp is enabled in the kernel */
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return false;
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}
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int main(int argc, char **argv)
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{
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g_test_init(&argc, &argv, NULL);
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if (can_play_with_seccomp()) {
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#ifdef SYS_fork
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g_test_add_func("/softmmu/seccomp/sys-fork/on",
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test_seccomp_sys_fork_on);
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g_test_add_func("/softmmu/seccomp/sys-fork/on-nospawn",
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test_seccomp_sys_fork_on_nospawn);
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g_test_add_func("/softmmu/seccomp/sys-fork/off",
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test_seccomp_sys_fork_off);
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#endif
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g_test_add_func("/softmmu/seccomp/fork/on",
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test_seccomp_fork_on);
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g_test_add_func("/softmmu/seccomp/fork/on-nospawn",
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test_seccomp_fork_on_nospawn);
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g_test_add_func("/softmmu/seccomp/fork/off",
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test_seccomp_fork_off);
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g_test_add_func("/softmmu/seccomp/thread/on",
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test_seccomp_thread_on);
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g_test_add_func("/softmmu/seccomp/thread/on-nospawn",
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test_seccomp_thread_on_nospawn);
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g_test_add_func("/softmmu/seccomp/thread/off",
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test_seccomp_thread_off);
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if (doit_sched() == 0) {
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/*
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* musl doesn't impl sched_setscheduler, hence
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* we check above if it works first
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*/
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g_test_add_func("/softmmu/seccomp/sched/on",
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test_seccomp_sched_on);
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g_test_add_func("/softmmu/seccomp/sched/on-nores",
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test_seccomp_sched_on_nores);
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g_test_add_func("/softmmu/seccomp/sched/off",
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test_seccomp_sched_off);
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}
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}
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return g_test_run();
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}
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