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authorDaniel P. Berrangé2021-07-29 14:15:43 +0200
committerDaniel P. Berrangé2022-02-16 19:52:40 +0100
commitd2ea8dac705fe9bca9b6b26a7aeb063d1a406f7a (patch)
tree41563216a16a629fe69ba4bc891e385828cb272c
parentseccomp: allow action to be customized per syscall (diff)
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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>
-rw-r--r--MAINTAINERS1
-rw-r--r--tests/unit/meson.build4
-rw-r--r--tests/unit/test-seccomp.c270
3 files changed, 275 insertions, 0 deletions
diff --git a/MAINTAINERS b/MAINTAINERS
index 4b3ae2ab08..1fe647eb08 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2982,6 +2982,7 @@ M: Eduardo Otubo <otubo@redhat.com>
S: Supported
F: softmmu/qemu-seccomp.c
F: include/sysemu/seccomp.h
+F: tests/unit/test-seccomp.c
Cryptography
M: Daniel P. Berrange <berrange@redhat.com>
diff --git a/tests/unit/meson.build b/tests/unit/meson.build
index 64a5e7bfde..cd06f0eaf5 100644
--- a/tests/unit/meson.build
+++ b/tests/unit/meson.build
@@ -53,6 +53,10 @@ if have_system or have_tools
tests += {
'test-qmp-event': [testqapi],
}
+
+ if seccomp.found()
+ tests += {'test-seccomp': ['../../softmmu/qemu-seccomp.c', seccomp]}
+ endif
endif
if have_block
diff --git a/tests/unit/test-seccomp.c b/tests/unit/test-seccomp.c
new file mode 100644
index 0000000000..10ab3e8fe5
--- /dev/null
+++ b/tests/unit/test-seccomp.c
@@ -0,0 +1,270 @@
+/*
+ * QEMU seccomp test suite
+ *
+ * Copyright (c) 2021 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/config-file.h"
+#include "qemu/option.h"
+#include "sysemu/seccomp.h"
+#include "qapi/error.h"
+#include "qemu/module.h"
+
+#include <unistd.h>
+#include <sys/syscall.h>
+
+static void test_seccomp_helper(const char *args, bool killed,
+ int errnum, int (*doit)(void))
+{
+ if (g_test_subprocess()) {
+ QemuOptsList *olist;
+ QemuOpts *opts;
+ int ret;
+
+ module_call_init(MODULE_INIT_OPTS);
+ olist = qemu_find_opts("sandbox");
+ g_assert(olist != NULL);
+
+ opts = qemu_opts_parse_noisily(olist, args, true);
+ g_assert(opts != NULL);
+
+ parse_sandbox(NULL, opts, &error_abort);
+
+ /* Running in a child process */
+ ret = doit();
+
+ if (errnum != 0) {
+ g_assert(ret != 0);
+ g_assert(errno == errnum);
+ } else {
+ g_assert(ret == 0);
+ }
+
+ _exit(0);
+ } else {
+ /* Running in main test process, spawning the child */
+ g_test_trap_subprocess(NULL, 0, 0);
+ if (killed) {
+ g_test_trap_assert_failed();
+ } else {
+ g_test_trap_assert_passed();
+ }
+ }
+}
+
+
+static void test_seccomp_killed(const char *args, int (*doit)(void))
+{
+ test_seccomp_helper(args, true, 0, doit);
+}
+
+static void test_seccomp_errno(const char *args, int errnum, int (*doit)(void))
+{
+ test_seccomp_helper(args, false, errnum, doit);
+}
+
+static void test_seccomp_passed(const char *args, int (*doit)(void))
+{
+ test_seccomp_helper(args, false, 0, doit);
+}
+
+#ifdef SYS_fork
+static int doit_sys_fork(void)
+{
+ int ret = syscall(SYS_fork);
+ if (ret < 0) {
+ return ret;
+ }
+ if (ret == 0) {
+ _exit(0);
+ }
+ return 0;
+}
+
+static void test_seccomp_sys_fork_on_nospawn(void)
+{
+ test_seccomp_killed("on,spawn=deny", doit_sys_fork);
+}
+
+static void test_seccomp_sys_fork_on(void)
+{
+ test_seccomp_passed("on", doit_sys_fork);
+}
+
+static void test_seccomp_sys_fork_off(void)
+{
+ test_seccomp_passed("off", doit_sys_fork);
+}
+#endif
+
+static int doit_fork(void)
+{
+ int ret = fork();
+ if (ret < 0) {
+ return ret;
+ }
+ if (ret == 0) {
+ _exit(0);
+ }
+ return 0;
+}
+
+static void test_seccomp_fork_on_nospawn(void)
+{
+ /* XXX fixme - should be killed */
+ test_seccomp_passed("on,spawn=deny", doit_fork);
+}
+
+static void test_seccomp_fork_on(void)
+{
+ test_seccomp_passed("on", doit_fork);
+}
+
+static void test_seccomp_fork_off(void)
+{
+ test_seccomp_passed("off", doit_fork);
+}
+
+static void *noop(void *arg)
+{
+ return arg;
+}
+
+static int doit_thread(void)
+{
+ pthread_t th;
+ int ret = pthread_create(&th, NULL, noop, NULL);
+ if (ret != 0) {
+ errno = ret;
+ return -1;
+ } else {
+ pthread_join(th, NULL);
+ return 0;
+ }
+}
+
+static void test_seccomp_thread_on(void)
+{
+ test_seccomp_passed("on", doit_thread);
+}
+
+static void test_seccomp_thread_on_nospawn(void)
+{
+ test_seccomp_passed("on,spawn=deny", doit_thread);
+}
+
+static void test_seccomp_thread_off(void)
+{
+ test_seccomp_passed("off", doit_thread);
+}
+
+static int doit_sched(void)
+{
+ struct sched_param param = { .sched_priority = 0 };
+ return sched_setscheduler(getpid(), SCHED_OTHER, &param);
+}
+
+static void test_seccomp_sched_on_nores(void)
+{
+ test_seccomp_errno("on,resourcecontrol=deny", EPERM, doit_sched);
+}
+
+static void test_seccomp_sched_on(void)
+{
+ test_seccomp_passed("on", doit_sched);
+}
+
+static void test_seccomp_sched_off(void)
+{
+ test_seccomp_passed("off", doit_sched);
+}
+
+static bool can_play_with_seccomp(void)
+{
+ g_autofree char *status = NULL;
+ g_auto(GStrv) lines = NULL;
+ size_t i;
+
+ if (!g_file_get_contents("/proc/self/status", &status, NULL, NULL)) {
+ return false;
+ }
+
+ lines = g_strsplit(status, "\n", 0);
+
+ for (i = 0; lines[i] != NULL; i++) {
+ if (g_str_has_prefix(lines[i], "Seccomp:")) {
+ /*
+ * "Seccomp: 1" or "Seccomp: 2" indicate we're already
+ * confined, probably as we're inside a container. In
+ * this case our tests might get unexpected results,
+ * so we can't run reliably
+ */
+ if (!strchr(lines[i], '0')) {
+ return false;
+ }
+
+ return true;
+ }
+ }
+
+ /* Doesn't look like seccomp is enabled in the kernel */
+ return false;
+}
+
+int main(int argc, char **argv)
+{
+ g_test_init(&argc, &argv, NULL);
+ if (can_play_with_seccomp()) {
+#ifdef SYS_fork
+ g_test_add_func("/softmmu/seccomp/sys-fork/on",
+ test_seccomp_sys_fork_on);
+ g_test_add_func("/softmmu/seccomp/sys-fork/on-nospawn",
+ test_seccomp_sys_fork_on_nospawn);
+ g_test_add_func("/softmmu/seccomp/sys-fork/off",
+ test_seccomp_sys_fork_off);
+#endif
+
+ g_test_add_func("/softmmu/seccomp/fork/on",
+ test_seccomp_fork_on);
+ g_test_add_func("/softmmu/seccomp/fork/on-nospawn",
+ test_seccomp_fork_on_nospawn);
+ g_test_add_func("/softmmu/seccomp/fork/off",
+ test_seccomp_fork_off);
+
+ g_test_add_func("/softmmu/seccomp/thread/on",
+ test_seccomp_thread_on);
+ g_test_add_func("/softmmu/seccomp/thread/on-nospawn",
+ test_seccomp_thread_on_nospawn);
+ g_test_add_func("/softmmu/seccomp/thread/off",
+ test_seccomp_thread_off);
+
+ if (doit_sched() == 0) {
+ /*
+ * musl doesn't impl sched_setscheduler, hence
+ * we check above if it works first
+ */
+ g_test_add_func("/softmmu/seccomp/sched/on",
+ test_seccomp_sched_on);
+ g_test_add_func("/softmmu/seccomp/sched/on-nores",
+ test_seccomp_sched_on_nores);
+ g_test_add_func("/softmmu/seccomp/sched/off",
+ test_seccomp_sched_off);
+ }
+ }
+ return g_test_run();
+}