From d2ea8dac705fe9bca9b6b26a7aeb063d1a406f7a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Date: Thu, 29 Jul 2021 13:15:43 +0100 Subject: [PATCH] seccomp: add unit test for seccomp filtering MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Daniel P. BerrangĂ© --- MAINTAINERS | 1 + tests/unit/meson.build | 4 + tests/unit/test-seccomp.c | 270 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 275 insertions(+) create mode 100644 tests/unit/test-seccomp.c diff --git a/MAINTAINERS b/MAINTAINERS index 4b3ae2ab08..1fe647eb08 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2982,6 +2982,7 @@ M: Eduardo Otubo S: Supported F: softmmu/qemu-seccomp.c F: include/sysemu/seccomp.h +F: tests/unit/test-seccomp.c Cryptography M: Daniel P. Berrange 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 . + * + */ + +#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 +#include + +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, ¶m); +} + +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(); +}