Re: [PATCH v3 3/6] selftest/Landlock: Signal restriction tests

This patch expands Landlock ABI version 6 by providing tests for
signal scoping mechanism. Base on kill(2), if the signal is 0,
no signal will be sent, but the permission of a process to send
a signal will be checked. Likewise, this test consider one signal
for each signal category.

Signed-off-by: Tahera Fahimi <redacted>
---
Chnages in versions:
V2:
* Moving tests from ptrace_test.c to scoped_signal_test.c
* Remove debugging statements.
* Covering all basic restriction scenarios by sending 0 as signal
V1:
* Expanding Landlock ABI version 6 by providing basic tests for
  four signals to test signal scoping mechanism.
---
 .../selftests/landlock/scoped_signal_test.c   | 302 ++++++++++++++++++
 1 file changed, 302 insertions(+)
 create mode 100644 tools/testing/selftests/landlock/scoped_signal_test.c

diff --git a/tools/testing/selftests/landlock/scoped_signal_test.c b/tools/testing/selftests/landlock/scoped_signal_test.c
new file mode 100644
index 000000000000..92958c6266ca
--- /dev/null
+++ b/tools/testing/selftests/landlock/scoped_signal_test.c

@@ -0,0 +1,302 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Landlock tests - Signal Scoping
+ *
+ * Copyright © 2017-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2019-2020 ANSSI
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/landlock.h>
+#include <signal.h>
+#include <sys/prctl.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "common.h"
+
+static sig_atomic_t signaled;

+
+static void create_signal_domain(struct __test_metadata *const _metadata)
+{
+	int ruleset_fd;
+	const struct landlock_ruleset_attr ruleset_attr = {
+		.scoped = LANDLOCK_SCOPED_SIGNAL,
+	};
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	EXPECT_LE(0, ruleset_fd)
+	{
+		TH_LOG("Failed to create a ruleset: %s", strerror(errno));
+	}
+	enforce_ruleset(_metadata, ruleset_fd);
+	EXPECT_EQ(0, close(ruleset_fd));
+}
+
+static void scope_signal_handler(int sig, siginfo_t *info, void *ucontext)
+{
+	if (sig == SIGHUP || sig == SIGURG || sig == SIGTSTP ||
+	    sig == SIGTRAP || sig == SIGUSR1) {
+		signaled = 1;
+	}
+}
+
+/* clang-format off */
+FIXTURE(signal_scoping) {};
+/* clang-format on */
+
+FIXTURE_VARIANT(signal_scoping)
+{
+	const int sig;
+	const bool domain_both;
+	const bool domain_parent;
+	const bool domain_child;
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, allow_without_domain) {
+	/* clang-format on */
+	.sig = 0,
+	.domain_both = false,
+	.domain_parent = false,
+	.domain_child = false,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, deny_with_child_domain) {
+	/* clang-format on */
+	.sig = 0,
+	.domain_both = false,
+	.domain_parent = false,
+	.domain_child = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, allow_with_parent_domain) {
+	/* clang-format on */
+	.sig = 0,
+	.domain_both = false,
+	.domain_parent = true,
+	.domain_child = false,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, deny_with_sibling_domain) {
+	/* clang-format on */
+	.sig = 0,
+	.domain_both = false,
+	.domain_parent = true,
+	.domain_child = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, allow_sibling_domain) {
+	/* clang-format on */
+	.sig = 0,
+	.domain_both = true,
+	.domain_parent = false,
+	.domain_child = false,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, deny_with_nested_domain) {
+	/* clang-format on */
+	.sig = 0,
+	.domain_both = true,
+	.domain_parent = false,
+	.domain_child = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, allow_with_nested_and_parent_domain) {
+	/* clang-format on */
+	.sig = 0,
+	.domain_both = true,
+	.domain_parent = true,
+	.domain_child = false,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, deny_with_forked_domain) {
+	/* clang-format on */
+	.sig = 0,
+	.domain_both = true,
+	.domain_parent = true,
+	.domain_child = true,
+};
+
+/* Default Action: Terminate*/
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, deny_with_forked_domain_SIGHUP) {
+	/* clang-format on */
+	.sig = SIGHUP,
+	.domain_both = true,
+	.domain_parent = true,
+	.domain_child = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, allow_with_forked_domain_SIGHUP) {
+	/* clang-format on */
+	.sig = SIGHUP,
+	.domain_both = false,
+	.domain_parent = true,
+	.domain_child = false,
+};
+
+/* Default Action: Ignore*/
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, deny_with_forked_domain_SIGURG) {
+	/* clang-format on */
+	.sig = SIGURG,
+	.domain_both = true,
+	.domain_parent = true,
+	.domain_child = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, allow_with_forked_domain_SIGURG) {
+	/* clang-format on */
+	.sig = SIGURG,
+	.domain_both = false,
+	.domain_parent = true,
+	.domain_child = false,
+};
+
+/* Default Action: Stop*/
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, deny_with_forked_domain_SIGTSTP) {
+	/* clang-format on */
+	.sig = SIGTSTP,
+	.domain_both = true,
+	.domain_parent = true,
+	.domain_child = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, allow_with_forked_domain_SIGTSTP) {
+	/* clang-format on */
+	.sig = SIGTSTP,
+	.domain_both = false,
+	.domain_parent = true,
+	.domain_child = false,
+};
+
+/* Default Action: Coredump*/
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, deny_with_forked_domain_SIGTRAP) {
+	/* clang-format on */
+	.sig = SIGTRAP,
+	.domain_both = true,
+	.domain_parent = true,
+	.domain_child = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, allow_with_forked_domain_SIGTRAP) {
+	/* clang-format on */
+	.sig = SIGTRAP,
+	.domain_both = false,
+	.domain_parent = true,
+	.domain_child = false,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(signal_scoping, deny_with_forked_domain_SIGUSR1) {
+	/* clang-format on */
+	.sig = SIGUSR1,
+	.domain_both = true,
+	.domain_parent = true,
+	.domain_child = true,
+};
+
+FIXTURE_SETUP(signal_scoping)
+{
+}
+
+FIXTURE_TEARDOWN(signal_scoping)
+{
+}
+
+TEST_F(signal_scoping, test_signal)

+{
+	pid_t child;
+	pid_t parent = getpid();
+	int status;
+	bool can_signal;
+	int pipe_parent[2];
+	struct sigaction action = {
+		.sa_sigaction = scope_signal_handler,
+		.sa_flags = SA_SIGINFO,
+
+	};
+
+	can_signal = !variant->domain_child;
+
+	if (variant->sig > 0)
+		ASSERT_LE(0, sigaction(variant->sig, &action, NULL));
+
+	if (variant->domain_both) {
+		create_signal_domain(_metadata);
+		if (!__test_passed(_metadata))
+			/* Aborts before forking. */
+			return;
+	}
+	ASSERT_EQ(0, pipe2(pipe_parent, O_CLOEXEC));
+
+	child = fork();
+	ASSERT_LE(0, child);
+	if (child == 0) {
+		char buf_child;
+		int err;
+
+		ASSERT_EQ(0, close(pipe_parent[1]));
+		if (variant->domain_child)
+			create_signal_domain(_metadata);
+
+		/* Waits for the parent to be in a domain, if any. */
+		ASSERT_EQ(1, read(pipe_parent[0], &buf_child, 1));

+
+		err = kill(parent, variant->sig);
+		if (can_signal) {
+			ASSERT_EQ(0, err);
+		} else {
+			ASSERT_EQ(-1, err);
+			ASSERT_EQ(EPERM, errno);
+		}
+		/* no matter of the domain, a process should be able to send
+		 * a signal to itself.
+		 */
+		ASSERT_EQ(0, raise(variant->sig));
+		if (variant->sig > 0)
+			ASSERT_EQ(1, signaled);
+		_exit(_metadata->exit_code);
+		return;
+	}
+	ASSERT_EQ(0, close(pipe_parent[0]));
+	if (variant->domain_parent)
+		create_signal_domain(_metadata);
+

+	/* Signals that the parent is in a domain, if any. */
+	ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
+
+	if (can_signal && variant->sig > 0) {
+		ASSERT_EQ(-1, pause());
+		ASSERT_EQ(EINTR, errno);