selftests/landlock: Add audit tests for network

Test all network blockers:
- net.bind_tcp
- net.connect_tcp

Test coverage for security/landlock is 94.0% of 1525 lines according to
gcc/gcov-14.

Cc: Günther Noack <gnoack@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-28-mic@digikod.net
[mic: Update test coverage]
Signed-off-by: Mickaël Salaün <mic@digikod.net>

Author: l0kod

tools/testing/selftests/landlock/net_test.c

@@ -20,6 +20,7 @@
 #include <sys/syscall.h>
 #include <sys/un.h>
 
+#include "audit.h"
 #include "common.h"
 
 const short sock_port_start = (1 << 10);
@@ -1868,4 +1869,135 @@ TEST_F(port_specific, bind_connect_1023)
 	EXPECT_EQ(0, close(bind_fd));
 }
 
+static int matches_log_tcp(const int audit_fd, const char *const blockers,
+			   const char *const dir_addr, const char *const addr,
+			   const char *const dir_port)
+{
+	static const char log_template[] = REGEX_LANDLOCK_PREFIX
+		" blockers=%s %s=%s %s=1024$";
+	/*
+	 * Max strlen(blockers): 16
+	 * Max strlen(dir_addr): 5
+	 * Max strlen(addr): 12
+	 * Max strlen(dir_port): 4
+	 */
+	char log_match[sizeof(log_template) + 37];
+	int log_match_len;
+
+	log_match_len = snprintf(log_match, sizeof(log_match), log_template,
+				 blockers, dir_addr, addr, dir_port);
+	if (log_match_len > sizeof(log_match))
+		return -E2BIG;
+
+	return audit_match_record(audit_fd, AUDIT_LANDLOCK_ACCESS, log_match,
+				  NULL);
+}
+
+FIXTURE(audit)
+{
+	struct service_fixture srv0;
+	struct audit_filter audit_filter;
+	int audit_fd;
+};
+
+FIXTURE_VARIANT(audit)
+{
+	const char *const addr;
+	const struct protocol_variant prot;
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(audit, ipv4) {
+	/* clang-format on */
+	.addr = "127\\.0\\.0\\.1",
+	.prot = {
+		.domain = AF_INET,
+		.type = SOCK_STREAM,
+	},
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(audit, ipv6) {
+	/* clang-format on */
+	.addr = "::1",
+	.prot = {
+		.domain = AF_INET6,
+		.type = SOCK_STREAM,
+	},
+};
+
+FIXTURE_SETUP(audit)
+{
+	ASSERT_EQ(0, set_service(&self->srv0, variant->prot, 0));
+	setup_loopback(_metadata);
+
+	set_cap(_metadata, CAP_AUDIT_CONTROL);
+	self->audit_fd = audit_init_with_exe_filter(&self->audit_filter);
+	EXPECT_LE(0, self->audit_fd);
+	disable_caps(_metadata);
+};
+
+FIXTURE_TEARDOWN(audit)
+{
+	set_cap(_metadata, CAP_AUDIT_CONTROL);
+	EXPECT_EQ(0, audit_cleanup(self->audit_fd, &self->audit_filter));
+	clear_cap(_metadata, CAP_AUDIT_CONTROL);
+}
+
+TEST_F(audit, bind)
+{
+	const struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
+				      LANDLOCK_ACCESS_NET_CONNECT_TCP,
+	};
+	struct audit_records records;
+	int ruleset_fd, sock_fd;
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	EXPECT_EQ(0, close(ruleset_fd));
+
+	sock_fd = socket_variant(&self->srv0);
+	ASSERT_LE(0, sock_fd);
+	EXPECT_EQ(-EACCES, bind_variant(sock_fd, &self->srv0));
+	EXPECT_EQ(0, matches_log_tcp(self->audit_fd, "net\\.bind_tcp", "saddr",
+				     variant->addr, "src"));
+
+	EXPECT_EQ(0, audit_count_records(self->audit_fd, &records));
+	EXPECT_EQ(0, records.access);
+	EXPECT_EQ(1, records.domain);
+
+	EXPECT_EQ(0, close(sock_fd));
+}
+
+TEST_F(audit, connect)
+{
+	const struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
+				      LANDLOCK_ACCESS_NET_CONNECT_TCP,
+	};
+	struct audit_records records;
+	int ruleset_fd, sock_fd;
+
+	ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	EXPECT_EQ(0, close(ruleset_fd));
+
+	sock_fd = socket_variant(&self->srv0);
+	ASSERT_LE(0, sock_fd);
+	EXPECT_EQ(-EACCES, connect_variant(sock_fd, &self->srv0));
+	EXPECT_EQ(0, matches_log_tcp(self->audit_fd, "net\\.connect_tcp",
+				     "daddr", variant->addr, "dest"));
+
+	EXPECT_EQ(0, audit_count_records(self->audit_fd, &records));
+	EXPECT_EQ(0, records.access);
+	EXPECT_EQ(1, records.domain);
+
+	EXPECT_EQ(0, close(sock_fd));
+}
+
 TEST_HARNESS_MAIN