[RFC PATCH 4/5] landlock/selftests: test LANDLOCK_ACCESS_FS_CONNECT_UNIX

["Günther Noack" <gnoack3000@gmail.com>]

* Exercise the LANDLOCK_ACCESS_FS_CONNECT_UNIX access right.
* Extract common helpers from an existing IOCTL test that
  also uses pathname unix(7) sockets.

Cc: Justin Suess <utilityemal77@gmail.com>
Cc: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
---
 tools/testing/selftests/landlock/fs_test.c | 88 +++++++++++++++++-----
 1 file changed, 71 insertions(+), 17 deletions(-)

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 74e975c5e9847..fb5b240bab629 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -4358,30 +4358,58 @@ TEST_F_FORK(layout1, named_pipe_ioctl)
 	ASSERT_EQ(child_pid, waitpid(child_pid, NULL, 0));
 }
 
+/*
+ * set_up_named_unix_server - Create a pathname unix socket and listen
+ *
+ * Return: The listening FD - it is the caller responsibility to close it.
+ */
+static int set_up_named_unix_server(struct __test_metadata *const _metadata,
+				    const char *const path)
+{
+	int fd;
+	struct sockaddr_un addr = {
+		.sun_family = AF_UNIX,
+	};
+
+	ASSERT_EQ(0, unlink(path));
+	fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_LE(0, fd);
+
+	strncpy(addr.sun_path, path, sizeof(addr.sun_path));
+	ASSERT_EQ(0, bind(fd, (struct sockaddr *)&addr, sizeof(addr)));
+
+	ASSERT_EQ(0, listen(fd, 10 /* qlen */));
+	return fd;
+}
+
+/*
+ * test_connect_named_unix - connect to the given named UNIX socket
+ *
+ * Return: The errno from connect(), or 0
+ */
+static int test_connect_named_unix(int fd, const char *const path)
+{
+	struct sockaddr_un addr = {
+		.sun_family = AF_UNIX,
+	};
+	strncpy(addr.sun_path, path, sizeof(addr.sun_path));
+
+	if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) == -1)
+		return errno;
+	return 0;
+}
+
 /* For named UNIX domain sockets, no IOCTL restrictions apply. */
 TEST_F_FORK(layout1, named_unix_domain_socket_ioctl)
 {
 	const char *const path = file1_s1d1;
 	int srv_fd, cli_fd, ruleset_fd;
-	struct sockaddr_un srv_un = {
-		.sun_family = AF_UNIX,
-	};
-	struct sockaddr_un cli_un = {
-		.sun_family = AF_UNIX,
-	};
 	const struct landlock_ruleset_attr attr = {
 		.handled_access_fs = LANDLOCK_ACCESS_FS_IOCTL_DEV,
 	};
 
 	/* Sets up a server */
-	ASSERT_EQ(0, unlink(path));
-	srv_fd = socket(AF_UNIX, SOCK_STREAM, 0);
-	ASSERT_LE(0, srv_fd);
-
-	strncpy(srv_un.sun_path, path, sizeof(srv_un.sun_path));
-	ASSERT_EQ(0, bind(srv_fd, (struct sockaddr *)&srv_un, sizeof(srv_un)));
-
-	ASSERT_EQ(0, listen(srv_fd, 10 /* qlen */));
+	srv_fd = set_up_named_unix_server(_metadata, path);
 
 	/* Enables Landlock. */
 	ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0);
@@ -4393,9 +4421,7 @@ TEST_F_FORK(layout1, named_unix_domain_socket_ioctl)
 	cli_fd = socket(AF_UNIX, SOCK_STREAM, 0);
 	ASSERT_LE(0, cli_fd);
 
-	strncpy(cli_un.sun_path, path, sizeof(cli_un.sun_path));
-	ASSERT_EQ(0,
-		  connect(cli_fd, (struct sockaddr *)&cli_un, sizeof(cli_un)));
+	ASSERT_EQ(0, test_connect_named_unix(cli_fd, path));
 
 	/* FIONREAD and other IOCTLs should not be forbidden. */
 	EXPECT_EQ(0, test_fionread_ioctl(cli_fd));
@@ -4570,6 +4596,34 @@ TEST_F_FORK(ioctl, handle_file_access_file)
 	ASSERT_EQ(0, close(file_fd));
 }
 
+TEST_F_FORK(layout1, named_unix_domain_socket)
+{
+	const char *const path = file1_s1d1;
+	int cli_fd, srv_fd, ruleset_fd;
+	const struct landlock_ruleset_attr attr = {
+		.handled_access_fs = LANDLOCK_ACCESS_FS_CONNECT_UNIX,
+	};
+
+	/* Sets up a server */
+	srv_fd = set_up_named_unix_server(_metadata, path);
+
+	/* Enables Landlock. */
+	ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/* Sets up a client connection to it */
+	cli_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_LE(0, cli_fd);
+
+	/* Connecting to the Unix socket is denied. */
+	EXPECT_EQ(EACCES, test_connect_named_unix(cli_fd, path));
+
+	ASSERT_EQ(0, close(cli_fd));
+	ASSERT_EQ(0, close(srv_fd));
+}
+
 /* clang-format off */
 FIXTURE(layout1_bind) {};
 /* clang-format on */
-- 
2.52.0