Subject: Re: [RFC PATCH v2 6/9] selftests/landlock: Test listening without explicit bind restriction

From: "Günther Noack" <[email-masked]>
Date: Tue, 20 Aug 2024 15:02:32 +0200

On Wed, Aug 14, 2024 at 11:01:48AM +0800, Mikhail Ivanov wrote:
> Test scenarios where listen(2) call without explicit bind(2) is allowed
> and forbidden.
> 
> Signed-off-by: Mikhail Ivanov <[email-masked]>
> ---
>  tools/testing/selftests/landlock/net_test.c | 83 +++++++++++++++++++++
>  1 file changed, 83 insertions(+)
> 
> diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c
> index 551891b18b7a..92c042349596 100644
> --- a/tools/testing/selftests/landlock/net_test.c
> +++ b/tools/testing/selftests/landlock/net_test.c
> @@ -1851,6 +1851,89 @@ TEST_F(port_specific, bind_connect_zero)
>  	EXPECT_EQ(0, close(bind_fd));
>  }
>  
> +TEST_F(port_specific, listen_without_bind_allowed)
> +{
> +	if (variant->sandbox == TCP_SANDBOX) {
> +		const struct landlock_ruleset_attr ruleset_attr = {
> +			.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
> +					      LANDLOCK_ACCESS_NET_LISTEN_TCP
> +		};
> +		const struct landlock_net_port_attr tcp_listen_zero = {
> +			.allowed_access = LANDLOCK_ACCESS_NET_LISTEN_TCP,
> +			.port = 0,
> +		};
> +		int ruleset_fd;
> +
> +		ruleset_fd = landlock_create_ruleset(&ruleset_attr,
> +						     sizeof(ruleset_attr), 0);
> +		ASSERT_LE(0, ruleset_fd);
> +
> +		/*
> +		 * Allow listening without explicit bind
> +		 * (cf. landlock_net_port_attr).
> +		 */
> +		EXPECT_EQ(0,
> +			  landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
> +					    &tcp_listen_zero, 0));
> +
> +		enforce_ruleset(_metadata, ruleset_fd);
> +		EXPECT_EQ(0, close(ruleset_fd));
> +	}
> +	int listen_fd, connect_fd;
> +	__u64 port;
> +
> +	listen_fd = socket_variant(&self->srv0);
> +	ASSERT_LE(0, listen_fd);
> +
> +	connect_fd = socket_variant(&self->srv0);
> +	ASSERT_LE(0, connect_fd);
> +	/*
> +	 * Allow listen(2) to select a random port for the socket,
> +	 * since bind(2) wasn't called.
> +	 */
> +	EXPECT_EQ(0, listen_variant(listen_fd, backlog));
> +
> +	/* Connects on the binded port. */
> +	port = get_binded_port(listen_fd, &variant->prot);

Please rename "binded" to "bound" when you come across it.

> +	EXPECT_NE(0, port);
> +	set_port(&self->srv0, port);
> +	EXPECT_EQ(0, connect_variant(connect_fd, &self->srv0));
> +
> +	EXPECT_EQ(0, close(connect_fd));
> +	EXPECT_EQ(0, close(listen_fd));
> +}
> +
> +TEST_F(port_specific, listen_without_bind_denied)
> +{
> +	if (variant->sandbox == TCP_SANDBOX) {
> +		const struct landlock_ruleset_attr ruleset_attr = {
> +			.handled_access_net = LANDLOCK_ACCESS_NET_LISTEN_TCP
> +		};
> +		int ruleset_fd;
> +
> +		ruleset_fd = landlock_create_ruleset(&ruleset_attr,
> +						     sizeof(ruleset_attr), 0);
> +		ASSERT_LE(0, ruleset_fd);
> +
> +		/* Deny listening. */
> +		enforce_ruleset(_metadata, ruleset_fd);
> +		EXPECT_EQ(0, close(ruleset_fd));
> +	}
> +	int listen_fd, ret;
> +
> +	listen_fd = socket_variant(&self->srv0);
> +	ASSERT_LE(0, listen_fd);
> +
> +	/* Checks that listening without explicit binding is prohibited. */
> +	ret = listen_variant(listen_fd, backlog);
> +	if (is_restricted(&variant->prot, variant->sandbox)) {
> +		/* Denied by Landlock. */
> +		EXPECT_EQ(-EACCES, ret);
> +	} else {
> +		EXPECT_EQ(0, ret);
> +	}
> +}
> +
>  TEST_F(port_specific, port_1023)
>  {
>  	int bind_fd, connect_fd, ret;
> -- 
> 2.34.1
>