Re: [PATCH] landlock: Fix and test network AF inconsistencies

["Mickaël Salaün" <mic@digikod.net>]

On Thu, Aug 17, 2023 at 05:13:28PM +0300, Konstantin Meskhidze (A) wrote:
> 
> 
> 8/17/2023 4:00 PM, Mickaël Salaün пишет:
> > Check af_family consistency while handling AF_UNSPEC specifically.
> > 
> > This patch should be squashed into the "Network support for Landlock"
> > v11 patch series.
> 
> Thank you so much.
> Can I find this patch in
> https://git.kernel.org/pub/scm/linux/kernel/git/mic/linux ???

It is now in the landlock-net-v11 branch.

> > 
> > Signed-off-by: Mickaël Salaün <mic@digikod.net>
> > ---
> >   security/landlock/net.c                     |  29 ++++-
> >   tools/testing/selftests/landlock/net_test.c | 124 +++++++++++++-------
> >   2 files changed, 108 insertions(+), 45 deletions(-)
> > 
> > diff --git a/security/landlock/net.c b/security/landlock/net.c
> > index f8d2be53ac0d..ea5373f774f9 100644
> > --- a/security/landlock/net.c
> > +++ b/security/landlock/net.c
> > @@ -80,11 +80,11 @@ static int check_socket_access(struct socket *const sock,
> >   	if (WARN_ON_ONCE(domain->num_layers < 1))
> >   		return -EACCES;
> > -	/* Checks if it's a TCP socket. */
> > +	/* Checks if it's a (potential) TCP socket. */
> >   	if (sock->type != SOCK_STREAM)
> >   		return 0;
> > -	/* Checks for minimal header length. */
> > +	/* Checks for minimal header length to safely read sa_family. */
> >   	if (addrlen < offsetofend(struct sockaddr, sa_family))
> >   		return -EINVAL;
> > @@ -106,7 +106,6 @@ static int check_socket_access(struct socket *const sock,
> >   		return 0;
> >   	}
> > -	/* Specific AF_UNSPEC handling. */
> >   	if (address->sa_family == AF_UNSPEC) {
> >   		/*
> >   		 * Connecting to an address with AF_UNSPEC dissolves the TCP
> > @@ -114,6 +113,10 @@ static int check_socket_access(struct socket *const sock,
> >   		 * connection while retaining the socket object (i.e., the file
> >   		 * descriptor).  As for dropping privileges, closing
> >   		 * connections is always allowed.
> > +		 *
> > +		 * For a TCP access control system, this request is legitimate.
> > +		 * Let the network stack handle potential inconsistencies and
> > +		 * return -EINVAL if needed.
> >   		 */
> >   		if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP)
> >   			return 0;
> > @@ -124,14 +127,34 @@ static int check_socket_access(struct socket *const sock,
> >   		 * INADDR_ANY (cf. __inet_bind).  Checking the address is
> >   		 * required to not wrongfully return -EACCES instead of
> >   		 * -EAFNOSUPPORT.
> > +		 *
> > +		 *  We could return 0 and let the network stack handle these
> > +		 *  checks, but it is safer to return a proper error and test
> > +		 *  consistency thanks to kselftest.
> >   		 */
> >   		if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
> > +			/* addrlen has already been checked for AF_UNSPEC. */
> >   			const struct sockaddr_in *const sockaddr =
> >   				(struct sockaddr_in *)address;
> > +			if (sock->sk->__sk_common.skc_family != AF_INET)
> > +				return -EINVAL;
> > +
> >   			if (sockaddr->sin_addr.s_addr != htonl(INADDR_ANY))
> >   				return -EAFNOSUPPORT;
> >   		}
> > +	} else {
> > +		/*
> > +		 * Checks sa_family consistency to not wrongfully return
> > +		 * -EACCES instead of -EINVAL.  Valid sa_family changes are
> > +		 *  only (from AF_INET or AF_INET6) to AF_UNSPEC.
> > +		 *
> > +		 *  We could return 0 and let the network stack handle this
> > +		 *  check, but it is safer to return a proper error and test
> > +		 *  consistency thanks to kselftest.
> > +		 */
> > +		if (address->sa_family != sock->sk->__sk_common.skc_family)
> > +			return -EINVAL;
> >   	}
> >   	id.key.data = (__force uintptr_t)port;
> > diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c
> > index 12dc127ea7d1..504a26c63fd9 100644
> > --- a/tools/testing/selftests/landlock/net_test.c
> > +++ b/tools/testing/selftests/landlock/net_test.c
> > @@ -233,7 +233,7 @@ static int connect_variant(const int sock_fd,
> >   FIXTURE(protocol)
> >   {
> > -	struct service_fixture srv0, srv1, srv2, unspec_any, unspec_srv0;
> > +	struct service_fixture srv0, srv1, srv2, unspec_any0, unspec_srv0;
> >   };
> >   FIXTURE_VARIANT(protocol)
> > @@ -257,8 +257,8 @@ FIXTURE_SETUP(protocol)
> >   	ASSERT_EQ(0, set_service(&self->unspec_srv0, prot_unspec, 0));
> > -	ASSERT_EQ(0, set_service(&self->unspec_any, prot_unspec, 0));
> > -	self->unspec_any.ipv4_addr.sin_addr.s_addr = htonl(INADDR_ANY);
> > +	ASSERT_EQ(0, set_service(&self->unspec_any0, prot_unspec, 0));
> > +	self->unspec_any0.ipv4_addr.sin_addr.s_addr = htonl(INADDR_ANY);
> >   	setup_loopback(_metadata);
> >   };
> > @@ -615,20 +615,18 @@ TEST_F(protocol, connect)
> >   // Kernel FIXME: tcp_sandbox_with_ipv6_tcp and tcp_sandbox_with_unix_stream
> >   TEST_F(protocol, bind_unspec)
> >   {
> > +	const struct landlock_ruleset_attr ruleset_attr = {
> > +		.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP,
> > +	};
> > +	const struct landlock_net_service_attr tcp_bind = {
> > +		.allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP,
> > +		.port = self->srv0.port,
> > +	};
> >   	int bind_fd, ret;
> >   	if (variant->sandbox == TCP_SANDBOX) {
> > -		const struct landlock_ruleset_attr ruleset_attr = {
> > -			.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP,
> > -		};
> > -		const struct landlock_net_service_attr tcp_bind = {
> > -			.allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP,
> > -			.port = self->srv0.port,
> > -		};
> > -		int ruleset_fd;
> > -
> > -		ruleset_fd = landlock_create_ruleset(&ruleset_attr,
> > -						     sizeof(ruleset_attr), 0);
> > +		const int ruleset_fd = landlock_create_ruleset(
> > +			&ruleset_attr, sizeof(ruleset_attr), 0);
> >   		ASSERT_LE(0, ruleset_fd);
> >   		/* Allows bind. */
> > @@ -642,8 +640,8 @@ TEST_F(protocol, bind_unspec)
> >   	bind_fd = socket_variant(&self->srv0);
> >   	ASSERT_LE(0, bind_fd);
> > -	/* Binds on AF_UNSPEC/INADDR_ANY. */
> > -	ret = bind_variant(bind_fd, &self->unspec_any);
> > +	/* Allowed bind on AF_UNSPEC/INADDR_ANY. */
> > +	ret = bind_variant(bind_fd, &self->unspec_any0);
> >   	if (variant->prot.domain == AF_INET) {
> >   		EXPECT_EQ(0, ret)
> >   		{
> > @@ -655,6 +653,33 @@ TEST_F(protocol, bind_unspec)
> >   	}
> >   	EXPECT_EQ(0, close(bind_fd));
> > +	if (variant->sandbox == TCP_SANDBOX) {
> > +		const int ruleset_fd = landlock_create_ruleset(
> > +			&ruleset_attr, sizeof(ruleset_attr), 0);
> > +		ASSERT_LE(0, ruleset_fd);
> > +
> > +		/* Denies bind. */
> > +		enforce_ruleset(_metadata, ruleset_fd);
> > +		EXPECT_EQ(0, close(ruleset_fd));
> > +	}
> > +
> > +	bind_fd = socket_variant(&self->srv0);
> > +	ASSERT_LE(0, bind_fd);
> > +
> > +	/* Denied bind on AF_UNSPEC/INADDR_ANY. */
> > +	ret = bind_variant(bind_fd, &self->unspec_any0);
> > +	if (variant->prot.domain == AF_INET) {
> > +		if (is_restricted(&variant->prot, variant->sandbox)) {
> > +			EXPECT_EQ(-EACCES, ret);
> > +		} else {
> > +			EXPECT_EQ(0, ret);
> > +		}
> > +	} else {
> > +		EXPECT_EQ(-EINVAL, ret);
> > +	}
> > +	EXPECT_EQ(0, close(bind_fd));
> > +
> > +	/* Checks bind with AF_UNSPEC and the loopback address. */
> >   	bind_fd = socket_variant(&self->srv0);
> >   	ASSERT_LE(0, bind_fd);
> >   	ret = bind_variant(bind_fd, &self->unspec_srv0);
> > @@ -671,34 +696,16 @@ TEST_F(protocol, bind_unspec)
> >   TEST_F(protocol, connect_unspec)
> >   {
> > +	const struct landlock_ruleset_attr ruleset_attr = {
> > +		.handled_access_net = LANDLOCK_ACCESS_NET_CONNECT_TCP,
> > +	};
> > +	const struct landlock_net_service_attr tcp_connect = {
> > +		.allowed_access = LANDLOCK_ACCESS_NET_CONNECT_TCP,
> > +		.port = self->srv0.port,
> > +	};
> >   	int bind_fd, client_fd, status;
> >   	pid_t child;
> > -	if (variant->sandbox == TCP_SANDBOX) {
> > -		const struct landlock_ruleset_attr ruleset_attr = {
> > -			.handled_access_net = LANDLOCK_ACCESS_NET_CONNECT_TCP,
> > -		};
> > -		const struct landlock_net_service_attr tcp_connect = {
> > -			.allowed_access = LANDLOCK_ACCESS_NET_CONNECT_TCP,
> > -			.port = self->srv0.port,
> > -		};
> > -		int ruleset_fd;
> > -
> > -		ruleset_fd = landlock_create_ruleset(&ruleset_attr,
> > -						     sizeof(ruleset_attr), 0);
> > -		ASSERT_LE(0, ruleset_fd);
> > -
> > -		/* Allows connect. */
> > -		ASSERT_EQ(0, landlock_add_rule(ruleset_fd,
> > -					       LANDLOCK_RULE_NET_SERVICE,
> > -					       &tcp_connect, 0));
> > -		enforce_ruleset(_metadata, ruleset_fd);
> > -		EXPECT_EQ(0, close(ruleset_fd));
> > -	}
> > -
> > -	/* Generic connection tests. */
> > -	test_bind_and_connect(_metadata, &self->srv0, false, false);
> > -
> >   	/* Specific connection tests. */
> >   	bind_fd = socket_variant(&self->srv0);
> >   	ASSERT_LE(0, bind_fd);
> > @@ -726,8 +733,22 @@ TEST_F(protocol, connect_unspec)
> >   			EXPECT_EQ(0, ret);
> >   		}
> > +		if (variant->sandbox == TCP_SANDBOX) {
> > +			const int ruleset_fd = landlock_create_ruleset(
> > +				&ruleset_attr, sizeof(ruleset_attr), 0);
> > +			ASSERT_LE(0, ruleset_fd);
> > +
> > +			/* Allows connect. */
> > +			ASSERT_EQ(0,
> > +				  landlock_add_rule(ruleset_fd,
> > +						    LANDLOCK_RULE_NET_SERVICE,
> > +						    &tcp_connect, 0));
> > +			enforce_ruleset(_metadata, ruleset_fd);
> > +			EXPECT_EQ(0, close(ruleset_fd));
> > +		}
> > +
> >   		/* Disconnects already connected socket, or set peer. */
> > -		ret = connect_variant(connect_fd, &self->unspec_any);
> > +		ret = connect_variant(connect_fd, &self->unspec_any0);
> >   		if (self->srv0.protocol.domain == AF_UNIX &&
> >   		    self->srv0.protocol.type == SOCK_STREAM) {
> >   			EXPECT_EQ(-EINVAL, ret);
> > @@ -744,6 +765,25 @@ TEST_F(protocol, connect_unspec)
> >   			EXPECT_EQ(0, ret);
> >   		}
> > +		if (variant->sandbox == TCP_SANDBOX) {
> > +			const int ruleset_fd = landlock_create_ruleset(
> > +				&ruleset_attr, sizeof(ruleset_attr), 0);
> > +			ASSERT_LE(0, ruleset_fd);
> > +
> > +			/* Denies connect. */
> > +			enforce_ruleset(_metadata, ruleset_fd);
> > +			EXPECT_EQ(0, close(ruleset_fd));
> > +		}
> > +
> > +		ret = connect_variant(connect_fd, &self->unspec_any0);
> > +		if (self->srv0.protocol.domain == AF_UNIX &&
> > +		    self->srv0.protocol.type == SOCK_STREAM) {
> > +			EXPECT_EQ(-EINVAL, ret);
> > +		} else {
> > +			/* Always allowed to disconnect. */
> > +			EXPECT_EQ(0, ret);
> > +		}
> > +
> >   		EXPECT_EQ(0, close(connect_fd));
> >   		_exit(_metadata->passed ? EXIT_SUCCESS : EXIT_FAILURE);
> >   		return;