Subject: Re: [RFC PATCH v1 03/10] selftests/landlock: Create 'create' test

From: Mickaël Salaün <[email-masked]>
Date: Wed, 8 May 2024 12:38:58 +0200

On Thu, Apr 11, 2024 at 06:58:34PM +0300, Ivanov Mikhail wrote:
> 
> 4/8/2024 4:08 PM, Günther Noack wrote:
> > Hello!
> > 
> > I am very happy to see this patch set, this is a very valuable feature, IMHO! :)
> > 
> > Regarding the subject of this patch:
> > 
> >    [RFC PATCH v1 03/10] selftests/landlock: Create 'create' test
> >                                                     ^^^^^^
> > 
> > This was probably meant to say "socket"?
> 
> I wanted each such patch to have the name of the test that this patch
> adds (without specifying the fixture, since this is not necessary
> information, which only complicates the name). I think
> 
>     [RFC PATCH v1 03/10] selftests/landlock: Add 'create' test
>                                              ~~~
> renaming should be fine.

Maybe something like this?
"selftests/landlock: Add protocol.create to socket tests"

> 
> > 
> > (In my mind, it is a good call to put the test in a separate file -
> > the existing test files have grown too large already.)
> > 
> > 
> > On Mon, Apr 08, 2024 at 05:39:20PM +0800, Ivanov Mikhail wrote:
> > > Initiate socket_test.c selftests. Add protocol fixture for tests
> > > with changeable domain/type values. Only most common variants of
> > > protocols (like ipv4-tcp,ipv6-udp, unix) were added.
> > > Add simple socket access right checking test.
> > > 
> > > Signed-off-by: Ivanov Mikhail <[email-masked]>
> > > Reviewed-by: Konstantin Meskhidze <[email-masked]>
> > > ---
> > >   .../testing/selftests/landlock/socket_test.c  | 197 ++++++++++++++++++
> > >   1 file changed, 197 insertions(+)
> > >   create mode 100644 tools/testing/selftests/landlock/socket_test.c
> > > 
> > > diff --git a/tools/testing/selftests/landlock/socket_test.c b/tools/testing/selftests/landlock/socket_test.c
> > > new file mode 100644
> > > index 000000000..525f4f7df
> > > --- /dev/null
> > > +++ b/tools/testing/selftests/landlock/socket_test.c
> > > @@ -0,0 +1,197 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * Landlock tests - Socket
> > > + *
> > > + * Copyright © 2024 Huawei Tech. Co., Ltd.
> > > + */
> > > +
> > > +#define _GNU_SOURCE
> > > +
> > > +#include <errno.h>
> > > +#include <linux/landlock.h>
> > > +#include <sched.h>
> > > +#include <string.h>
> > > +#include <sys/prctl.h>
> > > +#include <sys/socket.h>
> > > +
> > > +#include "common.h"
> > > +
> > > +/* clang-format off */
> > > +
> > > +#define ACCESS_LAST LANDLOCK_ACCESS_SOCKET_CREATE
> > > +
> > > +#define ACCESS_ALL ( \
> > > +	LANDLOCK_ACCESS_SOCKET_CREATE)
> > > +
> > > +/* clang-format on */
> > > +
> > > +struct protocol_variant {
> > > +	int domain;
> > > +	int type;
> > > +};
> > > +
> > > +struct service_fixture {
> > > +	struct protocol_variant protocol;
> > > +};
> > > +
> > > +static void setup_namespace(struct __test_metadata *const _metadata)
> > > +{
> > > +	set_cap(_metadata, CAP_SYS_ADMIN);
> > > +	ASSERT_EQ(0, unshare(CLONE_NEWNET));
> > > +	clear_cap(_metadata, CAP_SYS_ADMIN);
> > > +}
> > > +
> > > +static int socket_variant(const struct service_fixture *const srv)
> > > +{
> > > +	int ret;
> > > +
> > > +	ret = socket(srv->protocol.domain, srv->protocol.type | SOCK_CLOEXEC,
> > > +			 0);
> > > +	if (ret < 0)
> > > +		return -errno;
> > > +	return ret;
> > > +}
> > 
> > This helper is mostly concerned with mapping the error code.
> > 
> > In the fs_test.c, we have dealt with such use cases with helpers like
> > test_open_rel() and test_open().  These helpers attempt to open the file, take
> > the same arguments as open(2), but instead of returning the opened fd, they only
> > return 0 or errno.  Do you think this would be an option here?
> > 
> > Then you could write your tests as
> > 
> >    ASSERT_EQ(EACCES, test_socket(p->domain, p->type, 0));
> > 
> > and the test would (a) more obviously map to socket(2), and (b) keep relevant
> > information like the expected error code at the top level of the test.
> > 
> 
> I thought that `socket_variant()` would be suitable for future tests
> where sockets can be used after creation (e.g. for sending FDs). But
> until then, it's really better to replace it with what you suggested.

You can move common code/helpers from net_test.c to common.h (with a
dedicated patch) to avoid duplicating code.

> 
> > > +
> > > +FIXTURE(protocol)
> > > +{
> > > +	struct service_fixture srv0;
> > > +};
> > > +
> > > +FIXTURE_VARIANT(protocol)
> > > +{
> > > +	const struct protocol_variant protocol;
> > > +};
> > > +
> > > +FIXTURE_SETUP(protocol)
> > > +{
> > > +	disable_caps(_metadata);
> > > +	self->srv0.protocol = variant->protocol;
> > > +	setup_namespace(_metadata);
> > > +};
> > > +
> > > +FIXTURE_TEARDOWN(protocol)
> > > +{
> > > +}
> > > +
> > > +/* clang-format off */
> > > +FIXTURE_VARIANT_ADD(protocol, unspec) {
> > > +	/* clang-format on */
> > > +	.protocol = {
> > > +		.domain = AF_UNSPEC,
> > > +		.type = SOCK_STREAM,
> > > +	},
> > > +};
> > > +
> > > +/* clang-format off */
> > > +FIXTURE_VARIANT_ADD(protocol, unix_stream) {
> > > +	/* clang-format on */
> > > +	.protocol = {
> > > +		.domain = AF_UNIX,
> > > +		.type = SOCK_STREAM,
> > > +	},
> > > +};
> > > +
> > > +/* clang-format off */
> > > +FIXTURE_VARIANT_ADD(protocol, unix_dgram) {
> > > +	/* clang-format on */
> > > +	.protocol = {
> > > +		.domain = AF_UNIX,
> > > +		.type = SOCK_DGRAM,
> > > +	},
> > > +};
> > > +
> > > +/* clang-format off */
> > > +FIXTURE_VARIANT_ADD(protocol, ipv4_tcp) {
> > > +	/* clang-format on */
> > > +	.protocol = {
> > > +		.domain = AF_INET,
> > > +		.type = SOCK_STREAM,
> > > +	},
> > > +};
> > > +
> > > +/* clang-format off */
> > > +FIXTURE_VARIANT_ADD(protocol, ipv4_udp) {
> > > +	/* clang-format on */
> > > +	.protocol = {
> > > +		.domain = AF_INET,
> > > +		.type = SOCK_DGRAM,
> > > +	},
> > > +};
> > > +
> > > +/* clang-format off */
> > > +FIXTURE_VARIANT_ADD(protocol, ipv6_tcp) {
> > > +	/* clang-format on */
> > > +	.protocol = {
> > > +		.domain = AF_INET6,
> > > +		.type = SOCK_STREAM,
> > > +	},
> > > +};
> > > +
> > > +/* clang-format off */
> > > +FIXTURE_VARIANT_ADD(protocol, ipv6_udp) {
> > > +	/* clang-format on */
> > > +	.protocol = {
> > > +		.domain = AF_INET6,
> > > +		.type = SOCK_DGRAM,
> > > +	},
> > > +};
> > > +
> > > +static void test_socket_create(struct __test_metadata *const _metadata,
> > > +				  const struct service_fixture *const srv,
> > > +				  const bool deny_create)
> > > +{
> > > +	int fd;
> > > +
> > > +	fd = socket_variant(srv);
> > > +	if (srv->protocol.domain == AF_UNSPEC) {
> > > +		EXPECT_EQ(fd, -EAFNOSUPPORT);
> > > +	} else if (deny_create) {
> > > +		EXPECT_EQ(fd, -EACCES);

The deny_create argument/check should not be in this helper but in the
caller.

> > > +	} else {
> > > +		EXPECT_LE(0, fd)

This should be an ASSERT because the following code using fd would make
no sense if executed.

> > > +		{
> > > +			TH_LOG("Failed to create socket: %s", strerror(errno));
> > > +		}
> > > +		EXPECT_EQ(0, close(fd));
> > > +	}
> > > +}
> > 
> > This is slightly too much logic in a test helper, for my taste,
> > and the meaning of the true/false argument in the main test below
> > is not very obvious.
> > 
> > Extending the idea from above, if test_socket() was simpler, would it
> > be possible to turn these fixtures into something shorter like this:
> > 
> >    ASSERT_EQ(EAFNOSUPPORT, test_socket(AF_UNSPEC, SOCK_STREAM, 0));
> >    ASSERT_EQ(EACCES, test_socket(AF_UNIX, SOCK_STREAM, 0));
> >    ASSERT_EQ(EACCES, test_socket(AF_UNIX, SOCK_DGRAM, 0));
> >    ASSERT_EQ(EACCES, test_socket(AF_INET, SOCK_STREAM, 0));
> >    // etc.

I'd prefer that too.

> > 
> > Would that make the tests easier to write, to list out the table of
> > expected values aspect like that, rather than in a fixture?
> > 
> > 
> 
> Initially, I conceived this function as an entity that allows to
> separate the logic associated with the tested methods or usecases from
> the logic of configuring the state of the Landlock ruleset in the
> sandbox.
> 
> But at the moment, `test_socket_create()` is obviously a wrapper over
> socket(2). So for now it's worth removing unnecessary logic.
> 
> But i don't think it's worth removing the fixtures here:
> 
>   * in my opinion, the design of the fixtures is quite convenient.
>     It allows you to separate the definition of the object under test
>     from the test case. E.g. test protocol.create checks the ability of
>     Landlock to restrict the creation of a socket of a certain type,
>     rather than the ability to restrict creation of UNIX, TCP, UDP...
>     sockets

I'm not sure to understand, but we need to have positive and negative
tests, potentially in separate TEST_F().

> 
>   * with adding more tests, it may be necessary to check all protocols
>     in each of them
> 
> AF_UNSPEC should be removed from fixture variant to separate test,
> though.

Or you can add a new field to mark it as such.

A test should check that AF_UNSPEC cannot be restricted though.

> 
> > > +
> > > +TEST_F(protocol, create)
> > > +{
> > > +	const struct landlock_ruleset_attr ruleset_attr = {
> > > +		.handled_access_socket = LANDLOCK_ACCESS_SOCKET_CREATE,
> > > +	};
> > > +	const struct landlock_socket_attr create_socket_attr = {
> > > +		.allowed_access = LANDLOCK_ACCESS_SOCKET_CREATE,
> > > +		.domain = self->srv0.protocol.domain,
> > > +		.type = self->srv0.protocol.type,
> > > +	};
> > > +
> > > +	int ruleset_fd;
> > > +
> > > +	/* Allowed create */
> > > +	ruleset_fd = landlock_create_ruleset(&ruleset_attr,
> > > +							sizeof(ruleset_attr), 0);
> > > +	ASSERT_LE(0, ruleset_fd);
> > > +
> > > +	ASSERT_EQ(0,
> > > +			landlock_add_rule(ruleset_fd, LANDLOCK_RULE_SOCKET,
> > > +					&create_socket_attr, 0));
> > 
> > The indentation looks wrong?  We run clang-format on Landlock files.
> > 
> >    clang-format -i security/landlock/*.[ch] \
> >    	include/uapi/linux/landlock.h \
> >    	tools/testing/selftests/landlock/*.[ch]
> > 
> 
> Thanks! I'll fix indentation in the patch.

Please fix formatting in all patches.

You should have enough for a second patch series. :)