[PATCH v3] selftests/landlock: Add tests for io_uring openat access control with Landlock rules

[PATCH v3] selftests/landlock: Add tests for io_uring openat access control with Landlock rules

[Dorine Tipo]

This v3 patch expands Landlock test coverage to include io_uring
operations. It also introduces a test for IORING_OP_OPENAT with Landlock
rules, verifying allowed and disallowed access. This makes sure that
IORING_OP_OPENAT is well covered from security vulnerabilities by
ensuring Landlock controls access through io_uring.

It also updates Makefile to include -luring in the LDLIBS variable.
This ensures the test code has access to the necessary library for
io_uring operations.

The patch includes several improvements to the test_ioring_openat(),
FIXTURE_SETUP() and FIXTURE_TEARDOWN() addressing feedback received on
the initial version.

Signed-off-by: Dorine Tipo <dorine.a.tipo@gmail.com>
---
Changes since V1:
V2: - Consolidated two dependent patches in the V1 series into one patch
      as suggested by Fabio.
    - Updated The subject line to be more descriptive.

V3: - Added "selftests/landlock" subject prefix
    - Revised wording in the commit message to accurately reflect the
      test functionality as suggested by Mickaël.
    - Updated the Fixture set_up and tear_down to create and remove the
      necesssary files and folders for testing access.
    - renamed allowed_ruleset_fd and disallowed_ruleset_fd to ruleset_fd
      as suggest by Mickaël.
    - Moved all variable declarations to the top of the function.
    - Refactored the code to test only one allowed and one restricted
      path instead of iterating through all the paths.
    - Added comments to explain what is happening in different blocks
      of code
    - Removed the clang-format markers.
    - Removed unused arguments in the function definition.
    - Added a final rule struct with a null path to the allowed_rule
      and disallowed_rule arrays as suggested by Fabio.
    - CC'd the missing mailing lists as suggested by Shuah.
    - All executables have been included in the .gitignore so no updates
      are necessary.

 tools/testing/selftests/landlock/Makefile  |   4 +-
 tools/testing/selftests/landlock/fs_test.c | 140 +++++++++++++++++++++
 2 files changed, 142 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/landlock/Makefile b/tools/testing/selftests/landlock/Makefile
index 348e2dbdb4e0..ab47d1dadb62 100644
--- a/tools/testing/selftests/landlock/Makefile
+++ b/tools/testing/selftests/landlock/Makefile
@@ -13,11 +13,11 @@ TEST_GEN_PROGS := $(src_test:.c=)
 TEST_GEN_PROGS_EXTENDED := true

 # Short targets:
-$(TEST_GEN_PROGS): LDLIBS += -lcap
+$(TEST_GEN_PROGS): LDLIBS += -lcap -luring
 $(TEST_GEN_PROGS_EXTENDED): LDFLAGS += -static

 include ../lib.mk

 # Targets with $(OUTPUT)/ prefix:
-$(TEST_GEN_PROGS): LDLIBS += -lcap
+$(TEST_GEN_PROGS): LDLIBS += -lcap -luring
 $(TEST_GEN_PROGS_EXTENDED): LDFLAGS += -static
diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 9a6036fbf289..7147c75b6f79 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -21,7 +21,10 @@
 #include <sys/stat.h>
 #include <sys/sysmacros.h>
 #include <sys/vfs.h>
+#include <sys/types.h>
 #include <unistd.h>
+#include <liburing.h>
+#include <linux/io_uring.h>

 #include "common.h"

@@ -4874,4 +4877,141 @@ TEST_F_FORK(layout3_fs, release_inodes)
 	ASSERT_EQ(EACCES, test_open(TMP_DIR, O_RDONLY));
 }

+/* Test io_uring's IORING_OP_OPENAT access control with landlock rules */
+static int test_ioring_op_openat(struct __test_metadata *const _metadata, const __u64 access, const char **paths)
+{
+	int ruleset_fd;
+	int ret;
+	struct io_uring ring;
+	struct io_uring_sqe *sqe;
+
+	/* Test Allowed Access */
+	const struct rule allowed_rule[] = {
+		{
+			.path = paths[0],
+			.access = access,
+		},
+		{
+			.path = NULL,
+		},
+	};
+
+	ruleset_fd = create_ruleset(_metadata, allowed_rule[0].access, allowed_rule);
+
+	ASSERT_LE(0, ruleset_fd);
+
+	ret = io_uring_queue_init(32, &ring, 0);
+
+	ASSERT_EQ(0, ret);
+
+	/* Test allowed path */
+	sqe = io_uring_get_sqe(&ring);
+
+	/* Prepare SQE  for the openat operation */
+	io_uring_prep_openat(sqe, AT_FDCWD, paths[0], O_RDONLY, ruleset_fd);
+
+	/* Verify successful SQE preparation */
+	ASSERT_EQ(0, ret);
+
+	if (ret != 0)
+		return ret;
+
+	ret = io_uring_submit(&ring);
+
+	/* Verify 1 submission completed */
+	ASSERT_EQ(1, ret);
+
+	/* Test Disallowed Access */
+	const struct rule disallowed_rule[] = {
+		{
+			.path = paths[0],
+			.access = 0,
+		},
+		{
+			.path = NULL,
+		},
+	};
+
+	ruleset_fd = create_ruleset(_metadata, disallowed_rule[0].access, disallowed_rule);
+
+	ASSERT_LE(0, ruleset_fd);
+
+	/* Test disallowed path */
+	sqe = io_uring_get_sqe(&ring);
+
+	/* Prepare SQE  for the openat operation */
+	io_uring_prep_openat(sqe, AT_FDCWD, paths[0], O_RDONLY, ruleset_fd);
+
+	/* Verify successful SQE preparation */
+	ASSERT_EQ(0, ret);
+
+	if (ret != 0)
+		return ret;
+
+	ret = io_uring_submit(&ring);
+	/* Verify 1 submission completed */
+	ASSERT_EQ(0, ret);
+
+	/*  Cleanup: close ruleset fds, etc. */
+	close(ruleset_fd);
+
+	return 0;
+}
+
+FIXTURE(openat_test) {
+	struct __test_metadata *metadata;
+	const char *allowed_paths[11];
+	const char *disallowed_paths[2];
+};
+
+FIXTURE_SETUP(openat_test)
+{
+	/* initialize metadata, allowed_paths, and disallowed_paths */
+	self->metadata = _metadata;
+	const char *temp_allowed_paths[] = {
+		file1_s1d1, file2_s1d1, file1_s1d2, file2_s1d2,
+		file1_s1d3, file2_s1d3, file1_s2d1, file1_s2d2,
+		file1_s2d3, file2_s2d3, file1_s3d1};
+
+	memcpy(self->allowed_paths, temp_allowed_paths, sizeof(temp_allowed_paths));
+
+	const char *temp_disallowed_paths[] = {dir_s3d2, dir_s3d3};
+
+	memcpy(self->disallowed_paths, temp_disallowed_paths, sizeof(temp_disallowed_paths));
+
+	/* Create necessary directories and files */
+	for (int i = 0; i < sizeof(self->allowed_paths) / sizeof(char *); i++) {
+		create_file(self->metadata, self->allowed_paths[i]);
+	}
+
+	/* Create directories for disallowed paths */
+	for (int i = 0; i < sizeof(self->disallowed_paths) / sizeof(char *); i++) {
+		create_directory(self->metadata, self->disallowed_paths[i]);
+	}
+}
+
+FIXTURE_TEARDOWN(openat_test)
+{
+	/* Clean up test environment */
+	for (int i = 0; i < sizeof(self->allowed_paths) / sizeof(char *); i++) {
+		remove_path(self->allowed_paths[i]);
+	}
+
+	for (int i = 0; i < sizeof(self->disallowed_paths) / sizeof(char *); i++) {
+		remove_path(self->disallowed_paths[i]);
+	}
+}
+
+/* Test IORING_OP_OPENAT. */
+TEST_F_FORK(openat_test, test_ioring_op_openat_allowed)
+{
+	test_ioring_op_openat(self->metadata, LANDLOCK_ACCESS_FS_READ_FILE |
+			      LANDLOCK_ACCESS_FS_WRITE_FILE, self->allowed_paths);
+}
+
+TEST_F_FORK(openat_test, test_ioring_op_openat_disallowed)
+{
+	test_ioring_op_openat(self->metadata, 0, self->disallowed_paths);
+}
+
 TEST_HARNESS_MAIN
--
2.25.1

Re: [PATCH v3] selftests/landlock: Add tests for io_uring openat access control with Landlock rules

[Mickaël Salaün]

On Sat, Mar 30, 2024 at 12:48:17PM +0000, Dorine Tipo wrote:
> This v3 patch expands Landlock test coverage to include io_uring
> operations. It also introduces a test for IORING_OP_OPENAT with Landlock
> rules, verifying allowed and disallowed access. This makes sure that
> IORING_OP_OPENAT is well covered from security vulnerabilities by
> ensuring Landlock controls access through io_uring.
> 
> It also updates Makefile to include -luring in the LDLIBS variable.
> This ensures the test code has access to the necessary library for
> io_uring operations.
> 
> The patch includes several improvements to the test_ioring_openat(),
> FIXTURE_SETUP() and FIXTURE_TEARDOWN() addressing feedback received on
> the initial version.
> 
> Signed-off-by: Dorine Tipo <dorine.a.tipo@gmail.com>
> ---
> Changes since V1:
> V2: - Consolidated two dependent patches in the V1 series into one patch
>       as suggested by Fabio.
>     - Updated The subject line to be more descriptive.
> 
> V3: - Added "selftests/landlock" subject prefix
>     - Revised wording in the commit message to accurately reflect the
>       test functionality as suggested by Mickaël.
>     - Updated the Fixture set_up and tear_down to create and remove the
>       necesssary files and folders for testing access.
>     - renamed allowed_ruleset_fd and disallowed_ruleset_fd to ruleset_fd
>       as suggest by Mickaël.
>     - Moved all variable declarations to the top of the function.
>     - Refactored the code to test only one allowed and one restricted
>       path instead of iterating through all the paths.
>     - Added comments to explain what is happening in different blocks
>       of code
>     - Removed the clang-format markers.
>     - Removed unused arguments in the function definition.
>     - Added a final rule struct with a null path to the allowed_rule
>       and disallowed_rule arrays as suggested by Fabio.
>     - CC'd the missing mailing lists as suggested by Shuah.
>     - All executables have been included in the .gitignore so no updates
>       are necessary.
> 
>  tools/testing/selftests/landlock/Makefile  |   4 +-
>  tools/testing/selftests/landlock/fs_test.c | 140 +++++++++++++++++++++
>  2 files changed, 142 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/landlock/Makefile b/tools/testing/selftests/landlock/Makefile
> index 348e2dbdb4e0..ab47d1dadb62 100644
> --- a/tools/testing/selftests/landlock/Makefile
> +++ b/tools/testing/selftests/landlock/Makefile
> @@ -13,11 +13,11 @@ TEST_GEN_PROGS := $(src_test:.c=)
>  TEST_GEN_PROGS_EXTENDED := true
> 
>  # Short targets:
> -$(TEST_GEN_PROGS): LDLIBS += -lcap
> +$(TEST_GEN_PROGS): LDLIBS += -lcap -luring
>  $(TEST_GEN_PROGS_EXTENDED): LDFLAGS += -static
> 
>  include ../lib.mk
> 
>  # Targets with $(OUTPUT)/ prefix:
> -$(TEST_GEN_PROGS): LDLIBS += -lcap
> +$(TEST_GEN_PROGS): LDLIBS += -lcap -luring
>  $(TEST_GEN_PROGS_EXTENDED): LDFLAGS += -static
> diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
> index 9a6036fbf289..7147c75b6f79 100644
> --- a/tools/testing/selftests/landlock/fs_test.c
> +++ b/tools/testing/selftests/landlock/fs_test.c
> @@ -21,7 +21,10 @@
>  #include <sys/stat.h>
>  #include <sys/sysmacros.h>
>  #include <sys/vfs.h>
> +#include <sys/types.h>
>  #include <unistd.h>
> +#include <liburing.h>
> +#include <linux/io_uring.h>
> 
>  #include "common.h"
> 
> @@ -4874,4 +4877,141 @@ TEST_F_FORK(layout3_fs, release_inodes)
>  	ASSERT_EQ(EACCES, test_open(TMP_DIR, O_RDONLY));
>  }
> 
> +/* Test io_uring's IORING_OP_OPENAT access control with landlock rules */

What is tested exactly?

> +static int test_ioring_op_openat(struct __test_metadata *const _metadata, const __u64 access, const char **paths)
> +{
> +	int ruleset_fd;
> +	int ret;
> +	struct io_uring ring;
> +	struct io_uring_sqe *sqe;
> +
> +	/* Test Allowed Access */
> +	const struct rule allowed_rule[] = {
> +		{
> +			.path = paths[0],
> +			.access = access,
> +		},
> +		{
> +			.path = NULL,
> +		},
> +	};
> +
> +	ruleset_fd = create_ruleset(_metadata, allowed_rule[0].access, allowed_rule);
> +
> +	ASSERT_LE(0, ruleset_fd);
> +
> +	ret = io_uring_queue_init(32, &ring, 0);
> +
> +	ASSERT_EQ(0, ret);
> +
> +	/* Test allowed path */
> +	sqe = io_uring_get_sqe(&ring);
> +
> +	/* Prepare SQE  for the openat operation */
> +	io_uring_prep_openat(sqe, AT_FDCWD, paths[0], O_RDONLY, ruleset_fd);

Can you please explain what this call to io_uring_prep_openat() do?

> +
> +	/* Verify successful SQE preparation */
> +	ASSERT_EQ(0, ret);
> +
> +	if (ret != 0)
> +		return ret;
> +
> +	ret = io_uring_submit(&ring);
> +
> +	/* Verify 1 submission completed */
> +	ASSERT_EQ(1, ret);
> +
> +	/* Test Disallowed Access */
> +	const struct rule disallowed_rule[] = {
> +		{
> +			.path = paths[0],
> +			.access = 0,
> +		},
> +		{
> +			.path = NULL,
> +		},
> +	};
> +
> +	ruleset_fd = create_ruleset(_metadata, disallowed_rule[0].access, disallowed_rule);
> +
> +	ASSERT_LE(0, ruleset_fd);
> +
> +	/* Test disallowed path */
> +	sqe = io_uring_get_sqe(&ring);
> +
> +	/* Prepare SQE  for the openat operation */
> +	io_uring_prep_openat(sqe, AT_FDCWD, paths[0], O_RDONLY, ruleset_fd);
> +
> +	/* Verify successful SQE preparation */
> +	ASSERT_EQ(0, ret);
> +
> +	if (ret != 0)
> +		return ret;
> +
> +	ret = io_uring_submit(&ring);
> +	/* Verify 1 submission completed */
> +	ASSERT_EQ(0, ret);
> +
> +	/*  Cleanup: close ruleset fds, etc. */
> +	close(ruleset_fd);
> +
> +	return 0;
> +}
> +
> +FIXTURE(openat_test) {
> +	struct __test_metadata *metadata;
> +	const char *allowed_paths[11];
> +	const char *disallowed_paths[2];
> +};
> +
> +FIXTURE_SETUP(openat_test)
> +{
> +	/* initialize metadata, allowed_paths, and disallowed_paths */
> +	self->metadata = _metadata;
> +	const char *temp_allowed_paths[] = {
> +		file1_s1d1, file2_s1d1, file1_s1d2, file2_s1d2,
> +		file1_s1d3, file2_s1d3, file1_s2d1, file1_s2d2,
> +		file1_s2d3, file2_s2d3, file1_s3d1};
> +
> +	memcpy(self->allowed_paths, temp_allowed_paths, sizeof(temp_allowed_paths));
> +
> +	const char *temp_disallowed_paths[] = {dir_s3d2, dir_s3d3};
> +
> +	memcpy(self->disallowed_paths, temp_disallowed_paths, sizeof(temp_disallowed_paths));
> +
> +	/* Create necessary directories and files */
> +	for (int i = 0; i < sizeof(self->allowed_paths) / sizeof(char *); i++) {
> +		create_file(self->metadata, self->allowed_paths[i]);
> +	}
> +
> +	/* Create directories for disallowed paths */
> +	for (int i = 0; i < sizeof(self->disallowed_paths) / sizeof(char *); i++) {
> +		create_directory(self->metadata, self->disallowed_paths[i]);
> +	}
> +}
> +
> +FIXTURE_TEARDOWN(openat_test)
> +{
> +	/* Clean up test environment */
> +	for (int i = 0; i < sizeof(self->allowed_paths) / sizeof(char *); i++) {
> +		remove_path(self->allowed_paths[i]);
> +	}
> +
> +	for (int i = 0; i < sizeof(self->disallowed_paths) / sizeof(char *); i++) {
> +		remove_path(self->disallowed_paths[i]);
> +	}
> +}
> +
> +/* Test IORING_OP_OPENAT. */
> +TEST_F_FORK(openat_test, test_ioring_op_openat_allowed)
> +{
> +	test_ioring_op_openat(self->metadata, LANDLOCK_ACCESS_FS_READ_FILE |
> +			      LANDLOCK_ACCESS_FS_WRITE_FILE, self->allowed_paths);
> +}
> +
> +TEST_F_FORK(openat_test, test_ioring_op_openat_disallowed)
> +{
> +	test_ioring_op_openat(self->metadata, 0, self->disallowed_paths);
> +}
> +
>  TEST_HARNESS_MAIN
> --
> 2.25.1
> 
> 

(no subject)

[Dorine Tipo]

Subject: [PATCH v3] selftests/landlock: Add tests for io_uring openat access control with Landlock rules

> What is tested exactly?

The test_ioring_op_openat() function is testing the enforcement of
Landlock rules for read-only access.
It's specifically checking whether the Landlock rules correctly allow or
deny read-only access to the specified file when using the openat system
call with io_uring. The test does this by preparing a submission queue
entry for the openat operation with io_uring_prep_openat(), submitting
this operation to the kernel via io_uring, and then checking the result.
If the operation is successful, it means that Landlock allowed the read-only
access as expected. If the operation fails, it means that Landlock correctly
denied the access.

> +static int test_ioring_op_openat(struct __test_metadata *const _metadata, const __u64 access, const char **paths)
> +{
> +     int ruleset_fd;
> +     int ret;
> +     struct io_uring ring;
> +     struct io_uring_sqe *sqe;
> +
> +     /* Test Allowed Access */
> +     const struct rule allowed_rule[] = {
> +             {
> +                     .path = paths[0],
> +                     .access = access,
> +             },
> +             {
> +                     .path = NULL,
> +             },
> +     };
> +
> +     ruleset_fd = create_ruleset(_metadata, allowed_rule[0].access, allowed_rule);
> +
> +     ASSERT_LE(0, ruleset_fd);
> +
> +     ret = io_uring_queue_init(32, &ring, 0);
> +
> +     ASSERT_EQ(0, ret);
> +
> +     /* Test allowed path */
> +     sqe = io_uring_get_sqe(&ring);
> +
> +     /* Prepare SQE  for the openat operation */
> +     io_uring_prep_openat(sqe, AT_FDCWD, paths[0], O_RDONLY, ruleset_fd);

> Can you please explain what this call to io_uring_prep_openat() do?

io_uring_prep_openat() prepares the submission queue entry for the openat
system call. In my tests the call to io_uring_prep_openat() is preparing
an openat operation to open a file at a certain path with read-only access.
This operation is then submitted to the kernel via io_uring, and the test
checks whether the operation is allowed or denied based on the define
Landlock rules.

Re: [PATCH v3] selftests/landlock: Add tests for io_uring openat access control with Landlock rules

[Mickaël Salaün]

> Subject: Re: your mail

There is an issue with the subject.

On Thu, Apr 04, 2024 at 12:16:21PM +0000, Dorine Tipo wrote:
> 
> > What is tested exactly?
> 
> The test_ioring_op_openat() function is testing the enforcement of
> Landlock rules for read-only access.
> It's specifically checking whether the Landlock rules correctly allow or
> deny read-only access to the specified file when using the openat system
> call with io_uring. The test does this by preparing a submission queue
> entry for the openat operation with io_uring_prep_openat(), submitting
> this operation to the kernel via io_uring, and then checking the result.
> If the operation is successful, it means that Landlock allowed the read-only
> access as expected. If the operation fails, it means that Landlock correctly
> denied the access.

That doesn't reflect the content of this patch.

> 
> > +static int test_ioring_op_openat(struct __test_metadata *const _metadata, const __u64 access, const char **paths)
> > +{
> > +     int ruleset_fd;
> > +     int ret;
> > +     struct io_uring ring;
> > +     struct io_uring_sqe *sqe;
> > +
> > +     /* Test Allowed Access */
> > +     const struct rule allowed_rule[] = {
> > +             {
> > +                     .path = paths[0],
> > +                     .access = access,
> > +             },
> > +             {
> > +                     .path = NULL,
> > +             },
> > +     };
> > +
> > +     ruleset_fd = create_ruleset(_metadata, allowed_rule[0].access, allowed_rule);
> > +
> > +     ASSERT_LE(0, ruleset_fd);
> > +
> > +     ret = io_uring_queue_init(32, &ring, 0);
> > +
> > +     ASSERT_EQ(0, ret);
> > +
> > +     /* Test allowed path */
> > +     sqe = io_uring_get_sqe(&ring);
> > +
> > +     /* Prepare SQE  for the openat operation */
> > +     io_uring_prep_openat(sqe, AT_FDCWD, paths[0], O_RDONLY, ruleset_fd);
> 
> > Can you please explain what this call to io_uring_prep_openat() do?
> 
> io_uring_prep_openat() prepares the submission queue entry for the openat
> system call. In my tests the call to io_uring_prep_openat() is preparing
> an openat operation to open a file at a certain path with read-only access.
> This operation is then submitted to the kernel via io_uring, and the test
> checks whether the operation is allowed or denied based on the define
> Landlock rules.

This is not what is tested by this patch.

What is the last argument of io_uring_prep_openat()?  Did you write this
code?