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Introduces the LANDLOCK_ACCESS_FS_IOCTL_DEV right
and increments the Landlock ABI version to 5.
This access right applies to device-custom IOCTL commands
when they are invoked on block or character device files.
Like the truncate right, this right is associated with a file
descriptor at the time of open(2), and gets respected even when the
file descriptor is used outside of the thread which it was originally
opened in.
Therefore, a newly enabled Landlock policy does not apply to file
descriptors which are already open.
If the LANDLOCK_ACCESS_FS_IOCTL_DEV right is handled, only a small
number of safe IOCTL commands will be permitted on newly opened device
files. These include FIOCLEX, FIONCLEX, FIONBIO and FIOASYNC, as well
as other IOCTL commands for regular files which are implemented in
fs/ioctl.c.
Noteworthy scenarios which require special attention:
TTY devices are often passed into a process from the parent process,
and so a newly enabled Landlock policy does not retroactively apply to
them automatically. In the past, TTY devices have often supported
IOCTL commands like TIOCSTI and some TIOCLINUX subcommands, which were
letting callers control the TTY input buffer (and simulate
keypresses). This should be restricted to CAP_SYS_ADMIN programs on
modern kernels though.
Known limitations:
The LANDLOCK_ACCESS_FS_IOCTL_DEV access right is a coarse-grained
control over IOCTL commands.
Landlock users may use path-based restrictions in combination with
their knowledge about the file system layout to control what IOCTLs
can be done.
Cc: Paul Moore <paul@paul-moore.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240419161122.2023765-2-gnoack@google.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Setting the time namespace with CLONE_NEWTIME returns -EUSERS if the
calling thread shares memory with another thread (because of the shared
vDSO), which is the case when it is created with vfork().
Fix pidfd_setns_test by replacing test harness's vfork() call with a
clone3() call with CLONE_VFORK, and an explicit sharing of the
_metadata and self objects.
Replace _metadata->teardown_parent with a new FIXTURE_TEARDOWN_PARENT()
helper that can replace FIXTURE_TEARDOWN(). This is a cleaner approach
and it enables to selectively share the fixture data between the child
process running tests and the parent process running the fixture
teardown. This also avoids updating several tests to not rely on the
self object's copy-on-write property (e.g. storing the returned value of
a fork() call).
Cc: Christian Brauner <brauner@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Günther Noack <gnoack@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Will Drewry <wad@chromium.org>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202403291015.1fcfa957-oliver.sang@intel.com
Fixes: 0710a1a73fb4 ("selftests/harness: Merge TEST_F_FORK() into TEST_F()")
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20240511171445.904356-10-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Do not allocate self->dir_path in the test process because this would
not be visible in the FIXTURE_TEARDOWN() process when relying on
fork()/clone3() instead of vfork().
This change is required for a following commit removing vfork() call to
not break the layout3_fs.* test cases.
Cc: Günther Noack <gnoack@google.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20240511171445.904356-6-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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According to the test environment, the mount point of the test's working
directory may be shared or not, which changes the visibility of the
nested "tmp" mount point for the test's parent process calling
umount("tmp").
This was spotted while running tests in containers [1], where mount
points are private.
Cc: Günther Noack <gnoack@google.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Link: https://github.com/landlock-lsm/landlock-test-tools/pull/4 [1]
Fixes: 41cca0542d7c ("selftests/harness: Fix TEST_F()'s vfork handling")
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20240511171445.904356-3-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux
Pull landlock updates from Mickaël Salaün:
"Some miscellaneous improvements, including new KUnit tests, extended
documentation and boot help, and some cosmetic cleanups.
Additional test changes already went through the net tree"
* tag 'landlock-6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux:
samples/landlock: Don't error out if a file path cannot be opened
landlock: Use f_cred in security_file_open() hook
landlock: Rename "ptrace" files to "task"
landlock: Simplify current_check_access_socket()
landlock: Warn once if a Landlock action is requested while disabled
landlock: Extend documentation for kernel support
landlock: Add support for KUnit tests
selftests/landlock: Clean up error logs related to capabilities
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Always run fixture setup in the grandchild process, and by default also
run the teardown in the same process. However, this change makes it
possible to run the teardown in a parent process when
_metadata->teardown_parent is set to true (e.g. in fixture setup).
Fix TEST_SIGNAL() by forwarding grandchild's signal to its parent. Fix
seccomp tests by running the test setup in the parent of the test
thread, as expected by the related test code. Fix Landlock tests by
waiting for the grandchild before processing _metadata.
Use of exit(3) in tests should be OK because the environment in which
the vfork(2) call happen is already dedicated to the running test (with
flushed stdio, setpgrp() call), see __run_test() and the call to fork(2)
just before running the setup/test/teardown. Even if the test
configures its own exit handlers, they will not be run by the parent
because it never calls exit(3), and the test function either ends with a
call to _exit(2) or a signal.
Cc: Günther Noack <gnoack@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Will Drewry <wad@chromium.org>
Fixes: 0710a1a73fb4 ("selftests/harness: Merge TEST_F_FORK() into TEST_F()")
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Reported-by: Mark Brown <broonie@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20240305201029.1331333-1-mic@digikod.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Instead of tracking passed = 0/1 rename the field to exit_code
and invert the values so that they match the KSFT_* exit codes.
This will allow us to fold SKIP / XFAIL into the same value.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Replace Landlock-specific TEST_F_FORK() with an improved TEST_F() which
brings four related changes:
Run TEST_F()'s tests in a grandchild process to make it possible to
drop privileges and delegate teardown to the parent.
Compared to TEST_F_FORK(), simplify handling of the test grandchild
process thanks to vfork(2), and makes it generic (e.g. no explicit
conversion between exit code and _metadata).
Compared to TEST_F_FORK(), run teardown even when tests failed with an
assert thanks to commit 63e6b2a42342 ("selftests/harness: Run TEARDOWN
for ASSERT failures").
Simplify the test harness code by removing the no_print and step fields
which are not used. I added this feature just after I made
kselftest_harness.h more broadly available but this step counter
remained even though it wasn't needed after all. See commit 369130b63178
("selftests: Enhance kselftest_harness.h to print which assert failed").
Replace spaces with tabs in one line of __TEST_F_IMPL().
Cc: Günther Noack <gnoack@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Will Drewry <wad@chromium.org>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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This has the effect of creating a new test process for either TEST_F()
or TEST_F_FORK(), which doesn't change tests but will ease potential
backports. See next commit for the TEST_F_FORK() merge into TEST_F().
Cc: Günther Noack <gnoack@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Will Drewry <wad@chromium.org>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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It doesn't help to call TH_LOG() for every cap_*() error. Let's only
log errors returned by the kernel, not by libcap specificities.
Link: https://lore.kernel.org/r/20240125153230.3817165-3-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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CAP_NET_ADMIN allows to configure network interfaces, not CAP_SYS_ADMIN
which only allows to call unshare(2). Without this change, running
network tests as a non-root user but with all capabilities would fail at
the setup_loopback() step with "RTNETLINK answers: Operation not
permitted".
The issue is only visible when running tests with non-root users (i.e.
only relying on ambient capabilities). Indeed, when configuring the
network interface, the "ip" command is called, which may lead to the
special handling of capabilities for the root user by execve(2). If
root is the caller, then the inherited, permitted and effective
capabilities are all reset, which then includes CAP_NET_ADMIN. However,
if a non-root user is the caller, then ambient capabilities are masked
by the inherited ones, which were explicitly dropped.
To make execution deterministic whatever users are running the tests,
set the noroot secure bit for each test, and set the inheritable and
ambient capabilities to CAP_NET_ADMIN, the only capability that may be
required after an execve(2).
Factor out _effective_cap() into _change_cap(), and use it to manage
ambient capabilities with the new set_ambient_cap() and
clear_ambient_cap() helpers.
This makes it possible to run all Landlock tests with check-linux.sh
from https://github.com/landlock-lsm/landlock-test-tools
Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Fixes: a549d055a22e ("selftests/landlock: Add network tests")
Link: https://lore.kernel.org/r/20240125153230.3817165-2-mic@digikod.net
[mic: Make sure SECBIT_NOROOT_LOCKED is set]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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One issue comes up while building selftest/landlock/fs_test on my side
(gcc 7.3/glibc-2.28/kernel-4.19).
gcc -Wall -O2 -isystem fs_test.c -lcap -o selftests/landlock/fs_test
fs_test.c:4575:9: error: initializer element is not constant
.mnt = mnt_tmp,
^~~~~~~
Signed-off-by: Hu Yadi <hu.yadi@h3c.com>
Suggested-by: Jiao <jiaoxupo@h3c.com>
Reviewed-by: Berlin <berlin@h3c.com>
Link: https://lore.kernel.org/r/20240124022908.42100-1-hu.yadi@h3c.com
Fixes: 04f9070e99a4 ("selftests/landlock: Add tests for pseudo filesystems")
[mic: Factor out mount's data string and make mnt_tmp static]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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One issue comes up while building selftest/landlock/net_test on my side
(gcc 7.3/glibc-2.28/kernel-4.19).
net_test.c: In function ‘set_service’:
net_test.c:91:45: warning: implicit declaration of function ‘gettid’; [-Wimplicit-function-declaration]
"_selftests-landlock-net-tid%d-index%d", gettid(),
^~~~~~
getgid
net_test.c:(.text+0x4e0): undefined reference to `gettid'
Signed-off-by: Hu Yadi <hu.yadi@h3c.com>
Suggested-by: Jiao <jiaoxupo@h3c.com>
Reviewed-by: Berlin <berlin@h3c.com>
Fixes: a549d055a22e ("selftests/landlock: Add network tests")
Link: https://lore.kernel.org/r/20240123062621.25082-1-hu.yadi@h3c.com
[mic: Cosmetic fixes]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Suggested-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20231208155121.1943775-3-gnoack@google.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Add two tests to make sure that we cannot add a rule to a ruleset if the
rule's access rights that are not handled by the ruleset:
* fs: layout1.rule_with_unhandled_access
* net: mini.rule_with_unhandled_access
Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20231130093616.67340-3-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Add two tests to make sure that we cannot add a rule with access
rights that are unknown:
* fs: layout0.rule_with_unknown_access
* net: mini.rule_with_unknown_access
Rename unknown_access_rights tests to ruleset_with_unknown_access .
Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20231130093616.67340-2-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Add 2 tests to the layout1 fixture:
* topology_changes_with_net_only: Checks that FS topology
changes are not denied by network-only restrictions.
* topology_changes_with_net_and_fs: Make sure that FS topology
changes are still denied with FS and network restrictions.
This specifically test commit d7220364039f ("landlock: Allow FS topology
changes for domains without such rule type").
Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231027154615.815134-1-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Add 82 test suites to check edge cases related to bind() and connect()
actions. They are defined with 6 fixtures and their variants:
The "protocol" fixture is extended with 12 variants defined as a matrix
of: sandboxed/not-sandboxed, IPv4/IPv6/unix network domain, and
stream/datagram socket. 4 related tests suites are defined:
* bind: Tests bind action.
* connect: Tests connect action.
* bind_unspec: Tests bind action with the AF_UNSPEC socket family.
* connect_unspec: Tests connect action with the AF_UNSPEC socket family.
The "ipv4" fixture is extended with 4 variants defined as a matrix
of: sandboxed/not-sandboxed, and stream/datagram socket. 1 related test
suite is defined:
* from_unix_to_inet: Tests to make sure unix sockets' actions are not
restricted by Landlock rules applied to TCP ones.
The "tcp_layers" fixture is extended with 8 variants defined as a matrix
of: IPv4/IPv6 network domain, and different number of landlock rule
layers. 2 related tests suites are defined:
* ruleset_overlap: Tests nested layers with less constraints.
* ruleset_expand: Tests nested layers with more constraints.
In the "mini" fixture 4 tests suites are defined:
* network_access_rights: Tests handling of known access rights.
* unknown_access_rights: Tests handling of unknown access rights.
* inval: Tests unhandled allowed access and zero access value.
* tcp_port_overflow: Tests with port values greater than 65535.
The "ipv4_tcp" fixture supports IPv4 network domain with stream socket.
2 tests suites are defined:
* port_endianness: Tests with big/little endian port formats.
* with_fs: Tests a ruleset with both filesystem and network
restrictions.
The "port_specific" fixture is extended with 4 variants defined
as a matrix of: sandboxed/not-sandboxed, IPv4/IPv6 network domain,
and stream socket. 2 related tests suites are defined:
* bind_connect_zero: Tests with port 0.
* bind_connect_1023: Tests with port 1023.
Test coverage for security/landlock is 92.4% of 710 lines according to
gcc/gcov-13.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-11-konstantin.meskhidze@huawei.com
[mic: Extend commit message, update test coverage, clean up capability
use, fix useless TEST_F_FORK, and improve ipv4_tcp.with_fs]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Move enforce_ruleset() helper function to common.h so that it can be
used both by filesystem tests and network ones.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-10-konstantin.meskhidze@huawei.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Add network rules support in the ruleset management helpers and the
landlock_create_ruleset() syscall. Extend user space API to support
network actions:
* Add new network access rights: LANDLOCK_ACCESS_NET_BIND_TCP and
LANDLOCK_ACCESS_NET_CONNECT_TCP.
* Add a new network rule type: LANDLOCK_RULE_NET_PORT tied to struct
landlock_net_port_attr. The allowed_access field contains the network
access rights, and the port field contains the port value according to
the controlled protocol. This field can take up to a 64-bit value
but the maximum value depends on the related protocol (e.g. 16-bit
value for TCP). Network port is in host endianness [1].
* Add a new handled_access_net field to struct landlock_ruleset_attr
that contains network access rights.
* Increment the Landlock ABI version to 4.
Implement socket_bind() and socket_connect() LSM hooks, which enable
to control TCP socket binding and connection to specific ports.
Expand access_masks_t from u16 to u32 to be able to store network access
rights alongside filesystem access rights for rulesets' handled access
rights.
Access rights are not tied to socket file descriptors but checked at
bind() or connect() call time against the caller's Landlock domain. For
the filesystem, a file descriptor is a direct access to a file/data.
However, for network sockets, we cannot identify for which data or peer
a newly created socket will give access to. Indeed, we need to wait for
a connect or bind request to identify the use case for this socket.
Likewise a directory file descriptor may enable to open another file
(i.e. a new data item), but this opening is also restricted by the
caller's domain, not the file descriptor's access rights [2].
[1] https://lore.kernel.org/r/278ab07f-7583-a4e0-3d37-1bacd091531d@digikod.net
[2] https://lore.kernel.org/r/263c1eb3-602f-57fe-8450-3f138581bee7@digikod.net
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-9-konstantin.meskhidze@huawei.com
[mic: Extend commit message, fix typo in comments, and specify
endianness in the documentation]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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The opened file should be closed before return, otherwise resource leak
will occur.
Signed-off-by: Ding Xiang <dingxiang@cmss.chinamobile.com>
Link: https://lore.kernel.org/r/20230830101148.3738-1-dingxiang@cmss.chinamobile.com
Fixes: 3de64b656b3c ("selftests/landlock: Add supports_filesystem() helper")
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Add tests for the hostfs filesystems to make sure it has a consistent
inode management, which is required for Landlock's file hierarchy
identification. This adds 5 new tests for layout3_fs with the hostfs
variant.
Add hostfs to the new (architecture-specific) config.um file.
The hostfs filesystem, only available for an User-Mode Linux kernel, is
special because we cannot explicitly mount it. The layout3_fs.hostfs
variant tests are skipped if the current test directory is not backed by
this filesystem.
The layout3_fs.hostfs.tag_inode_dir_child and
layout3_fs.hostfs.tag_inode_file tests pass thanks to a previous commit
fixing hostfs inode management. Without this fix, the deny-by-default
policy would apply and all access requests would be denied.
Link: https://lore.kernel.org/r/20230612191430.339153-7-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Add generic and read-only tests for 6 pseudo filesystems to make sure
they have a consistent inode management, which is required for
Landlock's file hierarchy identification:
- tmpfs
- ramfs
- cgroup2
- proc
- sysfs
Update related kernel configuration to support these new filesystems,
remove useless CONFIG_SECURITY_PATH, and sort all entries. If these
filesystems are not supported by the kernel running tests, the related
tests are skipped.
Expanding variants, this adds 25 new tests for layout3_fs:
- tag_inode_dir_parent
- tag_inode_dir_mnt
- tag_inode_dir_child
- tag_inode_dir_file
- release_inodes
Test coverage for security/landlock with kernel debug code:
- 94.7% of 835 lines according to gcc/gcov-12
- 93.0% of 852 lines according to gcc/gcov-13
Test coverage for security/landlock without kernel debug code:
- 95.5% of 624 lines according to gcc/gcov-12
- 93.1% of 641 lines according to gcc/gcov-13
Link: https://lore.kernel.org/r/20230612191430.339153-6-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Add a new struct mnt_opt to define a mount point with the mount_opt()
helper. This doesn't change tests but prepare for the next commit.
Link: https://lore.kernel.org/r/20230612191430.339153-5-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Replace supports_overlayfs() with supports_filesystem() to be able to
check several filesystems. This will be useful in a following commit.
Only check for overlay filesystem once in the setup step, and then rely
on self->skip_test.
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Jeff Xu <jeffxu@google.com>
Link: https://lore.kernel.org/r/20230612191430.339153-4-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Add and use a layout0 test fixture to not populate the tmpfs filesystem
if it is not required for tests: unknown_access_rights, proc_nsfs,
unpriv and max_layers.
This doesn't change these tests but it speeds up their setup and makes
them less prone to error. This prepare the ground for a next commit.
Link: https://lore.kernel.org/r/20230612191430.339153-3-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Update ptrace tests according to all potential Yama security policies.
This is required to make such tests pass even if Yama is enabled.
Tests are not skipped but they now check both Landlock and Yama boundary
restrictions at run time to keep a maximum test coverage (i.e. positive
and negative testing).
Signed-off-by: Jeff Xu <jeffxu@google.com>
Link: https://lore.kernel.org/r/20230114020306.1407195-2-jeffxu@google.com
Cc: stable@vger.kernel.org
[mic: Add curly braces around EXPECT_EQ() to make it build, and improve
commit message]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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overlayfs may be disabled in the kernel configuration, causing related
tests to fail. Check that overlayfs is supported at runtime, so we can
skip layout2_overlay.* accordingly.
Signed-off-by: Jeff Xu <jeffxu@google.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230113053229.1281774-2-jeffxu@google.com
[mic: Reword comments and constify variables]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux
Pull landlock updates from Mickaël Salaün:
"This adds file truncation support to Landlock, contributed by Günther
Noack. As described by Günther [1], the goal of these patches is to
work towards a more complete coverage of file system operations that
are restrictable with Landlock.
The known set of currently unsupported file system operations in
Landlock is described at [2]. Out of the operations listed there,
truncate is the only one that modifies file contents, so these patches
should make it possible to prevent the direct modification of file
contents with Landlock.
The new LANDLOCK_ACCESS_FS_TRUNCATE access right covers both the
truncate(2) and ftruncate(2) families of syscalls, as well as open(2)
with the O_TRUNC flag. This includes usages of creat() in the case
where existing regular files are overwritten.
Additionally, this introduces a new Landlock security blob associated
with opened files, to track the available Landlock access rights at
the time of opening the file. This is in line with Unix's general
approach of checking the read and write permissions during open(), and
associating this previously checked authorization with the opened
file. An ongoing patch documents this use case [3].
In order to treat truncate(2) and ftruncate(2) calls differently in an
LSM hook, we split apart the existing security_path_truncate hook into
security_path_truncate (for truncation by path) and
security_file_truncate (for truncation of previously opened files)"
Link: https://lore.kernel.org/r/20221018182216.301684-1-gnoack3000@gmail.com [1]
Link: https://www.kernel.org/doc/html/v6.1/userspace-api/landlock.html#filesystem-flags [2]
Link: https://lore.kernel.org/r/20221209193813.972012-1-mic@digikod.net [3]
* tag 'landlock-6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux:
samples/landlock: Document best-effort approach for LANDLOCK_ACCESS_FS_REFER
landlock: Document Landlock's file truncation support
samples/landlock: Extend sample tool to support LANDLOCK_ACCESS_FS_TRUNCATE
selftests/landlock: Test ftruncate on FDs created by memfd_create(2)
selftests/landlock: Test FD passing from restricted to unrestricted processes
selftests/landlock: Locally define __maybe_unused
selftests/landlock: Test open() and ftruncate() in multiple scenarios
selftests/landlock: Test file truncation support
landlock: Support file truncation
landlock: Document init_layer_masks() helper
landlock: Refactor check_access_path_dual() into is_access_to_paths_allowed()
security: Create file_truncate hook from path_truncate hook
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The only (forced) static test binary doesn't depend on libcap. Because
using -lcap on systems that don't have such static library would fail
(e.g. on Arch Linux), let's be more specific and require only dynamic
libcap linking.
Fixes: a52540522c95 ("selftests/landlock: Fix out-of-tree builds")
Cc: Anders Roxell <anders.roxell@linaro.org>
Cc: Guillaume Tucker <guillaume.tucker@collabora.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20221019200536.2771316-1-mic@digikod.net
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All file descriptors that are truncatable need to have the Landlock
access rights set correctly on the file's Landlock security blob. This
is also the case for files that are opened by other means than
open(2).
Test coverage for security/landlock is 94.7% of 838 lines according to
gcc/gcov-11.
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20221018182216.301684-10-gnoack3000@gmail.com
[mic: Add test coverage in commit message]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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A file descriptor created in a restricted process carries Landlock
restrictions with it which will apply even if the same opened file is
used from an unrestricted process.
This change extracts suitable FD-passing helpers from base_test.c and
moves them to common.h. We use the fixture variants from the ftruncate
fixture to exercise the same scenarios as in the open_and_ftruncate
test, but doing the Landlock restriction and open() in a different
process than the ftruncate() call.
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20221018182216.301684-9-gnoack3000@gmail.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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The checkpatch tool started to flag __attribute__(__unused__), which
we previously used. The header where this is normally defined is not
currently compatible with selftests.
This is the same approach as used in selftests/net/psock_lib.h.
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20221018182216.301684-8-gnoack3000@gmail.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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This test uses multiple fixture variants to exercise a broader set of
scnenarios.
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20221018182216.301684-7-gnoack3000@gmail.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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These tests exercise the following truncation operations:
* truncate() (truncate by path)
* ftruncate() (truncate by file descriptor)
* open with the O_TRUNC flag
* special case: creat(), which is open with O_CREAT|O_WRONLY|O_TRUNC.
in the following scenarios:
* Files with read, write and truncate rights.
* Files with read and truncate rights.
* Files with the truncate right.
* Files without the truncate right.
In particular, the following scenarios are enforced with the test:
* open() with O_TRUNC requires the truncate right, if it truncates a file.
open() already checks security_path_truncate() in this case,
and it required no additional check in the Landlock LSM's file_open hook.
* creat() requires the truncate right
when called with an existing filename.
* creat() does *not* require the truncate right
when it's creating a new file.
* ftruncate() requires that the file was opened by a thread that had
the truncate right for the file at the time of open(). (The rights
are carried along with the opened file.)
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20221018182216.301684-6-gnoack3000@gmail.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Introduce the LANDLOCK_ACCESS_FS_TRUNCATE flag for file truncation.
This flag hooks into the path_truncate, file_truncate and
file_alloc_security LSM hooks and covers file truncation using
truncate(2), ftruncate(2), open(2) with O_TRUNC, as well as creat().
This change also increments the Landlock ABI version, updates
corresponding selftests, and updates code documentation to document
the flag.
In security/security.c, allocate security blobs at pointer-aligned
offsets. This fixes the problem where one LSM's security blob can
shift another LSM's security blob to an unaligned address (reported
by Nathan Chancellor).
The following operations are restricted:
open(2): requires the LANDLOCK_ACCESS_FS_TRUNCATE right if a file gets
implicitly truncated as part of the open() (e.g. using O_TRUNC).
Notable special cases:
* open(..., O_RDONLY|O_TRUNC) can truncate files as well in Linux
* open() with O_TRUNC does *not* need the TRUNCATE right when it
creates a new file.
truncate(2) (on a path): requires the LANDLOCK_ACCESS_FS_TRUNCATE
right.
ftruncate(2) (on a file): requires that the file had the TRUNCATE
right when it was previously opened. File descriptors acquired by
other means than open(2) (e.g. memfd_create(2)) continue to support
truncation with ftruncate(2).
Cc: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Acked-by: Paul Moore <paul@paul-moore.com> (LSM)
Link: https://lore.kernel.org/r/20221018182216.301684-5-gnoack3000@gmail.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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These changes simplify the Makefile and handle these 5 ways to build
Landlock tests:
- make -C tools/testing/selftests/landlock
- make -C tools/testing/selftests TARGETS=landlock gen_tar
- make TARGETS=landlock kselftest-gen_tar
- make TARGETS=landlock O=build kselftest-gen_tar
- make -C /tmp/linux TARGETS=landlock O=/tmp/build kselftest-gen_tar
This also makes $(KHDR_INCLUDES) available to other test collections
when building in their directory.
Fixes: f1227dc7d041 ("selftests/landlock: fix broken include of linux/landlock.h")
Fixes: 3bb267a36185 ("selftests: drop khdr make target")
Cc: Anders Roxell <anders.roxell@linaro.org>
Cc: Guillaume Tucker <guillaume.tucker@collabora.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20220909103402.1501802-1-mic@digikod.net
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git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux
Pull landlock fix from Mickaël Salaün:
"This fixes a mis-handling of the LANDLOCK_ACCESS_FS_REFER right when
multiple rulesets/domains are stacked.
The expected behaviour was that an additional ruleset can only
restrict the set of permitted operations, but in this particular case,
it was potentially possible to re-gain the LANDLOCK_ACCESS_FS_REFER
right"
* tag 'landlock-6.0-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux:
landlock: Fix file reparenting without explicit LANDLOCK_ACCESS_FS_REFER
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This change fixes a mis-handling of the LANDLOCK_ACCESS_FS_REFER right
when multiple rulesets/domains are stacked. The expected behaviour was
that an additional ruleset can only restrict the set of permitted
operations, but in this particular case, it was potentially possible to
re-gain the LANDLOCK_ACCESS_FS_REFER right.
With the introduction of LANDLOCK_ACCESS_FS_REFER, we added the first
globally denied-by-default access right. Indeed, this lifted an initial
Landlock limitation to rename and link files, which was initially always
denied when the source or the destination were different directories.
This led to an inconsistent backward compatibility behavior which was
only taken into account if no domain layer were using the new
LANDLOCK_ACCESS_FS_REFER right. However, when restricting a thread with
a new ruleset handling LANDLOCK_ACCESS_FS_REFER, all inherited parent
rulesets/layers not explicitly handling LANDLOCK_ACCESS_FS_REFER would
behave as if they were handling this access right and with all their
rules allowing it. This means that renaming and linking files could
became allowed by these parent layers, but all the other required
accesses must also be granted: all layers must allow file removal or
creation, and renaming and linking operations cannot lead to privilege
escalation according to the Landlock policy. See detailed explanation
in commit b91c3e4ea756 ("landlock: Add support for file reparenting with
LANDLOCK_ACCESS_FS_REFER").
To say it another way, this bug may lift the renaming and linking
limitations of the initial Landlock version, and a same ruleset can
enforce different restrictions depending on previous or next enforced
ruleset (i.e. inconsistent behavior). The LANDLOCK_ACCESS_FS_REFER right
cannot give access to data not already allowed, but this doesn't follow
the contract of the first Landlock ABI. This fix puts back the
limitation for sandboxes that didn't opt-in for this additional right.
For instance, if a first ruleset allows LANDLOCK_ACCESS_FS_MAKE_REG on
/dst and LANDLOCK_ACCESS_FS_REMOVE_FILE on /src, renaming /src/file to
/dst/file is denied. However, without this fix, stacking a new ruleset
which allows LANDLOCK_ACCESS_FS_REFER on / would now permit the
sandboxed thread to rename /src/file to /dst/file .
This change fixes the (absolute) rule access rights, which now always
forbid LANDLOCK_ACCESS_FS_REFER except when it is explicitly allowed
when creating a rule.
Making all domain handle LANDLOCK_ACCESS_FS_REFER was an initial
approach but there is two downsides:
* it makes the code more complex because we still want to check that a
rule allowing LANDLOCK_ACCESS_FS_REFER is legitimate according to the
ruleset's handled access rights (i.e. ABI v1 != ABI v2);
* it would not allow to identify if the user created a ruleset
explicitly handling LANDLOCK_ACCESS_FS_REFER or not, which will be an
issue to audit Landlock.
Instead, this change adds an ACCESS_INITIALLY_DENIED list of
denied-by-default rights, which (only) contains
LANDLOCK_ACCESS_FS_REFER. All domains are treated as if they are also
handling this list, but without modifying their fs_access_masks field.
A side effect is that the errno code returned by rename(2) or link(2)
*may* be changed from EXDEV to EACCES according to the enforced
restrictions. Indeed, we now have the mechanic to identify if an access
is denied because of a required right (e.g. LANDLOCK_ACCESS_FS_MAKE_REG,
LANDLOCK_ACCESS_FS_REMOVE_FILE) or if it is denied because of missing
LANDLOCK_ACCESS_FS_REFER rights. This may result in different errno
codes than for the initial Landlock version, but this approach is more
consistent and better for rename/link compatibility reasons, and it
wasn't possible before (hence no backport to ABI v1). The
layout1.rename_file test reflects this change.
Add 4 layout1.refer_denied_by_default* test suites to check that the
behavior of a ruleset not handling LANDLOCK_ACCESS_FS_REFER (ABI v1) is
unchanged even if another layer handles LANDLOCK_ACCESS_FS_REFER (i.e.
ABI v1 precedence). Make sure rule's absolute access rights are correct
by testing with and without a matching path. Add test_rename() and
test_exchange() helpers.
Extend layout1.inval tests to check that a denied-by-default access
right is not necessarily part of a domain's handled access rights.
Test coverage for security/landlock is 95.3% of 599 lines according to
gcc/gcov-11.
Fixes: b91c3e4ea756 ("landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER")
Reviewed-by: Paul Moore <paul@paul-moore.com>
Reviewed-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20220831203840.1370732-1-mic@digikod.net
Cc: stable@vger.kernel.org
[mic: Constify and slightly simplify test helpers]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Revert part of the earlier changes to fix the kselftest build when
using a sub-directory from the top of the tree as this broke the
landlock test build as a side-effect when building with "make -C
tools/testing/selftests/landlock".
Reported-by: Mickaël Salaün <mic@digikod.net>
Fixes: a917dd94b832 ("selftests/landlock: drop deprecated headers dependency")
Fixes: f2745dc0ba3d ("selftests: stop using KSFT_KHDR_INSTALL")
Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
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The khdr make target has been removed, so drop it from the landlock
Makefile dependencies as well as related include paths that are
standard for headers in the kernel tree.
Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
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Stop using the KSFT_KHDR_INSTALL flag as installing the kernel headers
from the kselftest Makefile is causing some issues. Instead, rely on
the headers to be installed directly by the top-level Makefile
"headers_install" make target prior to building kselftest.
Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Tested-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
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These test suites try to check all edge cases for directory and file
renaming or linking involving a new parent directory, with and without
LANDLOCK_ACCESS_FS_REFER and other access rights.
layout1:
* reparent_refer: Tests simple FS_REFER usage.
* reparent_link: Tests a mix of FS_MAKE_REG and FS_REFER with links.
* reparent_rename: Tests a mix of FS_MAKE_REG and FS_REFER with renames
and RENAME_EXCHANGE.
* reparent_exdev_layers_rename1/2: Tests renames with two layers.
* reparent_exdev_layers_exchange1/2/3: Tests exchanges with two layers.
* reparent_remove: Tests file and directory removal with rename.
* reparent_dom_superset: Tests access partial ordering.
layout1_bind:
* reparent_cross_mount: Tests FS_REFER propagation across mount points.
Test coverage for security/landlock is 95.4% of 604 lines according to
gcc/gcov-11.
Cc: Paul Moore <paul@paul-moore.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20220506161102.525323-9-mic@digikod.net
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Add a new LANDLOCK_ACCESS_FS_REFER access right to enable policy writers
to allow sandboxed processes to link and rename files from and to a
specific set of file hierarchies. This access right should be composed
with LANDLOCK_ACCESS_FS_MAKE_* for the destination of a link or rename,
and with LANDLOCK_ACCESS_FS_REMOVE_* for a source of a rename. This
lift a Landlock limitation that always denied changing the parent of an
inode.
Renaming or linking to the same directory is still always allowed,
whatever LANDLOCK_ACCESS_FS_REFER is used or not, because it is not
considered a threat to user data.
However, creating multiple links or renaming to a different parent
directory may lead to privilege escalations if not handled properly.
Indeed, we must be sure that the source doesn't gain more privileges by
being accessible from the destination. This is handled by making sure
that the source hierarchy (including the referenced file or directory
itself) restricts at least as much the destination hierarchy. If it is
not the case, an EXDEV error is returned, making it potentially possible
for user space to copy the file hierarchy instead of moving or linking
it.
Instead of creating different access rights for the source and the
destination, we choose to make it simple and consistent for users.
Indeed, considering the previous constraint, it would be weird to
require such destination access right to be also granted to the source
(to make it a superset). Moreover, RENAME_EXCHANGE would also add to
the confusion because of paths being both a source and a destination.
See the provided documentation for additional details.
New tests are provided with a following commit.
Reviewed-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20220506161102.525323-8-mic@digikod.net
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The original behavior was to check if the full set of requested accesses
was allowed by at least a rule of every relevant layer. This didn't
take into account requests for multiple accesses and same-layer rules
allowing the union of these accesses in a complementary way. As a
result, multiple accesses requested on a file hierarchy matching rules
that, together, allowed these accesses, but without a unique rule
allowing all of them, was illegitimately denied. This case should be
rare in practice and it can only be triggered by the path_rename or
file_open hook implementations.
For instance, if, for the same layer, a rule allows execution
beneath /a/b and another rule allows read beneath /a, requesting access
to read and execute at the same time for /a/b should be allowed for this
layer.
This was an inconsistency because the union of same-layer rule accesses
was already allowed if requested once at a time anyway.
This fix changes the way allowed accesses are gathered over a path walk.
To take into account all these rule accesses, we store in a matrix all
layer granting the set of requested accesses, according to the handled
accesses. To avoid heap allocation, we use an array on the stack which
is 2*13 bytes. A following commit bringing the LANDLOCK_ACCESS_FS_REFER
access right will increase this size to reach 112 bytes (2*14*4) in case
of link or rename actions.
Add a new layout1.layer_rule_unions test to check that accesses from
different rules pertaining to the same layer are ORed in a file
hierarchy. Also test that it is not the case for rules from different
layers.
Reviewed-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20220506161102.525323-5-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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The maximum number of nested Landlock domains is currently 64. Because
of the following fix and to help reduce the stack size, let's reduce it
to 16. This seems large enough for a lot of use cases (e.g. sandboxed
init service, spawning a sandboxed SSH service, in nested sandboxed
containers). Reducing the number of nested domains may also help to
discover misuse of Landlock (e.g. creating a domain per rule).
Add and use a dedicated layer_mask_t typedef to fit with the number of
layers. This might be useful when changing it and to keep it consistent
with the maximum number of layers.
Reviewed-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20220506161102.525323-3-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Add inval_create_ruleset_arguments, extension of
inval_create_ruleset_flags, to also check error ordering for
landlock_create_ruleset(2).
This is similar to the previous commit checking landlock_add_rule(2).
Test coverage for security/landlock is 94.4% of 504 lines accorging to
gcc/gcov-11.
Link: https://lore.kernel.org/r/20220506160820.524344-11-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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According to the Landlock goal to be a security feature available to
unprivileges processes, it makes more sense to first check for
no_new_privs before checking anything else (i.e. syscall arguments).
Merge inval_fd_enforce and unpriv_enforce_without_no_new_privs tests
into the new restrict_self_checks_ordering. This is similar to the
previous commit checking other syscalls.
Link: https://lore.kernel.org/r/20220506160820.524344-10-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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This makes more sense to first check the ruleset FD and then the rule
attribute. It will be useful to factor out code for other rule types.
Add inval_add_rule_arguments tests, extension of empty_path_beneath_attr
tests, to also check error ordering for landlock_add_rule(2).
Link: https://lore.kernel.org/r/20220506160820.524344-9-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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The O_PATH flag is currently not handled by Landlock. Let's make sure
this behavior will remain consistent with the same ruleset over time.
Cc: Shuah Khan <shuah@kernel.org>
Link: https://lore.kernel.org/r/20220506160820.524344-8-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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