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Add audit support for sb_mount, move_mount, sb_umount, sb_remount, and
sb_pivot_root hooks.
The new related blocker is "fs.change_topology".
Audit event sample:
type=LANDLOCK_DENY msg=audit(1729738800.349:44): domain=195ba459b blockers=fs.change_topology name="/" dev="tmpfs" ino=1
Remove landlock_get_applicable_domain() and get_current_fs_domain()
which are now fully replaced with landlock_get_applicable_subject().
Cc: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-12-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Asynchronously log domain information when it first denies an access.
This minimize the amount of generated logs, which makes it possible to
always log denials for the current execution since they should not
happen. These records are identified with the new AUDIT_LANDLOCK_DOMAIN
type.
The AUDIT_LANDLOCK_DOMAIN message contains:
- the "domain" ID which is described;
- the "status" which can either be "allocated" or "deallocated";
- the "mode" which is for now only "enforcing";
- for the "allocated" status, a minimal set of properties to easily
identify the task that loaded the domain's policy with
landlock_restrict_self(2): "pid", "uid", executable path ("exe"), and
command line ("comm");
- for the "deallocated" state, the number of "denials" accounted to this
domain, which is at least 1.
This requires each domain to save these task properties at creation
time in the new struct landlock_details. A reference to the PID is kept
for the lifetime of the domain to avoid race conditions when
investigating the related task. The executable path is resolved and
stored to not keep a reference to the filesystem and block related
actions. All these metadata are stored for the lifetime of the related
domain and should then be minimal. The required memory is not accounted
to the task calling landlock_restrict_self(2) contrary to most other
Landlock allocations (see related comment).
The AUDIT_LANDLOCK_DOMAIN record follows the first AUDIT_LANDLOCK_ACCESS
record for the same domain, which is always followed by AUDIT_SYSCALL
and AUDIT_PROCTITLE. This is in line with the audit logic to first
record the cause of an event, and then add context with other types of
record.
Audit event sample for a first denial:
type=LANDLOCK_ACCESS msg=audit(1732186800.349:44): domain=195ba459b blockers=ptrace opid=1 ocomm="systemd"
type=LANDLOCK_DOMAIN msg=audit(1732186800.349:44): domain=195ba459b status=allocated mode=enforcing pid=300 uid=0 exe="/root/sandboxer" comm="sandboxer"
type=SYSCALL msg=audit(1732186800.349:44): arch=c000003e syscall=101 success=no [...] pid=300 auid=0
Audit event sample for a following denial:
type=LANDLOCK_ACCESS msg=audit(1732186800.372:45): domain=195ba459b blockers=ptrace opid=1 ocomm="systemd"
type=SYSCALL msg=audit(1732186800.372:45): arch=c000003e syscall=101 success=no [...] pid=300 auid=0
Log domain deletion with the "deallocated" state when a domain was
previously logged. This makes it possible for log parsers to free
potential resources when a domain ID will never show again.
The number of denied access requests is useful to easily check how many
access requests a domain blocked and potentially if some of them are
missing in logs because of audit rate limiting, audit rules, or Landlock
log configuration flags (see following commit).
Audit event sample for a deletion of a domain that denied something:
type=LANDLOCK_DOMAIN msg=audit(1732186800.393:46): domain=195ba459b status=deallocated denials=2
Cc: Günther Noack <gnoack@google.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-11-mic@digikod.net
[mic: Update comment and GFP flag for landlock_log_drop_domain()]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Create a new domain.h file containing the struct landlock_hierarchy
definition and helpers. This type will grow with audit support. This
also prepares for a new domain type.
Cc: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20250320190717.2287696-4-mic@digikod.net
Reviewed-by: Günther Noack <gnoack3000@gmail.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Move LANDLOCK_ACCESS_FS_INITIALLY_DENIED, access_mask_t, struct
access_mask, and struct access_masks_all to a dedicated access.h file.
Rename LANDLOCK_ACCESS_FS_INITIALLY_DENIED to
_LANDLOCK_ACCESS_FS_INITIALLY_DENIED to make it clear that it's not part
of UAPI. Add some newlines when appropriate.
This file will be extended with following commits, and it will help to
avoid dependency loops.
Cc: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20250108154338.1129069-6-mic@digikod.net
[mic: Fix rebase conflict because of the new cleanup headers]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Simplify error handling by replacing goto statements with automatic
calls to landlock_put_ruleset() when going out of scope.
This change will be easy to backport to v6.6 if needed, only the
kernel.h include line conflicts. As for any other similar changes, we
should be careful when backporting without goto statements.
Add missing include file.
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20250113161112.452505-2-mic@digikod.net
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Replace get_raw_handled_fs_accesses() with a generic
landlock_union_access_masks(), and replace get_fs_domain() with a
generic landlock_get_applicable_domain(). These helpers will also be
useful for other types of access.
Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20241109110856.222842-2-mic@digikod.net
[mic: Slightly improve doc as suggested by Günther]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Introduce a new "scoped" member to landlock_ruleset_attr that can
specify LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET to restrict connection to
abstract UNIX sockets from a process outside of the socket's domain.
Two hooks are implemented to enforce these restrictions:
unix_stream_connect and unix_may_send.
Closes: https://github.com/landlock-lsm/linux/issues/7
Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com>
Link: https://lore.kernel.org/r/5f7ad85243b78427242275b93481cfc7c127764b.1725494372.git.fahimitahera@gmail.com
[mic: Fix commit message formatting, improve documentation, simplify
hook_unix_may_send(), and cosmetic fixes including rename of
LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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When defined using bit-fields, the compiler takes care of packing the
bits in a memory-efficient way and frees us from defining
LANDLOCK_SHIFT_ACCESS_* by hand. The exact memory layout does not
matter in our use case.
The manual definition of LANDLOCK_SHIFT_ACCESS_* has resulted in bugs in
at least two recent patch sets [1] [2] where new kinds of handled access
rights were introduced.
Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
Cc: Tahera Fahimi <fahimitahera@gmail.com>
Link: https://lore.kernel.org/r/ebd680cc-25d6-ee14-4856-310f5e5e28e4@huawei-partners.com [1]
Link: https://lore.kernel.org/r/ZmLEoBfHyUR3nKAV@google.com [2]
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240610082115.1693267-1-gnoack@google.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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Add a new key_type argument to the landlock_init_layer_masks() helper.
Add a masks_array_size argument to the landlock_unmask_layers() helper.
These modifications support implementing new rule types in the next
Landlock versions.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-7-konstantin.meskhidze@huawei.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Move and rename landlock_unmask_layers() and landlock_init_layer_masks()
helpers to ruleset.c to share them with Landlock network implementation
in following commits.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-6-konstantin.meskhidze@huawei.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Add a new landlock_key union and landlock_id structure to support a
socket port rule type. A struct landlock_id identifies a unique entry
in a ruleset: either a kernel object (e.g. inode) or typed data (e.g.
TCP port). There is one red-black tree per key type.
Add is_object_pointer() and get_root() helpers. is_object_pointer()
returns true if key type is LANDLOCK_KEY_INODE. get_root() helper
returns a red-black tree root pointer according to a key type.
Refactor landlock_insert_rule() and landlock_find_rule() to support
coming network modifications. Adding or searching a rule in ruleset can
now be done thanks to a Landlock ID argument passed to these helpers.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-4-konstantin.meskhidze@huawei.com
[mic: Fix commit message typo]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Allow mount point and root directory changes when there is no filesystem
rule tied to the current Landlock domain. This doesn't change anything
for now because a domain must have at least a (filesystem) rule, but
this will change when other rule types will come. For instance, a domain
only restricting the network should have no impact on filesystem
restrictions.
Add a new get_current_fs_domain() helper to quickly check filesystem
rule existence for all filesystem LSM hooks.
Remove unnecessary inlining.
Link: https://lore.kernel.org/r/20231026014751.414649-3-konstantin.meskhidze@huawei.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Rename ruleset's access masks and modify it's type to access_masks_t
to support network type rules in following commits. Add filesystem
helper functions to add and get filesystem mask.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-2-konstantin.meskhidze@huawei.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).
As found with Coccinelle[1], add __counted_by for struct landlock_rule.
[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
Cc: Paul Moore <paul@paul-moore.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: linux-security-module@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230817210257.never.920-kees@kernel.org
Signed-off-by: Mickaël Salaün <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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Create and use the access_mask_t typedef to enforce a consistent access
mask size and uniformly use a 16-bits type. This will helps transition
to a 32-bits value one day.
Add a build check to make sure all (filesystem) access rights fit in.
This will be extended with a following commit.
Reviewed-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20220506161102.525323-2-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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Let's follow a consistent and documented coding style. Everything may
not be to our liking but it is better than tacit knowledge. Moreover,
this will help maintain style consistency between different developers.
This contains only whitespace changes.
Automatically formatted with:
clang-format-14 -i security/landlock/*.[ch] include/uapi/linux/landlock.h
Link: https://lore.kernel.org/r/20220506160513.523257-3-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
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A Landlock ruleset is mainly a red-black tree with Landlock rules as
nodes. This enables quick update and lookup to match a requested
access, e.g. to a file. A ruleset is usable through a dedicated file
descriptor (cf. following commit implementing syscalls) which enables a
process to create and populate a ruleset with new rules.
A domain is a ruleset tied to a set of processes. This group of rules
defines the security policy enforced on these processes and their future
children. A domain can transition to a new domain which is the
intersection of all its constraints and those of a ruleset provided by
the current process. This modification only impact the current process.
This means that a process can only gain more constraints (i.e. lose
accesses) over time.
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20210422154123.13086-3-mic@digikod.net
Signed-off-by: James Morris <jamorris@linux.microsoft.com>
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