| Commit message (Collapse) | Author | Age | Files | Lines |
|---|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
Currently, a sandbox process is not restricted to sending a signal (e.g.
SIGKILL) to a process outside the sandbox environment. The ability to
send a signal for a sandboxed process should be scoped the same way
abstract UNIX sockets are scoped. Therefore, we extend the "scoped"
field in a ruleset with LANDLOCK_SCOPE_SIGNAL to specify that a ruleset
will deny sending any signal from within a sandbox process to its parent
(i.e. any parent sandbox or non-sandboxed processes).
This patch adds file_set_fowner and file_free_security hooks to set and
release a pointer to the file owner's domain. This pointer, fown_domain
in landlock_file_security will be used in file_send_sigiotask to check
if the process can send a signal.
The ruleset_with_unknown_scope test is updated to support
LANDLOCK_SCOPE_SIGNAL.
This depends on two new changes:
- commit 1934b212615d ("file: reclaim 24 bytes from f_owner"): replace
container_of(fown, struct file, f_owner) with fown->file .
- commit 26f204380a3c ("fs: Fix file_set_fowner LSM hook
inconsistencies"): lock before calling the hook.
Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com>
Closes: https://github.com/landlock-lsm/linux/issues/8
Link: https://lore.kernel.org/r/df2b4f880a2ed3042992689a793ea0951f6798a5.1725657727.git.fahimitahera@gmail.com
[mic: Update landlock_get_current_domain()'s return type, improve and
fix locking in hook_file_set_fowner(), simplify and fix sleepable call
and locking issue in hook_file_send_sigiotask() and rebase on the latest
VFS tree, simplify hook_task_kill() and quickly return when not
sandboxed, improve comments, rename LANDLOCK_SCOPED_SIGNAL]
Co-developed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
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>
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
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>
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
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>
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
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>
|
| |
|
|
|
|
|
|
|
|
| |
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>
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
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>
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
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
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
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>
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
| |
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>
|
| |
|
|
|
|
|
|
|
|
|
| |
In preparation to a following commit, add clang-format on and
clang-format off stanzas around constant definitions. This enables to
keep aligned values, which is much more readable than packed
definitions.
Link: https://lore.kernel.org/r/20220506160513.523257-2-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
Using Landlock objects and ruleset, it is possible to tag inodes
according to a process's domain. To enable an unprivileged process to
express a file hierarchy, it first needs to open a directory (or a file)
and pass this file descriptor to the kernel through
landlock_add_rule(2). When checking if a file access request is
allowed, we walk from the requested dentry to the real root, following
the different mount layers. The access to each "tagged" inodes are
collected according to their rule layer level, and ANDed to create
access to the requested file hierarchy. This makes possible to identify
a lot of files without tagging every inodes nor modifying the
filesystem, while still following the view and understanding the user
has from the filesystem.
Add a new ARCH_EPHEMERAL_INODES for UML because it currently does not
keep the same struct inodes for the same inodes whereas these inodes are
in use.
This commit adds a minimal set of supported filesystem access-control
which doesn't enable to restrict all file-related actions. This is the
result of multiple discussions to minimize the code of Landlock to ease
review. Thanks to the Landlock design, extending this access-control
without breaking user space will not be a problem. Moreover, seccomp
filters can be used to restrict the use of syscall families which may
not be currently handled by Landlock.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Serge E. Hallyn <serge@hallyn.com>
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
Link: https://lore.kernel.org/r/20210422154123.13086-8-mic@digikod.net
Signed-off-by: James Morris <jamorris@linux.microsoft.com>
|
|
|
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>
|
