kernel/linux.git/security/landlock/syscalls.c, branch v6.11.8

landlock: Various documentation improvements

2024-07-18T06:27:47+00:00

* Fix some typos, incomplete or confusing phrases. * Split paragraphs where appropriate. * List the same error code multiple times, if it has multiple possible causes. * Bring wording closer to the man page wording, which has undergone more thorough review (esp. for LANDLOCK_ACCESS_FS_WRITE_FILE). * Small semantic clarifications * Call the ephemeral port range "ephemeral" * Clarify reasons for EFAULT in landlock_add_rule() * Clarify @rule_type doc for landlock_add_rule() This is a collection of small fixes which I collected when preparing the corresponding man pages [1]. Cc: Alejandro Colomar Cc: Konstantin Meskhidze Link: https://lore.kernel.org/r/20240715155554.2791018-1-gnoack@google.com [1] Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240715160328.2792835-2-gnoack@google.com [mic: Add label to link, fix formatting spotted by make htmldocs, synchronize userspace-api documentation's date] Signed-off-by: Mickaël Salaün

landlock: Add IOCTL access right for character and block devices

2024-05-13T04:58:29+00:00

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 Cc: Christian Brauner Cc: Arnd Bergmann Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20240419161122.2023765-2-gnoack@google.com Signed-off-by: Mickaël Salaün

landlock: Warn once if a Landlock action is requested while disabled

2024-03-07T10:29:46+00:00

Because sandboxing can be used as an opportunistic security measure, user space may not log unsupported features. Let the system administrator know if an application tries to use Landlock but failed because it isn't enabled at boot time. This may be caused by boot loader configurations with outdated "lsm" kernel's command-line parameter. Cc: stable@vger.kernel.org Fixes: 265885daf3e5 ("landlock: Add syscall implementations") Reviewed-by: Kees Cook Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20240227110550.3702236-2-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Support network rules with TCP bind and connect

2023-10-26T19:07:15+00:00

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 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 Signed-off-by: Mickaël Salaün

landlock: Refactor landlock_add_rule() syscall

2023-10-26T19:07:14+00:00

Change the landlock_add_rule() syscall to support new rule types with next commits. Add the add_rule_path_beneath() helper to support current filesystem rules. Signed-off-by: Konstantin Meskhidze Link: https://lore.kernel.org/r/20231026014751.414649-8-konstantin.meskhidze@huawei.com Signed-off-by: Mickaël Salaün

landlock: Allow FS topology changes for domains without such rule type

2023-10-26T19:07:10+00:00

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

landlock: Make ruleset's access masks more generic

2023-10-26T19:07:09+00:00

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 Link: https://lore.kernel.org/r/20231026014751.414649-2-konstantin.meskhidze@huawei.com Signed-off-by: Mickaël Salaün

landlock: Support file truncation

2022-10-19T07:01:44+00:00

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 Signed-off-by: Günther Noack Acked-by: Paul Moore (LSM) Link: https://lore.kernel.org/r/20221018182216.301684-5-gnoack3000@gmail.com Signed-off-by: Mickaël Salaün

landlock: Fix documentation style

2022-09-29T16:43:04+00:00

It seems that all code should use double backquotes, which is also used to convert "%" defines. Let's use an homogeneous style and remove all use of simple backquotes (which should only be used for emphasis). Cc: Günther Noack Cc: Paul Moore Signed-off-by: Mickaël Salaün Link: https://lore.kernel.org/r/20220923154207.3311629-4-mic@digikod.net

landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER

2022-05-23T11:27:59+00:00

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 Signed-off-by: Mickaël Salaün Link: https://lore.kernel.org/r/20220506161102.525323-8-mic@digikod.net