diff options
Diffstat (limited to 'Documentation/userspace-api/landlock.rst')
| -rw-r--r-- | Documentation/userspace-api/landlock.rst | 25 |
1 files changed, 13 insertions, 12 deletions
diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst index 83bae71bf042..cec780c2f497 100644 --- a/Documentation/userspace-api/landlock.rst +++ b/Documentation/userspace-api/landlock.rst @@ -69,7 +69,7 @@ should try to protect users as much as possible whatever the kernel they are using. To avoid binary enforcement (i.e. either all security features or none), we can leverage a dedicated Landlock command to get the current version of the Landlock ABI and adapt the handled accesses. Let's check if we should -remove the `LANDLOCK_ACCESS_FS_REFER` access right which is only supported +remove the ``LANDLOCK_ACCESS_FS_REFER`` access right which is only supported starting with the second version of the ABI. .. code-block:: c @@ -128,7 +128,7 @@ descriptor. It may also be required to create rules following the same logic as explained for the ruleset creation, by filtering access rights according to the Landlock ABI version. In this example, this is not required because -`LANDLOCK_ACCESS_FS_REFER` is not allowed by any rule. +``LANDLOCK_ACCESS_FS_REFER`` is not allowed by any rule. We now have a ruleset with one rule allowing read access to ``/usr`` while denying all other handled accesses for the filesystem. The next step is to @@ -154,8 +154,8 @@ The current thread is now ready to sandbox itself with the ruleset. } close(ruleset_fd); -If the `landlock_restrict_self` system call succeeds, the current thread is now -restricted and this policy will be enforced on all its subsequently created +If the ``landlock_restrict_self`` system call succeeds, the current thread is +now restricted and this policy will be enforced on all its subsequently created children as well. Once a thread is landlocked, there is no way to remove its security policy; only adding more restrictions is allowed. These threads are now in a new Landlock domain, merge of their parent one (if any) with the new @@ -175,7 +175,8 @@ depend on their location (i.e. parent directories). This is particularly relevant when we want to allow linking or renaming. Indeed, having consistent access rights per directory enables to change the location of such directory without relying on the destination directory access rights (except those that -are required for this operation, see `LANDLOCK_ACCESS_FS_REFER` documentation). +are required for this operation, see ``LANDLOCK_ACCESS_FS_REFER`` +documentation). Having self-sufficient hierarchies also helps to tighten the required access rights to the minimal set of data. This also helps avoid sinkhole directories, i.e. directories where data can be linked to but not linked from. However, @@ -259,7 +260,7 @@ Backward and forward compatibility Landlock is designed to be compatible with past and future versions of the kernel. This is achieved thanks to the system call attributes and the -associated bitflags, particularly the ruleset's `handled_access_fs`. Making +associated bitflags, particularly the ruleset's ``handled_access_fs``. Making handled access right explicit enables the kernel and user space to have a clear contract with each other. This is required to make sure sandboxing will not get stricter with a system update, which could break applications. @@ -394,7 +395,7 @@ according to the potentially lost constraints. To protect against privilege escalations through renaming or linking, and for the sake of simplicity, Landlock previously limited linking and renaming to the same directory. Starting with the Landlock ABI version 2, it is now possible to securely -control renaming and linking thanks to the new `LANDLOCK_ACCESS_FS_REFER` +control renaming and linking thanks to the new ``LANDLOCK_ACCESS_FS_REFER`` access right. .. _kernel_support: @@ -403,14 +404,14 @@ Kernel support ============== Landlock was first introduced in Linux 5.13 but it must be configured at build -time with `CONFIG_SECURITY_LANDLOCK=y`. Landlock must also be enabled at boot +time with ``CONFIG_SECURITY_LANDLOCK=y``. Landlock must also be enabled at boot time as the other security modules. The list of security modules enabled by -default is set with `CONFIG_LSM`. The kernel configuration should then -contains `CONFIG_LSM=landlock,[...]` with `[...]` as the list of other +default is set with ``CONFIG_LSM``. The kernel configuration should then +contains ``CONFIG_LSM=landlock,[...]`` with ``[...]`` as the list of other potentially useful security modules for the running system (see the -`CONFIG_LSM` help). +``CONFIG_LSM`` help). -If the running kernel does not have `landlock` in `CONFIG_LSM`, then we can +If the running kernel does not have ``landlock`` in ``CONFIG_LSM``, then we can still enable it by adding ``lsm=landlock,[...]`` to Documentation/admin-guide/kernel-parameters.rst thanks to the bootloader configuration. |