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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>
22 lines
931 B
Plaintext
22 lines
931 B
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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config SECURITY_LANDLOCK
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bool "Landlock support"
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depends on SECURITY && !ARCH_EPHEMERAL_INODES
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select SECURITY_PATH
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help
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Landlock is a sandboxing mechanism that enables processes to restrict
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themselves (and their future children) by gradually enforcing
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tailored access control policies. A Landlock security policy is a
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set of access rights (e.g. open a file in read-only, make a
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directory, etc.) tied to a file hierarchy. Such policy can be
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configured and enforced by any processes for themselves using the
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dedicated system calls: landlock_create_ruleset(),
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landlock_add_rule(), and landlock_restrict_self().
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See Documentation/userspace-api/landlock.rst for further information.
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If you are unsure how to answer this question, answer N. Otherwise,
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you should also prepend "landlock," to the content of CONFIG_LSM to
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enable Landlock at boot time.
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