kernel/linux.git/security/landlock/ruleset.c, branch v6.18.22

landlock: Add AUDIT_LANDLOCK_DOMAIN and log domain status

2025-03-26T12:59:38+00:00

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 Acked-by: Paul Moore 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

landlock: Add AUDIT_LANDLOCK_ACCESS and log ptrace denials

2025-03-26T12:59:38+00:00

Add a new AUDIT_LANDLOCK_ACCESS record type dedicated to an access request denied by a Landlock domain. AUDIT_LANDLOCK_ACCESS indicates that something unexpected happened. For now, only denied access are logged, which means that any AUDIT_LANDLOCK_ACCESS record is always followed by a SYSCALL record with "success=no". However, log parsers should check this syscall property because this is the only sign that a request was denied. Indeed, we could have "success=yes" if Landlock would support a "permissive" mode. We could also add a new field to AUDIT_LANDLOCK_DOMAIN for this mode (see following commit). By default, the only logged access requests are those coming from the same executed program that enforced the Landlock restriction on itself. In other words, no audit record are created for a task after it called execve(2). This is required to avoid log spam because programs may only be aware of their own restrictions, but not the inherited ones. Following commits will allow to conditionally generate AUDIT_LANDLOCK_ACCESS records according to dedicated landlock_restrict_self(2)'s flags. The AUDIT_LANDLOCK_ACCESS message contains: - the "domain" ID restricting the action on an object, - the "blockers" that are missing to allow the requested access, - a set of fields identifying the related object (e.g. task identified with "opid" and "ocomm"). The blockers are implicit restrictions (e.g. ptrace), or explicit access rights (e.g. filesystem), or explicit scopes (e.g. signal). This field contains a list of at least one element, each separated with a comma. The initial blocker is "ptrace", which describe all implicit Landlock restrictions related to ptrace (e.g. deny tracing of tasks outside a sandbox). Add audit support to ptrace_access_check and ptrace_traceme hooks. For the ptrace_access_check case, we log the current/parent domain and the child task. For the ptrace_traceme case, we log the parent domain and the current/child task. Indeed, the requester and the target are the current task, but the action would be performed by the parent task. Audit event sample: type=LANDLOCK_ACCESS msg=audit(1729738800.349:44): domain=195ba459b blockers=ptrace opid=1 ocomm="systemd" type=SYSCALL msg=audit(1729738800.349:44): arch=c000003e syscall=101 success=no [...] pid=300 auid=0 A following commit adds user documentation. Add KUnit tests to check reading of domain ID relative to layer level. The quick return for non-landlocked tasks is moved from task_ptrace() to each LSM hooks. It is not useful to inline the audit_enabled check because other computation are performed by landlock_log_denial(). Use scoped guards for RCU read-side critical sections. Cc: Günther Noack Acked-by: Paul Moore Link: https://lore.kernel.org/r/20250320190717.2287696-10-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Move domain hierarchy management

2025-03-26T12:59:34+00:00

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 Link: https://lore.kernel.org/r/20250320190717.2287696-4-mic@digikod.net Reviewed-by: Günther Noack Signed-off-by: Mickaël Salaün

landlock: Fix grammar error

2025-02-14T08:23:08+00:00

Fix grammar error in comments that were identified using the codespell tool. Signed-off-by: Tanya Agarwal Reviewed-by: Günther Noack Link: https://lore.kernel.org/r/20250123194208.2660-1-tanyaagarwal25699@gmail.com [mic: Simplify commit message] Signed-off-by: Mickaël Salaün

landlock: Simplify initially denied access rights

2025-01-17T18:05:35+00:00

Upgrade domain's handled access masks when creating a domain from a ruleset, instead of converting them at runtime. This is more consistent and helps with audit support. Cc: Günther Noack Link: https://lore.kernel.org/r/20250108154338.1129069-7-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Move access types

2025-01-17T18:05:34+00:00

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 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

landlock: Use scoped guards for ruleset

2025-01-14T10:57:45+00:00

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 Link: https://lore.kernel.org/r/20250113161112.452505-2-mic@digikod.net Signed-off-by: Mickaël Salaün

landlock: Add abstract UNIX socket scoping

2024-09-16T21:50:45+00:00

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 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 Signed-off-by: Mickaël Salaün

landlock: Use bit-fields for storing handled layer access masks

2024-07-08T08:51:10+00:00

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 Cc: Tahera Fahimi 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 Link: https://lore.kernel.org/r/20240610082115.1693267-1-gnoack@google.com Signed-off-by: Mickaël Salaün

landlock: Optimize the number of calls to get_access_mask slightly

2024-01-03T11:43:17+00:00

This call is now going through a function pointer, and it is not as obvious any more that it will be inlined. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20231208155121.1943775-4-gnoack@google.com Fixes: 7a11275c3787 ("landlock: Refactor layer helpers") Signed-off-by: Mickaël Salaün