Denied access requests are logged by default for a sandboxed program if `audit`
is enabled. This default behavior can be changed with the
sys_landlock_restrict_self() flags (cf.
-Documentation/userspace-api/landlock.rst). Landlock logs can also be masked
-thanks to audit rules. Landlock can generate 2 audit record types.
+Documentation/userspace-api/landlock.rst), or suppressed on a per-object
+basis by using ``LANDLOCK_ADD_RULE_QUIET`` (ABI 10+). Landlock logs can
+also be masked thanks to audit rules. Landlock can generate 2 audit
+record types.
Record types
------------
attack attempt or a bug in the security policy. We can put in place some
filters to limit noise with two complementary ways:
-- with sys_landlock_restrict_self()'s flags if we can fix the sandboxed
+- with sys_landlock_restrict_self()'s flags, or
+ ``LANDLOCK_ADD_RULE_QUIET`` (ABI 10+) if we can fix the sandboxed
programs,
- or with audit rules (see :manpage:`auditctl(8)`).
datagrams to an explicit remote port (ignoring any destination set on
UDP sockets, via e.g. :manpage:`sendto(2)`).
+Quiet rule flag (ABI < 10)
+--------------------------
+
+Starting with the Landlock ABI version 10, it is possible to selectively
+suppress logs for specific denied accesses on a per-object basis with
+the ``LANDLOCK_ADD_RULE_QUIET`` flag of sys_landlock_add_rule(), in
+combination with the ``quiet_access_fs`` and ``quiet_access_net`` fields
+of struct landlock_ruleset_attr. It is also now possible to suppress
+logs for scope accesses via the ``quiet_scoped`` field of struct
+landlock_ruleset_attr. The object is marked as quiet within a ruleset
+when at least one sys_landlock_add_rule() call is made for it with the
+``LANDLOCK_ADD_RULE_QUIET`` flag, additional add-rule calls for the same
+object without this flag do not clear it.
+
.. _kernel_support:
Kernel support
* *handle* a wide range or all access rights that they know about at build time
* (and that they have tested with a kernel that supported them all).
*
+ * @quiet_access_fs and @quiet_access_net are bitmasks of actions for which a
+ * denial by this layer will not trigger a log if the corresponding object (or
+ * its children, for filesystem rules) is marked with the "quiet" bit via
+ * %LANDLOCK_ADD_RULE_QUIET, even if logging would normally take place per
+ * landlock_restrict_self() flags. @quiet_scoped is similar, except that it
+ * does not require marking any objects as quiet - if the ruleset is created
+ * with any bits set in @quiet_scoped, then denial of such scoped resources will
+ * not trigger any log. These 3 fields are available since Landlock ABI version
+ * 10.
+ *
+ * @quiet_access_fs, @quiet_access_net and @quiet_scoped must be a subset of
+ * @handled_access_fs, @handled_access_net and @scoped respectively.
+ *
* This structure can grow in future Landlock versions.
*/
struct landlock_ruleset_attr {
* resources (e.g. IPCs).
*/
__u64 scoped;
+ /**
+ * @quiet_access_fs: Bitmask of filesystem actions which should not be
+ * logged if per-object quiet flag is set.
+ */
+ __u64 quiet_access_fs;
+ /**
+ * @quiet_access_net: Bitmask of network actions which should not be
+ * logged if per-object quiet flag is set.
+ */
+ __u64 quiet_access_net;
+ /**
+ * @quiet_scoped: Bitmask of scoped actions which should not be logged.
+ */
+ __u64 quiet_scoped;
};
/**
#define LANDLOCK_CREATE_RULESET_ERRATA (1U << 1)
/* clang-format on */
+/**
+ * DOC: landlock_add_rule_flags
+ *
+ * **Flags**
+ *
+ * %LANDLOCK_ADD_RULE_QUIET
+ * Together with the quiet_* fields in struct landlock_ruleset_attr,
+ * this flag controls whether Landlock will log audit messages when
+ * access to the objects covered by this rule is denied by this layer.
+ *
+ * If logging is enabled, when Landlock denies an access, it will
+ * suppress the log if all of the following are true:
+ *
+ * - this layer is the innermost layer that denied the access;
+ * - all accesses denied by this layer are part of the quiet_* fields
+ * in the related struct landlock_ruleset_attr;
+ * - the object (or one of its parents, for filesystem rules) is
+ * marked as "quiet" via %LANDLOCK_ADD_RULE_QUIET.
+ *
+ * Because logging is only suppressed by a layer if the layer denies
+ * access, a sandboxed program cannot use this flag to "hide" access
+ * denials, without denying itself the access in the first place.
+ *
+ * The effect of this flag does not depend on the value of
+ * allowed_access in the passed in rule_attr. When this flag is
+ * present, the caller is also allowed to pass in an empty
+ * allowed_access.
+ */
+
+/* clang-format off */
+#define LANDLOCK_ADD_RULE_QUIET (1U << 0)
+/* clang-format on */
+
/**
* DOC: landlock_restrict_self_flags
*
* %LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON. Set to false by default.
*/
log_new_exec : 1;
+ /**
+ * @quiet_masks: Bitmasks of access that should be quieted (i.e. not
+ * logged) if the related object is marked as quiet.
+ */
+ struct access_masks quiet_masks;
#endif /* CONFIG_AUDIT */
};
*/
int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
const struct path *const path,
- access_mask_t access_rights)
+ access_mask_t access_rights, const u32 flags)
{
int err;
struct landlock_id id = {
if (IS_ERR(id.key.object))
return PTR_ERR(id.key.object);
mutex_lock(&ruleset->lock);
- err = landlock_insert_rule(ruleset, id, access_rights);
+ err = landlock_insert_rule(ruleset, id, access_rights, flags);
mutex_unlock(&ruleset->lock);
/*
* No need to check for an error because landlock_insert_rule()
int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
const struct path *const path,
- access_mask_t access_hierarchy);
+ access_mask_t access_hierarchy, const u32 flags);
#endif /* _SECURITY_LANDLOCK_FS_H */
#include "ruleset.h"
int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
- const u16 port, access_mask_t access_rights)
+ const u16 port, access_mask_t access_rights,
+ const u32 flags)
{
int err;
const struct landlock_id id = {
~landlock_get_net_access_mask(ruleset, 0);
mutex_lock(&ruleset->lock);
- err = landlock_insert_rule(ruleset, id, access_rights);
+ err = landlock_insert_rule(ruleset, id, access_rights, flags);
mutex_unlock(&ruleset->lock);
return err;
__init void landlock_add_net_hooks(void);
int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
- const u16 port, access_mask_t access_rights);
+ const u16 port, access_mask_t access_rights,
+ const u32 flags);
#else /* IS_ENABLED(CONFIG_INET) */
static inline void landlock_add_net_hooks(void)
{
static inline int
landlock_append_net_rule(struct landlock_ruleset *const ruleset, const u16 port,
- access_mask_t access_rights)
+ access_mask_t access_rights, const u32 flags)
{
return -EAFNOSUPPORT;
}
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>
+#include <uapi/linux/landlock.h>
#include "access.h"
#include "domain.h"
if (WARN_ON_ONCE(this->layers[0].level != 0))
return -EINVAL;
this->layers[0].access |= (*layers)[0].access;
+ this->layers[0].flags.quiet |= (*layers)[0].flags.quiet;
return 0;
}
/* @ruleset must be locked by the caller. */
int landlock_insert_rule(struct landlock_ruleset *const ruleset,
const struct landlock_id id,
- const access_mask_t access)
+ const access_mask_t access, const u32 flags)
{
struct landlock_layer layers[] = { {
.access = access,
/* When @level is zero, insert_rule() extends @ruleset. */
.level = 0,
+ .flags = {
+ .quiet = !!(flags & LANDLOCK_ADD_RULE_QUIET),
+ },
} };
build_check_layer();
return -EINVAL;
layers[0].access = walker_rule->layers[0].access;
+ layers[0].flags = walker_rule->layers[0].flags;
err = insert_rule(dst, id, &layers, ARRAY_SIZE(layers));
if (err)
if (err)
return ERR_PTR(err);
+#ifdef CONFIG_AUDIT
+ new_dom->hierarchy->quiet_masks = ruleset->quiet_masks;
+#endif /* CONFIG_AUDIT */
+
return no_free_ptr(new_dom);
}
* @work_free: Enables to free a ruleset within a lockless
* section. This is only used by
* landlock_put_ruleset_deferred() when @usage reaches zero.
- * The fields @lock, @usage, @num_rules, @num_layers and
- * @access_masks are then unused.
+ * The fields @lock, @usage, @num_rules, @num_layers,
+ * @quiet_masks and @access_masks are then unused.
*/
struct work_struct work_free;
struct {
* non-merged ruleset (i.e. not a domain).
*/
u32 num_layers;
+ /**
+ * @quiet_masks: Stores the quiet flags for an unmerged
+ * ruleset. For a merged domain, this is stored in each
+ * layer's struct landlock_hierarchy instead.
+ */
+ struct access_masks quiet_masks;
/**
* @access_masks: Contains the subset of filesystem and
* network actions that are restricted by a ruleset.
int landlock_insert_rule(struct landlock_ruleset *const ruleset,
const struct landlock_id id,
- const access_mask_t access);
+ const access_mask_t access, const u32 flags);
struct landlock_ruleset *
landlock_merge_ruleset(struct landlock_ruleset *const parent,
ruleset_size = sizeof(ruleset_attr.handled_access_fs);
ruleset_size += sizeof(ruleset_attr.handled_access_net);
ruleset_size += sizeof(ruleset_attr.scoped);
+ ruleset_size += sizeof(ruleset_attr.quiet_access_fs);
+ ruleset_size += sizeof(ruleset_attr.quiet_access_net);
+ ruleset_size += sizeof(ruleset_attr.quiet_scoped);
BUILD_BUG_ON(sizeof(ruleset_attr) != ruleset_size);
- BUILD_BUG_ON(sizeof(ruleset_attr) != 24);
+ BUILD_BUG_ON(sizeof(ruleset_attr) != 48);
path_beneath_size = sizeof(path_beneath_attr.allowed_access);
path_beneath_size += sizeof(path_beneath_attr.parent_fd);
* - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
* - %EINVAL: unknown @flags, or unknown access, or unknown scope, or too small
* @size;
+ * - %EINVAL: quiet_access_fs, quiet_access_net, or quiet_scoped is not a
+ * subset of the corresponding handled_access_fs, handled_access_net, or
+ * scoped;
* - %E2BIG: @attr or @size inconsistencies;
* - %EFAULT: @attr or @size inconsistencies;
* - %ENOMSG: empty &landlock_ruleset_attr.handled_access_fs.
if ((ruleset_attr.scoped | LANDLOCK_MASK_SCOPE) != LANDLOCK_MASK_SCOPE)
return -EINVAL;
+ /*
+ * Check that quiet masks are subsets of the respective handled masks.
+ * Because of the checks above this is sufficient to also ensure that
+ * the quiet masks are valid access masks.
+ */
+ if ((ruleset_attr.quiet_access_fs | ruleset_attr.handled_access_fs) !=
+ ruleset_attr.handled_access_fs)
+ return -EINVAL;
+ if ((ruleset_attr.quiet_access_net | ruleset_attr.handled_access_net) !=
+ ruleset_attr.handled_access_net)
+ return -EINVAL;
+ if ((ruleset_attr.quiet_scoped | ruleset_attr.scoped) !=
+ ruleset_attr.scoped)
+ return -EINVAL;
+
/* Checks arguments and transforms to kernel struct. */
ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs,
ruleset_attr.handled_access_net,
if (IS_ERR(ruleset))
return PTR_ERR(ruleset);
+ ruleset->quiet_masks.fs = ruleset_attr.quiet_access_fs;
+ ruleset->quiet_masks.net = ruleset_attr.quiet_access_net;
+ ruleset->quiet_masks.scope = ruleset_attr.quiet_scoped;
+
/* Creates anonymous FD referring to the ruleset. */
ruleset_fd = anon_inode_getfd("[landlock-ruleset]", &ruleset_fops,
ruleset, O_RDWR | O_CLOEXEC);
}
static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
- const void __user *const rule_attr)
+ const void __user *const rule_attr, u32 flags)
{
struct landlock_path_beneath_attr path_beneath_attr;
struct path path;
/*
* Informs about useless rule: empty allowed_access (i.e. deny rules)
- * are ignored in path walks.
+ * are ignored in path walks. However, the rule is not useless if it is
+ * there to hold a quiet flag.
*/
- if (!path_beneath_attr.allowed_access)
+ if (!flags && !path_beneath_attr.allowed_access)
return -ENOMSG;
/* Checks that allowed_access matches the @ruleset constraints. */
if ((path_beneath_attr.allowed_access | mask) != mask)
return -EINVAL;
+ /* Checks for useless quiet flag. */
+ if (flags & LANDLOCK_ADD_RULE_QUIET && !ruleset->quiet_masks.fs)
+ return -EINVAL;
+
/* Gets and checks the new rule. */
err = get_path_from_fd(path_beneath_attr.parent_fd, &path);
if (err)
/* Imports the new rule. */
err = landlock_append_fs_rule(ruleset, &path,
- path_beneath_attr.allowed_access);
+ path_beneath_attr.allowed_access, flags);
path_put(&path);
return err;
}
static int add_rule_net_port(struct landlock_ruleset *ruleset,
- const void __user *const rule_attr)
+ const void __user *const rule_attr, u32 flags)
{
struct landlock_net_port_attr net_port_attr;
int res;
/*
* Informs about useless rule: empty allowed_access (i.e. deny rules)
- * are ignored by network actions.
+ * are ignored by network actions. However, the rule is not useless if
+ * it is there to hold a quiet flag.
*/
- if (!net_port_attr.allowed_access)
+ if (!flags && !net_port_attr.allowed_access)
return -ENOMSG;
/* Checks that allowed_access matches the @ruleset constraints. */
if ((net_port_attr.allowed_access | mask) != mask)
return -EINVAL;
+ /* Checks for useless quiet flag. */
+ if (flags & LANDLOCK_ADD_RULE_QUIET && !ruleset->quiet_masks.net)
+ return -EINVAL;
+
/* Denies inserting a rule with port greater than 65535. */
if (net_port_attr.port > U16_MAX)
return -EINVAL;
/* Imports the new rule. */
return landlock_append_net_rule(ruleset, net_port_attr.port,
- net_port_attr.allowed_access);
+ net_port_attr.allowed_access, flags);
}
/**
* @rule_type: Identify the structure type pointed to by @rule_attr:
* %LANDLOCK_RULE_PATH_BENEATH or %LANDLOCK_RULE_NET_PORT.
* @rule_attr: Pointer to a rule (matching the @rule_type).
- * @flags: Must be 0.
+ * @flags: Must be 0 or %LANDLOCK_ADD_RULE_QUIET.
*
* This system call enables to define a new rule and add it to an existing
* ruleset.
* - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
* - %EAFNOSUPPORT: @rule_type is %LANDLOCK_RULE_NET_PORT but TCP/IP is not
* supported by the running kernel;
- * - %EINVAL: @flags is not 0;
+ * - %EINVAL: @flags is not valid;
* - %EINVAL: The rule accesses are inconsistent (i.e.
* &landlock_path_beneath_attr.allowed_access or
* &landlock_net_port_attr.allowed_access is not a subset of the ruleset
* handled accesses)
* - %EINVAL: &landlock_net_port_attr.port is greater than 65535;
+ * - %EINVAL: LANDLOCK_ADD_RULE_QUIET is passed but the ruleset has no
+ * quiet access bits set for the corresponding rule type.
* - %ENOMSG: Empty accesses (e.g. &landlock_path_beneath_attr.allowed_access is
- * 0);
+ * 0) and no flags;
* - %EBADF: @ruleset_fd is not a file descriptor for the current thread, or a
* member of @rule_attr is not a file descriptor as expected;
* - %EBADFD: @ruleset_fd is not a ruleset file descriptor, or a member of
* @rule_attr is not the expected file descriptor type;
* - %EPERM: @ruleset_fd has no write access to the underlying ruleset;
* - %EFAULT: @rule_attr was not a valid address.
+ *
+ * .. kernel-doc:: include/uapi/linux/landlock.h
+ * :identifiers: landlock_add_rule_flags
*/
SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
const enum landlock_rule_type, rule_type,
if (!is_initialized())
return -EOPNOTSUPP;
- /* No flag for now. */
- if (flags)
+ if (flags && flags != LANDLOCK_ADD_RULE_QUIET)
return -EINVAL;
/* Gets and checks the ruleset. */
switch (rule_type) {
case LANDLOCK_RULE_PATH_BENEATH:
- return add_rule_path_beneath(ruleset, rule_attr);
+ return add_rule_path_beneath(ruleset, rule_attr, flags);
case LANDLOCK_RULE_NET_PORT:
- return add_rule_net_port(ruleset, rule_attr);
+ return add_rule_net_port(ruleset, rule_attr, flags);
default:
return -EINVAL;
}
ASSERT_LE(0, ruleset_fd);
/* Checks invalid flags. */
- ASSERT_EQ(-1, landlock_add_rule(-1, 0, NULL, 1));
+ ASSERT_EQ(-1, landlock_add_rule(-1, 0, NULL, 100));
ASSERT_EQ(EINVAL, errno);
/* Checks invalid ruleset FD. */
projects / thirdparty / kernel / linux.git / commitdiff
