[PATCH v8 07/12] landlock: Add network rules support
Konstantin Meskhidze
konstantin.meskhidze at huawei.com
Fri Oct 21 15:26:39 UTC 2022
This commit adds network rules support in internal landlock functions
(presented in ruleset.c) and landlock_create_ruleset syscall.
Refactors user space API to support network actions. Adds new network
access flags, network rule and network attributes. Increments Landlock
ABI version.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze at huawei.com>
---
Changes since v7:
* Squashes commits.
* Increments ABI version to 4.
* Refactors commit message.
* Minor fixes.
Changes since v6:
* Renames landlock_set_net_access_mask() to landlock_add_net_access_mask()
because it OR values.
* Makes landlock_add_net_access_mask() more resilient incorrect values.
* Refactors landlock_get_net_access_mask().
* Renames LANDLOCK_MASK_SHIFT_NET to LANDLOCK_SHIFT_ACCESS_NET and use
LANDLOCK_NUM_ACCESS_FS as value.
* Updates access_masks_t to u32 to support network access actions.
* Refactors landlock internal functions to support network actions with
landlock_key/key_type/id types.
Changes since v5:
* Gets rid of partial revert from landlock_add_rule
syscall.
* Formats code with clang-format-14.
Changes since v4:
* Refactors landlock_create_ruleset() - splits ruleset and
masks checks.
* Refactors landlock_create_ruleset() and landlock mask
setters/getters to support two rule types.
* Refactors landlock_add_rule syscall add_rule_path_beneath
function by factoring out get_ruleset_from_fd() and
landlock_put_ruleset().
Changes since v3:
* Splits commit.
* Adds network rule support for internal landlock functions.
* Adds set_mask and get_mask for network.
* Adds rb_root root_net_port.
---
include/uapi/linux/landlock.h | 49 ++++++++++++++
security/landlock/limits.h | 6 +-
security/landlock/ruleset.c | 55 ++++++++++++++--
security/landlock/ruleset.h | 68 ++++++++++++++++----
security/landlock/syscalls.c | 13 +++-
tools/testing/selftests/landlock/base_test.c | 2 +-
6 files changed, 170 insertions(+), 23 deletions(-)
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index f3223f964691..096b683c6ff3 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -31,6 +31,13 @@ struct landlock_ruleset_attr {
* this access right.
*/
__u64 handled_access_fs;
+
+ /**
+ * @handled_access_net: Bitmask of actions (cf. `Network flags`_)
+ * that is handled by this ruleset and should then be forbidden if no
+ * rule explicitly allow them.
+ */
+ __u64 handled_access_net;
};
/*
@@ -54,6 +61,11 @@ enum landlock_rule_type {
* landlock_path_beneath_attr .
*/
LANDLOCK_RULE_PATH_BENEATH = 1,
+ /**
+ * @LANDLOCK_RULE_NET_SERVICE: Type of a &struct
+ * landlock_net_service_attr .
+ */
+ LANDLOCK_RULE_NET_SERVICE = 2,
};
/**
@@ -79,6 +91,24 @@ struct landlock_path_beneath_attr {
*/
} __attribute__((packed));
+/**
+ * struct landlock_net_service_attr - TCP subnet definition
+ *
+ * Argument of sys_landlock_add_rule().
+ */
+struct landlock_net_service_attr {
+ /**
+ * @allowed_access: Bitmask of allowed access network for services
+ * (cf. `Network flags`_).
+ */
+ __u64 allowed_access;
+ /**
+ * @port: Network port.
+ */
+ __u16 port;
+
+} __attribute__((packed));
+
/**
* DOC: fs_access
*
@@ -173,4 +203,23 @@ struct landlock_path_beneath_attr {
#define LANDLOCK_ACCESS_FS_TRUNCATE (1ULL << 14)
/* clang-format on */
+/**
+ * DOC: net_access
+ *
+ * Network flags
+ * ~~~~~~~~~~~~~~~~
+ *
+ * These flags enable to restrict a sandboxed process to a set of network
+ * actions.
+ *
+ * TCP sockets with allowed actions:
+ *
+ * - %LANDLOCK_ACCESS_NET_BIND_TCP: Bind a TCP socket to a local port.
+ * - %LANDLOCK_ACCESS_NET_CONNECT_TCP: Connect an active TCP socket to
+ * a remote port.
+ */
+/* clang-format off */
+#define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0)
+#define LANDLOCK_ACCESS_NET_CONNECT_TCP (1ULL << 1)
+/* clang-format on */
#endif /* _UAPI_LINUX_LANDLOCK_H */
diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index bafb3b8dc677..8a1a6463c64e 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h
@@ -23,6 +23,10 @@
#define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS)
#define LANDLOCK_SHIFT_ACCESS_FS 0
-/* clang-format on */
+#define LANDLOCK_LAST_ACCESS_NET LANDLOCK_ACCESS_NET_CONNECT_TCP
+#define LANDLOCK_MASK_ACCESS_NET ((LANDLOCK_LAST_ACCESS_NET << 1) - 1)
+#define LANDLOCK_NUM_ACCESS_NET __const_hweight64(LANDLOCK_MASK_ACCESS_NET)
+#define LANDLOCK_SHIFT_ACCESS_NET LANDLOCK_NUM_ACCESS_FS
+/* clang-format on */
#endif /* _SECURITY_LANDLOCK_LIMITS_H */
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index c7cf54ba4f6d..9277c1295114 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -36,6 +36,9 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
refcount_set(&new_ruleset->usage, 1);
mutex_init(&new_ruleset->lock);
new_ruleset->root_inode = RB_ROOT;
+#if IS_ENABLED(CONFIG_INET)
+ new_ruleset->root_net_port = RB_ROOT;
+#endif /* IS_ENABLED(CONFIG_INET) */
new_ruleset->num_layers = num_layers;
/*
* hierarchy = NULL
@@ -46,16 +49,21 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
}
struct landlock_ruleset *
-landlock_create_ruleset(const access_mask_t fs_access_mask)
+landlock_create_ruleset(const access_mask_t fs_access_mask,
+ const access_mask_t net_access_mask)
{
struct landlock_ruleset *new_ruleset;
/* Informs about useless ruleset. */
- if (!fs_access_mask)
+ if (!fs_access_mask && !net_access_mask)
return ERR_PTR(-ENOMSG);
new_ruleset = create_ruleset(1);
- if (!IS_ERR(new_ruleset))
+ if (IS_ERR(new_ruleset))
+ return new_ruleset;
+ if (fs_access_mask)
landlock_add_fs_access_mask(new_ruleset, fs_access_mask, 0);
+ if (net_access_mask)
+ landlock_add_net_access_mask(new_ruleset, net_access_mask, 0);
return new_ruleset;
}
@@ -73,6 +81,10 @@ static inline bool is_object_pointer(const enum landlock_key_type key_type)
switch (key_type) {
case LANDLOCK_KEY_INODE:
return true;
+#if IS_ENABLED(CONFIG_INET)
+ case LANDLOCK_KEY_NET_PORT:
+ return false;
+#endif /* IS_ENABLED(CONFIG_INET) */
}
WARN_ON_ONCE(1);
return false;
@@ -126,6 +138,11 @@ static inline struct rb_root *get_root(struct landlock_ruleset *const ruleset,
case LANDLOCK_KEY_INODE:
root = &ruleset->root_inode;
break;
+#if IS_ENABLED(CONFIG_INET)
+ case LANDLOCK_KEY_NET_PORT:
+ root = &ruleset->root_net_port;
+ break;
+#endif /* IS_ENABLED(CONFIG_INET) */
}
if (WARN_ON_ONCE(!root))
return ERR_PTR(-EINVAL);
@@ -154,7 +171,9 @@ static void build_check_ruleset(void)
BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
BUILD_BUG_ON(access_masks <
- (LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS));
+ (LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS) +
+ (LANDLOCK_MASK_ACCESS_NET
+ << LANDLOCK_SHIFT_ACCESS_NET));
}
/**
@@ -370,7 +389,12 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
err = merge_tree(dst, src, LANDLOCK_KEY_INODE);
if (err)
goto out_unlock;
-
+#if IS_ENABLED(CONFIG_INET)
+ /* Merges the @src network port tree. */
+ err = merge_tree(dst, src, LANDLOCK_KEY_NET_PORT);
+ if (err)
+ goto out_unlock;
+#endif /* IS_ENABLED(CONFIG_INET) */
out_unlock:
mutex_unlock(&src->lock);
mutex_unlock(&dst->lock);
@@ -426,7 +450,12 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
err = inherit_tree(parent, child, LANDLOCK_KEY_INODE);
if (err)
goto out_unlock;
-
+#if IS_ENABLED(CONFIG_INET)
+ /* Copies the @parent network port tree. */
+ err = inherit_tree(parent, child, LANDLOCK_KEY_NET_PORT);
+ if (err)
+ goto out_unlock;
+#endif /* IS_ENABLED(CONFIG_INET) */
if (WARN_ON_ONCE(child->num_layers <= parent->num_layers)) {
err = -EINVAL;
goto out_unlock;
@@ -459,6 +488,11 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
node)
free_rule(freeme, LANDLOCK_KEY_INODE);
+#if IS_ENABLED(CONFIG_INET)
+ rbtree_postorder_for_each_entry_safe(freeme, next,
+ &ruleset->root_net_port, node)
+ free_rule(freeme, LANDLOCK_KEY_NET_PORT);
+#endif /* IS_ENABLED(CONFIG_INET) */
put_hierarchy(ruleset->hierarchy);
kfree(ruleset);
}
@@ -637,6 +671,9 @@ get_access_mask_t(const struct landlock_ruleset *const ruleset,
* Populates @layer_masks such that for each access right in @access_request,
* the bits for all the layers are set where this access right is handled.
*
+ * @layer_masks must contain LANDLOCK_NUM_ACCESS_FS or LANDLOCK_NUM_ACCESS_NET
+ * elements according to @key_type.
+ *
* @domain: The domain that defines the current restrictions.
* @access_request: The requested access rights to check.
* @layer_masks: The layer masks to populate.
@@ -659,6 +696,12 @@ access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
get_access_mask = landlock_get_fs_access_mask;
num_access = LANDLOCK_NUM_ACCESS_FS;
break;
+#if IS_ENABLED(CONFIG_INET)
+ case LANDLOCK_KEY_NET_PORT:
+ get_access_mask = landlock_get_net_access_mask;
+ num_access = LANDLOCK_NUM_ACCESS_NET;
+ break;
+#endif /* IS_ENABLED(CONFIG_INET) */
default:
WARN_ON_ONCE(1);
return 0;
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index d9eb79ea9a89..f272d2cd518c 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -19,16 +19,20 @@
#include "limits.h"
#include "object.h"
+/* Rule access mask. */
typedef u16 access_mask_t;
/* Makes sure all filesystem access rights can be stored. */
static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
+/* Makes sure all network access rights can be stored. */
+static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_NET);
/* Makes sure for_each_set_bit() and for_each_clear_bit() calls are OK. */
static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));
/* Ruleset access masks. */
-typedef u16 access_masks_t;
+typedef u32 access_masks_t;
/* Makes sure all ruleset access rights can be stored. */
-static_assert(BITS_PER_TYPE(access_masks_t) >= LANDLOCK_NUM_ACCESS_FS);
+static_assert(BITS_PER_TYPE(access_masks_t) >=
+ LANDLOCK_NUM_ACCESS_FS + LANDLOCK_NUM_ACCESS_NET);
typedef u16 layer_mask_t;
/* Makes sure all layers can be checked. */
@@ -82,6 +86,13 @@ enum landlock_key_type {
* keys.
*/
LANDLOCK_KEY_INODE = 1,
+#if IS_ENABLED(CONFIG_INET)
+ /**
+ * @LANDLOCK_KEY_NET_PORT: Type of &landlock_ruleset.root_net_port's
+ * node keys.
+ */
+ LANDLOCK_KEY_NET_PORT = 2,
+#endif /* IS_ENABLED(CONFIG_INET) */
};
/**
@@ -156,6 +167,15 @@ struct landlock_ruleset {
* reaches zero.
*/
struct rb_root root_inode;
+#if IS_ENABLED(CONFIG_INET)
+ /**
+ * @root_net_port: Root of a red-black tree containing &struct
+ * landlock_rule nodes with network port. Once a ruleset is tied to a
+ * process (i.e. as a domain), this tree is immutable until @usage
+ * reaches zero.
+ */
+ struct rb_root root_net_port;
+#endif /* IS_ENABLED(CONFIG_INET) */
/**
* @hierarchy: Enables hierarchy identification even when a parent
* domain vanishes. This is needed for the ptrace protection.
@@ -166,8 +186,8 @@ struct landlock_ruleset {
* @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,
+ * @net_access_mask and @access_masks are then unused.
*/
struct work_struct work_free;
struct {
@@ -194,13 +214,13 @@ struct landlock_ruleset {
*/
u32 num_layers;
/**
- * @access_masks: Contains the subset of filesystem
- * actions that are restricted by a ruleset. A domain
- * saves all layers of merged rulesets in a stack
- * (FAM), starting from the first layer to the last
- * one. These layers are used when merging rulesets,
- * for user space backward compatibility (i.e.
- * future-proof), and to properly handle merged
+ * @access_masks: Contains the subset of filesystem and
+ * network actions that are restricted by a ruleset.
+ * A domain saves all layers of merged rulesets in a
+ * stack (FAM), starting from the first layer to the
+ * last one. These layers are used when merging
+ * rulesets, for user space backward compatibility
+ * (i.e. future-proof), and to properly handle merged
* rulesets without overlapping access rights. These
* layers are set once and never changed for the
* lifetime of the ruleset.
@@ -211,7 +231,8 @@ struct landlock_ruleset {
};
struct landlock_ruleset *
-landlock_create_ruleset(const access_mask_t access_mask);
+landlock_create_ruleset(const access_mask_t access_mask_fs,
+ const access_mask_t access_mask_net);
void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);
@@ -248,6 +269,20 @@ landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
(fs_mask << LANDLOCK_SHIFT_ACCESS_FS);
}
+static inline void
+landlock_add_net_access_mask(struct landlock_ruleset *const ruleset,
+ const access_mask_t net_access_mask,
+ const u16 layer_level)
+{
+ access_mask_t net_mask = net_access_mask & LANDLOCK_MASK_ACCESS_NET;
+
+ /* Should already be checked in sys_landlock_create_ruleset(). */
+ WARN_ON_ONCE(net_access_mask != net_mask);
+ // TODO: Add tests to check "|=" and not "="
+ ruleset->access_masks[layer_level] |=
+ (net_mask << LANDLOCK_SHIFT_ACCESS_NET);
+}
+
static inline access_mask_t
landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
const u16 layer_level)
@@ -257,6 +292,15 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
LANDLOCK_MASK_ACCESS_FS;
}
+static inline access_mask_t
+landlock_get_net_access_mask(const struct landlock_ruleset *const ruleset,
+ const u16 layer_level)
+{
+ return (ruleset->access_masks[layer_level] >>
+ LANDLOCK_SHIFT_ACCESS_NET) &
+ LANDLOCK_MASK_ACCESS_NET;
+}
+
bool unmask_layers(const struct landlock_rule *const rule,
const access_mask_t access_request,
layer_mask_t (*const layer_masks)[],
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 87389d7bfbf2..c5a6ad4e2fca 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -82,8 +82,9 @@ static void build_check_abi(void)
* struct size.
*/
ruleset_size = sizeof(ruleset_attr.handled_access_fs);
+ ruleset_size += sizeof(ruleset_attr.handled_access_net);
BUILD_BUG_ON(sizeof(ruleset_attr) != ruleset_size);
- BUILD_BUG_ON(sizeof(ruleset_attr) != 8);
+ BUILD_BUG_ON(sizeof(ruleset_attr) != 16);
path_beneath_size = sizeof(path_beneath_attr.allowed_access);
path_beneath_size += sizeof(path_beneath_attr.parent_fd);
@@ -129,7 +130,7 @@ static const struct file_operations ruleset_fops = {
.write = fop_dummy_write,
};
-#define LANDLOCK_ABI_VERSION 3
+#define LANDLOCK_ABI_VERSION 4
/**
* sys_landlock_create_ruleset - Create a new ruleset
@@ -188,8 +189,14 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
LANDLOCK_MASK_ACCESS_FS)
return -EINVAL;
+ /* Checks network content (and 32-bits cast). */
+ if ((ruleset_attr.handled_access_net | LANDLOCK_MASK_ACCESS_NET) !=
+ LANDLOCK_MASK_ACCESS_NET)
+ return -EINVAL;
+
/* Checks arguments and transforms to kernel struct. */
- ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs);
+ ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs,
+ ruleset_attr.handled_access_net);
if (IS_ERR(ruleset))
return PTR_ERR(ruleset);
diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index 792c3f0a59b4..646f778dfb1e 100644
--- a/tools/testing/selftests/landlock/base_test.c
+++ b/tools/testing/selftests/landlock/base_test.c
@@ -75,7 +75,7 @@ TEST(abi_version)
const struct landlock_ruleset_attr ruleset_attr = {
.handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
};
- ASSERT_EQ(3, landlock_create_ruleset(NULL, 0,
+ ASSERT_EQ(4, landlock_create_ruleset(NULL, 0,
LANDLOCK_CREATE_RULESET_VERSION));
ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,
--
2.25.1
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