[RFC PATCH v2 01/12] landlock: Support socket access-control
Mikhail Ivanov
ivanov.mikhail1 at huawei-partners.com
Fri May 24 09:30:04 UTC 2024
* Add new landlock rule type that corresponds to the restriction of
socket protocols. This is represented as an landlock_socket_attr
structure. Protocol allowed by landlock must be described by
a family-type pair (see socket(2)).
* Support socket rule storage in landlock ruleset.
* Add flag LANDLOCK_ACCESS_SOCKET_CREATE that will provide the
ability to control socket creation.
* Add socket.c file that will contain socket rules management and hooks.
Implement helper pack_socket_key() to convert 32-bit family and type
values into uintptr_t. This is possible due to the fact that these
values are limited to AF_MAX (=46), SOCK_MAX (=11) constants. Assumption
is checked in build-time by the helper.
* Support socket rules in landlock syscalls. Change ABI version to 6.
Closes: https://github.com/landlock-lsm/linux/issues/6
Signed-off-by: Mikhail Ivanov <ivanov.mikhail1 at huawei-partners.com>
---
Changes since v1:
* Reverts landlock_key.data type from u64 to uinptr_t.
* Adds helper to pack domain and type values into uintptr_t.
* Denies inserting socket rule with invalid family and type.
* Renames 'domain' to 'family' in landlock_socket_attr.
* Updates ABI version to 6 since ioctl patches changed it to 5.
* Formats code with clang-format.
* Minor fixes.
---
include/uapi/linux/landlock.h | 53 +++++++++++++++-
security/landlock/Makefile | 2 +-
security/landlock/limits.h | 5 ++
security/landlock/ruleset.c | 37 ++++++++++-
security/landlock/ruleset.h | 41 +++++++++++-
security/landlock/socket.c | 60 ++++++++++++++++++
security/landlock/socket.h | 17 +++++
security/landlock/syscalls.c | 66 ++++++++++++++++++--
tools/testing/selftests/landlock/base_test.c | 2 +-
9 files changed, 272 insertions(+), 11 deletions(-)
create mode 100644 security/landlock/socket.c
create mode 100644 security/landlock/socket.h
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index 68625e728f43..a25ba5983dfb 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -37,6 +37,13 @@ struct landlock_ruleset_attr {
* rule explicitly allow them.
*/
__u64 handled_access_net;
+
+ /**
+ * @handled_access_socket: Bitmask of actions (cf. `Socket flags`_)
+ * that is handled by this ruleset and should then be forbidden if no
+ * rule explicitly allow them.
+ */
+ __u64 handled_access_socket;
};
/*
@@ -65,6 +72,11 @@ enum landlock_rule_type {
* landlock_net_port_attr .
*/
LANDLOCK_RULE_NET_PORT,
+ /**
+ * @LANDLOCK_RULE_SOCKET: Type of a &struct
+ * landlock_socket_attr .
+ */
+ LANDLOCK_RULE_SOCKET,
};
/**
@@ -115,6 +127,28 @@ struct landlock_net_port_attr {
__u64 port;
};
+/**
+ * struct landlock_socket_attr - Socket definition
+ *
+ * Argument of sys_landlock_add_rule().
+ */
+struct landlock_socket_attr {
+ /**
+ * @allowed_access: Bitmask of allowed access for a socket
+ * (cf. `Socket flags`_).
+ */
+ __u64 allowed_access;
+ /**
+ * @family: Protocol family used for communication
+ * (same as domain in socket(2)).
+ */
+ int family;
+ /**
+ * @type: Socket type (see socket(2)).
+ */
+ int type;
+};
+
/**
* DOC: fs_access
*
@@ -251,7 +285,7 @@ struct landlock_net_port_attr {
* DOC: net_access
*
* Network flags
- * ~~~~~~~~~~~~~~~~
+ * ~~~~~~~~~~~~~
*
* These flags enable to restrict a sandboxed process to a set of network
* actions. This is supported since the Landlock ABI version 4.
@@ -266,4 +300,21 @@ struct landlock_net_port_attr {
#define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0)
#define LANDLOCK_ACCESS_NET_CONNECT_TCP (1ULL << 1)
/* clang-format on */
+
+/**
+ * DOC: socket_access
+ *
+ * Socket flags
+ * ~~~~~~~~~~~~
+ *
+ * These flags enable to restrict a sanboxed process to a set of socket
+ * protocols. This is supported since the Landlock ABI version 6.
+ *
+ * The following access rights apply only to sockets:
+ *
+ * - %LANDLOCK_ACCESS_SOCKET_CREATE: Create a socket.
+ */
+/* clang-format off */
+#define LANDLOCK_ACCESS_SOCKET_CREATE (1ULL << 0)
+/* clang-format on */
#endif /* _UAPI_LINUX_LANDLOCK_H */
diff --git a/security/landlock/Makefile b/security/landlock/Makefile
index b4538b7cf7d2..ff1dd98f6a1b 100644
--- a/security/landlock/Makefile
+++ b/security/landlock/Makefile
@@ -1,6 +1,6 @@
obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
landlock-y := setup.o syscalls.o object.o ruleset.o \
- cred.o task.o fs.o
+ cred.o task.o fs.o socket.o
landlock-$(CONFIG_INET) += net.o
diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index 20fdb5ff3514..448b4d596783 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h
@@ -28,6 +28,11 @@
#define LANDLOCK_NUM_ACCESS_NET __const_hweight64(LANDLOCK_MASK_ACCESS_NET)
#define LANDLOCK_SHIFT_ACCESS_NET LANDLOCK_NUM_ACCESS_FS
+#define LANDLOCK_LAST_ACCESS_SOCKET LANDLOCK_ACCESS_SOCKET_CREATE
+#define LANDLOCK_MASK_ACCESS_SOCKET ((LANDLOCK_LAST_ACCESS_SOCKET << 1) - 1)
+#define LANDLOCK_NUM_ACCESS_SOCKET __const_hweight64(LANDLOCK_MASK_ACCESS_SOCKET)
+#define LANDLOCK_SHIFT_ACCESS_SOCKET LANDLOCK_NUM_ACCESS_SOCKET
+
/* clang-format on */
#endif /* _SECURITY_LANDLOCK_LIMITS_H */
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index e0a5fbf9201a..c782f7cd313d 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -40,6 +40,7 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
#if IS_ENABLED(CONFIG_INET)
new_ruleset->root_net_port = RB_ROOT;
#endif /* IS_ENABLED(CONFIG_INET) */
+ new_ruleset->root_socket = RB_ROOT;
new_ruleset->num_layers = num_layers;
/*
@@ -52,12 +53,13 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
struct landlock_ruleset *
landlock_create_ruleset(const access_mask_t fs_access_mask,
- const access_mask_t net_access_mask)
+ const access_mask_t net_access_mask,
+ const access_mask_t socket_access_mask)
{
struct landlock_ruleset *new_ruleset;
/* Informs about useless ruleset. */
- if (!fs_access_mask && !net_access_mask)
+ if (!fs_access_mask && !net_access_mask && !socket_access_mask)
return ERR_PTR(-ENOMSG);
new_ruleset = create_ruleset(1);
if (IS_ERR(new_ruleset))
@@ -66,6 +68,9 @@ landlock_create_ruleset(const access_mask_t 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);
+ if (socket_access_mask)
+ landlock_add_socket_access_mask(new_ruleset, socket_access_mask,
+ 0);
return new_ruleset;
}
@@ -89,6 +94,9 @@ static bool is_object_pointer(const enum landlock_key_type key_type)
return false;
#endif /* IS_ENABLED(CONFIG_INET) */
+ case LANDLOCK_KEY_SOCKET:
+ return false;
+
default:
WARN_ON_ONCE(1);
return false;
@@ -146,6 +154,9 @@ static struct rb_root *get_root(struct landlock_ruleset *const ruleset,
return &ruleset->root_net_port;
#endif /* IS_ENABLED(CONFIG_INET) */
+ case LANDLOCK_KEY_SOCKET:
+ return &ruleset->root_socket;
+
default:
WARN_ON_ONCE(1);
return ERR_PTR(-EINVAL);
@@ -175,7 +186,9 @@ static void build_check_ruleset(void)
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_NET << LANDLOCK_SHIFT_ACCESS_NET)));
+ (LANDLOCK_MASK_ACCESS_NET << LANDLOCK_SHIFT_ACCESS_NET) |
+ (LANDLOCK_MASK_ACCESS_SOCKET
+ << LANDLOCK_SHIFT_ACCESS_SOCKET)));
}
/**
@@ -399,6 +412,11 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
goto out_unlock;
#endif /* IS_ENABLED(CONFIG_INET) */
+ /* Merges the @src socket tree. */
+ err = merge_tree(dst, src, LANDLOCK_KEY_SOCKET);
+ if (err)
+ goto out_unlock;
+
out_unlock:
mutex_unlock(&src->lock);
mutex_unlock(&dst->lock);
@@ -462,6 +480,11 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
goto out_unlock;
#endif /* IS_ENABLED(CONFIG_INET) */
+ /* Copies the @parent socket tree. */
+ err = inherit_tree(parent, child, LANDLOCK_KEY_SOCKET);
+ if (err)
+ goto out_unlock;
+
if (WARN_ON_ONCE(child->num_layers <= parent->num_layers)) {
err = -EINVAL;
goto out_unlock;
@@ -498,6 +521,10 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
free_rule(freeme, LANDLOCK_KEY_NET_PORT);
#endif /* IS_ENABLED(CONFIG_INET) */
+ rbtree_postorder_for_each_entry_safe(freeme, next,
+ &ruleset->root_socket, node)
+ free_rule(freeme, LANDLOCK_KEY_SOCKET);
+
put_hierarchy(ruleset->hierarchy);
kfree(ruleset);
}
@@ -708,6 +735,10 @@ landlock_init_layer_masks(const struct landlock_ruleset *const domain,
break;
#endif /* IS_ENABLED(CONFIG_INET) */
+ case LANDLOCK_KEY_SOCKET:
+ get_access_mask = landlock_get_socket_access_mask;
+ num_access = LANDLOCK_NUM_ACCESS_SOCKET;
+ break;
default:
WARN_ON_ONCE(1);
return 0;
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index c7f1526784fd..a9773efd529b 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -92,6 +92,12 @@ enum landlock_key_type {
* node keys.
*/
LANDLOCK_KEY_NET_PORT,
+
+ /**
+ * @LANDLOCK_KEY_SOCKET: Type of &landlock_ruleset.root_socket's
+ * node keys.
+ */
+ LANDLOCK_KEY_SOCKET,
};
/**
@@ -177,6 +183,15 @@ struct landlock_ruleset {
struct rb_root root_net_port;
#endif /* IS_ENABLED(CONFIG_INET) */
+ /**
+ * @root_socket: Root of a red-black tree containing &struct
+ * landlock_rule nodes with socket type, described by (family, type)
+ * pair (see socket(2)). 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_socket;
+
/**
* @hierarchy: Enables hierarchy identification even when a parent
* domain vanishes. This is needed for the ptrace protection.
@@ -233,7 +248,8 @@ struct landlock_ruleset {
struct landlock_ruleset *
landlock_create_ruleset(const access_mask_t access_mask_fs,
- const access_mask_t access_mask_net);
+ const access_mask_t access_mask_net,
+ const access_mask_t access_mask_socket);
void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);
@@ -282,6 +298,20 @@ landlock_add_net_access_mask(struct landlock_ruleset *const ruleset,
(net_mask << LANDLOCK_SHIFT_ACCESS_NET);
}
+static inline void
+landlock_add_socket_access_mask(struct landlock_ruleset *const ruleset,
+ const access_mask_t socket_access_mask,
+ const u16 layer_level)
+{
+ access_mask_t socket_mask = socket_access_mask &
+ LANDLOCK_MASK_ACCESS_SOCKET;
+
+ /* Should already be checked in sys_landlock_create_ruleset(). */
+ WARN_ON_ONCE(socket_access_mask != socket_mask);
+ ruleset->access_masks[layer_level] |=
+ (socket_mask << LANDLOCK_SHIFT_ACCESS_SOCKET);
+}
+
static inline access_mask_t
landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset,
const u16 layer_level)
@@ -309,6 +339,15 @@ landlock_get_net_access_mask(const struct landlock_ruleset *const ruleset,
LANDLOCK_MASK_ACCESS_NET;
}
+static inline access_mask_t
+landlock_get_socket_access_mask(const struct landlock_ruleset *const ruleset,
+ const u16 layer_level)
+{
+ return (ruleset->access_masks[layer_level] >>
+ LANDLOCK_SHIFT_ACCESS_SOCKET) &
+ LANDLOCK_MASK_ACCESS_SOCKET;
+}
+
bool landlock_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/socket.c b/security/landlock/socket.c
new file mode 100644
index 000000000000..1249a4a36503
--- /dev/null
+++ b/security/landlock/socket.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - Socket management and hooks
+ *
+ * Copyright © 2024 Huawei Tech. Co., Ltd.
+ */
+
+#include <linux/net.h>
+#include <linux/socket.h>
+#include <linux/stddef.h>
+
+#include "limits.h"
+#include "ruleset.h"
+#include "socket.h"
+
+static uintptr_t pack_socket_key(const int family, const int type)
+{
+ union {
+ struct {
+ unsigned short family, type;
+ } __packed data;
+ uintptr_t packed;
+ } socket_key;
+
+ /* Checks that all supported socket families and types can be stored in socket_key. */
+ BUILD_BUG_ON(AF_MAX > (typeof(socket_key.data.family))~0);
+ BUILD_BUG_ON(SOCK_MAX > (typeof(socket_key.data.type))~0);
+
+ /* Checks that socket_key can be stored in landlock_key. */
+ BUILD_BUG_ON(sizeof(socket_key.data) > sizeof(socket_key.packed));
+ BUILD_BUG_ON(sizeof(socket_key.packed) >
+ sizeof_field(union landlock_key, data));
+
+ socket_key.data.family = (unsigned short)family;
+ socket_key.data.type = (unsigned short)type;
+
+ return socket_key.packed;
+}
+
+int landlock_append_socket_rule(struct landlock_ruleset *const ruleset,
+ const int family, const int type,
+ access_mask_t access_rights)
+{
+ int err;
+
+ const struct landlock_id id = {
+ .key.data = pack_socket_key(family, type),
+ .type = LANDLOCK_KEY_SOCKET,
+ };
+
+ /* Transforms relative access rights to absolute ones. */
+ access_rights |= LANDLOCK_MASK_ACCESS_SOCKET &
+ ~landlock_get_socket_access_mask(ruleset, 0);
+
+ mutex_lock(&ruleset->lock);
+ err = landlock_insert_rule(ruleset, id, access_rights);
+ mutex_unlock(&ruleset->lock);
+
+ return err;
+}
diff --git a/security/landlock/socket.h b/security/landlock/socket.h
new file mode 100644
index 000000000000..8519357f1c39
--- /dev/null
+++ b/security/landlock/socket.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Landlock LSM - Socket management and hooks
+ *
+ * Copyright © 2024 Huawei Tech. Co., Ltd.
+ */
+
+#ifndef _SECURITY_LANDLOCK_SOCKET_H
+#define _SECURITY_LANDLOCK_SOCKET_H
+
+#include "ruleset.h"
+
+int landlock_append_socket_rule(struct landlock_ruleset *const ruleset,
+ const int family, const int type,
+ access_mask_t access_rights);
+
+#endif /* _SECURITY_LANDLOCK_SOCKET_H */
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 03b470f5a85a..30c771f5e74f 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -24,12 +24,14 @@
#include <linux/syscalls.h>
#include <linux/types.h>
#include <linux/uaccess.h>
+#include <linux/net.h>
#include <uapi/linux/landlock.h>
#include "cred.h"
#include "fs.h"
#include "limits.h"
#include "net.h"
+#include "socket.h"
#include "ruleset.h"
#include "setup.h"
@@ -88,7 +90,8 @@ static void build_check_abi(void)
struct landlock_ruleset_attr ruleset_attr;
struct landlock_path_beneath_attr path_beneath_attr;
struct landlock_net_port_attr net_port_attr;
- size_t ruleset_size, path_beneath_size, net_port_size;
+ struct landlock_socket_attr socket_attr;
+ size_t ruleset_size, path_beneath_size, net_port_size, socket_size;
/*
* For each user space ABI structures, first checks that there is no
@@ -97,8 +100,9 @@ static void build_check_abi(void)
*/
ruleset_size = sizeof(ruleset_attr.handled_access_fs);
ruleset_size += sizeof(ruleset_attr.handled_access_net);
+ ruleset_size += sizeof(ruleset_attr.handled_access_socket);
BUILD_BUG_ON(sizeof(ruleset_attr) != ruleset_size);
- BUILD_BUG_ON(sizeof(ruleset_attr) != 16);
+ BUILD_BUG_ON(sizeof(ruleset_attr) != 24);
path_beneath_size = sizeof(path_beneath_attr.allowed_access);
path_beneath_size += sizeof(path_beneath_attr.parent_fd);
@@ -109,6 +113,12 @@ static void build_check_abi(void)
net_port_size += sizeof(net_port_attr.port);
BUILD_BUG_ON(sizeof(net_port_attr) != net_port_size);
BUILD_BUG_ON(sizeof(net_port_attr) != 16);
+
+ socket_size = sizeof(socket_attr.allowed_access);
+ socket_size += sizeof(socket_attr.family);
+ socket_size += sizeof(socket_attr.type);
+ BUILD_BUG_ON(sizeof(socket_attr) != socket_size);
+ BUILD_BUG_ON(sizeof(socket_attr) != 16);
}
/* Ruleset handling */
@@ -149,7 +159,7 @@ static const struct file_operations ruleset_fops = {
.write = fop_dummy_write,
};
-#define LANDLOCK_ABI_VERSION 5
+#define LANDLOCK_ABI_VERSION 6
/**
* sys_landlock_create_ruleset - Create a new ruleset
@@ -213,9 +223,15 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
LANDLOCK_MASK_ACCESS_NET)
return -EINVAL;
+ /* Checks socket content (and 32-bits cast). */
+ if ((ruleset_attr.handled_access_socket |
+ LANDLOCK_MASK_ACCESS_SOCKET) != LANDLOCK_MASK_ACCESS_SOCKET)
+ return -EINVAL;
+
/* Checks arguments and transforms to kernel struct. */
ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs,
- ruleset_attr.handled_access_net);
+ ruleset_attr.handled_access_net,
+ ruleset_attr.handled_access_socket);
if (IS_ERR(ruleset))
return PTR_ERR(ruleset);
@@ -371,6 +387,45 @@ static int add_rule_net_port(struct landlock_ruleset *ruleset,
net_port_attr.allowed_access);
}
+static int add_rule_socket(struct landlock_ruleset *ruleset,
+ const void __user *const rule_attr)
+{
+ struct landlock_socket_attr socket_attr;
+ int family, type;
+ int res;
+ access_mask_t mask;
+
+ /* Copies raw user space buffer. */
+ res = copy_from_user(&socket_attr, rule_attr, sizeof(socket_attr));
+ if (res)
+ return -EFAULT;
+
+ /*
+ * Informs about useless rule: empty allowed_access (i.e. deny rules)
+ * are ignored by socket actions.
+ */
+ if (!socket_attr.allowed_access)
+ return -ENOMSG;
+
+ /* Checks that allowed_access matches the @ruleset constraints. */
+ mask = landlock_get_socket_access_mask(ruleset, 0);
+ if ((socket_attr.allowed_access | mask) != mask)
+ return -EINVAL;
+
+ family = socket_attr.family;
+ type = socket_attr.type;
+
+ /* Denies inserting a rule with unsupported socket family and type. */
+ if (family < 0 || family >= AF_MAX)
+ return -EINVAL;
+ if (type < 0 || type >= SOCK_MAX)
+ return -EINVAL;
+
+ /* Imports the new rule. */
+ return landlock_append_socket_rule(ruleset, family, type,
+ socket_attr.allowed_access);
+}
+
/**
* sys_landlock_add_rule - Add a new rule to a ruleset
*
@@ -429,6 +484,9 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
case LANDLOCK_RULE_NET_PORT:
err = add_rule_net_port(ruleset, rule_attr);
break;
+ case LANDLOCK_RULE_SOCKET:
+ err = add_rule_socket(ruleset, rule_attr);
+ break;
default:
err = -EINVAL;
break;
diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index 3c1e9f35b531..52b00472a487 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(5, landlock_create_ruleset(NULL, 0,
+ ASSERT_EQ(6, landlock_create_ruleset(NULL, 0,
LANDLOCK_CREATE_RULESET_VERSION));
ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,
--
2.34.1
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