This commit adds network rules support in the ruleset management
helpers and the landlock_create_ruleset syscall.
Refactor user space API to support network actions. Add new network
access flags, network rule and network attributes. Increment Landlock
ABI version. Expand access_masks_t to u32 to be sure network access
rights can be stored. Implement socket_bind() and socket_connect()
LSM hooks, which enable to restrict TCP socket binding and connection
to specific ports.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx>
---
Changes since v8:
* Squashes commits.
* Refactors commit message.
* Changes UAPI port field to __be16.
* Changes logic of bind/connect hooks with AF_UNSPEC families.
* Adds address length checking.
* Minor fixes.
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/Kconfig | 1 +
security/landlock/Makefile | 2 +
security/landlock/limits.h | 6 +-
security/landlock/net.c | 200 +++++++++++++++++++
security/landlock/net.h | 26 +++
security/landlock/ruleset.c | 52 ++++-
security/landlock/ruleset.h | 63 +++++-
security/landlock/setup.c | 2 +
security/landlock/syscalls.c | 72 ++++++-
tools/testing/selftests/landlock/base_test.c | 2 +-
11 files changed, 452 insertions(+), 23 deletions(-)
create mode 100644 security/landlock/net.c
create mode 100644 security/landlock/net.h
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index f3223f964691..ae11c663c975 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.
+ */
+ __be16 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/Kconfig b/security/landlock/Kconfig
index 8e33c4e8ffb8..10c099097533 100644
--- a/security/landlock/Kconfig
+++ b/security/landlock/Kconfig
@@ -3,6 +3,7 @@
config SECURITY_LANDLOCK
bool "Landlock support"
depends on SECURITY && !ARCH_EPHEMERAL_INODES
+ select SECURITY_NETWORK
select SECURITY_PATH
help
Landlock is a sandboxing mechanism that enables processes to restrict
diff --git a/security/landlock/Makefile b/security/landlock/Makefile
index 7bbd2f413b3e..53d3c92ae22e 100644
--- a/security/landlock/Makefile
+++ b/security/landlock/Makefile
@@ -2,3 +2,5 @@ obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
landlock-y := setup.o syscalls.o object.o ruleset.o \
cred.o ptrace.o fs.o
+
+landlock-$(CONFIG_INET) += net.o
\ No newline at end of file
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/net.c b/security/landlock/net.c
new file mode 100644
index 000000000000..338bd6dd8e3f
--- /dev/null
+++ b/security/landlock/net.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - Network management and hooks
+ *
+ * Copyright © 2022 Huawei Tech. Co., Ltd.
+ * Copyright © 2022 Microsoft Corporation
+ */
+
+#include <linux/in.h>
+#include <linux/net.h>
+#include <linux/socket.h>
+#include <net/ipv6.h>
+
+#include "common.h"
+#include "cred.h"
+#include "limits.h"
+#include "net.h"
+#include "ruleset.h"
+
+int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
+ const __be16 port, access_mask_t access_rights)
+{
+ int err;
+ const struct landlock_id id = {
+ .key.data = port,
+ .type = LANDLOCK_KEY_NET_PORT,
+ };
+ BUILD_BUG_ON(sizeof(port) > sizeof(id.key.data));
+
+ /* Transforms relative access rights to absolute ones. */
+ access_rights |= LANDLOCK_MASK_ACCESS_NET &
+ ~landlock_get_net_access_mask(ruleset, 0);
+
+ mutex_lock(&ruleset->lock);
+ err = landlock_insert_rule(ruleset, id, access_rights);
+ mutex_unlock(&ruleset->lock);
+
+ return err;
+}
+
+static int check_addrlen(const struct sockaddr *const address, int addrlen)
+{
+ if (addrlen < offsetofend(struct sockaddr, sa_family))
+ return -EINVAL;
+ switch (address->sa_family) {
+ case AF_UNSPEC:
+ case AF_INET:
+ if (addrlen < sizeof(struct sockaddr_in))
+ return -EINVAL;
+ return 0;
+#if IS_ENABLED(CONFIG_IPV6)
+ case AF_INET6:
+ if (addrlen < SIN6_LEN_RFC2133)
+ return -EINVAL;
+ return 0;
+#endif
+ }
+ WARN_ON_ONCE(1);
+ return 0;
+}
+
+static int check_socket_access(const struct landlock_ruleset *const domain,
+ struct sockaddr *address, __be16 port,
+ access_mask_t access_request)
+{
+ bool allowed = false;
+ layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {};
+ const struct landlock_rule *rule;
+ access_mask_t handled_access;
+ const struct landlock_id id = {
+ .key.data = port,
+ .type = LANDLOCK_KEY_NET_PORT,
+ };
+
+ if (WARN_ON_ONCE(!domain))
+ return 0;
+ if (WARN_ON_ONCE(domain->num_layers < 1))
+ return -EACCES;
+
+ switch (address->sa_family) {
+ case AF_UNSPEC:
+ /*
+ * Connecting to an address with AF_UNSPEC dissolves the TCP
+ * association, which have the same effect as closing the
+ * connection while retaining the socket object (i.e., the file
+ * descriptor). As for dropping privileges, closing
+ * connections is always allowed.
+ */
+ if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP)
+ return 0;
+
+ /*
+ * For compatibility reason, accept AF_UNSPEC for bind
+ * accesses (mapped to AF_INET) only if the address is
+ * INADDR_ANY (cf. __inet_bind). Checking the address is
+ * required to not wrongfully return -EACCES instead of
+ * -EAFNOSUPPORT.
+ */
+ if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
+ const struct sockaddr_in *const sockaddr =
+ (struct sockaddr_in *)address;
+
+ if (sockaddr->sin_addr.s_addr != htonl(INADDR_ANY))
+ return -EAFNOSUPPORT;
+ }
+
+ fallthrough;
+ case AF_INET:
+#if IS_ENABLED(CONFIG_IPV6)
+ case AF_INET6:
+#endif
+ rule = landlock_find_rule(domain, id);
+ handled_access = landlock_init_layer_masks(
+ domain, access_request, &layer_masks,
+ LANDLOCK_KEY_NET_PORT);
+ allowed = landlock_unmask_layers(rule, handled_access,
+ &layer_masks,
+ ARRAY_SIZE(layer_masks));
+
+ fallthrough;
+ }
+ return allowed ? 0 : -EACCES;
+}
+
+static u16 get_port(const struct sockaddr *const address)
+{
+ /* Gets port value in host byte order. */
+ switch (address->sa_family) {
+ case AF_UNSPEC:
+ case AF_INET: {
+ const struct sockaddr_in *const sockaddr =
+ (struct sockaddr_in *)address;
+ return sockaddr->sin_port;
+ }
+#if IS_ENABLED(CONFIG_IPV6)
+ case AF_INET6: {
+ const struct sockaddr_in6 *const sockaddr_ip6 =
+ (struct sockaddr_in6 *)address;
+ return sockaddr_ip6->sin6_port;
+ }
+#endif
+ }
+ WARN_ON_ONCE(1);
+ return 0;
+}
+
+static int hook_socket_bind(struct socket *sock, struct sockaddr *address,
+ int addrlen)
+{
+ int ret;
+ const struct landlock_ruleset *const dom =
+ landlock_get_current_domain();
+
+ if (!dom)
+ return 0;
+
+ /* Check if it's a TCP socket. */
+ if (sock->type != SOCK_STREAM)
+ return 0;
+
+ ret = check_addrlen(address, addrlen);
+ if (ret)
+ return ret;
+
+ return check_socket_access(dom, address, get_port(address),
+ LANDLOCK_ACCESS_NET_BIND_TCP);
