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Message-ID: <20220829170401.834298-10-konstantin.meskhidze@huawei.com> Date: Tue, 30 Aug 2022 01:03:52 +0800 From: Konstantin Meskhidze <konstantin.meskhidze@...wei.com> To: <mic@...ikod.net> CC: <willemdebruijn.kernel@...il.com>, <gnoack3000@...il.com>, <linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>, <netfilter-devel@...r.kernel.org>, <yusongping@...wei.com>, <hukeping@...wei.com>, <anton.sirazetdinov@...wei.com> Subject: [PATCH v7 09/18] landlock: implement TCP network hooks This patch adds support of socket_bind() and socket_connect() hooks. It's possible to restrict binding and connecting of TCP types of sockets to particular ports. It's just basic idea of how Landlock could support network confinement. Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com> --- Changes since v6: * Updates copyright. * Refactors landlock_append_net_rule() and check_socket_access() functions with landlock_id type. Changes since v5: * Fixes some logic errors. * Formats code with clang-format-14. Changes since v4: * Factors out CONFIG_INET into make file. * Refactors check_socket_access(). * Adds helper get_port(). * Adds CONFIG_IPV6 in get_port(), hook_socket_bind/connect functions to support AF_INET6 family. * Adds AF_UNSPEC family support in hook_socket_bind/connect functions. * Refactors add_rule_net_service() and landlock_add_rule syscall to support network rule inserting. * Refactors init_layer_masks() to support network rules. Changes since v3: * Splits commit. * Adds SECURITY_NETWORK in config. * Adds IS_ENABLED(CONFIG_INET) if a kernel has no INET configuration. * Adds hook_socket_bind and hook_socket_connect hooks. --- security/landlock/Kconfig | 1 + security/landlock/Makefile | 2 + security/landlock/net.c | 161 +++++++++++++++++++++++++++++++++++ security/landlock/net.h | 26 ++++++ security/landlock/setup.c | 2 + security/landlock/syscalls.c | 59 ++++++++++++- 6 files changed, 248 insertions(+), 3 deletions(-) create mode 100644 security/landlock/net.c create mode 100644 security/landlock/net.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/net.c b/security/landlock/net.c new file mode 100644 index 000000000000..0d249ad619bf --- /dev/null +++ b/security/landlock/net.c @@ -0,0 +1,161 @@ +// 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 "cred.h" +#include "limits.h" +#include "net.h" + +int landlock_append_net_rule(struct landlock_ruleset *const ruleset, u16 port, + u32 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_socket_access(const struct landlock_ruleset *const domain, + u16 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; + + rule = landlock_find_rule(domain, id); + handled_access = init_layer_masks(domain, access_request, &layer_masks, + LANDLOCK_KEY_NET_PORT); + allowed = unmask_layers(rule, handled_access, &layer_masks, + ARRAY_SIZE(layer_masks)); + + 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 ntohs(sockaddr->sin_port); + } +#if IS_ENABLED(CONFIG_IPV6) + case AF_INET6: { + const struct sockaddr_in6 *const sockaddr_ip6 = + (struct sockaddr_in6 *)address; + return ntohs(sockaddr_ip6->sin6_port); + } +#endif + } + WARN_ON_ONCE(1); + return 0; +} + +static int hook_socket_bind(struct socket *sock, struct sockaddr *address, + int addrlen) +{ + 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; + + switch (address->sa_family) { + case AF_UNSPEC: + case AF_INET: +#if IS_ENABLED(CONFIG_IPV6) + case AF_INET6: +#endif + return check_socket_access(dom, get_port(address), + LANDLOCK_ACCESS_NET_BIND_TCP); + default: + return 0; + } +} + +static int hook_socket_connect(struct socket *sock, struct sockaddr *address, + int addrlen) +{ + 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; + + /* Check if the hook is AF_INET* socket's action. */ + switch (address->sa_family) { + case AF_INET: +#if IS_ENABLED(CONFIG_IPV6) + case AF_INET6: +#endif + return check_socket_access(dom, get_port(address), + LANDLOCK_ACCESS_NET_CONNECT_TCP); + case AF_UNSPEC: { + u16 i; + /* + * If just in a layer a mask supports connect access, + * the socket_connect() hook with AF_UNSPEC family flag + * must be banned. This prevents from disconnecting already + * connected sockets. + */ + for (i = 0; i < dom->num_layers; i++) { + if (landlock_get_net_access_mask(dom, i) & + LANDLOCK_ACCESS_NET_CONNECT_TCP) + return -EACCES; + } + } + } + return 0; +} + +static struct security_hook_list landlock_hooks[] __lsm_ro_after_init = { + LSM_HOOK_INIT(socket_bind, hook_socket_bind), + LSM_HOOK_INIT(socket_connect, hook_socket_connect), +}; + +__init void landlock_add_net_hooks(void) +{ + security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks), + LANDLOCK_NAME); +} diff --git a/security/landlock/net.h b/security/landlock/net.h new file mode 100644 index 000000000000..2c63a8f1b258 --- /dev/null +++ b/security/landlock/net.h @@ -0,0 +1,26 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Landlock LSM - Network management and hooks + * + * Copyright © 2022 Huawei Tech. Co., Ltd. + */ + +#ifndef _SECURITY_LANDLOCK_NET_H +#define _SECURITY_LANDLOCK_NET_H + +#include "common.h" +#include "ruleset.h" +#include "setup.h" + +#if IS_ENABLED(CONFIG_INET) +__init void landlock_add_net_hooks(void); + +int landlock_append_net_rule(struct landlock_ruleset *const ruleset, u16 port, + u32 access_hierarchy); +#else /* IS_ENABLED(CONFIG_INET) */ +static inline void landlock_add_net_hooks(void) +{ +} +#endif /* IS_ENABLED(CONFIG_INET) */ + +#endif /* _SECURITY_LANDLOCK_NET_H */ diff --git a/security/landlock/setup.c b/security/landlock/setup.c index f8e8e980454c..8059dc0b47d3 100644 --- a/security/landlock/setup.c +++ b/security/landlock/setup.c @@ -14,6 +14,7 @@ #include "fs.h" #include "ptrace.h" #include "setup.h" +#include "net.h" bool landlock_initialized __lsm_ro_after_init = false; @@ -28,6 +29,7 @@ static int __init landlock_init(void) landlock_add_cred_hooks(); landlock_add_ptrace_hooks(); landlock_add_fs_hooks(); + landlock_add_net_hooks(); landlock_initialized = true; pr_info("Up and running.\n"); return 0; diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index 641155f6f6f8..16880e951346 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -29,6 +29,7 @@ #include "cred.h" #include "fs.h" #include "limits.h" +#include "net.h" #include "ruleset.h" #include "setup.h" @@ -74,7 +75,8 @@ static void build_check_abi(void) { struct landlock_ruleset_attr ruleset_attr; struct landlock_path_beneath_attr path_beneath_attr; - size_t ruleset_size, path_beneath_size; + struct landlock_net_service_attr net_service_attr; + size_t ruleset_size, path_beneath_size, net_service_size; /* * For each user space ABI structures, first checks that there is no @@ -90,6 +92,11 @@ static void build_check_abi(void) path_beneath_size += sizeof(path_beneath_attr.parent_fd); BUILD_BUG_ON(sizeof(path_beneath_attr) != path_beneath_size); BUILD_BUG_ON(sizeof(path_beneath_attr) != 12); + + net_service_size = sizeof(net_service_attr.allowed_access); + net_service_size += sizeof(net_service_attr.port); + BUILD_BUG_ON(sizeof(net_service_attr) != net_service_size); + BUILD_BUG_ON(sizeof(net_service_attr) != 10); } /* Ruleset handling */ @@ -322,13 +329,54 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset, return err; } +static int add_rule_net_service(struct landlock_ruleset *ruleset, + const void __user *const rule_attr) +{ +#if IS_ENABLED(CONFIG_INET) + struct landlock_net_service_attr net_service_attr; + int res; + u32 mask; + + /* Copies raw user space buffer, only one type for now. */ + res = copy_from_user(&net_service_attr, rule_attr, + sizeof(net_service_attr)); + if (res) + return -EFAULT; + + /* + * Informs about useless rule: empty allowed_access (i.e. deny rules) + * are ignored by network actions. + */ + if (!net_service_attr.allowed_access) + return -ENOMSG; + + /* + * Checks that allowed_access matches the @ruleset constraints + * (ruleset->access_masks[0] is automatically upgraded to 64-bits). + */ + mask = landlock_get_net_access_mask(ruleset, 0); + if ((net_service_attr.allowed_access | mask) != mask) + return -EINVAL; + + /* Denies inserting a rule with port 0. */ + if (net_service_attr.port == 0) + return -EINVAL; + + /* Imports the new rule. */ + return landlock_append_net_rule(ruleset, net_service_attr.port, + net_service_attr.allowed_access); +#else /* IS_ENABLED(CONFIG_INET) */ + return -EAFNOSUPPORT; +#endif /* IS_ENABLED(CONFIG_INET) */ +} + /** * sys_landlock_add_rule - Add a new rule to a ruleset * * @ruleset_fd: File descriptor tied to the ruleset that should be extended * with the new rule. - * @rule_type: Identify the structure type pointed to by @rule_attr (only - * LANDLOCK_RULE_PATH_BENEATH for now). + * @rule_type: Identify the structure type pointed to by @rule_attr: + * LANDLOCK_RULE_PATH_BENEATH or LANDLOCK_RULE_NET_SERVICE. * @rule_attr: Pointer to a rule (only of type &struct * landlock_path_beneath_attr for now). * @flags: Must be 0. @@ -339,6 +387,8 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset, * Possible returned errors are: * * - EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time; + * - EAFNOSUPPORT: @rule_type is LANDLOCK_RULE_NET_SERVICE but TCP/IP is not + * supported by the running kernel; * - EINVAL: @flags is not 0, or inconsistent access in the rule (i.e. * &landlock_path_beneath_attr.allowed_access is not a subset of the rule's * accesses); @@ -374,6 +424,9 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd, case LANDLOCK_RULE_PATH_BENEATH: err = add_rule_path_beneath(ruleset, rule_attr); break; + case LANDLOCK_RULE_NET_SERVICE: + err = add_rule_net_service(ruleset, rule_attr); + break; default: err = -EINVAL; break; -- 2.25.1
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