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Message-ID: <258ba4aa-6b12-abda-75b9-ffa196fba683@huawei.com>
Date: Thu, 5 Jan 2023 11:57:29 +0300
From: "Konstantin Meskhidze (A)" <konstantin.meskhidze@...wei.com>
To: Mickaël Salaün <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>, <artem.kuzin@...wei.com>,
<linux-api@...r.kernel.org>,
"Alejandro Colomar (man-pages)" <alx.manpages@...il.com>
Subject: Re: [PATCH v8 08/12] landlock: Implement TCP network hooks
11/17/2022 9:43 PM, Mickaël Salaün пишет:
>
> On 21/10/2022 17:26, Konstantin Meskhidze wrote:
>> This patch adds support of socket_bind() and socket_connect() hooks.
>> It's possible to restrict binding and connecting of TCP sockets to
>> particular ports.
>
> 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@...wei.com>
>> ---
>>
>> Changes since v7:
>> * Minor fixes.
>> * Refactors commit message.
>>
>> 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 | 164 +++++++++++++++++++++++++++++++++++
>> security/landlock/net.h | 26 ++++++
>> security/landlock/setup.c | 2 +
>> security/landlock/syscalls.c | 59 ++++++++++++-
>> 6 files changed, 251 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..39e8a156a1f4
>> --- /dev/null
>> +++ b/security/landlock/net.c
>> @@ -0,0 +1,164 @@
>> +// 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 u16 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_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)
>
> get_port() should return a __be16 type. This enables to avoid converting
> port when checking a rule.
In this case a user must do a coverting port into __be16:
struct landlock_net_service_attr net_service = {
.allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP,
.port = htons(sock_port),
};
I think that a user should not think about this conversion cause it
makes UAPI more complex to use. Lets do this under kernel's hood and let
it as it is now -> u16 port.
What do you think?
>
> make C=2 security/landlock/ must not print any warning.
>
>
>> +{
>> + /* 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;
>
> You can remove this default case and move the return 0 at the end of the
> function.
>
>
>> + }
>> +}
>> +
>> +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;
>
> You can move "i" after the "dom" declaration to remove the extra braces.
>
>
>> +
>> + /*
>> + * 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;
>
> I'm wondering if this is the right error code for this case. EPERM may
> be more appropriate.
>
> Thinking more about this case, I don't understand what is the rationale
> to deny such action. What would be the consequence to always allow
> connection with AF_UNSPEC (i.e. to disconnect a socket)?
>
>
>> + }
>> + }
>> + }
>> + 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..0da1d9dff5ab
>> --- /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,
>> + const u16 port, access_mask_t access_rights);
>> +#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 3f196d2ce4f9..7e4a598177b8 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;
>>
>> @@ -29,6 +30,7 @@ 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 c5a6ad4e2fca..7853f32e8325 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;
>
> access_mask_t 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
>
> %LANDLOCK_RULE_NET_SERVICE
>
>
>> + * 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
>> * ruleset handled accesses);
>> @@ -373,6 +423,9 @@ 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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