Date: Tue, 4 Jul 2023 15:37:20 +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>, <yusongping@...wei.com>,
	<artem.kuzin@...wei.com>
Subject: Re: [PATCH v11 08/12] landlock: Add network rules and TCP hooks
 support



7/3/2023 8:06 PM, Mickaël Salaün пишет:
> 
> On 03/07/2023 12:36, Konstantin Meskhidze (A) wrote:
>> 
>> 
>> 6/26/2023 9:57 PM, Mickaël Salaün пишет:
>>> Complementary review:
>>>
>>> On 15/05/2023 18:13, Konstantin Meskhidze wrote:
>>>> 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 enables to restrict TCP socket binding and connection
>>>> to specific ports.
>>>>
>>>> Co-developed-by: Mickaël Salaün <mic@...ikod.net>
>>>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
>>>> ---
>>>>
>>>> Changes since v10:
>>>> * Removes "packed" attribute.
>>>> * Applies Mickaёl's patch with some refactoring.
>>>> * Deletes get_port() and check_addrlen() helpers.
>>>> * Refactors check_socket_access() by squashing get_port() and
>>>> check_addrlen() helpers into it.
>>>> * Fixes commit message.
>>>>
>>>> Changes since v9:
>>>> * Changes UAPI port field to __u64.
>>>> * Moves shared code into check_socket_access().
>>>> * Adds get_raw_handled_net_accesses() and
>>>> get_current_net_domain() helpers.
>>>> * Minor fixes.
>>>>
>>>> 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                |  48 +++++
>>>>    security/landlock/Kconfig                    |   1 +
>>>>    security/landlock/Makefile                   |   2 +
>>>>    security/landlock/limits.h                   |   6 +-
>>>>    security/landlock/net.c                      | 174 +++++++++++++++++++
>>>>    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, 425 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 81d09ef9aa50..93794759dad4 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;
>>>> +
>>>
>>> Please remove this empty line.
>> 
>>    Ok. Thanks.
>>>
>>>
>>>> +	/**
>>>> +	 * @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 +91,23 @@ struct landlock_path_beneath_attr {
>>>>    	 */
>>>>    } __attribute__((packed));
>>>>
>>>> +/**
>>>> + * struct landlock_net_service_attr - TCP subnet definition
>>>
>>> s/TCP subnet definition/Network service definition/
>>>
>>     Ok. Thanks.
>>>
>>>> + *
>>>> + * 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.
>>>> +	 */
>>>> +	__u64 port;
>>>> +};
>>>> +
>>>>    /**
>>>>     * DOC: fs_access
>>>>     *
>>>> @@ -189,4 +218,23 @@ 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 */
>>>
>>> Please the empty line to make this patch clean.
>> 
>>    Ok. I will.
>>>
>>>
>>>>    #endif /* _SECURITY_LANDLOCK_LIMITS_H */
>>>> diff --git a/security/landlock/net.c b/security/landlock/net.c
>>>> new file mode 100644
>>>> index 000000000000..f8d2be53ac0d
>>>> --- /dev/null
>>>> +++ b/security/landlock/net.c
>>>> @@ -0,0 +1,174 @@
>>>> +// 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 = (__force uintptr_t)htons(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 access_mask_t
>>>> +get_raw_handled_net_accesses(const struct landlock_ruleset *const domain)
>>>> +{
>>>> +	access_mask_t access_dom = 0;
>>>> +	size_t layer_level;
>>>> +
>>>> +	for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
>>>> +		access_dom |= landlock_get_net_access_mask(domain, layer_level);
>>>> +	return access_dom;
>>>> +}
>>>> +
>>>> +static const struct landlock_ruleset *get_current_net_domain(void)
>>>> +{
>>>> +	const struct landlock_ruleset *const dom =
>>>> +		landlock_get_current_domain();
>>>> +
>>>> +	if (!dom || !get_raw_handled_net_accesses(dom))
>>>> +		return NULL;
>>>> +
>>>> +	return dom;
>>>> +}
>>>> +
>>>> +static int check_socket_access(struct socket *const sock,
>>>> +			       struct sockaddr *const address,
>>>> +			       const int addrlen,
>>>> +			       const access_mask_t access_request)
>>>> +{
>>>> +	__be16 port;
>>>> +	layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {};
>>>> +	const struct landlock_rule *rule;
>>>> +	access_mask_t handled_access;
>>>> +	struct landlock_id id = {
>>>> +		.type = LANDLOCK_KEY_NET_PORT,
>>>> +	};
>>>> +	const struct landlock_ruleset *const domain = get_current_net_domain();
>>>> +
>>>> +	if (WARN_ON_ONCE(!domain))
>>>
>>> The WARN_ON_ONCE() needs to be removed for processes not sandboxed. This
>>> should be printed when running the tests.
>>>
>>    Probably during the boot stage it prints once since no process is
>>    landlocked at this stage.
>>    So we need to leave it like this:
>> 	if (!domain)
>>           	return 0;
> 
> Yes
> 
> 
>>     ????
>>>
>>>
>>>> +		return 0;
>>>> +	if (WARN_ON_ONCE(domain->num_layers < 1))
>>>> +		return -EACCES;
>>>> +
>>>> +	/* Checks if it's a TCP socket. */
>>>> +	if (sock->type != SOCK_STREAM)
>>>> +		return 0;
>>>> +
>>>> +	/* Checks for minimal header length. */
>>>> +	if (addrlen < offsetofend(struct sockaddr, sa_family))
>>>
>>> You can use "typeof(*address)" instead of struct sockaddr, this makes it
>>> easier to review.
>>>
>>     Do mean to change offsetofend() by typeof(*address)??
> 
> No: if (addrlen < offsetofend(typeof(*address), sa_family))
> 
   Got it. Thanks.
>>>
>>>> +		return -EINVAL;
>>>> +
>>>
>>> [...]
>>> .
> .

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