Message-ID: <55092d4f-b076-d4fc-e75f-b4981a382a78@huawei.com>
Date: Mon, 3 Jul 2023 13:36:23 +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



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;
   ????
> 
> 
>> +		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)??
> 
>> +		return -EINVAL;
>> +
> 
> [...]
> .

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