Re: [PATCH v8 08/12] landlock: Implement TCP network hooks

["Konstantin Meskhidze (A)" <konstantin.meskhidze@huawei.com>]

1/9/2023 3:38 PM, Mickaël Salaün пишет:
> 
> On 09/01/2023 09:07, Konstantin Meskhidze (A) wrote:
>> 
>> 
>> 1/6/2023 10:30 PM, Mickaël Salaün пишет:
>>>
>>> On 05/01/2023 09:57, Konstantin Meskhidze (A) wrote:
>>>>
>>>>
>>>> 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@huawei.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?
>>>
>>> BE and LE conversions may be error prone without strong typing, but the
>>> current Linux network UAPI uses this convention (see related syscalls),
>>> so developers already use htons() in their applications. I think it is
>>> less hazardous to use the same convention. It would be nice to have the
>>> point of view of network and API folks though.
>> 
>>     Ok. Thanks. Let ports be in BE format like in network packets.
>> 
>>     What should a selftest with port conversion be like?
>> 
>>     1. Set a port with a Landlock rule with no conversion. get an error
>> wit bind/connect actions.
>>     2. Convert a port with htons(sock_port). get no error.
>> 
>>     What do you think?
> 
> Right, you can do both on a LE architecture (that must be checked in the
> test or it should be skipped), test with a port value that has different
> representation in LE and BE.

   Do you mean to check architecture in a test first and then port 
representaton? What about BE architectures? My current VM is X86-64 
architecture a LE one. I can test just it now.
> .