Date: Tue, 10 Oct 2023 05:23:22 +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 v12 08/12] landlock: Add network rules and TCP hooks
 support



10/9/2023 5:13 PM, Mickaël Salaün пишет:
> On Mon, Oct 09, 2023 at 04:12:42PM +0200, Mickaël Salaün wrote:
>> On Mon, Oct 02, 2023 at 10:26:36PM +0200, Mickaël Salaün wrote:
>> > Thanks for this new version Konstantin. I pushed this series, with minor
>> > changes, to -next. So far, no warning. But it needs some changes, mostly
>> > kernel-only, but also one with the handling of port 0 with bind (see my
>> > review below).
>> > 
>> > On Wed, Sep 20, 2023 at 05:26:36PM +0800, 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.
>> > > The new landlock_net_port_attr structure has two fields. The allowed_access
>> > > field contains the LANDLOCK_ACCESS_NET_* rights. The port field contains
>> > > the port value according to the allowed protocol. This field can
>> > > take up to a 64-bit value [1] but the maximum value depends on the related
>> > > protocol (e.g. 16-bit for TCP).
>> > > 
>> > > [1]
>> > > https://lore.kernel.org/r/278ab07f-7583-a4e0-3d37-1bacd091531d@digikod.net
>> > > 
>> > > Signed-off-by: Mickaël Salaün <mic@...ikod.net>
>> > > Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
>> > > ---
>> > > 
>> > > Changes since v11:
>> > > * Replace dates with "2022-2023" in net.c/h files headers.
>> > > * Removes WARN_ON_ONCE(!domain) in check_socket_access().
>> > > * Using "typeof(*address)" instead of offsetofend(struct sockaddr, sa_family).
>> > > * Renames LANDLOCK_RULE_NET_SERVICE to LANDLOCK_RULE_NET_PORT.
>> > > * Renames landlock_net_service_attr to landlock_net_port_attr.
>> > > * Defines two add_rule_net_service() functions according to
>> > >   IS_ENABLED(CONFIG_INET) instead of changing the body of the only
>> > >   function.
>> > > * Adds af_family consistency check while handling AF_UNSPEC specifically.
>> > > * Adds bind_access_mask in add_rule_net_service() to deny all rules with bind
>> > >   action on port zero.
>> > > * Minor fixes.
>> > > * Refactors commit message.
>> > > 
>> > > 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                |  47 ++++
>> > >  security/landlock/Kconfig                    |   3 +-
>> > >  security/landlock/Makefile                   |   2 +
>> > >  security/landlock/limits.h                   |   5 +
>> > >  security/landlock/net.c                      | 241 +++++++++++++++++++
>> > >  security/landlock/net.h                      |  35 +++
>> > >  security/landlock/ruleset.c                  |  62 ++++-
>> > >  security/landlock/ruleset.h                  |  59 ++++-
>> > >  security/landlock/setup.c                    |   2 +
>> > >  security/landlock/syscalls.c                 |  33 ++-
>> > >  tools/testing/selftests/landlock/base_test.c |   2 +-
>> > >  11 files changed, 467 insertions(+), 24 deletions(-)
>> > >  create mode 100644 security/landlock/net.c
>> > >  create mode 100644 security/landlock/net.h
>> > > 
>> 
>> > > diff --git a/security/landlock/net.c b/security/landlock/net.c
>> > > new file mode 100644
>> > > index 000000000000..62b830653e25
>> > > --- /dev/null
>> > > +++ b/security/landlock/net.c
>> > > @@ -0,0 +1,241 @@
>> > > +// SPDX-License-Identifier: GPL-2.0-only
>> > > +/*
>> > > + * Landlock LSM - Network management and hooks
>> > > + *
>> > > + * Copyright © 2022-2023 Huawei Tech. Co., Ltd.
>> > > + * Copyright © 2022-2023 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)
>> > 
>> > This function is only used in add_rule_net_service(), so it should not
>> > be exported, and we can merge it (into landlock_add_rule_net_port).
>> > 
>> > > +{
>> > > +	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;
>> > > +}
>> > > +
>> > > +int add_rule_net_service(struct landlock_ruleset *ruleset,
>> > 
>> > We should only export functions with a "landlock_" prefix, and "service"
>> > is now replaced with "port", which gives landlock_add_rule_net_port().
>> > 
>> > For consistency, we should also rename add_rule_path_beneath() into
>> > landlock_add_rule_path_beneath(), move it into fs.c, and merge
>> > landlock_append_fs_rule() into it (being careful to not move the related
>> > code to ease review). This change should be part of the "landlock:
>> > Refactor landlock_add_rule() syscall" patch. Please be careful to keep
>> > the other changes happening in other patches.
>> > 
>> > 
>> > > +			 const void __user *const rule_attr)
>> > > +{
>> > > +	struct landlock_net_port_attr net_port_attr;
>> > > +	int res;
>> > > +	access_mask_t mask, bind_access_mask;
>> > > +
>> > > +	/* Copies raw user space buffer. */
>> > > +	res = copy_from_user(&net_port_attr, rule_attr, sizeof(net_port_attr));
>> > 
>> > We should include <linux/uaccess.h> because of copy_from_user().
>> > 
>> > Same for landlock_add_rule_path_beneath().
>> > 
>> > > +	if (res)
>> > > +		return -EFAULT;
>> > > +
>> > > +	/*
>> > > +	 * Informs about useless rule: empty allowed_access (i.e. deny rules)
>> > > +	 * are ignored by network actions.
>> > > +	 */
>> > > +	if (!net_port_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_port_attr.allowed_access | mask) != mask)
>> > > +		return -EINVAL;
>> > > +
>> > > +	/*
>> > > +	 * Denies inserting a rule with port 0 (for bind action) or
>> > > +	 * higher than 65535.
>> > > +	 */
>> > > +	bind_access_mask = net_port_attr.allowed_access &
>> > > +			   LANDLOCK_ACCESS_NET_BIND_TCP;
>> > > +	if (((net_port_attr.port == 0) &&
>> > > +	     (bind_access_mask == LANDLOCK_ACCESS_NET_BIND_TCP)) ||
>> > > +	    (net_port_attr.port > U16_MAX))
>> > > +		return -EINVAL;
>> > > +
>> > > +	/* Imports the new rule. */
>> > > +	return landlock_append_net_rule(ruleset, net_port_attr.port,
>> > > +					net_port_attr.allowed_access);
>> > > +}
>> 
>> Please ignore the above suggestions. Thinking more about this, let's
>> keep the static add_rule_net_service() in syscalls.c, and only make the
>> inline landlock_add_rule_net_service() return -EAFNOSUPPORT (which is
> 
> "inline landlock_append_net_rule()" of course

    yep. got it.
> 
>> already the case with this patch when CONFIG_INET is not set). This will
>> slightly change the current semantic but enable to check all the
>> syscalls arguments even if CONFIG_INET is not set, which is a good thing
>> (and should be reflected in tests). It is better to group all the code
>> handling user space memory copying and ABI specificities in the
>> syscalls.c file. This approach is simpler, it will avoid the exported
>> function issues (e.g. add_rule_net_service), and it will not require
>> more changes to the fs.[ch] files.
> .

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