Re: [PATCH v12 08/12] landlock: Add network rules and TCP hooks support

["Mickaël Salaün" <mic@digikod.net>]

On Tue, Oct 10, 2023 at 05:20:45AM +0300, Konstantin Meskhidze (A) wrote:
> 
> 
> 10/9/2023 5:12 PM, Mickaël Salaün пишет:
> > 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@digikod.net>
> > > > Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.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
> > 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.
> > .
>   Ok.Will be moved back to syscalls.c.
>   What about renaming to add_rule_net_service()->add_rule_net_port() ???

Yes please rename it, there should be no mention of "net_service"
anymore.