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@xxxxxxxxxxx
>
> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx>
> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx>
> ---
>
> 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);
> +}
