netdev - Re: [RFC PATCH v4 07/15] landlock: user space API network support

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Date:   Tue, 12 Apr 2022 13:21:36 +0200
From:   Mickaël Salaün <mic@...ikod.net>
To:     Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
Cc:     willemdebruijn.kernel@...il.com,
        linux-security-module@...r.kernel.org, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org, yusongping@...wei.com,
        artem.kuzin@...wei.com, anton.sirazetdinov@...wei.com
Subject: Re: [RFC PATCH v4 07/15] landlock: user space API network support


On 09/03/2022 14:44, Konstantin Meskhidze wrote:
> User space API was refactored to support
> network actions. New network access flags,
> network rule and network attributes were
> added.
> 
> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
> ---
> 
> Changes since v3:
> * Split commit.
> * Refactoring User API for network rule type.
> 
> ---
>   include/uapi/linux/landlock.h | 48 +++++++++++++++++++++++++++++++++++
>   security/landlock/syscalls.c  |  5 ++--
>   2 files changed, 51 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
> index b3d952067f59..4fc6c793fdf4 100644
> --- a/include/uapi/linux/landlock.h
> +++ b/include/uapi/linux/landlock.h
> @@ -25,6 +25,13 @@ struct landlock_ruleset_attr {
>   	 * compatibility reasons.
>   	 */
>   	__u64 handled_access_fs;
> +
> +	/**
> +	 * @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;
>   };
> 
>   /*
> @@ -46,6 +53,11 @@ 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,
>   };
> 
>   /**
> @@ -70,6 +82,24 @@ struct landlock_path_beneath_attr {
>   	 */
>   } __attribute__((packed));
> 
> +/**
> + * struct landlock_net_service_attr - TCP subnet definition
> + *
> + * 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
> +	 */
> +	__u16 port;
> +
> +} __attribute__((packed));
> +
>   /**
>    * DOC: fs_access
>    *
> @@ -134,4 +164,22 @@ struct landlock_path_beneath_attr {
>   #define LANDLOCK_ACCESS_FS_MAKE_BLOCK			(1ULL << 11)
>   #define LANDLOCK_ACCESS_FS_MAKE_SYM			(1ULL << 12)
> 
> +/**
> + * 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.
> + */
> +#define LANDLOCK_ACCESS_NET_BIND_TCP			(1ULL << 0)
> +#define LANDLOCK_ACCESS_NET_CONNECT_TCP			(1ULL << 1)
> +
>   #endif /* _UAPI_LINUX_LANDLOCK_H */
> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
> index 8c0f6165fe3a..fcbce83d64ef 100644
> --- a/security/landlock/syscalls.c
> +++ b/security/landlock/syscalls.c
> @@ -81,8 +81,9 @@ static void build_check_abi(void)
>   	 * struct size.
>   	 */
>   	ruleset_size = sizeof(ruleset_attr.handled_access_fs);
> +	ruleset_size += sizeof(ruleset_attr.handled_access_net);
>   	BUILD_BUG_ON(sizeof(ruleset_attr) != ruleset_size);
> -	BUILD_BUG_ON(sizeof(ruleset_attr) != 8);
> +	BUILD_BUG_ON(sizeof(ruleset_attr) != 16);
> 
>   	path_beneath_size = sizeof(path_beneath_attr.allowed_access);
>   	path_beneath_size += sizeof(path_beneath_attr.parent_fd);
> @@ -184,7 +185,7 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
> 
>   	/* Checks content (and 32-bits cast). */
>   	if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_ACCESS_FS) !=
> -			LANDLOCK_MASK_ACCESS_FS)
> +			 LANDLOCK_MASK_ACCESS_FS)

Don't add cosmetic changes. FYI, I'm relying on the way Vim does line 
cuts, which is mostly tabs. Please try to do the same.


>   		return -EINVAL;
>   	access_mask_set.fs = ruleset_attr.handled_access_fs;
> 
> --
> 2.25.1
> 

You need to also update Documentation/userspace-api/landlock.rst 
accordingly. You can check you changes by building the HTML doc.