netdev - Re: [PATCH v6 17/17] samples/landlock: adds network demo

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Date:   Wed, 27 Jul 2022 22:26:16 +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,
        anton.sirazetdinov@...wei.com
Subject: Re: [PATCH v6 17/17] samples/landlock: adds network demo


On 21/06/2022 10:23, Konstantin Meskhidze wrote:
> This commit adds network demo. It's possible to
> allow a sandoxer to bind/connect to a list of
> particular ports restricting networks actions to
> the rest of ports.
> 
> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
> ---
> 
> Changes since v5:
> * Makes network ports sandboxing optional.
> * Fixes some logic errors.
> * Formats code with clang-format-14.
> 
> Changes since v4:
> * Adds ENV_TCP_BIND_NAME "LL_TCP_BIND" and
> ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT" variables
> to insert TCP ports.
> * Renames populate_ruleset() to populate_ruleset_fs().
> * Adds populate_ruleset_net() and parse_port_num() helpers.
> * Refactors main() to support network sandboxing.
> 
> ---
>   samples/landlock/sandboxer.c | 118 +++++++++++++++++++++++++++++++----
>   1 file changed, 107 insertions(+), 11 deletions(-)
> 
> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
> index 3e404e51ec64..0606c676fded 100644
> --- a/samples/landlock/sandboxer.c
> +++ b/samples/landlock/sandboxer.c


[...]

> @@ -232,16 +308,36 @@ int main(const int argc, char *const argv[], char *const *const envp)
>   		access_fs_rw &= ~ACCESS_ABI_2;

We need to check the ABI to make this sample work without a kernel 
supporting Landlock network access rights, and error out if the user 
explicitely asked for it anyway (with the environement variable).


>   	}
> 
> +	/* Adds optionally network bind() support. */
> +	env_port_name = getenv(ENV_TCP_BIND_NAME);
> +	if (env_port_name) {
> +		access_net_tcp |= LANDLOCK_ACCESS_NET_BIND_TCP;
> +	}
> +	/* Adds optionally network connect() support. */
> +	env_port_name = getenv(ENV_TCP_CONNECT_NAME);
> +	if (env_port_name) {
> +		access_net_tcp |= LANDLOCK_ACCESS_NET_CONNECT_TCP;
> +	}
> +	ruleset_attr.handled_access_net = access_net_tcp;
> +
>   	ruleset_fd =
>   		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
>   	if (ruleset_fd < 0) {
>   		perror("Failed to create a ruleset");
>   		return 1;
>   	}
> -	if (populate_ruleset(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro)) {
> +	if (populate_ruleset_fs(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro)) {
> +		goto err_close_ruleset;
> +	}
> +	if (populate_ruleset_fs(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) {
> +		goto err_close_ruleset;
> +	}
> +	if (populate_ruleset_net(ENV_TCP_BIND_NAME, ruleset_fd,
> +				 LANDLOCK_ACCESS_NET_BIND_TCP)) {
>   		goto err_close_ruleset;
>   	}
> -	if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) {
> +	if (populate_ruleset_net(ENV_TCP_CONNECT_NAME, ruleset_fd,
> +				 LANDLOCK_ACCESS_NET_CONNECT_TCP)) {
>   		goto err_close_ruleset;
>   	}
>   	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
> --
> 2.25.1
>