netdev - Re: [PATCH v11 08/12] landlock: Add network rules and TCP hooks support

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Date: Thu, 3 Aug 2023 16:12:02 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
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 v11 08/12] landlock: Add network rules and TCP hooks
 support

On Tue, May 16, 2023 at 12:13:35AM +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.
> 
> Co-developed-by: Mickaël Salaün <mic@...ikod.net>
> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
> ---

[...]

> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
> index 8a54e87dbb17..5cb0a1bc6ec0 100644
> --- a/security/landlock/syscalls.c
> +++ b/security/landlock/syscalls.c

[...]

> +static int add_rule_net_service(struct landlock_ruleset *ruleset,
> +				const void __user *const rule_attr)
> +{
> +#if IS_ENABLED(CONFIG_INET)

We should define two add_rule_net_service() functions according to
IS_ENABLED(CONFIG_INET) instead of changing the body of the only
function.  The second function would only return -EAFNOSUPPORT.  This
cosmetic change would make the code cleaner.


> +	struct landlock_net_service_attr net_service_attr;
> +	int res;
> +	access_mask_t mask;
> +
> +	/* Copies raw user space buffer, only one type for now. */
> +	res = copy_from_user(&net_service_attr, rule_attr,
> +			     sizeof(net_service_attr));
> +	if (res)
> +		return -EFAULT;
> +
> +	/*
> +	 * Informs about useless rule: empty allowed_access (i.e. deny rules)
> +	 * are ignored by network actions.
> +	 */
> +	if (!net_service_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_service_attr.allowed_access | mask) != mask)
> +		return -EINVAL;
> +
> +	/* Denies inserting a rule with port 0 or higher than 65535. */
> +	if ((net_service_attr.port == 0) || (net_service_attr.port > U16_MAX))
> +		return -EINVAL;
> +
> +	/* Imports the new rule. */
> +	return landlock_append_net_rule(ruleset, net_service_attr.port,
> +					net_service_attr.allowed_access);
> +#else /* IS_ENABLED(CONFIG_INET) */
> +	return -EAFNOSUPPORT;
> +#endif /* IS_ENABLED(CONFIG_INET) */
> +}