Message-ID: <369537f3-78e1-2a4e-c010-d56e29c2f315@digikod.net>
Date:   Mon, 12 Sep 2022 19:18:15 +0200
From:   Mickaël Salaün <mic@...ikod.net>
To:     "Konstantin Meskhidze (A)" <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, anton.sirazetdinov@...wei.com
Subject: Re: [PATCH v7 08/18] landlock: add network rules support


On 10/09/2022 20:27, Konstantin Meskhidze (A) wrote:
> 
> 
> 9/6/2022 11:08 AM, Mickaël Salaün пишет:
>>
>> On 29/08/2022 19:03, Konstantin Meskhidze wrote:
>>> This commit adds network rules support in internal landlock functions
>>> (presented in ruleset.c) and landlock_create_ruleset syscall.
>>>
>>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
>>> ---
>>>
>>> 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.
>>>
>>> ---
>>>    security/landlock/limits.h   |  6 +++++-
>>>    security/landlock/ruleset.c  | 38 +++++++++++++++++++++++++++++----
>>>    security/landlock/ruleset.h  | 41 ++++++++++++++++++++++++++++++++++--
>>>    security/landlock/syscalls.c |  8 ++++++-
>>>    4 files changed, 85 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/security/landlock/limits.h b/security/landlock/limits.h
>>> index bafb3b8dc677..8a1a6463c64e 100644
>>> --- a/security/landlock/limits.h
>>> +++ b/security/landlock/limits.h
>>> @@ -23,6 +23,10 @@
>>>    #define LANDLOCK_NUM_ACCESS_FS		__const_hweight64(LANDLOCK_MASK_ACCESS_FS)
>>>    #define LANDLOCK_SHIFT_ACCESS_FS	0
>>>
>>> -/* clang-format on */
>>> +#define LANDLOCK_LAST_ACCESS_NET	LANDLOCK_ACCESS_NET_CONNECT_TCP
>>> +#define LANDLOCK_MASK_ACCESS_NET	((LANDLOCK_LAST_ACCESS_NET << 1) - 1)
>>> +#define LANDLOCK_NUM_ACCESS_NET		__const_hweight64(LANDLOCK_MASK_ACCESS_NET)
>>> +#define LANDLOCK_SHIFT_ACCESS_NET	LANDLOCK_NUM_ACCESS_FS
>>>
>>> +/* clang-format on */
>>>    #endif /* _SECURITY_LANDLOCK_LIMITS_H */
>>> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
>>> index 84fcd8eb30d4..442f212039df 100644
>>> --- a/security/landlock/ruleset.c
>>> +++ b/security/landlock/ruleset.c
>>> @@ -36,6 +36,7 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
>>>    	refcount_set(&new_ruleset->usage, 1);
>>>    	mutex_init(&new_ruleset->lock);
>>>    	new_ruleset->root_inode = RB_ROOT;
>>> +	new_ruleset->root_net_port = RB_ROOT;
>>>    	new_ruleset->num_layers = num_layers;
>>>    	/*
>>>    	 * hierarchy = NULL
>>> @@ -46,16 +47,21 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
>>>    }
>>>
>>>    struct landlock_ruleset *
>>> -landlock_create_ruleset(const access_mask_t fs_access_mask)
>>> +landlock_create_ruleset(const access_mask_t fs_access_mask,
>>> +			const access_mask_t net_access_mask)
>>>    {
>>>    	struct landlock_ruleset *new_ruleset;
>>>
>>>    	/* Informs about useless ruleset. */
>>> -	if (!fs_access_mask)
>>> +	if (!fs_access_mask && !net_access_mask)
>>>    		return ERR_PTR(-ENOMSG);
>>>    	new_ruleset = create_ruleset(1);
>>> -	if (!IS_ERR(new_ruleset))
>>> +	if (IS_ERR(new_ruleset))
>>> +		return new_ruleset;
>>> +	if (fs_access_mask)
>>>    		landlock_add_fs_access_mask(new_ruleset, fs_access_mask, 0);
>>> +	if (net_access_mask)
>>> +		landlock_add_net_access_mask(new_ruleset, net_access_mask, 0);
>>>    	return new_ruleset;
>>>    }
>>>
>>> @@ -73,6 +79,8 @@ static inline bool is_object_pointer(const enum landlock_key_type key_type)
>>>    	switch (key_type) {
>>>    	case LANDLOCK_KEY_INODE:
>>>    		return true;
>>> +	case LANDLOCK_KEY_NET_PORT:
>>> +		return false;
>>>    	}
>>>    	WARN_ON_ONCE(1);
>>>    	return false;
>>> @@ -126,6 +134,9 @@ static inline struct rb_root *get_root(struct landlock_ruleset *const ruleset,
>>>    	case LANDLOCK_KEY_INODE:
>>>    		root = &ruleset->root_inode;
>>>    		break;
>>> +	case LANDLOCK_KEY_NET_PORT:
>>> +		root = &ruleset->root_net_port;
>>> +		break;
>>>    	}
>>>    	if (WARN_ON_ONCE(!root))
>>>    		return ERR_PTR(-EINVAL);
>>> @@ -154,7 +165,9 @@ static void build_check_ruleset(void)
>>>    	BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
>>>    	BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
>>>    	BUILD_BUG_ON(access_masks <
>>> -		     (LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS));
>>> +		     (LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS) +
>>> +			     (LANDLOCK_MASK_ACCESS_NET
>>> +			      << LANDLOCK_SHIFT_ACCESS_NET));
>>>    }
>>>
>>>    /**
>>> @@ -367,6 +380,11 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
>>>    	if (err)
>>>    		goto out_unlock;
>>>
>>> +	/* Merges the @src network port tree. */
>>> +	err = merge_tree(dst, src, LANDLOCK_KEY_NET_PORT);
>>> +	if (err)
>>> +		goto out_unlock;
>>> +
>>>    out_unlock:
>>>    	mutex_unlock(&src->lock);
>>>    	mutex_unlock(&dst->lock);
>>> @@ -419,6 +437,11 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
>>>    	if (err)
>>>    		goto out_unlock;
>>>
>>> +	/* Copies the @parent network port tree. */
>>> +	err = inherit_tree(parent, child, LANDLOCK_KEY_NET_PORT);
>>> +	if (err)
>>> +		goto out_unlock;
>>> +
>>>    	if (WARN_ON_ONCE(child->num_layers <= parent->num_layers)) {
>>>    		err = -EINVAL;
>>>    		goto out_unlock;
>>> @@ -451,6 +474,9 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
>>>    	rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
>>>    					     node)
>>>    		free_rule(freeme, LANDLOCK_KEY_INODE);
>>> +	rbtree_postorder_for_each_entry_safe(freeme, next,
>>> +					     &ruleset->root_net_port, node)
>>> +		free_rule(freeme, LANDLOCK_KEY_NET_PORT);
>>>    	put_hierarchy(ruleset->hierarchy);
>>>    	kfree(ruleset);
>>>    }
>>> @@ -640,6 +666,10 @@ access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
>>>    		get_access_mask = landlock_get_fs_access_mask;
>>>    		num_access = LANDLOCK_NUM_ACCESS_FS;
>>>    		break;
>>> +	case LANDLOCK_KEY_NET_PORT:
>>> +		get_access_mask = landlock_get_net_access_mask;
>>> +		num_access = LANDLOCK_NUM_ACCESS_NET;
>>> +		break;
>>>    	default:
>>>    		WARN_ON_ONCE(1);
>>>    		return 0;
>>> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
>>> index 2083855bf42d..d456ee90b648 100644
>>> --- a/security/landlock/ruleset.h
>>> +++ b/security/landlock/ruleset.h
>>> @@ -26,7 +26,7 @@ static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
>>>    static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));
>>>
>>>    /* Ruleset access masks. */
>>> -typedef u16 access_masks_t;
>>> +typedef u32 access_masks_t;
>>>    /* Makes sure all ruleset access rights can be stored. */
>>>    static_assert(BITS_PER_TYPE(access_masks_t) >= LANDLOCK_NUM_ACCESS_FS);
>>
>> There is some fixes missing from my patch.
>>
>>
>>>
>>> @@ -66,6 +66,11 @@ enum landlock_key_type {
>>>    	 * keys.
>>>    	 */
>>>    	LANDLOCK_KEY_INODE = 1,
>>
>>
>> #if IS_ENABLED(CONFIG_INET)
>>
>>> +	/**
>>> +	 * @LANDLOCK_KEY_NET_PORT: Type of &landlock_ruleset.root_net_port's
>>> +	 * node keys.
>>> +	 */
>>> +	LANDLOCK_KEY_NET_PORT = 2,
>>
>> #endif /* IS_ENABLED(CONFIG_INET) */
>>
>> And then all use of LANDLOCK_KEY_NET_PORT should be surrounded by the
>> same check (but not directly in the net.c file).
> 
>    I checked the branch with your patches: tmp-net
> (7d6cf40a6f81adf607ad3cc17aaa11e256beeea4), but I did not find #if
> IS_ENABLED(CONFIG_INET) surrounding LANDLOCK_KEY_NET_PORT.

You need to write that yourself.


>>
>>
>>>    };
>>>
>>>    /**
>>> @@ -133,6 +138,12 @@ struct landlock_ruleset {
>>>    	 * reaches zero.
>>>    	 */
>>>    	struct rb_root root_inode;
>>
>> #if IS_ENABLED(CONFIG_INET)
>>
>>> +	/**
>>> +	 * @root_net_port: Root of a red-black tree containing object nodes
>>> +	 * for network port. Once a ruleset is tied to a process (i.e. as a domain),
>>> +	 * this tree is immutable until @usage reaches zero.
>>> +	 */
>>
>> There is some fixes missing from my patch. Please explain everything
>> that you didn't take.
> 
>      Sorry. I did merge your patch manually and did not tell the
> difference here. Will be fixed

You can use git diff to be sure to not miss some parts. BTW, tools such 
as git cherry-pick, read-tree, diff and "add -p" can save you some time.


>>
>>
>>> +	struct rb_root root_net_port;
>>
>>
>> #endif /* IS_ENABLED(CONFIG_INET) */
>>
>> And then all use of root_net_port should be surrounded by the same check.
> 
>     The same - I did not find #if IS_ENABLED(CONFIG_INET) surrounding
> root_net_port in tmp-net (7d6cf40a6f81adf607ad3cc17aaa11e256beeea4)
>>
>> I think it should be OK to keep all other remaining network references
>> though (e.g. access_masks and the ).
> 
>     Ok. Thanks.
>>
>>
>>>    	/**
>>>    	 * @hierarchy: Enables hierarchy identification even when a parent
>>>    	 * domain vanishes.  This is needed for the ptrace protection.
>>> @@ -188,7 +199,8 @@ struct landlock_ruleset {
>>>    };
>>>
>>>    struct landlock_ruleset *
>>> -landlock_create_ruleset(const access_mask_t access_mask);
>>> +landlock_create_ruleset(const access_mask_t access_mask_fs,
>>> +			const access_mask_t access_mask_net);
>>>
>>>    void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
>>>    void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);
>>> @@ -226,6 +238,21 @@ landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
>>>    		(fs_mask << LANDLOCK_SHIFT_ACCESS_FS);
>>>    }
>>>
>>> +/* A helper function to set a network mask. */
>>
>> I already said that this comment is useless, and I removed it in my
>> patch. Please take a closer look at reviews.
> 
>    Sorry. I missed that in your patch. Will be fixed.
>>
>>
>>> +static inline void
>>> +landlock_add_net_access_mask(struct landlock_ruleset *const ruleset,
>>> +			     const access_mask_t net_access_mask,
>>> +			     const u16 layer_level)
>>> +{
>>> +	access_mask_t net_mask = net_access_mask & LANDLOCK_MASK_ACCESS_NET;
>>> +
>>> +	/* Should already be checked in sys_landlock_create_ruleset(). */
>>> +	WARN_ON_ONCE(net_access_mask != net_mask);
>>> +	// TODO: Add tests to check "|=" and not "="
>>> +	ruleset->access_masks[layer_level] |=
>>> +		(net_mask << LANDLOCK_SHIFT_ACCESS_NET);
>>> +}
>>> +
>>>    /* A helper function to get a filesystem mask. */
>>>    static inline access_mask_t
>>>    landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
>>> @@ -236,6 +263,16 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
>>>    	       LANDLOCK_MASK_ACCESS_FS;
>>>    }
>>>
>>> +/* A helper function to get a network mask. */
>>> +static inline access_mask_t
>>> +landlock_get_net_access_mask(const struct landlock_ruleset *const ruleset,
>>> +			     const u16 layer_level)
>>> +{
>>> +	return (ruleset->access_masks[layer_level] >>
>>> +		LANDLOCK_SHIFT_ACCESS_NET) &
>>> +	       LANDLOCK_MASK_ACCESS_NET;
>>> +}
>>> +
>>
>> This hunk doesn't match my patch.
> 
>     Do you mean landlock_get_net_access_mask? If yes, there is no diff
> with your patch here.

I removed useless comments, please do a diff (and look at the changes in 
the commit messages). Some code also moved.


>>
>>
>>>    bool unmask_layers(const struct landlock_rule *const rule,
>>>    		   const access_mask_t access_request,
>>>    		   layer_mask_t (*const layer_masks)[],
>>> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
>>> index ffd5805eddd9..641155f6f6f8 100644
>>> --- a/security/landlock/syscalls.c
>>> +++ b/security/landlock/syscalls.c
>>> @@ -189,8 +189,14 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
>>>    	    LANDLOCK_MASK_ACCESS_FS)
>>>    		return -EINVAL;
>>>
>>> +	/* Checks network content (and 32-bits cast). */
>>> +	if ((ruleset_attr.handled_access_net | LANDLOCK_MASK_ACCESS_NET) !=
>>> +	    LANDLOCK_MASK_ACCESS_NET)
>>> +		return -EINVAL;
>>> +
>>>    	/* Checks arguments and transforms to kernel struct. */
>>> -	ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs);
>>> +	ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs,
>>> +					  ruleset_attr.handled_access_net);
>>>    	if (IS_ERR(ruleset))
>>>    		return PTR_ERR(ruleset);
>>>
>>> --
>>> 2.25.1
>>>
>> .

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