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Message-ID: <9a6ea6ac-525d-e058-5867-0794a99b19a3@huawei.com>
Date: Wed, 4 Jan 2023 14:41:17 +0300
From: "Konstantin Meskhidze (A)" <konstantin.meskhidze@...wei.com>
To: Mickaël Salaün <mic@...ikod.net>
CC: <willemdebruijn.kernel@...il.com>, <gnoack3000@...il.com>,
<linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
<netfilter-devel@...r.kernel.org>, <artem.kuzin@...wei.com>,
Linux API <linux-api@...r.kernel.org>,
"Alejandro Colomar (man-pages)" <alx.manpages@...il.com>
Subject: Re: [PATCH v8 07/12] landlock: Add network rules support
11/17/2022 9:43 PM, Mickaël Salaün пишет:
>
> On 21/10/2022 17:26, Konstantin Meskhidze wrote:
>> This commit adds network rules support in internal landlock functions
>> (presented in ruleset.c) and landlock_create_ruleset syscall.
>
> …in the ruleset management helpers and the landlock_create_ruleset syscall.
>
>
>> Refactors user space API to support network actions. Adds new network
>
> Refactor…
>
>> access flags, network rule and network attributes. Increments Landlock
>
> Increment…
>
>> ABI version.
>>
>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
>> ---
>>
>> 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 | 49 ++++++++++++++
>> security/landlock/limits.h | 6 +-
>> security/landlock/ruleset.c | 55 ++++++++++++++--
>> security/landlock/ruleset.h | 68 ++++++++++++++++----
>> security/landlock/syscalls.c | 13 +++-
>> tools/testing/selftests/landlock/base_test.c | 2 +-
>> 6 files changed, 170 insertions(+), 23 deletions(-)
>>
>> diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
>> index f3223f964691..096b683c6ff3 100644
>> --- a/include/uapi/linux/landlock.h
>> +++ b/include/uapi/linux/landlock.h
>> @@ -31,6 +31,13 @@ struct landlock_ruleset_attr {
>> * this access right.
>> */
>> __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;
>> };
>>
>> /*
>> @@ -54,6 +61,11 @@ 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,
>> };
>>
>> /**
>> @@ -79,6 +91,24 @@ 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;
>
> From an UAPI point of view, I think the port field should be __be16, as
> for sockaddr_in->port and other network-related APIs. This will require
> some kernel changes to please sparse: make C=2 security/landlock/ must
> not print any warning.
I have this errors trying to launch sparse checking:
DESCEND objtool
DESCEND bpf/resolve_btfids
CALL scripts/checksyscalls.sh
CHK kernel/kheaders_data.tar.xz
CC security/landlock/setup.o
CHECK security/landlock/setup.c
./include/asm-generic/rwonce.h:67:16: error: typename in expression
./include/asm-generic/rwonce.h:67:16: error: Expected ) in function call
./include/asm-generic/rwonce.h:67:16: error: got :
./include/linux/list.h:292:16: error: typename in expression
./include/linux/list.h:292:16: error: Expected ) in function call
./include/linux/list.h:292:16: error: got :
....
./include/linux/seqlock.h:682:16: error: Expected ) in function call
./include/linux/seqlock.h:682:16: error: got :
./include/linux/seqlock.h:695:16: error: typename in expression
./include/linux/seqlock.h:695:16: error: Expected ) in function call
./include/linux/seqlock.h:695:16: error: too many errors
Segmentation fault (core dumped)
make[3]: *** [scripts/Makefile.build:250: security/landlock/setup.o]
Error 139
make[3]: *** Deleting file 'security/landlock/setup.o'
make[3]: *** Waiting for unfinished jobs....
Segmentation fault (core dumped)
make[3]: *** [scripts/Makefile.build:250: security/landlock/syscalls.o]
Error 139
make[3]: *** Deleting file 'security/landlock/syscalls.o'
make[2]: *** [scripts/Makefile.build:502: security/landlock] Error 2
make[1]: *** [scripts/Makefile.build:502: security] Error 2
make[1]: *** Waiting for unfinished jobs....
make: *** [Makefile:1994: .] Error 2
>
> Using big-endian values as keys (casted to uintptr_t, not strictly
> __be16) in the rb-tree should not be an issue because there is no port
> range ordering (for now).
>
> A dedicated test should check that endianness is correct, e.g. by using
> different port encoding. This should include passing and failing tests,
> but they should work on all architectures (i.e. big or little endian).
>
>
>> +
>> +} __attribute__((packed));
>> +
>> /**
>> * DOC: fs_access
>> *
>> @@ -173,4 +203,23 @@ struct landlock_path_beneath_attr {
>> #define LANDLOCK_ACCESS_FS_TRUNCATE (1ULL << 14)
>> /* clang-format on */
>>
>> +/**
>> + * 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.
>> + */
>> +/* clang-format off */
>> +#define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0)
>> +#define LANDLOCK_ACCESS_NET_CONNECT_TCP (1ULL << 1)
>> +/* clang-format on */
>> #endif /* _UAPI_LINUX_LANDLOCK_H */
>> 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 c7cf54ba4f6d..9277c1295114 100644
>> --- a/security/landlock/ruleset.c
>> +++ b/security/landlock/ruleset.c
>> @@ -36,6 +36,9 @@ 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;
>> +#if IS_ENABLED(CONFIG_INET)
>> + new_ruleset->root_net_port = RB_ROOT;
>> +#endif /* IS_ENABLED(CONFIG_INET) */
>> new_ruleset->num_layers = num_layers;
>> /*
>> * hierarchy = NULL
>> @@ -46,16 +49,21 @@ 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 +81,10 @@ static inline bool is_object_pointer(const enum landlock_key_type key_type)
>> switch (key_type) {
>> case LANDLOCK_KEY_INODE:
>> return true;
>> +#if IS_ENABLED(CONFIG_INET)
>> + case LANDLOCK_KEY_NET_PORT:
>> + return false;
>> +#endif /* IS_ENABLED(CONFIG_INET) */
>> }
>> WARN_ON_ONCE(1);
>> return false;
>> @@ -126,6 +138,11 @@ static inline struct rb_root *get_root(struct landlock_ruleset *const ruleset,
>> case LANDLOCK_KEY_INODE:
>> root = &ruleset->root_inode;
>> break;
>> +#if IS_ENABLED(CONFIG_INET)
>> + case LANDLOCK_KEY_NET_PORT:
>> + root = &ruleset->root_net_port;
>> + break;
>> +#endif /* IS_ENABLED(CONFIG_INET) */
>> }
>> if (WARN_ON_ONCE(!root))
>> return ERR_PTR(-EINVAL);
>> @@ -154,7 +171,9 @@ 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) +
>
> This is correct but because we are dealing with bitmasks I would prefer
> to use "|" instead of "+".
>
>
>> + (LANDLOCK_MASK_ACCESS_NET
>> + << LANDLOCK_SHIFT_ACCESS_NET));
>> }
>>
>> /**
>> @@ -370,7 +389,12 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
>> err = merge_tree(dst, src, LANDLOCK_KEY_INODE);
>> if (err)
>> goto out_unlock;
>> -
>
> Please keep this newline.
>
>> +#if IS_ENABLED(CONFIG_INET)
>> + /* Merges the @src network port tree. */
>> + err = merge_tree(dst, src, LANDLOCK_KEY_NET_PORT);
>> + if (err)
>> + goto out_unlock;
>> +#endif /* IS_ENABLED(CONFIG_INET) */
>> out_unlock:
>> mutex_unlock(&src->lock);
>> mutex_unlock(&dst->lock);
>> @@ -426,7 +450,12 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
>> err = inherit_tree(parent, child, LANDLOCK_KEY_INODE);
>> if (err)
>> goto out_unlock;
>> -
>
> newline
>
>> +#if IS_ENABLED(CONFIG_INET)
>> + /* Copies the @parent network port tree. */
>> + err = inherit_tree(parent, child, LANDLOCK_KEY_NET_PORT);
>> + if (err)
>> + goto out_unlock;
>> +#endif /* IS_ENABLED(CONFIG_INET) */
>> if (WARN_ON_ONCE(child->num_layers <= parent->num_layers)) {
>> err = -EINVAL;
>> goto out_unlock;
>> @@ -459,6 +488,11 @@ 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);
>> +#if IS_ENABLED(CONFIG_INET)
>> + rbtree_postorder_for_each_entry_safe(freeme, next,
>> + &ruleset->root_net_port, node)
>> + free_rule(freeme, LANDLOCK_KEY_NET_PORT);
>> +#endif /* IS_ENABLED(CONFIG_INET) */
>> put_hierarchy(ruleset->hierarchy);
>> kfree(ruleset);
>> }
>> @@ -637,6 +671,9 @@ get_access_mask_t(const struct landlock_ruleset *const ruleset,
>> * Populates @layer_masks such that for each access right in @access_request,
>> * the bits for all the layers are set where this access right is handled.
>> *
>> + * @layer_masks must contain LANDLOCK_NUM_ACCESS_FS or LANDLOCK_NUM_ACCESS_NET
>> + * elements according to @key_type.
>
> Please include this sentence in the @layer_masks description below.
>
>> + *
>> * @domain: The domain that defines the current restrictions.
>> * @access_request: The requested access rights to check.
>> * @layer_masks: The layer masks to populate.
>
> "It must contain…"
>
>
>> @@ -659,6 +696,12 @@ 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;
>> +#if IS_ENABLED(CONFIG_INET)
>> + case LANDLOCK_KEY_NET_PORT:
>> + get_access_mask = landlock_get_net_access_mask;
>> + num_access = LANDLOCK_NUM_ACCESS_NET;
>> + break;
>> +#endif /* IS_ENABLED(CONFIG_INET) */
>> default:
>> WARN_ON_ONCE(1);
>> return 0;
>> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
>> index d9eb79ea9a89..f272d2cd518c 100644
>> --- a/security/landlock/ruleset.h
>> +++ b/security/landlock/ruleset.h
>> @@ -19,16 +19,20 @@
>> #include "limits.h"
>> #include "object.h"
>>
>> +/* Rule access mask. */
>> typedef u16 access_mask_t;
>> /* Makes sure all filesystem access rights can be stored. */
>> static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
>> +/* Makes sure all network access rights can be stored. */
>> +static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_NET);
>> /* Makes sure for_each_set_bit() and for_each_clear_bit() calls are OK. */
>> static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));
>>
>> /* Ruleset access masks. */
>> -typedef u16 access_masks_t;
>> +typedef u32 access_masks_t;
>
> This type change need to be explained in the commit message.
>
>
>> /* Makes sure all ruleset access rights can be stored. */
>> -static_assert(BITS_PER_TYPE(access_masks_t) >= LANDLOCK_NUM_ACCESS_FS);
>> +static_assert(BITS_PER_TYPE(access_masks_t) >=
>> + LANDLOCK_NUM_ACCESS_FS + LANDLOCK_NUM_ACCESS_NET);
>>
>> typedef u16 layer_mask_t;
>> /* Makes sure all layers can be checked. */
>> @@ -82,6 +86,13 @@ 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) */
>> };
>>
>> /**
>> @@ -156,6 +167,15 @@ 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 &struct
>> + * landlock_rule nodes with network port. Once a ruleset is tied to a
>> + * process (i.e. as a domain), this tree is immutable until @usage
>> + * reaches zero.
>> + */
>> + struct rb_root root_net_port;
>> +#endif /* IS_ENABLED(CONFIG_INET) */
>> /**
>> * @hierarchy: Enables hierarchy identification even when a parent
>> * domain vanishes. This is needed for the ptrace protection.
>> @@ -166,8 +186,8 @@ struct landlock_ruleset {
>> * @work_free: Enables to free a ruleset within a lockless
>> * section. This is only used by
>> * landlock_put_ruleset_deferred() when @usage reaches zero.
>> - * The fields @lock, @usage, @num_rules, @num_layers and
>> - * @access_masks are then unused.
>> + * The fields @lock, @usage, @num_rules, @num_layers,
>> + * @net_access_mask and @access_masks are then unused.
>
> There is no net_access_mask anymore.
> .
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