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Landlock updates for v6.7-rc1 

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Merge tag 'landlock-6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux

Pull landlock updates from Mickaël Salaün:
 "A Landlock ruleset can now handle two new access rights:
  LANDLOCK_ACCESS_NET_BIND_TCP and LANDLOCK_ACCESS_NET_CONNECT_TCP. When
  handled, the related actions are denied unless explicitly allowed by a
  Landlock network rule for a specific port.

  The related patch series has been reviewed for almost two years, it
  has evolved a lot and we now have reached a decent design, code and
  testing. The refactored kernel code and the new test helpers also
  bring the foundation to support more network protocols.

  Test coverage for security/landlock is 92.4% of 710 lines according to
  gcc/gcov-13, and it was 93.1% of 597 lines before this series. The
  decrease in coverage is due to code refactoring to make the ruleset
  management more generic (i.e. dealing with inodes and ports) that also
  added new WARN_ON_ONCE() checks not possible to test from user space.

  syzkaller has been updated accordingly [4], and such patched instance
  (tailored to Landlock) has been running for a month, covering all the
  new network-related code [5]"

Link: https://lore.kernel.org/r/20231026014751.414649-1-konstantin.meskhidze@huawei.com [1]
Link: https://lore.kernel.org/r/CAHC9VhS1wwgH6NNd+cJz4MYogPiRV8NyPDd1yj5SpaxeUB4UVg@mail.gmail.com [2]
Link: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next-history.git/commit/?id=c8dc5ee69d3a [3]
Link: https://github.com/google/syzkaller/pull/4266 [4]
Link: https://storage.googleapis.com/syzbot-assets/82e8608dec36/ci-upstream-linux-next-kasan-gce-root-ab577164.html#security%2flandlock%2fnet.c [5]

* tag 'landlock-6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux:
  selftests/landlock: Add tests for FS topology changes with network rules
  landlock: Document network support
  samples/landlock: Support TCP restrictions
  selftests/landlock: Add network tests
  selftests/landlock: Share enforce_ruleset() helper
  landlock: Support network rules with TCP bind and connect
  landlock: Refactor landlock_add_rule() syscall
  landlock: Refactor layer helpers
  landlock: Move and rename layer helpers
  landlock: Refactor merge/inherit_ruleset helpers
  landlock: Refactor landlock_find_rule/insert_rule helpers
  landlock: Allow FS topology changes for domains without such rule type
  landlock: Make ruleset's access masks more generic
This commit is contained in:
Linus Torvalds 2023-11-03 09:28:53 -10:00
parent 7ab89417ed f12f8f8450
commit 136cc1e1f5
18 changed files with 2967 additions and 352 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

99
Documentation/userspace-api/landlock.rst
View File

@ -8,13 +8,13 @@ Landlock: unprivileged access control
=====================================
:Author: Mickaël Salaün
:Date: October 2022
:Date: October 2023
The goal of Landlock is to enable to restrict ambient rights (e.g. global
filesystem access) for a set of processes. Because Landlock is a stackable
LSM, it makes possible to create safe security sandboxes as new security layers
in addition to the existing system-wide access-controls. This kind of sandbox
is expected to help mitigate the security impact of bugs or
filesystem or network access) for a set of processes. Because Landlock
is a stackable LSM, it makes possible to create safe security sandboxes as new
security layers in addition to the existing system-wide access-controls. This
kind of sandbox is expected to help mitigate the security impact of bugs or
unexpected/malicious behaviors in user space applications. Landlock empowers
any process, including unprivileged ones, to securely restrict themselves.
@ -28,20 +28,34 @@ appropriately <kernel_support>`.
Landlock rules
==============
A Landlock rule describes an action on an object. An object is currently a
file hierarchy, and the related filesystem actions are defined with `access
rights`_. A set of rules is aggregated in a ruleset, which can then restrict
A Landlock rule describes an action on an object which the process intends to
perform. A set of rules is aggregated in a ruleset, which can then restrict
the thread enforcing it, and its future children.
The two existing types of rules are:
Filesystem rules
For these rules, the object is a file hierarchy,
and the related filesystem actions are defined with
`filesystem access rights`.
Network rules (since ABI v4)
For these rules, the object is a TCP port,
and the related actions are defined with `network access rights`.
Defining and enforcing a security policy
----------------------------------------
We first need to define the ruleset that will contain our rules. For this
example, the ruleset will contain rules that only allow read actions, but write
actions will be denied. The ruleset then needs to handle both of these kind of
actions. This is required for backward and forward compatibility (i.e. the
kernel and user space may not know each other's supported restrictions), hence
the need to be explicit about the denied-by-default access rights.
We first need to define the ruleset that will contain our rules.
For this example, the ruleset will contain rules that only allow filesystem
read actions and establish a specific TCP connection. Filesystem write
actions and other TCP actions will be denied.
The ruleset then needs to handle both these kinds of actions. This is
required for backward and forward compatibility (i.e. the kernel and user
space may not know each other's supported restrictions), hence the need
to be explicit about the denied-by-default access rights.
.. code-block:: c
@ -62,6 +76,9 @@ the need to be explicit about the denied-by-default access rights.
LANDLOCK_ACCESS_FS_MAKE_SYM |
LANDLOCK_ACCESS_FS_REFER |
LANDLOCK_ACCESS_FS_TRUNCATE,
.handled_access_net =
LANDLOCK_ACCESS_NET_BIND_TCP |
LANDLOCK_ACCESS_NET_CONNECT_TCP,
};
Because we may not know on which kernel version an application will be
@ -70,9 +87,7 @@ should try to protect users as much as possible whatever the kernel they are
using. To avoid binary enforcement (i.e. either all security features or
none), we can leverage a dedicated Landlock command to get the current version
of the Landlock ABI and adapt the handled accesses. Let's check if we should
remove the ``LANDLOCK_ACCESS_FS_REFER`` or ``LANDLOCK_ACCESS_FS_TRUNCATE``
access rights, which are only supported starting with the second and third
version of the ABI.
remove access rights which are only supported in higher versions of the ABI.
.. code-block:: c
@ -92,6 +107,12 @@ version of the ABI.
case 2:
/* Removes LANDLOCK_ACCESS_FS_TRUNCATE for ABI < 3 */
ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_TRUNCATE;
__attribute__((fallthrough));
case 3:
/* Removes network support for ABI < 4 */
ruleset_attr.handled_access_net &=
~(LANDLOCK_ACCESS_NET_BIND_TCP |
LANDLOCK_ACCESS_NET_CONNECT_TCP);
}
This enables to create an inclusive ruleset that will contain our rules.
@ -143,10 +164,23 @@ for the ruleset creation, by filtering access rights according to the Landlock
ABI version. In this example, this is not required because all of the requested
``allowed_access`` rights are already available in ABI 1.
We now have a ruleset with one rule allowing read access to ``/usr`` while
denying all other handled accesses for the filesystem. The next step is to
restrict the current thread from gaining more privileges (e.g. thanks to a SUID
binary).
For network access-control, we can add a set of rules that allow to use a port
number for a specific action: HTTPS connections.
.. code-block:: c
struct landlock_net_port_attr net_port = {
.allowed_access = LANDLOCK_ACCESS_NET_CONNECT_TCP,
.port = 443,
};
err = landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
&net_port, 0);
The next step is to restrict the current thread from gaining more privileges
(e.g. through a SUID binary). We now have a ruleset with the first rule
allowing read access to ``/usr`` while denying all other handled accesses for
the filesystem, and a second rule allowing HTTPS connections.
.. code-block:: c
@ -355,7 +389,7 @@ Access rights
-------------
.. kernel-doc:: include/uapi/linux/landlock.h
:identifiers: fs_access
:identifiers: fs_access net_access
Creating a new ruleset
----------------------
@ -374,6 +408,7 @@ Extending a ruleset
.. kernel-doc:: include/uapi/linux/landlock.h
:identifiers: landlock_rule_type landlock_path_beneath_attr
landlock_net_port_attr
Enforcing a ruleset
-------------------
@ -387,9 +422,9 @@ Current limitations
Filesystem topology modification
--------------------------------
As for file renaming and linking, a sandboxed thread cannot modify its
filesystem topology, whether via :manpage:`mount(2)` or
:manpage:`pivot_root(2)`. However, :manpage:`chroot(2)` calls are not denied.
Threads sandboxed with filesystem restrictions cannot modify filesystem
topology, whether via :manpage:`mount(2)` or :manpage:`pivot_root(2)`.
However, :manpage:`chroot(2)` calls are not denied.
Special filesystems
-------------------
@ -451,6 +486,14 @@ always allowed when using a kernel that only supports the first or second ABI.
Starting with the Landlock ABI version 3, it is now possible to securely control
truncation thanks to the new ``LANDLOCK_ACCESS_FS_TRUNCATE`` access right.
Network support (ABI < 4)
-------------------------
Starting with the Landlock ABI version 4, it is now possible to restrict TCP
bind and connect actions to only a set of allowed ports thanks to the new
``LANDLOCK_ACCESS_NET_BIND_TCP`` and ``LANDLOCK_ACCESS_NET_CONNECT_TCP``
access rights.
.. _kernel_support:
Kernel support
@ -469,6 +512,12 @@ still enable it by adding ``lsm=landlock,[...]`` to
Documentation/admin-guide/kernel-parameters.rst thanks to the bootloader
configuration.
To be able to explicitly allow TCP operations (e.g., adding a network rule with
``LANDLOCK_ACCESS_NET_BIND_TCP``), the kernel must support TCP
(``CONFIG_INET=y``). Otherwise, sys_landlock_add_rule() returns an
``EAFNOSUPPORT`` error, which can safely be ignored because this kind of TCP
operation is already not possible.
Questions and answers
=====================

55
include/uapi/linux/landlock.h
View File

@ -31,6 +31,12 @@ 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 +60,11 @@ enum landlock_rule_type {
* landlock_path_beneath_attr .
*/
LANDLOCK_RULE_PATH_BENEATH = 1,
/**
* @LANDLOCK_RULE_NET_PORT: Type of a &struct
* landlock_net_port_attr .
*/
LANDLOCK_RULE_NET_PORT,
};
/**
@ -79,6 +90,31 @@ struct landlock_path_beneath_attr {
*/
} __attribute__((packed));
/**
* struct landlock_net_port_attr - Network port definition
*
* Argument of sys_landlock_add_rule().
*/
struct landlock_net_port_attr {
/**
* @allowed_access: Bitmask of allowed access network for a port
* (cf. `Network flags`_).
*/
__u64 allowed_access;
/**
* @port: Network port in host endianness.
*
* It should be noted that port 0 passed to :manpage:`bind(2)` will
* bind to an available port from a specific port range. This can be
* configured thanks to the ``/proc/sys/net/ipv4/ip_local_port_range``
* sysctl (also used for IPv6). A Landlock rule with port 0 and the
* ``LANDLOCK_ACCESS_NET_BIND_TCP`` right means that requesting to bind
* on port 0 is allowed and it will automatically translate to binding
* on the related port range.
*/
__u64 port;
};
/**
* DOC: fs_access
*
@ -189,4 +225,23 @@ 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. This is supported since the Landlock ABI version 4.
*
* 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 */

115
samples/landlock/sandboxer.c
View File

@ -8,6 +8,8 @@
*/
#define _GNU_SOURCE
#define __SANE_USERSPACE_TYPES__
#include <arpa/inet.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/landlock.h>
@ -51,7 +53,9 @@ static inline int landlock_restrict_self(const int ruleset_fd,
#define ENV_FS_RO_NAME "LL_FS_RO"
#define ENV_FS_RW_NAME "LL_FS_RW"
#define ENV_PATH_TOKEN ":"
#define ENV_TCP_BIND_NAME "LL_TCP_BIND"
#define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT"
#define ENV_DELIMITER ":"
static int parse_path(char *env_path, const char ***const path_list)
{
@ -60,13 +64,13 @@ static int parse_path(char *env_path, const char ***const path_list)
if (env_path) {
num_paths++;
for (i = 0; env_path[i]; i++) {
if (env_path[i] == ENV_PATH_TOKEN[0])
if (env_path[i] == ENV_DELIMITER[0])
num_paths++;
}
}
*path_list = malloc(num_paths * sizeof(**path_list));
for (i = 0; i < num_paths; i++)
(*path_list)[i] = strsep(&env_path, ENV_PATH_TOKEN);
(*path_list)[i] = strsep(&env_path, ENV_DELIMITER);
return num_paths;
}
@ -81,8 +85,8 @@ static int parse_path(char *env_path, const char ***const path_list)
/* clang-format on */
static int populate_ruleset(const char *const env_var, const int ruleset_fd,
const __u64 allowed_access)
static int populate_ruleset_fs(const char *const env_var, const int ruleset_fd,
const __u64 allowed_access)
{
int num_paths, i, ret = 1;
char *env_path_name;
@ -143,6 +147,39 @@ out_free_name:
return ret;
}
static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
const __u64 allowed_access)
{
int ret = 1;
char *env_port_name, *strport;
struct landlock_net_port_attr net_port = {
.allowed_access = allowed_access,
.port = 0,
};
env_port_name = getenv(env_var);
if (!env_port_name)
return 0;
env_port_name = strdup(env_port_name);
unsetenv(env_var);
while ((strport = strsep(&env_port_name, ENV_DELIMITER))) {
net_port.port = atoi(strport);
if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
&net_port, 0)) {
fprintf(stderr,
"Failed to update the ruleset with port \"%llu\": %s\n",
net_port.port, strerror(errno));
goto out_free_name;
}
}
ret = 0;
out_free_name:
free(env_port_name);
return ret;
}
/* clang-format off */
#define ACCESS_FS_ROUGHLY_READ ( \
@ -166,39 +203,58 @@ out_free_name:
/* clang-format on */
#define LANDLOCK_ABI_LAST 3
#define LANDLOCK_ABI_LAST 4
int main(const int argc, char *const argv[], char *const *const envp)
{
const char *cmd_path;
char *const *cmd_argv;
int ruleset_fd, abi;
char *env_port_name;
__u64 access_fs_ro = ACCESS_FS_ROUGHLY_READ,
access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE;
struct landlock_ruleset_attr ruleset_attr = {
.handled_access_fs = access_fs_rw,
.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
LANDLOCK_ACCESS_NET_CONNECT_TCP,
};
if (argc < 2) {
fprintf(stderr,
"usage: %s=\"...\" %s=\"...\" %s <cmd> [args]...\n\n",
ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);
"usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\"%s "
"<cmd> [args]...\n\n",
ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
ENV_TCP_CONNECT_NAME, argv[0]);
fprintf(stderr,
"Launch a command in a restricted environment.\n\n");
fprintf(stderr, "Environment variables containing paths, "
"each separated by a colon:\n");
fprintf(stderr,
"Environment variables containing paths and ports "
"each separated by a colon:\n");
fprintf(stderr,
"* %s: list of paths allowed to be used in a read-only way.\n",
ENV_FS_RO_NAME);
fprintf(stderr,
"* %s: list of paths allowed to be used in a read-write way.\n",
"* %s: list of paths allowed to be used in a read-write way.\n\n",
ENV_FS_RW_NAME);
fprintf(stderr,
"Environment variables containing ports are optional "
"and could be skipped.\n");
fprintf(stderr,
"* %s: list of ports allowed to bind (server).\n",
ENV_TCP_BIND_NAME);
fprintf(stderr,
"* %s: list of ports allowed to connect (client).\n",
ENV_TCP_CONNECT_NAME);
fprintf(stderr,
"\nexample:\n"
"%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" "
"%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
"%s=\"9418\" "
"%s=\"80:443\" "
"%s bash -i\n\n",
ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);
ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
ENV_TCP_CONNECT_NAME, argv[0]);
fprintf(stderr,
"This sandboxer can use Landlock features "
"up to ABI version %d.\n",
@ -255,7 +311,12 @@ int main(const int argc, char *const argv[], char *const *const envp)
case 2:
/* Removes LANDLOCK_ACCESS_FS_TRUNCATE for ABI < 3 */
ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_TRUNCATE;
__attribute__((fallthrough));
case 3:
/* Removes network support for ABI < 4 */
ruleset_attr.handled_access_net &=
~(LANDLOCK_ACCESS_NET_BIND_TCP |
LANDLOCK_ACCESS_NET_CONNECT_TCP);
fprintf(stderr,
"Hint: You should update the running kernel "
"to leverage Landlock features "
@ -274,18 +335,42 @@ int main(const int argc, char *const argv[], char *const *const envp)
access_fs_ro &= ruleset_attr.handled_access_fs;
access_fs_rw &= ruleset_attr.handled_access_fs;
/* Removes bind access attribute if not supported by a user. */
env_port_name = getenv(ENV_TCP_BIND_NAME);
if (!env_port_name) {
ruleset_attr.handled_access_net &=
~LANDLOCK_ACCESS_NET_BIND_TCP;
}
/* Removes connect access attribute if not supported by a user. */
env_port_name = getenv(ENV_TCP_CONNECT_NAME);
if (!env_port_name) {
ruleset_attr.handled_access_net &=
~LANDLOCK_ACCESS_NET_CONNECT_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(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) {
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_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)) {
perror("Failed to restrict privileges");
goto err_close_ruleset;

1
security/landlock/Kconfig
View File

@ -3,6 +3,7 @@
config SECURITY_LANDLOCK
bool "Landlock support"
depends on SECURITY
select SECURITY_NETWORK
select SECURITY_PATH
help
Landlock is a sandboxing mechanism that enables processes to restrict

2
security/landlock/Makefile
View File

@ -2,3 +2,5 @@ obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
landlock-y := setup.o syscalls.o object.o ruleset.o \
cred.o ptrace.o fs.o
landlock-$(CONFIG_INET) += net.o

232
security/landlock/fs.c
View File

@ -150,16 +150,6 @@ retry:
LANDLOCK_ACCESS_FS_TRUNCATE)
/* clang-format on */
/*
* All access rights that are denied by default whether they are handled or not
* by a ruleset/layer. This must be ORed with all ruleset->fs_access_masks[]
* entries when we need to get the absolute handled access masks.
*/
/* clang-format off */
#define ACCESS_INITIALLY_DENIED ( \
LANDLOCK_ACCESS_FS_REFER)
/* clang-format on */
/*
* @path: Should have been checked by get_path_from_fd().
*/
@ -168,7 +158,9 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
access_mask_t access_rights)
{
int err;
struct landlock_object *object;
struct landlock_id id = {
.type = LANDLOCK_KEY_INODE,
};
/* Files only get access rights that make sense. */
if (!d_is_dir(path->dentry) &&
@ -178,20 +170,19 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
return -EINVAL;
/* Transforms relative access rights to absolute ones. */
access_rights |=
LANDLOCK_MASK_ACCESS_FS &
~(ruleset->fs_access_masks[0] | ACCESS_INITIALLY_DENIED);
object = get_inode_object(d_backing_inode(path->dentry));
if (IS_ERR(object))
return PTR_ERR(object);
access_rights |= LANDLOCK_MASK_ACCESS_FS &
~landlock_get_fs_access_mask(ruleset, 0);
id.key.object = get_inode_object(d_backing_inode(path->dentry));
if (IS_ERR(id.key.object))
return PTR_ERR(id.key.object);
mutex_lock(&ruleset->lock);
err = landlock_insert_rule(ruleset, object, access_rights);
err = landlock_insert_rule(ruleset, id, access_rights);
mutex_unlock(&ruleset->lock);
/*
* No need to check for an error because landlock_insert_rule()
* increments the refcount for the new object if needed.
*/
landlock_put_object(object);
landlock_put_object(id.key.object);
return err;
}
@ -208,6 +199,9 @@ find_rule(const struct landlock_ruleset *const domain,
{
const struct landlock_rule *rule;
const struct inode *inode;
struct landlock_id id = {
.type = LANDLOCK_KEY_INODE,
};
/* Ignores nonexistent leafs. */
if (d_is_negative(dentry))
@ -215,66 +209,12 @@ find_rule(const struct landlock_ruleset *const domain,
inode = d_backing_inode(dentry);
rcu_read_lock();
rule = landlock_find_rule(
domain, rcu_dereference(landlock_inode(inode)->object));
id.key.object = rcu_dereference(landlock_inode(inode)->object);
rule = landlock_find_rule(domain, id);
rcu_read_unlock();
return rule;
}
/*
* @layer_masks is read and may be updated according to the access request and
* the matching rule.
*
* Returns true if the request is allowed (i.e. relevant layer masks for the
* request are empty).
*/
static inline bool
unmask_layers(const struct landlock_rule *const rule,
const access_mask_t access_request,
layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
{
size_t layer_level;
if (!access_request || !layer_masks)
return true;
if (!rule)
return false;
/*
* An access is granted if, for each policy layer, at least one rule
* encountered on the pathwalk grants the requested access,
* regardless of its position in the layer stack. We must then check
* the remaining layers for each inode, from the first added layer to
* the last one. When there is multiple requested accesses, for each
* policy layer, the full set of requested accesses may not be granted
* by only one rule, but by the union (binary OR) of multiple rules.
* E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
*/
for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
const struct landlock_layer *const layer =
&rule->layers[layer_level];
const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
const unsigned long access_req = access_request;
unsigned long access_bit;
bool is_empty;
/*
* Records in @layer_masks which layer grants access to each
* requested access.
*/
is_empty = true;
for_each_set_bit(access_bit, &access_req,
ARRAY_SIZE(*layer_masks)) {
if (layer->access & BIT_ULL(access_bit))
(*layer_masks)[access_bit] &= ~layer_bit;
is_empty = is_empty && !(*layer_masks)[access_bit];
}
if (is_empty)
return true;
}
return false;
}
/*
* Allows access to pseudo filesystems that will never be mountable (e.g.
* sockfs, pipefs), but can still be reachable through
@ -287,64 +227,35 @@ static inline bool is_nouser_or_private(const struct dentry *dentry)
unlikely(IS_PRIVATE(d_backing_inode(dentry))));
}
static inline access_mask_t
get_handled_accesses(const struct landlock_ruleset *const domain)
static access_mask_t
get_raw_handled_fs_accesses(const struct landlock_ruleset *const domain)
{
access_mask_t access_dom = ACCESS_INITIALLY_DENIED;
access_mask_t access_dom = 0;
size_t layer_level;
for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
access_dom |= domain->fs_access_masks[layer_level];
return access_dom & LANDLOCK_MASK_ACCESS_FS;
access_dom |=
landlock_get_raw_fs_access_mask(domain, layer_level);
return access_dom;
}
/**
* init_layer_masks - Initialize layer masks from an access request
*
* 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.
*
* @domain: The domain that defines the current restrictions.
* @access_request: The requested access rights to check.
* @layer_masks: The layer masks to populate.
*
* Returns: An access mask where each access right bit is set which is handled
* in any of the active layers in @domain.
*/
static inline access_mask_t
init_layer_masks(const struct landlock_ruleset *const domain,
const access_mask_t access_request,
layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
static access_mask_t
get_handled_fs_accesses(const struct landlock_ruleset *const domain)
{
access_mask_t handled_accesses = 0;
size_t layer_level;
/* Handles all initially denied by default access rights. */
return get_raw_handled_fs_accesses(domain) |
LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
}
memset(layer_masks, 0, sizeof(*layer_masks));
/* An empty access request can happen because of O_WRONLY | O_RDWR. */
if (!access_request)
return 0;
static const struct landlock_ruleset *get_current_fs_domain(void)
{
const struct landlock_ruleset *const dom =
landlock_get_current_domain();
/* Saves all handled accesses per layer. */
for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
const unsigned long access_req = access_request;
unsigned long access_bit;
if (!dom || !get_raw_handled_fs_accesses(dom))
return NULL;
for_each_set_bit(access_bit, &access_req,
ARRAY_SIZE(*layer_masks)) {
/*
* Artificially handles all initially denied by default
* access rights.
*/
if (BIT_ULL(access_bit) &
(domain->fs_access_masks[layer_level] |
ACCESS_INITIALLY_DENIED)) {
(*layer_masks)[access_bit] |=
BIT_ULL(layer_level);
handled_accesses |= BIT_ULL(access_bit);
}
}
}
return handled_accesses;
return dom;
}
/*
@ -519,7 +430,7 @@ static bool is_access_to_paths_allowed(
* a superset of the meaningful requested accesses).
*/
access_masked_parent1 = access_masked_parent2 =
get_handled_accesses(domain);
get_handled_fs_accesses(domain);
is_dom_check = true;
} else {
if (WARN_ON_ONCE(dentry_child1 || dentry_child2))
@ -531,18 +442,22 @@ static bool is_access_to_paths_allowed(
}
if (unlikely(dentry_child1)) {
unmask_layers(find_rule(domain, dentry_child1),
init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
&_layer_masks_child1),
&_layer_masks_child1);
landlock_unmask_layers(
find_rule(domain, dentry_child1),
landlock_init_layer_masks(
domain, LANDLOCK_MASK_ACCESS_FS,
&_layer_masks_child1, LANDLOCK_KEY_INODE),
&_layer_masks_child1, ARRAY_SIZE(_layer_masks_child1));
layer_masks_child1 = &_layer_masks_child1;
child1_is_directory = d_is_dir(dentry_child1);
}
if (unlikely(dentry_child2)) {
unmask_layers(find_rule(domain, dentry_child2),
init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
&_layer_masks_child2),
&_layer_masks_child2);
landlock_unmask_layers(
find_rule(domain, dentry_child2),
landlock_init_layer_masks(
domain, LANDLOCK_MASK_ACCESS_FS,
&_layer_masks_child2, LANDLOCK_KEY_INODE),
&_layer_masks_child2, ARRAY_SIZE(_layer_masks_child2));
layer_masks_child2 = &_layer_masks_child2;
child2_is_directory = d_is_dir(dentry_child2);
}
@ -594,15 +509,16 @@ static bool is_access_to_paths_allowed(
}
rule = find_rule(domain, walker_path.dentry);
allowed_parent1 = unmask_layers(rule, access_masked_parent1,
layer_masks_parent1);
allowed_parent2 = unmask_layers(rule, access_masked_parent2,
layer_masks_parent2);
allowed_parent1 = landlock_unmask_layers(
rule, access_masked_parent1, layer_masks_parent1,
ARRAY_SIZE(*layer_masks_parent1));
allowed_parent2 = landlock_unmask_layers(
rule, access_masked_parent2, layer_masks_parent2,
ARRAY_SIZE(*layer_masks_parent2));
/* Stops when a rule from each layer grants access. */
if (allowed_parent1 && allowed_parent2)
break;
jump_up:
if (walker_path.dentry == walker_path.mnt->mnt_root) {
if (follow_up(&walker_path)) {
@ -641,7 +557,8 @@ static inline int check_access_path(const struct landlock_ruleset *const domain,
{
layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
access_request = init_layer_masks(domain, access_request, &layer_masks);
access_request = landlock_init_layer_masks(
domain, access_request, &layer_masks, LANDLOCK_KEY_INODE);
if (is_access_to_paths_allowed(domain, path, access_request,
&layer_masks, NULL, 0, NULL, NULL))
return 0;
@ -651,8 +568,7 @@ static inline int check_access_path(const struct landlock_ruleset *const domain,
static inline int current_check_access_path(const struct path *const path,
const access_mask_t access_request)
{
const struct landlock_ruleset *const dom =
landlock_get_current_domain();
const struct landlock_ruleset *const dom = get_current_fs_domain();
if (!dom)
return 0;
@ -727,16 +643,18 @@ static bool collect_domain_accesses(
if (is_nouser_or_private(dir))
return true;
access_dom = init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
layer_masks_dom);
access_dom = landlock_init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
layer_masks_dom,
LANDLOCK_KEY_INODE);
dget(dir);
while (true) {
struct dentry *parent_dentry;
/* Gets all layers allowing all domain accesses. */
if (unmask_layers(find_rule(domain, dir), access_dom,
layer_masks_dom)) {
if (landlock_unmask_layers(find_rule(domain, dir), access_dom,
layer_masks_dom,
ARRAY_SIZE(*layer_masks_dom))) {
/*
* Stops when all handled accesses are allowed by at
* least one rule in each layer.
@ -815,8 +733,7 @@ static int current_check_refer_path(struct dentry *const old_dentry,
struct dentry *const new_dentry,
const bool removable, const bool exchange)
{
const struct landlock_ruleset *const dom =
landlock_get_current_domain();
const struct landlock_ruleset *const dom = get_current_fs_domain();
bool allow_parent1, allow_parent2;
access_mask_t access_request_parent1, access_request_parent2;
struct path mnt_dir;
@ -850,9 +767,9 @@ static int current_check_refer_path(struct dentry *const old_dentry,
* The LANDLOCK_ACCESS_FS_REFER access right is not required
* for same-directory referer (i.e. no reparenting).
*/
access_request_parent1 = init_layer_masks(
access_request_parent1 = landlock_init_layer_masks(
dom, access_request_parent1 | access_request_parent2,
&layer_masks_parent1);
&layer_masks_parent1, LANDLOCK_KEY_INODE);
if (is_access_to_paths_allowed(
dom, new_dir, access_request_parent1,
&layer_masks_parent1, NULL, 0, NULL, NULL))
@ -1050,7 +967,7 @@ static int hook_sb_mount(const char *const dev_name,
const struct path *const path, const char *const type,
const unsigned long flags, void *const data)
{
if (!landlock_get_current_domain())
if (!get_current_fs_domain())
return 0;
return -EPERM;
}
@ -1058,7 +975,7 @@ static int hook_sb_mount(const char *const dev_name,
static int hook_move_mount(const struct path *const from_path,
const struct path *const to_path)
{
if (!landlock_get_current_domain())
if (!get_current_fs_domain())
return 0;
return -EPERM;
}
@ -1069,14 +986,14 @@ static int hook_move_mount(const struct path *const from_path,
*/
static int hook_sb_umount(struct vfsmount *const mnt, const int flags)
{
if (!landlock_get_current_domain())
if (!get_current_fs_domain())
return 0;
return -EPERM;
}
static int hook_sb_remount(struct super_block *const sb, void *const mnt_opts)
{
if (!landlock_get_current_domain())
if (!get_current_fs_domain())
return 0;
return -EPERM;
}
@ -1092,7 +1009,7 @@ static int hook_sb_remount(struct super_block *const sb, void *const mnt_opts)
static int hook_sb_pivotroot(const struct path *const old_path,
const struct path *const new_path)
{
if (!landlock_get_current_domain())
if (!get_current_fs_domain())
return 0;
return -EPERM;
}
@ -1128,8 +1045,7 @@ static int hook_path_mknod(const struct path *const dir,
struct dentry *const dentry, const umode_t mode,
const unsigned int dev)
{
const struct landlock_ruleset *const dom =
landlock_get_current_domain();
const struct landlock_ruleset *const dom = get_current_fs_domain();
if (!dom)
return 0;
@ -1208,8 +1124,7 @@ static int hook_file_open(struct file *const file)
layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
access_mask_t open_access_request, full_access_request, allowed_access;
const access_mask_t optional_access = LANDLOCK_ACCESS_FS_TRUNCATE;
const struct landlock_ruleset *const dom =
landlock_get_current_domain();
const struct landlock_ruleset *const dom = get_current_fs_domain();
if (!dom)
return 0;
@ -1229,7 +1144,8 @@ static int hook_file_open(struct file *const file)
if (is_access_to_paths_allowed(
dom, &file->f_path,
init_layer_masks(dom, full_access_request, &layer_masks),
landlock_init_layer_masks(dom, full_access_request,
&layer_masks, LANDLOCK_KEY_INODE),
&layer_masks, NULL, 0, NULL, NULL)) {
allowed_access = full_access_request;
} else {

6
security/landlock/limits.h
View File

@ -21,6 +21,12 @@
#define LANDLOCK_LAST_ACCESS_FS LANDLOCK_ACCESS_FS_TRUNCATE
#define LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
#define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS)
#define LANDLOCK_SHIFT_ACCESS_FS 0
#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 */

200
security/landlock/net.c Normal file
View File

@ -0,0 +1,200 @@
// SPDX-License-Identifier: GPL-2.0-only
/*
* Landlock LSM - Network management and hooks
*
* Copyright © 2022-2023 Huawei Tech. Co., Ltd.
* Copyright © 2022-2023 Microsoft Corporation
*/
#include <linux/in.h>
#include <linux/net.h>
#include <linux/socket.h>
#include <net/ipv6.h>
#include "common.h"
#include "cred.h"
#include "limits.h"
#include "net.h"
#include "ruleset.h"
int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
const u16 port, access_mask_t access_rights)
{
int err;
const struct landlock_id id = {
.key.data = (__force uintptr_t)htons(port),
.type = LANDLOCK_KEY_NET_PORT,
};
BUILD_BUG_ON(sizeof(port) > sizeof(id.key.data));
/* Transforms relative access rights to absolute ones. */
access_rights |= LANDLOCK_MASK_ACCESS_NET &
~landlock_get_net_access_mask(ruleset, 0);
mutex_lock(&ruleset->lock);
err = landlock_insert_rule(ruleset, id, access_rights);
mutex_unlock(&ruleset->lock);
return err;
}
static access_mask_t
get_raw_handled_net_accesses(const struct landlock_ruleset *const domain)
{
access_mask_t access_dom = 0;
size_t layer_level;
for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
access_dom |= landlock_get_net_access_mask(domain, layer_level);
return access_dom;
}
static const struct landlock_ruleset *get_current_net_domain(void)
{
const struct landlock_ruleset *const dom =
landlock_get_current_domain();
if (!dom || !get_raw_handled_net_accesses(dom))
return NULL;
return dom;
}
static int current_check_access_socket(struct socket *const sock,
struct sockaddr *const address,
const int addrlen,
const access_mask_t access_request)
{
__be16 port;
layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {};
const struct landlock_rule *rule;
access_mask_t handled_access;
struct landlock_id id = {
.type = LANDLOCK_KEY_NET_PORT,
};
const struct landlock_ruleset *const dom = get_current_net_domain();
if (!dom)
return 0;
if (WARN_ON_ONCE(dom->num_layers < 1))
return -EACCES;
/* Checks if it's a (potential) TCP socket. */
if (sock->type != SOCK_STREAM)
return 0;
/* Checks for minimal header length to safely read sa_family. */
if (addrlen < offsetofend(typeof(*address), sa_family))
return -EINVAL;
switch (address->sa_family) {
case AF_UNSPEC:
case AF_INET:
if (addrlen < sizeof(struct sockaddr_in))
return -EINVAL;
port = ((struct sockaddr_in *)address)->sin_port;
break;
#if IS_ENABLED(CONFIG_IPV6)
case AF_INET6:
if (addrlen < SIN6_LEN_RFC2133)
return -EINVAL;
port = ((struct sockaddr_in6 *)address)->sin6_port;
break;
#endif /* IS_ENABLED(CONFIG_IPV6) */
default:
return 0;
}
/* Specific AF_UNSPEC handling. */
if (address->sa_family == AF_UNSPEC) {
/*
* Connecting to an address with AF_UNSPEC dissolves the TCP
* association, which have the same effect as closing the
* connection while retaining the socket object (i.e., the file
* descriptor). As for dropping privileges, closing
* connections is always allowed.
*
* For a TCP access control system, this request is legitimate.
* Let the network stack handle potential inconsistencies and
* return -EINVAL if needed.
*/
if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP)
return 0;
/*
* For compatibility reason, accept AF_UNSPEC for bind
* accesses (mapped to AF_INET) only if the address is
* INADDR_ANY (cf. __inet_bind). Checking the address is
* required to not wrongfully return -EACCES instead of
* -EAFNOSUPPORT.
*
* We could return 0 and let the network stack handle these
* checks, but it is safer to return a proper error and test
* consistency thanks to kselftest.
*/
if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
/* addrlen has already been checked for AF_UNSPEC. */
const struct sockaddr_in *const sockaddr =
(struct sockaddr_in *)address;
if (sock->sk->__sk_common.skc_family != AF_INET)
return -EINVAL;
if (sockaddr->sin_addr.s_addr != htonl(INADDR_ANY))
return -EAFNOSUPPORT;
}
} else {
/*
* Checks sa_family consistency to not wrongfully return
* -EACCES instead of -EINVAL. Valid sa_family changes are
* only (from AF_INET or AF_INET6) to AF_UNSPEC.
*
* We could return 0 and let the network stack handle this
* check, but it is safer to return a proper error and test
* consistency thanks to kselftest.
*/
if (address->sa_family != sock->sk->__sk_common.skc_family)
return -EINVAL;
}
id.key.data = (__force uintptr_t)port;
BUILD_BUG_ON(sizeof(port) > sizeof(id.key.data));
rule = landlock_find_rule(dom, id);
handled_access = landlock_init_layer_masks(
dom, access_request, &layer_masks, LANDLOCK_KEY_NET_PORT);
if (landlock_unmask_layers(rule, handled_access, &layer_masks,
ARRAY_SIZE(layer_masks)))
return 0;
return -EACCES;
}
static int hook_socket_bind(struct socket *const sock,
struct sockaddr *const address, const int addrlen)
{
return current_check_access_socket(sock, address, addrlen,
LANDLOCK_ACCESS_NET_BIND_TCP);
}
static int hook_socket_connect(struct socket *const sock,
struct sockaddr *const address,
const int addrlen)
{
return current_check_access_socket(sock, address, addrlen,
LANDLOCK_ACCESS_NET_CONNECT_TCP);
}
static struct security_hook_list landlock_hooks[] __ro_after_init = {
LSM_HOOK_INIT(socket_bind, hook_socket_bind),
LSM_HOOK_INIT(socket_connect, hook_socket_connect),
};
__init void landlock_add_net_hooks(void)
{
security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
LANDLOCK_NAME);
}

33
security/landlock/net.h Normal file
View File

@ -0,0 +1,33 @@
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Landlock LSM - Network management and hooks
*
* Copyright © 2022-2023 Huawei Tech. Co., Ltd.
*/
#ifndef _SECURITY_LANDLOCK_NET_H
#define _SECURITY_LANDLOCK_NET_H
#include "common.h"
#include "ruleset.h"
#include "setup.h"
#if IS_ENABLED(CONFIG_INET)
__init void landlock_add_net_hooks(void);
int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
const u16 port, access_mask_t access_rights);
#else /* IS_ENABLED(CONFIG_INET) */
static inline void landlock_add_net_hooks(void)
{
}
static inline int
landlock_append_net_rule(struct landlock_ruleset *const ruleset, const u16 port,
access_mask_t access_rights)
{
return -EAFNOSUPPORT;
}
#endif /* IS_ENABLED(CONFIG_INET) */
#endif /* _SECURITY_LANDLOCK_NET_H */

405
security/landlock/ruleset.c
View File

@ -29,33 +29,43 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
struct landlock_ruleset *new_ruleset;
new_ruleset =
kzalloc(struct_size(new_ruleset, fs_access_masks, num_layers),
kzalloc(struct_size(new_ruleset, access_masks, num_layers),
GFP_KERNEL_ACCOUNT);
if (!new_ruleset)
return ERR_PTR(-ENOMEM);
refcount_set(&new_ruleset->usage, 1);
mutex_init(&new_ruleset->lock);
new_ruleset->root = RB_ROOT;
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
* num_rules = 0
* fs_access_masks[] = 0
* access_masks[] = 0
*/
return new_ruleset;
}
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))
new_ruleset->fs_access_masks[0] = fs_access_mask;
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;
}
@ -68,8 +78,25 @@ static void build_check_rule(void)
BUILD_BUG_ON(rule.num_layers < LANDLOCK_MAX_NUM_LAYERS);
}
static 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) */
default:
WARN_ON_ONCE(1);
return false;
}
}
static struct landlock_rule *
create_rule(struct landlock_object *const object,
create_rule(const struct landlock_id id,
const struct landlock_layer (*const layers)[], const u32 num_layers,
const struct landlock_layer *const new_layer)
{
@ -90,8 +117,13 @@ create_rule(struct landlock_object *const object,
if (!new_rule)
return ERR_PTR(-ENOMEM);
RB_CLEAR_NODE(&new_rule->node);
landlock_get_object(object);
new_rule->object = object;
if (is_object_pointer(id.type)) {
/* This should be catched by insert_rule(). */
WARN_ON_ONCE(!id.key.object);
landlock_get_object(id.key.object);
}
new_rule->key = id.key;
new_rule->num_layers = new_num_layers;
/* Copies the original layer stack. */
memcpy(new_rule->layers, layers,
@ -102,12 +134,32 @@ create_rule(struct landlock_object *const object,
return new_rule;
}
static void free_rule(struct landlock_rule *const rule)
static struct rb_root *get_root(struct landlock_ruleset *const ruleset,
const enum landlock_key_type key_type)
{
switch (key_type) {
case LANDLOCK_KEY_INODE:
return &ruleset->root_inode;
#if IS_ENABLED(CONFIG_INET)
case LANDLOCK_KEY_NET_PORT:
return &ruleset->root_net_port;
#endif /* IS_ENABLED(CONFIG_INET) */
default:
WARN_ON_ONCE(1);
return ERR_PTR(-EINVAL);
}
}
static void free_rule(struct landlock_rule *const rule,
const enum landlock_key_type key_type)
{
might_sleep();
if (!rule)
return;
landlock_put_object(rule->object);
if (is_object_pointer(key_type))
landlock_put_object(rule->key.object);
kfree(rule);
}
@ -117,19 +169,21 @@ static void build_check_ruleset(void)
.num_rules = ~0,
.num_layers = ~0,
};
typeof(ruleset.fs_access_masks[0]) fs_access_mask = ~0;
typeof(ruleset.access_masks[0]) access_masks = ~0;
BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
BUILD_BUG_ON(fs_access_mask < LANDLOCK_MASK_ACCESS_FS);
BUILD_BUG_ON(access_masks <
((LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS) |
(LANDLOCK_MASK_ACCESS_NET << LANDLOCK_SHIFT_ACCESS_NET)));
}
/**
* insert_rule - Create and insert a rule in a ruleset
*
* @ruleset: The ruleset to be updated.
* @object: The object to build the new rule with. The underlying kernel
* object must be held by the caller.
* @id: The ID to build the new rule with. The underlying kernel object, if
* any, must be held by the caller.
* @layers: One or multiple layers to be copied into the new rule.
* @num_layers: The number of @layers entries.
*
@ -143,26 +197,35 @@ static void build_check_ruleset(void)
* access rights.
*/
static int insert_rule(struct landlock_ruleset *const ruleset,
struct landlock_object *const object,
const struct landlock_id id,
const struct landlock_layer (*const layers)[],
size_t num_layers)
const size_t num_layers)
{
struct rb_node **walker_node;
struct rb_node *parent_node = NULL;
struct landlock_rule *new_rule;
struct rb_root *root;
might_sleep();
lockdep_assert_held(&ruleset->lock);
if (WARN_ON_ONCE(!object || !layers))
if (WARN_ON_ONCE(!layers))
return -ENOENT;
walker_node = &(ruleset->root.rb_node);
if (is_object_pointer(id.type) && WARN_ON_ONCE(!id.key.object))
return -ENOENT;
root = get_root(ruleset, id.type);
if (IS_ERR(root))
return PTR_ERR(root);
walker_node = &root->rb_node;
while (*walker_node) {
struct landlock_rule *const this =
rb_entry(*walker_node, struct landlock_rule, node);
if (this->object != object) {
if (this->key.data != id.key.data) {
parent_node = *walker_node;
if (this->object < object)
if (this->key.data < id.key.data)
walker_node = &((*walker_node)->rb_right);
else
walker_node = &((*walker_node)->rb_left);
@ -194,24 +257,24 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
* Intersects access rights when it is a merge between a
* ruleset and a domain.
*/
new_rule = create_rule(object, &this->layers, this->num_layers,
new_rule = create_rule(id, &this->layers, this->num_layers,
&(*layers)[0]);
if (IS_ERR(new_rule))
return PTR_ERR(new_rule);
rb_replace_node(&this->node, &new_rule->node, &ruleset->root);
free_rule(this);
rb_replace_node(&this->node, &new_rule->node, root);
free_rule(this, id.type);
return 0;
}
/* There is no match for @object. */
/* There is no match for @id. */
build_check_ruleset();
if (ruleset->num_rules >= LANDLOCK_MAX_NUM_RULES)
return -E2BIG;
new_rule = create_rule(object, layers, num_layers, NULL);
new_rule = create_rule(id, layers, num_layers, NULL);
if (IS_ERR(new_rule))
return PTR_ERR(new_rule);
rb_link_node(&new_rule->node, parent_node, walker_node);
rb_insert_color(&new_rule->node, &ruleset->root);
rb_insert_color(&new_rule->node, root);
ruleset->num_rules++;
return 0;
}
@ -229,7 +292,7 @@ static void build_check_layer(void)
/* @ruleset must be locked by the caller. */
int landlock_insert_rule(struct landlock_ruleset *const ruleset,
struct landlock_object *const object,
const struct landlock_id id,
const access_mask_t access)
{
struct landlock_layer layers[] = { {
@ -239,7 +302,7 @@ int landlock_insert_rule(struct landlock_ruleset *const ruleset,
} };
build_check_layer();
return insert_rule(ruleset, object, &layers, ARRAY_SIZE(layers));
return insert_rule(ruleset, id, &layers, ARRAY_SIZE(layers));
}
static inline void get_hierarchy(struct landlock_hierarchy *const hierarchy)
@ -258,10 +321,51 @@ static void put_hierarchy(struct landlock_hierarchy *hierarchy)
}
}
static int merge_tree(struct landlock_ruleset *const dst,
struct landlock_ruleset *const src,
const enum landlock_key_type key_type)
{
struct landlock_rule *walker_rule, *next_rule;
struct rb_root *src_root;
int err = 0;
might_sleep();
lockdep_assert_held(&dst->lock);
lockdep_assert_held(&src->lock);
src_root = get_root(src, key_type);
if (IS_ERR(src_root))
return PTR_ERR(src_root);
/* Merges the @src tree. */
rbtree_postorder_for_each_entry_safe(walker_rule, next_rule, src_root,
node) {
struct landlock_layer layers[] = { {
.level = dst->num_layers,
} };
const struct landlock_id id = {
.key = walker_rule->key,
.type = key_type,
};
if (WARN_ON_ONCE(walker_rule->num_layers != 1))
return -EINVAL;
if (WARN_ON_ONCE(walker_rule->layers[0].level != 0))
return -EINVAL;
layers[0].access = walker_rule->layers[0].access;
err = insert_rule(dst, id, &layers, ARRAY_SIZE(layers));
if (err)
return err;
}
return err;
}
static int merge_ruleset(struct landlock_ruleset *const dst,
struct landlock_ruleset *const src)
{
struct landlock_rule *walker_rule, *next_rule;
int err = 0;
might_sleep();
@ -281,29 +385,19 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
err = -EINVAL;
goto out_unlock;
}
dst->fs_access_masks[dst->num_layers - 1] = src->fs_access_masks[0];
dst->access_masks[dst->num_layers - 1] = src->access_masks[0];
/* Merges the @src tree. */
rbtree_postorder_for_each_entry_safe(walker_rule, next_rule, &src->root,
node) {
struct landlock_layer layers[] = { {
.level = dst->num_layers,
} };
/* Merges the @src inode tree. */
err = merge_tree(dst, src, LANDLOCK_KEY_INODE);
if (err)
goto out_unlock;
if (WARN_ON_ONCE(walker_rule->num_layers != 1)) {
err = -EINVAL;
goto out_unlock;
}
if (WARN_ON_ONCE(walker_rule->layers[0].level != 0)) {
err = -EINVAL;
goto out_unlock;
}
layers[0].access = walker_rule->layers[0].access;
err = insert_rule(dst, walker_rule->object, &layers,
ARRAY_SIZE(layers));
if (err)
goto out_unlock;
}
#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);
@ -311,10 +405,41 @@ out_unlock:
return err;
}
static int inherit_tree(struct landlock_ruleset *const parent,
struct landlock_ruleset *const child,
const enum landlock_key_type key_type)
{
struct landlock_rule *walker_rule, *next_rule;
struct rb_root *parent_root;
int err = 0;
might_sleep();
lockdep_assert_held(&parent->lock);
lockdep_assert_held(&child->lock);
parent_root = get_root(parent, key_type);
if (IS_ERR(parent_root))
return PTR_ERR(parent_root);
/* Copies the @parent inode or network tree. */
rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
parent_root, node) {
const struct landlock_id id = {
.key = walker_rule->key,
.type = key_type,
};
err = insert_rule(child, id, &walker_rule->layers,
walker_rule->num_layers);
if (err)
return err;
}
return err;
}
static int inherit_ruleset(struct landlock_ruleset *const parent,
struct landlock_ruleset *const child)
{
struct landlock_rule *walker_rule, *next_rule;
int err = 0;
might_sleep();
@ -325,23 +450,25 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
mutex_lock(&child->lock);
mutex_lock_nested(&parent->lock, SINGLE_DEPTH_NESTING);
/* Copies the @parent tree. */
rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
&parent->root, node) {
err = insert_rule(child, walker_rule->object,
&walker_rule->layers,
walker_rule->num_layers);
if (err)
goto out_unlock;
}
/* Copies the @parent inode tree. */
err = inherit_tree(parent, child, LANDLOCK_KEY_INODE);
if (err)
goto out_unlock;
#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;
}
/* Copies the parent layer stack and leaves a space for the new layer. */
memcpy(child->fs_access_masks, parent->fs_access_masks,
flex_array_size(parent, fs_access_masks, parent->num_layers));
memcpy(child->access_masks, parent->access_masks,
flex_array_size(parent, access_masks, parent->num_layers));
if (WARN_ON_ONCE(!parent->hierarchy)) {
err = -EINVAL;
@ -361,8 +488,16 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
struct landlock_rule *freeme, *next;
might_sleep();
rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root, node)
free_rule(freeme);
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);
}
@ -453,23 +588,151 @@ out_put_dom:
*/
const struct landlock_rule *
landlock_find_rule(const struct landlock_ruleset *const ruleset,
const struct landlock_object *const object)
const struct landlock_id id)
{
const struct rb_root *root;
const struct rb_node *node;
if (!object)
root = get_root((struct landlock_ruleset *)ruleset, id.type);
if (IS_ERR(root))
return NULL;
node = ruleset->root.rb_node;
node = root->rb_node;
while (node) {
struct landlock_rule *this =
rb_entry(node, struct landlock_rule, node);
if (this->object == object)
if (this->key.data == id.key.data)
return this;
if (this->object < object)
if (this->key.data < id.key.data)
node = node->rb_right;
else
node = node->rb_left;
}
return NULL;
}
/*
* @layer_masks is read and may be updated according to the access request and
* the matching rule.
* @masks_array_size must be equal to ARRAY_SIZE(*layer_masks).
*
* Returns true if the request is allowed (i.e. relevant layer masks for the
* request are empty).
*/
bool landlock_unmask_layers(const struct landlock_rule *const rule,
const access_mask_t access_request,
layer_mask_t (*const layer_masks)[],
const size_t masks_array_size)
{
size_t layer_level;
if (!access_request || !layer_masks)
return true;
if (!rule)
return false;
/*
* An access is granted if, for each policy layer, at least one rule
* encountered on the pathwalk grants the requested access,
* regardless of its position in the layer stack. We must then check
* the remaining layers for each inode, from the first added layer to
* the last one. When there is multiple requested accesses, for each
* policy layer, the full set of requested accesses may not be granted
* by only one rule, but by the union (binary OR) of multiple rules.
* E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
*/
for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
const struct landlock_layer *const layer =
&rule->layers[layer_level];
const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
const unsigned long access_req = access_request;
unsigned long access_bit;
bool is_empty;
/*
* Records in @layer_masks which layer grants access to each
* requested access.
*/
is_empty = true;
for_each_set_bit(access_bit, &access_req, masks_array_size) {
if (layer->access & BIT_ULL(access_bit))
(*layer_masks)[access_bit] &= ~layer_bit;
is_empty = is_empty && !(*layer_masks)[access_bit];
}
if (is_empty)
return true;
}
return false;
}
typedef access_mask_t
get_access_mask_t(const struct landlock_ruleset *const ruleset,
const u16 layer_level);
/**
* landlock_init_layer_masks - Initialize layer masks from an access request
*
* 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.
*
* @domain: The domain that defines the current restrictions.
* @access_request: The requested access rights to check.
* @layer_masks: It must contain %LANDLOCK_NUM_ACCESS_FS or
* %LANDLOCK_NUM_ACCESS_NET elements according to @key_type.
* @key_type: The key type to switch between access masks of different types.
*
* Returns: An access mask where each access right bit is set which is handled
* in any of the active layers in @domain.
*/
access_mask_t
landlock_init_layer_masks(const struct landlock_ruleset *const domain,
const access_mask_t access_request,
layer_mask_t (*const layer_masks)[],
const enum landlock_key_type key_type)
{
access_mask_t handled_accesses = 0;
size_t layer_level, num_access;
get_access_mask_t *get_access_mask;
switch (key_type) {
case LANDLOCK_KEY_INODE:
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;
}
memset(layer_masks, 0,
array_size(sizeof((*layer_masks)[0]), num_access));
/* An empty access request can happen because of O_WRONLY | O_RDWR. */
if (!access_request)
return 0;
/* Saves all handled accesses per layer. */
for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
const unsigned long access_req = access_request;
unsigned long access_bit;
for_each_set_bit(access_bit, &access_req, num_access) {
if (BIT_ULL(access_bit) &
get_access_mask(domain, layer_level)) {
(*layer_masks)[access_bit] |=
BIT_ULL(layer_level);
handled_accesses |= BIT_ULL(access_bit);
}
}
}
return handled_accesses;
}

185
security/landlock/ruleset.h
View File

@ -15,16 +15,35 @@
#include <linux/rbtree.h>
#include <linux/refcount.h>
#include <linux/workqueue.h>
#include <uapi/linux/landlock.h>
#include "limits.h"
#include "object.h"
/*
* All access rights that are denied by default whether they are handled or not
* by a ruleset/layer. This must be ORed with all ruleset->access_masks[]
* entries when we need to get the absolute handled access masks.
*/
/* clang-format off */
#define LANDLOCK_ACCESS_FS_INITIALLY_DENIED ( \
LANDLOCK_ACCESS_FS_REFER)
/* clang-format on */
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 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 + LANDLOCK_NUM_ACCESS_NET);
typedef u16 layer_mask_t;
/* Makes sure all layers can be checked. */
static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS);
@ -44,6 +63,52 @@ struct landlock_layer {
access_mask_t access;
};
/**
* union landlock_key - Key of a ruleset's red-black tree
*/
union landlock_key {
/**
* @object: Pointer to identify a kernel object (e.g. an inode).
*/
struct landlock_object *object;
/**
* @data: Raw data to identify an arbitrary 32-bit value
* (e.g. a TCP port).
*/
uintptr_t data;
};
/**
* enum landlock_key_type - Type of &union landlock_key
*/
enum landlock_key_type {
/**
* @LANDLOCK_KEY_INODE: Type of &landlock_ruleset.root_inode's node
* keys.
*/
LANDLOCK_KEY_INODE = 1,
/**
* @LANDLOCK_KEY_NET_PORT: Type of &landlock_ruleset.root_net_port's
* node keys.
*/
LANDLOCK_KEY_NET_PORT,
};
/**
* struct landlock_id - Unique rule identifier for a ruleset
*/
struct landlock_id {
/**
* @key: Identifies either a kernel object (e.g. an inode) or
* a raw value (e.g. a TCP port).
*/
union landlock_key key;
/**
* @type: Type of a landlock_ruleset's root tree.
*/
const enum landlock_key_type type;
};
/**
* struct landlock_rule - Access rights tied to an object
*/
@ -53,12 +118,13 @@ struct landlock_rule {
*/
struct rb_node node;
/**
* @object: Pointer to identify a kernel object (e.g. an inode). This
* is used as a key for this ruleset element. This pointer is set once
* and never modified. It always points to an allocated object because
* each rule increments the refcount of its object.
* @key: A union to identify either a kernel object (e.g. an inode) or
* a raw data value (e.g. a network socket port). This is used as a key
* for this ruleset element. The pointer is set once and never
* modified. It always points to an allocated object because each rule
* increments the refcount of its object.
*/
struct landlock_object *object;
union landlock_key key;
/**
* @num_layers: Number of entries in @layers.
*/
@ -94,11 +160,23 @@ struct landlock_hierarchy {
*/
struct landlock_ruleset {
/**
* @root: Root of a red-black tree containing &struct landlock_rule
* nodes. Once a ruleset is tied to a process (i.e. as a domain), this
* tree is immutable until @usage reaches zero.
* @root_inode: Root of a red-black tree containing &struct
* landlock_rule nodes with inode object. 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;
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.
@ -110,7 +188,7 @@ struct landlock_ruleset {
* section. This is only used by
* landlock_put_ruleset_deferred() when @usage reaches zero.
* The fields @lock, @usage, @num_rules, @num_layers and
* @fs_access_masks are then unused.
* @access_masks are then unused.
*/
struct work_struct work_free;
struct {
@ -137,30 +215,31 @@ struct landlock_ruleset {
*/
u32 num_layers;
/**
* @fs_access_masks: Contains the subset of filesystem
* actions that are restricted by a ruleset. A domain
* saves all layers of merged rulesets in a stack
* (FAM), starting from the first layer to the last
* one. These layers are used when merging rulesets,
* for user space backward compatibility (i.e.
* future-proof), and to properly handle merged
* @access_masks: Contains the subset of filesystem and
* network actions that are restricted by a ruleset.
* A domain saves all layers of merged rulesets in a
* stack (FAM), starting from the first layer to the
* last one. These layers are used when merging
* rulesets, for user space backward compatibility
* (i.e. future-proof), and to properly handle merged
* rulesets without overlapping access rights. These
* layers are set once and never changed for the
* lifetime of the ruleset.
*/
access_mask_t fs_access_masks[];
access_masks_t access_masks[];
};
};
};
struct landlock_ruleset *
landlock_create_ruleset(const access_mask_t fs_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);
int landlock_insert_rule(struct landlock_ruleset *const ruleset,
struct landlock_object *const object,
const struct landlock_id id,
const access_mask_t access);
struct landlock_ruleset *
@ -169,7 +248,7 @@ landlock_merge_ruleset(struct landlock_ruleset *const parent,
const struct landlock_rule *
landlock_find_rule(const struct landlock_ruleset *const ruleset,
const struct landlock_object *const object);
const struct landlock_id id);
static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
{
@ -177,4 +256,68 @@ static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
refcount_inc(&ruleset->usage);
}
static inline void
landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
const access_mask_t fs_access_mask,
const u16 layer_level)
{
access_mask_t fs_mask = fs_access_mask & LANDLOCK_MASK_ACCESS_FS;
/* Should already be checked in sys_landlock_create_ruleset(). */
WARN_ON_ONCE(fs_access_mask != fs_mask);
ruleset->access_masks[layer_level] |=
(fs_mask << LANDLOCK_SHIFT_ACCESS_FS);
}
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);
ruleset->access_masks[layer_level] |=
(net_mask << LANDLOCK_SHIFT_ACCESS_NET);
}
static inline access_mask_t
landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset,
const u16 layer_level)
{
return (ruleset->access_masks[layer_level] >>
LANDLOCK_SHIFT_ACCESS_FS) &
LANDLOCK_MASK_ACCESS_FS;
}
static inline access_mask_t
landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
const u16 layer_level)
{
/* Handles all initially denied by default access rights. */
return landlock_get_raw_fs_access_mask(ruleset, layer_level) |
LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
}
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;
}
bool landlock_unmask_layers(const struct landlock_rule *const rule,
const access_mask_t access_request,
layer_mask_t (*const layer_masks)[],
const size_t masks_array_size);
access_mask_t
landlock_init_layer_masks(const struct landlock_ruleset *const domain,
const access_mask_t access_request,
layer_mask_t (*const layer_masks)[],
const enum landlock_key_type key_type);
#endif /* _SECURITY_LANDLOCK_RULESET_H */

2
security/landlock/setup.c
View File

@ -12,6 +12,7 @@
#include "common.h"
#include "cred.h"
#include "fs.h"
#include "net.h"
#include "ptrace.h"
#include "setup.h"
@ -29,6 +30,7 @@ static int __init landlock_init(void)
landlock_add_cred_hooks();
landlock_add_ptrace_hooks();
landlock_add_fs_hooks();
landlock_add_net_hooks();
landlock_initialized = true;
pr_info("Up and running.\n");
return 0;

158
security/landlock/syscalls.c
View File

@ -29,6 +29,7 @@
#include "cred.h"
#include "fs.h"
#include "limits.h"
#include "net.h"
#include "ruleset.h"
#include "setup.h"
@ -74,7 +75,8 @@ static void build_check_abi(void)
{
struct landlock_ruleset_attr ruleset_attr;
struct landlock_path_beneath_attr path_beneath_attr;
size_t ruleset_size, path_beneath_size;
struct landlock_net_port_attr net_port_attr;
size_t ruleset_size, path_beneath_size, net_port_size;
/*
* For each user space ABI structures, first checks that there is no
@ -82,13 +84,19 @@ 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);
BUILD_BUG_ON(sizeof(path_beneath_attr) != path_beneath_size);
BUILD_BUG_ON(sizeof(path_beneath_attr) != 12);
net_port_size = sizeof(net_port_attr.allowed_access);
net_port_size += sizeof(net_port_attr.port);
BUILD_BUG_ON(sizeof(net_port_attr) != net_port_size);
BUILD_BUG_ON(sizeof(net_port_attr) != 16);
}
/* Ruleset handling */
@ -129,7 +137,7 @@ static const struct file_operations ruleset_fops = {
.write = fop_dummy_write,
};
#define LANDLOCK_ABI_VERSION 3
#define LANDLOCK_ABI_VERSION 4
/**
* sys_landlock_create_ruleset - Create a new ruleset
@ -188,8 +196,14 @@ 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);
@ -274,13 +288,84 @@ out_fdput:
return err;
}
static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
const void __user *const rule_attr)
{
struct landlock_path_beneath_attr path_beneath_attr;
struct path path;
int res, err;
access_mask_t mask;
/* Copies raw user space buffer. */
res = copy_from_user(&path_beneath_attr, rule_attr,
sizeof(path_beneath_attr));
if (res)
return -EFAULT;
/*
* Informs about useless rule: empty allowed_access (i.e. deny rules)
* are ignored in path walks.
*/
if (!path_beneath_attr.allowed_access)
return -ENOMSG;
/* Checks that allowed_access matches the @ruleset constraints. */
mask = landlock_get_raw_fs_access_mask(ruleset, 0);
if ((path_beneath_attr.allowed_access | mask) != mask)
return -EINVAL;
/* Gets and checks the new rule. */
err = get_path_from_fd(path_beneath_attr.parent_fd, &path);
if (err)
return err;
/* Imports the new rule. */
err = landlock_append_fs_rule(ruleset, &path,
path_beneath_attr.allowed_access);
path_put(&path);
return err;
}
static int add_rule_net_port(struct landlock_ruleset *ruleset,
const void __user *const rule_attr)
{
struct landlock_net_port_attr net_port_attr;
int res;
access_mask_t mask;
/* Copies raw user space buffer. */
res = copy_from_user(&net_port_attr, rule_attr, sizeof(net_port_attr));
if (res)
return -EFAULT;
/*
* Informs about useless rule: empty allowed_access (i.e. deny rules)
* are ignored by network actions.
*/
if (!net_port_attr.allowed_access)
return -ENOMSG;
/* Checks that allowed_access matches the @ruleset constraints. */
mask = landlock_get_net_access_mask(ruleset, 0);
if ((net_port_attr.allowed_access | mask) != mask)
return -EINVAL;
/* Denies inserting a rule with port greater than 65535. */
if (net_port_attr.port > U16_MAX)
return -EINVAL;
/* Imports the new rule. */
return landlock_append_net_rule(ruleset, net_port_attr.port,
net_port_attr.allowed_access);
}
/**
* sys_landlock_add_rule - Add a new rule to a ruleset
*
* @ruleset_fd: File descriptor tied to the ruleset that should be extended
* with the new rule.
* @rule_type: Identify the structure type pointed to by @rule_attr (only
* %LANDLOCK_RULE_PATH_BENEATH for now).
* @rule_type: Identify the structure type pointed to by @rule_attr:
* %LANDLOCK_RULE_PATH_BENEATH or %LANDLOCK_RULE_NET_PORT.
* @rule_attr: Pointer to a rule (only of type &struct
* landlock_path_beneath_attr for now).
* @flags: Must be 0.
@ -291,9 +376,13 @@ out_fdput:
* Possible returned errors are:
*
* - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
* - %EAFNOSUPPORT: @rule_type is %LANDLOCK_RULE_NET_PORT but TCP/IP is not
* supported by the running kernel;
* - %EINVAL: @flags is not 0, or inconsistent access in the rule (i.e.
* &landlock_path_beneath_attr.allowed_access is not a subset of the
* ruleset handled accesses);
* &landlock_path_beneath_attr.allowed_access or
* &landlock_net_port_attr.allowed_access is not a subset of the
* ruleset handled accesses), or &landlock_net_port_attr.port is
* greater than 65535;
* - %ENOMSG: Empty accesses (e.g. &landlock_path_beneath_attr.allowed_access);
* - %EBADF: @ruleset_fd is not a file descriptor for the current thread, or a
* member of @rule_attr is not a file descriptor as expected;
@ -306,10 +395,8 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
const enum landlock_rule_type, rule_type,
const void __user *const, rule_attr, const __u32, flags)
{
struct landlock_path_beneath_attr path_beneath_attr;
struct path path;
struct landlock_ruleset *ruleset;
int res, err;
int err;
if (!landlock_initialized)
return -EOPNOTSUPP;
@ -323,48 +410,17 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
if (IS_ERR(ruleset))
return PTR_ERR(ruleset);
if (rule_type != LANDLOCK_RULE_PATH_BENEATH) {
switch (rule_type) {
case LANDLOCK_RULE_PATH_BENEATH:
err = add_rule_path_beneath(ruleset, rule_attr);
break;
case LANDLOCK_RULE_NET_PORT:
err = add_rule_net_port(ruleset, rule_attr);
break;
default:
err = -EINVAL;
goto out_put_ruleset;
break;
}
/* Copies raw user space buffer, only one type for now. */
res = copy_from_user(&path_beneath_attr, rule_attr,
sizeof(path_beneath_attr));
if (res) {
err = -EFAULT;
goto out_put_ruleset;
}
/*
* Informs about useless rule: empty allowed_access (i.e. deny rules)
* are ignored in path walks.
*/
if (!path_beneath_attr.allowed_access) {
err = -ENOMSG;
goto out_put_ruleset;
}
/*
* Checks that allowed_access matches the @ruleset constraints
* (ruleset->fs_access_masks[0] is automatically upgraded to 64-bits).
*/
if ((path_beneath_attr.allowed_access | ruleset->fs_access_masks[0]) !=
ruleset->fs_access_masks[0]) {
err = -EINVAL;
goto out_put_ruleset;
}
/* Gets and checks the new rule. */
err = get_path_from_fd(path_beneath_attr.parent_fd, &path);
if (err)
goto out_put_ruleset;
/* Imports the new rule. */
err = landlock_append_fs_rule(ruleset, &path,
path_beneath_attr.allowed_access);
path_put(&path);
out_put_ruleset:
landlock_put_ruleset(ruleset);
return err;
}

2
tools/testing/selftests/landlock/base_test.c
View File

@ -75,7 +75,7 @@ TEST(abi_version)
const struct landlock_ruleset_attr ruleset_attr = {
.handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
};
ASSERT_EQ(3, landlock_create_ruleset(NULL, 0,
ASSERT_EQ(4, landlock_create_ruleset(NULL, 0,
LANDLOCK_CREATE_RULESET_VERSION));
ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,

13
tools/testing/selftests/landlock/common.h
View File

@ -112,10 +112,13 @@ static void _init_caps(struct __test_metadata *const _metadata, bool drop_all)
cap_t cap_p;
/* Only these three capabilities are useful for the tests. */
const cap_value_t caps[] = {
/* clang-format off */
CAP_DAC_OVERRIDE,
CAP_MKNOD,
CAP_SYS_ADMIN,
CAP_SYS_CHROOT,
CAP_NET_BIND_SERVICE,
/* clang-format on */
};
cap_p = cap_get_proc();
@ -256,3 +259,13 @@ static int __maybe_unused send_fd(int usock, int fd_tx)
return -errno;
return 0;
}
static void __maybe_unused
enforce_ruleset(struct __test_metadata *const _metadata, const int ruleset_fd)
{
ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0))
{
TH_LOG("Failed to enforce ruleset: %s", strerror(errno));
}
}

4
tools/testing/selftests/landlock/config
View File

@ -1,5 +1,9 @@
CONFIG_CGROUPS=y
CONFIG_CGROUP_SCHED=y
CONFIG_INET=y
CONFIG_IPV6=y
CONFIG_NET=y
CONFIG_NET_NS=y
CONFIG_OVERLAY_FS=y
CONFIG_PROC_FS=y
CONFIG_SECURITY=y

69
tools/testing/selftests/landlock/fs_test.c
View File

@ -677,16 +677,6 @@ static int create_ruleset(struct __test_metadata *const _metadata,
return ruleset_fd;
}
static void enforce_ruleset(struct __test_metadata *const _metadata,
const int ruleset_fd)
{
ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0))
{
TH_LOG("Failed to enforce ruleset: %s", strerror(errno));
}
}
TEST_F_FORK(layout0, proc_nsfs)
{
const struct rule rules[] = {
@ -1635,6 +1625,65 @@ TEST_F_FORK(layout1, move_mount)
clear_cap(_metadata, CAP_SYS_ADMIN);
}
TEST_F_FORK(layout1, topology_changes_with_net_only)
{
const struct landlock_ruleset_attr ruleset_net = {
.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
LANDLOCK_ACCESS_NET_CONNECT_TCP,
};
int ruleset_fd;
/* Add network restrictions. */
ruleset_fd =
landlock_create_ruleset(&ruleset_net, sizeof(ruleset_net), 0);
ASSERT_LE(0, ruleset_fd);
enforce_ruleset(_metadata, ruleset_fd);
ASSERT_EQ(0, close(ruleset_fd));
/* Mount, remount, move_mount, umount, and pivot_root checks. */
set_cap(_metadata, CAP_SYS_ADMIN);
ASSERT_EQ(0, mount_opt(&mnt_tmp, dir_s1d2));
ASSERT_EQ(0, mount(NULL, dir_s1d2, NULL, MS_PRIVATE | MS_REC, NULL));
ASSERT_EQ(0, syscall(__NR_move_mount, AT_FDCWD, dir_s1d2, AT_FDCWD,
dir_s2d2, 0));
ASSERT_EQ(0, umount(dir_s2d2));
ASSERT_EQ(0, syscall(__NR_pivot_root, dir_s3d2, dir_s3d3));
ASSERT_EQ(0, chdir("/"));
clear_cap(_metadata, CAP_SYS_ADMIN);
}
TEST_F_FORK(layout1, topology_changes_with_net_and_fs)
{
const struct landlock_ruleset_attr ruleset_net_fs = {
.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
LANDLOCK_ACCESS_NET_CONNECT_TCP,
.handled_access_fs = LANDLOCK_ACCESS_FS_EXECUTE,
};
int ruleset_fd;
/* Add network and filesystem restrictions. */
ruleset_fd = landlock_create_ruleset(&ruleset_net_fs,
sizeof(ruleset_net_fs), 0);
ASSERT_LE(0, ruleset_fd);
enforce_ruleset(_metadata, ruleset_fd);
ASSERT_EQ(0, close(ruleset_fd));
/* Mount, remount, move_mount, umount, and pivot_root checks. */
set_cap(_metadata, CAP_SYS_ADMIN);
ASSERT_EQ(-1, mount_opt(&mnt_tmp, dir_s1d2));
ASSERT_EQ(EPERM, errno);
ASSERT_EQ(-1, mount(NULL, dir_s3d2, NULL, MS_PRIVATE | MS_REC, NULL));
ASSERT_EQ(EPERM, errno);
ASSERT_EQ(-1, syscall(__NR_move_mount, AT_FDCWD, dir_s3d2, AT_FDCWD,
dir_s2d2, 0));
ASSERT_EQ(EPERM, errno);
ASSERT_EQ(-1, umount(dir_s3d2));
ASSERT_EQ(EPERM, errno);
ASSERT_EQ(-1, syscall(__NR_pivot_root, dir_s3d2, dir_s3d3));
ASSERT_EQ(EPERM, errno);
clear_cap(_metadata, CAP_SYS_ADMIN);
}
TEST_F_FORK(layout1, release_inodes)
{
const struct rule rules[] = {

1738
tools/testing/selftests/landlock/net_test.c Normal file
View File

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