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// 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,
access_mask_t access_request)
{
__be16 port;
layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {};
const struct landlock_rule *rule;
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);
access_request = landlock_init_layer_masks(
dom, access_request, &layer_masks, LANDLOCK_KEY_NET_PORT);
if (landlock_unmask_layers(rule, access_request, &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_lsmid);
}
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