1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Landlock LSM - Network management and hooks
4 *
5 * Copyright © 2022-2023 Huawei Tech. Co., Ltd.
6 * Copyright © 2022-2023 Microsoft Corporation
7 */
8
9 #include <linux/in.h>
10 #include <linux/net.h>
11 #include <linux/socket.h>
12 #include <net/ipv6.h>
13
14 #include "common.h"
15 #include "cred.h"
16 #include "limits.h"
17 #include "net.h"
18 #include "ruleset.h"
19
20 int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
21 const u16 port, access_mask_t access_rights)
22 {
23 int err;
24 const struct landlock_id id = {
25 .key.data = (__force uintptr_t)htons(port),
26 .type = LANDLOCK_KEY_NET_PORT,
27 };
28
29 BUILD_BUG_ON(sizeof(port) > sizeof(id.key.data));
30
31 /* Transforms relative access rights to absolute ones. */
32 access_rights |= LANDLOCK_MASK_ACCESS_NET &
33 ~landlock_get_net_access_mask(ruleset, 0);
34
35 mutex_lock(&ruleset->lock);
36 err = landlock_insert_rule(ruleset, id, access_rights);
37 mutex_unlock(&ruleset->lock);
38
39 return err;
40 }
41
42 static access_mask_t
43 get_raw_handled_net_accesses(const struct landlock_ruleset *const domain)
44 {
45 access_mask_t access_dom = 0;
46 size_t layer_level;
47
48 for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
49 access_dom |= landlock_get_net_access_mask(domain, layer_level);
50 return access_dom;
51 }
52
53 static const struct landlock_ruleset *get_current_net_domain(void)
54 {
55 const struct landlock_ruleset *const dom =
56 landlock_get_current_domain();
57
58 if (!dom || !get_raw_handled_net_accesses(dom))
59 return NULL;
60
61 return dom;
62 }
63
64 static int current_check_access_socket(struct socket *const sock,
65 struct sockaddr *const address,
66 const int addrlen,
67 access_mask_t access_request)
68 {
69 __be16 port;
70 layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {};
71 const struct landlock_rule *rule;
72 struct landlock_id id = {
73 .type = LANDLOCK_KEY_NET_PORT,
74 };
75 const struct landlock_ruleset *const dom = get_current_net_domain();
76
77 if (!dom)
78 return 0;
79 if (WARN_ON_ONCE(dom->num_layers < 1))
80 return -EACCES;
81
82 /* Checks if it's a (potential) TCP socket. */
83 if (sock->type != SOCK_STREAM)
84 return 0;
85
86 /* Checks for minimal header length to safely read sa_family. */
87 if (addrlen < offsetofend(typeof(*address), sa_family))
88 return -EINVAL;
89
90 switch (address->sa_family) {
91 case AF_UNSPEC:
92 case AF_INET:
93 if (addrlen < sizeof(struct sockaddr_in))
94 return -EINVAL;
95 port = ((struct sockaddr_in *)address)->sin_port;
96 break;
97
98 #if IS_ENABLED(CONFIG_IPV6)
99 case AF_INET6:
100 if (addrlen < SIN6_LEN_RFC2133)
101 return -EINVAL;
102 port = ((struct sockaddr_in6 *)address)->sin6_port;
103 break;
104 #endif /* IS_ENABLED(CONFIG_IPV6) */
105
106 default:
107 return 0;
108 }
109
110 /* Specific AF_UNSPEC handling. */
111 if (address->sa_family == AF_UNSPEC) {
112 /*
113 * Connecting to an address with AF_UNSPEC dissolves the TCP
114 * association, which have the same effect as closing the
115 * connection while retaining the socket object (i.e., the file
116 * descriptor). As for dropping privileges, closing
117 * connections is always allowed.
118 *
119 * For a TCP access control system, this request is legitimate.
120 * Let the network stack handle potential inconsistencies and
121 * return -EINVAL if needed.
122 */
123 if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP)
124 return 0;
125
126 /*
127 * For compatibility reason, accept AF_UNSPEC for bind
128 * accesses (mapped to AF_INET) only if the address is
129 * INADDR_ANY (cf. __inet_bind). Checking the address is
130 * required to not wrongfully return -EACCES instead of
131 * -EAFNOSUPPORT.
132 *
133 * We could return 0 and let the network stack handle these
134 * checks, but it is safer to return a proper error and test
135 * consistency thanks to kselftest.
136 */
137 if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
138 /* addrlen has already been checked for AF_UNSPEC. */
139 const struct sockaddr_in *const sockaddr =
140 (struct sockaddr_in *)address;
141
142 if (sock->sk->__sk_common.skc_family != AF_INET)
143 return -EINVAL;
144
145 if (sockaddr->sin_addr.s_addr != htonl(INADDR_ANY))
146 return -EAFNOSUPPORT;
147 }
148 } else {
149 /*
150 * Checks sa_family consistency to not wrongfully return
151 * -EACCES instead of -EINVAL. Valid sa_family changes are
152 * only (from AF_INET or AF_INET6) to AF_UNSPEC.
153 *
154 * We could return 0 and let the network stack handle this
155 * check, but it is safer to return a proper error and test
156 * consistency thanks to kselftest.
157 */
158 if (address->sa_family != sock->sk->__sk_common.skc_family)
159 return -EINVAL;
160 }
161
162 id.key.data = (__force uintptr_t)port;
163 BUILD_BUG_ON(sizeof(port) > sizeof(id.key.data));
164
165 rule = landlock_find_rule(dom, id);
166 access_request = landlock_init_layer_masks(
167 dom, access_request, &layer_masks, LANDLOCK_KEY_NET_PORT);
168 if (landlock_unmask_layers(rule, access_request, &layer_masks,
169 ARRAY_SIZE(layer_masks)))
170 return 0;
171
172 return -EACCES;
173 }
174
175 static int hook_socket_bind(struct socket *const sock,
176 struct sockaddr *const address, const int addrlen)
177 {
178 return current_check_access_socket(sock, address, addrlen,
179 LANDLOCK_ACCESS_NET_BIND_TCP);
180 }
181
182 static int hook_socket_connect(struct socket *const sock,
183 struct sockaddr *const address,
184 const int addrlen)
185 {
186 return current_check_access_socket(sock, address, addrlen,
187 LANDLOCK_ACCESS_NET_CONNECT_TCP);
188 }
189
190 static struct security_hook_list landlock_hooks[] __ro_after_init = {
191 LSM_HOOK_INIT(socket_bind, hook_socket_bind),
192 LSM_HOOK_INIT(socket_connect, hook_socket_connect),
193 };
194
195 __init void landlock_add_net_hooks(void)
196 {
197 security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
198 &landlock_lsmid);
199 }
200
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