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 const struct access_masks any_net = { 43 .net = ~0, 44 }; 45 46 static int current_check_access_socket(struct socket *const sock, 47 struct sockaddr *const address, 48 const int addrlen, 49 access_mask_t access_request) 50 { 51 __be16 port; 52 layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {}; 53 const struct landlock_rule *rule; 54 struct landlock_id id = { 55 .type = LANDLOCK_KEY_NET_PORT, 56 }; 57 const struct landlock_ruleset *const dom = 58 landlock_get_applicable_domain(landlock_get_current_domain(), 59 any_net); 60 61 if (!dom) 62 return 0; 63 if (WARN_ON_ONCE(dom->num_layers < 1)) 64 return -EACCES; 65 66 if (!sk_is_tcp(sock->sk)) 67 return 0; 68 69 /* Checks for minimal header length to safely read sa_family. */ 70 if (addrlen < offsetofend(typeof(*address), sa_family)) 71 return -EINVAL; 72 73 switch (address->sa_family) { 74 case AF_UNSPEC: 75 case AF_INET: 76 if (addrlen < sizeof(struct sockaddr_in)) 77 return -EINVAL; 78 port = ((struct sockaddr_in *)address)->sin_port; 79 break; 80 81 #if IS_ENABLED(CONFIG_IPV6) 82 case AF_INET6: 83 if (addrlen < SIN6_LEN_RFC2133) 84 return -EINVAL; 85 port = ((struct sockaddr_in6 *)address)->sin6_port; 86 break; 87 #endif /* IS_ENABLED(CONFIG_IPV6) */ 88 89 default: 90 return 0; 91 } 92 93 /* Specific AF_UNSPEC handling. */ 94 if (address->sa_family == AF_UNSPEC) { 95 /* 96 * Connecting to an address with AF_UNSPEC dissolves the TCP 97 * association, which have the same effect as closing the 98 * connection while retaining the socket object (i.e., the file 99 * descriptor). As for dropping privileges, closing 100 * connections is always allowed. 101 * 102 * For a TCP access control system, this request is legitimate. 103 * Let the network stack handle potential inconsistencies and 104 * return -EINVAL if needed. 105 */ 106 if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) 107 return 0; 108 109 /* 110 * For compatibility reason, accept AF_UNSPEC for bind 111 * accesses (mapped to AF_INET) only if the address is 112 * INADDR_ANY (cf. __inet_bind). Checking the address is 113 * required to not wrongfully return -EACCES instead of 114 * -EAFNOSUPPORT. 115 * 116 * We could return 0 and let the network stack handle these 117 * checks, but it is safer to return a proper error and test 118 * consistency thanks to kselftest. 119 */ 120 if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) { 121 /* addrlen has already been checked for AF_UNSPEC. */ 122 const struct sockaddr_in *const sockaddr = 123 (struct sockaddr_in *)address; 124 125 if (sock->sk->__sk_common.skc_family != AF_INET) 126 return -EINVAL; 127 128 if (sockaddr->sin_addr.s_addr != htonl(INADDR_ANY)) 129 return -EAFNOSUPPORT; 130 } 131 } else { 132 /* 133 * Checks sa_family consistency to not wrongfully return 134 * -EACCES instead of -EINVAL. Valid sa_family changes are 135 * only (from AF_INET or AF_INET6) to AF_UNSPEC. 136 * 137 * We could return 0 and let the network stack handle this 138 * check, but it is safer to return a proper error and test 139 * consistency thanks to kselftest. 140 */ 141 if (address->sa_family != sock->sk->__sk_common.skc_family) 142 return -EINVAL; 143 } 144 145 id.key.data = (__force uintptr_t)port; 146 BUILD_BUG_ON(sizeof(port) > sizeof(id.key.data)); 147 148 rule = landlock_find_rule(dom, id); 149 access_request = landlock_init_layer_masks( 150 dom, access_request, &layer_masks, LANDLOCK_KEY_NET_PORT); 151 if (landlock_unmask_layers(rule, access_request, &layer_masks, 152 ARRAY_SIZE(layer_masks))) 153 return 0; 154 155 return -EACCES; 156 } 157 158 static int hook_socket_bind(struct socket *const sock, 159 struct sockaddr *const address, const int addrlen) 160 { 161 return current_check_access_socket(sock, address, addrlen, 162 LANDLOCK_ACCESS_NET_BIND_TCP); 163 } 164 165 static int hook_socket_connect(struct socket *const sock, 166 struct sockaddr *const address, 167 const int addrlen) 168 { 169 return current_check_access_socket(sock, address, addrlen, 170 LANDLOCK_ACCESS_NET_CONNECT_TCP); 171 } 172 173 static struct security_hook_list landlock_hooks[] __ro_after_init = { 174 LSM_HOOK_INIT(socket_bind, hook_socket_bind), 175 LSM_HOOK_INIT(socket_connect, hook_socket_connect), 176 }; 177 178 __init void landlock_add_net_hooks(void) 179 { 180 security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks), 181 &landlock_lsmid); 182 } 183