diff options
Diffstat (limited to 'security/landlock/net.c')
| -rw-r--r-- | security/landlock/net.c | 250 |
1 files changed, 250 insertions, 0 deletions
diff --git a/security/landlock/net.c b/security/landlock/net.c new file mode 100644 index 000000000..c36864998 --- /dev/null +++ b/security/landlock/net.c @@ -0,0 +1,250 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Landlock - Network management and hooks + * + * Copyright © 2022-2023 Huawei Tech. Co., Ltd. + * Copyright © 2022-2025 Microsoft Corporation + */ + +#include <linux/in.h> +#include <linux/lsm_audit.h> +#include <linux/net.h> +#include <linux/socket.h> +#include <net/ipv6.h> + +#include "audit.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 int current_check_access_socket(struct socket *const sock, + struct sockaddr *const address, + const int addrlen, + access_mask_t access_request) +{ + __be16 port; + struct layer_access_masks layer_masks = {}; + const struct landlock_rule *rule; + struct landlock_id id = { + .type = LANDLOCK_KEY_NET_PORT, + }; + const struct access_masks masks = { + .net = access_request, + }; + const struct landlock_cred_security *const subject = + landlock_get_applicable_subject(current_cred(), masks, NULL); + struct lsm_network_audit audit_net = {}; + + if (!subject) + 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: + if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) { + /* + * 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. + */ + return 0; + } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) { + /* + * Binding to an AF_UNSPEC address is treated + * differently by IPv4 and IPv6 sockets. The socket's + * family may change under our feet due to + * setsockopt(IPV6_ADDRFORM), but that's ok: we either + * reject entirely or require + * %LANDLOCK_ACCESS_NET_BIND_TCP for the given port, so + * it cannot be used to bypass the policy. + * + * IPv4 sockets map AF_UNSPEC to AF_INET for + * retrocompatibility for bind accesses, only if the + * address is INADDR_ANY (cf. __inet_bind). IPv6 + * sockets always reject it. + * + * Checking the address is required to not wrongfully + * return -EACCES instead of -EAFNOSUPPORT or -EINVAL. + * 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 (sock->sk->__sk_common.skc_family == AF_INET) { + const struct sockaddr_in *const sockaddr = + (struct sockaddr_in *)address; + + if (addrlen < sizeof(struct sockaddr_in)) + return -EINVAL; + + if (sockaddr->sin_addr.s_addr != + htonl(INADDR_ANY)) + return -EAFNOSUPPORT; + } else { + if (addrlen < SIN6_LEN_RFC2133) + return -EINVAL; + else + return -EAFNOSUPPORT; + } + } else { + WARN_ON_ONCE(1); + } + /* Only for bind(AF_UNSPEC+INADDR_ANY) on IPv4 socket. */ + fallthrough; + case AF_INET: { + const struct sockaddr_in *addr4; + + if (addrlen < sizeof(struct sockaddr_in)) + return -EINVAL; + + addr4 = (struct sockaddr_in *)address; + port = addr4->sin_port; + + if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) { + audit_net.dport = port; + audit_net.v4info.daddr = addr4->sin_addr.s_addr; + } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) { + audit_net.sport = port; + audit_net.v4info.saddr = addr4->sin_addr.s_addr; + } else { + WARN_ON_ONCE(1); + } + break; + } + +#if IS_ENABLED(CONFIG_IPV6) + case AF_INET6: { + const struct sockaddr_in6 *addr6; + + if (addrlen < SIN6_LEN_RFC2133) + return -EINVAL; + + addr6 = (struct sockaddr_in6 *)address; + port = addr6->sin6_port; + + if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) { + audit_net.dport = port; + audit_net.v6info.daddr = addr6->sin6_addr; + } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) { + audit_net.sport = port; + audit_net.v6info.saddr = addr6->sin6_addr; + } else { + WARN_ON_ONCE(1); + } + break; + } +#endif /* IS_ENABLED(CONFIG_IPV6) */ + + default: + return 0; + } + + /* + * 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 && + address->sa_family != AF_UNSPEC) + return -EINVAL; + + id.key.data = (__force uintptr_t)port; + BUILD_BUG_ON(sizeof(port) > sizeof(id.key.data)); + + rule = landlock_find_rule(subject->domain, id); + access_request = landlock_init_layer_masks(subject->domain, + access_request, &layer_masks, + LANDLOCK_KEY_NET_PORT); + if (!access_request) + return 0; + + if (landlock_unmask_layers(rule, &layer_masks)) + return 0; + + audit_net.family = address->sa_family; + landlock_log_denial(subject, + &(struct landlock_request){ + .type = LANDLOCK_REQUEST_NET_ACCESS, + .audit.type = LSM_AUDIT_DATA_NET, + .audit.u.net = &audit_net, + .access = access_request, + .layer_masks = &layer_masks, + }); + return -EACCES; +} + +static int hook_socket_bind(struct socket *const sock, + struct sockaddr *const address, const int addrlen) +{ + access_mask_t access_request; + + if (sk_is_tcp(sock->sk)) + access_request = LANDLOCK_ACCESS_NET_BIND_TCP; + else + return 0; + + return current_check_access_socket(sock, address, addrlen, + access_request); +} + +static int hook_socket_connect(struct socket *const sock, + struct sockaddr *const address, + const int addrlen) +{ + access_mask_t access_request; + + if (sk_is_tcp(sock->sk)) + access_request = LANDLOCK_ACCESS_NET_CONNECT_TCP; + else + return 0; + + return current_check_access_socket(sock, address, addrlen, + access_request); +} + +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); +} |