diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h index f2927681e92d..811ec77f9105 100644 --- a/include/uapi/linux/landlock.h +++ b/include/uapi/linux/landlock.h @@ -378,11 +378,34 @@ struct landlock_net_port_attr { * * - %LANDLOCK_ACCESS_NET_BIND_UDP: Bind UDP sockets to the given local * port. Support added in Landlock ABI version 10. + * - %LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP: Set the remote port of UDP + * sockets to the given port, or send datagrams to the given remote port + * ignoring any destination pre-set on a socket. Support added in + * Landlock ABI version 10. + * + * .. note:: Setting a remote address or sending a first datagram + * auto-binds UDP sockets to an ephemeral local source port if not + * already bound. To allow this if both %LANDLOCK_ACCESS_NET_BIND_UDP + * and %LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP are handled, you need to + * either: + * + * - use a socket already bound to a port before the ruleset started + * being enforced; + * - or grant %LANDLOCK_ACCESS_NET_BIND_UDP on port 0, meaning "any + * port in the ephemeral port range"; + * - or grant %LANDLOCK_ACCESS_NET_BIND_UDP on a specific port, and + * call :manpage:`bind(2)` on that port before trying to + * :manpage:`connect(2)` or send datagrams. + * + * .. note:: Sending datagrams to an ``AF_UNSPEC`` destination address + * family is not supported for IPv6 UDP sockets: you will need to use a + * ``NULL`` address instead. */ /* clang-format off */ #define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0) #define LANDLOCK_ACCESS_NET_CONNECT_TCP (1ULL << 1) #define LANDLOCK_ACCESS_NET_BIND_UDP (1ULL << 2) +#define LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP (1ULL << 3) /* clang-format on */ /** diff --git a/security/landlock/audit.c b/security/landlock/audit.c index e676ebffeebe..851647197a01 100644 --- a/security/landlock/audit.c +++ b/security/landlock/audit.c @@ -46,6 +46,8 @@ static const char *const net_access_strings[] = { [BIT_INDEX(LANDLOCK_ACCESS_NET_BIND_TCP)] = "net.bind_tcp", [BIT_INDEX(LANDLOCK_ACCESS_NET_CONNECT_TCP)] = "net.connect_tcp", [BIT_INDEX(LANDLOCK_ACCESS_NET_BIND_UDP)] = "net.bind_udp", + [BIT_INDEX(LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP)] = + "net.connect_send_udp", }; static_assert(ARRAY_SIZE(net_access_strings) == LANDLOCK_NUM_ACCESS_NET); diff --git a/security/landlock/limits.h b/security/landlock/limits.h index c0f30a4591b8..a4d908b240a2 100644 --- a/security/landlock/limits.h +++ b/security/landlock/limits.h @@ -23,7 +23,7 @@ #define LANDLOCK_MASK_ACCESS_FS ((LANDLOCK_LAST_ACCESS_FS << 1) - 1) #define LANDLOCK_NUM_ACCESS_FS __const_hweight64(LANDLOCK_MASK_ACCESS_FS) -#define LANDLOCK_LAST_ACCESS_NET LANDLOCK_ACCESS_NET_BIND_UDP +#define LANDLOCK_LAST_ACCESS_NET LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP #define LANDLOCK_MASK_ACCESS_NET ((LANDLOCK_LAST_ACCESS_NET << 1) - 1) #define LANDLOCK_NUM_ACCESS_NET __const_hweight64(LANDLOCK_MASK_ACCESS_NET) diff --git a/security/landlock/net.c b/security/landlock/net.c index f57fe2a44f0d..942f856433c9 100644 --- a/security/landlock/net.c +++ b/security/landlock/net.c @@ -44,7 +44,8 @@ int landlock_append_net_rule(struct landlock_ruleset *const ruleset, static int current_check_access_socket(struct socket *const sock, struct sockaddr *const address, const int addrlen, - access_mask_t access_request) + access_mask_t access_request, + bool connecting) { unsigned short sock_family; __be16 port; @@ -75,19 +76,50 @@ static int current_check_access_socket(struct socket *const sock, switch (address->sa_family) { case AF_UNSPEC: - if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) { + if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP || + (access_request == LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP && + connecting)) { /* - * 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. + * Connecting to an address with AF_UNSPEC dissolves the + * remote association while retaining the socket object + * (i.e., the file descriptor). For TCP, it has the same + * effect as closing the connection. For UDP, it removes + * any preset remote address. As for dropping + * privileges, these actions are always allowed. Let + * the network stack handle potential inconsistencies + * and return -EINVAL if needed. */ return 0; + } else if (access_request == + LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) { + if (sock_family == AF_INET6) { + /* + * We cannot allow sending UDP datagrams to an + * explicit AF_UNSPEC address on IPv6 sockets, + * even if AF_UNSPEC is treated as "no address" + * on such sockets (so it should always be + * allowed). That's because the socket's family + * can change under our feet (if another thread + * calls setsockopt(IPV6_ADDRFORM)) to IPv4, + * which would then treat AF_UNSPEC as AF_INET. + */ + audit_net.family = AF_UNSPEC; + audit_net.sk = sock->sk; + landlock_init_layer_masks( + subject->domain, access_request, + &layer_masks, LANDLOCK_KEY_NET_PORT); + 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; + } } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP || access_request == LANDLOCK_ACCESS_NET_BIND_UDP) { /* @@ -130,7 +162,11 @@ static int current_check_access_socket(struct socket *const sock, } else { WARN_ON_ONCE(1); } - /* Only for bind(AF_UNSPEC+INADDR_ANY) on IPv4 socket. */ + /* + * AF_UNSPEC is treated as AF_INET only in + * bind(AF_UNSPEC+INADDR_ANY) on IPv4 sockets and when sending + * to AF_UNSPEC addresses on IPv4 sockets. + */ fallthrough; case AF_INET: { const struct sockaddr_in *addr4; @@ -141,7 +177,8 @@ static int current_check_access_socket(struct socket *const sock, addr4 = (struct sockaddr_in *)address; port = addr4->sin_port; - if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) { + if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP || + access_request == LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) { audit_net.dport = port; audit_net.v4info.daddr = addr4->sin_addr.s_addr; } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP || @@ -164,7 +201,8 @@ static int current_check_access_socket(struct socket *const sock, addr6 = (struct sockaddr_in6 *)address; port = addr6->sin6_port; - if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP) { + if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP || + access_request == LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) { audit_net.dport = port; audit_net.v6info.daddr = addr6->sin6_addr; } else if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP || @@ -221,6 +259,44 @@ static int current_check_access_socket(struct socket *const sock, return -EACCES; } +static int current_check_autobind_udp_socket(struct socket *const sock) +{ + const struct access_masks bind_udp = { + .net = LANDLOCK_ACCESS_NET_BIND_UDP, + }; + struct sockaddr_storage port0 = {}; + unsigned short num; + bool slow; + + /* Quick return for non-Landlocked tasks. */ + if (!landlock_get_applicable_subject(current_cred(), bind_udp, NULL)) + return 0; + + /* + * On UDP sockets, if a local port has not already been bound, calling + * connect() or sending a first datagram has the side effect of + * autobinding an ephemeral port: we also have to check that the process + * would have had the right to bind(0) explicitly. Hold the socket lock + * around the inet_num read to exclude udp_lib_get_port()'s transient + * inet_num = snum write that is reverted to 0 on a failing reuseport + * bind. + */ + slow = lock_sock_fast(sock->sk); + num = inet_sk(sock->sk)->inet_num; + unlock_sock_fast(sock->sk, slow); + if (num != 0) + return 0; + + /* + * Construct a struct sockaddr* with port 0 to pretend the process tried + * to bind() on that address. + */ + port0.ss_family = READ_ONCE(sock->sk->sk_family); + + return current_check_access_socket(sock, (struct sockaddr *)&port0, + sizeof(port0), bind_udp.net, false); +} + static int hook_socket_bind(struct socket *const sock, struct sockaddr *const address, const int addrlen) { @@ -234,7 +310,7 @@ static int hook_socket_bind(struct socket *const sock, return 0; return current_check_access_socket(sock, address, addrlen, - access_request); + access_request, false); } static int hook_socket_connect(struct socket *const sock, @@ -242,19 +318,57 @@ static int hook_socket_connect(struct socket *const sock, const int addrlen) { access_mask_t access_request; + int ret = 0; if (sk_is_tcp(sock->sk)) access_request = LANDLOCK_ACCESS_NET_CONNECT_TCP; + else if (sk_is_udp(sock->sk)) + access_request = LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP; else return 0; - return current_check_access_socket(sock, address, addrlen, - access_request); + ret = current_check_access_socket(sock, address, addrlen, + access_request, true); + + /* + * connect()ing to an AF_UNSPEC address does not trigger an autobind and + * should never be restricted. + */ + if (ret == 0 && sk_is_udp(sock->sk) && + addrlen >= offsetofend(typeof(*address), sa_family) && + address->sa_family != AF_UNSPEC) + ret = current_check_autobind_udp_socket(sock); + + return ret; +} + +static int hook_socket_sendmsg(struct socket *const sock, + struct msghdr *const msg, const int size) +{ + struct sockaddr *const address = msg->msg_name; + const int addrlen = msg->msg_namelen; + access_mask_t access_request; + int ret = 0; + + if (sk_is_udp(sock->sk)) + access_request = LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP; + else + return 0; + + if (address != NULL) + ret = current_check_access_socket(sock, address, addrlen, + access_request, false); + + if (ret == 0) + ret = current_check_autobind_udp_socket(sock); + + return ret; } 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), + LSM_HOOK_INIT(socket_sendmsg, hook_socket_sendmsg), }; __init void landlock_add_net_hooks(void) diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c index 135b09fd1880..23d860e76372 100644 --- a/tools/testing/selftests/landlock/net_test.c +++ b/tools/testing/selftests/landlock/net_test.c @@ -1326,12 +1326,13 @@ FIXTURE_TEARDOWN(mini) /* clang-format off */ -#define ACCESS_LAST LANDLOCK_ACCESS_NET_BIND_UDP +#define ACCESS_LAST LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP #define ACCESS_ALL ( \ LANDLOCK_ACCESS_NET_BIND_TCP | \ LANDLOCK_ACCESS_NET_CONNECT_TCP | \ - LANDLOCK_ACCESS_NET_BIND_UDP) + LANDLOCK_ACCESS_NET_BIND_UDP | \ + LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP) /* clang-format on */