// 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);
}