// SPDX-License-Identifier: GPL-2.0-or-later
/* SCTP kernel implementation
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001-2002 International Business Machines, Corp.
 * Copyright (c) 2001 Intel Corp.
 * Copyright (c) 2001 Nokia, Inc.
 * Copyright (c) 2001 La Monte H.P. Yarroll
 *
 * This file is part of the SCTP kernel implementation
 *
 * This abstraction represents an SCTP endpoint.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <linux-sctp@vger.kernel.org>
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Karl Knutson <karl@athena.chicago.il.us>
 *    Jon Grimm <jgrimm@austin.ibm.com>
 *    Daisy Chang <daisyc@us.ibm.com>
 *    Dajiang Zhang <dajiang.zhang@nokia.com>
 */

#include <linux/types.h>
#include <linux/slab.h>
#include <linux/in.h>
#include <linux/random.h>       /* get_random_bytes() */
#include <net/sock.h>
#include <net/ipv6.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

/* Forward declarations for internal helpers. */
static void sctp_endpoint_bh_rcv(struct work_struct *work);

static void gen_cookie_auth_key(struct hmac_sha256_key *key)
{
        u8 raw_key[SCTP_COOKIE_KEY_SIZE];

        get_random_bytes(raw_key, sizeof(raw_key));
        hmac_sha256_preparekey(key, raw_key, sizeof(raw_key));
        memzero_explicit(raw_key, sizeof(raw_key));
}

/*
 * Initialize the base fields of the endpoint structure.
 */
static struct sctp_endpoint *sctp_endpoint_init(struct sctp_endpoint *ep,
                                                struct sock *sk,
                                                gfp_t gfp)
{
        struct net *net = sock_net(sk);
        struct sctp_shared_key *null_key;

        ep->asconf_enable = net->sctp.addip_enable;
        ep->auth_enable = net->sctp.auth_enable;
        if (ep->auth_enable) {
                if (sctp_auth_init(ep, gfp))
                        goto nomem;
                if (ep->asconf_enable) {
                        sctp_auth_ep_add_chunkid(ep, SCTP_CID_ASCONF);
                        sctp_auth_ep_add_chunkid(ep, SCTP_CID_ASCONF_ACK);
                }
        }

        /* Initialize the base structure. */
        /* What type of endpoint are we?  */
        ep->base.type = SCTP_EP_TYPE_SOCKET;

        /* Initialize the basic object fields. */
        refcount_set(&ep->base.refcnt, 1);
        ep->base.dead = false;

        /* Create an input queue.  */
        sctp_inq_init(&ep->base.inqueue);

        /* Set its top-half handler */
        sctp_inq_set_th_handler(&ep->base.inqueue, sctp_endpoint_bh_rcv);

        /* Initialize the bind addr area */
        sctp_bind_addr_init(&ep->base.bind_addr, 0);

        /* Create the lists of associations.  */
        INIT_LIST_HEAD(&ep->asocs);

        /* Use SCTP specific send buffer space queues.  */
        ep->sndbuf_policy = net->sctp.sndbuf_policy;

        sk->sk_data_ready = sctp_data_ready;
        sk->sk_write_space = sctp_write_space;
        sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);

        /* Get the receive buffer policy for this endpoint */
        ep->rcvbuf_policy = net->sctp.rcvbuf_policy;

        /* Generate the cookie authentication key. */
        gen_cookie_auth_key(&ep->cookie_auth_key);

        /* SCTP-AUTH extensions*/
        INIT_LIST_HEAD(&ep->endpoint_shared_keys);
        null_key = sctp_auth_shkey_create(0, gfp);
        if (!null_key)
                goto nomem_shkey;

        list_add(&null_key->key_list, &ep->endpoint_shared_keys);

        /* Add the null key to the endpoint shared keys list and
         * set the hmcas and chunks pointers.
         */
        ep->prsctp_enable = net->sctp.prsctp_enable;
        ep->reconf_enable = net->sctp.reconf_enable;
        ep->ecn_enable = net->sctp.ecn_enable;

        /* Remember who we are attached to.  */
        ep->base.sk = sk;
        ep->base.net = sock_net(sk);
        sock_hold(ep->base.sk);

        return ep;

nomem_shkey:
        sctp_auth_free(ep);
nomem:
        return NULL;

}

/* Create a sctp_endpoint with all that boring stuff initialized.
 * Returns NULL if there isn't enough memory.
 */
struct sctp_endpoint *sctp_endpoint_new(struct sock *sk, gfp_t gfp)
{
        struct sctp_endpoint *ep;

        /* Build a local endpoint. */
        ep = kzalloc_obj(*ep, gfp);
        if (!ep)
                goto fail;

        if (!sctp_endpoint_init(ep, sk, gfp))
                goto fail_init;

        SCTP_DBG_OBJCNT_INC(ep);
        return ep;

fail_init:
        kfree(ep);
fail:
        return NULL;
}

/* Add an association to an endpoint.  */
void sctp_endpoint_add_asoc(struct sctp_endpoint *ep,
                            struct sctp_association *asoc)
{
        struct sock *sk = ep->base.sk;

        /* If this is a temporary association, don't bother
         * since we'll be removing it shortly and don't
         * want anyone to find it anyway.
         */
        if (asoc->temp)
                return;

        /* Now just add it to our list of asocs */
        list_add_tail(&asoc->asocs, &ep->asocs);

        /* Increment the backlog value for a TCP-style listening socket. */
        if (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING))
                sk_acceptq_added(sk);
}

/* Free the endpoint structure.  Delay cleanup until
 * all users have released their reference count on this structure.
 */
void sctp_endpoint_free(struct sctp_endpoint *ep)
{
        ep->base.dead = true;

        inet_sk_set_state(ep->base.sk, SCTP_SS_CLOSED);

        /* Unlink this endpoint, so we can't find it again! */
        sctp_unhash_endpoint(ep);

        sctp_endpoint_put(ep);
}

/* Final destructor for endpoint.  */
static void sctp_endpoint_destroy_rcu(struct rcu_head *head)
{
        struct sctp_endpoint *ep = container_of(head, struct sctp_endpoint, rcu);
        struct sock *sk = ep->base.sk;

        sctp_sk(sk)->ep = NULL;
        sock_put(sk);

        kfree(ep);
        SCTP_DBG_OBJCNT_DEC(ep);
}

static void sctp_endpoint_destroy(struct sctp_endpoint *ep)
{
        struct sock *sk;

        if (unlikely(!ep->base.dead)) {
                WARN(1, "Attempt to destroy undead endpoint %p!\n", ep);
                return;
        }

        /* SCTP-AUTH: Free up AUTH releated data such as shared keys
         * chunks and hmacs arrays that were allocated
         */
        sctp_auth_destroy_keys(&ep->endpoint_shared_keys);
        sctp_auth_free(ep);

        /* Cleanup. */
        sctp_inq_free(&ep->base.inqueue);
        sctp_bind_addr_free(&ep->base.bind_addr);

        memzero_explicit(&ep->cookie_auth_key, sizeof(ep->cookie_auth_key));

        sk = ep->base.sk;
        /* Remove and free the port */
        if (sctp_sk(sk)->bind_hash)
                sctp_put_port(sk);

        call_rcu(&ep->rcu, sctp_endpoint_destroy_rcu);
}

/* Hold a reference to an endpoint. */
int sctp_endpoint_hold(struct sctp_endpoint *ep)
{
        return refcount_inc_not_zero(&ep->base.refcnt);
}

/* Release a reference to an endpoint and clean up if there are
 * no more references.
 */
void sctp_endpoint_put(struct sctp_endpoint *ep)
{
        if (refcount_dec_and_test(&ep->base.refcnt))
                sctp_endpoint_destroy(ep);
}

/* Is this the endpoint we are looking for?  */
struct sctp_endpoint *sctp_endpoint_is_match(struct sctp_endpoint *ep,
                                               struct net *net,
                                               const union sctp_addr *laddr,
                                               int dif, int sdif)
{
        int bound_dev_if = READ_ONCE(ep->base.sk->sk_bound_dev_if);
        struct sctp_endpoint *retval = NULL;

        if (net_eq(ep->base.net, net) &&
            sctp_sk_bound_dev_eq(net, bound_dev_if, dif, sdif) &&
            (htons(ep->base.bind_addr.port) == laddr->v4.sin_port)) {
                if (sctp_bind_addr_match(&ep->base.bind_addr, laddr,
                                         sctp_sk(ep->base.sk)))
                        retval = ep;
        }

        return retval;
}

/* Find the association that goes with this chunk.
 * We lookup the transport from hashtable at first, then get association
 * through t->assoc.
 */
struct sctp_association *sctp_endpoint_lookup_assoc(
        const struct sctp_endpoint *ep,
        const union sctp_addr *paddr,
        struct sctp_transport **transport)
{
        struct sctp_association *asoc = NULL;
        struct sctp_transport *t;

        *transport = NULL;

        /* If the local port is not set, there can't be any associations
         * on this endpoint.
         */
        if (!ep->base.bind_addr.port)
                return NULL;

        rcu_read_lock();
        t = sctp_epaddr_lookup_transport(ep, paddr);
        if (!t)
                goto out;

        *transport = t;
        asoc = t->asoc;
out:
        rcu_read_unlock();
        return asoc;
}

/* Look for any peeled off association from the endpoint that matches the
 * given peer address.
 */
bool sctp_endpoint_is_peeled_off(struct sctp_endpoint *ep,
                                 const union sctp_addr *paddr)
{
        int bound_dev_if = READ_ONCE(ep->base.sk->sk_bound_dev_if);
        struct sctp_sockaddr_entry *addr;
        struct net *net = ep->base.net;
        struct sctp_bind_addr *bp;

        bp = &ep->base.bind_addr;
        /* This function is called with the socket lock held,
         * so the address_list can not change.
         */
        list_for_each_entry(addr, &bp->address_list, list) {
                if (sctp_has_association(net, &addr->a, paddr,
                                         bound_dev_if, bound_dev_if))
                        return true;
        }

        return false;
}

/* Do delayed input processing.  This is scheduled by sctp_rcv().
 * This may be called on BH or task time.
 */
static void sctp_endpoint_bh_rcv(struct work_struct *work)
{
        struct sctp_endpoint *ep =
                container_of(work, struct sctp_endpoint,
                             base.inqueue.immediate);
        struct sctp_association *asoc;
        struct sock *sk;
        struct net *net;
        struct sctp_transport *transport;
        struct sctp_chunk *chunk;
        struct sctp_inq *inqueue;
        union sctp_subtype subtype;
        enum sctp_state state;
        int error = 0;
        int first_time = 1;     /* is this the first time through the loop */

        if (ep->base.dead)
                return;

        asoc = NULL;
        inqueue = &ep->base.inqueue;
        sk = ep->base.sk;
        net = sock_net(sk);

        while (NULL != (chunk = sctp_inq_pop(inqueue))) {
                subtype = SCTP_ST_CHUNK(chunk->chunk_hdr->type);

                /* If the first chunk in the packet is AUTH, do special
                 * processing specified in Section 6.3 of SCTP-AUTH spec
                 */
                if (first_time && (subtype.chunk == SCTP_CID_AUTH)) {
                        struct sctp_chunkhdr *next_hdr;

                        next_hdr = sctp_inq_peek(inqueue);
                        if (!next_hdr)
                                goto normal;

                        /* If the next chunk is COOKIE-ECHO, skip the AUTH
                         * chunk while saving a pointer to it so we can do
                         * Authentication later (during cookie-echo
                         * processing).
                         */
                        if (next_hdr->type == SCTP_CID_COOKIE_ECHO) {
                                chunk->auth_chunk = skb_clone(chunk->skb,
                                                                GFP_ATOMIC);
                                chunk->auth = 1;
                                continue;
                        }
                }
normal:
                /* We might have grown an association since last we
                 * looked, so try again.
                 *
                 * This happens when we've just processed our
                 * COOKIE-ECHO chunk.
                 */
                if (NULL == chunk->asoc) {
                        asoc = sctp_endpoint_lookup_assoc(ep,
                                                          sctp_source(chunk),
                                                          &transport);
                        chunk->asoc = asoc;
                        chunk->transport = transport;
                }

                state = asoc ? asoc->state : SCTP_STATE_CLOSED;
                if (sctp_auth_recv_cid(subtype.chunk, asoc) && !chunk->auth)
                        continue;

                /* Remember where the last DATA chunk came from so we
                 * know where to send the SACK.
                 */
                if (asoc && sctp_chunk_is_data(chunk))
                        asoc->peer.last_data_from = chunk->transport;
                else {
                        SCTP_INC_STATS(ep->base.net, SCTP_MIB_INCTRLCHUNKS);
                        if (asoc)
                                asoc->stats.ictrlchunks++;
                }

                if (chunk->transport)
                        chunk->transport->last_time_heard = ktime_get();

                error = sctp_do_sm(net, SCTP_EVENT_T_CHUNK, subtype, state,
                                   ep, asoc, chunk, GFP_ATOMIC);

                if (error && chunk)
                        chunk->pdiscard = 1;

                /* Check to see if the endpoint is freed in response to
                 * the incoming chunk. If so, get out of the while loop.
                 */
                if (!sctp_sk(sk)->ep)
                        break;

                if (first_time)
                        first_time = 0;
        }
}