/*
 * Copyright (C)2002 USAGI/WIDE Project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Authors
 *
 *      Mitsuru KANDA @USAGI       : IPv6 Support
 *      Kazunori MIYAZAWA @USAGI   :
 *      Kunihiro Ishiguro <kunihiro@ipinfusion.com>
 *
 *      This file is derived from net/ipv4/ah.c.
 */

#include <linux/module.h>
#include <net/ip.h>
#include <net/ah.h>
#include <linux/crypto.h>
#include <linux/pfkeyv2.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <net/icmp.h>
#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/xfrm.h>

static int zero_out_mutable_opts(struct ipv6_opt_hdr *opthdr)
{
        u8 *opt = (u8 *)opthdr;
        int len = ipv6_optlen(opthdr);
        int off = 0;
        int optlen = 0;

        off += 2;
        len -= 2;

        while (len > 0) {

                switch (opt[off]) {

                case IPV6_TLV_PAD0:
                        optlen = 1;
                        break;
                default:
                        if (len < 2)
                                goto bad;
                        optlen = opt[off+1]+2;
                        if (len < optlen)
                                goto bad;
                        if (opt[off] & 0x20)
                                memset(&opt[off+2], 0, opt[off+1]);
                        break;
                }

                off += optlen;
                len -= optlen;
        }
        if (len == 0)
                return 1;

bad:
        return 0;
}

#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
/**
 *      ipv6_rearrange_destopt - rearrange IPv6 destination options header
 *      @iph: IPv6 header
 *      @destopt: destionation options header
 */
static void ipv6_rearrange_destopt(struct ipv6hdr *iph, struct ipv6_opt_hdr *destopt)
{
        u8 *opt = (u8 *)destopt;
        int len = ipv6_optlen(destopt);
        int off = 0;
        int optlen = 0;

        off += 2;
        len -= 2;

        while (len > 0) {

                switch (opt[off]) {

                case IPV6_TLV_PAD0:
                        optlen = 1;
                        break;
                default:
                        if (len < 2)
                                goto bad;
                        optlen = opt[off+1]+2;
                        if (len < optlen)
                                goto bad;

                        /* Rearrange the source address in @iph and the
                         * addresses in home address option for final source.
                         * See 11.3.2 of RFC 3775 for details.
                         */
                        if (opt[off] == IPV6_TLV_HAO) {
                                struct in6_addr final_addr;
                                struct ipv6_destopt_hao *hao;

                                hao = (struct ipv6_destopt_hao *)&opt[off];
                                if (hao->length != sizeof(hao->addr)) {
                                        if (net_ratelimit())
                                                printk(KERN_WARNING "destopt hao: invalid header length: %u\n", hao->length);
                                        goto bad;
                                }
                                ipv6_addr_copy(&final_addr, &hao->addr);
                                ipv6_addr_copy(&hao->addr, &iph->saddr);
                                ipv6_addr_copy(&iph->saddr, &final_addr);
                        }
                        break;
                }

                off += optlen;
                len -= optlen;
        }
        /* Note: ok if len == 0 */
bad:
        return;
}
#else
static void ipv6_rearrange_destopt(struct ipv6hdr *iph, struct ipv6_opt_hdr *destopt) {}
#endif

/**
 *      ipv6_rearrange_rthdr - rearrange IPv6 routing header
 *      @iph: IPv6 header
 *      @rthdr: routing header
 *
 *      Rearrange the destination address in @iph and the addresses in @rthdr
 *      so that they appear in the order they will at the final destination.
 *      See Appendix A2 of RFC 2402 for details.
 */
static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
{
        int segments, segments_left;
        struct in6_addr *addrs;
        struct in6_addr final_addr;

        segments_left = rthdr->segments_left;
        if (segments_left == 0)
                return;
        rthdr->segments_left = 0;

        /* The value of rthdr->hdrlen has been verified either by the system
         * call if it is locally generated, or by ipv6_rthdr_rcv() for incoming
         * packets.  So we can assume that it is even and that segments is
         * greater than or equal to segments_left.
         *
         * For the same reason we can assume that this option is of type 0.
         */
        segments = rthdr->hdrlen >> 1;

        addrs = ((struct rt0_hdr *)rthdr)->addr;
        ipv6_addr_copy(&final_addr, addrs + segments - 1);

        addrs += segments - segments_left;
        memmove(addrs + 1, addrs, (segments_left - 1) * sizeof(*addrs));

        ipv6_addr_copy(addrs, &iph->daddr);
        ipv6_addr_copy(&iph->daddr, &final_addr);
}

static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len, int dir)
{
        union {
                struct ipv6hdr *iph;
                struct ipv6_opt_hdr *opth;
                struct ipv6_rt_hdr *rth;
                char *raw;
        } exthdr = { .iph = iph };
        char *end = exthdr.raw + len;
        int nexthdr = iph->nexthdr;

        exthdr.iph++;

        while (exthdr.raw < end) {
                switch (nexthdr) {
                case NEXTHDR_DEST:
                        if (dir == XFRM_POLICY_OUT)
                                ipv6_rearrange_destopt(iph, exthdr.opth);
                case NEXTHDR_HOP:
                        if (!zero_out_mutable_opts(exthdr.opth)) {
                                LIMIT_NETDEBUG(
                                        KERN_WARNING "overrun %sopts\n",
                                        nexthdr == NEXTHDR_HOP ?
                                                "hop" : "dest");
                                return -EINVAL;
                        }
                        break;

                case NEXTHDR_ROUTING:
                        ipv6_rearrange_rthdr(iph, exthdr.rth);
                        break;

                default :
                        return 0;
                }

                nexthdr = exthdr.opth->nexthdr;
                exthdr.raw += ipv6_optlen(exthdr.opth);
        }

        return 0;
}

static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
{
        int err;
        int extlen;
        struct ipv6hdr *top_iph;
        struct ip_auth_hdr *ah;
        struct ah_data *ahp;
        u8 nexthdr;
        char tmp_base[8];
        struct {
#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
                struct in6_addr saddr;
#endif
                struct in6_addr daddr;
                char hdrs[0];
        } *tmp_ext;

        skb_push(skb, -skb_network_offset(skb));
        top_iph = ipv6_hdr(skb);
        top_iph->payload_len = htons(skb->len - sizeof(*top_iph));

        nexthdr = *skb_mac_header(skb);
        *skb_mac_header(skb) = IPPROTO_AH;

        /* When there are no extension headers, we only need to save the first
         * 8 bytes of the base IP header.
         */
        memcpy(tmp_base, top_iph, sizeof(tmp_base));

        tmp_ext = NULL;
        extlen = skb_transport_offset(skb) - sizeof(struct ipv6hdr);
        if (extlen) {
                extlen += sizeof(*tmp_ext);
                tmp_ext = kmalloc(extlen, GFP_ATOMIC);
                if (!tmp_ext) {
                        err = -ENOMEM;
                        goto error;
                }
#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
                memcpy(tmp_ext, &top_iph->saddr, extlen);
#else
                memcpy(tmp_ext, &top_iph->daddr, extlen);
#endif
                err = ipv6_clear_mutable_options(top_iph,
                                                 extlen - sizeof(*tmp_ext) +
                                                 sizeof(*top_iph),
                                                 XFRM_POLICY_OUT);
                if (err)
                        goto error_free_iph;
        }

        ah = ip_auth_hdr(skb);
        ah->nexthdr = nexthdr;

        top_iph->priority    = 0;
        top_iph->flow_lbl[0] = 0;
        top_iph->flow_lbl[1] = 0;
        top_iph->flow_lbl[2] = 0;
        top_iph->hop_limit   = 0;

        ahp = x->data;
        ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;

        ah->reserved = 0;
        ah->spi = x->id.spi;
        ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output);

        spin_lock_bh(&x->lock);
        err = ah_mac_digest(ahp, skb, ah->auth_data);
        memcpy(ah->auth_data, ahp->work_icv, ahp->icv_trunc_len);
        spin_unlock_bh(&x->lock);

        if (err)
                goto error_free_iph;

        memcpy(top_iph, tmp_base, sizeof(tmp_base));
        if (tmp_ext) {
#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
                memcpy(&top_iph->saddr, tmp_ext, extlen);
#else
                memcpy(&top_iph->daddr, tmp_ext, extlen);
#endif
error_free_iph:
                kfree(tmp_ext);
        }

error:
        return err;
}

static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
{
        /*
         * Before process AH
         * [IPv6][Ext1][Ext2][AH][Dest][Payload]
         * |<-------------->| hdr_len
         *
         * To erase AH:
         * Keeping copy of cleared headers. After AH processing,
         * Moving the pointer of skb->network_header by using skb_pull as long
         * as AH header length. Then copy back the copy as long as hdr_len
         * If destination header following AH exists, copy it into after [Ext2].
         *
         * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
         * There is offset of AH before IPv6 header after the process.
         */

        struct ip_auth_hdr *ah;
        struct ipv6hdr *ip6h;
        struct ah_data *ahp;
        unsigned char *tmp_hdr = NULL;
        u16 hdr_len;
        u16 ah_hlen;
        int nexthdr;
        int err = -EINVAL;

        if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
                goto out;

        /* We are going to _remove_ AH header to keep sockets happy,
         * so... Later this can change. */
        if (skb_cloned(skb) &&
            pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
                goto out;

        skb->ip_summed = CHECKSUM_NONE;

        hdr_len = skb->data - skb_network_header(skb);
        ah = (struct ip_auth_hdr *)skb->data;
        ahp = x->data;
        nexthdr = ah->nexthdr;
        ah_hlen = (ah->hdrlen + 2) << 2;

        if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
            ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
                goto out;

        if (!pskb_may_pull(skb, ah_hlen))
                goto out;

        tmp_hdr = kmemdup(skb_network_header(skb), hdr_len, GFP_ATOMIC);
        if (!tmp_hdr)
                goto out;
        ip6h = ipv6_hdr(skb);
        if (ipv6_clear_mutable_options(ip6h, hdr_len, XFRM_POLICY_IN))
                goto free_out;
        ip6h->priority    = 0;
        ip6h->flow_lbl[0] = 0;
        ip6h->flow_lbl[1] = 0;
        ip6h->flow_lbl[2] = 0;
        ip6h->hop_limit   = 0;

        spin_lock(&x->lock);
        {
                u8 auth_data[MAX_AH_AUTH_LEN];

                memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
                memset(ah->auth_data, 0, ahp->icv_trunc_len);
                skb_push(skb, hdr_len);
                err = ah_mac_digest(ahp, skb, ah->auth_data);
                if (err)
                        goto unlock;
                if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len))
                        err = -EBADMSG;
        }
unlock:
        spin_unlock(&x->lock);

        if (err)
                goto free_out;

        skb->network_header += ah_hlen;
        memcpy(skb_network_header(skb), tmp_hdr, hdr_len);
        skb->transport_header = skb->network_header;
        __skb_pull(skb, ah_hlen + hdr_len);

        kfree(tmp_hdr);

        return nexthdr;

free_out:
        kfree(tmp_hdr);
out:
        return err;
}

static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
                    u8 type, u8 code, int offset, __be32 info)
{
        struct net *net = dev_net(skb->dev);
        struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
        struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
        struct xfrm_state *x;

        if (type != ICMPV6_DEST_UNREACH &&
            type != ICMPV6_PKT_TOOBIG)
                return;

        x = xfrm_state_lookup(net, (xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
        if (!x)
                return;

        NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/%pI6\n",
                 ntohl(ah->spi), &iph->daddr);

        xfrm_state_put(x);
}

static int ah6_init_state(struct xfrm_state *x)
{
        struct ah_data *ahp = NULL;
        struct xfrm_algo_desc *aalg_desc;
        struct crypto_hash *tfm;

        if (!x->aalg)
                goto error;

        if (x->encap)
                goto error;

        ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
        if (ahp == NULL)
                return -ENOMEM;

        tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(tfm))
                goto error;

        ahp->tfm = tfm;
        if (crypto_hash_setkey(tfm, x->aalg->alg_key,
                               (x->aalg->alg_key_len + 7) / 8))
                goto error;

        /*
         * Lookup the algorithm description maintained by xfrm_algo,
         * verify crypto transform properties, and store information
         * we need for AH processing.  This lookup cannot fail here
         * after a successful crypto_alloc_hash().
         */
        aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
        BUG_ON(!aalg_desc);

        if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
            crypto_hash_digestsize(tfm)) {
                printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
                       x->aalg->alg_name, crypto_hash_digestsize(tfm),
                       aalg_desc->uinfo.auth.icv_fullbits/8);
                goto error;
        }

        ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
        ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;

        BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);

        ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
        if (!ahp->work_icv)
                goto error;

        x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
                                          ahp->icv_trunc_len);
        switch (x->props.mode) {
        case XFRM_MODE_BEET:
        case XFRM_MODE_TRANSPORT:
                break;
        case XFRM_MODE_TUNNEL:
                x->props.header_len += sizeof(struct ipv6hdr);
                break;
        default:
                goto error;
        }
        x->data = ahp;

        return 0;

error:
        if (ahp) {
                kfree(ahp->work_icv);
                crypto_free_hash(ahp->tfm);
                kfree(ahp);
        }
        return -EINVAL;
}

static void ah6_destroy(struct xfrm_state *x)
{
        struct ah_data *ahp = x->data;

        if (!ahp)
                return;

        kfree(ahp->work_icv);
        crypto_free_hash(ahp->tfm);
        kfree(ahp);
}

static const struct xfrm_type ah6_type =
{
        .description    = "AH6",
        .owner          = THIS_MODULE,
        .proto          = IPPROTO_AH,
        .flags          = XFRM_TYPE_REPLAY_PROT,
        .init_state     = ah6_init_state,
        .destructor     = ah6_destroy,
        .input          = ah6_input,
        .output         = ah6_output,
        .hdr_offset     = xfrm6_find_1stfragopt,
};

static const struct inet6_protocol ah6_protocol = {
        .handler        =       xfrm6_rcv,
        .err_handler    =       ah6_err,
        .flags          =       INET6_PROTO_NOPOLICY,
};

static int __init ah6_init(void)
{
        if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
                printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
                return -EAGAIN;
        }

        if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
                printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
                xfrm_unregister_type(&ah6_type, AF_INET6);
                return -EAGAIN;
        }

        return 0;
}

static void __exit ah6_fini(void)
{
        if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
                printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");

        if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
                printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");

}

module_init(ah6_init);
module_exit(ah6_fini);

MODULE_LICENSE("GPL");
MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_AH);