/*
 * 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.
 */

#define pr_fmt(fmt) "IPv6: " fmt

#include <crypto/hash.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <net/ip.h>
#include <net/ah.h>
#include <linux/crypto.h>
#include <linux/pfkeyv2.h>
#include <linux/string.h>
#include <linux/scatterlist.h>
#include <net/ip6_route.h>
#include <net/icmp.h>
#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/xfrm.h>

#define IPV6HDR_BASELEN 8

struct tmp_ext {
#if IS_ENABLED(CONFIG_IPV6_MIP6)
                struct in6_addr saddr;
#endif
                struct in6_addr daddr;
                char hdrs[0];
};

struct ah_skb_cb {
        struct xfrm_skb_cb xfrm;
        void *tmp;
};

#define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))

static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags,
                          unsigned int size)
{
        unsigned int len;

        len = size + crypto_ahash_digestsize(ahash) +
              (crypto_ahash_alignmask(ahash) &
               ~(crypto_tfm_ctx_alignment() - 1));

        len = ALIGN(len, crypto_tfm_ctx_alignment());

        len += sizeof(struct ahash_request) + crypto_ahash_reqsize(ahash);
        len = ALIGN(len, __alignof__(struct scatterlist));

        len += sizeof(struct scatterlist) * nfrags;

        return kmalloc(len, GFP_ATOMIC);
}

static inline struct tmp_ext *ah_tmp_ext(void *base)
{
        return base + IPV6HDR_BASELEN;
}

static inline u8 *ah_tmp_auth(u8 *tmp, unsigned int offset)
{
        return tmp + offset;
}

static inline u8 *ah_tmp_icv(struct crypto_ahash *ahash, void *tmp,
                             unsigned int offset)
{
        return PTR_ALIGN((u8 *)tmp + offset, crypto_ahash_alignmask(ahash) + 1);
}

static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
                                               u8 *icv)
{
        struct ahash_request *req;

        req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
                                crypto_tfm_ctx_alignment());

        ahash_request_set_tfm(req, ahash);

        return req;
}

static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
                                             struct ahash_request *req)
{
        return (void *)ALIGN((unsigned long)(req + 1) +
                             crypto_ahash_reqsize(ahash),
                             __alignof__(struct scatterlist));
}

static bool 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_PAD1:
                        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 true;

bad:
        return false;
}

#if IS_ENABLED(CONFIG_IPV6_MIP6)
/**
 *      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_PAD1:
                        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)) {
                                        net_warn_ratelimited("destopt hao: invalid header length: %u\n",
                                                             hao->length);
                                        goto bad;
                                }
                                final_addr = hao->addr;
                                hao->addr = iph->saddr;
                                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;
        final_addr = addrs[segments - 1];

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

        addrs[0] = iph->daddr;
        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 void ah6_output_done(struct crypto_async_request *base, int err)
{
        int extlen;
        u8 *iph_base;
        u8 *icv;
        struct sk_buff *skb = base->data;
        struct xfrm_state *x = skb_dst(skb)->xfrm;
        struct ah_data *ahp = x->data;
        struct ipv6hdr *top_iph = ipv6_hdr(skb);
        struct ip_auth_hdr *ah = ip_auth_hdr(skb);
        struct tmp_ext *iph_ext;

        extlen = skb_network_header_len(skb) - sizeof(struct ipv6hdr);
        if (extlen)
                extlen += sizeof(*iph_ext);

        iph_base = AH_SKB_CB(skb)->tmp;
        iph_ext = ah_tmp_ext(iph_base);
        icv = ah_tmp_icv(ahp->ahash, iph_ext, extlen);

        memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
        memcpy(top_iph, iph_base, IPV6HDR_BASELEN);

        if (extlen) {
#if IS_ENABLED(CONFIG_IPV6_MIP6)
                memcpy(&top_iph->saddr, iph_ext, extlen);
#else
                memcpy(&top_iph->daddr, iph_ext, extlen);
#endif
        }

        kfree(AH_SKB_CB(skb)->tmp);
        xfrm_output_resume(skb, err);
}

static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
{
        int err;
        int nfrags;
        int extlen;
        u8 *iph_base;
        u8 *icv;
        u8 nexthdr;
        struct sk_buff *trailer;
        struct crypto_ahash *ahash;
        struct ahash_request *req;
        struct scatterlist *sg;
        struct ipv6hdr *top_iph;
        struct ip_auth_hdr *ah;
        struct ah_data *ahp;
        struct tmp_ext *iph_ext;

        ahp = x->data;
        ahash = ahp->ahash;

        if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
                goto out;
        nfrags = err;

        skb_push(skb, -skb_network_offset(skb));
        extlen = skb_network_header_len(skb) - sizeof(struct ipv6hdr);
        if (extlen)
                extlen += sizeof(*iph_ext);

        err = -ENOMEM;
        iph_base = ah_alloc_tmp(ahash, nfrags, IPV6HDR_BASELEN + extlen);
        if (!iph_base)
                goto out;

        iph_ext = ah_tmp_ext(iph_base);
        icv = ah_tmp_icv(ahash, iph_ext, extlen);
        req = ah_tmp_req(ahash, icv);
        sg = ah_req_sg(ahash, req);

        ah = ip_auth_hdr(skb);
        memset(ah->auth_data, 0, ahp->icv_trunc_len);

        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(iph_base, top_iph, IPV6HDR_BASELEN);

        if (extlen) {
#if IS_ENABLED(CONFIG_IPV6_MIP6)
                memcpy(iph_ext, &top_iph->saddr, extlen);
#else
                memcpy(iph_ext, &top_iph->daddr, extlen);
#endif
                err = ipv6_clear_mutable_options(top_iph,
                                                 extlen - sizeof(*iph_ext) +
                                                 sizeof(*top_iph),
                                                 XFRM_POLICY_OUT);
                if (err)
                        goto out_free;
        }

        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;

        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.low);

        sg_init_table(sg, nfrags);
        skb_to_sgvec(skb, sg, 0, skb->len);

        ahash_request_set_crypt(req, sg, icv, skb->len);
        ahash_request_set_callback(req, 0, ah6_output_done, skb);

        AH_SKB_CB(skb)->tmp = iph_base;

        err = crypto_ahash_digest(req);
        if (err) {
                if (err == -EINPROGRESS)
                        goto out;

                if (err == -EBUSY)
                        err = NET_XMIT_DROP;
                goto out_free;
        }

        memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
        memcpy(top_iph, iph_base, IPV6HDR_BASELEN);

        if (extlen) {
#if IS_ENABLED(CONFIG_IPV6_MIP6)
                memcpy(&top_iph->saddr, iph_ext, extlen);
#else
                memcpy(&top_iph->daddr, iph_ext, extlen);
#endif
        }

out_free:
        kfree(iph_base);
out:
        return err;
}

static void ah6_input_done(struct crypto_async_request *base, int err)
{
        u8 *auth_data;
        u8 *icv;
        u8 *work_iph;
        struct sk_buff *skb = base->data;
        struct xfrm_state *x = xfrm_input_state(skb);
        struct ah_data *ahp = x->data;
        struct ip_auth_hdr *ah = ip_auth_hdr(skb);
        int hdr_len = skb_network_header_len(skb);
        int ah_hlen = (ah->hdrlen + 2) << 2;

        work_iph = AH_SKB_CB(skb)->tmp;
        auth_data = ah_tmp_auth(work_iph, hdr_len);
        icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);

        err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
        if (err)
                goto out;

        err = ah->nexthdr;

        skb->network_header += ah_hlen;
        memcpy(skb_network_header(skb), work_iph, hdr_len);
        __skb_pull(skb, ah_hlen + hdr_len);
        if (x->props.mode == XFRM_MODE_TUNNEL)
                skb_reset_transport_header(skb);
        else
                skb_set_transport_header(skb, -hdr_len);
out:
        kfree(AH_SKB_CB(skb)->tmp);
        xfrm_input_resume(skb, 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.
         */

        u8 *auth_data;
        u8 *icv;
        u8 *work_iph;
        struct sk_buff *trailer;
        struct crypto_ahash *ahash;
        struct ahash_request *req;
        struct scatterlist *sg;
        struct ip_auth_hdr *ah;
        struct ipv6hdr *ip6h;
        struct ah_data *ahp;
        u16 hdr_len;
        u16 ah_hlen;
        int nexthdr;
        int nfrags;
        int err = -ENOMEM;

        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_unclone(skb, GFP_ATOMIC))
                goto out;

        skb->ip_summed = CHECKSUM_NONE;

        hdr_len = skb_network_header_len(skb);
        ah = (struct ip_auth_hdr *)skb->data;
        ahp = x->data;
        ahash = ahp->ahash;

        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;


        if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
                goto out;
        nfrags = err;

        ah = (struct ip_auth_hdr *)skb->data;
        ip6h = ipv6_hdr(skb);

        skb_push(skb, hdr_len);

        work_iph = ah_alloc_tmp(ahash, nfrags, hdr_len + ahp->icv_trunc_len);
        if (!work_iph)
                goto out;

        auth_data = ah_tmp_auth(work_iph, hdr_len);
        icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
        req = ah_tmp_req(ahash, icv);
        sg = ah_req_sg(ahash, req);

        memcpy(work_iph, ip6h, hdr_len);
        memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
        memset(ah->auth_data, 0, ahp->icv_trunc_len);

        if (ipv6_clear_mutable_options(ip6h, hdr_len, XFRM_POLICY_IN))
                goto out_free;

        ip6h->priority    = 0;
        ip6h->flow_lbl[0] = 0;
        ip6h->flow_lbl[1] = 0;
        ip6h->flow_lbl[2] = 0;
        ip6h->hop_limit   = 0;

        sg_init_table(sg, nfrags);
        skb_to_sgvec(skb, sg, 0, skb->len);

        ahash_request_set_crypt(req, sg, icv, skb->len);
        ahash_request_set_callback(req, 0, ah6_input_done, skb);

        AH_SKB_CB(skb)->tmp = work_iph;

        err = crypto_ahash_digest(req);
        if (err) {
                if (err == -EINPROGRESS)
                        goto out;

                goto out_free;
        }

        err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
        if (err)
                goto out_free;

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

        if (x->props.mode == XFRM_MODE_TUNNEL)
                skb_reset_transport_header(skb);
        else
                skb_set_transport_header(skb, -hdr_len);

        err = nexthdr;

out_free:
        kfree(work_iph);
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 &&
            type != NDISC_REDIRECT)
                return;

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

        if (type == NDISC_REDIRECT)
                ip6_redirect(skb, net, 0, 0);
        else
                ip6_update_pmtu(skb, net, info, 0, 0);
        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_ahash *ahash;

        if (!x->aalg)
                goto error;

        if (x->encap)
                goto error;

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

        ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
        if (IS_ERR(ahash))
                goto error;

        ahp->ahash = ahash;
        if (crypto_ahash_setkey(ahash, 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_ahash_digestsize(ahash)) {
                pr_info("AH: %s digestsize %u != %hu\n",
                        x->aalg->alg_name, crypto_ahash_digestsize(ahash),
                        aalg_desc->uinfo.auth.icv_fullbits/8);
                goto error;
        }

        ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
        ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;

        BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);

        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) {
                crypto_free_ahash(ahp->ahash);
                kfree(ahp);
        }
        return -EINVAL;
}

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

        if (!ahp)
                return;

        crypto_free_ahash(ahp->ahash);
        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) {
                pr_info("%s: can't add xfrm type\n", __func__);
                return -EAGAIN;
        }

        if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
                pr_info("%s: can't add protocol\n", __func__);
                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)
                pr_info("%s: can't remove protocol\n", __func__);

        if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
                pr_info("%s: can't remove xfrm type\n", __func__);

}

module_init(ah6_init);
module_exit(ah6_fini);

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