#include <crypto/aead.h>
#include <crypto/authenc.h>
#include <linux/err.h>
#include <linux/module.h>
#include <net/ip.h>
#include <net/xfrm.h>
#include <net/esp.h>
#include <linux/scatterlist.h>
#include <linux/kernel.h>
#include <linux/pfkeyv2.h>
#include <linux/rtnetlink.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/in6.h>
#include <net/icmp.h>
#include <net/protocol.h>
#include <net/udp.h>

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

#define ESP_SKB_CB(__skb) ((struct esp_skb_cb *)&((__skb)->cb[0]))

/*
 * Allocate an AEAD request structure with extra space for SG and IV.
 *
 * For alignment considerations the IV is placed at the front, followed
 * by the request and finally the SG list.
 *
 * TODO: Use spare space in skb for this where possible.
 */
static void *esp_alloc_tmp(struct crypto_aead *aead, int nfrags)
{
        unsigned int len;

        len = crypto_aead_ivsize(aead);
        if (len) {
                len += crypto_aead_alignmask(aead) &
                       ~(crypto_tfm_ctx_alignment() - 1);
                len = ALIGN(len, crypto_tfm_ctx_alignment());
        }

        len += sizeof(struct aead_givcrypt_request) + crypto_aead_reqsize(aead);
        len = ALIGN(len, __alignof__(struct scatterlist));

        len += sizeof(struct scatterlist) * nfrags;

        return kmalloc(len, GFP_ATOMIC);
}

static inline u8 *esp_tmp_iv(struct crypto_aead *aead, void *tmp)
{
        return crypto_aead_ivsize(aead) ?
               PTR_ALIGN((u8 *)tmp, crypto_aead_alignmask(aead) + 1) : tmp;
}

static inline struct aead_givcrypt_request *esp_tmp_givreq(
        struct crypto_aead *aead, u8 *iv)
{
        struct aead_givcrypt_request *req;

        req = (void *)PTR_ALIGN(iv + crypto_aead_ivsize(aead),
                                crypto_tfm_ctx_alignment());
        aead_givcrypt_set_tfm(req, aead);
        return req;
}

static inline struct aead_request *esp_tmp_req(struct crypto_aead *aead, u8 *iv)
{
        struct aead_request *req;

        req = (void *)PTR_ALIGN(iv + crypto_aead_ivsize(aead),
                                crypto_tfm_ctx_alignment());
        aead_request_set_tfm(req, aead);
        return req;
}

static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead,
                                             struct aead_request *req)
{
        return (void *)ALIGN((unsigned long)(req + 1) +
                             crypto_aead_reqsize(aead),
                             __alignof__(struct scatterlist));
}

static inline struct scatterlist *esp_givreq_sg(
        struct crypto_aead *aead, struct aead_givcrypt_request *req)
{
        return (void *)ALIGN((unsigned long)(req + 1) +
                             crypto_aead_reqsize(aead),
                             __alignof__(struct scatterlist));
}

static void esp_output_done(struct crypto_async_request *base, int err)
{
        struct sk_buff *skb = base->data;

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

static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
{
        int err;
        struct ip_esp_hdr *esph;
        struct crypto_aead *aead;
        struct aead_givcrypt_request *req;
        struct scatterlist *sg;
        struct scatterlist *asg;
        struct esp_data *esp;
        struct sk_buff *trailer;
        void *tmp;
        u8 *iv;
        u8 *tail;
        int blksize;
        int clen;
        int alen;
        int nfrags;

        /* skb is pure payload to encrypt */

        err = -ENOMEM;

        /* Round to block size */
        clen = skb->len;

        esp = x->data;
        aead = esp->aead;
        alen = crypto_aead_authsize(aead);

        blksize = ALIGN(crypto_aead_blocksize(aead), 4);
        clen = ALIGN(clen + 2, blksize);
        if (esp->padlen)
                clen = ALIGN(clen, esp->padlen);

        if ((err = skb_cow_data(skb, clen - skb->len + alen, &trailer)) < 0)
                goto error;
        nfrags = err;

        tmp = esp_alloc_tmp(aead, nfrags + 1);
        if (!tmp)
                goto error;

        iv = esp_tmp_iv(aead, tmp);
        req = esp_tmp_givreq(aead, iv);
        asg = esp_givreq_sg(aead, req);
        sg = asg + 1;

        /* Fill padding... */
        tail = skb_tail_pointer(trailer);
        do {
                int i;
                for (i=0; i<clen-skb->len - 2; i++)
                        tail[i] = i + 1;
        } while (0);
        tail[clen - skb->len - 2] = (clen - skb->len) - 2;
        tail[clen - skb->len - 1] = *skb_mac_header(skb);
        pskb_put(skb, trailer, clen - skb->len + alen);

        skb_push(skb, -skb_network_offset(skb));
        esph = ip_esp_hdr(skb);
        *skb_mac_header(skb) = IPPROTO_ESP;

        /* this is non-NULL only with UDP Encapsulation */
        if (x->encap) {
                struct xfrm_encap_tmpl *encap = x->encap;
                struct udphdr *uh;
                __be32 *udpdata32;
                __be16 sport, dport;
                int encap_type;

                spin_lock_bh(&x->lock);
                sport = encap->encap_sport;
                dport = encap->encap_dport;
                encap_type = encap->encap_type;
                spin_unlock_bh(&x->lock);

                uh = (struct udphdr *)esph;
                uh->source = sport;
                uh->dest = dport;
                uh->len = htons(skb->len - skb_transport_offset(skb));
                uh->check = 0;

                switch (encap_type) {
                default:
                case UDP_ENCAP_ESPINUDP:
                        esph = (struct ip_esp_hdr *)(uh + 1);
                        break;
                case UDP_ENCAP_ESPINUDP_NON_IKE:
                        udpdata32 = (__be32 *)(uh + 1);
                        udpdata32[0] = udpdata32[1] = 0;
                        esph = (struct ip_esp_hdr *)(udpdata32 + 2);
                        break;
                }

                *skb_mac_header(skb) = IPPROTO_UDP;
        }

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

        sg_init_table(sg, nfrags);
        skb_to_sgvec(skb, sg,
                     esph->enc_data + crypto_aead_ivsize(aead) - skb->data,
                     clen + alen);
        sg_init_one(asg, esph, sizeof(*esph));

        aead_givcrypt_set_callback(req, 0, esp_output_done, skb);
        aead_givcrypt_set_crypt(req, sg, sg, clen, iv);
        aead_givcrypt_set_assoc(req, asg, sizeof(*esph));
        aead_givcrypt_set_giv(req, esph->enc_data,
                              XFRM_SKB_CB(skb)->seq.output);

        ESP_SKB_CB(skb)->tmp = tmp;
        err = crypto_aead_givencrypt(req);
        if (err == -EINPROGRESS)
                goto error;

        if (err == -EBUSY)
                err = NET_XMIT_DROP;

        kfree(tmp);

error:
        return err;
}

static int esp_input_done2(struct sk_buff *skb, int err)
{
        struct iphdr *iph;
        struct xfrm_state *x = xfrm_input_state(skb);
        struct esp_data *esp = x->data;
        struct crypto_aead *aead = esp->aead;
        int alen = crypto_aead_authsize(aead);
        int hlen = sizeof(struct ip_esp_hdr) + crypto_aead_ivsize(aead);
        int elen = skb->len - hlen;
        int ihl;
        u8 nexthdr[2];
        int padlen;

        kfree(ESP_SKB_CB(skb)->tmp);

        if (unlikely(err))
                goto out;

        if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
                BUG();

        err = -EINVAL;
        padlen = nexthdr[0];
        if (padlen + 2 + alen >= elen)
                goto out;

        /* ... check padding bits here. Silly. :-) */

        iph = ip_hdr(skb);
        ihl = iph->ihl * 4;

        if (x->encap) {
                struct xfrm_encap_tmpl *encap = x->encap;
                struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);

                /*
                 * 1) if the NAT-T peer's IP or port changed then
                 *    advertize the change to the keying daemon.
                 *    This is an inbound SA, so just compare
                 *    SRC ports.
                 */
                if (iph->saddr != x->props.saddr.a4 ||
                    uh->source != encap->encap_sport) {
                        xfrm_address_t ipaddr;

                        ipaddr.a4 = iph->saddr;
                        km_new_mapping(x, &ipaddr, uh->source);

                        /* XXX: perhaps add an extra
                         * policy check here, to see
                         * if we should allow or
                         * reject a packet from a
                         * different source
                         * address/port.
                         */
                }

                /*
                 * 2) ignore UDP/TCP checksums in case
                 *    of NAT-T in Transport Mode, or
                 *    perform other post-processing fixes
                 *    as per draft-ietf-ipsec-udp-encaps-06,
                 *    section 3.1.2
                 */
                if (x->props.mode == XFRM_MODE_TRANSPORT)
                        skb->ip_summed = CHECKSUM_UNNECESSARY;
        }

        pskb_trim(skb, skb->len - alen - padlen - 2);
        __skb_pull(skb, hlen);
        skb_set_transport_header(skb, -ihl);

        err = nexthdr[1];

        /* RFC4303: Drop dummy packets without any error */
        if (err == IPPROTO_NONE)
                err = -EINVAL;

out:
        return err;
}

static void esp_input_done(struct crypto_async_request *base, int err)
{
        struct sk_buff *skb = base->data;

        xfrm_input_resume(skb, esp_input_done2(skb, err));
}

/*
 * Note: detecting truncated vs. non-truncated authentication data is very
 * expensive, so we only support truncated data, which is the recommended
 * and common case.
 */
static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
{
        struct ip_esp_hdr *esph;
        struct esp_data *esp = x->data;
        struct crypto_aead *aead = esp->aead;
        struct aead_request *req;
        struct sk_buff *trailer;
        int elen = skb->len - sizeof(*esph) - crypto_aead_ivsize(aead);
        int nfrags;
        void *tmp;
        u8 *iv;
        struct scatterlist *sg;
        struct scatterlist *asg;
        int err = -EINVAL;

        if (!pskb_may_pull(skb, sizeof(*esph) + crypto_aead_ivsize(aead)))
                goto out;

        if (elen <= 0)
                goto out;

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

        err = -ENOMEM;
        tmp = esp_alloc_tmp(aead, nfrags + 1);
        if (!tmp)
                goto out;

        ESP_SKB_CB(skb)->tmp = tmp;
        iv = esp_tmp_iv(aead, tmp);
        req = esp_tmp_req(aead, iv);
        asg = esp_req_sg(aead, req);
        sg = asg + 1;

        skb->ip_summed = CHECKSUM_NONE;

        esph = (struct ip_esp_hdr *)skb->data;

        /* Get ivec. This can be wrong, check against another impls. */
        iv = esph->enc_data;

        sg_init_table(sg, nfrags);
        skb_to_sgvec(skb, sg, sizeof(*esph) + crypto_aead_ivsize(aead), elen);
        sg_init_one(asg, esph, sizeof(*esph));

        aead_request_set_callback(req, 0, esp_input_done, skb);
        aead_request_set_crypt(req, sg, sg, elen, iv);
        aead_request_set_assoc(req, asg, sizeof(*esph));

        err = crypto_aead_decrypt(req);
        if (err == -EINPROGRESS)
                goto out;

        err = esp_input_done2(skb, err);

out:
        return err;
}

static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
{
        struct esp_data *esp = x->data;
        u32 blksize = ALIGN(crypto_aead_blocksize(esp->aead), 4);
        u32 align = max_t(u32, blksize, esp->padlen);
        u32 rem;

        mtu -= x->props.header_len + crypto_aead_authsize(esp->aead);
        rem = mtu & (align - 1);
        mtu &= ~(align - 1);

        switch (x->props.mode) {
        case XFRM_MODE_TUNNEL:
                break;
        default:
        case XFRM_MODE_TRANSPORT:
                /* The worst case */
                mtu -= blksize - 4;
                mtu += min_t(u32, blksize - 4, rem);
                break;
        case XFRM_MODE_BEET:
                /* The worst case. */
                mtu += min_t(u32, IPV4_BEET_PHMAXLEN, rem);
                break;
        }

        return mtu - 2;
}

static void esp4_err(struct sk_buff *skb, u32 info)
{
        struct net *net = dev_net(skb->dev);
        struct iphdr *iph = (struct iphdr *)skb->data;
        struct ip_esp_hdr *esph = (struct ip_esp_hdr *)(skb->data+(iph->ihl<<2));
        struct xfrm_state *x;

        if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
            icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
                return;

        x = xfrm_state_lookup(net, (xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
        if (!x)
                return;
        NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
                 ntohl(esph->spi), ntohl(iph->daddr));
        xfrm_state_put(x);
}

static void esp_destroy(struct xfrm_state *x)
{
        struct esp_data *esp = x->data;

        if (!esp)
                return;

        crypto_free_aead(esp->aead);
        kfree(esp);
}

static int esp_init_aead(struct xfrm_state *x)
{
        struct esp_data *esp = x->data;
        struct crypto_aead *aead;
        int err;

        aead = crypto_alloc_aead(x->aead->alg_name, 0, 0);
        err = PTR_ERR(aead);
        if (IS_ERR(aead))
                goto error;

        esp->aead = aead;

        err = crypto_aead_setkey(aead, x->aead->alg_key,
                                 (x->aead->alg_key_len + 7) / 8);
        if (err)
                goto error;

        err = crypto_aead_setauthsize(aead, x->aead->alg_icv_len / 8);
        if (err)
                goto error;

error:
        return err;
}

static int esp_init_authenc(struct xfrm_state *x)
{
        struct esp_data *esp = x->data;
        struct crypto_aead *aead;
        struct crypto_authenc_key_param *param;
        struct rtattr *rta;
        char *key;
        char *p;
        char authenc_name[CRYPTO_MAX_ALG_NAME];
        unsigned int keylen;
        int err;

        err = -EINVAL;
        if (x->ealg == NULL)
                goto error;

        err = -ENAMETOOLONG;
        if (snprintf(authenc_name, CRYPTO_MAX_ALG_NAME, "authenc(%s,%s)",
                     x->aalg ? x->aalg->alg_name : "digest_null",
                     x->ealg->alg_name) >= CRYPTO_MAX_ALG_NAME)
                goto error;

        aead = crypto_alloc_aead(authenc_name, 0, 0);
        err = PTR_ERR(aead);
        if (IS_ERR(aead))
                goto error;

        esp->aead = aead;

        keylen = (x->aalg ? (x->aalg->alg_key_len + 7) / 8 : 0) +
                 (x->ealg->alg_key_len + 7) / 8 + RTA_SPACE(sizeof(*param));
        err = -ENOMEM;
        key = kmalloc(keylen, GFP_KERNEL);
        if (!key)
                goto error;

        p = key;
        rta = (void *)p;
        rta->rta_type = CRYPTO_AUTHENC_KEYA_PARAM;
        rta->rta_len = RTA_LENGTH(sizeof(*param));
        param = RTA_DATA(rta);
        p += RTA_SPACE(sizeof(*param));

        if (x->aalg) {
                struct xfrm_algo_desc *aalg_desc;

                memcpy(p, x->aalg->alg_key, (x->aalg->alg_key_len + 7) / 8);
                p += (x->aalg->alg_key_len + 7) / 8;

                aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
                BUG_ON(!aalg_desc);

                err = -EINVAL;
                if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
                    crypto_aead_authsize(aead)) {
                        NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
                                 x->aalg->alg_name,
                                 crypto_aead_authsize(aead),
                                 aalg_desc->uinfo.auth.icv_fullbits/8);
                        goto free_key;
                }

                err = crypto_aead_setauthsize(
                        aead, aalg_desc->uinfo.auth.icv_truncbits / 8);
                if (err)
                        goto free_key;
        }

        param->enckeylen = cpu_to_be32((x->ealg->alg_key_len + 7) / 8);
        memcpy(p, x->ealg->alg_key, (x->ealg->alg_key_len + 7) / 8);

        err = crypto_aead_setkey(aead, key, keylen);

free_key:
        kfree(key);

error:
        return err;
}

static int esp_init_state(struct xfrm_state *x)
{
        struct esp_data *esp;
        struct crypto_aead *aead;
        u32 align;
        int err;

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

        x->data = esp;

        if (x->aead)
                err = esp_init_aead(x);
        else
                err = esp_init_authenc(x);

        if (err)
                goto error;

        aead = esp->aead;

        esp->padlen = 0;

        x->props.header_len = sizeof(struct ip_esp_hdr) +
                              crypto_aead_ivsize(aead);
        if (x->props.mode == XFRM_MODE_TUNNEL)
                x->props.header_len += sizeof(struct iphdr);
        else if (x->props.mode == XFRM_MODE_BEET && x->sel.family != AF_INET6)
                x->props.header_len += IPV4_BEET_PHMAXLEN;
        if (x->encap) {
                struct xfrm_encap_tmpl *encap = x->encap;

                switch (encap->encap_type) {
                default:
                        goto error;
                case UDP_ENCAP_ESPINUDP:
                        x->props.header_len += sizeof(struct udphdr);
                        break;
                case UDP_ENCAP_ESPINUDP_NON_IKE:
                        x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
                        break;
                }
        }

        align = ALIGN(crypto_aead_blocksize(aead), 4);
        if (esp->padlen)
                align = max_t(u32, align, esp->padlen);
        x->props.trailer_len = align + 1 + crypto_aead_authsize(esp->aead);

error:
        return err;
}

static const struct xfrm_type esp_type =
{
        .description    = "ESP4",
        .owner          = THIS_MODULE,
        .proto          = IPPROTO_ESP,
        .flags          = XFRM_TYPE_REPLAY_PROT,
        .init_state     = esp_init_state,
        .destructor     = esp_destroy,
        .get_mtu        = esp4_get_mtu,
        .input          = esp_input,
        .output         = esp_output
};

static const struct net_protocol esp4_protocol = {
        .handler        =       xfrm4_rcv,
        .err_handler    =       esp4_err,
        .no_policy      =       1,
        .netns_ok       =       1,
};

static int __init esp4_init(void)
{
        if (xfrm_register_type(&esp_type, AF_INET) < 0) {
                printk(KERN_INFO "ip esp init: can't add xfrm type\n");
                return -EAGAIN;
        }
        if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
                printk(KERN_INFO "ip esp init: can't add protocol\n");
                xfrm_unregister_type(&esp_type, AF_INET);
                return -EAGAIN;
        }
        return 0;
}

static void __exit esp4_fini(void)
{
        if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
                printk(KERN_INFO "ip esp close: can't remove protocol\n");
        if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
                printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
}

module_init(esp4_init);
module_exit(esp4_fini);
MODULE_LICENSE("GPL");
MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_ESP);