/*
   * 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/esp.c
   */

  #include <linux/err.h>

  #include <linux/module.h>
  #include <net/ip.h>
  #include <net/xfrm.h>
  #include <net/esp.h>
  #include <asm/scatterlist.h>
  #include <linux/crypto.h>

  #include <linux/kernel.h>

  #include <linux/pfkeyv2.h>
  #include <linux/random.h>
  #include <net/icmp.h>
  #include <net/ipv6.h>

  #include <net/protocol.h>

  #include <linux/icmpv6.h>
  
  static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
  {
  	int err;

  	struct ipv6hdr *top_iph;
  	struct ipv6_esp_hdr *esph;

  	struct crypto_blkcipher *tfm;
  	struct blkcipher_desc desc;

  	struct sk_buff *trailer;
  	int blksize;
  	int clen;
  	int alen;
  	int nfrags;

  	u8 *tail;

  	struct esp_data *esp = x->data;
  	int hdr_len = (skb_transport_offset(skb) +
  		       sizeof(*esph) + esp->conf.ivlen);

  
  	/* Strip IP+ESP header. */
  	__skb_pull(skb, hdr_len);
  
  	/* Now skb is pure payload to encrypt */
  	err = -ENOMEM;
  
  	/* Round to block size */
  	clen = skb->len;
  
  	alen = esp->auth.icv_trunc_len;
  	tfm = esp->conf.tfm;

  	desc.tfm = tfm;
  	desc.flags = 0;
  	blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);

  	clen = ALIGN(clen + 2, blksize);

  	if (esp->conf.padlen)

  		clen = ALIGN(clen, esp->conf.padlen);

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

  	pskb_put(skb, trailer, clen - skb->len);
  
  	top_iph = (struct ipv6hdr *)__skb_push(skb, hdr_len);

  	esph = (struct ipv6_esp_hdr *)skb_transport_header(skb);

  	top_iph->payload_len = htons(skb->len + alen - sizeof(*top_iph));

  	*(skb_tail_pointer(trailer) - 1) = *skb_network_header(skb);

  	*skb_network_header(skb) = IPPROTO_ESP;

  
  	esph->spi = x->id.spi;
  	esph->seq_no = htonl(++x->replay.oseq);

  	xfrm_aevent_doreplay(x);

  	if (esp->conf.ivlen) {
  		if (unlikely(!esp->conf.ivinitted)) {
  			get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
  			esp->conf.ivinitted = 1;
  		}

  		crypto_blkcipher_set_iv(tfm, esp->conf.ivec, esp->conf.ivlen);

  	}

  
  	do {
  		struct scatterlist *sg = &esp->sgbuf[0];
  
  		if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
  			sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
  			if (!sg)
  				goto error;
  		}
  		skb_to_sgvec(skb, sg, esph->enc_data+esp->conf.ivlen-skb->data, clen);

  		err = crypto_blkcipher_encrypt(&desc, sg, sg, clen);

  		if (unlikely(sg != &esp->sgbuf[0]))
  			kfree(sg);
  	} while (0);

  	if (unlikely(err))
  		goto error;

  	if (esp->conf.ivlen) {

  		memcpy(esph->enc_data, esp->conf.ivec, esp->conf.ivlen);
  		crypto_blkcipher_get_iv(tfm, esp->conf.ivec, esp->conf.ivlen);

  	}
  
  	if (esp->auth.icv_full_len) {

  		err = esp_mac_digest(esp, skb, (u8 *)esph - skb->data,
  				     sizeof(*esph) + esp->conf.ivlen + clen);
  		memcpy(pskb_put(skb, trailer, alen), esp->auth.work_icv, alen);

  	}

  error:
  	return err;
  }

  static int esp6_input(struct xfrm_state *x, struct sk_buff *skb)

  {
  	struct ipv6hdr *iph;
  	struct ipv6_esp_hdr *esph;
  	struct esp_data *esp = x->data;

  	struct crypto_blkcipher *tfm = esp->conf.tfm;
  	struct blkcipher_desc desc = { .tfm = tfm };

  	struct sk_buff *trailer;

  	int blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);

  	int alen = esp->auth.icv_trunc_len;
  	int elen = skb->len - sizeof(struct ipv6_esp_hdr) - esp->conf.ivlen - alen;

  	int hdr_len = skb_network_header_len(skb);

  	int nfrags;

  	int ret = 0;
  
  	if (!pskb_may_pull(skb, sizeof(struct ipv6_esp_hdr))) {
  		ret = -EINVAL;

  		goto out;

  	}
  
  	if (elen <= 0 || (elen & (blksize-1))) {
  		ret = -EINVAL;

  		goto out;

  	}

  
  	/* If integrity check is required, do this. */

  	if (esp->auth.icv_full_len) {

  		u8 sum[alen];

  		ret = esp_mac_digest(esp, skb, 0, skb->len - alen);
  		if (ret)
  			goto out;

  		if (skb_copy_bits(skb, skb->len - alen, sum, alen))

  			BUG();

  		if (unlikely(memcmp(esp->auth.work_icv, sum, alen))) {

  			x->stats.integrity_failed++;
  			ret = -EINVAL;
  			goto out;
  		}
  	}
  
  	if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	skb->ip_summed = CHECKSUM_NONE;
  
  	esph = (struct ipv6_esp_hdr*)skb->data;

  	iph = ipv6_hdr(skb);

  
  	/* Get ivec. This can be wrong, check against another impls. */
  	if (esp->conf.ivlen)

  		crypto_blkcipher_set_iv(tfm, esph->enc_data, esp->conf.ivlen);

  	{

  		u8 nexthdr[2];
  		struct scatterlist *sg = &esp->sgbuf[0];
  		u8 padlen;
  
  		if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
  			sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
  			if (!sg) {
  				ret = -ENOMEM;
  				goto out;
  			}
  		}
  		skb_to_sgvec(skb, sg, sizeof(struct ipv6_esp_hdr) + esp->conf.ivlen, elen);

  		ret = crypto_blkcipher_decrypt(&desc, sg, sg, elen);

  		if (unlikely(sg != &esp->sgbuf[0]))
  			kfree(sg);

  		if (unlikely(ret))
  			goto out;

  
  		if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
  			BUG();
  
  		padlen = nexthdr[0];
  		if (padlen+2 >= elen) {

  			LIMIT_NETDEBUG(KERN_WARNING "ipsec esp packet is garbage padlen=%d, elen=%d
  ", padlen+2, elen);

  			ret = -EINVAL;
  			goto out;
  		}

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

  
  		pskb_trim(skb, skb->len - alen - padlen - 2);

  		ret = nexthdr[1];
  	}

  	__skb_pull(skb, sizeof(*esph) + esp->conf.ivlen);
  	skb_set_transport_header(skb, -hdr_len);

  out:

  	return ret;
  }

  static u32 esp6_get_mtu(struct xfrm_state *x, int mtu)

  {
  	struct esp_data *esp = x->data;

  	u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);

  	u32 align = max_t(u32, blksize, esp->conf.padlen);
  	u32 rem;

  	mtu -= x->props.header_len + esp->auth.icv_trunc_len;
  	rem = mtu & (align - 1);
  	mtu &= ~(align - 1);
  
  	if (x->props.mode != XFRM_MODE_TUNNEL) {

  		u32 padsize = ((blksize - 1) & 7) + 1;

  		mtu -= blksize - padsize;
  		mtu += min_t(u32, blksize - padsize, rem);

  	}

  	return mtu - 2;

  }
  
  static void esp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,

  		     int type, int code, int offset, __be32 info)

  {
  	struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
  	struct ipv6_esp_hdr *esph = (struct ipv6_esp_hdr*)(skb->data+offset);
  	struct xfrm_state *x;

  	if (type != ICMPV6_DEST_UNREACH &&

  	    type != ICMPV6_PKT_TOOBIG)
  		return;
  
  	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET6);
  	if (!x)
  		return;

  	printk(KERN_DEBUG "pmtu discovery on SA ESP/%08x/" NIP6_FMT "
  ",

  			ntohl(esph->spi), NIP6(iph->daddr));
  	xfrm_state_put(x);
  }
  
  static void esp6_destroy(struct xfrm_state *x)
  {
  	struct esp_data *esp = x->data;
  
  	if (!esp)
  		return;

  	crypto_free_blkcipher(esp->conf.tfm);

  	esp->conf.tfm = NULL;
  	kfree(esp->conf.ivec);
  	esp->conf.ivec = NULL;

  	crypto_free_hash(esp->auth.tfm);

  	esp->auth.tfm = NULL;
  	kfree(esp->auth.work_icv);
  	esp->auth.work_icv = NULL;

  	kfree(esp);
  }

  static int esp6_init_state(struct xfrm_state *x)

  {
  	struct esp_data *esp = NULL;

  	struct crypto_blkcipher *tfm;

  
  	/* null auth and encryption can have zero length keys */
  	if (x->aalg) {
  		if (x->aalg->alg_key_len > 512)
  			goto error;
  	}
  	if (x->ealg == NULL)
  		goto error;
  
  	if (x->encap)
  		goto error;

  	esp = kzalloc(sizeof(*esp), GFP_KERNEL);

  	if (esp == NULL)
  		return -ENOMEM;

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

  		struct crypto_hash *hash;

  
  		esp->auth.key = x->aalg->alg_key;
  		esp->auth.key_len = (x->aalg->alg_key_len+7)/8;

  		hash = crypto_alloc_hash(x->aalg->alg_name, 0,
  					 CRYPTO_ALG_ASYNC);
  		if (IS_ERR(hash))
  			goto error;
  
  		esp->auth.tfm = hash;
  		if (crypto_hash_setkey(hash, esp->auth.key, esp->auth.key_len))

  			goto error;

  		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(hash)) {
  			NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu
  ",
  				 x->aalg->alg_name,
  				 crypto_hash_digestsize(hash),
  				 aalg_desc->uinfo.auth.icv_fullbits/8);
  			goto error;

  		}

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

  		esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
  		if (!esp->auth.work_icv)
  			goto error;
  	}
  	esp->conf.key = x->ealg->alg_key;
  	esp->conf.key_len = (x->ealg->alg_key_len+7)/8;

  	tfm = crypto_alloc_blkcipher(x->ealg->alg_name, 0, CRYPTO_ALG_ASYNC);
  	if (IS_ERR(tfm))

  		goto error;

  	esp->conf.tfm = tfm;
  	esp->conf.ivlen = crypto_blkcipher_ivsize(tfm);

  	esp->conf.padlen = 0;
  	if (esp->conf.ivlen) {
  		esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
  		if (unlikely(esp->conf.ivec == NULL))
  			goto error;

  		esp->conf.ivinitted = 0;

  	}

  	if (crypto_blkcipher_setkey(tfm, esp->conf.key, esp->conf.key_len))

  		goto error;
  	x->props.header_len = sizeof(struct ipv6_esp_hdr) + esp->conf.ivlen;

  	if (x->props.mode == XFRM_MODE_TUNNEL)

  		x->props.header_len += sizeof(struct ipv6hdr);
  	x->data = esp;
  	return 0;
  
  error:
  	x->data = esp;
  	esp6_destroy(x);
  	x->data = NULL;
  	return -EINVAL;
  }
  
  static struct xfrm_type esp6_type =
  {
  	.description	= "ESP6",
  	.owner	     	= THIS_MODULE,
  	.proto	     	= IPPROTO_ESP,
  	.init_state	= esp6_init_state,
  	.destructor	= esp6_destroy,

  	.get_mtu	= esp6_get_mtu,

  	.input		= esp6_input,

  	.output		= esp6_output,
  	.hdr_offset	= xfrm6_find_1stfragopt,

  };
  
  static struct inet6_protocol esp6_protocol = {
  	.handler 	=	xfrm6_rcv,
  	.err_handler	=	esp6_err,
  	.flags		=	INET6_PROTO_NOPOLICY,
  };
  
  static int __init esp6_init(void)
  {
  	if (xfrm_register_type(&esp6_type, AF_INET6) < 0) {
  		printk(KERN_INFO "ipv6 esp init: can't add xfrm type
  ");
  		return -EAGAIN;
  	}
  	if (inet6_add_protocol(&esp6_protocol, IPPROTO_ESP) < 0) {
  		printk(KERN_INFO "ipv6 esp init: can't add protocol
  ");
  		xfrm_unregister_type(&esp6_type, AF_INET6);
  		return -EAGAIN;
  	}
  
  	return 0;
  }
  
  static void __exit esp6_fini(void)
  {
  	if (inet6_del_protocol(&esp6_protocol, IPPROTO_ESP) < 0)
  		printk(KERN_INFO "ipv6 esp close: can't remove protocol
  ");
  	if (xfrm_unregister_type(&esp6_type, AF_INET6) < 0)
  		printk(KERN_INFO "ipv6 esp close: can't remove xfrm type
  ");
  }
  
  module_init(esp6_init);
  module_exit(esp6_fini);
  
  MODULE_LICENSE("GPL");

  MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_ESP);