net/ipv4/ah4.c - maze/linux - Git at Google

 #define pr_fmt(fmt) "IPsec: " fmt

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

 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 u8 *ah_tmp_auth(void *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));
 }

 /* Clear mutable options and find final destination to substitute
  * into IP header for icv calculation. Options are already checked
  * for validity, so paranoia is not required. */

 static int ip_clear_mutable_options(const struct iphdr *iph, __be32 *daddr)
 {
 	unsigned char *optptr = (unsigned char *)(iph+1);
 	int  l = iph->ihl*4 - sizeof(struct iphdr);
 	int  optlen;

 	while (l > 0) {
 		switch (*optptr) {
 		case IPOPT_END:
 			return 0;
 		case IPOPT_NOOP:
 			l--;
 			optptr++;
 			continue;
 		}
 		optlen = optptr[1];
 		if (optlen<2 || optlen>l)
 			return -EINVAL;
 		switch (*optptr) {
 		case IPOPT_SEC:
 		case 0x85:	/* Some "Extended Security" crap. */
 		case IPOPT_CIPSO:
 		case IPOPT_RA:
 		case 0x80|21:	/* RFC1770 */
 			break;
 		case IPOPT_LSRR:
 		case IPOPT_SSRR:
 			if (optlen < 6)
 				return -EINVAL;
 			memcpy(daddr, optptr+optlen-4, 4);
 			/* Fall through */
 		default:
 			memset(optptr, 0, optlen);
 		}
 		l -= optlen;
 		optptr += optlen;
 	}
 	return 0;
 }

 static void ah_output_done(struct crypto_async_request *base, int err)
 {
 	u8 *icv;
 	struct iphdr *iph;
 	struct sk_buff *skb = base->data;
 	struct xfrm_state *x = skb_dst(skb)->xfrm;
 	struct ah_data *ahp = x->data;
 	struct iphdr *top_iph = ip_hdr(skb);
 	struct ip_auth_hdr *ah = ip_auth_hdr(skb);
 	int ihl = ip_hdrlen(skb);

 	iph = AH_SKB_CB(skb)->tmp;
 	icv = ah_tmp_icv(ahp->ahash, iph, ihl);
 	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);

 	top_iph->tos = iph->tos;
 	top_iph->ttl = iph->ttl;
 	top_iph->frag_off = iph->frag_off;
 	if (top_iph->ihl != 5) {
 		top_iph->daddr = iph->daddr;
 		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 	}

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

 static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
 {
 	int err;
 	int nfrags;
 	int ihl;
 	u8 *icv;
 	struct sk_buff *trailer;
 	struct crypto_ahash *ahash;
 	struct ahash_request *req;
 	struct scatterlist *sg;
 	struct iphdr *iph, *top_iph;
 	struct ip_auth_hdr *ah;
 	struct ah_data *ahp;

 	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));
 	ah = ip_auth_hdr(skb);
 	ihl = ip_hdrlen(skb);

 	err = -ENOMEM;
 	iph = ah_alloc_tmp(ahash, nfrags, ihl);
 	if (!iph)
 		goto out;

 	icv = ah_tmp_icv(ahash, iph, ihl);
 	req = ah_tmp_req(ahash, icv);
 	sg = ah_req_sg(ahash, req);

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

 	top_iph = ip_hdr(skb);

 	iph->tos = top_iph->tos;
 	iph->ttl = top_iph->ttl;
 	iph->frag_off = top_iph->frag_off;

 	if (top_iph->ihl != 5) {
 		iph->daddr = top_iph->daddr;
 		memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 		err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
 		if (err)
 			goto out_free;
 	}

 	ah->nexthdr = *skb_mac_header(skb);
 	*skb_mac_header(skb) = IPPROTO_AH;

 	top_iph->tos = 0;
 	top_iph->tot_len = htons(skb->len);
 	top_iph->frag_off = 0;
 	top_iph->ttl = 0;
 	top_iph->check = 0;

 	if (x->props.flags & XFRM_STATE_ALIGN4)
 		ah->hdrlen  = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
 	else
 		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, ah_output_done, skb);

 	AH_SKB_CB(skb)->tmp = iph;

 	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);

 	top_iph->tos = iph->tos;
 	top_iph->ttl = iph->ttl;
 	top_iph->frag_off = iph->frag_off;
 	if (top_iph->ihl != 5) {
 		top_iph->daddr = iph->daddr;
 		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
 	}

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

 static void ah_input_done(struct crypto_async_request *base, int err)
 {
 	u8 *auth_data;
 	u8 *icv;
 	struct iphdr *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 ihl = ip_hdrlen(skb);
 	int ah_hlen = (ah->hdrlen + 2) << 2;

 	work_iph = AH_SKB_CB(skb)->tmp;
 	auth_data = ah_tmp_auth(work_iph, ihl);
 	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, ihl);
 	__skb_pull(skb, ah_hlen + ihl);
 	skb_set_transport_header(skb, -ihl);
 out:
 	kfree(AH_SKB_CB(skb)->tmp);
 	xfrm_input_resume(skb, err);
 }

 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 {
 	int ah_hlen;
 	int ihl;
 	int nexthdr;
 	int nfrags;
 	u8 *auth_data;
 	u8 *icv;
 	struct sk_buff *trailer;
 	struct crypto_ahash *ahash;
 	struct ahash_request *req;
 	struct scatterlist *sg;
 	struct iphdr *iph, *work_iph;
 	struct ip_auth_hdr *ah;
 	struct ah_data *ahp;
 	int err = -ENOMEM;

 	if (!pskb_may_pull(skb, sizeof(*ah)))
 		goto out;

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

 	nexthdr = ah->nexthdr;
 	ah_hlen = (ah->hdrlen + 2) << 2;

 	if (x->props.flags & XFRM_STATE_ALIGN4) {
 		if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
 		    ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
 			goto out;
 	} else {
 		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;

 	/* 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;


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

 	ah = (struct ip_auth_hdr *)skb->data;
 	iph = ip_hdr(skb);
 	ihl = ip_hdrlen(skb);

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

 	auth_data = ah_tmp_auth(work_iph, ihl);
 	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, iph, ihl);
 	memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 	memset(ah->auth_data, 0, ahp->icv_trunc_len);

 	iph->ttl = 0;
 	iph->tos = 0;
 	iph->frag_off = 0;
 	iph->check = 0;
 	if (ihl > sizeof(*iph)) {
 		__be32 dummy;
 		err = ip_clear_mutable_options(iph, &dummy);
 		if (err)
 			goto out_free;
 	}

 	skb_push(skb, ihl);

 	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, ah_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, ihl);
 	__skb_pull(skb, ah_hlen + ihl);
 	skb_set_transport_header(skb, -ihl);

 	err = nexthdr;

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

 static void ah4_err(struct sk_buff *skb, u32 info)
 {
 	struct net *net = dev_net(skb->dev);
 	const struct iphdr *iph = (const struct iphdr *)skb->data;
 	struct ip_auth_hdr *ah = (struct ip_auth_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, skb->mark, (const xfrm_address_t *)&iph->daddr,
 			      ah->spi, IPPROTO_AH, AF_INET);
 	if (!x)
 		return;
 	pr_debug("pmtu discovery on SA AH/%08x/%08x\n",
 		 ntohl(ah->spi), ntohl(iph->daddr));
 	xfrm_state_put(x);
 }

 static int ah_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)
 		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_ahash().
 	 */
 	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("%s: %s digestsize %u != %hu\n",
 			__func__, 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);

 	if (x->props.flags & XFRM_STATE_ALIGN4)
 		x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
 						  ahp->icv_trunc_len);
 	else
 		x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 						  ahp->icv_trunc_len);
 	if (x->props.mode == XFRM_MODE_TUNNEL)
 		x->props.header_len += sizeof(struct iphdr);
 	x->data = ahp;

 	return 0;

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

 static void ah_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 ah_type =
 {
 	.description	= "AH4",
 	.owner		= THIS_MODULE,
 	.proto	     	= IPPROTO_AH,
 	.flags		= XFRM_TYPE_REPLAY_PROT,
 	.init_state	= ah_init_state,
 	.destructor	= ah_destroy,
 	.input		= ah_input,
 	.output		= ah_output
 };

 static const struct net_protocol ah4_protocol = {
 	.handler	=	xfrm4_rcv,
 	.err_handler	=	ah4_err,
 	.no_policy	=	1,
 	.netns_ok	=	1,
 };

 static int __init ah4_init(void)
 {
 	if (xfrm_register_type(&ah_type, AF_INET) < 0) {
 		pr_info("%s: can't add xfrm type\n", __func__);
 		return -EAGAIN;
 	}
 	if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
 		pr_info("%s: can't add protocol\n", __func__);
 		xfrm_unregister_type(&ah_type, AF_INET);
 		return -EAGAIN;
 	}
 	return 0;
 }

 static void __exit ah4_fini(void)
 {
 	if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
 		pr_info("%s: can't remove protocol\n", __func__);
 	if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
 		pr_info("%s: can't remove xfrm type\n", __func__);
 }

 module_init(ah4_init);
 module_exit(ah4_fini);
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);
	#define pr_fmt(fmt) "IPsec: " fmt

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

	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 u8 ah_tmp_auth(void 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));
	}

	/* Clear mutable options and find final destination to substitute
	* into IP header for icv calculation. Options are already checked
	* for validity, so paranoia is not required. */

	static int ip_clear_mutable_options(const struct iphdr iph, __be32 daddr)
	{
	unsigned char optptr = (unsigned char )(iph+1);
	int l = iph->ihl*4 - sizeof(struct iphdr);
	int optlen;

	while (l > 0) {
	switch (*optptr) {
	case IPOPT_END:
	return 0;
	case IPOPT_NOOP:
	l--;
	optptr++;
	continue;
	}
	optlen = optptr[1];
	if (optlen<2 \|\| optlen>l)
	return -EINVAL;
	switch (*optptr) {
	case IPOPT_SEC:
	case 0x85: /* Some "Extended Security" crap. */
	case IPOPT_CIPSO:
	case IPOPT_RA:
	case 0x80\|21: /* RFC1770 */
	break;
	case IPOPT_LSRR:
	case IPOPT_SSRR:
	if (optlen < 6)
	return -EINVAL;
	memcpy(daddr, optptr+optlen-4, 4);
	/* Fall through */
	default:
	memset(optptr, 0, optlen);
	}
	l -= optlen;
	optptr += optlen;
	}
	return 0;
	}

	static void ah_output_done(struct crypto_async_request *base, int err)
	{
	u8 *icv;
	struct iphdr *iph;
	struct sk_buff *skb = base->data;
	struct xfrm_state *x = skb_dst(skb)->xfrm;
	struct ah_data *ahp = x->data;
	struct iphdr *top_iph = ip_hdr(skb);
	struct ip_auth_hdr *ah = ip_auth_hdr(skb);
	int ihl = ip_hdrlen(skb);

	iph = AH_SKB_CB(skb)->tmp;
	icv = ah_tmp_icv(ahp->ahash, iph, ihl);
	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);

	top_iph->tos = iph->tos;
	top_iph->ttl = iph->ttl;
	top_iph->frag_off = iph->frag_off;
	if (top_iph->ihl != 5) {
	top_iph->daddr = iph->daddr;
	memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
	}

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

	static int ah_output(struct xfrm_state x, struct sk_buff skb)
	{
	int err;
	int nfrags;
	int ihl;
	u8 *icv;
	struct sk_buff *trailer;
	struct crypto_ahash *ahash;
	struct ahash_request *req;
	struct scatterlist *sg;
	struct iphdr iph, top_iph;
	struct ip_auth_hdr *ah;
	struct ah_data *ahp;

	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));
	ah = ip_auth_hdr(skb);
	ihl = ip_hdrlen(skb);

	err = -ENOMEM;
	iph = ah_alloc_tmp(ahash, nfrags, ihl);
	if (!iph)
	goto out;

	icv = ah_tmp_icv(ahash, iph, ihl);
	req = ah_tmp_req(ahash, icv);
	sg = ah_req_sg(ahash, req);

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

	top_iph = ip_hdr(skb);

	iph->tos = top_iph->tos;
	iph->ttl = top_iph->ttl;
	iph->frag_off = top_iph->frag_off;

	if (top_iph->ihl != 5) {
	iph->daddr = top_iph->daddr;
	memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
	err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
	if (err)
	goto out_free;
	}

	ah->nexthdr = *skb_mac_header(skb);
	*skb_mac_header(skb) = IPPROTO_AH;

	top_iph->tos = 0;
	top_iph->tot_len = htons(skb->len);
	top_iph->frag_off = 0;
	top_iph->ttl = 0;
	top_iph->check = 0;

	if (x->props.flags & XFRM_STATE_ALIGN4)
	ah->hdrlen = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
	else
	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, ah_output_done, skb);

	AH_SKB_CB(skb)->tmp = iph;

	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);

	top_iph->tos = iph->tos;
	top_iph->ttl = iph->ttl;
	top_iph->frag_off = iph->frag_off;
	if (top_iph->ihl != 5) {
	top_iph->daddr = iph->daddr;
	memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
	}

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

	static void ah_input_done(struct crypto_async_request *base, int err)
	{
	u8 *auth_data;
	u8 *icv;
	struct iphdr *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 ihl = ip_hdrlen(skb);
	int ah_hlen = (ah->hdrlen + 2) << 2;

	work_iph = AH_SKB_CB(skb)->tmp;
	auth_data = ah_tmp_auth(work_iph, ihl);
	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, ihl);
	__skb_pull(skb, ah_hlen + ihl);
	skb_set_transport_header(skb, -ihl);
	out:
	kfree(AH_SKB_CB(skb)->tmp);
	xfrm_input_resume(skb, err);
	}

	static int ah_input(struct xfrm_state x, struct sk_buff skb)
	{
	int ah_hlen;
	int ihl;
	int nexthdr;
	int nfrags;
	u8 *auth_data;
	u8 *icv;
	struct sk_buff *trailer;
	struct crypto_ahash *ahash;
	struct ahash_request *req;
	struct scatterlist *sg;
	struct iphdr iph, work_iph;
	struct ip_auth_hdr *ah;
	struct ah_data *ahp;
	int err = -ENOMEM;

	if (!pskb_may_pull(skb, sizeof(*ah)))
	goto out;

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

	nexthdr = ah->nexthdr;
	ah_hlen = (ah->hdrlen + 2) << 2;

	if (x->props.flags & XFRM_STATE_ALIGN4) {
	if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
	ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
	goto out;
	} else {
	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;

	/* 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;


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

	ah = (struct ip_auth_hdr *)skb->data;
	iph = ip_hdr(skb);
	ihl = ip_hdrlen(skb);

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

	auth_data = ah_tmp_auth(work_iph, ihl);
	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, iph, ihl);
	memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
	memset(ah->auth_data, 0, ahp->icv_trunc_len);

	iph->ttl = 0;
	iph->tos = 0;
	iph->frag_off = 0;
	iph->check = 0;
	if (ihl > sizeof(*iph)) {
	__be32 dummy;
	err = ip_clear_mutable_options(iph, &dummy);
	if (err)
	goto out_free;
	}

	skb_push(skb, ihl);

	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, ah_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, ihl);
	__skb_pull(skb, ah_hlen + ihl);
	skb_set_transport_header(skb, -ihl);

	err = nexthdr;

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

	static void ah4_err(struct sk_buff *skb, u32 info)
	{
	struct net *net = dev_net(skb->dev);
	const struct iphdr iph = (const struct iphdr )skb->data;
	struct ip_auth_hdr ah = (struct ip_auth_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, skb->mark, (const xfrm_address_t *)&iph->daddr,
	ah->spi, IPPROTO_AH, AF_INET);
	if (!x)
	return;
	pr_debug("pmtu discovery on SA AH/%08x/%08x\n",
	ntohl(ah->spi), ntohl(iph->daddr));
	xfrm_state_put(x);
	}

	static int ah_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)
	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_ahash().
	*/
	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("%s: %s digestsize %u != %hu\n",
	__func__, 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);

	if (x->props.flags & XFRM_STATE_ALIGN4)
	x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
	ahp->icv_trunc_len);
	else
	x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
	ahp->icv_trunc_len);
	if (x->props.mode == XFRM_MODE_TUNNEL)
	x->props.header_len += sizeof(struct iphdr);
	x->data = ahp;

	return 0;

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

	static void ah_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 ah_type =
	{
	.description = "AH4",
	.owner = THIS_MODULE,
	.proto = IPPROTO_AH,
	.flags = XFRM_TYPE_REPLAY_PROT,
	.init_state = ah_init_state,
	.destructor = ah_destroy,
	.input = ah_input,
	.output = ah_output
	};

	static const struct net_protocol ah4_protocol = {
	.handler = xfrm4_rcv,
	.err_handler = ah4_err,
	.no_policy = 1,
	.netns_ok = 1,
	};

	static int __init ah4_init(void)
	{
	if (xfrm_register_type(&ah_type, AF_INET) < 0) {
	pr_info("%s: can't add xfrm type\n", __func__);
	return -EAGAIN;
	}
	if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
	pr_info("%s: can't add protocol\n", __func__);
	xfrm_unregister_type(&ah_type, AF_INET);
	return -EAGAIN;
	}
	return 0;
	}

	static void __exit ah4_fini(void)
	{
	if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
	pr_info("%s: can't remove protocol\n", __func__);
	if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
	pr_info("%s: can't remove xfrm type\n", __func__);
	}

	module_init(ah4_init);
	module_exit(ah4_fini);
	MODULE_LICENSE("GPL");
	MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);