linux/net/ipv4/ah4.c
Nicolas Dichtel fa9921e46f ipsec: allow to align IPv4 AH on 32 bits
The Linux IPv4 AH stack aligns the AH header on a 64 bit boundary
(like in IPv6). This is not RFC compliant (see RFC4302, Section
3.3.3.2.1), it should be aligned on 32 bits.

For most of the authentication algorithms, the ICV size is 96 bits.
The AH header alignment on 32 or 64 bits gives the same results.

However for SHA-256-128 for instance, the wrong 64 bit alignment results
in adding useless padding in IPv4 AH, which is forbidden by the RFC.

To avoid breaking backward compatibility, we use a new flag
(XFRM_STATE_ALIGN4) do change original behavior.

Initial patch from Dang Hongwu <hongwu.dang@6wind.com> and
Christophe Gouault <christophe.gouault@6wind.com>.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-02-08 14:00:40 -08:00

539 lines
12 KiB
C

#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(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));
}
err = ah->nexthdr;
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);
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;
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 = ah->nexthdr;
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;
if (err == -EBUSY)
err = NET_XMIT_DROP;
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);
struct iphdr *iph = (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, (xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
if (!x)
return;
printk(KERN_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)) {
printk(KERN_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);
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) {
printk(KERN_INFO "ip ah init: can't add xfrm type\n");
return -EAGAIN;
}
if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
printk(KERN_INFO "ip ah init: can't add protocol\n");
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)
printk(KERN_INFO "ip ah close: can't remove protocol\n");
if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
}
module_init(ah4_init);
module_exit(ah4_fini);
MODULE_LICENSE("GPL");
MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);