kernel-ark/net/ipv4/esp4.c
Martin Willi d979e20f2b xfrm: Traffic Flow Confidentiality for IPv4 ESP
Add TFC padding to all packets smaller than the boundary configured
on the xfrm state. If the boundary is larger than the PMTU, limit
padding to the PMTU.

Signed-off-by: Martin Willi <martin@strongswan.org>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2010-12-10 14:43:59 -08:00

667 lines
15 KiB
C

#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]))
static u32 esp4_get_mtu(struct xfrm_state *x, int mtu);
/*
* 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 plen;
int tfclen;
int nfrags;
/* skb is pure payload to encrypt */
err = -ENOMEM;
esp = x->data;
aead = esp->aead;
alen = crypto_aead_authsize(aead);
tfclen = 0;
if (x->tfcpad) {
struct xfrm_dst *dst = (struct xfrm_dst *)skb_dst(skb);
u32 padto;
padto = min(x->tfcpad, esp4_get_mtu(x, dst->child_mtu_cached));
if (skb->len < padto)
tfclen = padto - skb->len;
}
blksize = ALIGN(crypto_aead_blocksize(aead), 4);
clen = ALIGN(skb->len + 2 + tfclen, blksize);
if (esp->padlen)
clen = ALIGN(clen, esp->padlen);
plen = clen - skb->len - tfclen;
err = skb_cow_data(skb, tfclen + plen + alen, &trailer);
if (err < 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);
if (tfclen) {
memset(tail, 0, tfclen);
tail += tfclen;
}
do {
int i;
for (i = 0; i < plen - 2; i++)
tail[i] = i + 1;
} while (0);
tail[plen - 2] = plen - 2;
tail[plen - 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, skb->mark, (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, x->aalg->alg_trunc_len / 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);