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authorMartin Willi <martin@strongswan.org>2010-12-08 04:37:51 +0000
committerDavid S. Miller <davem@davemloft.net>2010-12-10 14:43:59 -0800
commit040253c931e336360453c8d81f76d1b010b2b5e7 (patch)
treee9fa38b6cd2a12eec1f12f1a89258f3713cfabd7
parentd979e20f2b9f8a50c8d5f889e0b5d78580440d1f (diff)
xfrm: Traffic Flow Confidentiality for IPv6 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>
-rw-r--r--net/ipv6/esp6.c32
1 files changed, 24 insertions, 8 deletions
diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index ee9b93bdd6a2..1b5c9825743b 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -49,6 +49,8 @@ struct esp_skb_cb {
#define ESP_SKB_CB(__skb) ((struct esp_skb_cb *)&((__skb)->cb[0]))
+static u32 esp6_get_mtu(struct xfrm_state *x, int mtu);
+
/*
* Allocate an AEAD request structure with extra space for SG and IV.
*
@@ -140,6 +142,8 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
int blksize;
int clen;
int alen;
+ int plen;
+ int tfclen;
int nfrags;
u8 *iv;
u8 *tail;
@@ -148,18 +152,26 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
/* skb is pure payload to encrypt */
err = -ENOMEM;
- /* Round to block size */
- clen = skb->len;
-
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, esp6_get_mtu(x, dst->child_mtu_cached));
+ if (skb->len < padto)
+ tfclen = padto - skb->len;
+ }
blksize = ALIGN(crypto_aead_blocksize(aead), 4);
- clen = ALIGN(clen + 2, blksize);
+ clen = ALIGN(skb->len + 2 + tfclen, blksize);
if (esp->padlen)
clen = ALIGN(clen, esp->padlen);
+ plen = clen - skb->len - tfclen;
- if ((err = skb_cow_data(skb, clen - skb->len + alen, &trailer)) < 0)
+ err = skb_cow_data(skb, tfclen + plen + alen, &trailer);
+ if (err < 0)
goto error;
nfrags = err;
@@ -174,13 +186,17 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
/* Fill padding... */
tail = skb_tail_pointer(trailer);
+ if (tfclen) {
+ memset(tail, 0, tfclen);
+ tail += tfclen;
+ }
do {
int i;
- for (i=0; i<clen-skb->len - 2; i++)
+ for (i = 0; i < plen - 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);
+ 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));