From 040253c931e336360453c8d81f76d1b010b2b5e7 Mon Sep 17 00:00:00 2001 From: Martin Willi Date: Wed, 8 Dec 2010 04:37:51 +0000 Subject: [PATCH] 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 Acked-by: Herbert Xu Signed-off-by: David S. Miller --- net/ipv6/esp6.c | 32 ++++++++++++++++++++++++-------- 1 file 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; ilen - 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)); -- 2.30.2