| From | Greg Kroah-Hartman <> | Subject | [ 027/133] xfrm: Workaround incompatibility of ESN and async crypto | Date | Thu, 11 Oct 2012 07:50:53 +0900 |
| |
3.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Steffen Klassert <steffen.klassert@secunet.com>
[ Upstream commit 3b59df46a449ec9975146d71318c4777ad086744 ]
ESN for esp is defined in RFC 4303. This RFC assumes that the sequence number counters are always up to date. However, this is not true if an async crypto algorithm is employed.
If the sequence number counters are not up to date on sequence number check, we may incorrectly update the upper 32 bit of the sequence number. This leads to a DOS.
We workaround this by comparing the upper sequence number, (used for authentication) with the upper sequence number computed after the async processing. We drop the packet if these numbers are different.
To do this, we introduce a recheck function that does this check in the ESN case.
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- include/net/xfrm.h | 3 +++ net/xfrm/xfrm_input.c | 2 +- net/xfrm/xfrm_replay.c | 15 +++++++++++++++ 3 files changed, 19 insertions(+), 1 deletion(-)
--- a/include/net/xfrm.h +++ b/include/net/xfrm.h @@ -269,6 +269,9 @@ struct xfrm_replay { int (*check)(struct xfrm_state *x, struct sk_buff *skb, __be32 net_seq); + int (*recheck)(struct xfrm_state *x, + struct sk_buff *skb, + __be32 net_seq); void (*notify)(struct xfrm_state *x, int event); int (*overflow)(struct xfrm_state *x, struct sk_buff *skb); }; --- a/net/xfrm/xfrm_input.c +++ b/net/xfrm/xfrm_input.c @@ -212,7 +212,7 @@ resume: /* only the first xfrm gets the encap type */ encap_type = 0; - if (async && x->repl->check(x, skb, seq)) { + if (async && x->repl->recheck(x, skb, seq)) { XFRM_INC_STATS(net, LINUX_MIB_XFRMINSTATESEQERROR); goto drop_unlock; } --- a/net/xfrm/xfrm_replay.c +++ b/net/xfrm/xfrm_replay.c @@ -420,6 +420,18 @@ err: return -EINVAL; } +static int xfrm_replay_recheck_esn(struct xfrm_state *x, + struct sk_buff *skb, __be32 net_seq) +{ + if (unlikely(XFRM_SKB_CB(skb)->seq.input.hi != + htonl(xfrm_replay_seqhi(x, net_seq)))) { + x->stats.replay_window++; + return -EINVAL; + } + + return xfrm_replay_check_esn(x, skb, net_seq); +} + static void xfrm_replay_advance_esn(struct xfrm_state *x, __be32 net_seq) { unsigned int bitnr, nr, i; @@ -479,6 +491,7 @@ static void xfrm_replay_advance_esn(stru static struct xfrm_replay xfrm_replay_legacy = { .advance = xfrm_replay_advance, .check = xfrm_replay_check, + .recheck = xfrm_replay_check, .notify = xfrm_replay_notify, .overflow = xfrm_replay_overflow, }; @@ -486,6 +499,7 @@ static struct xfrm_replay xfrm_replay_le static struct xfrm_replay xfrm_replay_bmp = { .advance = xfrm_replay_advance_bmp, .check = xfrm_replay_check_bmp, + .recheck = xfrm_replay_check_bmp, .notify = xfrm_replay_notify_bmp, .overflow = xfrm_replay_overflow_bmp, }; @@ -493,6 +507,7 @@ static struct xfrm_replay xfrm_replay_bm static struct xfrm_replay xfrm_replay_esn = { .advance = xfrm_replay_advance_esn, .check = xfrm_replay_check_esn, + .recheck = xfrm_replay_recheck_esn, .notify = xfrm_replay_notify_bmp, .overflow = xfrm_replay_overflow_esn, };
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