From: David Miller <davem@davemloft.net>
To: eric.dumazet@gmail.com
Cc: netdev@vger.kernel.org, zhiyunq@umich.edu, nanditad@google.com,
ncardwell@google.com, john.dykstra1@gmail.com
Subject: Re: [PATCH] tcp: should drop incoming frames without ACK flag set
Date: Wed, 26 Dec 2012 15:09:17 -0800 (PST) [thread overview]
Message-ID: <20121226.150917.847023967466840760.davem@davemloft.net> (raw)
In-Reply-To: <1356561874.20133.21098.camel@edumazet-glaptop>
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 26 Dec 2012 14:44:34 -0800
> [PATCH v2] tcp: should drop incoming frames without ACK flag set
>
> In commit 96e0bf4b5193d (tcp: Discard segments that ack data not yet
> sent) John Dykstra enforced a check against ack sequences.
>
> In commit 354e4aa391ed5 (tcp: RFC 5961 5.2 Blind Data Injection Attack
> Mitigation) I added more safety tests.
>
> But we missed fact that these tests are not performed if ACK bit is
> not set.
>
> RFC 793 3.9 mandates TCP should drop a frame without ACK flag set.
>
> " fifth check the ACK field,
> if the ACK bit is off drop the segment and return"
>
> Not doing so permits an attacker to only guess an acceptable sequence
> number, evading stronger checks.
>
> Many thanks to Zhiyun Qian for bringing this issue to our attention.
>
> See :
> http://web.eecs.umich.edu/~zhiyunq/pub/ccs12_TCP_sequence_number_inference.pdf
>
> Reported-by: Zhiyun Qian <zhiyunq@umich.edu>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
Applied, thanks Eric.
prev parent reply other threads:[~2012-12-26 23:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-26 17:10 [PATCH] tcp: should drop incoming frames without ACK flag set Eric Dumazet
2012-12-26 22:11 ` David Miller
2012-12-26 22:44 ` Eric Dumazet
2012-12-26 23:09 ` David Miller [this message]
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