Re: [IPsec] [Last-Call] Secdir last call review of draft-ietf-ipsecme-rfc8229bis-06

[Christian Huitema <[e-mail]>]

On 5/30/2022 8:28 AM, Valery Smyslov wrote:
> Hi Joe, Christian,
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>            I suggest we add the following text to the Security considerations:
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>     TCP data injection attacks have no effect on application data since
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>     IPsec provides data integrity.  However, they can have some effect,
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>     mostly as a DoS attack:
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>     o  if an attacker alters the content of the Length field that
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>        separates packets, then the receiver will incorrectly identify the
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>        margins of the following packets and will drop all of them or even
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>        tear down the TCP connection if the content of the Length field
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>        happens to be 0 or 1 (see Section 3)
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>     o  if the content of an IKE message is altered, then it will be
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>        dropped by the receiver; if the dropped message is the IKE request
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>        message, then the initiator will tear down the IKE SA after some
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>        timeout, since in most cases the request message will not be
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>        retransmitted (as advised in Section 6.2) and thus the response
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>        will never be received
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>     o  if an attacker alters the non-ESP marker then IKE packets will be
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>        dispatched to ESP and sometimes visa versa, those packets will be
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>        dropped
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>     o  if an attacker modifies TCP-Encapsulated stream prefix or
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>        unencrypted IKE messages before IKE SA is established, then in
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>        most cases this will result in failure to establish IKE SA, often
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>        with false "authentication failed" diagnostics
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>     An attacker capable of blocking UDP traffic can force peers to use
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>     TCP encapsulation, thus degrading the performance and making the
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>     connection more vulnerable to DoS attacks.  Note, that attacker
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>     capable to modify packets on the wire or to block them can prevent
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>     peers to communicate regardless of the transport being used.
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> (The text is still a draft, I’ve been waiting for Tommy to review it).

That text works. The main point is to be clear that IPSEC over TCP is 
significantly more fragile than IPSEC over UDP or IP, and the text does 
that. My only reservation is that you describe TCP injection as altering 
the packet, as if an attacker catches a packet in flight, changes some 
of the content, and then forwards it. That's not what they typically do. 
Attackers simply send TCP packets with a sequence number that is "in 
windows", so the receiver accepts the content of that packet instead of 
the genuine bytes sent by the peer at that same sequence number.

-- Christian Huitema