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