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

["touch@xxxxxxxxxxxxxx" <touch@xxxxxxxxxxxxxx>]

It might be useful to add that most of those injection attacks are similar to the kind of attack possible when IPsec is carried inside IP tunnels or UDP tunnels when IPsec messages are split across tunnel messages. In those cases, the vulnerability depends on the predictability of the fragment identifier, which can be much smaller than the predictability of being within the TCP receive window sequence space, esp. for long-lived TCP connections.

Joe

—

Dr. Joe Touch, temporal epistemologist

www.strayalpha.com

On May 30, 2022, at 8:28 AM, Valery Smyslov <svan@xxxxxxxx> wrote:

Hi Joe, Christian,

 

From: touch@xxxxxxxxxxxxxx [mailto:touch@xxxxxxxxxxxxxx] 
Sent: Monday, May 30, 2022 6:21 PM
To: Christian Huitema
Cc: Valery Smyslov; secdir@xxxxxxxx; draft-ietf-ipsecme-rfc8229bis.all@xxxxxxxx; ipsec@xxxxxxxx; last-call@xxxxxxxx
Subject: Re: [Last-Call] Secdir last call review of draft-ietf-ipsecme-rfc8229bis-06

 

On May 30, 2022, at 8:00 AM, Christian Huitema <huitema@xxxxxxxxxxx> wrote:

 

The bar against TCP injection attacks might be lower than you think. An attacker that sees the traffic can easily inject TCP packet with sequence number that fit in the flow control window and are ahead of what the actual sender produced. 

 

It might be useful to be more specific about the issue. Data injection attacks on TCP connections interfere with the IPsec stream in a similar way to IP or UDP fragment attacks on IP or UDP tunnels that use fragmentation. 

 

In all three cases, attackers can corrupt in-transit packets via IP packet attacks, which is not possible with an unfragmented IPsec message.

 

In all three cases, this happens when an injection can overwrite a portion of an IPsec message.

 

Data isn’t injected to the user, though.

 

          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).

 

Regards,

Valery.

 

 

Joe

 

 

 

 

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