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

[Valery Smyslov <[e-mail]>]

Hi Joe,

 

From: [e-mail] [mailto:[e-mail]] 
Sent: Monday, May 30, 2022 10:57 PM
To: Tero Kivinen
Cc: Valery Smyslov; Christian Huitema; [e-mail]; [e-mail]; [e-mail]; [e-mail]
Subject: Re: [Last-Call] Secdir last call review of draft-ietf-ipsecme-rfc8229bis-06

 

On May 30, 2022, at 12:25 PM, Tero Kivinen <[e-mail]> wrote:

 

I think we need to add text explaining how to detect when the TCP
length framing gets messed up by attacks, and how to recover (i.e.,
close down the TCP channel and recreate the TCP channel). 

 

The impact of RSTs can be limited for this purpose by recommending RFC5961 for these connections.

 

          I’ve added a reference to RFC 5961.

 

          Currently the new text in the Security considerations looks like:

 

   TCP connections are also susceptible to RST and other spoofing

   attacks [RFC4953].  This specification makes IPsec tolerant of sudden

   TCP connection drops, but if an attacker is able to tear down TCP

   connections, IPsec connection's performance can suffer, effectively

   making this a DoS attack.

 

   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

 

   [RFC5961] discusses how TCP injection attacks can be mitigated.

 

   Note, that data injection attacks are also possible on IP level (e.g.

   when IP fragmentation is used) resulting in DoS attack even if TCP

   encapsulation is not used.  On the other hand, TCP injection attacks

   are easier to mount than the IP fragmentation injection attacks, because

   TCP keeps a long receive window open that's a sitting target for such

   attacks.

 

   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.

 

 

But if even data injection has the same impact, it’d be much better to see if there’s a way to recover “sync” in the byte stream rather than expecting a new connection.

 

          TCP connections can be closed and re-open – I don’t think this is a big problem if IKE SA survives.

          The real problem is when IKE SA (and all Child SAs) is teared down as result of attack. 

          This can happen when IKE message is corrupted or incorrectly parsed as a result of data injection attack.

 

          Currently the draft says that there is no need to retransmit the request message in case of TCP (with SHOULD NOT).

          We can add a note that implementations MAY retransmit messages to mitigate a possibility of data injection attacks.

 

          Regards,

          Valery.

 

 

 

Joe