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Re: Issue LC90

From: David Hull <dmh@tibco.com>
Date: Mon, 27 Jun 2005 15:41:57 -0400
To: Francisco Curbera <curbera@us.ibm.com>
Cc: public-ws-addressing@w3.org
Message-id: <42C05685.9030202@tibco.com>
Francisco Curbera wrote:

>Again, my understanding is that you filter our replay attacks before you do
>anything else, including RM.
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That's my understanding, too.

So, what does the security layer look at when making this determination?

Should it look at the [message id] or not?  Why or why not?

>Paco
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>                      David Hull                                                                                                   
>                      <dmh@tibco.com>          To:       Francisco Curbera/Watson/IBM@IBMUS                                        
>                                               cc:       public-ws-addressing@w3.org                                               
>                      06/27/2005 03:20         Subject:  Re: Issue LC90                                                            
>                      PM                                                                                                           
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>Francisco Curbera wrote:
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>>This is a composability issue. My understanding is that typically the
>>timestamp would protect the RM headers as well, so they will be different
>>in a retransmission.
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>So, in this case, what should the security layer look at?
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>>Paco
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>>                     David Hull
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>>                     <dmh@tibco.com>          To:       Francisco
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>Curbera/Watson/IBM@IBMUS
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>>                                              cc:
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>public-ws-addressing@w3.org
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>>                     06/27/2005 02:03         Subject:  Re: Issue LC90
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>>                     PM
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>>If a message is retransmitted for reliability purposes, the payload (that
>>is, the message the reliability layer thinks it's sending) will be
>>retransmitted verbatim.  The [message id] is part of this, so it will be
>>the same in both versions, just as the other WSA headers will be, and the
>>body for that matter.  There will be no part of the message payload that
>>could be used to tell if the message is a replay or a retransmission.
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>This
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>>is why the reliability layer uses its own sequence number.  The
>>retransmission will have a separate sequence number.  The security layer
>>can use this information to distinguish retransmissions from replays.  It
>>can't use anything in the payload.
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>>The current text says that the security layer should take care to consider
>>information that will not change when trying to see if anything has
>>changed.  The new text points out that the [message id] will not change
>>with a retransmission and looking at it won't help.  Further, it uses a
>>SHOULD NOT, instead of a MUST NOT, so that anyone who really wants to fold
>>in redundant information is free to do so.
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>>Francisco Curbera wrote:
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>>     Issue LC90 proposes changing the following paragraph in the security
>>     section,
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>>     "Some processors may use message identifiers ([message id]) as part
>>     of a
>>     uniqueness metric in order to detect replays of messages. Care
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>should
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>>     be
>>     taken to ensure that for purposes of replay detection, the message
>>     identifier is combined with other data, such as a timestamp, so that
>>     a
>>     legitimate retransmission of the message is not confused with a
>>     replay
>>     attack."
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>>     to the alternate text,
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>>     "For purposes of reliability and security, the [message id] property
>>     SHOULD
>>     regarded simply as another part of the message payload.  It SHOULD
>>     NOT be
>>     used as part of a uniqueness metric in order to detect replays of
>>     messages,
>>     as a message with a given [message id] may be legitimately re-sent
>>     for
>>     purposes of reliable transmission."
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>>     We think that there is no justification to say that you one cannot
>>     use
>>     messageID as part of an uniqueness criterion for security purposes,
>>     so the
>>     "SHOULD NOT" in the proposed text is unjustified. The original text
>>     is more
>>     balanced, recognizing that message_if may be used and giving the
>>     right
>>     advice if one chooses to do so.
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>>     I propose we close with no change.
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>>     Paco
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Received on Monday, 27 June 2005 19:42:05 GMT

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