Re: [TLS] Comments on

[Bill Frantz <[e-mail]>]

On 2/18/14 at 4:56 AM, [e-mail] (Niels Möller) wrote:

>Bill Frantz <[e-mail]> writes:
>
>>However, it is a situation that any application that is reading files
>>needs to be prepared to handle. Disk errors and all that...
>
>I think there's a difference between on one hand, truncation due to
>random failures of your own, reasonably trusted, hardware. And on the
>other hand, truncation caused the enemy attacking the communication
>channel for some evil purpose.

 From the point of view of an application, there isn't much 
difference. In both cases, it receives notification from the 
infrastructure that the read couldn't complete because an error occurred.

System managers certainly want to know if they are under attack, 
but even just knowing that there was a MAC verification failure 
is not solidly definitive. There could have been an undetected 
failure in the transmission which only showed up because of the 
MAC failure -- since the MAC is a stronger check than the checks 
in TCP/IP. IF I were that manager, one failure -- be on high 
alert for attackers. Two failures -- try to located the 
attackers and deal with them. :-)


>If we really want to make progress with this discussion, I guess we must
>also distinguish between file types where appending data doesn't change
>the meaning of earlier data (e.g, a typical log file), and file types
>where appending data can change the meaning radically (e.g., consider a
>document format where you can add data at the end of the file which adds
>a mark "this document is fake" on top of every page when the file is
>displayed or printed).

I see no need to make such a distinction at our level. We will 
give the application an error that says we couldn't give it all 
the data. How it handles the error is not our problem. Handling 
this error like any other "couldn't read the rest of the file" 
error seems right in all cases.

Cheers - Bill

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