Re: The TCP and UDP checksum algorithm may soon need updating

Richard Barnes <rlb@ipv.sx> Thu, 04 June 2020 21:45 UTC

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From: Richard Barnes <rlb@ipv.sx>
Date: Thu, 4 Jun 2020 17:45:25 -0400
Message-ID: <CAL02cgS4ZAks-eXc78r7zq6SnCUZ5Jvush_bVbtL-M-z-7EaEg@mail.gmail.com>
Subject: Re: The TCP and UDP checksum algorithm may soon need updating
To: Craig Partridge <craig@tereschau.net>
Cc: Joe Touch <touch@strayalpha.com>, IETF discussion list <ietf@ietf.org>
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It seems like you're assuming that file transfer applications are sending a
large file all in one go, over a single TCP session.  All of the serious
file transfer applications that come to my mind protect against this by
handling large things in more manageable chunks -- think BitTorrent,
MPEG-DASH, even HTTP range requests.  That's prudent application design not
just because TCP passes corrupted data sometimes, but because transport
connections fail for all sorts of reasons.

--Richard

On Thu, Jun 4, 2020 at 5:26 PM Craig Partridge <craig@tereschau.net> wrote:

> The SSH spec says terminate on failure and that it requires a reliable
> underpinning.
>
> Termination on error is no good.  One of the studies shows huge failure
> rates (over 50%) for large file transfers.  One guess is that's due to
> security protocols terminating when TCP hands up something with an error.
>
> Craig
>
> On Thu, Jun 4, 2020 at 3:19 PM Richard Barnes <rlb@ipv.sx> wrote:
>
>> Yeah, secure transports already consider the data from the network
>> untrusted, including TLS and DTLS, but also IPsec/ESP, SSH, SRTP and QUIC.
>> As long as those protocols are using reasonably modern, AEAD ciphers, the
>> worst impact of corruption in the transport is DoS.
>>
>> That said, there might be some pretty hard crashes in cases where the
>> security protocol relies on the transport for something.  For example, TLS
>> doesn't have a mechanism for requesting that data be re-sent in the event
>> of loss/corruption, because it's assumed that TCP provides that.  If
>> corruption is only detected at the TLS layer, there's not a way to
>> recover.  That said, I wouldn't be surprised if many TLS stacks close the
>> connection on bad data anyway.
>>
>> On the UDP side, there should be no issue.  Anything above UDP has to
>> tolerate loss anyway, so there should be mechanisms that will require from
>> corruption-treated-as-loss.
>>
>> So there may be some feedback loops to close, but that's a more limited,
>> host-internal problem.
>>
>> In any case -- one more reason to encrypt everything!
>>
>> --Richard
>>
>> On Thu, Jun 4, 2020 at 4:17 PM Craig Partridge <craig@tereschau.net>
>> wrote:
>>
>>> Ah, I somehow had missed that.
>>>
>>> Looks like it does the trick if we need it. Not sure if we'd have to
>>> update the optional checksum to use a new checksum too.
>>>
>>> Craig
>>>
>>> On Thu, Jun 4, 2020 at 1:33 PM Joe Touch <touch@strayalpha.com
>>> <touch@strayalpha..com>> wrote:
>>>
>>>> See draft-ietf-tsvwg-udp-options
>>>>
>>>> > On Jun 4, 2020, at 12:13 PM, Craig Partridge <craig@tereschau.net>
>>>> wrote:
>>>> >
>>>> > Then there's UDP.  UDP has no options.
>>>>
>>>
>>>
>>> --
>>> *****
>>> Craig Partridge's email account for professional society activities and
>>> mailing lists.
>>>
>>
>
> --
> *****
> Craig Partridge's email account for professional society activities and
> mailing lists.
>