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Re: [TLS] datacenter TLS decryption as a three-party protocol

mrex@sap.com (Martin Rex) Wed, 19 July 2017 20:32 UTC

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Date: Wed, 19 Jul 2017 22:32:04 +0200
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Subject: Re: [TLS] datacenter TLS decryption as a three-party protocol
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Martin Rex wrote:
> 
> There were a few issues with F5 loadbalancers (that were just forwarding
> traffic, _not_ acting as reverse proxy) related to a borked F5 option called
> "FastL4forward", which occasionally caused the F5 box to truncate TCP streams
> (the box received&ACKed 5 MByte of TCP data towards the TLS Server, but
> forwarded only 74 KBytes to the client before closing the connection with
> a TCP FIN towards the TLS client.
> 
> And once I saw another strange TCP-level data corruption caused by
> some Riverbed WAN accellerator.

I forgot to mention how I analyzed the breakage created by the middleboxes:

network capture (tcpdump) with a IP-address capture filter for a dedicated
client machine was *perfectly* sufficient to determine the TCP-level breakage.

For the F5 cockup, we used a concurrent tcpdump capture on the box in both
directions, again with IP-address capture filter, in order to prove to the
vendor that his box is corrupting/truncating the TCP stream between
TLS client and TLS server.


-Martin

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