Removed DHE SSL ciphers in TLS RSA key exchange

[Rocketct]

Removed DHE SSL ciphers to fix issue #270

cc:\ @sandeepmistry tested

[sandeepmistry]

Let's see what feedback Microchip has on these changes.

[adriens]

🙏 I'll give it a try pretty soon as I jave received some new hardware (I don't want to break the actual working one) . Thanks for this 👍

[sandeepmistry]

Tested with the following domains + WiFiSSLClient example sketch:

• www.google.com
• www.arduino.cc
• maker.ifttt.com
• example.com

Looks good!

[sandeepmistry]

@gvarisco any opinions on this change?

With the DHE ciphers enabled the connection to maker.ifttt.com would fail because the server had a 512 byte public key which the WINC1500 firmware can't handle.

Michele from Microchip is also in agreement with this change:

Anyway it looks to be good to me.

I believe that, originally, the TLS client was somehow limited to use cipher suites that it could not actually support.

By adding the RSA for authentication mechanism, 128 AES for encryption and 256 SHA for integrity we are well in between the winc1500 boundaries.

[adriens]

@sandeepmistry : could you give a try to https://www.heroku.com/ ?... I have some REST services ther I'd like to consume ;-p

[gvarisco]

@sandeepmistry +1, I'm happy to remove DHE-based ciphers. LGTM.

[sandeepmistry]

@gvarisco great, thanks for the feedback!