HTTP Public Key Pinning (HPKP) support

[rugk]

I wonder if you support HPKP. In case not, it would be awesome if you'll add support.
E.g. Posteo supports it and it can be easily implemented as it is just a HTTP header. However the result is a huge security improvement making MITM attacks much more difficult.

Here more information about HPKP:

• https://en.wikipedia.org/wiki/HTTP_Public_Key_Pinning
• https://scotthelme.co.uk/guidance-on-setting-up-hpkp/
• https://developer.mozilla.org/en-US/docs/Web/Security/Public_Key_Pinning

[rugk]

BTW, here is Android's doc about how to do key pinning in general:
https://developer.android.com/training/articles/security-config.html#CertificatePinning

You could even allow such manual key pinning by letting users enter the cert hash, or, as said, just support HPKP, where this is done automatically.

[rfc2822]

@rugk The mentioned pinning method is to pin certain certificates which are built in the app. It won't help in the DAVdroid use case.

[rugk]

@rfc2822 Hmm, okay… Too bad.

[rfc2822]

By the way… http://www.zdnet.com/article/google-chrome-is-backing-away-from-public-key-pinning-and-heres-why/