Document the HSM Daemon

[settermjd]

I'm not quite sure if this is what you want, but I've done my best to take the existing hsmdaemon documentation, to work through it and revise it, where necessary; after which I've integrated it into the ownCloud docs.

@sharidas, can you let me know if it goes far enough, or if something is missing?

This fixes #586.

[sharidas]

This document looks excellent 👍 One small comment added regarding the PR mentioned.

[mmattel]

Not everyone is aware about the term HSM. I would therefore take the long name Hardware Security Module into the navigation and page header and then continue with the abbreviation HSM.

[sharidas]

LGTM 👍

[mmattel]

Before merging, pls see my comment #802 (comment)

Update: solved

[settermjd]

@butonic, have I understood you correctly with the changes made in ffda10b?

[butonic]

@settermjd one more thing:

When using hsmdaemon with an HSM, the keys are not stored on the same physical machine as ownCloud.

When using hsmdaemon with an HSM, the keys can be stored on a different physical machine as ownCloud.

Sorry for nitpicking: the keys may actually land on the same machine. The HSM might only be used to decrypt them. I think rephrasing with can is a good way to describe the situation.

[settermjd]

@butonic, with respect to #802 (comment), please do nit-pick. I'm all for it to ensure 100% accuracy and quality of the documentation. However, that change likely invalidates the two sentences that follow after.

[settermjd]

@butonic, can you review 605db58 pls?

[butonic]

@settermjd hm that sounds confusing ... why point out that there is still insecurity left ...

When using hsmdaemon with an HSM, the keys can be stored on a different physical machine as ownCloud.

Sounds more positive, doesn't it? I feel that it conveys the idea of moving the keys elsewhere. If it really happens depends on the implementation details of the HSM. We shouldn't bother going into that, otherwise we might have to go into the details of individual HSM modules and how and where they store key material. I think it still makes sense to give SoftHSM2 as an example later, together with the corresponding threat model.

[settermjd]

Okay. That sounds fair to me.

[settermjd]

@butonic, change made.