Add "passphraseless submission key" to prerequisites

[eloquence]

While our key generation docs suggest that it is safe to generate a passphraseless submission key, they do not strictly require it. It's certainly possible to use an SVS with a passphrase-protected key.
https://docs.securedrop.org/en/stable/generate_submission_key.html

Our SDW installation procedure and test plans do not currently account for a key protected by a passphrase. Until/unless this is a use case we explicitly support, I would suggest that we list a passphraseless submission key as a prerequisite for the SecureDrop Workstation.

[conorsch]

Our SDW installation procedure and test plans do not currently account for a key protected by a passphrase. Until/unless this is a use case we explicitly support [...]

Given that split-gpg does not support passphrases on privkeys, we're not likely to change support anytime soon. Agree that clarification in the docs is the right approach.

[eaon]

That split-gpg doc is outdated then 😄 I use split-gpg with pinentry-gnome3 every day! But even so, the automated use from salt during initial setup that would make the use of passphrases on private keys cumbersome to support

[conorsch]

That split-gpg doc is outdated then

Good to know! I was surprised to see the feature explicitly omitted, even though I don't use it myself. And the original point stands: we're not likely to support it on SDW in the foreseeable future.

[zenmonkeykstop]

This came up recently for a new user, it would be good to update the install docs to flag the need for a passphrase0less version of the submission privkey. I'm agnostic on whether or not to provide instructions on removing the key, but I probably would not add said instructions in the main install flow as it would be irrelevant to a large majority of users.

[nathandyer]

Just to add a couple thoughts here:

• This might be a good candidate for a .. note::
• I recommend that we suggest that users reach out to support in the event that they have a submission key with a passphrase set so we can assist with exporting a version without a passphrase set. I'm not sure that the removal instructions are widely useful enough to live in our main docs (but happy to be persuaded otherwise)

[zenmonkeykstop]

If possible, the docs should allow folks to function without falling back to support. I'd agree they're probably not going to be widely useful (coz current server setup recommends against a passphrase) but putting them in a linked page makes sense IMO.

[lilyannehall]

Opened #284 if y'all wanna give feedback <3