Add configuration flag for allowing SHA1 hash algorithm

[sosnovsky]

[martgil]

Hi @sosnovsky just curious — what’s the reason we need to allow SHA-1 in OpenPGP.js?

[sosnovsky]

Hi @martgil, I was composing message to our customer and got this error saying that their key is unusable. I checked their key and found that error occurs because key uses the SHA-1 algorithm. After checking the keys of their other users, I discovered that many of them also use SHA-1. So completely disabling SHA-1 would break their company email communication.
For now it'll be better to just show some warning for users with SHA-1 keys, saying that their keys are insecure and should be updated to use more secure algorithms.

[martgil]

Hi @sosnovsky - If I understand it correctly, therefore allowing this insecure SHA-1 should only be applied if both conditions are meet:

1. only for enterprise users
2. who sets the flag for allowing sha1

So, we'll be needing a new client configuration flag then document it here: https://flowcrypt.com/docs/technical/enterprise-admin-panel/usage/domain-configuration/client-configuration.html