Multiple account privacy

[Ropyro]

Hi There --

I want to offer my friend an account in my Nextcloud instance but want to assure him that I can't look at his files. From what I'm reading on the old internet it looks like I'd have access to his files through my admin account. Is this true? If so, is there a way to configure it so his files are absolutely private?

[BrutalBirdie]

@Ropyro the magic word is "encryption"
https://docs.nextcloud.com/server/19/user_manual/files/encrypting_files.html

[Ropyro]

@BrutalBirdie Awesome, thanks And off I go...

[BrutalBirdie]

@Ropyro Don't run of too fast, I am reading a bit deeper into this...
I know Nextcloud Admins can impersonate to view Data of other users.
This should not work if server side encryption is enabled.

Read threw the doc of Nextcloud about the pros and cons about server side encryption.

[BrutalBirdie]

https://github.com/nextcloud/impersonate/issues/41#issuecomment-386062283

with E2E it doesn't matter because you can't open the files on the server. In other words the admin can impersonate you but without your mnemonic key they still can't access your E2E files.

Not sure how credible this user is tho. Still looking deeper.

---

Ehh I will just test it now.

[Ropyro]

@BrutalBirdie Ha -- yea, I see all that.

[Ropyro]

@BrutalBirdie It's gotta be possible. Right? I mean, I've used paid versions of Nextcloud in the past. I have to assume they didn't have access to my files. I hope, anyway.

[BrutalBirdie]

@Ropyro Okay so here are my first findings, which are.. well. Bad.

https://docs.nextcloud.com/server/23/admin_manual/configuration_files/encryption_configuration.html

I followed this doc.

Hmm well, lets try it with the cloudron file manager.

Good right?
Nope.

[BrutalBirdie]

@BrutalBirdie digging deeper

[Ropyro]

@BrutalBirdie Man, thanks for doing the leg-work here. I'll be buying you a beer

[BrutalBirdie]

I must be missing something?

Now you must log out and then log back in to initialize your encryption keys.

When you log back in, there is a checkbox for enabling encryption on your home storage. This is checked by default. Un-check to avoid encrypting your home storage.

This never happened? I must be missing something..

[Ropyro]

@BrutalBirdie I mean, I see an option to enable "server-side" encryption on the admin/security page but I assume that's different than what you're doing?

[BrutalBirdie]

@Ropyro Nah that's exactly what I am looking at.

Also this:
https://docs.nextcloud.com/server/23/admin_manual/configuration_files/encryption_configuration.html#enabling-users-file-recovery-keys

Does not exist for me.

If you want to team up on this we can do a discord call or something

[Ropyro]

@BrutalBirdie Ha! I'm bouncing back and forth between this and another project right now. I appreciate all your help. Gives me a direction to play around with. Beer forthcoming

[BrutalBirdie]

@Ropyro

Encryption keys are stored only on the Nextcloud server, eliminating exposure of your data to third-party storage providers. The encryption app does not protect your data if your Nextcloud server is compromised, and it does not prevent Nextcloud administrators from reading user’s files. This would require client-side encryption, which this app does not provide. If your Nextcloud server is not connected to any external storage services then it is better to use other encryption tools, such as file-level or whole-disk encryption.

This is by design.
https://docs.nextcloud.com/server/23/admin_manual/configuration_files/encryption_configuration.html
The first big yellow warning.

---

ps: Thanks for the Beer! Cheers

[BrutalBirdie]

And here we go for another round ...
https://apps.nextcloud.com/apps/impersonate

This app is not compatible with instances that have encryption enabled.

But.... it is? Its working? Right now?

[robi]

You can always encrypt before uploading.

Or use internxt.com which does ZK e2e for you.

[BrutalBirdie]

Ok... this is getting into a convoluted mess.

Now I found out there should be a per-user-encryption:
https://docs.nextcloud.com/server/latest/admin_manual/configuration_files/encryption_details.html#key-type-user-key

Funny how this is missing in the doc for the encryption ooc commands...........
https://docs.nextcloud.com/server/23/admin_manual/configuration_server/occ_command.html#encryption-label

And also not mentioned in the main doc where they show and tell about the Enabling users file recovery keys.

I've set up a new Nextcloud (with user managed by the app) and installed the Default Encryption Module then went into the Nextcloud app web-terminal and did a:

root@f6665ea8-5f0a-41f7-b8ae-be1719062c33:/app/code# sudo -u www-data php -f /app/code/occ encryption:disable-master-key
Warning: Only perform this operation for a fresh installations with no existing encrypted data! There is no way to enable the master key again. We strongly recommend to keep the master key, it provides significant performance improvements and is easier to handle for both, users and administrators. Do you really want to switch to per-user keys? (y/n) y
Master key successfully disabled.

Then I enabled the server wide encryption.

Ok understandable because: https://docs.nextcloud.com/server/latest/admin_manual/configuration_files/encryption_configuration.html#enabling-users-file-recovery-keys

So I set a recovery key. Good? Ehhhh... with that I can decrypt files from a user if he allows it.
Wait... if the user allows it? By default it's not allowed.
So if I try this in the web-terminal:

root@f6665ea8-5f0a-41f7-b8ae-be1719062c33:/app/code# sudo -u www-data php -f /app/code/occ encryption:decrypt-all eha
Disable server side encryption... done.


You are about to start to decrypt all files stored in eha's account.
It will depend on the encryption module and your setup if this is possible.
Depending on the number and size of your files this can take some time
Please make sure that no user access his files during this process!

Do you really want to continue? (y/n) y
prepare encryption modules...

Prepare "Default encryption module"

You can only decrypt the users files if you know
the users password or if he activated the recovery key.

Do you want to use the users login password to decrypt all files? (y/n) n
No recovery key available for user eha
Module "Default encryption module" does not support the functionality to decrypt all files again or the initialization of the module failed!
 aborted.
Server side encryption remains enabled

So now I impersonate the user... and allow it?

Please no....

Please don't tell me now that I can decrypt the user files afterwards.

root@f6665ea8-5f0a-41f7-b8ae-be1719062c33:/app/code# sudo -u www-data php -f /app/code/occ encryption:decrypt-all eha
Disable server side encryption... done.


You are about to start to decrypt all files stored in eha's account.
It will depend on the encryption module and your setup if this is possible.
Depending on the number and size of your files this can take some time
Please make sure that no user access his files during this process!

Do you really want to continue? (y/n) y
prepare encryption modules...

Prepare "Default encryption module"

You can only decrypt the users files if you know
the users password or if he activated the recovery key.

Do you want to use the users login password to decrypt all files? (y/n) n
Please enter the recovery key password: 
 done.





 starting to decrypt files... finished 
 [============================]


Files for following users couldn't be decrypted, 
maybe the user is not set up in a way that supports this operation: 
    eha
        /eha/files/allowed_recovery.md
        /eha/files/deny_recovery.md

Server side encryption remains enabled

thank god.

If I now look into the security tab as the user:

This looks bugged.
So disable it again:

and enable it again:

Hmmm this Recovery Key enabled did never happen as impersonated user.
So this could be used as an indicator if an admin tried to decrypt your files... good to know I guess.

So now I can decrypt the user files with the recovery password?

root@f6665ea8-5f0a-41f7-b8ae-be1719062c33:/app/code# sudo -u www-data php -f /app/code/occ encryption:decrypt-all eha
Disable server side encryption... done.


You are about to start to decrypt all files stored in eha's account.
It will depend on the encryption module and your setup if this is possible.
Depending on the number and size of your files this can take some time
Please make sure that no user access his files during this process!

Do you really want to continue? (y/n) y
prepare encryption modules...

Prepare "Default encryption module"

You can only decrypt the users files if you know
the users password or if he activated the recovery key.

Do you want to use the users login password to decrypt all files? (y/n) n
Please enter the recovery key password: 
 done.





 starting to decrypt files... finished 
 [============================]


all files could be decrypted successfully!
Server side encryption remains enabled

Yep worked.
...
Okay I will write that down a bit clearer tomorrow. (And try this again with LDAP instead of user management by the app)

My head is smoking.
This documentation of Nextcloud is a nightmare!

[Ropyro]

@BrutalBirdie Man, what a mess! I didn't have time to look into it today as deeply as you did. Can't thank you enough!

[mehdi]

Basically, what you want for this is end-to-end encryption (and I know a bit about this, it's literally my job to implement E2EE ^^).

The problem is that the nextcloud app that provides E2EE is bad, like really bad, like "my files just disappeared, i have no idea why" bad.

So, long story short, there is no simple way for you to provide this service to your friend with nextcloud with you not being able to look at their files.