dovecot - Aug 2020 - [EXT] Re: mail_crypt folder keys without sql database

Hello,

Can the mail_crypt "folder keys" feature be used with encrypted user
keys in passwd-file without sql database? It seems that there is no guide in the
docs.

Best regards,
narangd
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> On 05/08/2020 18:45 secure.light.0417.road <secure.light.0417.road at
protonmail.com> wrote:
> 
> 
> Hello,
> 
> Can the?mail_crypt "folder keys" feature be used?with encrypted
user keys in passwd-file without sql database? It seems that there is no guide
in the docs.
> 
> Best regards,
> narangd
Dovecot stores folder and user keys into mail_attribute_dict. This does not have
to be SQL database.

You can also add `userdb_mail_crypt_private_password` into passwd-file to
provide it if you use passwd-file as userdb.

Aki

mail_crypt_private_password cannot be hashed, as it's used to encrypt the
key.

Aki
> On 06/08/2020 10:06 secure.light.0417.road <secure.light.0417.road at
protonmail.com> wrote:
> 
>  
> I've tried to append the field
"userdb_mail_crypt_private_password=<same-hashed-password-in-passwd-file>"
to the end of each user line in userdb as passwd-file. And use the command below
to generate keys.
> 
>   doveadm -o
plugin/mail_crypt_private_password=<not-hashed-user-password> mailbox
cryptokey generate -u <username> -U
> 
> I confirmed mail encryption work properly.
> 
> Also I've compared two "dovecot-attribute" files with and
without "mail_crypt_require_encrypted_user_key = yes". Seemingly they
have no difference. How to check that the private key in dovecot-attribute be
encrypted properly?
> 
> narangd
> 
> Sent with ProtonMail Secure Email.
> 
> ??????? Original Message ???????
> On Thursday, August 6, 2020 1:03 AM, Aki Tuomi <aki.tuomi at
open-xchange.com> wrote:
> 
> > > On 05/08/2020 18:45 secure.light.0417.road secure.light.0417.road
at protonmail.com wrote:
> > > Hello,
> > > Can the?mail_crypt "folder keys" feature be used?with
encrypted user keys in passwd-file without sql database? It seems that there is
no guide in the docs.
> > > Best regards,
> > > narangd
> >
> > Dovecot stores folder and user keys into mail_attribute_dict. This
does not have to be SQL database.
> >
> > You can also add `userdb_mail_crypt_private_password` into passwd-file
to provide it if you use passwd-file as userdb.
> >
> > Aki

> On 06/08/2020 13:52 secure.light.0417.road <secure.light.0417.road at
protonmail.com> wrote:
> 
>  
> Ah, right. The hashed password can't be used to encrypt.
> 
> I want to remove possibility to decrypt mails using materials in mail
servers in VPS. I've thought about below scenario:
> 
> 1. The client generates asymmetric keys in local.
> 2. The client sends the public key to the dovecot in the mail server.
> 3. The dovecot generates a symmetric key.
> 4. The dovecot encrypts a received mail with the symmetric key.
> 5. The dovecot also encrypts the symmetric key with the public key.
> 6. The client get the mail and encrypted symmetric key from server into
local and decrypts it using local private key.
> 
You probably want to use PGP then.
> Instead of 1 and 2, the way like "the dovecot generates all 3 and
removes only private key", can be considered with docker image deployment.
mail_crypt plugin is primarily intended to protect storage medium, and not end
user as such. While it does support this, it's not perfect tool for it, and
can be bit difficult to set up. Dovecot does not support client-supplied private
keys.
> 
> Is it possible with mail_crypt?
> 
> narangd
> 
Aki

p.s. please keep responses on the list.