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Hi,
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just to mention this. If you use the stored password hash, it equals to using a plain text string. Depending on your threat model it might or not be an issue that admins have access to the password used to encrypt mails.
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Aki
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On 04/03/2023 16:12 EET Jeremy <<a href="mailto:mailinglist-subscriptions@protonmail.com">mailinglist-subscriptions@protonmail.com</a>> wrote:
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Hi again,
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I was able to solve both questions. I was overthinking things.
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A solution to the first question about mail_attribute_dict was simply to use other available variables to point to the virtual user's maildir paths. Like so: /var/mail/%d/%u/dovecot-attributes
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As for the second question:
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When I asked it, I was uncertain if dovecot would be able to cope with a hashed password for userdb_mail_crypt_private_password. I somehow believed dovecot required a plain text password there, as per the '%w' in the example password_query. Turns out this was not the case. Simply providing the already hashed password of the password field did the trick. So:
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password_query = SELECT \
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email as user, password, \
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password AS userdb_mail_crypt_private_password \
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FROM virtual_users WHERE email='%u';
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Hope this is of help to others if they stumble upon this question.
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------- Original Message -------
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On Thursday, February 23rd, 2023 at 08:53, Jeremy <<a href="mailto:mailinglist-subscriptions@protonmail.com">mailinglist-subscriptions@protonmail.com</a>> wrote:
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Hi again,
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I am using dovecot 2.3.16, along with postfix and a PostgreSQL database for managing virtual accounts.
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After an initial topic from me about encrypting already existent mail, I could now use some pointers on how to set up the mail-crypt plugin for pure virtual accounts (i.e. that have no matching system users and/or home directories. I hope somebody can clarify a few things that are not entirely clear to me yet.
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After doing my own research, I believe the following should be possible:
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I'd like to use the password of virtual email accounts to let dovecot encrypt/decrypt the keys needed to encrypt/decrypt the mail in the relevant folders.
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As per the documentation @ <a href="https://doc.dovecot.org/configuration_manual/mail_crypt_plugin/" target="_blank" rel="noopener">https://doc.dovecot.org/configuration_manual/mail_crypt_plugin/</a> I believe this would be all the configuration I need:
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# Config
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mail_attribute_dict = file:%h/Maildir/dovecot-attributes
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mail_plugins = $mail_plugins mail_crypt
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plugin {
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mail_crypt_curve = secp521r1 # or some other preferred curve
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mail_crypt_save_version = 2
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mail_crypt_require_encrypted_user_key = yes # necessary for encrypting keys with user password
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}
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# File: /etc/dovecot/dovecot-sql.conf.ext
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password_query = SELECT \
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email as user, password, \
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'%w' AS userdb_mail_crypt_private_password \
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FROM virtual_users WHERE email='%u';
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My first question is:
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Is it possible to configure mail_attribute_dict in such a way as to not use home directories. Since I only use virtual accounts, without those accounts having home directories, can I somehow tell dovecot to save the attributes into the PostsreSQL database, for instance? If not, can you suggest another approach, without having to create home directories for virtual users?
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My second question is:
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The documentation warns about not using password directly in the above SQL query:
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Choosing encryption key
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DO NOT use password directly. It can contain % which is interpreted as > variable expansion and can cause errors.
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Does this refer to not accidentally substituting '%w' with password? In other words, if I leave the above query as is, should I be good, even if plain text passwords of users potentially have % signs in them? Or would I need to take further measurements? (The passwords in my database are already hashed, by the way).
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I hope somebody can offer some guidance on this. Thanks.
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<pre>---
Aki Tuomi</pre>
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