bash script hook lda_mailbox_autocreate for generate mail-crypt user encrypted private key with user password

[uxqex4efpu at elude.in]

What it is way most best for causing bash script run (as root) of time
mailbox created (lda_mailbox_autocreate)?

I use dovecot 2.3.4.1 in Debian 10.

And I use of mail-crypt-plugin
https://doc.dovecot.org/configuration_manual/mail_crypt_plugin/

I setup mail-crypt for requiring user encrypted EC key
(mail_crypt_require_encrypted_user_key = yes). I want for passphrase
encrypt EC key using client plaintext password. There is credential no
stored on server. But for user with use password too bad, I concatenate
user plaintext password with random salt. And then string to SHA512() hash
and use as decryption key (mail_crypt_private_password) for EC private
key.

For above I have plugin config

>   mail_plugins = $mail_plugins mail_crypt
>   plugin {
>     mail_crypt_curve = secp256k1
>     mail_crypt_require_encrypted_user_key = yes
>     mail_crypt_save_version = 2
>   }

And for returning userdb_mail_crypt_private_password, I have sql query

>   password_query = SELECT username, password, \
>     SHA2( CONCAT('%w',salt), 512 ) AS userdb_mail_crypt_private_password \
>     FROM virtual_users WHERE username='%u';

But how I generate key of user automatically? Note for generating key of
user, I need user password plaintext. I never save plaintext password of
user of the server.

Also user of note creates in PHP of web of the server. And for security I
do not allow PHP exec shell (php.ini disabled_functions). Definitely not
leaving PHP doveadm access!

For solving subject to generate user key encrypted, I do imap of call of
the service 'imap-postlogin' the service likes document "Post-login
scripting' write
https://doc.dovecot.org/admin_manual/post_login_scripting/

And 'imap-postlogin' execute my custom  script with 'script-login' binary
https://github.com/dovecot/core/blob/8606e1abb90a1c91357b84bf547a89564d053533/src/util/script-login.c

Here it is config for above

>   service imap {
>     executable = imap imap-postlogin
>   }
>   service imap-postlogin {
>     executable = script-login /usr/local/bin/generateKeys.sh
>     unix_listener imap-postlogin {
>     }
>   }

And generateKeys.sh it is script simple for generating keys with sha256()
hash product mysql. Variable of note ${MAIL_CRYPT_PRIVATE_PASSWORD}
automatically put of 'userdb_mail_crypt_private_password' return of mysql
field of query when documented
https://doc.dovecot.org/admin_manual/post_login_scripting/running-surroundings

> Fields returned by userdb lookup with their keys uppercased
> (e.g. if userdb returned home, it's stored in HOME).

Here generatekeys.sh

>   #!/bin/bash
>   if [ `/usr/bin/doveadm mailbox cryptokey list -u "${USER}" -U >
/dev/null | wc -l` -lt 2 ]; then
>           /usr/bin/doveadm -o
"plugin/mail_crypt_private_password=${MAIL_CRYPT_PRIVATE_PASSWORD}"
mailbox cryptokey generate -u "${USER}" -U > /dev/null
>   fi
>   exec "$@"

This work! But I want more good. By why execute each login? Possible has
generateKeys.sh execute in the times only of dovecot create mailbox
(lda_mailbox_autocreate) instead?