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

Sun, 08 Dec 2019 10:17:20 -0800

It's a known issue that the password will be set to silly value, most likely 'yes'.

You should generate the user key during provisioning with `doveadm cryptokey generate -Uu user -n password`. 

Aki
On 08/12/2019 16:22 uxqex4e...@elude.in wrote:


Technically creating and encrypting folder key does not
require decrypting user's private key. All folder keys
are encrypted with user's public key.
Problem is for that this is a new user. The new user has no private key. I
need for generating that private key. It do not the sense encrypts
something using a key public if there is no private key. Both key public
and private is mathematically related and have to be created together. I
am using the wrong command for creating the main user encrypted EC private
key?

Directing my question primary: it is any way to have the dovecot executes
a bash script in the time of the mailbox created (lda_mailbox_autocreate)?

Also, I notice extra behavior when I do:

1. I creates user in mysql database
2. I confirms it not exists mailbox for user
3. I confirms it not exists cryptokeys for user

root@localhost:/var/vmail# doveadm mailbox cryptokey list -u newuser -U
Folder Active Public ID
root@localhost:/var/vmail#
4. Before create mailbox or cryptokeys for user, I send mail from exist
user to new user
5. Postfix Delivers mail to dovecot
6. The dovecot accepts mail for new user and create mailbox automatically
(lda_mailbox_autocreate)
7. I check and see that dovecot creates key of user

root@localhost:/var/vmail# doveadm mailbox cryptokey list -u newuser -U
Folder Active Public ID
yes XYZ
root@localhost:/var/vmail#
How the possible??? I have put in settings of mail-crypt that keys of user
have to be encrypted (mail_crypt_require_encrypted_user_key = yes), but I
supply no key! How the dovecot creates main user encrypted public/private
EC keypair without key of encryption given?

I confirm that element of post for 'newuser' is encrypted, but of course I
can no decrypt the mail. I achieve error:

dovecot: imap(newuser...Error: Mailbox INBOX: UID=1: read()
failed...Private key not available: Cannot decrypt key XYZ
No well for executing generateKeys.sh on user first login. What if the
user receives email before first login? How I execute generateKeys.sh on
create of mailbox and how I do emails incoming without any keypair
created? For to reject or queue or save unencrypted until I generate
keypair? It possible?

On Sun, December 8, 2019 08:04, Aki Tuomi via dovecot wrote:
>

Technically creating and encrypting folder key does not require
decrypting user's private key. All folder keys are encrypted with user's
public key.
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Aki
>
On 08/12/2019 09:42 uxqex4efpu--- via dovecot <
dovecot@dovecot.org>
wrote:
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What it is way most best for causing bash script run (as root) of time
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mailbox created (lda_mailbox_autocreate)?
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I use dovecot 2.3.4.1 in Debian 10.
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And I use of mail-crypt-plugin
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I setup mail-crypt for requiring user encrypted EC key
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(mail_crypt_require_encrypted_user_key = yes). I want for passphrase
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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.
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For above I have plugin config
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mail_plugins = $mail_plugins mail_crypt
plugin {
mail_crypt_curve = secp256k1
mail_crypt_require_encrypted_user_key = yes
mail_crypt_save_version = 2
}
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And for returning userdb_mail_crypt_private_password, I have sql query
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password_query = SELECT username, password, \
SHA2( CONCAT('%w',salt), 512 ) AS userdb_mail_crypt_private_password \
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FROM virtual_users WHERE username='%u';
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But how I generate key of user automatically? Note for generating key of
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user, I need user password plaintext. I never save plaintext password of
user of the server.
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Also user of note creates in PHP of web of the server. And for security I
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do not allow PHP exec shell (php.ini disabled_functions). Definitely not
leaving PHP doveadm access!
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For solving subject to generate user key encrypted, I do imap of call of
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the service 'imap-postlogin' the service likes document "Post-login
scripting' write
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And 'imap-postlogin' execute my custom script with 'script-login' binary
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3533/src/util/script-login.c
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Here it is config for above
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service imap {
executable = imap imap-postlogin
}
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service imap-postlogin {
executable = script-login /usr/local/bin/generateKeys.sh
unix_listener imap-postlogin {
}
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}
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And generateKeys.sh it is script simple for generating keys with sha256()
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hash product mysql. Variable of note ${MAIL_CRYPT_PRIVATE_PASSWORD}
automatically put of 'userdb_mail_crypt_private_password' return of mysql
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field of query when documented
dings
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Fields returned by userdb lookup with their keys uppercased
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(e.g. if userdb returned home, it's stored in HOME).
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Here generatekeys.sh
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#!/bin/bash
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if [ `/usr/bin/doveadm mailbox cryptokey list -u "${USER}" -U >
/dev/null | wc -l` -lt 2 ]; then
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/usr/bin/doveadm -o
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"plugin/mail_crypt_private_password=${MAIL_CRYPT_PRIVATE_PASSWORD}"
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mailbox cryptokey generate -u "${USER}" -U > /dev/null
fi
exec "$@"
This work! But I want more good. By why execute each login? Possible has
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generateKeys.sh execute in the times only of dovecot create mailbox
(lda_mailbox_autocreate) instead?
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---
Aki Tuomi
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---
Aki Tuomi

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