[Dovecot] Question about salted hashes

[Tobias Maffert]

Hello.

I'm switching from b1gmail to my own setup which consists of
Postfix+Dovecot+MySQL (and maybe VBoxAdm). There are two problems: -
b1gmail is using unsalted MD5 hashes. Is there any good way to make my
new setup backward compatible? So I don't have to force all of my 50k
users to change their password. - How do I change my setup to salted
SHA256 (or an even better algorithm). And how do I make the hashes
compatible between Postfix, Dovecot, MySQL (and maybe VBoxAdm)?

My system:

Debian Squeeze
Postfix version: 2.7.1
Dovecot version: 1.2.15

-----------------------------------------------
dovecot -n

# 1.2.15: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-5-686 i686 Debian 6.0.6
protocols: imap pop3
disable_plaintext_auth: no
login_dir: /var/run/dovecot/login
login_executable(default): /usr/lib/dovecot/imap-login
login_executable(imap): /usr/lib/dovecot/imap-login
login_executable(pop3): /usr/lib/dovecot/pop3-login
mail_access_groups: vmail
mail_debug: yes
mbox_write_locks: fcntl dotlock
mail_executable(default): /usr/lib/dovecot/imap
mail_executable(imap): /usr/lib/dovecot/imap
mail_executable(pop3): /usr/lib/dovecot/pop3
mail_plugins(default): quota imap_quota
mail_plugins(imap): quota imap_quota
mail_plugins(pop3): quota
mail_plugin_dir(default): /usr/lib/dovecot/modules/imap
mail_plugin_dir(imap): /usr/lib/dovecot/modules/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/modules/pop3
pop3_uidl_format(default): %08Xu%08Xv
pop3_uidl_format(imap): %08Xu%08Xv
pop3_uidl_format(pop3): UID%u-%v
lda:
  postmaster_address: <postmaster-address>
  auth_socket_path: /var/run/dovecot/auth-master
  mail_plugins: quota
  sendmail_path: /usr/sbin/sendmail
auth default:
  mechanisms: plain login
  user: vmail
  passdb:
    driver: sql
    args: /etc/dovecot/dovecot-sql.conf
  userdb:
    driver: prefetch
  userdb:
    driver: sql
    args: /etc/dovecot/dovecot-sql.conf
  socket:
    type: listen
    client:
      path: /var/spool/postfix/private/auth
      mode: 432
      user: postfix
      group: postfix
    master:
      path: /var/run/dovecot/auth-master
      mode: 432
      user: vmail
      group: vmail
plugin:
  quota: maildir

-----------------------------------------------

driver = mysql
connect = host=127.0.0.1 dbname=smail user=smail password=mypw
default_pass_scheme = CRYPT
password_query = SELECT username AS user, password_enc AS password,
CONCAT(homedir, maildir) AS userdb_home, uid AS userdb_uid, gid AS
userdb_gid,  CONCAT('maildir:', homedir, maildir) AS userdb_mail,
CONCAT('maildir:storage=', (quota*1024)) as userdb_quota FROM mail_users
WHERE (username = '%u' OR email = '%u') AND ((imap = 1 AND '%Ls' =
'imap') OR (pop3 = 1 AND '%Ls' = 'pop3') OR '%Ls' = 'smtp')
user_query = SELECT CONCAT(homedir, maildir) AS home, CONCAT('maildir:',
homedir, maildir) AS mail, uid, gid, CONCAT('*:storage=', (quota*1024))
as quota_rule FROM mail_users WHERE (username = '%u' OR email = '%u')

-----------------------------------------------

Regards,
Tobi M.