[Dovecot] dovecot and vmailmgr

hello

now that dovecot supports authentication with checkpassword-compatible modules, I tried to get it working for IMAP on a qmail + vmailmgr
server.

For a subtle detail, while claiming to be "a drop-in replacement for
the standard checkpassword", checkvpw (auth module for vmailmgr) is not "drop in".
It actually expects 2 args on its command line, not 1. So, a wrapper is needed to
get it authenticating correctly with dovecot; a very simple one
(argswrapper.c below).

This wrapper is not sufficient though. In fact, vmailmgr represents
user homes like this: $HOME_LOCUSER/users/virtual_username this is ok with default_mail_env = maildir:%h/users/%n

$HOME_LOCUSER depends on the domain part of the user's email. The
relation is held in /var/qmail/control/virtualdomains . However, on the local part (virtual_username) some rewriting is done
on the username, as dots are replaced by ":". So in the end j.doe@foo.com becomes "~mxfoocom/users/j:doe".

Now, var-expand does not support any rewriting. I patched it by
adding another modifier, m_str_replace(), which replaces REPLACE_SOURCE with
REPLACE_TARGET in a given string. By defining REPLACE_SOURCE to '.' and
REPLACE_TARGET to ':' one accomplishes the vmailmgr username rewriting. This modifier is
applied with "P", so: default_mail_env = maildir:%h/users/%Pn

A better, general solution would be for dovecot to implement some
kind of general rewriting, say with regexps and sed-like replacement rules, or with
an external process in a cgi fashion.

With this patch, dovecot gets the correct path for any user mailbox.
However, there's a bug in dovecot storage modules (both maildir and mbox) which truncates
the path in the first ":", when expecting ":INBOX" etc specifiers:

     /* <Maildir> [:INBOX=<dir>] [:INDEX=<dir>] [:CONTROL=<dir>] */
     if (debug)
         i_info("maildir: data=%s", data);
     p = strchr(data, ':');
     if (p == NULL)
         root_dir = data;
     else {
         root_dir = t_strdup_until(data, p);

this way, a former data = /var/maildirs/foo/users/j:doe:INDEX=... is
truncated to /var/maildirs/foo/users/j . This opens the much worse possibility for
user "j:doe" to be accounted into user "j" account after authentication.

It is difficult to get a solid fix here, because the grammar is
ambiguous for INBOX, INDEX and CONTROL tokens. Since they are not separated with an
illegal path symbol from the rest of the path in default_mail_env, it is not
possible to state when a ":INBOX=" token belongs to the path and when it is a user
directive. The Best is to move the specifiers into a different configuration directive. However, a more solid check with the current modus operandi is

     /* <Maildir> [:INBOX=<dir>] [:INDEX=<dir>] [:CONTROL=<dir>] */
     if (debug)
         i_info("maildir: data=%s", data);
     /* extracting INBOX / INDEX / CONTROL suffices */
     if (((p = strstr(data, ":INBOX=")) != NULL)
         || ((p = strstr(data, ":INDEX=")) != NULL)
         || ((p = strstr(data, ":CONTROL=")) != NULL)) {

         root_dir = t_strdup_until(data, p);

which expects the full ":INBOX=" etc strings to be present in data
instead of the single ":" separator. The patches that implement this for both {maildir,mailbox}-storage
are also appended below.

I will take a couple of hours tomorrow to wrap all the iter up on a
web page here http://mij.oltrelinux.com/net/dovecot-qmail-vmailmgr/

All the patches are applied wrt 1.0-beta7

bye