[dovecot] Re: Some experiences

Timo Sirainen tss at iki.fi
Sun Jan 5 11:32:25 EET 2003

On Sun, 2003-01-05 at 06:46, Amelia A.Lewis wrote:
> Since it's a more-or-less closed server, I didn't want to use pam
> (well, I wouldn't mind, for users with shell accounts, but I can't see
> a way to mix pam and passwd-file ... is there a way to do that?).

Not really. I don't think it'd be worth the trouble.

> It turns out that digest-md5 support for clients is, well, not very
> widespread.  I expect this box to be used by various windoze clients,
> eventually, and while I'm willing to lay down the law a little, I
> can't find enough digest-md5 support to lay down that law.  So,
> regretfully, I abandoned that plan.  This kinda bothers me, since I
> think TLS/STARTTLS is absolutely the *wrong* solution for mailbox
> access (or for anything that deals with a store-and-forward
> transport).

I think Outlook supported only NTLM besides the plaintext auth. There's
specs for it now so it would be possible to be supported too.

> I therefore tried md5 passwords in a passwd-file, with STARTTLS
> enabled.  Didn't work.  I turned off SSL, and reenabled plain-text,
> and watched the login go by.  Very sniffable, of course.  But correct
> username and password ... failed.  There are instructions for creating
> digest-md5 style secrets in auth.txt, but none for md5 passwords; I
> used openssl passwd -1 [password] (and cut and paste).  It seems odd
> to me that this didn't work; does that command use a different
> algorithm than dovecot?

It uses different algorithm, although Dovecot could be made to support
that too.. The Dovecot's algorithm is very simple and is compatible with
pwdfile PAM module, it's simply the MD5 sum of a given text, eg:

perl -MDigest::MD5 -e 'print Digest::MD5::md5_hex("pass")."[34]\n"'

Digest-MD5 passwords should probably rather be used so that could be
used also by people who can. The description was a bit broken it seems,
for plaintext authentication it works only if the realm is empty, so
this should work:

perl -MDigest::MD5 -e 'print Digest::MD5::md5_hex("user::pass")."[56]\n"'

> imap(user:@omain.realm): Failed to create storage with data:
> domain.realm

Guess I should have actually tested this :) It tried to replace the ':'
char with '@'. Fixed.

> Note the missing first letter after user:@  And I don't know what it
> was trying to do; the maildirs already exist.  /etc/dovecot.conf sets
> the default mail location to /home/users/%n/Maildir (non-shell users

%n was then "user:", so it didn't work.

> The solution was to remove the realm (which isn't useful except for
> digest md5, anway, right?).

It's not really useful for digest-md5 either. It's mostly to support
multiple realms running in same server. I'm not yet sure how I'd
actually even properly support those .. probably fallback to user at realm
style in plaintext passwords.

Maybe I should consider anyway using Cyrus SASL library, at least
optionally. Would make life so much easier :) Everyone keeps wanting
LDAP and MySQL and whatever support, but I'd rather concentrate on the
IMAP side for now.

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