[Dovecot] Dovecot not handling r/o mailboxes completely, and problem with ACL as a workaround

[Adam McDougall]

I have an update, I realize now that my ACL is working, however applying the 
ACL still does nothing to improve the original problem that dovecot doesn't seem
to communicate permission failures to the client, which allows the client to 
become out of sync with reality on the server.  

I'm really not sure how dovecot might currently determine if a folder is 
read only on disk, because there seems to be some handling for that case
in the code.  Perhaps if I knew what part of the code (or an explanation)
of why it thinks a folder is not writable, I could use that to my advantage
and try to make folders look more "read only" on disk.  

On Sun, May 06, 2007 at 09:34:28PM -0400, Adam McDougall wrote:

  First of all, I think dovecot is really fantastic and I have thanks for all
  the hard work.  I think it will be the best fit for my ~5000 users when I 
  have it setup completely.  We normally have approx 500 concurrent IMAP
  connections during the day.  
  
  I am trying to convert from courier-imap to dovecot, but I have an issue with
  public namespace folders that are not writable by certain users.  Please let me
  know if I need to provide more information or how I can help solve this issue.
  

<snip>
  I don't know how courier stores and checks mail directory 
  permissions, but it was aware when a user would not be able to delete or change 
  messages and would return a READ-ONLY imap error when an attempt to change a 
  message occurred (courier returns this in the IMAP response to update mail flags 
  to reflect that the client wants to move to delete a mail).  I understand that 
  imap clients will usually only set status as read or deleted first and only try 
  to delete an email for real on expunge, but it seems dovecot does not try to 
  detect if a message is modifyable before it is too late for the user to find 
  out.  What happens is a user appears to be able to mark messages read, move them 
  to another folder, or delete them (another way of moving to another folder eg. 
  Trash).  The user is clueless that the changes will not occur, and only finds 
  out later when they reload the folder to find the messages back, or tries to 
  expunge and get an unhelpful 'internal error' from dovecot (I can help trace 
  this situation if it helps, but I think that stage should not be reached if 
  things were working right).  My configuration has the public folder control and 
  indexes inside a user's home directory, so it will always be possible for 
  dovecot to record message status changes, however I do not think dovecot should 
  update the control and indexes to reflect an IMAP operation that is not allowed 
  to complete due to restricted permissions on the actual email file.  I suppose 
  dovecot would have to check the permissions on mail message files.
  
<snip portion about ACLs>
  
  # dovecot --version
  1.0.0
  
  The reason I have so many public spaces below, is to match the existing
  directory structure we setup for courier, and also to help us keep the
  directory listing more tidy since otherwise we would end up with many folders
  all under one directory.  Some of them have monthly rotation and it could get
  out of hand if we did not split them up.  I understand it makes things more 
  difficult for the global acl list at present, if I were to use it, but 
  I may not have any conflicting folder names at this time. 
  
  # dovecot -n
  # /usr/local/etc/dovecot.conf
  ssl_cert_file: /usr/local/etc/apache2/ssl/mail.egr.msu.edu.pem
  ssl_key_file: /usr/local/etc/apache2/ssl/mail.egr.msu.edu.pem
  login_dir: /var/run/dovecot/login
  login_executable: /usr/local/libexec/dovecot/imap-login
  verbose_proctitle: yes
  first_valid_uid: 1000
  first_valid_gid: 0
  mail_location: 
  maildir:~/Maildir:CONTROL=%h/Maildir/dovecot/private/control:INDEX=%h/Maildir/dovecot/private/indexes
  mail_debug: yes
  mmap_disable: yes
  maildir_copy_with_hardlinks: yes
  mail_plugins: acl
  mail_log_max_lines_per_sec: 0
  imap_client_workarounds: delay-newmail outlook-idle netscape-eoh tb-extra-mailbox-sep
  namespace:
    type: public
    separator: /
    prefix: #shared/be/
    location: 
  maildir:/egr/mail/shared-dovecot2/be:CONTROL=%h/Maildir/dovecot/public/control/be:INDEX=%h/Maildir/dovecot/public/indexes/be
  namespace:
    type: public
    separator: /
    prefix: #shared/cee/
    location: 
  maildir:/egr/mail/shared-dovecot2/cee:CONTROL=%h/Maildir/dovecot/public/control/cee:INDEX=%h/Maildir/dovecot/public/indexes/cee
  namespace:
    type: public
    separator: /
    prefix: #shared/chems/
    location: 
  maildir:/egr/mail/shared-dovecot2/chems:CONTROL=%h/Maildir/dovecot/public/control/chems:INDEX=%h/Maildir/dovecot/public/indexes/chems
  namespace:
    type: public
    separator: /
    prefix: #shared/decs/
    location: 
  maildir:/egr/mail/shared-dovecot2/decs:CONTROL=%h/Maildir/dovecot/public/control/decs:INDEX=%h/Maildir/dovecot/public/indexes/decs
  namespace:
    type: public
    separator: /
    prefix: #shared/egr/
    location: 
  maildir:/egr/mail/shared-dovecot2/egr:CONTROL=%h/Maildir/dovecot/public/control/egr:INDEX=%h/Maildir/dovecot/public/indexes/egr
  namespace:
    type: public
    separator: /
    prefix: #shared/me/
    location: 
  maildir:/egr/mail/shared-dovecot2/me:CONTROL=%h/Maildir/dovecot/public/control/me:INDEX=%h/Maildir/dovecot/public/indexes/me
  namespace:
    type: public
    separator: /
    prefix: #shared/org/
    location: 
  maildir:/egr/mail/shared-dovecot2/org:CONTROL=%h/Maildir/dovecot/public/control/org:INDEX=%h/Maildir/dovecot/public/indexes/org
  namespace:
    type: public
    separator: /
    prefix: #shared/toptest/
    location: 
  maildir:/egr/mail/shared-dovecot2/toptest:CONTROL=%h/Maildir/dovecot/public/control/toptest:INDEX=%h/Maildir/dovecot/public/indexes/toptest
  namespace:
    type: public
    separator: /
    prefix: #shared/ugs/
    location: 
  maildir:/egr/mail/shared-dovecot2/ugs:CONTROL=%h/Maildir/dovecot/public/control/ugs:INDEX=%h/Maildir/dovecot/public/indexes/ugs
  namespace:
    type: public
    separator: /
    prefix: #shared/vprgs/
    location: 
  maildir:/egr/mail/shared-dovecot2/vprgs:CONTROL=%h/Maildir/dovecot/public/control/vprgs:INDEX=%h/Maildir/dovecot/public/indexes/vprgs
  namespace:
    type: private
    separator: /
    prefix: mail/
    hidden: yes
  namespace:
    type: private
    separator: /
    location: 
  maildir:~/Maildir:CONTROL=%h/Maildir/dovecot/private/control:INDEX=%h/Maildir/dovecot/private/indexes
    inbox: yes
  auth default:
    mechanisms: plain login
    passdb:
      driver: pam
    userdb:
      driver: passwd
    socket:
      type: listen
      client:
        path: /var/spool/postfix/private/auth
        user: postfix
        group: postfix
      master:
  plugin:
    acl: vfile:/usr/local/etc/dovecot-acls
  
  Thanks.