Now I’ve got my production server running Dovecot (finally) and can tell you that it really rocks and I performed the upgrade without any problem. Just configure, compile and install as per instructions and then kill the current running dovecot process. The new version should start automatically.

Just an small remark, just saw in my Wordpress dashboard before posting this, that I’ve passed the 200 blogposts on this blog. That is excluding the 134 pages (the actual documentation) and the 920 comments (which I tend to prune every now and then to keep them relevant).

Read on for more information on step 2 for the migration.

I already ran into some problems that I haven’t seen one any of my test runs, which shows that it was good to do this upgrade myself for real before posting the full writeup. I’m posting the migration in several independent steps which you can do at your own leisure and speed. After each step you will have a fully functioning mailserver where only a small part of the setup has been changed. In this manner everything should be manageable and hopefully will not pose to many issues.

In the first step we are going to replace the Courier IMAP server with the Dovecot IMAP server. The instructions will work for Leopard and Snow Leopard. The next step will be about replacing Courier Auth with the Dovecot Auth module.

But no time to waste, read the first step in migrating from Courier to Dovecot.

• deliver: Don’t crash when a message with Auto-submitted: header gets rejected.
• lib-storage: Fixed header searches to work correctly when there are multiple headers with same name.
• dict client: Disconnect from dict server after 1 second of idling.
• dict: If process crashed, it wasn’t automatically restarted
• dict file: If dict file’s group permissions equal world permissions, don’t try to change its gid.
• maildir: Fixed a memory leak when copying with hardlinks.
• maildir: Expunging last messages may have assert-crashed if their filenames had just changed.

• mbox: Message header reading was unnecessarily slow. Fetching a huge header could have resulted in Dovecot eating a lot of CPU. Also searching messages was much slower than necessary.
• mbox, dbox, cydir: Mail root directory was created with 0770 permissions, instead of 0700.
• maildir: Reading uidlist could have ended up in an infinite loop.
• IMAP IDLE: v1.2.7+ caused extra load by checking changes every 0.5 seconds after a change had occurred in mailbox

• %variables now support %{host}, %{pid} and %{env:ENVIRONMENT_NAME} everywhere.
• LIST-STATUS capability is now advertised
• maildir: Fixed several assert-crashes.
• imap: LIST “” inbox shouldn’t crash when using namespace with “INBOX.” prefix.
• lazy_expunge now ignores non-private namespaces.

• maildir: When saving, filenames now always contain ,S=. Previously this was done only when quota plugin was loaded. It’s required for zlib plugin and may be useful for other things too.
• lazy-expunge: Support a single-namespace configuration. If a mailbox is deleted, its messages are merged with its old expunged messages (if there were any).
• expire: Settings now support spaces in mailbox names by using quoted strings.
• maildir: v1.2.7 and v1.2.8 caused assert-crashes in maildir_uidlist_records_drop_expunges()
• maildir_copy_preserve_filename=yes could have caused crashes.
• Maildir++ quota: % limits weren’t updated when limits were read from maildirsize.
• virtual: v1.2.8 didn’t fully fix the “lots of mailboxes” bug
• virtual: Fixed updating virtual mailbox based on flag changes.
• fts-squat: Fixed searching multi-byte characters.

This is mainly to fix the 0777 base_dir creation issue, which could be considered a security hole, exploitable by local users. An attacker could for example replace Dovecot’s auth socket and log in as other users. Gaining root privileges isn’t possible though.

This affects only v1.2 users, v1.1 and older versions were creating the directory with 0755 permission.

If your Dovecot’s base_dir isn’t in /var/run/dovecot/, you should also make sure that the $prefix/var/ and $prefix/var/run/ (i.e. /usr/local/var/, /usr/local/var/run/ by default) aren’t 0777.

The fixes include:

• Dovecot v1.2.x had been creating base_dir (and its parents if necessary) with 0777 permissions. The base_dir’s permissions get changed to 0755 automatically at startup, but you may need to chmod the parent directories manually.
• acl: If user has rights from more than one group, merge them instead of choosing one group’s rights and ignoring others.
• virtual: When using a lot of mailboxes, the virtual mailbox’s header could have grown over 32 kB and caused “out of memory” crashes. Also over 64 kB headers couldn’t even be updated with existing transaction log records. Added a new record type that gets used with >=64 kB headers. Older Dovecot versions don’t understand this header and will log errors if they see it.
• FETCH BODYSTRUCTURE didn’t return RFC 2231 “key*” fields correctly

There is mention of moving o a 2.0 version in a few weeks. I hope to have that ready and tested as soon as possible.

Here is a list of the changes:

• Upgraded to Unicode 5.2.0
• Added authtest utility for doing passdb and userdb lookups.
• login: ssl_security string now also shows the used compression.
• quota: Don’t crash with non-Maildir++ quota backend.
• imap proxy: Fixed crashing with some specific password characters.
• dovecot –exec-mail was broken.
• Avoid assert-crashing when two processes try to create index at the same time.

Update: There is a small issue when compiling this version on Leopard. It’s has to do with the fact that Leopard is using an older version (0.7.8) of OpenSSL than Snow Leopard (using 0.9.8).

The error will show itself during the make fase of the build. You would see errors like:

Undefined symbols:
“_SSL_get_current_compression”, referenced from:
_ssl_proxy_get_security_string in liblogin-common.a(ssl-proxy-openssl.o)
“_SSL_COMP_get_name”, referenced from:
_ssl_proxy_get_security_string in liblogin-common.a(ssl-proxy-openssl.o)
ld: symbol(s) not found

You can solve it by downloading and applying this fix, execute the following commands from the 1.2.6 source directory:

curl "http://hg.dovecot.org/dovecot-1.2/raw-file/4add5c3f13ea/configure.in" \
-o ./configure.in
 
curl "http://hg.dovecot.org/dovecot-1.2/raw-file/4add5c3f13ea/src/login-common/ssl-proxy-openssl.c" \
-o ./src/login-common/ssl-proxy-openssl.c

Then run the normal ./configure and make statements from the regular install instructions.

The bugfixes include:

• Authentication: DIGEST-MD5 and RPA mechanisms no longer require user’s login realm to be listed in auth_realms. It only made configuration more difficult without really providing extra security.
• zlib plugin: Don’t allow clients to save compressed data directly. This prevents users from exploiting (most of the) potential security holes in zlib/bzlib.
• Added pop3_save_uidl setting.
• dict quota: When updating quota and user isn’t already in dict, recalculate and save the quota.
• file_set_size() was broken with OSes that didn’t support posix_fallocate() (almost everyone except Linux), causing all kinds of index file errors.
• v1.2.4 index file handling could have caused an assert-crash
• IMAP: Fixes to QRESYNC extension.
• virtual plugin: Crashfix
• deliver: Don’t send rejects to any messages that have Auto-Submitted
  header. This avoids emails loops.
• Maildir: Performance fixes, especially with maildir_very_dirty_syncs.
• Maildir++ quota: Limits weren’t read early enough from maildirsize file (when quota limits not enforced by Dovecot)
• Message decoding fixes (mainly for IMAP SEARCH, Sieve).