[Dovecot] Differences between IPv4 and IPv6 authentication

[Tony Meyer]

Hi,

I have Dovecot listening on both IPv4 and IPv6, and can connect on
both interfaces, but cannot authenticate over IPv6, using exactly the
same credentials as IPv4.  I assumed that the same authentication
mechanisms would be used, regardless of the protocol being used - are
there differences somewhere?

For example:

~$ telnet server1.teststable.simplyspamfree.com 143
Trying 2a01:4f8:100:12c1:bc:28:b2:34...
Connected to server1.teststable.simplyspamfree.com.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE
STARTTLS AUTH=PLAIN] Training System v2.8.30038 ready.
0 login training XXXXXXXX
0 NO [AUTHENTICATIONFAILED] Authentication failed.
0 logout
* BYE Logging out
0 OK Logout completed.

~$ telnet -4 server1.teststable.simplyspamfree.com 143
Trying 188.40.178.56...
Connected to server1.teststable.simplyspamfree.com.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE
STARTTLS AUTH=PLAIN] Training System v2.8.30038 ready.
0 login training XXXXXXXX
0 OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE
SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS MULTIAPPEND UNSELECT
IDLE CHILDREN NAMESPACE UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE
QRESYNC ESEARCH ESORT SEARCHRES WITHIN CONTEXT=SEARCH LIST-STATUS
QUOTA] Logged in
0 logout
* BYE Logging out
0 OK Logout completed.

Any insight would be appreciated, thanks!

Cheers,
Tony

~$ dovecot -n
# 1.2.15: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-bpo.3-amd64 x86_64 Debian 5.0.6
log_path: /var/log/spamexperts/dovecot.log
log_timestamp: %Y-%m-%d %H:%M:%S
listen: *, [::]
disable_plaintext_auth: no
login_dir: /var/run/dovecot/login
login_executable: /usr/lib/dovecot/imap-login
verbose_proctitle: yes
first_valid_uid: 100
mail_privileged_group: mail
fsync_disable: yes
mbox_write_locks: fcntl dotlock
mail_executable: /home/spamexperts/post-login.sh
mail_plugins: acl quota imap_quota expire
imap_client_workarounds: delay-newmail
auth default:
  passdb:
    driver: sql
    args: /etc/dovecot/dovecot-mysql-maint.conf
  passdb:
    driver: sql
    args: /etc/dovecot/dovecot-mysql.conf
  userdb:
    driver: sql
    args: /etc/dovecot/dovecot-mysql-maint.conf
  userdb:
    driver: sql
    args: /etc/dovecot/dovecot-mysql.conf
plugin:
  quota: maildir
  acl: vfile:/etc/dovecot/dovecot-acls
  expire: Caught 30
  expire_dict: proxy::expire
dict:
  expire: mysql:/etc/dovecot/dovecot-expire-mysql.conf