imap-login SSLv3 causes signal 11, core dump and DoS. ssl_protocols = ??

[James]

Connecting to dovecot with ssl3 causes imap-login to die:


$ openssl s_client -connect localhost:993 -ssl3
CONNECTED(00000003)
4277630796:error:14094410:SSL routines:ssl3_read_bytes:sslv3 alert 
handshake failure:s3_pkt.c:1461:SSL alert number 40
4277630796:error:1409E0E5:SSL routines:ssl3_write_bytes:ssl handshake 
failure:s3_pkt.c:645:
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 7 bytes and written 0 bytes
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
     Protocol  : SSLv3
     Cipher    : 0000
     Session-ID:
     Session-ID-ctx:
     Master-Key:
     Key-Arg   : None
     PSK identity: None
     PSK identity hint: None
     SRP username: None
     Start Time: 1426851034
     Timeout   : 7200 (sec)
     Verify return code: 0 (ok)
---



syslog:
Mar 20 11:30:35 MAILHOST dovecot: [ID 583609 mail.crit] imap-login: 
Fatal: master: service(imap-login): child 21918 killed with signal 11 
(core dumped) [last ip=127.0.0.1]




dovecot.conf had:
ssl_protocols = !SSLv2 !SSLv3

removing that line stops the core dump and syslog then shows:

Mar 20 11:36:25 MAILHOST dovecot: [ID 583609 mail.info] imap-login: 
Disconnected (disconnected before auth was ready, waited 0 secs): 
user=<>, rip=127.0.0.1, lip=127.0.0.1, TLS handshaking: SSL_accept() 
failed: error:14076102:SSL routines:SSL23_GET_CLIENT_HELLO:unsupported 
protocol, session=<eqr1ubYRWgB/AAAB>



the "SSL23_GET_CLIENT_HELLO:unsupported protocol" seems to do what I 
thought the ssl_protocols setting did.
Do I still need, if I ever needed, the "ssl_protocols = " setting?



James.



# dovecot -n
# 2.2.16: /etc/opt/XXXX/dovecot/dovecot.conf
# Pigeonhole version 0.4.7
# OS: SunOS 5.10 i86pc
auth_mechanisms = plain login digest-md5 cram-md5
base_dir = /var/opt/XXXX/dovecot/
lda_mailbox_autocreate = yes
lda_mailbox_autosubscribe = yes
login_trusted_networks = 111.222.333.444/24
mail_gid = vmail
mail_home = /XXXXXX/XXXX/%d/%n
mail_location = maildir:/XXXXX/XXXX/%d/%n/Maildir
mail_max_userip_connections = 20
mail_plugins = quota
mail_uid = vmail
mailbox_idle_check_interval = 10 secs
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope 
encoded-character vacation subaddress comparator-i;ascii-numeric 
relational regex imap4flags copy include variables body enotify 
environment mailbox date index ihave duplicate
passdb {
   args = /etc/opt/XXXX/dovecot/dovecot-sql.conf
   driver = sql
}
plugin {
   fts_autoindex = yes
   quota = maildir:User quota
   quota_rule = *:storage=1G
   quota_rule2 = Trash:storage=+10%
   quota_warning = storage=90%% quota-warning 90 %u
   quota_warning2 = storage=95%% quota-warning 95 %u
   quota_warning3 = storage=99%% quota-warning 99 %u
   sieve = /XXXXX/XXXX/%d/%n/dovecot.sieve
   sieve_dir = /XXXXX/XXXX/%d/%n/sieve
}
protocols = imap lmtp sieve
service auth {
   drop_priv_before_exec = yes
   unix_listener auth-client {
     mode = 0660
   }
   unix_listener auth-master {
     mode = 0600
   }
   user = root
}
service imap-login {
   chroot =
   drop_priv_before_exec = yes
   executable = imap-login -D
   service_count = 1
   user = dovecot
}
service lmtp {
   group = vmail
   unix_listener lmtp {
     mode = 0666
   }
   user = vmail
}
service quota-warning {
   executable = script /etc/opt/XXXX/dovecot/quota-warning
   user = vmail
}
ssl_cert = </etc/opt/XXXX/dovecot/dovecot.pem
ssl_cipher_list = AES128+EECDH:AES128+EDH
ssl_key = </etc/opt/XXXX/dovecot/dovecot.pem
ssl_prefer_server_ciphers = yes
ssl_protocols = !SSLv2 !SSLv3
userdb {
   driver = prefetch
}
userdb {
   args = /etc/opt/XXXX/dovecot/dovecot-sql.conf
   driver = sql
}
protocol lda {
   auth_socket_path = /var/opt/XXXX/dovecot/auth-master
   mail_plugins = quota sieve
   postmaster_address = postmaster at XXXXXXXX
   sendmail_path = /opt/XXXX/sbin/exim
}
protocol pop3 {
   mail_plugins = quota
}
protocol imap {
   mail_plugins = quota imap_quota
}
protocol lmtp {
   mail_plugins = quota sieve
   postmaster_address = postmaster at XXXXXX
   sendmail_path = /opt/XXXX/sbin/exim
}