I just added an ECDSA certificate to my mail server using ssl_alt_cert (the RSA
certificate is specified by ssl_cert), both certificate files contain the
certificate and a single intermediate (which currently happens to be the same
intermediate from Let?s Encrypt).
When connecting to the server using either RSA or ECDSA ciphers, the server
sends the proper certificate, but also sends two intermediates. Apparently it?s
reading the intermediate from both files and using both for all situations,
rather than using only the intermediate in the RSA file for RSA certificates,
and the intermediate in the ECDSA file for ECDSA certificates. I expect this
will be a bigger problem when Let?s Encrypt starts using ECDSA intermediates.
Removing the intermediate from the ssl_alt_cert file solves the problem (but
then doesn?t allow an ECDSA intermediate to be specified).
Configuration:
# 2.2.34 (874deae): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.4.22 (22940fb7)
# OS: Linux 4.14.17-x86_64-linode99 x86_64 Debian 9.3 ext4
# Hostname: [redacted]
auth_mechanisms = plain login
listen = [ipv4 redacted], [ipv6 redacted]
mail_location = maildir:/var/mail/vhosts/%d/%n
mail_privileged_group = mail
namespace inbox {
inbox = yes
location =
mailbox Drafts {
special_use = \Drafts
}
mailbox Junk {
special_use = \Junk
}
mailbox Sent {
special_use = \Sent
}
mailbox "Sent Messages" {
special_use = \Sent
}
mailbox Trash {
special_use = \Trash
}
prefix =
}
passdb {
args = /etc/dovecot/dovecot-sql.conf.ext
driver = sql
}
passdb {
args = /etc/dovecot/dovecot-ldap.conf.ext
driver = ldap
}
protocols = imap lmtp
service auth-worker {
user = vmail
}
service auth {
unix_listener /var/spool/postfix/private/auth {
group = postfix
mode = 0666
user = postfix
}
unix_listener auth-userdb {
mode = 0600
user = vmail
}
user = dovecot
}
service imap-login {
inet_listener imap {
port = 0
}
inet_listener imaps {
port = 993
ssl = yes
}
}
service lmtp {
unix_listener /var/spool/postfix/private/dovecot-lmtp {
group = postfix
mode = 0600
user = postfix
}
}
ssl = required
ssl_alt_cert = </etc/ssl/certs/mail.[redacted].ecdsa.pem
ssl_alt_key = </etc/ssl/private/[redacted].ecdsa.key
ssl_cert = </etc/ssl/certs/mail.[redacted].rsa.pem
ssl_key = </etc/ssl/private/[redacted].rsa.key
ssl_cipher_list =
ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:DHE-RSA-AES256-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES256-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES128-SHA:DHE-RSA-AES128-SHA:kEDH+CAMELLIA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:AES:CAMELLIA:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:!PSK:!aECDH:!EDH-DSS-DES-CBC3-SHA:!EDH-RSA-DES-CBC3-SHA:!KRB5-DES-CBC3-SHA:!DES-CBC3-SHA
ssl_dh_parameters_length = 4096
ssl_prefer_server_ciphers = yes
userdb {
args = uid=vmail gid=vmail home=/var/vmail/vhosts/%d/%n
driver = static
}
userdb {
args = /etc/dovecot/dovecot-ldap.conf.ext
driver = ldap
}
On 08/03/18 18:43, Peter Linss wrote:> I just added an ECDSA certificate to my mail server using ssl_alt_cert (the RSA certificate is specified by ssl_cert), both certificate files contain the certificate and a single intermediate (which currently happens to be the same intermediate from Let?s Encrypt). > > When connecting to the server using either RSA or ECDSA ciphers, the server sends the proper certificate, but also sends two intermediates. Apparently it?s reading the intermediate from both files and using both for all situations, rather than using only the intermediate in the RSA file for RSA certificates, and the intermediate in the ECDSA file for ECDSA certificates. I expect this will be a bigger problem when Let?s Encrypt starts using ECDSA intermediates. > > Removing the intermediate from the ssl_alt_cert file solves the problem (but then doesn?t allow an ECDSA intermediate to be specified).I believe that supplying multiple unrelated intermediate certificates is an incorrect behaviour, though I don't know if this is a problem that can be solved in Dovecot or has to be addressed in openssl itself. Do you get any issue in certificate validation in the client? John
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On 10 March 2018 at 14:49 John Fawcett <
<a
href="mailto:john@voipsupport.it">john@voipsupport.it</a>>
wrote:
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On 08/03/18 18:43, Peter Linss wrote:
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I just added an ECDSA certificate to my mail server using ssl_alt_cert (the
RSA certificate is specified by ssl_cert), both certificate files contain the
certificate and a single intermediate (which currently happens to be the same
intermediate from Let’s Encrypt).
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When connecting to the server using either RSA or ECDSA ciphers, the server
sends the proper certificate, but also sends two intermediates. Apparently it’s
reading the intermediate from both files and using both for all situations,
rather than using only the intermediate in the RSA file for RSA certificates,
and the intermediate in the ECDSA file for ECDSA certificates. I expect this
will be a bigger problem when Let’s Encrypt starts using ECDSA intermediates.
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Removing the intermediate from the ssl_alt_cert file solves the problem
(but then doesn’t allow an ECDSA intermediate to be specified).
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I believe that supplying multiple unrelated intermediate certificates is
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an incorrect behaviour, though I don't know if this is a problem that
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can be solved in Dovecot or has to be addressed in openssl itself.
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Do you get any issue in certificate validation in the client?
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John
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You sure your cert file does not contain unrelated certificates?
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---
<br>Aki Tuomi
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