dovecot 2.2/openssl 1.0 vs dovecot 2.3/openssl 1.1.1 ssl regression

Arkadiusz Miśkiewicz arekm at
Tue Nov 13 20:53:50 EET 2018


I'm considering dovecot migration from 2.2.36 run with openssl 1.0.2o to
dovecot 2.3.3 run with openssl 1.1.1.

Currently I have both variants running with identical configs and certs
(the only differences are due to config syntax changes in dovecot 2.3),
so for example on both I have:

ssl_ca = </etc/openssl/certs/wildcard_ca.pem
(this file contains single intermediate certificate of my CA)

ssl_cert = </etc/openssl/certs/wildcard_crt.pem
(this contains single cerificate for my * domain)

ssl_key =  # hidden, use -P to show it
(and one key)

No alt certs in use.

Chain is:
- CA trusted by clients (this certificate isn't provided by my dovecot,
it's not needed)
- wildcard_ca.pem - intermediate CA
- wildcard_crt.pem - wildcard certificate for my * domain

dovecot 2.2.36 behaviour is to provide wildcard_ca.pem and
wildcard_crt.pem to the client - that behaviour is OK. Client has full
trust chain.

dovecot 2.3.3 provides only wildcard_crt.pem certificate to the client
which is a big problem because missing wildcard_ca.pem (intermediate
certificate) breaks chain and client is not able to verify trust chain.

Testing is done with simple:

openssl s_client -connect -starttls imap -servername -showcerts

2.3.x announcements and upgrade wiki mention no such behaviour change,
so I assume it is a regression.

Now doing
cat wildcard_ca.pem >> wildcard_crt.pem
solves the problem and dovecot starts providing both certs to clients
but if that's the proper way of solving this issue then what's the point
of having ssl_ca config setting?


Arkadiusz Miśkiewicz, arekm / ( | )

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