I changed some of the tls options following the document, now config is following:

tokeninfo_url = https://keycloak.com/auth/realms/mail/protocol/openid-connect/token
introspection_url = https://dovecot:7598e21b-ec34-481f-80d0-059bddae0923@keycloak.com/auth/realms/demo/protocol/openid-connect/token/introspect
introspection_mode = post
debug = yes
rawlog_dir = /tmp/oauth2
#force_introspection = yes
username_attribute = username
#active_attribute = active
#active_value = true
tls_ca_cert_file = /etc/pki/CA/certs/incommon-rsa-server-ca.crt
tls_cert_file = /etc/pki/dovecot/certs/dovecot.pem
tls_key_file = /etc/pki/dovecot/private/dovecot.pem

---------------

The debug log is showing now slightly different msg ex:

Dec 5 21:09:59 mktst4 dovecot: auth: Error: oauth2(mizuki,10.0.2.1,<29b4iv+YKuuCx5Tr>): oauth2 failed: Couldn't initialize SSL context: Can't load SSL certificate: There is no valid PEM certificate.

Still not able to connect to the keyclaok server. :(

PS: Dovecot & Keycloak severs are both using the same legit cert/key pair with CA file configured.

Thanks!

Mizuki

On Thu, Dec 5, 2019 at 3:06 PM Aki Tuomi < aki.tuomi@open-xchange.com> wrote:

Before declaring it not ready for prime time, did you try setting

tls_ca_cert_file = /etc/ssl/certs/ca-certificates.crt

In the oauth2 configuration file as documented in https://doc.dovecot.org/configuration_manual/authentication/oauth2 ?

Aki

> On 05/12/2019 21:58 mizuki via dovecot < dovecot@dovecot.org> wrote:
>
>
> Hi all,
>
> We'd like to enable OAuth with Keycloak in Dovecot, after enabling 'OAUTHBEARER XOAUTH2' in Dovecot based on online document, I can confirm Dovecot is ready for OAuth using openssl command, however when the auth request comes in, it failed in establishing a SSL connection with Keycloak server on port 443, shown as following in debug logs. I can confirming using commands 'openssl s_client -connect <keycloak_server>:443' or 'curl -v https://<keycloak_server/' all returns normal and no errors. Altering some of the SSL options in dovecot such as 'ssl_ca = </etc/pki/CA/certs/root_ca.pem' or 'ssl_client_ca_file = </etc/pki/CA/certs/root_ca.pem' does not help either. The certificate are NOT self-signed but signed the legit authorities. So I'm not sure why dovecot could not establish the connections.
>