Mailer TLS-configuration, possible SSL-Hanshake-Exception since Quarkus 3.12

[wernert75]

Describe the bug

Given a Mail-Server uses STARTTLS, no TLS

the following configuration worked until Quarkus 3.11.x. Since 3.12.x this configuration leads to a SSL-Handshake-Exception.

quarkus.mailer.from=a@b.com
quarkus.mailer.host=localhost
quarkus.mailer.port=25
qauarkus.mailer.mock=false
quarkus.tls.trust-all=true

Switch quarkus.tls.trust-all to false, or remove the property, make the configuration works.

It seems, only the trust-all=true configuration property enables TLS. Even if it's not configured.

Expected behavior

Mails should be send without throwing an exception, even if trust-all=true

Actual behavior

Mailer throws SSL-Handshake-Exception

How to Reproduce?

See description.

Output of uname -a or ver

No response

Output of java -version

No response

Quarkus version or git rev

No response

Build tool (ie. output of mvnw --version or gradlew --version)

No response

Additional information

No response

[quarkus-bot]

/cc @cescoffier (mailer), @radcortez (config)

[cescoffier]

@geoand I remembered we discussed something similar, but I cannot remember where.

In the case of the mailer, because of the STARTTLS mode (which starts a plain connection and upgrades it to TLS), trust-all must not be considered as an enabler for TLS. So, for the mailer, we must only enable TLS if tls-configuration-name is set or if ssl=true is set.

[geoand]

I vaguely remember something similar, but can't remember exactly...

Maybe it was for OTel?

[cescoffier]

Actually.....
The documentation looks up to date:
https://quarkus.io/guides/mailer-reference#configuring-starttls

@wernert75 can you try with:

quarkus.mailer.from=[a@b.com](mailto:a@b.com)
quarkus.mailer.host=localhost
quarkus.mailer.port=25
qauarkus.mailer.mock=false
quarkus.tls.trust-all=true

quarkus.mailer.tls=false
quarkus.mailer.start-tls=REQUIRED

To avoid the ambiguity, we explicitly disable TLS if START_TLS is used.

[geoand]

Ah no, it was for Redis

[cescoffier]

@wernert75 When you have time, can you confirm, I will document the breaking change.

[wernert75]

This configuration works:

quarkus.mailer.from=a@b.com
quarkus.mailer.host=localhost
quarkus.mailer.port=25
qauarkus.mailer.mock=false
quarkus.tls.trust-all=true

quarkus.mailer.tls=false
quarkus.mailer.start-tls=REQUIRED

BUT this configuration works not (SSLHandshakeException):
(without quarkus.mailer.tls=false)

quarkus.mailer.from=a@b.com
quarkus.mailer.host=localhost
quarkus.mailer.port=25
qauarkus.mailer.mock=false
quarkus.tls.trust-all=true

quarkus.mailer.start-tls=REQUIRED

In the end, it is primarily a configuration issue. With 3.11 it worked with the not quite consistent configuration. With 3.12 it then failed unexpectedly. A note in the documentation or in the log output would certainly be sufficient

[cescoffier]

Thanks for your reactivity, @wernert75!

Totally agree! I will update the documentation and add it to the list of breaking changes.