Enabling weak RSA ciphers in RabbitMQ not working

[Dan Thorson]

Hello,

I need to enable weak RSA-PSK support in RabbitMQ - we have older IoT devices that don't support the latest ciphers, which need to connect to RabbitMQ (via the MQTT Plugin).  Setting the ssl_options.ciphers.X in rabbitmq.conf is not working.  TLS/SSL is working fine with the available cipher_suites.

I have confirmed that the ciphers are available to RabbitMQ, but not enabled:

# diff <(rabbitmq-diagnostics cipher_suites --format openssl -q) <(rabbitmq-diagnostics cipher_suites --format openssl -q --all)|grep RSA-PSK
> RSA-PSK-AES256-GCM-SHA384
> RSA-PSK-AES256-CBC-SHA384
> RSA-PSK-AES128-GCM-SHA256
> RSA-PSK-AES128-CBC-SHA256
> RSA-PSK-AES256-CBC-SHA
> RSA-PSK-AES128-CBC-SHA
> RSA-PSK-RC4-SHA

Erlang also reports the ciphers as available:

> rp(ssl:cipher_suites(all,'tlsv1.2','openssl')).
["ECDHE-ECDSA-AES256-GCM-SHA384",
 "ECDHE-RSA-AES256-GCM-SHA384","ECDHE-ECDSA-AES256-CCM",
 "ECDHE-ECDSA-AES256-CCM8","ECDHE-ECDSA-AES256-SHA384",
 "ECDHE-RSA-AES256-SHA384","ECDHE-ECDSA-CHACHA20-POLY1305",
 "ECDHE-RSA-CHACHA20-POLY1305",
 "ECDHE-ECDSA-AES128-GCM-SHA256",
 "ECDHE-RSA-AES128-GCM-SHA256","ECDHE-ECDSA-AES128-CCM",
 "ECDHE-ECDSA-AES128-CCM8","ECDH-ECDSA-AES256-GCM-SHA384",
 "ECDH-RSA-AES256-GCM-SHA384","ECDH-ECDSA-AES256-SHA384",
 "ECDH-RSA-AES256-SHA384","ECDH-ECDSA-AES128-GCM-SHA256",
 "ECDH-RSA-AES128-GCM-SHA256","ECDHE-ECDSA-AES128-SHA256",
 "ECDHE-RSA-AES128-SHA256","ECDH-ECDSA-AES128-SHA256",
 "ECDH-RSA-AES128-SHA256","DHE-RSA-AES256-GCM-SHA384",
 "DHE-DSS-AES256-GCM-SHA384","DHE-RSA-AES256-SHA256",
 "DHE-DSS-AES256-SHA256","DHE-RSA-AES128-GCM-SHA256",
 "DHE-DSS-AES128-GCM-SHA256","DHE-RSA-CHACHA20-POLY1305",
 "DHE-RSA-AES128-SHA256","DHE-DSS-AES128-SHA256",
 "ECDHE-ECDSA-AES256-SHA","ECDHE-RSA-AES256-SHA",
 "ECDH-ECDSA-AES256-SHA","ECDH-RSA-AES256-SHA",
 "ECDHE-ECDSA-AES128-SHA","ECDHE-RSA-AES128-SHA",
 "ECDH-ECDSA-AES128-SHA","ECDH-RSA-AES128-SHA",
 "DHE-RSA-AES256-SHA","DHE-DSS-AES256-SHA",
 "DHE-RSA-AES128-SHA","DHE-DSS-AES128-SHA",
 "RSA-PSK-AES256-GCM-SHA384","RSA-PSK-AES256-CBC-SHA384",
 "RSA-PSK-AES128-GCM-SHA256","RSA-PSK-AES128-CBC-SHA256",
 "RSA-PSK-AES256-CBC-SHA","RSA-PSK-AES128-CBC-SHA",
 "RSA-PSK-RC4-SHA","SRP-RSA-AES-256-CBC-SHA",
 "SRP-DSS-AES256-CBC-SHA","SRP-RSA-AES-128-CBC-SHA",
 "SRP-DSS-AES128-CBC-SHA","AES256-GCM-SHA384",
 "AES256-SHA256","AES128-GCM-SHA256","AES128-SHA256",
 "AES256-SHA","AES128-SHA","DES-CBC3-SHA",
 "ECDHE-ECDSA-DES-CBC3-SHA","ECDHE-RSA-DES-CBC3-SHA",
 "EDH-RSA-DES-CBC3-SHA","DHE-DSS-DES-CBC3-SHA",
 "ECDH-ECDSA-DES-CBC3-SHA","ECDH-RSA-DES-CBC3-SHA",
 "EDH-RSA-DES-CBC-SHA","DES-CBC-SHA","ECDHE-ECDSA-RC4-SHA",
 "ECDHE-RSA-RC4-SHA","ECDH-ECDSA-RC4-SHA","ECDH-RSA-RC4-SHA",
 "RC4-SHA","RC4-MD5"]


I have tried to set the ciphers in rabbitmq.conf, but that is not working - the ciphers are not enabled when RabbitMQ is restarted - RabbitMQ reports (via the diagnostics/cipher_suites tool) the same list of cipher_suites regardless of the config file.   I have confirmed the config file is being used, and can see other changes made in it take effect when restarting RabbitMQ. I have the log levels set to debug but can't see anything related to SSL, TLS, or ciphers in the logs.

Here are my ssl_options settings.  The certificates and key were created using the tls_gen utility.

# grep ssl_options /etc/rabbitmq/rabbitmq.conf

ssl_options.cacertfile = /etc/pki/tls/ca_certificate.pem
ssl_options.certfile = /etc/pki/tls/server_certificate.pem
ssl_options.keyfile = /etc/pki/tls/server_key.pem
ssl_options.password = XXXXXXXXXX

ssl_options.verify = verify_peer
ssl_options.fail_if_no_peer_cert = false
ssl_options.versions.1 = tlsv1.2
ssl_options.ciphers.1  = RSA-PSK-AES256-GCM-SHA384
ssl_options.ciphers.2  = RSA-PSK-AES128-GCM-SHA256
ssl_options.ciphers.3  = RSA-PSK-AES128-CBC-SHA256
ssl_options.ciphers.4  = RSA-PSK-AES256-CBC-SHA
ssl_options.ciphers.5  = RSA-PSK-AES128-CBC-SHA
ssl_options.ciphers.6  = RSA-PSK-RC4-SHA
ssl_options.honor_cipher_order = true
ssl_options.honor_ecc_order    = true

RabbitMQ version is 3.12.2
Erlang version is 25.3.2
OpenSSL version is 1.0.2

Has anyone here been able to enable weak RSA cipher support in RabbitMQ?

[Luke Bakken]

Hi Dan,

Thanks for the comprehensive report.

In situations like this, it's preferable for you to attach your full, unabridged configuration files to your messages rather than copy/paste. I've seen enough subtle errors in config files to not trust copy/paste.

Even better would be to save everything in a publicly-available source code repo (via GitHub / GitLab, for one example) that I can clone and use.

Feel free to obfuscate sensitive values, of course.

I can generate my own certs using tls-gen.

Can you give exact steps for how I can test whether the expected ciphers are available? Can I use https://testssl.sh/?

Thanks,

Luke